• 专利附录
  • 专利说明
  • 权利要求
  • 类似技术
  • 同族专利
  • 引用文献
  • 法律状态
  • 优先权
    • 专利摘要:
    The present invention relates to a capacitive device (2) in a motor vehicle for detecting the presence of an occupant inside the vehicle, said device comprising - a first electrode (20) separated from a second electrode (21) by a dielectric material (22) for forming a capacitive sensor, said capacitive sensor being disposed on a surface of a vehicle component; - a voltage generator (23) arranged to generate an alternating voltage between said first and second electrodes (20,21 and a current measurement circuit (24) arranged to measure the current between the second electrode and an electrical ground of the vehicle, the presence of said occupant near said component being a function of the measured current.
    公开号:FR3065291A1
    申请号:FR1854463
    申请日:2018-05-25
    公开日:2018-10-19
    发明作者:Pierre Sabourin
    申请人:Autoliv Development AB；
    IPC主号:
    专利说明:

    © Publication no .: 3 065291 (only to be used for reproduction orders) © National registration no .: 18 54463 ® FRENCH REPUBLIC
    NATIONAL INSTITUTE OF INDUSTRIAL PROPERTY
    COURBEVOIE © Int Cl 8 : G 01 R27 / 26 (2017.01), B 62 D 1/04, B 60 N 2/00
    A1 PATENT APPLICATION
    ©) Date of filing: 25.05.18. © Applicant (s): AUTOLIV DEVELOPMENT AB - SE. (© Priority: @ Inventor (s): SABOURIN PIERRE. ©) Date of public availability of the request: 19.10.18 Bulletin 18/42. ©) List of documents cited in the report preliminary research: The latter was not established on the date of publication of the request. (© References to other national documents ® Holder (s): AUTOLIV DEVELOPMENT AB. related: ©) Extension request (s): © Agent (s): NOVAGRAAF PATENTS.
    DEVICE FOR DETECTING THE PRESENCE OF AN OCCUPANT WITHIN THE INTERIOR OF A VEHICLE.
    FR 3,065,291 - A1 yV / The present invention relates to a capacitive device (2) in a motor vehicle for detecting the presence of an occupant inside the vehicle, said device comprising
    a first electrode (20) separated from a second electrode (21) by a dielectric material (22) to form a capacitive sensor, said capacitive sensor being arranged on a surface of a component of the vehicle,
    a voltage generator (23) arranged to generate an alternating voltage between said first and second electrodes (20,21), and
    - a current measurement circuit (24) arranged to measure the current between the second electrode and an electrical ground of the vehicle, the presence of said occupant near said component being a function of the measured current.

    -1 DEVICE FOR DETECTING THE PRESENCE OF AN OCCUPANT
    INSIDE THE INTERIOR OF A VEHICLE [001] The present invention relates generally to a capacitive device for detecting the presence of an occupant inside a motor vehicle. The device can in particular be used to detect the presence of a driver's hands on the vehicle steering wheel or the presence of an occupant in one of the vehicle seats.
    It is known in the prior art such capacitive devices, such as that disclosed in document US 2010/0295563, disclosing a device comprising two electrodes separated by a dielectric material, an alternating voltage generator and a circuit for measuring the current flowing between the two electrodes. The alternating voltage generator is connected between the second electrode and the electrical ground of the vehicle. This device is mounted in a vehicle seat to detect the presence of an occupant in this seat. The detection is carried out by measuring the current flowing through the two electrodes, the intensity of this current being modified when the seat is occupied.
    A major drawback of this device is that it permanently creates electromagnetic interference (or disturbance) because an alternating current flows continuously between the second electrode and the vehicle ground.
    An object of the present invention is to respond to the drawbacks of the prior art mentioned above and in particular to reduce the emission of electromagnetic interference.
    For this, a first object of the invention relates to a capacitive measurement device in a motor vehicle for detecting the presence of an occupant inside the vehicle, said device comprising:
    A first electrode separated from a second electrode by a dielectric material to form a capacitive sensor, said capacitive sensor being arranged on a surface of a component of the vehicle, a voltage generator arranged to generate an alternating voltage between said first and second electrodes, and a current measurement circuit arranged to measure the current between the second electrode and an electrical ground of the vehicle, the presence of said occupant near said component being a function of the measured current.
    With this arrangement, the current measurement circuit receives current only when an occupant approaches the first electrode, which in particular makes it possible to reduce the emission of electromagnetic interference because no signal passes through the electrical ground when the occupant is not near the device. Detection is also improved since this makes it easier to differentiate between the presence of an occupant near the first electrode (presence of a current) and the absence of occupant (no current).
    Advantageously, the voltage generator is connected between said first and second electrodes. In other words, the voltage generator includes two output terminals, and each of the output terminals is electrically connected with one of the first electrode or the second electrode.
    In particular, the vehicle component is a steering wheel or a seat, comprising a metal frame (or a basic structure forming a chassis), and the first electrode and the second electrode are each distinct from the frame. In other words, according to a particular implementation, the voltage generator is not connected to the armature, to energize the first electrode or the second electrode.
    According to one embodiment, the voltage generator is connected between said first and second electrodes via a circuit
    -3 voltage transformer. This embodiment notably makes it possible to overcome the imperfections of the voltage generator. A generator based on operational amplifiers would be more expensive because it would require precise and therefore expensive components to reject the common mode.
    According to one embodiment, the current measurement circuit comprises an operational amplifier, mounted as a current-voltage converter connected between the second electrode and the electrical ground of the vehicle, delivering an output voltage which is a function of the current flowing between the second electrode and the electrical ground of the vehicle, and a circuit for processing said output voltage to deduce therefrom the presence or absence of said occupant near said component.
    In this embodiment, the operational amplifier receives current only when the driver is near the steering wheel.
    The operational amplifier is then less sensitive to saturation, which allows greater sensitivity or measurement accuracy.
    A second object of the invention relates to a vehicle steering wheel equipped with the capacitive device as defined in the first object of the invention and in which the second electrode is disposed between said first electrode and an armature of the steering wheel. The steering wheel frame may or may not be connected to a vehicle ground.
    A third object of the invention relates to a motor vehicle comprising a steering wheel as defined in the second object of the invention.
    A fourth object of the invention relates to a vehicle seat equipped with the capacitive device as defined in the first object of the invention, said seat comprising a frame and in which the second electrode is arranged between the first electrode and the seat frame.
    [0015] A fifth object of the invention relates to a motor vehicle comprising a seat as defined in the fourth object of the invention.
    Other characteristics and advantages of the present invention will appear more clearly on reading the detailed description which follows of an embodiment of the invention given by way of nonlimiting example and illustrated by the appended drawings, wherein :
    Figure 1 shows a block diagram showing a steering wheel equipped with two electrodes to detect the presence of the hands of a driver on the steering wheel;
    FIG. 2 represents an electrical diagram of a capacitive device according to a first embodiment of the invention;
    FIG. 3 represents an electrical diagram of the device of FIG. 2, in which the current measurement circuit is detailed; and Figure 4 shows an electrical diagram of a capacitive device according to a second embodiment of the invention.
    The invention is described below in the context of a capacitive device mounted on the steering wheel of a vehicle, said device being intended to detect the presence of hands (those of the driver) on the steering wheel of a vehicle .
    Figure 1 schematically shows a steering wheel provided with a frame 10 which can be connected to an electrical ground of the vehicle. According to the invention, the steering wheel is equipped with an external electrode 20 and an internal electrode 21 separated by a layer of dielectric material 22. The electrode 21 is present between the electrode 20 and the frame 10 of the steering wheel 1 The electrode 21 is present on the steering wheel and is not in direct contact (electrical contact) with the armature of the steering wheel. Said electrodes 20, 21 and the dielectric material form a capacitive element or sensor having a capacity C10 of predetermined construction. The capacitance C10 is generally between 500 pF and 10 nF, preferably between 1 nF and 5
    -5nF and even more preferably between 1 and 3 nF. This capacity is visible in Figure 2.
    When the driver of the vehicle brings his hands closer to the steering wheel, he adds a capacity proportional to the surface of the member approached between the external electrode 20 and the electrical mass of the vehicle. Thus, the overall capacity at the steering wheel of the vehicle is modified. Figure 2 shows the capacities present at the steering wheel:
    the construction capacity C10 present between the electrodes 20 and 21;
    - the capacity C11 present between the steering wheel 1 and the electrical ground of the vehicle; this capacity includes the capacity reported by the hands and, where applicable, one or more leakage capacities linked to the construction of the steering wheel; and the building capacity C12 present between the internal electrode
    21 and the electrical ground of the vehicle.
    Figure 2 illustrates a capacitive device 2 according to a first embodiment of the invention. This device comprises, in addition to the electrodes 20 and 21, a voltage generator 23 arranged to generate an alternating voltage between the electrodes 20 and 21 and a current measurement circuit 24 arranged to measure the current between the electrode 21 and the ground vehicle.
    The voltage generator 23 is connected between the electrodes 20 and 21 and the current measurement circuit 24 is connected between the electrode 21 and the electrical ground of the vehicle.
    The repository of the voltage generator 23 is constituted by the electrode 21. The voltage generator 23 is preferably configured to have a very low impedance relative to the capacitance C10 so that the latter has only '' a negligible influence on the current measured by the current measurement circuit 24.
    The presence of the driver's hands near or on the steering wheel is detected by measuring the current between the electrode 21 and the electrical ground of the vehicle. As indicated above, this current is measured by the current measurement circuit 24. An electrical diagram of the current measurement circuit 24 is shown in FIG. 3.
    The current measurement circuit 24 includes an operational amplifier 240 connected between the electrode 21 and the electrical ground of the vehicle and a processing circuit 241 connected to the output of the operational amplifier. The positive (+) input terminal of the operational amplifier is connected to a bias voltage which in alternating current is equivalent to an electrical ground. The negative input terminal (-) of the operational amplifier is connected to the electrode 21. The output terminal of the operational amplifier is connected to the negative input terminal via a resistor 242 connected in parallel with a capacitor 243 so that the operational amplifier forms a current-voltage converter filtered by the capacitor 243.
    The value of the resistance 242 is for example between 1 kû and 10 kû, preferably between 1 kû and 5 kû. The resistance value is advantageously selected so that the electromagnetic compatibility tests do not saturate the input stage of the amplifier. The capacitance of the capacitor 243 is selected as a function of the desired bandwidth relative to the frequency of the sinusoidal voltage generator. For example, for a frequency 100kHz and a resistance 242 of 2kQ, the capacitance of the capacitor 243 is of the order of
    220pF.
    The voltage between the input terminals of the operational amplifier 240 is zero or almost zero and its input impedance is very high and considered to be infinite. Therefore, the electrode 21 constitutes a virtual ground, which cancels any impact of the capacitor C12 (between
    -7 the electrode 21 and the electrical earth of the vehicle) on the measurement because the voltage across the terminals of the capacitor C12 is zero.
    The operational amplifier 240 being mounted as a current-voltage converter, the voltage present at its output is a replica of the current flowing between the electrode 21 and the electrical ground of the vehicle.
    The processing circuit 241 determines from the output voltage of the operational amplifier whether or not the driver's hands are present near the steering wheel. When the driver approaches his hands with electrode 20 (external electrode), a current appears between electrode 21 and the virtual ground of the vehicle. This current is converted into voltage by the operational amplifier 240 and detected by the processing circuit 241. The processing circuit 241 is for example an integrated impedance measurement circuit of the AD5933 type sold by the company
    Analog Devices.
    This arrangement has a major advantage, namely that a current does not flow to the electrical ground of the vehicle, through the armature of the steering wheel or the current measurement circuit 24, when the hands of the driver are in contact or near the steering wheel. This makes it possible to reduce, or even eliminate, the electromagnetic disturbances generated by the device outside of this situation.
    This arrangement also makes it possible to improve the precision of the detection. In fact, the capacitance C11 added by the driver being very low (of the order of 150 pF for two hands and 15 pF for a finger when there is contact with the steering wheel), the current flowing through the capacitance C11 and the current measurement circuit 24 via the vehicle's electrical ground is very weak. The presence of a current flowing between the electrode 21 and the virtual earth of the vehicle, whether it is low or not, therefore indicates that the driver's hands are near the steering wheel of the vehicle.
    -8 In addition, the operational amplifier 240 receiving current only when the driver is near the steering wheel, it is less sensitive to saturation, which allows greater sensitivity or measurement accuracy.
    In this first embodiment, the voltage generator 23 can be achieved by means of two operational amplifiers. However, this requires the use of amplifiers with precise, relatively expensive components to reject common mode.
    Also, according to a second embodiment illustrated in Figure 4, the voltage generator 23 is connected between the electrodes 20 and 21 via a voltage transformer 25. The voltage generator 23 on the one hand and the electrodes 20 and 21 on the other hand are connected respectively to the primary and secondary of the transformer 25. The transformer is used to create a galvanic isolation between the voltage generator 23 and the electrodes 20,21, and to prevent the propagation of common mode effects to the electrodes 20, 21.
    The electrodes 20 and 21 are advantageously connected to the secondary of the transformer 25 via a screened cable 26. The electrodes 20 and 21 are connected, respectively via the core and the screen of the screened cable, to the secondary of the transformer. The negative (-) input terminal of the operational amplifier is connected to the secondary of transformer 25.
    The shielded cable 26 allows to bring a constant capacity. It protects the measurement signal with virtual mass. The steering wheel frame has no impact on the measurement signal. The shielded cable also makes it possible to avoid any signal capture between the voltage generator 23 and the armatures 20, 21 liable to disturb the current measurement.
    It will be understood that various modifications and / or improvements obvious to those skilled in the art can be made to
    -9different embodiments of the invention described in the present description without departing from the scope of the invention defined by the appended claims. In particular, FIG. 1 represents a vehicle steering wheel, but the electrical device of the invention can just as easily be installed in a seat or any other part of the vehicle interior.
    The invention is for example applicable to the detection of the presence of an occupant in a car seat. Everything described above for a steering wheel is then applicable to a seat, the frame of the seat then corresponding to the frame of the steering wheel. The capacity and resistance values indicated above for the detection of hands on the steering wheel are then adapted if necessary for this new application.
    权利要求:
    Claims (7)
    [1" id="c-fr-0001]
    1. Capacitive device (2.2 ’) in a motor vehicle to detect the presence of an occupant inside the vehicle, said device
    5 comprising a first electrode (20) separated from a second electrode (21) by a dielectric material (22) to form a capacitive sensor, said capacitive sensor being arranged on a surface of a component of the vehicle, a voltage generator ( 23) arranged to generate an alternating voltage between said first and second electrodes (20,21), and a current measurement circuit (24) arranged to measure the current between the second electrode and an electrical ground of the vehicle, the presence of said occupying near said component being a function of the current measured.
    [2" id="c-fr-0002]
    2. Device according to claim 1, in which the voltage generator (23) is connected between said first and second electrodes via a voltage transformer circuit (25).
    20
    [3" id="c-fr-0003]
    3. Device according to claim 1 or 2, wherein the current measurement circuit (24) comprises an operational amplifier (240), mounted as a current-voltage converter connected between the second electrode and the electrical ground of the vehicle, delivering a voltage output which is a function of the current
    25 circulating between the second electrode and the electrical ground of the vehicle, and a processing circuit (241) of said output voltage to deduce therefrom the presence or absence of said occupant near said component.
    -11
    [4" id="c-fr-0004]
    4. Vehicle steering wheel equipped with the capacitive device (2,2 ’) according to one of the preceding claims and in which the second electrode (21) is disposed between said first electrode (20) and a frame of the steering wheel.
    [5" id="c-fr-0005]
    5. Motor vehicle comprising a steering wheel according to the preceding claim.
    [6" id="c-fr-0006]
    6. Vehicle seat equipped with the capacitive device (2,2 ′) according to one of the preceding claims, said seat comprising a frame and in which the second electrode (21) is disposed between said first electrode (20) and the seat frame.
    [7" id="c-fr-0007]
    7. Motor vehicle comprising a seat according to the preceding claim.
    PL 1/2
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    引用文献:
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    法律状态:
    2019-05-29| PLFP| Fee payment|Year of fee payment: 2 |
    2020-05-27| PLFP| Fee payment|Year of fee payment: 3 |
    2021-05-28| PLFP| Fee payment|Year of fee payment: 4 |
    优先权:
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    FR1854463|2018-05-25|
    FR1854463A|FR3065291B1|2018-05-25|2018-05-25|DEVICE FOR DETECTION OF THE PRESENCE OF AN OCCUPANT INSIDE THE INTERIOR OF A VEHICLE|FR1854463A| FR3065291B1|2018-05-25|2018-05-25|DEVICE FOR DETECTION OF THE PRESENCE OF AN OCCUPANT INSIDE THE INTERIOR OF A VEHICLE|
    US17/057,896| US20210206334A1|2018-05-25|2019-05-21|Device for detecting the presence of an occupant inside the passenger compartment of a vehicle|
    PCT/EP2019/063057| WO2019224177A1|2018-05-25|2019-05-21|Device for detecting the presence of an occupant inside the passenger compartment of a vehicle|
    JP2020563681A| JP2021520503A|2018-05-25|2019-05-21|A device for detecting the presence or absence of occupants in the passenger compartment of a vehicle|
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