• 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:
    An actuator comprising a coil and a permanent magnet plunger characterized by means for preventing, or reducing to a desired extent, the circulation of currents caused by movement of the plunger within the coil as soon as power supplied to the coil is switched off.
    公开号:BE1025915B1
    申请号:E20185745
    申请日:2018-10-26
    公开日:2020-02-12
    发明作者:Hugh-Peter Granville Kelly
    申请人:Elaut Nv；
    IPC主号:
    专利说明:

    Improvements to the operation of electromagnet actuators
    The following invention relates to improvements to the mode of operation of electromagnetic actuators with permanent magnets. In particular, it relates to such improvements as applied to the types of actuators described in my granted patent no. EP 1,305,807 and my co-pending patent application, application no.
    GB1708753.7.
    All permanent magnet electromagnetic actuators contain a coil for their operation, which can be in one or more windings, and a magnetic plunger. The coil, upon energization, provides a magnetic field for interaction with that of the magnetic plunger, resulting in thrust and movement in the desired direction of movement. Once the coil is excitation-free, the plunger is released from the influence of the magnetic field acting thereon and can return to its original starting position, under the influence of, for example, gravity or a spring.
    It is common to switch the current to the coil of an actuator on and off, whether it is a plunger of the permanent magnet type or a conventional mild steel plunger solenoid, using a drive circuit comprising a transistor or similar electronic device. contains. In both cases, however, a back emf '(return electromagnetic force) peak occurs when the current to the coil is stopped. (The peak occurs in a known manner - from the decay, on switching off, of the electromagnetic field developed by and surrounding the coil.)
    The switching connections of electronic devices are, however, vulnerable to such back-peak peaks that can be significant, for example many tens of volts, or even thousands of volts for actuators with substantial dimensions. To address this problem, it is common to connect a freewheeling diode across the coil in reverse polarity to circulate the aforementioned back-emf within the winding of the coil of the actuator and thus be self-dissipating. In this way damage to the drive circuit is avoided.
    However, in terms of the free movement to their starting position of permanent magnet plungers, the situation becomes more complicated when the applied power is switched off. (Permanent magnets are used in such plungers to improve performance. Interaction of the magnetic fields provided by the plunger magnets with the fields provided by the coil of the actuator results in increased thrust.) A disadvantage occurs in this case when a
    BE2018 / 5745 freewheel diode is used in this case, as mentioned above, to decrease the back-emf peak.
    It is known that any permanent magnet configuration (e.g., a plunger comprising permanent magnets) that has magnetic fields arising therefrom and that moves next to and with respect to a coil, when offering a fully electrical path, a current in the inductor. In the case of the above-mentioned free-running diode, this provides precisely such a fully electric path. This allows these generated currents to flow within the coil of the actuator. In accordance with electrical theory, the magnetic field created by these generated currents will be in one direction to counteract the direction of movement of the magnetic configuration (the plunger) that causes them primarily. The result can be a slow and / or restrained movement from the configuration to the starting position. For certain applications, when a smooth (i.e. rapid) return is desired, this is disadvantageous.
    According to a first aspect of the invention, an actuator comprising a coil and a permanent magnet plunger is provided with a means for preventing, or reducing to a desired extent, the circulation of currents caused by movement of the plunger within the coil as soon as power supplied to the coil is switched off.
    In this way, the generation of magnetic fields that work against the free movement of the plunger is made impossible, and the plunger can, for example, return to its starting position under the influence of gravity or spring action.
    In practice, it remains desirable to still use a freewheel diode or the like to compensate for the initial "back emf" peak that occurs when the applied power is interrupted. Such peaks occur instantaneously, and typically their rise times can have a duration of only a fraction of or a few milliseconds. This is in contrast to the typical duration of the current induced in the coil of the actuator during the time it takes the magnetic plunger to return to its starting position, which can be measured in tens of milliseconds.
    According to a second aspect of the invention, the means for preventing, or reducing to a desired extent, a zener diode having a sufficiently low conductive voltage that allows it to conduct higher, potentially harmful voltages associated with a "back emf" peak therethrough , but which is also high enough to prevent it, or
    BE2018 / 5745 to a desired extent, reduce the circulation of currents caused by the movement of the plunger within the coil.
    By way of explanation, the high "back emf" peak voltages which occur when switching off power to the coil of the actuator, which have exceeded the voltage limiting point of the zener diode, can dissipate desirably within the coil and thereby prevent damage to the control transistor circuit, while the relatively lower voltages generated by the slower movement of the magnetic plunger to its starting position fall below, or in the main part below, the cut-off point of the zener diode and prevent conduction therethrough. In this way, a slow movement of the plunger to its starting position is avoided.
    For many applications, a rapid re-activation of an actuator is not necessary, several seconds lie between one activation and the next.
    According to a third aspect of the invention, the means for preventing or reducing to a desired size is a capacitance having a sufficiently high conductivity that allows to conduct higher, potentially harmful voltages associated with a "back emf" peak therethrough, but which is also sufficiently low to prevent, or reduce to a desired extent, the circulation of currents caused by the movement of the plunger within the coil.
    Thus, currents resulting from the very high rate of voltage change associated with the "back emf" peak are deflected away harmlessly, but currents resulting from the lower rate of voltage change associated with the movement of the magnetic plunger after shutdown are not guided through it to any extent. The selection of the actual capacitance value is carefully calculated to ensure that little damping occurs in terms of the speed of the rise of the control voltage to the coil of the actuator when supplying the initial power.
    In my simultaneously filed patent application, application no. GB1708753.7, an actuator with a coil and a coaxial permanent magnet plunger is disclosed, the coil being housed in a metal housing for advantageously dissipating heat. Slits are provided in the housing to prevent the circulation of unwanted eddy currents therein, which would otherwise prevent the movement of the magnetic rod thereby.
    BE2018 / 5745
    According to a fifth aspect of the invention, the embodiment of the present invention is used in combination with the actuator of the simultaneously filed application, wherein the actuator comprises a means to prevent the circulation of eddy currents within the housing of the actuator during movement of the plunger or essentially.
    The invention will now be described with reference to the accompanying drawings, in which: 1 shows a permanent magnet actuator connected to a drive circuit according to the invention
    Figures 2a to 2e show different switching options for connection to the actuator
    Figure 3 shows an actuator with a slot housing and driven by the circuit of the invention
    Referring to Figure 1, an electromagnetic actuator with a permanent magnet is shown at 10. The actuator comprises a housing 11, a coil 12, and a permanent magnet plunger 12a. The bearings 13 and 14 guide the plunger concentrically through the coil. The plunger includes the magnets M1 and M2 to provide a permanent magnetic field, as shown at the insert at 15. In this example, excitation of the coil lifts the plunger from the rest position 16 and brings it to a stop position at 17. The plunger falls under the influence of gravity as soon as the current to the coil is cut off.
    A driving circuit 18 is connected to the coil. This includes a drive transistor 19 and other components (not shown) for supplying power to the coil of the actuator. A device 20 is provided which further controls the power to and from the coil.
    The operation of the circuit is as follows. To energize the coil of the actuator, and thereby lift the plunger from its rest position to its upper stop position, an activating signal current is supplied to the base 21 of the transistor. This allows power to flow to the coil. At this point the device 20 allows this power flow. As soon as it is necessary to de-energize the coil, the transistor is switched off and at the same time the device 20 deactivates any possibility of a reverse power flow from the coil of the actuator to the driving circuit. Thus, the device 20 is a means for preventing, or reducing to a desired extent, the circulation of currents caused by movement of the plunger within the coil as soon as power supplied to the coil is switched off.
    BE2018 / 5745
    By way of explanation, any plunger of the permanent magnet type that passes through a coil in such a way that the lines of force therefrom intersect the windings of the coil results in the generation of an emf (electromagnetic force) within the coil. . In the case of this embodiment, it is desirable that such an emf cannot circulate within the coil after the power has been cut off, and the plunger begins to fall. If not, the field created by the currents circulating in the coil - as generated by the falling rod - will be in one direction, in accordance with electrical theory, so that the movement of the falling rod is resisted and thus results in a slow / restrained movement. This is particularly relevant when a rapid (i.e., rapid or substantially instantaneous) movement is required under the influence of gravity to return the rod to its starting position. The provision within the driving circuit of the device 20 thus ensures that such a current flow cannot occur within the coil after switching off, whereby the rod can fall freely to its starting position.
    Although the embodiment of the circuit of Figure 1 and the use of the device 20 meets the objectives of the present invention, it is desirable in practice to ensure that any back emf 'peak that occurs at the time the coil is turned off is harmless dissipate. It is common to address this by inverting a freewheel diode across the coil terminals, as shown at 22 in Figure 2a. The current supplied to operate the actuator cannot flow through the diode, but as soon as the power is turned off, the "back emf" peak can circulate freely through the diode, as shown by the arrow, and self-dissipate within the coil. This thereby protects the drive transistor against undesirably high "back emf" voltage peaks. However, this embodiment cannot be used in the case described herein. The presence of the diode allows, after switching off, the free circulation of the currents in the opposite direction that would be generated in the coil during the downward movement of the plunger.
    A compromise is illustrated with reference to Figure 2b. Herein, the means for preventing, or reducing to a desired extent, the circulation of currents within the annular field coil, once power supplied to the coil is turned off, is a zener (or avalanche) diode 23 that is used instead of the conventional diode 22 of Figure 2a. The conductor voltage of the zener diode is selected to be above or close to the maximum voltage that would be generated inside the coil due to the free fall of the plunger. In this way no current can flow when the power is switched off and the plunger can fall freely. However, the conductive voltage is also selected with due consideration
    BE2018 / 5745 of the maximum allowable inverse voltage (PIV) of the drive transistor. The drive transistor is protected by ensuring that the conduction voltage is far below the PIV figure. Thus, the diode has a sufficiently low conductive voltage that allows higher, potentially harmful voltages associated with a "back emf" peak to pass therethrough, but is also sufficiently high to block, or substantially block, the passage of currents associated with lower voltage generation. (Note that the aforementioned diode 22 remains connected, as shown in series with the zener diode, to prevent forward conduction of the zener diode during the energizing phase of the coil 12.) Examples of voltages and their periodicity generated by the falling plunger , and a characteristic "back emf" peak, are shown at 24 & 25 in Figure 2c.
    To remedy the flow of any current arising from the emf generated during the movement of the plunger after the power to the coil has been cut off, an optional diode 22a may be connected in the power rail supplying the assembly, as shown. This prevents any possible power from flowing back to the power supply. It is not necessary to have a path to drain the lazy emf that arises after the power supply has been switched off. Experiments show that, in the absence of a current path, the emf simply rises and is harmlessly lost.
    Typically, the former is in the range of 10 to 20 volts, while the latter, the peak voltage, can reach 40 to 100 volts. The use of a 20 volt Zener diode will thus capture the high back emf peak while blocking the slower and slower currents generated during free fall. Such a 20-volt conducting voltage is typically well within the safe PIV of the types of bipolar or field-effect transistors that would be used to supply power to a 24-volt rail supplied actuator. The conductive voltage is therefore in the range of 25-40V. An additional aspect concerns the timing of the back emf peak and the generated voltages. A back emf peak for actuators of small to medium size can have a duration of less than a millisecond, or up to a few milliseconds, while generated currents, due to the speed of movement of a mechanical plunger, typically an order of magnitude, or more, of these periods. The use of a zener diode thus allows to process both eventualities, the immediate conduction of high emf peak voltages, but blocking the subsequent generated emf currents.
    The drive transistor of Figure 2a is shown as a standard bipolar transistor. In the case that a FET transistor is used, as shown at 26 in Fig. 2d, an additional diode 27 may be
    BE2018 / 5745 guide path are placed as shown. For clarification, many FET field effect transistors often embody their own reverse-connected diodes for safety. The presence of the additional diode 27 obviates the possibility that said embodied diode provides a conduction path for the pack of peaks.
    As an alternative to the use of zener diodes, a simple capacitor can be used, as shown at 28 in Figure 2e. Connected directly across the coil, or with the option of a series resistor as shown at 29, the capacitor can serve to provide a conductor path for a high rise time voltage back emf peak, but an insufficient conduction path for the much lower voltage speed that is inside the coil is generated by the falling plunger. That is, the capacitor has a conductance that is high enough to conduct potentially higher, potentially harmful voltages associated with a "back emf" peak through it, but that is also high enough to prevent, or reduce to a desired magnitude, of the circulation of currents caused by the movement of the plunger within the coil. The presence of the series resistance can also help in specific cases to limit the conduction of the generated voltages. An additional diode 27 as illustrated in and described with reference to Figure 2d may optionally be provided.
    Many other switching configurations are possible for isolating a conductor path for the coil after stopping the power supplied thereto, e.g. analog ports.
    With reference to Figure 3, a top view of the actuator 10 of Figure 1 is shown at 30. The housing 30 is longitudinally cut as shown at 31 and 32. The purpose is to prevent the circulation of eddy currents around the housing that would otherwise be caused by the magnetic plunger 33 moving through it, which would be a further damping of the free movement.
    The coil 34 of the actuator is connected to the drive circuit 35 in the above-mentioned manner. The combination of the slit housing and the drive circuit method as described herein provides the actuator with a substantially free-moving plunger as soon as the power supply thereto is switched off.
    Numerous variations will be apparent to those skilled in the art.
    权利要求:
    Claims (12)
    [1]
    Conclusions
    An actuator comprising a coil and a permanent magnet plunger characterized by means for preventing, or reducing to a desired extent, the circulation of currents caused by movement of the plunger within the coil as soon as power is supplied to the coil turned off.
    [2]
    An actuator according to claim 1, wherein the means for preventing or reducing to a desired size is a zener diode that has a sufficiently low conductive voltage that allows higher, potentially harmful voltages associated with a "back emf" peak therethrough but also sufficiently high to prevent, or reduce to a desired extent, the circulation of currents caused by the movement of the plunger within the coil.
    [3]
    An actuator according to claim 2, wherein the conductive voltage is in the range of 25 to 40V.
    [4]
    An actuator according to claim 2, wherein an additional diode, in reverse direction, is connected in series with the zener diode for preventing forward conduction through the zener diode of drive currents intended for the coil of the actuator.
    [5]
    An actuator according to claim 1, wherein the means for preventing, or reducing to a desired size, is a capacity that has a sufficiently high conductivity that allows it to conduct higher, potentially harmful voltages associated with a "back emf" peak therethrough but which is also sufficiently low to prevent, or reduce to a desired extent, the circulation of currents caused by the movement of the plunger within the coil.
    [6]
    An actuator according to claim 4, further comprising a resistor in series with the capacitance.
    [7]
    An actuator according to any one of the preceding claims, further comprising a FET transistor for supplying power to the coil, and a protection diode in the conduction path between the FET transistor and the coil.
    [8]
    An actuator according to any one of the preceding claims, further comprising a drive circuit in which any form of an electrical and / or electronic circuit present comprises the means for preventing, or reducing to a desired extent, the means
    BE2018 / 5745 is able to dissipate and / or process any "back emf" peak, simultaneously with blocking or substantially blocking the circulation of currents generated in the coil due to the movement of the composite plunger after stopping the feed supplied thereto power.
    5
    [9]
    An actuator according to any one of the preceding claims, further comprising a housing housing the coil and the means for preventing or substantially limiting the circulation of eddy currents within the housing of the actuator during the movement of the plunger.
    [10]
    10. An actuator according to claim 8, wherein the means for preventing the circulation of eddy currents comprises one or more gaps that are located inside the housing.
    [11]
    An amusement hall machine comprising an actuator according to any one of the preceding claims.
    [12]
    The amusement hall machine of claim 9, wherein the actuator is an actuator of one
    15 grab.
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    同族专利:
    公开号 | 公开日
    BE1025915A1|2019-08-07|
    GB201717983D0|2017-12-13|
    GB2567894A|2019-05-01|
    WO2019086356A1|2019-05-09|
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    法律状态:
    2020-04-02| FG| Patent granted|Effective date: 20200212 |
    2021-07-15| MM| Lapsed because of non-payment of the annual fee|Effective date: 20201031 |
    优先权:
    申请号 | 申请日 | 专利标题
    GB1717983.9A|GB2567894A|2017-10-31|2017-10-31|Improvements to the operation of electromagnetic actuators|
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