SENSOR TO DETECT THE LEVEL OF A MEDIA CONTAINED IN A CONTAINER, METHOD TO CONTROL A SENSOR TO DETECT

专利摘要:
a sensor for detecting the level of a medium contained in a container, in particular a tank, comprising: an arrangement of capacitive elements designed to be associated with the container (1), in particular, so as to extend according to a geometric axis of detection (x) of the middle level (l), the arrangement of capacitive elements comprising a plurality of electrodes (j1 to jn), in particular, on one side of an electrically insulating substrate (20) having a generally elongated shape, the electrodes (j1 to jn) are separated from each other, in particular, along the geometric axis of detection (x) and are preferably substantially coplanar with each other; at least one insulating layer (16) for electrically insulating the electrodes (j1 to jn) in relation to the interior of the container (1); and a controller (24) having a plurality of inputs; each capacitive element comprises at least one of a single electrode and a set of electrodes connected together in common, in particular in parallel, the single electrode or the set of electrodes being connected to a respective input among the plurality of inputs; the controller (24) is predisposed to discriminate a capacitance value associated with each electrode (j1 to jn) in order to deduce the level of the medium present in the container.
公开号:BR112017005012B1
申请号:R112017005012-9
申请日:2015-09-14
公开日:2021-03-30
发明作者:Matteo Rondano；Enrico Chiesa；Mauro Zorzetto；Domenico Cantarelli
申请人:Eltek S.P.A.；
IPC主号:

专利说明:

FIELD OF THE INVENTION
[0001] The present invention relates to a sensor to detect the level of a generic medium, such as a liquid, a fluid substance, a powdery material or a material in the bulk state, etc. The invention was developed with particular reference to level sensors of a capacitive type used in vehicles. PREVIOUS TECHNIQUE
[0002] Level sensors are used in various contexts to detect a residual amount of a liquid present in a generic container, such as a tank. Some of these sensors are based on the use of a float. These sensors are generally mechanically complicated and have some critical aspects, such as risks of obstruction. These are inevitably affected by problems related to the possible freezing of the medium that is subjected to measurement.
[0003] Level sensors based on the measurement of electrical quantities are also known, such as conductivity / resistivity or capacitance. These sensors often have an array of first electrodes, arranged according to the geometry axis of level detection, which is usually vertical on a corresponding insulating substrate that must be installed inside the tank. The sensors then have a similar arrangement of second electrodes defined between those of the first array or facing the same so that the fluid whose level is to be measured penetrates between the electrodes of the two arrays. In some solutions, instead of a plurality of second electrodes, a common electrode is provided that has a height at least equal to that of the first array. In still other solutions, it is the tank itself that has an internal surface made electrically conductive, for example, by means of a metallization surface in order to function as a common electrode. The electrodes are electrically connected to a circuit arrangement, which often includes a microcontroller that, processing the value of the electrical quantity detected by the electrodes, can identify a transition area between the liquid and the air in the tank, which is considered indicative of the liquid level.
[0004] In these known solutions, the electrodes are in direct contact with the liquid, therefore, they are subjected to premature aging and wear. The operation of these sensor systems is then strictly related to the characteristics of the fluid, such as the conductivity / resistivity or the dielectric constant of the same.
[0005] With reference to level sensors of a capacitive type, these typically contemplate at least two electrodes facing each other, among which the liquid whose level must be detected must penetrate, in which the electrodes that are excited by means of an oscillator circuit, that is, a circuit that generates an electrical frequency-modulated or AC signal. The circuit detects a variation of the capacitance between the electrodes facing each other that is proportional to the variation of the dielectric defined between the electrodes, that is, proportional to the level of the liquid defined between them and, therefore, of the capacitance of the sensor element. In these sensors, an input signal is then obtained proportional to the aforementioned capacitance variation. Known sensors of this type include configurations with a respective impedance that can even behave as antennas and present the problem of generating electromagnetic interference (EMI), in which this disturbance interferes with other electronic systems, such as electronic circuits on board the vehicle. . This phenomenon increases with the increase in the length of the electrodes, that is, with the increase in the length of the level sensor that can behave like a transmission antenna.
[0006] The additional types of capacitive sensors contemplate the execution of measurement between at least two coplanar electrodes, for example, in a finger-corrected configuration (interdigitated), which face an insulating wall that separates them from the liquid, in which the presence of liquid beyond the insulating wall determines a variation in the dielectric between the two electrodes defined next to each other, thus enabling detection. Such a sensor is known, for example, from US 7258005 B2. In such cases, the spacing between the two electrodes needs to be much greater than the thickness of the insulating wall, typically greater than twice the wall thickness (that is, the sum of the wall thickness between each of the two electrodes and the fluid to be detected) so that the possible presence of liquid can actually disturb the capacitance between the electrodes. In addition to causing inconvenience problems, such a solution has limits on resolution or measurement accuracy.
[0007] Other types of capacitive sensors are mounted outside a tank, such as a fuel tank for an additive in a vehicle. However, these types of sensors are penalized by the fact that the tank needs to include large wall thicknesses in order to guarantee the necessary mechanical resistance. This results in the need to use signals at a frequency that has greater power in order to detect the level of the liquid in the tank and this determines greater risks of the electromagnetic interference mentioned above. SUMMARY AND OBJECTIVE OF THE INVENTION
[0008] The purpose of the present invention, in its general terms, is to provide a level sensor that is simple and inexpensive to produce, distinguished by great flexibility of use and construction and that is substantially innumerable from the problems highlighted above.
[0009] According to a first aspect, the objective of the invention is to provide a level sensor that can be produced in different lengths while guaranteeing accuracy and reliability.
[00010] According to a different aspect, the objective of the invention is to provide a sensor that is suitable to perform level measurements even under conditions of solidification or at least partial freezing of the medium that is subjected to the measurement.
[00011] According to a different aspect, the objective of the invention is to provide a level sensor with the capacity to distinguish the presence and / or the height of different layers and / or different states of the environment that undergo the measurement, such as a sequence of states and / or layers of the "liquid - air / gas - solid" type or, otherwise, of the "liquid - solid" type, or otherwise of the "air / gas - solid" type or again of the "liquid - air / gas" type.
[00012] According to a different aspect, the objective of the invention is to provide a level sensor capable of detecting variations in height of different layers and / or states of the medium that undergoes the measurement, such as an increase or reduction of a frozen or solidified layer of the medium, for example, a measurement of level changes in a tank containing a liquid during freezing and / or non-freezing.
[00013] According to a different aspect, the objective of the invention is to provide a level sensor that has a structure designed to enable its precise operation even in cases of stress due to freezing and / or solidification conditions and / or heating of the medium subjected to the measurement.
[00014] At least one of the purposes of the invention is achieved by a level sensor and a corresponding control method that has the characteristics specified in the attached claims. The claims form an integral part of the technical teaching provided in this document in relation to the invention. BRIEF DESCRIPTION OF THE DRAWINGS
[00015] Additional objectives, characteristics and advantages of the invention will emerge from the following description, with reference to the accompanying drawings, which are provided only by way of non-limiting examples in which:
[00016] - Figures 1 and 2 are partially seen in schematic perspective in section of two possible alternative configurations for installing a level sensor, according to the invention in a generic container, such as a tank;
[00017] - Figures 3 and 4 are seen in schematic perspective, from different angles, of a level sensor according to an embodiment of the invention;
[00018] - Figure 5 is a schematic perspective view partially in section of a level sensor according to a possible embodiment of the invention;
[00019] - Figure 6 is a partial exploded schematic view of a level sensor according to the possible modality of the invention;
[00020] - Figures 7 and 8 are seen in schematic perspective from different angles of a level sensor circuit according to a possible embodiment of the invention;
[00021] - Figure 9 is a schematic longitudinal section of a level sensor according to a possible modality of the invention;
[00022] - Figure 10 is a first detail on a larger scale of the sensor in Figure 9;
[00023] - Figure 11 is a detail on a larger scale of the sensor in Figure 10;
[00024] - Figure 12 is a second detail on a larger scale of the sensor in Figure 9;
[00025] - Figure 13 is a schematic cross-sectional view of a capture portion of a level sensor according to a possible embodiment of the invention;
[00026] - Figure 14 is a detail on a larger scale of the sensor in Figure 13;
[00027] - Figure 15 is a detail on a larger scale of the sensor in Figure 14;
[00028] - Figures 16, 17 and 18 are seen in schematic and partial perspectives of possible alternative configurations for installing or fixing a level sensor, according to the possible modality of the invention;
[00029] - Figure 19 is a partial and schematic perspective view of a portion of a container to which a level sensor according to Figure 18 can be associated;
[00030] - Figure 20 is a partial and schematic representation with the purpose of illustrating a possible configuration of connection of electrodes of a level sensor according to a possible modality of the invention;
[00031] - Figure 21 is a partial and schematic representation with the purpose of exemplifying a possible circuit configuration of a level sensor, according to Figure 20;
[00032] - Figure 22 is a partial and schematic representation similar to that of Figure 21 with the purpose of exemplifying an alternative circuit configuration of a level sensor according to Figure 20;
[00033] - Figures 23 and 24 are schematic representations with the purpose of illustrating possible additional configurations of connection of level sensor electrodes, according to possible alternative modalities of the invention;
[00034] - Figure 25 is a partial and schematic representation with the purpose of exemplifying a possible circuit configuration of a level sensor, according to Figure 24;
[00035] - Figure 26 is a schematic representation, by means of graphics, with the purpose of exemplifying a possible principle of interpretation of electrical signals or values used in possible modalities of the invention;
[00036] - Figures 27 and 28 are schematic representations similar to those of Figures 20, 23 and 24, with the purpose of illustrating possible additional configurations of connection of level sensor electrodes according to possible alternative modalities of the invention;
[00037] - Figure 29 is a schematic representation of some circuit elements of a level sensor, according to a possible embodiment of the invention;
[00038] - Figure 30 is a partial and schematic representation similar to that of Figure 25, with the purpose of exemplifying a possible additional condition of use of a level sensor, according to a possible modality of the invention;
[00039] - Figure 31 is a schematic perspective view partially in section of a possible variant modality of a level sensor according to the invention; and
[00040] - Figure 32 is a partial and schematic representation with the purpose of exemplifying an alternative circuit configuration to that of Figure 25. DESCRIPTION OF PREFERENTIAL MODALITIES OF THE INVENTION
[00041] The reference to "a modality" or "a modality" in the context of the present description is intended to indicate that a particular configuration, structure or characteristic described in relation to the modality is comprised in at least one modality. Therefore, phrases such as "in a modality", "in a modality" and the like that may be present in different points of the present description do not necessarily refer to one and the same modality, however, preferably, they can refer to different modalities . Furthermore, conformations, structures or particular characteristics defined in the course of the present description can be combined in any suitable way in one or more modalities, even in different modalities from those shown. Numerical and special references (such as "top / top", "bottom / bottom", "top", "bottom", "front", "back", "vertical" etc.) used in this document are provided only as a convenience and, therefore, do not define the sphere of protection or the scope of the modalities. In the Figures, the same reference numerals are used to indicate elements that are similar or technically equivalent.
[00042] In Figure 1, indicated as a whole by 1 is a generic container, in particular a tank, for a generic medium in the fluid or bulk state. Tank 1 preferably has a main body, produced from electrically insulating plastic material. Tank 1 may be associated with a heater of a type known per se, used to heat the tank itself and / or its contents, for example, in the event of freezing. An electric heater is represented schematically in the Figure by the block indicated with EH.
[00043] Tank 1 can, for example, be a tank that equips a motor vehicle. In one embodiment, such as that exemplified in this document, tank 1 is designed to equip a vehicle with a diesel engine, and the liquid contained in tank 1 is a liquid known as an AdBlue, that is, a solution of urea in 32.5% (minimum 31.8% - maximum 33.3%) in demineralized water, used by a SCR (Selective Catalyst Reduction) system, that is, a system to reduce nitrogen oxide emissions from the exhaust gases by a diesel engine.
[00044] In the schematic example illustrated, the tank has an upper wall 2, in which an opening is provided which has a plug 3 for upper coating. The wall of the tank 1, for example, the bottom wall of the same 4, then has an outlet opening, not visible, through which the liquid exits or is extracted, for example, by means of a pump, to feed the SCR system with the liquid. Again in the upper wall 2, the tank 1 has a second opening, indicated by 5, fixed in a position corresponding to which, in a fluid-impermeable manner, there is the body of a level sensor according to a possible modality. The level sensor, indicated as a whole by 10, is mounted so that it extends according to a level detection geometry axis, indicated with X, preferably substantially vertical, but possibly, if necessary, inclined in relation to to the vertical position.
[00045] The sensor 10 has a catching part 11 indicated to extend at least partially inside the tank 1. The distal end region of the catching part 11 is preferably in contact with the bottom wall 4 from the tank, or at a small distance from it, that is, at a height very close to the opening for the liquid extraction outlet, in order to detect the presence of an even lower level in the tank. In an embodiment not shown, the distal end region of the catching part 11 is fixed inside the wall of the tank 1 as opposed to the wall provided with the opening 5 in which the sensor 10 is installed and fixed, preferably by means of a quick release coupling or fixation. Preferably, the proximal end region of the catching part 11 extends within the tank 1 to a height relatively close to the upper wall 3.
[00046] In the illustrated mode, the sensor body 10 has, at the top of it, elements for fixing it to the upper wall 2 of the tank. In the example, these means are represented by flange formations with associated screws (not shown). This modality should not be understood in any way as limiting, since there are different possible solutions for fixing the body of the sensor 10, among which some are exemplified hereinafter.
[00047] In the example of Figure 1, sensor 10 is fixed at the top, that is, associated with the upper wall 2 of the tank. However, in other modalities, the sensor can be attached at the bottom, that is, to the bottom wall 4. Such a modality is illustrated schematically in Figure 2, in which the sensor 10 is mounted in a fluid impermeable manner in a position corresponding to opening 5, defined in the present context on the back wall 4. In addition, in this embodiment, a region of proximal end (which can be defined in the present context as lower) of the capture part 11 is in a position close to the wall bottom 4, while the distal end region (which in the present context can be defined as upper) is at a height relatively close to the top wall 3. Furthermore, in such a solution, the distal end of part 11 can be attached to the wall 3 by means of suitable coupling means of the type indicated above.
[00048] In Figures 3 and 4, a sensor 10, according to a modality, is shown isolated, at different angles. At the proximal end of part 11, the body 10a of the sensor 10 defines a housing of the box type 12, which also includes a generally hollow connector body 12a, provided with electrical terminals described hereinafter which project, preferably, from a wall side of the housing. The housing 12 is preferably provided with a closing cap 13 which can be held in position in a fluid impermeable manner, for example, by means of a weld between the plastic material of the housing 12 and the plastic material of the cap 13.
[00049] Between housing 12 and part 11, body 10a of sensor 10 preferably defines a portion or formation 14 for coupling in a liquid impermeable manner in a position corresponding to the respective installation opening in the tank. Formation 14 defines at least one seat for at least one sealing member 15 which can also perform the elastic mounting functions of the sensor 20 in the tank. In one embodiment, at least two elastic elements of a type of O-ring are provided, among which one performs the sealing functions and the other is exploited to obtain the elastic assembly of the sensor 10 in the tank 1, for example, in order to to compensate for the set tolerances. In the illustrated example, formation 14 has a substantially circular profile, and the sealing element is an O-ring. Then, indicated with 12b in Figures 3 and 4 are the flange formations mentioned above to fix the sensor body 10a which, in the present context, they are defined at the bottom of the housing 12.
[00050] In Figure 5, a sensor 10 according to a modality is represented partially in section in order to highlight the way that the body 10a of the same is hollow internally in order to house the level detection components. From the Figure, it is possible to verify in particular the way that the sensor body 10a defines, in a position corresponding to the capture part 11, a hollow shell 16, which has a generally elongated shape. In the illustrated example, housing 16 has a generally prismatic, in particular substantially parallelepipedal shape. As will be seen, in a variable embodiment, at least the housing 16 can be obtained by means of a direct overmoulding of electrically insulating plastic material on a circuit substrate described hereinafter. More generally, the sensor 10 has at least one insulation layer, to electrically isolate the electrodes (described hereinafter) in relation to the interior of the tank 1.
[00051] In a preferred embodiment, the housing 12 with the formation 14 and the enclosure 16 are defined by a single body 10a produced from electrically insulating plastic material, as can be clearly seen, for example, in Figure 6. Without exclusion on the other hand, of the invention there is an embodiment of the body 10a in distinct parts made fixed in relation to each other in a fluid impermeable manner, for example, by means of mutual coupling means or, otherwise, by means of welding or overmoulding.
[00052] In one embodiment, the body 10a or at least the projected portion of it to be exposed directly or indirectly to the liquid (the casing 16 and possibly the fixing portion 14) is produced from a moldable thermoplastic material, such as polypropylene (PP) or high density polyethylene (HDPE). The practical tests conducted by the present applicant, on the other hand, make it possible to prove that a particularly suitable material - also in view of the particular level detection modalities described hereinafter - is a cyclic olefin copolymer (COC). Such materials, often used in the medical field, have particularly advantageous characteristics for the application considered in this document, among which can be mentioned low density, very low water absorption, excellent barrier properties in relation to water vapor , high rigidity, resistivity and hardness, high resistance to extreme temperatures and thermal shocks, excellent resistance to aggressive agents such as acids and alkalis, excellent electrical insulation properties and easy workability with the use of common methods of treating thermoplastic materials, such as injection molding, extrusion, blow molding, injection blow molding.
[00053] The material, or at least one of the materials used to supply the body 10a of the sensor 10, can be similar to a material that supplies at least part of the tank 1, for example, in order to allow a fluid impermeable welding between the sensor body and the tank, or chemically compatible with it. One or more of the materials indicated above can be used to provide different portions of the body 10a, such as the housing 12 with the formation 14 and the casing 16, even when the body 10a is produced from different parts made fixed in one relation to the other. Of course, the lid 13 can also be obtained from one of the indicated materials.
[00054] Again, in Figure 5, it can be verified the way they are housed in the cavity defined by the sensor body 10, indicated as all with H, the electronic and electrical detection components. In a preferred embodiment, these components are mounted on an electrically insulating substrate 20 that provides a circuit substrate. The substrate 20 is produced from a material suitable for creating printed circuits, such as, for example, FR4 or a similar composite material, such as fiberglass or, again, a polymer-based ceramic material, preferably a material that can be molded to enable the production of the substrate 20.
[00055] On the circuit substrate 20, there may be identified a first portion 20a that must be received in housing 12 and a second portion 20b that must be received in housing 16. Predominantly associated with portion 20a of substrate 20 are the electronic control components of sensor 10, as well as corresponding terminals for external electrical connection of sensor 10. Instead, associated with portion 20b of substrate 20 are the detection components, including a series of electrodes. Some of these electrodes are indicated in Figure 5 by the letter "J" followed by the number that identifies the electrode position in the series that extends from the proximal end (electrode J1) to the distal end (electrode Jn) of the capture part 11, that is, from the 20b portion of the substrate 20.
[00056] In the illustrated example, a single circuit substrate is provided in which parts 20a and 20b are defined, however, in possible varying modalities, several circuit substrates connected together by means of suitable electrical interconnection means and possibly possibly mechanical interconnecting means (e.g., a circuit substrate corresponding to portion 20a and a circuit substrate corresponding to portion 20b, with conductors or electrical connectors for connecting electrically conductive paths of one portion to electrically conductive paths of the other portion).
[00057] In Figure 6, a sensor 10 according to an embodiment of the invention is shown in an exploded view, in which the various parts already identified above can be seen. Visible in this Figure are the terminals mentioned above, indicated with 21, preferably with a generally flat shape, for example, obtained by means of molding and / or stamping of metal belt, which supplies, with the connector body 12a fixed in relation to the housing 12, an interface for external connection of the sensor 10, for example, to a control unit of the SCR system on board the vehicle.
[00058] In one embodiment, each terminal 21 has a blade-shaped contact portion 21a, designed for positioning the connector body 12a inside the cavity and a narrow interconnection portion 21b, designed for electrical and mechanical coupling to the contacts respective 22 present in the substrate 20, in particular, in the portion 20a thereof, which are hereinafter described.
[00059] Again visible in Figure 6 there is the substrate 20 as a whole, with the corresponding parts 20a and 20b, with associated electrical and electronic components. The substrate 20 is also shown in isolation in Figures 7 and 8, which represent opposite views of the larger faces of the same. The circuit substrate 20, which is generally shaped and preferably elongated, has a control circuit arrangement indicated on one of its larger faces, conventionally defined in the present context as "rear", as a whole. preferably 23, comprising an electronic controller 24, for example, a microcontroller. The controller 24 preferably comprises at least one logical processing and / or control unit, a memory circuit and inputs and outputs, among which the inputs of an analog / digital type.
[00060] The components of the circuit arrangement 23 are connected to the electrically conductive paths provided in the portion 20a which are visible, for example, in Figure 8 (without any reference number). At the back of the substrate portion 20b, then, a series of electrically conductive paths 25 is provided for the electrical connection of the electrodes J of Figure 5 - preferably with metallized through holes for connection between the paths on different surfaces - and of possible other components available 23.
[00061] In one embodiment, the circuit comprises at least one temperature sensor, provided, in particular, on the corresponding circuit substrate 20. Such sensor, for example, of an NTC type, can be mounted in at least one among the region of the distal end and the proximal end region of the 20b portion of the substrate 20. In the example shown, mounted on the 20b portion of the substrate 20, in particular, on the back of the substrate, there are two temperature sensors 26 and 27, in end regions opposite from the portion 20b, connected to the circuit 23 layout by means of corresponding conductive paths. Assuming an installation of sensor 10 in tank 1 of the type illustrated in Figure 2, temperature sensor 27 can be used to detect the temperature of the liquid, whereas sensor 26 - which in the installed condition is closest to the upper wall Tank - can be used to detect the temperature in the internal volume of the tank above the liquid, for example, the air temperature. A configuration of the type represented, in particular, with two temperature sensors 26 and 27, makes it possible to install sensor 10 in tank 1 both in the configuration of Figure 1 and in the configuration of Figure 2, inverting, at a software level, the functions, such as the functions of the two sensors and / or the functions of the electrodes J.
[00062] A sensor to detect the temperature can be provided inside the portion 20a of the substrate, that is, inside the housing 12. Of course, it may also be possible to supply more than two temperature sensors, for example, with one or more sensors in intermediate positions between those of sensors 26 and 27.
[00063] Clearly visible in Figure 8 is the front of the substrate 20 in the portion 20b whose electrodes J are arranged, of which only a few are shown. In the non-limiting example shown, the electrodes J - which are thirty-seven in number - are arranged according to an arrangement that extends according to the length direction of the substrate portion 20b, that is, along the geometric axis of detection X separated from each other. The J electrodes are produced from an electrically conductive material, for example, a metal material or a metal alloy and are associated with the front of the 20b portion of the substrate 20. The J electrodes are preferably coplanar and can therefore example, be in the form of plates or sheets etched in etching or applied to substrate 20 or, otherwise, constituted by an electrically conductive layer - similar to trajectories 25 - which is arranged on substrate 20, for example, with a silkscreen printing technique or the like.
[00064] As mentioned, in one embodiment, substrate 20 has through holes - partially visible in Figures 7 and 8, where one is designed by F - which contains conductive material for electrical connection between the electrodes J provided in front of portion 20b and the conductive paths 25 present at the rear of the substrate portion 20b 20.
[00065] Referring again to Figure 6, a part of the blind cavity H that extends axially in the body 10a of the level sensor is visible, that is, in parts 12, 14 and 16 thereof. Within this cavity H, guide and positioning elements are preferably provided for the substrate 20, some of which are partially visible in Figures 5 and 6, where they are indicated with 16a and 12c, in a position corresponding to the enclosure 16 and in a position corresponding to the housing 12, respectively. The positioning elements for the substrate 20 can possibly be provided in the lid 13.
[00066] In Figure 9, the level 10 sensor is visible in a longitudinal section, from which the presence of the blind cavity H extending in the housing 12, in the fixation formation 14 and in the housing 16, can be clearly verified. in which cavity H the circuit substrate 20 is housed. From this Figure, it can be clearly seen how, in one mode, temperature sensor 27 is defined in a position close to formation 14 or, more generally, in an installed condition of sensor 10, in a position close to to the wall of tank 1 provided with the opening for the installation of sensor 10. From a comparison between Figures 7 and 8, on the one hand, and Figure 9, on the other hand, it can also be observed that the electrode indicated with J1 also it is, in the installed condition of Figure 2, in a position close to the bottom wall of the tank, preferably a position that can be reached by the liquid even in a condition despite the minimum filling of the tank. As will be seen, in one embodiment, the J1 electrode is used to supply a reference value used in the liquid level detection course. According to a different modality, the electrode J1 can, for this purpose, be used in combination with at least one additional reference electrode J at a different potential or voltage. On the other hand, one or more reference electrodes J can also be provided in other areas of the substrate portion 20b.
[00067] Also visible in Figure 9 is the connector body 12a, with one of the corresponding terminals 21. The terminals 21 can be fitted by interference in corresponding passages defined in the connector body 12a or possibly at least the housing body 12 can be overmoulded at the terminals. Preferably, the terminals, and the corresponding passages of the connector body extend longitudinally in a direction substantially perpendicular to a plane identified by the circuit substrate 20 and / or by the electrodes J.
[00068] In one embodiment, contacts 22 are configured for elastic coupling to terminals 21 in order to obtain electrical and mechanical connection between them. Visible in Figure 10 and even more in detail in Figure 11, there is a possible modality of coupling between the portion 21b of a terminal 21 with a corresponding contact 22 provided in the portion 20a of the substrate.
[00069] In the exemplified embodiment (see Figure 11 in particular), the contacts have a flat base 22a provided with a hole or central passage 22b. Moving away from the base 22a, on opposite sides of the passage 22b there are at least two flaps 22c that converge towards each other. The body of the contacts 22 is produced from an electrically conductive material, such as a metal or metal alloy, for example, phosphor bronze, preferably coated with tin or gold or other material designed to improve electrical contact.
[00070] The flaps 22c are inserted into a corresponding through hole 20c defined in the portion 20a of the substrate, and the base 22a is fixed and / or welded to a surface of the substrate itself or to its conductive paths. Preferably, the hole 20c is surrounded by the electrically conductive material of one of the paths of the layout of the circuit layout 23, with the base 22a of the contact 22 that overlaps at least partially with the conductive material mentioned above in order to obtain the electrical connection. As also seen in Figure 11, in the assembled condition, the passage 22b of a contact is substantially aligned with the hole 20c of the substrate 20, with the base 22a fitted against a surface of the substrate itself (in the present context, a back surface) and with the flaps 22c that project, preferably, from the hole 20c on the opposite surface (in the present context, the front surface) of the substrate 20.
[00071] For the purposes of mounting the sensor, the substrate 20, already provided with the corresponding electrical and electronic components, is inserted into the cavity H of the body 10a of the sensor 10 from the open part, that is, from the housing 12. Therefore, after insertion, the portion 20b of the substrate 20 is positioned predominantly within the housing 16, while the portion 20a is positioned within the housing 12. The position of the contacts 22 and the holes 20c in the substrate 20 is so that, following the aforementioned insertion of the substrate 20 in the body 10a, these holes and contacts face the passages inside the connector body 12b. Then, the terminals 21 interference fit into the corresponding passages of the connector body 12a so that the respective interconnecting portions 21b penetrate the holes 22a and 20c of the contacts 22 and the substrate 20, respectively. Then, the portions 21b of the terminals penetrate between the flaps 22c, which causes elastic bifurcation of the same, which guarantees an adequate electrical connection and a well-balanced mechanical connection. Preferably, the elastic electrical connection above is also suitable to prevent any possible damage to the substrate 20 and the corresponding circuit due, for example, to possible mechanical stresses during the use of the sensor 10, such as vibrations or stresses applied to the terminals 21.
[00072] It will be observed that the assembly of the sensor is very simple and readily capable of automation, which gives elementary operations in them, represented by the insertion of the circuit substrate 20 in cavity H of the body 10a and fitting by subsequent actuation of the terminals 21 in the corresponding passages of the connector body 12a.
[00073] As will be mentioned, in one embodiment, the body 10a of the sensor 10 is provided with guide elements and / or positioning for the substrate 20. The presence of these elements simplifies the additional assembly of the sensor 10, while guaranteeing a high precision of assembly between the parts and a greater precision of measurement. The positioning elements mentioned above can be provided with at least one of the housing 12 and the housing 16, preferably both in the housing and in the housing. As already mentioned, one or more positioning elements can be provided in the cover 13 of the housing 12.
[00074] With reference, for example, to Figures 10 and 11, in one embodiment, defined within each of the two opposite side walls of housing 12 are insertion and positioning guides, indicated with 12c, which are generally parallel to each other and between which a border region of the substrate 20, in particular of the portion 20a thereof, can be engaged. In the illustrated example, the guides 12c are defined in relief on the inner surface of the opposite walls mentioned above of the housing 12 (see, in this respect, also Figure 6, in which the type of a guide 12c is visible), however, without excluding the scope of the invention there is a modality in which the guides that have similar purposes to the guides 12c are constituted by recesses that extend in the longitudinal direction of the sensor body 10. Preferably, the top of the guides 12c is shaped so as to have a portion of introduction of centralization, in the present context defined by an inclined surface, designed to facilitate the introduction of the opposite edges of the portion 20a of the substrate in the respective pairs of guides 12c. The portion 20a of the substrate 20 can be inserted with little interference between the guides 12c or with minimal clearance.
[00075] From Figure 10 it can be seen the way that, in a preferred embodiment, the lid 13 also has, on the side of the top wall of it, a positioning formation 13a that defines a seat for the proximal or upper edge (as seen in the Figure) of portion 20a. In addition, in this case the positioning formation 13a is preferably shaped so as to define a centering introduction portion, in the present context, which comprises two converging inclined surfaces, in order to facilitate the introduction of the proximal or upper edge of the portion 20a in the corresponding seat when the lid 13 is mounted in the housing 12. The formation 13a preferably comprises a surface or contrast element 13b suitable to prevent undesirable axial movements of the substrate 20.
[00076] In a preferred embodiment, defined between the distal end of the casing 16 and the distal end of the substrate 20 (that is, of the portion 20a of the same) there is a free space or gap, in particular, to enable the compensation of possible degrees different from thermal expansions of the material constituting the shell 16 and the material constituting the substrate 20. Such clearance is indicated with H1 in Figure 12, which represents an enlarged detail of the sensor of Figure 9, in particular, of the distal end portion of sensor 10. In order to clarify this aspect, it should be considered that a preferred context of use of sensor 10, which is the vehicle sector, covers reaching very low temperatures, for example, as low as -40 ° C, although the device is preferably produced substantially at room temperature, for example, at 25 ° C. With reference to this numerical example, the sensor 10 therefore undergoes a considerable thermal oscillation, which corresponds to a variable shrinkage of the housing 16 according to the plastic material used.
[00077] If the jump above a temperature of 65 ° C (from +25 ° C to - 40 ° C), then the gap H1 is expected to allow free contraction of housing 16, without coming into contact with the distal edge or edge of substrate 20 and / or an H1 clearance is expected to prevent the contraction above housing 16 from damaging one or more electrodes J. With reference to the materials mentioned above, the following thermal expansion values can be considered: - HDPE => 200 ppm / ° C - PP => 120 ppm / ° C - COC => 60 ppm / ° C - FR4 (substrate 20) => 20 ppm / ° C
[00078] Now considering the formula H1 (mm) = unit h (mm / mm) x length Lu of the sensor (mm), for the temperature jump determined in the present context as an example (65 ° C), the following values of unit h can be considered: - h for HDPE = 0.012 mm / mm - h for PP = 0.007 mm / mm - h for COC = 0.003 mm / mm
[00079] Consequently, for example, for a sensor body 10 with Lu = 150 mm produced from HDPE, the minimum value of H1 is 0.012 x 150 = 1.8 mm; for a sensor body of identical length Lu produced from PP, the minimum value of H1 is 0.007 x 150 = 1.05 mm; for the same sensor body produced from COC, the minimum value of H1 is 0.003 x 150 = 0.45 mm.
[00080] In a preferred embodiment, the portion 20b of the circuit substrate 20 is positioned inside the housing 16 of the body 10a of the level sensor so that the front of the same, that is, the face of the same with the electrodes J, is adjacent or to the corresponding inner surface, that is to say fitted against it, preferably at least partially in contact with it. For this purpose, preferably, inside the housing 16 one or more positioning elements are provided, which tends to propel the portion 20b of the substrate towards a wall of the housing 16. In one embodiment, projecting from from within a wall of the enclosure 16, there is at least one positioning element mentioned above, which extends towards the opposite wall of the enclosure itself.
[00081] A possible modality in this sense is visible in Figure 13, which is a cross-sectional view of the enclosure 16 (in particular, according to a plane orthogonal to the geometric axis X that passes, for example, through line XIII-XIII in Figure 4). From this Figure, it is possible to verify the way in which the reliefs 16a are projected from the interior of the larger walls of the enclosure 16 (among which one is also visible in Figures 5 and 9), which are generally parallel to each other and extend in the longitudinal direction of the wrapper, preferably, but not necessarily, for the entire length of the wrapper (these reliefs possibly having intermediate interruptions). The reliefs 16a, in the present context defined integrally by the body 10a or the housing 16, preferably have a tapered profile so that a generally pointed or tapered top of the same is pressed against the back of the portion 20b of the substrate 20. As noted , after insertion of the substrate 20 into the cavity H, the reliefs 16a are designed to urge the front of the part 20b against the inner surface of the wall of the housing 16 as opposed to that from which the reliefs themselves arise. This stress advantageously has an elastic component, due to a certain elasticity of the plastic material that constitutes the wrapper 16.
[00082] In one embodiment, the positioning element 16 or each positioning element 16 is produced from a material other than the material of the casing 16, such as an elastomer, for example, molded or molded or overmolded in the casing 16 and / or has a different shape than the one shown, although designed to operate in a way to exert buoyancy and / or to operate elasticly on substrate 20 and electrodes J.
[00083] In a preferred embodiment, the relief or reliefs 16a is / are configured / configured in such a way that they can yield elasticly and / or be able to undergo deformation at least in the top area of the same / of them in order to allow the insertion of the substrate 20 even in the case where the thickness of the latter is greater than the distance between the tip of the relief or reliefs 16a and the inner surface of the casing 16 which faces the top tip (a condition that can arise as a result of dimensioned tolerances due to different degrees of shrinkage of the plastic material during the corresponding molding process), in any case, guaranteeing the thrust mentioned above.
[00084] In one embodiment, inserted into the casing 16, or in any mode at least from the substrate 20 and the corresponding facing wall of the casing 16a, is the fluid filling material which is not electrically conductive, such as a fluid material electrically insulating, in order to preferably guarantee the absence of air bubbles - in particular, between the electrodes J and the housing 16 - which can invalidate the appropriate level measurement, which is carried out according to the modalities described hereinafter. The filler material mentioned above, which is preferably designed to encapsulate and / or be in contact with at least portion 20b of substrate 20, can, for example, be a polyurethane resin or, preferably, a gel, with more preferably, a silicone gel. A silicone gel suitable for application is, for example, the gel called SilGel® 612, marketed by Wacker Chemie AG, Munich, Germany.
[00085] The presence of the general filling or insulating material, for the sake of brevity below, also defined only as "gel", mainly serves to fill the possible gaps that arise between the front of the sensor portion 20b and the wall of the casing 16 which faces it. These spans, despite the minimum volume, may exist, for example, due to the surface roughness of the substrate 20 and / or the electrodes J or again when the electrodes J have a thickness that determines a small projection of the same from the front surface of the portion 20b of the circuit substrate or again due to roughness and / or possible deformation of the wall of the housing 16, for example, following the surface finish of the corresponding mold and / or shrinkage other than the polymeric and / or thermoplastic material in the case to shape the casing 16.
[00086] The ideas presented above are further clarified by the details shown in Figures 14 and 15. Clearly visible in the detail in Figure 14 is the top of the relief 16, which presses on the back of the substrate portion 20b, thereby pushing the electrodes - one of which is indicated with J - against the inner surface of the wall facing the housing 16. The additional magnification of Figure 15 highlights the interface area between the electrode J and the wall mentioned above of the housing 16, from which it can be checked the way that, in the exemplified case, the facing surfaces of the two elements in question have respective microcavities, for example, due to surface roughness and / or material deformations (for example, different shrinkage of the material during molding, small warping , etc.). In the presence of the aforementioned gel - indicated with G in Figure 15 at the interface between the aforementioned microcavities - the reliefs 16a push the part 20b of the substrate 20 against the inner surface of the shell 16, thereby favoring the exit of the excess gel between the two parties concerned. In this way, between the facing parts, only a G-gel film is strictly necessary to fill the aforementioned microwells. The aforementioned outlet of the excess gel G is preferably allowed by the presence of at least one outlet chamber in the shell 16, for example, comprising a part of the cavity H internal to the shell 16 that is not occupied by the substrate 20 and the reliefs 16a. This chamber is shown schematically with H2 in Figure 13 (the H2 chamber may possibly comprise the space previously indicated with H1).
[00087] From Figure 14 a deformation or small removal of the material of the relief type 16a can be observed which, in the example, presumes precisely a nominally rounded tip. As explained, the tapered shape of the reliefs 16a has the purpose of allowing a deformation, in particular, in the case where the portion 20b of the circuit substrate is forcibly fitted in the cavity of the enclosure 16 (for example, in the case of dimensional shrinkage excessive or tolerances due to the molding of the housing itself) and to ensure both the thrust mentioned above for the purpose of obtaining a satisfactory contact between the electrodes J and the inner surface of the housing 16 and causing the excess gel to efflux, for the purposes of accurate and reliable detection. In this respect, it should be considered that, in the preferred embodiment, the gel is introduced into the cavity of the casing 16 in order to substantially fill it, however, for practical purposes, it is sufficient for the gel to be present in the interface area between the portion 20b of the substrate with the electrodes J and the facing surface of the housing 16, where the excess gel can, as has been said, flow into the outlet chamber H2 mentioned above inside the housing.
[00088] As already mentioned, the modalities of fixing the body 10a of the level sensor 10 to the tank may differ from the modalities previously exemplified. In general, the coupling can be based on the presence of elements in the relief associated with one of the body 10a of the sensor 10 and the tank 1, which are provided for coupling to the cavities or seats present in the other between the tank and the body 10a of the sensor, the coupling preferably taking place after a movement that is partly axial and partly angular. In one embodiment, the mechanical coupling between the body 10a and the tank is a quick coupling, for example, a quick lock coupling or a threaded coupling or a quick release coupling. Figure 16 exemplifies the case of a coupling between the sensor 10 and the tank 1 based on a substantially one-bayonet type coupling system. In this example, the sensor body 10a is provided, in the fixing portion 14 of the same, with a plurality of teeth or surface hitch reliefs, of which only one is visible, indicated with 12d, which are designed for coupling to seats respective coupling lugs 5a defined in peripheral positions in relation to the opening 5 of the wall of the tank 1 provided with the opening 5, in the present context, the bottom wall 4. Preferably, the wall mentioned above of the tank 1 has, in a position corresponding to the opening 5, a cylindrical housing for receiving the fixing portion 14 and the corresponding gasket 15, with the seats 5a extending between the upper face of the wall 4 and the cylindrical surface of the housing mentioned above. For the purposes of coupling, the body 10a is inserted through the opening 5, until the gasket 15 rests on a corresponding contrast surface defined in the cylindrical housing mentioned above, in which the fixation portion is also received. This insertion is done in such a way that the reliefs 12d begin to enter a substantially vertical extension of the respective seats 5a. A subsequent angular movement transmitted in the body 10a determines the passage of the reliefs 12d in the substantially horizontal extension of the seats 5a, with consequent engagement between the parts, as typically occurs in bayonet coupling of a known type (in which there are, at all, inclined extensions on seats possibly covered 5a).
[00089] In one embodiment, additionally or alternatively, a coupling is provided inside the tank, such as a coupling based on coupling reliefs associated with one between the distal end of the sensor 10 and the facing wall of the tank, being that these coupling reliefs are coupled to the cavities present in the other between the end and the distal wall. For example, the distal end of the casing 16 may be provided with one or more grooves or hitch teeth, preferably radial grooves, intended for coupling to respective hitch seats defined in an element that rises from the wall of the facing tank to the distal end mentioned above. The above coupling inside the tank can comprise elements technically equivalent to those described with reference to the example in Figure 16.
[00090] A coupling of the type illustrated in Figure 16, in addition to not requiring specific tools, makes it possible to obtain elastic assembly of the body 10a of the sensor 10 in the tank 1. In the embodiment shown in Figure 16, the shape of the housing 12 is substantially cylindrical, without prejudice the characteristics of the same described above.
[00091] In one embodiment, the fixation between the body 10a of the level sensor and tank 1 is of a permanent type, for example, obtained by means of gluing or welding. Such a solution is exemplified in Figure 17, in which the elevation outside the wall 4 of the tank 1 (however, it may be the wall 2) is an annular relief 2a, in the present context, a substantially quadrangular relief, which circumscribes a region of the wall 4 in which the opening 5 is defined, in the present context, which substantially consists of a slot having slightly larger cross-sectional dimensions than the housing 16. In this case, the fastening portion 14 of the body 10a is substantially shaped complementary to the closed profile defined by relief 2a, that is, quadrangular in the illustrated example and is preferably provided with an annular relief specific to it, complementary or specular to relief 2a, not shown. For coupling purposes, the housing 16 of the body 10a is inserted into the opening 5, until the fixing portion 14 engages with the relief 2a. The definitive fixation between the portion 14 and the relief 2a can be obtained by means of an adhesive deposited in at least one of the two parts in question (in which this adhesive also performs the function of guaranteeing fluid impermeability) or, otherwise by welding the portion 14 and the relief 2a between them, for example, by means of laser or vibration or ultrasonic welding or again by re-melting the material or the so-called hot blade welding. Of course, in this case, the materials that make up the wall 2 or 4 of the tank 1 and the fixing portion 14 of the sensor body are materials that are compatible in view of the fact that they must be welded together.
[00092] In the embodiment shown in Figure 17, the housing wall 12 from which the connector body 12a protrudes and the connector body itself has a different structure from the cases illustrated above, without prejudice to the characteristics of the device described with reference to Figures 1 to 15. In Figures 16 and 17, the connection between the terminals internal to the connector body 12a and the internal circuit of the sensor 10 is also different from the connection shown above. According to these variables, the electrical connectors are preferably provided with a connector body 12a shaped in order to define switching means, a design to enable exclusive coupling with a respective external electrical connector and / or restraint means, designs to enable coupling with the external connector mentioned above only in the direction, thereby preventing reversals of polarity or erroneous connections.
[00093] Figure 18 illustrates a variable modality similar to that of Figure 16, however, distinguished by the presence of two elastic elements 15 'and 15 ", in the present context represented by O-rings, with the fixation portion 14 that defines corresponding seats for these elements. Preferably, the surface hitch reliefs 12c are defined in the portion 14 in an intermediate position between the two elastic elements 15 'and 15 ", that is, in an intermediate position between the corresponding positioning seats. As shown in Figure 19, in such an embodiment, the cylindrical housing in the installation opening 5 is shaped so as to have two axial resting surfaces 5b and 5c for the elements 15 'and 15 ", respectively, with the coupling seats 5a for the reliefs 12d that are in an intermediate position between the surfaces mentioned above.
[00094] In such an embodiment, a lower gasket 15 "performs sealing functions, in particular, radial sealing, between the portion 14 of the body 10a and the interior of the corresponding cylindrical housing. The elastic element 15 'is, instead, designed to be axially compressed between the corresponding resting surface of the portion 14, indicated with 14a in Figure 16 and the surface 5b of the cylindrical housing, thus, in the installed condition, the elastic reaction of the element 15 'impels the body 10a as a whole towards the exterior of the housing (downwards, with reference to Figure 18), thus ensuring an elastic assembly and the recovery of possible tolerances between the parties involved.
[00095] As stated, the installation configurations described with reference to Figures 16 to 19 can also be used when the level 10 sensor is associated with the top wall of the tank, similarly to the illustration in Figure 1.
[00096] As seen, in the modalities described so far, the level 10 sensor includes an array of capacitive elements, among which each includes a single electrode J1 to Jn (where "n" is equal to 37, in the examples illustrated so far). The word "unique", in the present context, should indicate that each J electrode belongs to a capacitive element that does not require an additional electrode, as typically occurs in known capacitive level sensors, which presupposes the presence of pairs of electrodes or plates facing corrected by finger (interdigitated) or, otherwise, the presence of a common electrode or plate, facing which there are a plurality of electrodes or plates. In other words, in the solution proposed in this document, each J electrode provides the plate of a type of "virtual capacitor", whose other plate is obtained by the medium that is subjected to the measurement present in the tank and in which the wall defined between them of the housing 16 - or another layer of insulation that replaces it - constitutes the dielectric or the insulator between the plates of the virtual capacitor, to which, possibly, the dielectric or the isolate constituted by the gel layer G described above may be added.
[00097] Therefore, in practice, each J electrode provides, along with the corresponding electronic control components, a type of capacitive proximity sensor, which can detect the presence or absence of the medium even without direct contact with the latter. This type of operation is based on the principle of detecting the capacitance of a capacitor. The electrode J is the sensitive side of the capacitor and constitutes a plate of the same, while the possible presence in the vicinity of an electrically conductive medium provides the other plate of the capacitor. Thus, the presence or absence of a medium in the vicinity of each electrode J determines a capacitance that the electronic components are capable of detecting.
[00098] In the application considered in this document, each J electrode can then supply at least two different capacitive structures according to the possibility of the liquid being present or absent in front of them, namely, at least:
[00099] - a first capacitive structure that has a first capacitance value, when an electrode J is facing the liquid, that is, when the level of the liquid in the tank corresponds to the electrode J considered or is above it; and
[000100] - a second capacitive structure that has a second capacitance value, when the electrode J is not facing the liquid, that is, when the level of the liquid in the tank is below the considered electrode J.
[000101] In the preferred embodiment illustrated, as seen, the electrodes J are insulated from the liquid, as long as they are contained in the electrically insulating and liquid impermeable housing 16: the wall of the housing 16 towards which the electrodes J are facing, with the electrically insulating substrate 20 and / or the air and / or the possible gel layer G defined between them, it can then be considered as a type of dielectric of the "virtual capacitor" mentioned above.
[000102] In the preferred mode illustrated, as seen, the electrodes J are insulated from the liquid, as long as they are contained in the electrically insulating and liquid impermeable housing 16: the wall of the housing 16 towards which the electrodes J are facing, with the electrically insulating substrate 20 and / or the air and / or the possible gel layer G defined between them, it can then be considered as a type of dielectric.
[000103] The wall thickness of the housing 16, which faces the electrodes J, that is, the insulation layer, can be between 0.1 and 5 mm, preferably between 0.6 and 1 mm, with more preferably, approximately 0.8 mm. As already mentioned, in addition, the hollow housing 16 can be replaced by a direct overmoulding of plastic material on the sensitive element or by a generic wall or by an insulating layer of the J electrodes, with a thickness of the part that faces the J electrodes similar to that indicated for the homologous wall of the enclosure 16.
[000104] Each electrode J is electrically connected - by itself or otherwise in common, in particular, in parallel, to at least one other electrode J, as explained hereinafter - to a respective input of a plurality of controller inputs 24 that belongs to circuit layout 23. Preferably, provided between each input of the controller and a corresponding electrode J there is a filter resistor (two of these resistors are indicated with R1 and Rn in Figures 6 and 7). Controller 24 is substantially predisposed to discriminate the capacitance value associated with each electrode J at least between the first and second values said above capacitance and, consequently, identify at least one liquid / air transition in the tank, which is indicative of the level the middle when it is in the fluid state. In a preferred mode, controller 24 performs a sequential sampling of the capacitance values present at the inputs to which the J electrodes are connected in order to identify the transition mentioned above.
[000105] Controller 24 is preferably a digital electronic microcontroller with an analog to digital converter. Just as an example, a commercial microcontroller suitable for the order proposed in this document is the one identified by the code PIC16F1517 sold with Microchip Technology Inc., Chandler, AZ, USA In any case, it should be noted that the functions of the controller 24 they can be, at least partially, implanted through dedicated external circuits. For example, in a preferred embodiment, controller 24 consists of a microcontroller that implements an analog to digital converter module, however, in other modalities, controller 24 may include a microcontroller (or a microprocessor or an ASIC or an FPGA) and an integrated circuit (either external or independent) to perform the functions of analog to digital converter.
[000106] Figure 20 shows schematically a controller 24 that, just for example, includes "n" inputs IN signal (in the present document twenty in number), connected to which, by means of corresponding conductive paths 25, are maximum possible number of J electrodes in a single configuration (ie, not connected in common or in parallel with other electrodes).
[000107] In a preferred mode, the detection of the capacitance value in each of the IN inputs is done indirectly, for example, based on the measurement of a voltage or, otherwise, converting an input capacitance into an equivalent resistance and then converting, the current measured by means of the equivalent resistance in a digital count. In such cases, preferably, the IN inputs of controller 24 are analog inputs, and the controller implements or has an analog to digital converter associated with it.
[000108] In a preferred mode, associated with each IN input there is a sampling or measurement circuit that includes a controllable switch and a capacitor which, in the present context, are also called "sampling switch" and "holding capacitor ". The controllable switch is switchable between a first position, in which the holding capacitor is connected to a voltage source, and a second position, in which the capacitor itself is connected to a respective J electrode or to several J electrodes connected in common ( in parallel). Preferably, the above voltage is a DC voltage, for example, the supply voltage of the circuit arrangement 23. The controller 24 comprises or has associated means for causing the switching of the controllable switch from the first position to the second position, in order to discharge the holding capacitor in proportion to the capacitance value associated with the corresponding J electrode or the set of J electrodes connected in common. In addition, controller 24 has the means to determine the voltage at the IN input when the controllable switch is in its second position, this voltage being indicative of the capacitance associated with electrode J or the set of electrodes J. Controller 24 has, then, means of comparison or control, to compare the determined voltage present at the IN input with at least one corresponding reference value or threshold, and thus deducting the possibility that the liquid is facing or not facing the J electrode or, otherwise, at least one of the electrodes in the set of electrodes J connected in common.
[000109] In a preferred mode, the scanning or sampling of the IN inputs is obtained with the use of a sampling and retention circuit associated with an analog to digital converter, and the capacitance measurement of each J electrode or set of J electrodes is performed as a comparison of the measurement made with the intrinsic capacitance of the circuit.
[000110] An example of operation of a sensor according to the configuration of Figure 20 - that is, with electrodes connected only to the respective inputs of the controller 24 - is illustrated schematically in Figure 21. It should be noted that this Figure represents, only for the sake of greater objectivity, a level sensor mounted from above, that is, in the configuration of Figure 1. However, the corresponding J electrodes are illustrated in the same order as in Figure 20 (therefore, with the J1 electrode the lowest and the upper Jn electrode).
[000111] Visible in Figure 21 is the tank 1, which has the capture part 11 of the sensor inside it, that is, the electrodes J1 to Jn, contained in the corresponding housing 16, which is immersed, at least partially, in the AdBlue liquid, indicated with L (the substrate 20 is not represented in the present context as an objectivity, and considering that - in a possible modality - it may be the casing 16 itself that performs the functions of the substrate 20). In the illustrated example, the analog IN inputs of controller 24 are connected to an MTP multiplexer implanted in the controller itself, which operates substantially as an electronic diverter, associated with which there is a sampling and retention circuit that comprises, in the present context, a capacitor of CRETENTION retention and an SS sampling switch. The sampling switch SS can be switched between a first position, connected to the VDD voltage (for example, the supply voltage of the controller 24) and a second position, connected to an output of the MTP multiplexer, that is, a position of connection to electrodes J.
[000112] In one embodiment, the control circuit layout 23 or the controller thereof 24 comprises means for connecting one or more IN inputs to earth, that is, the corresponding J electrodes, different from that connected to the sampling and retention circuit. In an implantation, a connection to the ground of all IN inputs (or J electrodes) other than the one considered each time for measurement purposes may be covered. In the example of Figure 21, for example, the MTP multiplexer is obtained in order to switch each IN input to the sampling and retention circuit each time and one or more among the other IN inputs (possibly all) to ground, as represented schematically by GM earth symbol shown with the dashed line in Figure 21. In a possible variable mode, instead of a ground connection, at least one input or the IN inputs (that is, the corresponding J electrodes) different from those considered for the purposes can be connected to a different predefined potential, that is, a different reference voltage, preferably a different potential or voltage different from the voltage at the IN input or J electrode each time considered for capacitance measurement purposes (for example , an intermediate voltage between the positive supply voltage and earth or, otherwise, a negative potential or voltage). In this perspective, the GM symbol in the Figures can also be understood as representing a connection to the potential predefined above.
[000113] Through the MTP multiplexer, the IN inputs and then the J electrodes are connected sequentially to the sampling switch SS. In the case of the modality mentioned above, when each of the IN inputs is connected by the MTP multiplexer to the SS switch, the multiplexer also connects to ground or to a predefined potential one or more among the other IN inputs, preferably at least the IN inputs corresponding to the J electrodes defined adjacent to or close to the J electrode each time connected to the sampling and retention circuit. The SS sampling switch is cyclically switched, synchronously with the MTP multiplexer operation, between the first position, of charging the CRETENTION capacitor, and the second position, connecting the capacitor itself to the IN input currently selected by the MTP multiplexer and then to the corresponding electrode J. With the SS switch in the second position, a load balance is brought between the capacitance of the CRETENTION capacitor and the capacitance associated with electrode J considered who, in the present context, is assumed to be electrode J1. In other words, with this load balance, the CRETENTION capacitor is discharged in proportion to the capacitance of the "virtual capacitor" defined by electrode J1. By means of the ADC, the amount of charge or, otherwise, a residual voltage of the CRETENTION capacitor is then determined and then compared to a predefined reference value or threshold in order to deduce the possibility of electrode J whether or not it is facing liquid L, that is, the possibility that the electrode J assumed the first structure or capacitive configuration or the second structure or capacitive configuration indicated above.
[000114] As explained earlier, when an electrode J faces the liquid L (for example, electrode J1 in Figure 21) associated with it is a first capacitance value, whereas in the opposite case (as for electrode Jn or Jn-1 of Figure 21) associated with it is a second capacitance value, different from the first value. In Figure 21, the block represented by a dashed line indicated with VE is understood as schematically representative of the function of the "virtual" electrode or plate obtained by liquid L, as explained above.
[000115] Following the aforementioned balance between the charges of the CRETENTION capacitor and the J1 electrode, the voltage value across the capacitor and / or at the IN1 input may substantially match or, otherwise, may be greater or less than one determined reference threshold, previously stored in controller 24. For example, in one mode, controller 24 can be programmed in such a way that the detection at an IN input of a voltage equal to the predefined threshold or greater than it is indicative of the fact that that the electrode considered is not facing the liquid L (as for the Jn electrode), whereas the detection of an IN input of a voltage below the threshold is indicative of the fact that the electrode is facing the liquid (as for electrode J1).
[000116] As can be seen, performing the described sequential sampling, controller 24 can identify the two J electrodes corresponding to the liquid / air transition in tank 1. Once the presence of the liquid / air transition has been detected, the controller can deduce the liquid level based on the fact that the electrode between the two J electrodes associated with which the voltage value is, equal to or above the threshold is the first electrode that is facing the air (or, in contrast, the electrode associated with which the voltage value is below the threshold is the last electrode facing the fluid).
[000117] For the above purpose, preferably contained in circuit 24 are the information representing the values in length (height) corresponding to the position of each electrode J or in any case the distance between electrodes J in the direction of the geometric axis X in order to be able to establish or calculate the level according to the predefined unit of measurement. The electronic components of the sensor 10 transmit or generate signals to be sent externally and / or to the electrical connector of the sensor 10, which represents the level information.
[000118] As previously explained, in possible modalities, for the purpose of detection, the MPT multiplexer cyclically connects an IN input to the sampling and retention circuit and at least some of the other IN inputs (preferably all) to the land or a given potential. This is useful for shielding electromagnetic disturbance and for improving the signal-to-noise ratio. This connection to ground or to a specific potential, in particular of some among the multiple IN inputs or J electrodes, can generate parasitic capacitances in the system, which can, however, be considered negligible in relation to the capacitance measurement of effective interest, as previously described.
[000119] On the other hand, in this case, each J electrode can also supply, together with the corresponding control electronic components and at least one other J electrode, a type of capacitive proximity sensor, which can detect the presence or absence of the medium even without direct contact with the latter. The two J electrodes come together to form the sensitive sides of a capacitor, which represent the plates of the capacitor, and the medium that separates them (in the present context, the material of the 20b portion and / or the G gel and / or the air ) represents the dielectric, which provides elevation at a substantially predefined capacitance. The presence or absence of an additional medium in the vicinity of the two J electrodes causes a substantially predefined variation or disturbance in the capacitance mentioned above that the electronic control components can detect. In such an implantation, which operates predominantly based on the field effect, there may be parasitic components towards the fluid, with an effect similar to that described with reference to Figure 21, which contributes to the detection of capacitance.
[000120] It will be noted that the operations described with reference to Figure 21 can also be obtained with different circuits, but technically equivalent, in relation to the example. For example, with each IN input of controller 24 there may be associated a respective circuit that performs the functions of the sampling and retention circuit described above, with an MTP multiplexer between the circuits mentioned above and the ADC. Another possibility is to provide each IN input with a sampling or measurement circuit that performs, for example, the sampling and retention circuit functions described above, directly in interface with an ADC. Such a case is represented, for example, schematically in Figure 22, in which the controllable switches indicated by the MS are selectively switched to connect, each time, each IN input to the corresponding sampling and retention circuit (as for input IN1) and the other IN inputs are connected to the ground or to the reference voltage mentioned above (as for the INn input) or switched in an open circuit, in which case the voltage or potential at the J electrodes and / or IN inputs may be fluctuating.
[000121] The presence of MS switches may not be necessary in these modalities in which the IN inputs other than the currently sampled input are not connected to ground.
[000122] Preferably, the electronic components of the sensor that were the subject of the invention are properly initialized and / or calibrated in the production stage, with storage of the corresponding software or program and / or at least some variables (such as, one or plus thresholds used in level detections), which, for example, depending on the physical configuration of the sensor and the system in which it is installed, in the present context, represented by tank 1.
[000123] In one embodiment, the calibration step includes a reading of all values of the J electrodes in "dry" conditions or in the air (that is, not facing the liquid) in order to define first reference thresholds and / or define an initial definition of zero displacement, namely, to compensate for parasitic capacitances due to materials, structures, thickness, etc. of the sensor and / or the system on which it is installed. This value is stored as a threshold reference for the detections as a maximum voltage threshold that can be detected by the entire CRETENTION capacitor and / or by the ADC circuit, where it is possible to subsequently vary this threshold value after the measurements made in the service life of the sensor, for example, by means of a dedicated reference electrode. This calibration threshold is preferably performed only once on the production line, however, for some applications where the tank has crucial geometries that can affect the measurement of raw J electrode data (such as very restricted volumes and presence of metal material), it is possible to use this calibration or self-calibration directly on the sensor 10 installed in order to have an ideal calibration in the real system and / or eliminate all possible noise effects due to the external environment.
[000124] The operating principle described to some extent depends on the temperature and aging of the system, if observed in an absolute manner. For this reason, in a preferred mode, controller 24 is programmed to perform a measurement of a differential type, preferably with the use, for this purpose, of at least one reference electrode. Since the temperature effect is represented by a shift in the measurement of the voltage value determined at an IN input of the controller 24, making a differential measurement between a detection electrode and a reference electrode, it is possible to either derive the measurement on the detection electrode and subtract the common mode effect present on the detection electrodes and, therefore, cancel any possible thermal and / or structural tendency produced by the change in temperature and / or by aging. The thermal trend mentioned above can also be compensated by means of a temperature sensor, for example, of the same type as the sensors indicated with 26 and 27. Thus, according to this modality, the voltage value determined, used for the comparison with the at least one reference threshold is preferably a differential value.
[000125] The reference electrode mentioned above is preferably the lowest electrode inside the tank 1 and then, with reference to the examples illustrated so far, the electrode J1. In addition, it is possible to supply even several reference electrodes (for example, the first three J electrodes that start at the bottom), which can be used to perform the differential measurement, as well as to program the controller 24 in order to select each one any of the electrodes J1 to Jn as the reference electrode to perform the differential measurement (controller 24 can, in fact, identify an electrode that is facing or not facing the liquid, due to the fact that the capacitance in both conditions is different and due to the presence of the threshold mentioned above).
[000126] In such a modality, the controller 24 scans all the electrodes J and obtains raw data of corresponding voltage for the purposes of verifying the presence of the liquid. In this step, the controller 24 calculates the difference between the raw data of each detection electrode and the raw data of the reference electrode J1, thus obtaining a relative measurement. This difference is compared to at least a minimum threshold defined at the design stage. In a possible modality, if at least one of the differences calculated between each detection electrode J2 to Jn and the reference electrode J1 is below the minimum threshold, this means that the detection electrode in question is at least partially turned towards the liquid L; otherwise, the electrode in question is in the air, that is, it is at a height greater than the level of liquid L.
[000127] In a modality - covering the connection to ground or to a voltage different from the inputs / electrodes different from that considered for the measurement purposes -, in order to detect a reference value for the measurement and / or a minimum level, an additional electrode, not shown can be provided, adjacent to J1 or, otherwise, the J1 electrode is designed to operate as a ground or reference electrode, in which case the detection of the reference value and / or level will start from adjacent electrode J2.
[000128] As already mentioned, the search for the level is substantially based on the identification, by the controller 24, of the two detection electrodes corresponding to the transition between liquid and air. The assessment is made by comparing the relative information (ie the differential measurement) with predefined thresholds for each and defined in the design stage (which can be replaced by defined thresholds and storage after the liquid test in the production stage) in order to deduce the possibility of an electrode facing the liquid or not. Following the scan, the controller can then identify two adjacent detection electrodes, one of which is facing the liquid and the other is not, that is, the position at the height of the liquid / air transition in tank 1 .
[000129] In an embodiment, by itself of the invention, the electronic circuit of sensor 10 undergoes a calibration or configuration based on the type and / or conductivity of the medium whose level must be detected, in particular, considering that, in the case of resistive means, that is, little conductive, there has also been determined a type of electrical resistance connected virtually in series to the measuring capacitor whose resistance can cause an increase in the time required to reach the final threshold value (such as an increase in time charge of the "virtual capacitor" to which a J electrode belongs and / or an increase in the discharge time of the capacitor (CRETENTION). In this perspective, the calibration mentioned above can, for example, be covered in order to consider possible delays in sampling measurement and prevent erroneous measurements on values that have not yet been fully settled.
[000130] In an embodiment, by itself of the invention, the electronic circuit of sensor 10 is configured to detect the charging curve of the "virtual capacitor" corresponding to the detection electrode J and / or to detect the discharge curve of a capacitor holding capacities, such as the CRETENTION capacitor, in which the charging curve and / or the discharge curve are / are variable at least in proportion to the characteristics of electrical conductivity and / or impedance of the medium subjected to the measurement, in order to to be able to determine the characteristics of the medium itself. The electronic circuit can use the information then acquired to perform one or more of the operations of detection, processing, comparison, storage, compensation and warning. For this purpose, structural and / or circuit elements can be used, which are at least in part similar to those described above.
[000131] As mentioned, in a particularly advantageous embodiment, the detection electrodes comprise at least first detection electrodes, which are connected to the respective IN inputs of the controller 24, and second detection electrodes, which are electrically connected in common or in pairs. parallel to the first detection electrodes, where the definition of parallel connection also refers to the parallel connection between the "virtual capacitors" defined by the J electrodes that are connected together in common with respect to a respective IN input.
[000132] An example of this type is illustrated schematically in Figure 23, in which the first electrodes mentioned above start from electrode J4 to electrode J20, while the second electrodes start from electrode J21 to electrode Jn. In this example, electrodes J1 to J3 can be reference electrodes. In the configuration of Figure 23, it is substantially possible to identify a first subarray (or module or block or set) of first electrodes, starting from electrode J4 to electrode J20 and a second subarray of second electrodes, starting from electrode J21 to electrode Jn they are substantially connected to each other in common or in parallel. The number of electrode subarrays can be increased in order to obtain longer and shorter level sensors, that is, in order to allow different level measurements.
[000133] In such a modality, the control means or comparators mentioned above implanted in controller 24 are predisposed to compare the voltage determined at the IN input corresponding to two electrodes connected in common (for example, electrodes J4 and J21 in parallel) with at least two corresponding reference thresholds in order to deduce the possibility of the liquid being turned or not facing the first detection electrode (the J4 electrode) and / or the corresponding second detection electrode (the J21 electrode). The measurement can be done according to the modalities described previously. Preferably, also in this case, the measurement is made by obtaining the raw data at the IN input to which the two detection electrodes connected in common are connected, and then reference this value in relation to a reference electrode, such as the J1 electrode, in order to pass from an absolute measurement to a differential measurement in order to eliminate the common error effect possible due to the temperature and / or aging of the level sensor, as previously described.
[000134] In one embodiment, the value obtained from the differential measurement is compared to the number of thresholds equal to the number of several electrodes connected in common increase by 1. Consequently, with reference to the example described considered in the present context of two J electrodes in parallel, the differential value is compared to three different thresholds in the design and production stages: a value equal to or within the first threshold (for example, +/- 40%) indicates that both electrodes are not facing the liquid, a value equal to or within a certain threshold (for example, +/- 40%) indicates that one of the electrodes (known based on its physical position) is facing the liquid and the other electrode is not and, finally, a value equal to a third threshold or within a certain proximity to it (for example, +/- 40%) indicates that both electrodes are facing the fluid.
[000135] In a different mode, a more simplified analysis logic is provided, by means of which the value obtained from the differential measurement is compared to a number of thresholds equal to the number of electrodes connected in common. Consequently, with reference again to the example considered in the present context of two J electrodes in parallel, the differential value is compared to two thresholds: a value above a first threshold indicates that both electrodes are not facing the liquid, a value between two thresholds indicates that one of the electrodes (known based on its physical position) is facing the liquid and the other electrode is not and, finally, a value below the second threshold indicates that both electrodes are facing the fluid .
[000136] Evidently, based on the same principle described above, more than two electrodes connected in common can be covered, that is, several subarrays with respective electrodes in parallel, in this case the number of reference thresholds for each IN input will be equal to number of electrodes of each parallel increased by 1 or, otherwise, equal to the number of electrodes of each parallel, according to the analysis approach implemented.
[000137] For example, Figure 24 illustrates the case of the first, second and third detection electrodes connected in common or in parallel. The first electrodes start from electrode J4 to electrode J20, the second electrodes start from electrode J21 to electrode J37 and the third electrodes start from electrode J38 to electrode Jn. In this example, electrodes J1 to J3 can be reference electrodes. In the example in Figure 24, it is, therefore, possible to identify three electrode subarrays or "virtual capacitors", with the electrodes of a subarray (J4 to J20) that are connected substantially in common or in parallel with similar electrodes of the other subarrays (J21 to J37 and J38 to Jn).
[000138] In such a modality, the control means or comparators implanted in the controller 24 are predisposed to compare the voltage determined at the IN input corresponding to three electrodes in parallel (for example, the electrodes J4, J21 and J37) with three thresholds corresponding reference points in order to deduce the possibility of the liquid being turned or not towards the first detection electrode (the J4 electrode) and / or the corresponding second detection electrode (the J21 electrode) and / or the third detection electrode ( electrode J37). An example of operation of an arrangement of the type illustrated in Figure 24 is hereinafter described with reference to Figures 25 and 26.
[000139] Figure 25 is a schematic representation similar to that of Figure 21, in which only the IN4 and INn inputs of controller 24 are highlighted (the representation of the reference electrode J1 is, in the present context, omitted for the sake of objectivity). As for the case of Figure 21, controller 24 performs sequential sampling of the analog inputs of the same IN, with corresponding differential measurement for each one of them and corresponding comparison with three predefined thresholds for J electrodes that are facing liquid L and / or with the predefined thresholds for "dry" J electrodes, that is, those that are not directed towards liquid L. In addition, in this case, the control circuit arrangement may comprise means (MS and / or GM and / or MTP ) to connect to ground or to a different predefined potential one or more IN inputs different from the one connected each time to the sampling and retention circuit.
[000140] Figure 26 exemplifies, in graphical and schematic form, the measurement principle adopted for the various IN inputs, for example, the IN4 input. Assuming that the initial 5 V voltage shown in the graph corresponding to the VDD voltage in Figure 25. TH1, TH2 and TH3 are three predefined threshold values for input IN4, that is, a maximum threshold, a minimum threshold and a threshold intermediate, respectively, for the condition of electrodes that are facing the liquid.
[000141] The graph in part a) of Figure 26 expresses the condition that arises in the case where none of these three electrodes J4, J21 and J38 are facing the fluid, after the commutation of the SS switch of Figure 25 in the position of the same in which the CRETENTION capacitor is connected to the corresponding set of detection electrodes J4, J21 and J38. In the Figure, a falling edge of the voltage represents the decrease in the voltage value due to the differential measurement made with the modalities described above and / or the fact that, even if they are not turned towards liquid L, associated with the three electrodes in question there is, in any case, still a minimum capacitance, due to the structure of the device. The voltage drop that appears in the graph in part a) of Figure 26 can also be verified in relation to a "dry" threshold value, indicated with THD, greater than the minimum TH3 threshold value, and it is possible to use this value of THD threshold also for the purpose of discrimination in relation to the three detection thresholds TH1, TH2 and TH3. The voltage drop in graph a) remains within the determined proximity (for example, the + / 40% mentioned above) of the THD threshold and, in any case, above the TH3 threshold. Controller 24 then deduces the absence of liquid in front of electrodes J4, J21 and J38.
[000142] The graph in part b) of Figure 26 preferably expresses the condition that arises in the case where one of the electrodes J4, J21, and J38 is directed towards liquid L. In this case, the reduction in the value of tension is higher than in the previous case. In addition to the differential measurement, in fact, the general capacitance associated with the three electrodes is greater than in the previous case, since one of them is facing the liquid L. The voltage value is within the determined proximity of the TH3 threshold and, starting In addition, controller 24 deduces the presence of liquid in front of only one of the electrodes, that is, the lowest electrode among the three (where the physical position of the electrodes is known by the controller).
[000143] The graph in part c) of Figure 26 preferably expresses the condition corresponding to that of Figure 25, that is, the condition in which two of the electrodes J4, J21 and J38 are facing liquid L. The decrease in voltage, it is now greater than the case of part b) of Figure 23 since, in addition to the differential measurement, in the condition in question, the general capacitance associated with the three electrodes is increased additionally in relation to the previous case. The voltage value is now in the determined proximity to the TH2 threshold. Controller 24 then deduces the presence of liquid in front of electrodes J20 and J37 and the absence of liquid in front of the remaining electrode Jn, that is, the largest electrode above among the three. This discrimination is also considered considering that, in the chaos of the conditions of freezing or partial solidification of the liquid, it is possible to combine other detections in order to better discriminate this condition, such as a check and comparison to the state of adjacent electrodes and / or a temperature. Finally, the graph in part d) of Figure 26 expresses the condition in which all three electrodes J4, J21 and J38 are facing liquid L. The decrease in voltage is evidently greater than in the case of part c) of Figure 23 since, in addition to the differential measurement, in the condition in question, the general capacitance associated with the three electrodes is maximum. The voltage value is now in the determined proximity to the TH1 threshold, so controller 24 deduces the presence of liquid in front of the three electrodes J21 and J38.
[000144] As previously explained, the same findings can be obtained using a simplified logic, that is, comparing the voltage value with only the three detection thresholds TH1, TH2 and TH3, as follows:
[000145] - part a) of Figure 26: with the voltage value that remains above the TH3 threshold, controller 24 deduces the absence of liquid in front of electrodes J4, J21 and J38;
[000146] - part b) of Figure 26: with the voltage value between the TH3 threshold and the TH2 threshold, the controller 24 deduces the presence of liquid in front of the lowest electrode among the three;
[000147] - part c) of Figure 26: with the voltage value between the TH2 threshold and the TH1 threshold, controller 24 deduces the presence of liquid in front of electrodes J20 and J37 and the absence of liquid in front the remaining electrode Jn; and
[000148] - part d) of Figure 26: with the voltage value that falls below the TH1 threshold, controller 24 deduces the presence of liquid in front of the three electrodes J21 and J38.
[000149] By scanning the IN inputs with any one of the modalities exemplified above, controller 24 can identify the liquid / air transition. Then, in the case specified in Figure 25, controller 24 can deduce the presence of a liquid / air transition between electrodes J37 and J38, thereby identifying the level of liquid in tank 1.
[000150] From what has been described above, it can be readily understood how the type of proposed modality is extremely flexible in relation to the possible lengths required for the level sensor. In other words, with a given controller 24 and with substantially the same number of analog IN inputs (or with a slightly larger number of IN inputs, as described below), it is possible to provide level sensors of different lengths, which includes for the detecting the use of J electrodes in a single configuration, or otherwise two J electrodes in parallel or otherwise again three J electrodes in parallel and so on.
[000151] For example, by placing twenty J electrodes in a single configuration, which are 2 mm high and defined at a distance of 2 mm, it is possible to cover a sensitive area for the level measurement of 78 mm ( 20 electrodes + 19 spaces between them) x 2 mm). When it is necessary to increase the length of the sensitive area (the measurement of higher levels) while maintaining the same measurement resolution, it is possible to use two electrodes in parallel, or three, even while maintaining the same controller 24.
[000152] Preferably, in the presence of the first detection electrodes connected in common with additional detection electrodes, it is preferable that the physical position of the various electrode subsets be as far apart as possible from each other in order to increase the signal difference and, therefore, the quality of the level information. For this reason, in a preferred mode, if numerous sets of detection electrodes connected in common are provided, with the electrodes of each set forming respective subarrays arranged in sequence along the sensor's geometric detection axis, as can be seen, for example, from Figures 23 and 24. In general, with reference to, for example, Figure 24, the rule can be applied through which, given a number y (for example, 17) of the first electrodes (J4-J20) in parallel with the second electrodes (J21-J37), defined between each first electrode and the second corresponding electrode, there will be y-1 (in the example, 16) electrodes.
[000153] Due to the type of modality described, it is also possible to have different sensitivities for level detection. This can be achieved in the production stage of part 20a of the substrate with the corresponding electrodes J by positioning the electrodes themselves with a distance from center to center equal to the desired resolution. It is also possible to imagine at least two different measurement resolutions in the sensitive portion 20b of the sensor, in particular, at least one measurement with higher resolution and one measurement with lower resolution, in a lower area and in an upper area of the 20b portion, or vice versa -version. In such a case, the electrodes in the lower area of the portion 20b may be closer to each other than the electrodes present in the upper area, or vice versa. The minimum distance between two electrodes can, for example, be 1 mm. So, it is evident that the dimensions of the electrodes define the level of capacitance that can be measured by the control electronics so that a higher level electrode will offer a higher dynamics or measured value.
[000154] J electrodes are preferably (but not necessarily) equal to each other and can, for example, be obtained with dimensions of 20 mm (length) x 2 mm (height) and defined at a distance of 2 mm apart . For level sensors that have a length of less than 100 mm - or in the case where they intend to increase the resolution in an area of the sensitive portion of the sensor - it is possible to reduce the dimensions of the electrodes and, therefore, also reduce the distance between them, precisely to obtain a measurement with higher resolution. In such cases, the electrodes can, for example, have dimensions of 15 mm (length) x 1 mm (height) and be defined at a distance of 1 mm of separation. In order to maximize the measurement dynamics for the liquid, for example, for the AdBlue liquid in the present context considered (or another solution with urea or different reducing agent), it is also preferable to dimension the electrodes, to any value of their length, so that the height of an electrode is equal to the distance between two contiguous electrodes. Preferably, the spacing between two contiguous electrodes J will be greater than twice the thickness of the wall that separates them from the medium 12.
[000155] Figures 27 and 28 illustrate, with views similar to that of Figure 24, additionally possible arrangements that provide sets of J electrodes in parallel. In the case of Figure 27, the two end electrodes of the illustrated arrangement, namely, the electrodes J1 and Jn, are not connected in parallel with other electrodes and constitute reference electrodes for the condition of presence and absence of liquid, respectively, or vice versa, whose function is preferably programmable or predeterminable, for example, in order to allow the installation of sensor 10 in tank 1 in the two conditions of Figures 1 and 2.
[000156] Figure 27 illustrates a configuration, partly similar to that of Figure 24, in which the electrode array includes three sub-arrays of the first, second and third detection electrodes connected in common one (that is, in parallel with) with the another, the subarrays being separated, however, by individual electrodes. The first electrodes range from electrode J2 to electrode J17, the second electrodes range from electrode J19 to electrode J34, and the third electrodes range from electrode J36 to electrode J51. In this example, the intermediate electrodes J18 and J35 are, instead, independent and defined between the three electrode subarrays mentioned above. In particular, the single J18 electrode is defined between the first sub-array (J2-J17) and the second sub-array (J19-J34), while the single J35 electrode is defined between the second aforementioned sub-array and the third sub-array (J36-J51) .
[000157] The intermediate electrodes J18 and J35 allow a clearer distinction between the subarrays of electrodes connected in common, in particular in order to detect particular conditions or states of the liquid or other medium that is subjected to measurement (such as a solidification state or partial freezing of the liquid or medium), in particular a more precise and / or clear distinction in detecting "liquid - air / gas" and / or "liquid - air / gas - solid / ice" transitions. For this purpose, it must be considered that the electrodes defined between J18 and J35 enable faster determination of which and / or how many subarrays or parts of it are facing (or not) towards the medium, therefore, it is possible to identify the areas more quickly. of uncertainty in which they perform more accurate measurements, that is, by detecting the transition areas between two adjacent electrodes in order to detect, for example, the transition area from liquid to air, as previously mentioned.
[000158] The presence of independent intermediate electrodes is also useful in order to better discriminate the values in relation to the previously mentioned reference thresholds (such as TH1, TH2, TH3 and / or the "dry" threshold), in particular, in the case a large number of electrode sub-arrays in common (or in parallel): in the case of many sub-arrays, there will, in fact, be many defined reference thresholds close together; for example, in the case where it is preferable, for reasons of cost, to use an ADC with a lower resolution (for example, 8 bits instead of 10 or 12 bits), the presence of the previously mentioned independent electrode J18, J35 making it possible a detection that is clearer and / or more certain, similar to what has been described with reference to graph b) of Figure 26, in which only the TH3 threshold is considered.
[000159] Figure 28 is substantially similar to Figure 27, differing only due to the fact that the intermediate electrodes J18 and J35 are not in a single configuration, but are connected together in parallel and connected to one and the same IN input. Such a configuration can be useful to limit the number of connections to the supplied intermediate electrodes, although a good distinction between two thresholds (namely, TH1 and TH2 thresholds) associated with one and the same IN input is ensured.
[000160] With reference to the configurations described by way of example in Figures 27 and 28, and considering a larger number of subarrays or sets of electrodes connected in common (for example, five or more subarrays), a number of intermediate electrodes can be supplied, connected in a single configuration or connected in pairs in parallel to each other.
[000161] Figure 29 illustrates some circuit components used in a possible practical implementation of the invention. Part a) of the Figure highlights the microcontroller 24 used, in the present context the PIC16F1517 previously mentioned manufactured by Microchip Technology Inc., with an indication of the corresponding inputs and outputs. Part b) of the Figure highlights the electrodes J, which in the present context comprise electrodes J1-J17 connected in a single configuration to the respective microcontroller inputs 24, as well as electrodes J18- J27 connected to the respective microcontroller inputs 24 in common or in parallel with electrodes J28-J37. It can be seen that, in the connection between each of the electrodes J1-J27 and the corresponding input of the microcontroller 24, the filter resistance mentioned above, which can possibly be omitted. Part c) of Figure 29 illustrates a possible circuit diagram of a temperature sensor that can be used in the device according to the invention, such as, for example, the temperature sensor 26 and / or 27 in Figure 7. Finally , part d) of the Figure illustrates a possible communication port or electrical connector that belongs to the circuit arrangement 23 of Figure 7, which can be used, for example, for programming and / or calibrating the level sensor in the production stage. Of course, the circuit arrangement 23 also includes a power supply stage, not shown, as long as it can be obtained according to techniques known per se.
[000162] Thanks to its nature consisting of different detection elements, the sensor according to the invention has the capacity to perform level measurements in a wide range of situations, which arise, for example, in SCR systems. A first situation is the typical case, already described above, in which the liquid contained in the tank is entirely in the fluid state. A second situation can arise in the case where the tank operates in low temperature conditions, in order to cause total freezing of the liquid present in the tank. In this case too, sensor 10 is perfectly capable of recognizing the electrodes facing the mass of ice and, therefore, calculating its height. A third situation is one in which the tank contains a predominant liquid part, which floats or is immersed in parts of ice ("iceberg effect"): also in this case, the level measurement performed by sensor 10 can occur with the modalities already described above, as long as the presence of pieces of ice does not affect the operation of sensor 10 and level calculation. Similar considerations apply to the case where there is a direct transition between liquid and ice.
[000163] The sensor 10 is also capable of detecting in mixed situations, when the liquid-ice system is freezing or thawing. Such a case is illustrated schematically in Figure 30, in which at the top of the tank 1 liquid ice is present, indicated with I, to form a partial or total cap. At the bottom of tank 1, at a higher temperature, the L contents of the tank are already in a liquid state and present between the solid part I and the liquid part L is air, indicated with A, or vacuum. Such a condition can, for example, arise in the case of the use of liquid L contained in the tank before it is completely frozen or after partial thawing of the contents of the tank that was obtained by means of a heater: in such a case, the part of used liquid substantially corresponds to an intermediate area that is empty or with air between the liquid and the ice. According to an aspect of the invention, in such a condition, it is advantageous to detect the level of the liquid in order to prevent its complete use, that is, in order to leave at least part of the liquid in the tank, for the reasons explained henceforth.
[000164] Also in a condition of the type exemplified, the control electronics of sensor 10 has the capacity to correctly identify the presence of one or more electrodes (J4, J20) facing liquid L, followed by the presence of one or more electrodes ( J21, J37) facing the air A, in turn followed by one or more electrodes (J38, Jn) facing the ice I. Advantageously, in such a situation, the sensor control electronics according to the invention has ability to define both the amount / level of liquid content L, which is important since it is the part that can be directly used at the moment by the SCR system, and the total amount of liquid (L + I) present in the tank, which is important to plan to complete the tank level 1. A possible control logic that can be used to detect the so-called "igloo effect" (presence of an air layer overlaid by an ice layer) can be as follows:
[000165] - all detection electrodes that are in the "dry" condition, that is, facing the air, are considered alone;
[000166] - the acquired information is evaluated on a certain number of electrodes (for example, three) subsequent to a considered "dry" electrode (where by "subsequent" electrodes it is intended to mean the electrodes above the "dry" electrode considered, in the case of installing the sensor from below, or below the "dry" electrode considered, in the case of installing the sensor from above);
[000167] - a check is made to verify that above an "dry" electrode an electrode - among the subsequent electrodes mentioned above - is present that is facing the liquid; for this purpose, in a preferred mode, the difference is computed between the measurements made on the subsequent electrodes mentioned above and the measurement made on the "dry" electrode considered, and the three individual results are compared with absolute thresholds defined at the design stage; if at least one of these differences coincides or is in the certain vicinity of the defined threshold, the presence of the "igloo effect" is detected.
[000168] It is also possible that, starting from a situation of the type shown in Figure 27, the tank is completely filled, which introduces a part of liquid L, which, however, can be blocked by the ice cap I still present in tank 1. Based on the principles established above, also in this case the sensor according to the invention evidently has the capacity to detect the increase in the total level of liquid present in tank 1. Again with reference to situations of the type represented in Figure 27, it will be noted that, if necessary, the electronics of sensor 10 can be programmed to perform successive detections, separated from each other for a certain period of time (for example, 2 minutes), in order to detect progressive evolution of the ice cap I defrost.
[000169] As already mentioned, the sensor electronics that form the subject of the invention are initialized and calibrated in the production stage, with the storage of the corresponding software and the corresponding variables, within one or more of the reference thresholds that depend on the physical configuration. of the tank sensor system, among the minimum thresholds that represent the condition of an electrode or a set of electrodes that is not facing the fluid. The minimum threshold for the opposite case (liquid facing an electrode) can be predefined after experiments and / or it can be defined by means of an additional test with the capture part 11 of the sensor completely immersed in the liquid. In the case where the sensor 10 provides electrodes in parallel, the intermediate thresholds between the minimum threshold and the maximum threshold are also then defined experimentally.
[000170] The temperature information that can be acquired by means of sensor 27 and / or 26 can be used by electronics 23 to recognize the situation of the tank system, for example, in order to deduce the freezing condition of the liquid and activate a corresponding heater, and / or in order to mathematically compensate the information on the level measurement, in particular in the case of applications in critical temperatures where the use of a differential measurement with the reference electrode may not be sufficient to guarantee compensation of error.
[000171] It is emphasized that, in order to be able to cause certain ice liquids to thaw through a heater, such as the AdBlue additive considered in this document, it is necessary to have a portion of thawed liquid present in the tank in any case. so that the heater can continue to heat the liquid and this transmits heat to the ice mass. When applying to an SCR system, when the vehicle engine is started, the additive is extracted, and this is not a source of particular problems as long as there is still a certain amount of heated additive in the tank, which can reach mass of ice as a result of the movement of the vehicle and the consequent mixing of the liquid in the tank 1. If, instead, the initial extraction of the additive causes emptying of the entire liquid residue contained in the tank, the melting effect stops. For this reason, in a preferred embodiment, the sensor according to the invention can be predisposed, for example, in a software level, to detect the level of the melted liquid so as to guarantee in any case the presence of a minimum level of the even enough for the melting effect not to be interrupted. For this purpose, sensor 10 can generate an appropriate signal or data for the outside world, which can, for example, be used by electronics on board the vehicle and / or to issue appropriate warnings.
[000172] It will be seen, of course, that with the sensor forming the material of the invention, progressive melting of the liquid ice mass can also be readily detected as the melting proceeds. Evidently, the sensor 10 is capable of operating during the heating and / or thawing of the liquid or other medium, the level of which must be measured, as well as in the course of its possible freezing.
[000173] The sensor 10 interfaces with an external control system, such as a control unit of the SCR system, through connector 12b. For this purpose, the control electronics 23 of the sensor is predisposed for data transmission, preferably in a serial format, more preferably, with the use of an interface and / or SENT protocol (Single Edge Nibble Transmission) ). The signals sent may comprise, in addition to the information that represents the level of the medium being measured, also information that represents at least one of the temperature of the medium or air present in the tank, the presence of a condition of freezing or solidification of at least part of the medium that is subjected to the measurement, the presence of an abnormal operation condition, a warning and / or status sign.
[000174] From what has been previously described, it can be seen how the operation of the level sensor described is substantially independent of the dielectric constant of the medium subjected to the measurement. The sensitive element represented by the electrode array has the capacity to perform the level measurement even if it is completely isolated from the liquid, which guarantees its protection against contact with aggressive liquids, such as AdBlue or urea, which provides good mechanical strength in the sensor frame. In this perspective, the wall thickness of the housing 16, in particular in the area facing the electrodes J, can be comprised between 0.1 and 5 mm, preferably between 0.6 and 1 mm, more preferably, approximately 0 , 8 mm. As already mentioned, the enclosure can be replaced by a direct overmoulding of plastic material on the sensitive element, or by a generic wall for insulating the J electrodes, with a thickness like the one indicated above.
[000175] The sensor described can be of any length and is therefore readily adaptable to the interior of any container. A problem present in the application of level sensors is precisely represented by the length of the sensor, that is, the height of the level that must be measured, which is a variable that depends on the tank in which the sensor is installed. In this context, the invention makes it possible to:
[000176] - use of standardized electronics, that is, as few components as possible, with a microcontroller that, given the same or practically the same number of inputs, can handle a wide range of lengths thanks to the possible connection in common or parallel of a number of electrode subsets; and
[000177] - use of a highly flexible circuit diagram for the various possible lengths required for the sensor, that is, use of one and the same microcontroller with the same number of inputs also for level sensors of different lengths.
[000178] As already mentioned, by placing, for example, 20 electrodes that have a height of 2 mm at a distance of 2 mm separation, a sensitive area for level measurement that has a length of 78 mm is obtained, that is, a sensitive area that is 78 mm long for a set of first electrodes. When it is necessary to increase the length of the sensitive area, it is possible to use the same number of inputs by providing second electrodes in parallel with the first. In this way, it is possible to maintain the same microcontroller, both in terms of cost and in terms of design. As a non-limiting example, with ten electrode subsets in theory it is possible to reach lengths close to 780 mm. For lengths of this type, it is possible, on the other hand, to reduce the number of electrode subarrays, in the case where a lower measurement sensitivity or resolution is acceptable at least in some parts or for some levels of the sensor. For this purpose, as already mentioned, it is possible, for example, to increase the distance between the electrodes in the areas where the measurement accuracy is less significant (such as a level close to the full tank level) and to reduce, instead, the distance to obtain a higher resolution in areas considered more critical (for example, in proximity to a minimum level in the tank).
[000179] In several modalities previously described, the installation of sensor 10 on the bottom wall of the tank was assumed, so that the electrode indicated with J1 represents the electrode defined further down in the tank itself. Obviously, as explained, the installation of the sensor can also be done on the upper wall of the tank, in which case - with reference to the illustrated examples - the electrode Ji is the closest to the distal end of the 20b portion of the substrate 20, and the electrode Jn it is closest to the proximal end of portion 20b. Of course, the control software will be predisposed to enable level detection according to the point at which the sensor is installed, for an additional advantage in the flexibility of use.
[000180] From the description above, the characteristics of the present invention emerge clearly, as well as its advantages, mainly represented by the simplicity of production of the proposed level sensor, by its contained cost, by its precision and reliability, and by its high flexibility of use and configuration.
[000181] It is evident that numerous variations can be made in the devices and methods described by way of example by the person skilled in the art, without departing from the scope of the invention as defined by the appended claims.
[000182] According to possible variations of the implantation or application, the level sensor that forms the material of the invention can be disposed outside the container or tank that contains the medium that is subjected to the measurement (that is, on a wall or on a seat made on the outer wall of the container or tank), with the electrode arrangement J fitted against a wall of the container, with possible interposition of the G gel or similar. In this case, the wall said above the container is appropriately configured in terms of material and thickness in order to provide the layer that electrically insulates the electrodes J in relation to the interior of the container 1. A possible example of the modality is illustrated in Figure 31, in that the housing of the sensor body 10 is in the present context a housing 16 'opened laterally, so that the front of the substrate portion 20b and, therefore, the electrodes J, turn / or are adjusted against a respective portion 16 "of a side wall 6 of tank 1. In the example, that portion 16 ", which in the present context provides the insulating layer that electrically isolates electrodes J from the inside of tank 1, is tuned in relation to the rest of wall 6, for example, with a thickness between 0.1 and 5 mm mentioned above.
[000183] According to other variant modalities, the enclosure 16 and at least part of the corresponding characteristics described above could be comprised in at least an integrated part or associated with the container or tank. As already mentioned, the electrodes could be associated directly with a wall or wall portion of the tank (for example, the 16 "portion of Figure 31), which in this case would constitute both the substrate for the J electrodes and the insulating layer in relation to to the contents of the tank.
[000184] As previously mentioned, the capacitance measurements required for implantation of the invention can be performed - directly or indirectly - also with sampling or measurement circuits different from those exemplified in Figures 21, 22, 25 and 30, even in absence of means to connect the IN inputs other than the one connected each time to the sampling or measurement circuit to ground or to a reference voltage, such as, for example, circuits designed to convert the input capacitance into an equivalent resistance. For such cases, for example, a modulator (in particular, of a sigmadelta type) can be used to convert the current measured by means of the equivalent resistance into a digital count. When the medium L turns to an electrode J, the capacitance increases and the equivalent resistance decreases. This causes a variation (typically, an increase) in the current through the resistance, with a consequent variation (typically, an increase) in the digital count, which can be considered as representative of the presence of the medium in front of the electrode. In addition, in implantations of this type, the count value determined each time at the considered IN input can be compared to one or more reference thresholds and / or can be a differential value in relation to one or more reference electrodes, with a similar approach to that described above in relation to capacitance measurements based on voltage values.
[000185] An example in this sense is illustrated schematically in Figure 32, in which the block indicated with CJ must represent the capacitance associated with electrode J or the set of electrodes J that undergo each measurement each time. In this example, a CP sampling circuit is provided, where the CJ capacitance (for example, a J electrode or a set of J electrodes) provides, next to the switches S1 and S2, a switched capacitor circuit. The two switches are controlled by means of two clocks or timing circuits complementary to each other, not shown. Thus, when switch S1 is closed, capacitance CJ is charged by voltage V, with the charge in CJ which is, therefore, Q = CJV. When S2 is closed and S1 is opened, the change is removed from the CJ. If the switching frequency of switches S1 and S2 is Fs, the charge Q = CJV is transferred at the rate Fs: consequently, the charge transfer rate per unit of time (current) is ICS = qFs = CJFsV.
[000186] The equation indicates that the ICS current, which the switched capacitor circuit draws from the Mux analog bus, is directly proportional to the CJ capacitance. The IDAC converter supplies the Mux analog bus with a constant current whenever the Q output of the bistable multivibrator D is high and does not supply the current instead when the Q output of the bistable multivibrator D is low. The Q output of the bistable multivibrator D is basically the output of the CMP comparator, synchronized with a CL time trial. The ICM current that a CMOD reference capacitor draws from the Mux analog bus is the difference between the current supplied by the IDAC converter and the current drawn by the switched capacitor circuit. The voltage V across the capacitance CJ is connected to the inversion input (-) of the CMP comparator, whereas the non-inversion input (+) is connected to a reference voltage VREF.
[000187] When the CJ capacitance increases (due to the presence of the L medium in front of a J electrode), the ICS current increases proportionally. The output of the CMP comparator is a PWM signal and its duty cycle is proportional to the CJ value. The duty cycle measured by means of a suitable counter: since, as explained, the capacitance of the J electrodes - and, therefore, the CJ capacitance - is affected by the presence or, otherwise, of the L medium, it is possible deduce from the count mentioned above which electrode or electrodes J are facing the L medium and which are not. In addition, in this case, the count value determined each time at the considered IN input (possibly a differential value in relation to one or more reference electrodes) is compared by the control means or comparators of the controller 24 with one or more thresholds of reference, with an approach similar to that described above in relation to capacitance measurements based on voltage values. In addition, in a modality of the type illustrated in Figure 32, there may possibly be ways to connect different inputs / electrodes to ground or to a different potential than those considered each time for the purposes of level detection.
[000188] Just as an example, the microcontrollers commercially available for the application exemplified with reference to Figure 32 can be those identified by the codes CY8C24894-24LFXA and CY8C4245AXI, marketed with Cypress Semiconductor Corporation, San Jose, CA, USA
[000189] Figure 32 illustrates the case of electrode sets (J4, J21, J38 and J20, J37, Jn) connected together in common, however, the type of implantation described in this Figure can also be used with a configuration in which the The capacitive elements of the level sensor each comprise a single electrode, similarly to what has been described with reference to Figure 21. Furthermore, in this case, the presence of the GM means can be contemplated or not.
[000190] In a variant, the sensor control logic can be predisposed to perform a first capacitance measurement at the single IN input (and, therefore, on a single electrode or a set of electrodes in common), without connecting to ground or to a reference voltage the other IN inputs and then a second measurement in which also the IN inputs other than the one that is currently sampled are also connected to the ground or to the reference voltage mentioned above, in order to combine two detection techniques for the purposes of increased detection security.
[000191] The invention has been described with particular reference to the detection of the level of a liquid medium, in particular, a urea-based additive, however, as already mentioned, the described sensor can be used in combination with different substances and materials, up to potentially subjected to solidification for reasons other than freezing (for example, a mass of a powdery or similar material of which a part is compacted and solidified, for example, due to excessive moisture).

权利要求:
Claims (18)
[0001]
1. Sensor to detect the level of a medium contained in a container (1), the sensor (10) comprises: an arrangement of capacitive elements designed to be associated with the container (1), in order to extend according to an axis geometric detection (X) of the middle level (L), with the arrangement of capacitive elements comprising a plurality of electrodes (J1 to Jn), on one side of an electrically insulating substrate (20) that has a generally elongated shape, being that the electrodes (J1 to Jn) are separated from each other, along the geometric axis of detection (X) and are substantially coplanar with each other; at least one insulating layer (16; 16 ") to electrically insulate the electrodes (J1 to Jn) from the inside of the container (1); and a controller (24) that has a plurality of inputs (IN1-INn), where the controller (24) comprises or has an associated circuit for measuring capacitance (SS, CRETENTION; CP), where each capacitive element comprises at least one of a single electrode (J) and a set of electrodes connected together in parallel ( J4, J21, J38; J20, J37, Jn), the single electrode (J) or the set of electrodes (J4, J21, J38; J20, J37, Jn) being connected to a respective input (IN) of the plurality of inputs (IN1 to INn), where the controller (24) is predisposed to discriminate a capacitance value associated with each electrode (J1-Jn) to deduce the level of the medium (L) present in the container (1), in which the controller (24) is operable to detect a capacitance value in each of the inputs in the plurality of inputs (IN1-INn) indirectly, based on in a voltage measurement or by converting an input capacitance into an equivalent resistance and then converting the measured current through the equivalent resistance into a digital count, where the controller (24) understands or has associated at least one among: - a multiplexer circuit predisposed to selectively connect each input (IN) of the plurality of inputs (IN1 to INn) to the circuit for measuring capacitance (SS, CRETENTION; CP); - a reference circuit for connecting to ground or to a reference voltage one or more of the inputs of the plurality of inputs (IN1 to INn) different from the input (IN) connected each time to the circuit to measure capacitance (SS, CRETENTION; CP ); and - a sampling or measurement circuit (CP) operatively connected to each input (IN) of the plurality of inputs (IN1 to INn), configured to convert an input capacitance to an equivalent resistance and to convert a current measured by means of the equivalent resistance in a digital count that represents the input capacitance value, characterized by the fact that: - the controller (24) understands or has an associated control circuit, to compare a digital count determined in said input (IN) , or a voltage determined at said input (IN), with at least one corresponding threshold or reference value (THD, TH1, TH2, TH3) in order to deduce whether or not the medium is facing the single electrode (J) or an electrode from the set of electrodes (J4, J21, J38, J20, J37, Jn), - the digital count determined at said input (IN) or the voltage determined at said input (IN) is a differential digital count or a differential voltage , respectively, the controller (24) being predisposed to compute the difference between a digital count value or voltage corresponding to said input (IN) and a digital count value or voltage corresponding to an input (N) of the plurality of inputs (IN1-INn) which is connected to at least one reference electrode (J1) - the control circuit is predisposed to compare the value of the differential digital count or voltage with at least one threshold or reference value (THD, TH1, TH2, TH3).
[0002]
2. Level sensor, according to claim 1, characterized by the fact that each electrode (J1 to Jn) can provide at least: - a first configuration or capacitive structure that has a first capacitance value when the electrode (J1 a Jn) is facing the medium (L) or when the level of the medium (L) in the container (1) corresponds to the electrode (J1 to Jn) or is above it; and - a second configuration or capacitive structure that has a second capacitance value when the electrode (J1 to Jn) is not facing the medium (L) or when the level of the medium (L) in the container (1) is below the electrode (J1-Jn).
[0003]
3. Level sensor, according to claim 1, characterized by the fact that the controller (24) is predisposed to discriminate a capacitance value associated with each electrode (J1 to Jn) between at least a first capacitance value and a second capacitance value in order to identify a transition between the medium and the air or gas in the container (1) which is representative of the medium level (L).
[0004]
4. Level sensor, according to claim 1, characterized by the fact that: the circuit for measuring capacitance (SS, CRETENTION; CP) comprises a sampling circuit (SS, CRETENTION) connected in an operational way or capable of being connected to each input (IN) among the plurality of inputs (IN1 to INn) that includes a controllable switch (SS) and a capacitor (CRETENTION), with the controllable switch (SS) being switchable between a first position, where the capacitor ( CRE-TENTION) is connected to a voltage source (VDD) and a second position, where the capacitor (CRETENTION) is connected to the respective single electrode (J) or to the respective set of electrodes (J1 to Jn) and the controller ( 24) comprises or has an associated switching circuit (SS), to switch the switcher (SS) from the first position to the second position in order to discharge the capacitor (CRETENTION) in proportion to the capacitance value associated with the single electrode ( J) or the corresponding set electrodes (J4, J21, J38; J20, J37, Jn).
[0005]
5. Level sensor, according to claim 1, characterized by the fact that: each set of electrodes comprises at least one first electrode (J4) and a second electrode (J21) connected together in parallel; and the comparator circuit is predisposed to compare the digital count determined at said input (IN) or the voltage determined at said input (IN) with at least two corresponding thresholds or reference values in order to deduce the possibility of the medium (L) whether or not it is facing the first electrode (J4) and / or the second electrode (J21),
[0006]
6. Level sensor according to claim 1, characterized by the fact that: the at least one threshold or reference value comprises thresholds or reference values (THD, TH1, TH2, TH3; TH1, TH2, TH3) in a number corresponding to the number of electrodes in said set increased by one, or otherwise, a number corresponding to the number of electrodes in said set; and the comparator circuit is predisposed to compare the digital count determined at said input (IN) or the voltage determined at said input (IN), with each one of the thresholds or reference values in order to deduce the possibility of each one among the electrodes (J4, J21, J38) of said set are facing or not facing the medium (L).
[0007]
7. Level sensor, according to claim 1, characterized by the fact that the electrodes of the respective sets form on the electrically insulating substrate (20) respective electrode subarrays (J4 to J20; J21 to J37; J38 to Jn) arranged in sequence along a geometric axis of detection (X), where, given a number y of first electrodes (J4 to J20) connected in parallel to the second electrodes (J21 to J37), defined between each first electrode and the corresponding second electrodes are y-1 electrodes.
[0008]
8. Level sensor, according to claim 1, characterized by the fact that at least a portion of the electrically insulating substrate (20) is defined against the insulating layer (16; 16 ") on one side of it provided the plurality of electrodes (J1 to Jn), at least partially in contact with the insulating layer (16; 16 ").
[0009]
9. Level sensor, according to claim 1, characterized by the fact that between the insulation layer (16; 16 ") and an electrically insulating substrate face (20) that carries the plurality of electrodes (J1 to Jn) there are a filling material (G) is present, in which the filling material (G) is defined between the insulation layer (16; 16 ") and the face mentioned above and / or a front of the electrodes (J).
[0010]
10. Level sensor, according to claim 1, characterized by the fact that the arrangement of capacitive elements is contained in an electrically insulating and liquid-impermeable enclosure (16) that defines said at least one insulation layer and is configured to be defined inside the container (1) according to the geometric axis of detection (X), the housing being a housing (16) that defines a respective cavity (H) for insertion of the electrically insulating substrate (20) that holds the electrodes (J1 to Jn) or, otherwise, it is an overmolded casing in at least part of the electrically insulating substrate (20) that holds the electrodes (J1 to Jn).
[0011]
11. Level sensor, according to claim 1, characterized by the fact that it comprises at least one of: - a sensor body (10a) that defines a fixation portion (14) configured to couple impermeable to liquid in a respective installation opening (5) of the container (1), the fixing portion having at least one seat for a corresponding elastic element (15; 15 ', 15 "); - a sensor body (10a) produced, at least partially, a moldable thermoplastic material selected from a polypropylene, a high density polyethylene and a cyclic olefin copolymer; - a sensor body (10a) defining a cavity (H) to receive the electrically insulating substrate ( 20), the cavity (H) having guide and / or positioning elements (12c, 16a) for the substrate (20); - a sensor body (10a) that has a connector (12a) with electrical terminals (21 ), in which an electrically insulating substrate (20) has electrical contacts (22) c configured for elastic coupling to the terminals (21) of the connector (12a), and the electrical contacts (22) are arranged in positions corresponding to through holes (20c) of the substrate (20); - a sensor body (10a) that has positioning elements (16a) configured to urge at least a portion (20b) of the electrically insulating substrate (20) that carries the electrodes (J1 to Jn) towards the insulation layer (16 ; 16 "), the positioning means (16a) being yieldable / or elastically deformable; - a sensor body (10a) that has coupling elements (12d) predisposed for quick coupling to a wall (2, 4) of the container (1) - a sensor body (10a) that has a distal end predisposed for releasable coupling to a container wall (1).
[0012]
12. Level sensor, according to claim 1, characterized by the fact that it comprises an electrically insulating substrate (20) that carries the electrodes (J1-Jn), in which the substrate (20): - has a first portion (20b) that carries the plurality of electrodes (J1 to Jn) and a second portion (20a) that carries a circuit arrangement (23) that includes the controller (24), with electrically conductive paths provided on the substrate (25 ) for electrical connection of the electrodes (J1 to Jn); and / or - it has at least one temperature sensor associated (26, 27); and / or - it has a distal end that is separated from a distal end of a corresponding housing (16) to compensate for any possible expansion; and / or - has at least one reference electrode (J1) associated with at least one of a portion of the distal end and a portion of the proximal end thereof; and / or - associated with a plurality of reference electrodes (J1, Jn; J18, J35), each at a respective end of an array of the plurality of electrodes (J1 to Jn) or, otherwise, reference electrodes (J18 , J35) defined between subarrays of detection electrodes (J2 to J37; J19 to J34, J36 to Jn); and / or - it has associated a plurality of reference electrodes, among which each (J1, J18, J35, Jn) is connected to a respective input (IN) of the controller (24) or, among which, at least some (J18, J35) are connected in parallel to the input (IN) of the controller (24); and / or - it has first electrodes of the plurality of electrodes (J1 to Jn) closest to each other in the direction of the geometric axis of detection (X) in relation to second electrodes of the plurality of electrodes (J1 to Jn), with the first electrodes determine a measurement resolution greater than that determined by the second electrodes.
[0013]
13. Level sensor, according to claim 1, characterized by the fact that the controller (24): - is configured to carry a sequential sampling of the capacitance values associated with the inputs (IN) of the plurality of inputs (IN1 to INn ); and / or - it is a digital electronic microcontroller with an analog to digital converter, and the inputs (IN) of the plurality of inputs (IN1 to INn) are analog inputs, and / or - it implements a sampling and retention circuit.
[0014]
14. Level sensor, according to claim 1, characterized by the fact that the controller (24) is predisposed to detect one or more of the following conditions: - the medium (L) contained in the container (1) is totally in the fluid state; - the medium (L) contained in the container (1) has completely changed from a fluid state to a solid or frozen state; - the medium (L) contained in the container (1) has a part of predominant fluid floating or immersed in which parts of the medium are in solid or frozen state ("iceberg effect"); - the medium (L) contained in the container is changing from a fluid state to a solid state or vice versa, such as freezing or thawing; - the medium contained in the container (1) includes at least one first part in the solid or frozen state (I) and a second part in the fluid or liquid state (L), between the first part (I) and the second part ( L) there is a defined layer (A) of air or gas ("igloo effect"); and - the medium (L) contained in the container (1) comprises at least a part in the solid or frozen state superimposed by a part in the fluid or liquid state.
[0015]
15. Level sensor, according to claim 1, characterized by the fact that the controller (24) comprises a conversion circuit operatively connected or connectable to each input (IN) of the plurality of inputs (IN1-INn), configured for convert an input capacitance into an equivalent resistance and to convert a current measured by means of the equivalent resistance into a digital count representing the value of the input capacitance.
[0016]
16. Method for controlling a sensor to detect the level of a medium (L) contained in a container (1), as defined in claim 1, the sensor having a plurality of electrodes arranged according to the arrangement (J1 to Jn ) that extend according to a geometric axis of detection (X) of the medium level (L), and said method comprises the steps of: i) acquiring electrical signals by means of first electrodes (J21, J37), which they are not facing the middle (L); ii) acquire electrical signals through a certain number of second electrodes (J38, Jn) that are at a height greater than the first electrode considered (J37); iii) check the possibility of having at least one electrode present above the first considered electrode (J37), among the second electrodes mentioned above (J38, Jn), which is facing the middle (L) and, thus, deduct that the medium (L) contained in the container (1) comprises at least a part in the solid or frozen state (I) that overlaps with a layer of air or gas (A), characterized by the fact that step iii) comprises: - compute the difference between the values that represent electrical signals acquired through said second electrodes (J38, Jn), and the value that represents the electrical signal acquired through the first electrode considered (J37), in order to compare the individual results at least one predefined value or threshold; and - if at least one of the differences coincides with a certain proximity to the predefined value or threshold or is within it, deduce that the medium (L) contained in the container (1) comprises at least a part in the solid or frozen state (I ) that overlaps with a layer of air or gas (A).
[0017]
17. Container, characterized by the fact that it is predisposed for coupling to a level sensor, as defined in claim 1.
[0018]
18. Method characterized by the fact that it is to control a sensor to detect the level of a medium (L), and the sensor (10) has an array of capacitive elements designed to be associated with a container (1), being that the array of capacitive elements comprises a plurality of electrodes (J1 to Jn), the electrodes (J1 to Jn) are connected to a plurality of inputs (IN1 to INn) of a control circuit (23, 24), in which at least one of a level, a quantity, a state or a characteristic of the medium (L) present in the container (1) is deduced based on the acquired electrical signals, in which the control circuit (23, 24) is operable to connect selectively tar each input (IN) of the plurality of inputs (IN1-INn) to means for capacitance measurement, and for connection to the ground or to a reference voltage one or more of the inputs (IN) of the plurality of inputs (IN1-INn ) different from the input (IN) each time connected to the capacitance measurement means, ca characterized by the fact that: - the detection of a capacitance value at each input (IN) of the plurality of inputs (IN1-INn) is done indirectly, based on a measurement of a voltage or by the conversion of a capacitance of input into an equivalent resistance and then the conversion of the current measured by means of the equivalent resistance in a digital gem counter, - a digital count determined at said input (IN), or a voltage determined at said input (IN), is compared to at least one corresponding reference value or threshold (THD, TH1, TH2, TH3), - the digital count is determined at said input (IN) or voltage determined at said input (IN) is a differential count or a differential voltage , obtained by computing a difference between a digital count value or voltage detected for said input (IN) and a count value or voltage detected for an input (IN) of the plurality of inputs (THD, TH1, TH2, TH3) that is connected to at least u m reference electrode (J1), the control circuit (23, 24) is predisposed to compare the value of the digital count or differential voltage with at least one threshold or reference value (THD, TH1, TH2, TH3).

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法律状态:
2020-04-28| B06U| Preliminary requirement: requests with searches performed by other patent offices: procedure suspended [chapter 6.21 patent gazette]|

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2021-01-26| B09A| Decision: intention to grant [chapter 9.1 patent gazette]|

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2021-03-30| B16A| Patent or certificate of addition of invention granted [chapter 16.1 patent gazette]|Free format text: PRAZO DE VALIDADE: 20 (VINTE) ANOS CONTADOS A PARTIR DE 14/09/2015, OBSERVADAS AS CONDICOES LEGAIS. |

优先权:

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申请号 | 申请日 | 专利标题

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ITTO2014A000726|2014-09-15|

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ITTO20140726|2014-09-15|

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PCT/IB2015/057043|WO2016042459A1|2014-09-15|2015-09-14|Sensor for detecting the level of a medium|

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