JP2006093410A - Solenoid driver - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solenoid driver which determines the position of a plunger of an electromagnetic solenoid without a separately installed sensor for detecting the position of the plunger. <P>SOLUTION: The solenoid driver detects the inductance of the coil 22 of the electromagnetic solenoid that changes in response to the position of the plunger of the solenoid. The solenoid driver, therefore, determines the position of the plunger based on the inductance of the coil 22 without the separately installed sensor for detecting the position of the plunger. The solenoid driver, particularly, detects the inductance of the coil 22 based on the response time of a coil current while a pulse voltage is applied for plunger drive. This solenoid driver eliminates the need of separately applying a pulse voltage for detecting the inductance of the coil 22 in addition to the pulse voltage for plunger drive, thus enabling efficient detection of the inductance of the coil 22. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a solenoid driving device that drives an electromagnetic solenoid.

Conventionally, an electromagnetic solenoid having a configuration in which a plunger (movable iron piece) is moved by a magnetic force generated by a coil is known.
Among such electromagnetic solenoids, there is one in which the position of the plunger is detected using a sensor or a switch (see, for example, Patent Document 1).
JP-A-5-243040

However, if a sensor or the like for detecting the position of the plunger is separately provided, there is a problem that the number of parts increases and the apparatus becomes large.
The present invention has been made in view of these problems, and an object of the present invention is to make it possible to determine the position of the plunger without separately providing a sensor or the like for detecting the position of the plunger of the electromagnetic solenoid.

  In order to achieve the above object, a solenoid driving apparatus according to claim 1 is for driving an electromagnetic solenoid configured to move a plunger by a magnetic force generated by a coil. And this solenoid drive device is provided with the inductance detection means which detects the inductance of the coil which changes according to the position of a plunger.

  For this reason, according to this solenoid drive device, it becomes possible to determine the position of the plunger without separately providing a sensor or the like for detecting the position of the plunger. In other words, since the inductance of the coil changes according to the position of the plunger, the position of the plunger can be determined based on the inductance of the coil.

  In addition, as a method of detecting the inductance of the coil, a method of detecting when a stepped voltage (for example, a pulse voltage) is applied to the coil based on a delay in the response time of the current flowing through the coil, or a voltage across the coil For example, a detection method based on at least one of an overshoot state and an undershoot state may be considered.

  In addition, as a method of determining the specific position of the plunger based on the inductance of the coil, a method of referring to data (such as a data table) obtained by measuring the correspondence between the coil inductance and the plunger position in advance, A method of calculating based on a calculation formula representing the relationship between the position of the plunger and the position of the plunger is conceivable.

  Next, the solenoid drive device according to claim 2 is for driving an electromagnetic solenoid configured to move the plunger by the magnetic force generated by the coil, similarly to the solenoid drive device according to claim 1. The solenoid driving device is adapted to the position of the plunger based on the pulse voltage applying means for applying the pulse voltage for driving the plunger to the coil and the current flowing through the coil in the state where the pulse voltage for driving the plunger is applied. And an inductance detecting means for detecting the inductance of the coil that changes.

  For this reason, according to this solenoid drive device, the position of the plunger can be determined based on the inductance of the coil without separately providing a sensor or the like for detecting the position of the plunger, as in the solenoid drive device of claim 1. Become. In addition, in the solenoid drive device according to the second aspect of the present invention, the coil inductance is detected based on the current flowing through the coil in a state where the pulse voltage for driving the plunger is applied, and the coil inductance is detected. Since it is not necessary to apply the pulse voltage separately from the pulse voltage for driving the plunger, the coil inductance can be detected efficiently.

Here, specifically, the detection of the inductance based on the current flowing through the coil can be performed, for example, as in claim 3.
That is, in the solenoid drive device according to claim 3, in the solenoid drive device according to claim 2, the inductance detection means is based on a response time of a current flowing through the coil in a state where a pulse voltage for driving the plunger is applied. Detect the coil inductance. According to this configuration, the inductance of the coil can be detected with high accuracy. This is because the inductance of the coil appears remarkably as a delay in the response time of the current when a step-like voltage is applied.

  Next, the solenoid drive device according to claim 4 is for driving an electromagnetic solenoid having a configuration in which the plunger is moved by the magnetic force generated by the coil, similarly to the solenoid drive device according to claim 1. Then, the solenoid driving device is arranged at the position of the plunger based on the pulse voltage applying means for applying a pulse voltage for driving the plunger to the coil and the voltage across the coil in the state where the pulse voltage for driving the plunger is applied. And an inductance detecting means for detecting the inductance of the coil that changes in response.

  For this reason, according to this solenoid drive device, the position of the plunger can be determined based on the inductance of the coil without separately providing a sensor or the like for detecting the position of the plunger, as in the solenoid drive device of claim 1. Become. In addition, in the solenoid drive device according to the fourth aspect of the invention, the inductance of the coil is detected based on the voltage across the coil when the pulse voltage for driving the plunger is applied, and the inductance of the coil is detected. For this reason, it is not necessary to apply the pulse voltage separately from the pulse voltage for driving the plunger, so that the inductance of the coil can be detected efficiently.

Here, the detection of the inductance based on the both-ends voltage of the coil can be performed specifically as described in claim 5, for example.
That is, in the solenoid drive device according to claim 5, in the solenoid drive device according to claim 4, the inductance detection means is based on at least one of an overshoot state and an undershoot state occurring in the voltage across the coil. Detect the inductance. According to this configuration, the inductance of the coil can be detected based on the voltage across the coil. This is because the overshoot or undershoot that occurs in the voltage across the coil by applying a step-like voltage changes in its degree (amplitude, vibration period, rate of change, etc.) according to the inductance of the coil.

  Next, a solenoid drive device according to a sixth aspect of the present invention is the solenoid drive device according to any one of the second to fifth aspects, wherein the pulse voltage application means generates a constant duty ratio (high frequency in one cycle) as a pulse voltage for driving the plunger. The external force applied to the plunger is detected according to the degree of change in the inductance of the coil detected by the inductance detecting means in a state where the pulse voltage of the level period is applied to the coil.

  That is, the external force applied to the plunger according to the degree of change in the position of the plunger in a state where a pulse voltage with a constant duty ratio is applied (in other words, the position of the plunger does not change unless an external force is applied). It is trying to detect. Here, the degree (direction, size, etc.) of the external force applied to the plunger can be detected based on the moving speed of the plunger, for example.

According to the solenoid driving apparatus having such a configuration, it is possible to detect an external force applied to the plunger without separately providing a sensor or the like.
Next, in the solenoid drive device according to claim 7, in the solenoid drive device according to any one of claims 2 to 6, the pulse voltage applying means is driven by a plunger based on the inductance of the coil detected by the inductance detection means. Vary the duty ratio of the pulse voltage.

That is, the duty ratio of the pulse voltage for driving the plunger is changed based on the position of the plunger.
For this reason, according to this solenoid drive device, the efficient drive according to the position of the plunger is realizable. For example, as the difference between the target position of the plunger and the actual position increases, the duty ratio of the pulse voltage for driving the plunger can be changed greatly.

  Further, in the solenoid drive device according to claim 8, in the solenoid drive device according to claim 7, the pulse voltage application means is for driving the plunger so as to keep the inductance of the coil detected by the inductance detection means constant. Adjust the duty ratio of the pulse voltage.

That is, the duty ratio of the pulse voltage for driving the plunger is adjusted so as to keep the position of the plunger constant.
For this reason, according to the present solenoid drive device, the position of the plunger can be controlled to be constant regardless of the presence or absence of an external force.

  Next, in the solenoid drive device according to claim 9, in the solenoid drive device according to claim 7 or 8, the pulse voltage application means applies a pulse voltage having a constant duty ratio to the coil as a pulse voltage for driving the plunger. In this state, the adjustment degree of the duty ratio of the pulse voltage for driving the plunger is changed in accordance with the change degree of the inductance of the coil detected by the inductance detection means.

That is, the adjustment degree of the duty ratio of the pulse voltage for driving the plunger is changed according to the degree of external force applied to the plunger.
For this reason, according to this solenoid drive device, the efficient drive according to the degree of the external force added to a plunger is realizable. For example, the duty ratio of the pulse voltage for driving the plunger can be greatly changed as the degree of external force applied to the plunger is increased.

Embodiments to which the present invention is applied will be described below with reference to the drawings.
FIG. 1 is a circuit diagram of the solenoid drive device of the first embodiment.
As shown in the figure, in this solenoid drive device, a drive power supply (DC power supply) 11, a P-channel MOSFET (hereinafter simply referred to as “FET”) 12, and an electromagnetic solenoid 20 (FIG. 2) to be described later. A coil 22 as a component and a current detection resistor 31 for detecting a current flowing through the coil 22 (hereinafter referred to as “coil current”) are connected in series.

  In this solenoid drive device, a so-called free-wheeling diode 13 for consuming the energy of the coil 22 is connected in parallel with the coil 22 and the current detection resistor 31 connected in series.

Further, in the solenoid driving device, a current detection circuit 30 is configured using the current detection resistor 31.
In addition, the solenoid driving apparatus is provided with a microcomputer (hereinafter referred to as “microcomputer”) 40 for performing various controls.

  The FET 12 has a drain connected to the driving power supply 11, a source connected to one end of the coil 22, and a gate connected to the output port P 1 of the microcomputer 40. Therefore, the FET 12 is switched according to a signal output from the output port P1 of the microcomputer 40. Specifically, the signal is turned on when the signal output from the output port P1 becomes low level, and turned off when the signal becomes high level. The FET 12 is provided with a protection diode 12a for protecting the FET 12 from a reverse voltage. The anode of the protection diode 12a is connected to the source of the FET 12, and the cathode is connected to the drain of the FET 12.

The coil 22 is a component of the electromagnetic solenoid 20 shown in FIG.
The electromagnetic solenoid 20 shown in the figure includes a plunger (movable iron piece) 21 and a coil 22, and is configured such that the position of the plunger 21 changes continuously according to the magnitude of the magnetic force generated in the coil 22. It is well known.

  The plunger 21 is a columnar magnetic body, and is provided so as to be slidable along the axial direction thereof. And the plunger 21 drives the drive target object which is not shown in figure directly or indirectly fixed with respect to this plunger 21 by the slide movement.

  The coil 22 is wound so as to surround the outer peripheral surface of the plunger 21, and attracts the plunger 21 in the direction in which the plunger 21 is drawn into the coil 22 (the left direction in FIG. 2) by the magnetic force generated by energization. The plunger 21 is applied with a force in a direction away from the coil 22 (a right direction in FIG. 2) by a spring (not shown), and the energization amount to the coil 22 (in the case of this solenoid driving device, as will be described later). The position of the plunger 21 can be arbitrarily adjusted according to the duty ratio of the pulse voltage applied to the coil 22. Further, the coil 22 is provided with a stopper 23 for regulating the movement limit position of the plunger 21 toward the coil 22 (specifically, the movement limit position in the left direction in FIG. 2).

  On the other hand, in FIG. 1, the current detection circuit 30 includes the current detection resistor 31, a comparator 32, and a reference voltage source 33 that generates a predetermined reference voltage Vref. The reference voltage source 33 may be configured to generate the reference voltage Vref by, for example, dividing the voltage of the driving power supply 11, or from a power supply different from the driving power supply 11. It may be configured to generate the voltage Vref.

  The comparator 32 has its non-inverting input terminal (+) connected to the connection point between the current detection resistor 31 and the coil 22, its inverting input terminal (-) connected to the reference voltage source 33, and its output. The terminal is connected to the input port P2 of the microcomputer 40. Therefore, the voltage V1 across the current detection resistor 31 is input to the non-inverting input terminal (+) of the comparator 32, and the reference voltage Vref is input to the inverting input terminal (−). The output voltage of the comparator 32 is low when the voltage V1 across the current detection resistor 31 is less than or equal to the reference voltage Vref, and is high when the voltage V1 across the current detection resistor 31 is greater than the reference voltage Vref. .

On the other hand, the microcomputer 40 performs a process of driving the plunger 21 of the electromagnetic solenoid 20 and a process of determining the position of the plunger 21 in the electromagnetic solenoid 20.
(1): Processing for Driving the Plunger 21 of the Electromagnetic Solenoid 20 The microcomputer 40 has its output port P1 connected to the gate of the FET 12 as described above. Then, the microcomputer 40 applies a pulse voltage for driving the plunger 21 to the coil 22 by switching the FET 12 by outputting a pulse signal from the output port P1. Note that the pulse voltage for driving the plunger 21 has a form obtained by inverting the pulse signal from the output port P1.

  Further, the microcomputer 40 performs PWM control to change the duty ratio of the pulse signal output from the output port P1, thereby changing the duty ratio of the pulse voltage for driving the plunger 21 to change the position of the plunger 21 in the electromagnetic solenoid 20. (In other words, the position of the driving object) is controlled.

(2): Processing for determining the position of the plunger 21 in the electromagnetic solenoid 20 On the other hand, the microcomputer 40 has its input port P2 connected to the output terminal of the comparator 32 as described above, and is input from this input port P2. Based on the signal, the position of the plunger 21 in the electromagnetic solenoid 20 (in other words, the position of the driven object) is determined. Specifically, the microcomputer 40 receives the timing at which the pulse signal output from the output port P1 falls from the high level to the low level (the timing at which the pulse voltage for driving the plunger 21 rises) and the signal input from the input port P2. The position of the plunger 21 is determined based on the time difference from the timing of rising from the low level to the high level.

Here, the reason why the position of the plunger 21 in the electromagnetic solenoid 20 can be determined in this way will be described.
In the electromagnetic solenoid 20, the inductance of the coil 22 changes according to the position of the plunger 21. Specifically, the inductance increases in the state where the plunger 21 is accommodated in the coil 22, and the inductance decreases as the plunger 21 moves away from the coil 22. For this reason, the position of the plunger 21 can be determined based on the inductance of the coil 22.

  On the other hand, the inductance of the coil 22 remarkably appears as a delay in the response time of the coil current when a stepped voltage is applied to the coil 22. Specifically, the larger the inductance of the coil 22, the greater the delay in the response time of the coil current. For this reason, the inductance of the coil 22 can be detected based on the response time of the coil current.

Therefore, the position of the plunger 21 can be determined based on the response time of the coil current.
In the first embodiment, as shown in FIG. 3, the microcomputer 40 determines the coil current response time when the pulse signal output from the output port P1 falls from the high level to the low level (when the FET 12 is turned on). The time from when the pulse voltage for driving the plunger 21 rises) until the coil current reaches the reference current Iref is obtained. Strictly speaking, there is a slight time difference between the timing at which the pulse signal output from the output port P1 changes from the high level to the low level and the timing at which the FET 12 is turned on. In this embodiment, the timing at which the pulse signal from the output port P1 changes and the timing at which the FET 12 is turned on / off are the same.

  Here, the timing at which the coil current reaches the reference current Iref is detected by the current detection circuit 30. That is, the comparator 32 of the current detection circuit 30 inputs the coil current in the form of a voltage V1 across the current detection resistor 31, and the voltage V1 across the current detection resistor 31 when the coil current is the reference current Iref. When the voltage V1 across the current detection resistor 31 is lower than the reference voltage Vref, a low level signal is output, and the voltage V1 across the current detection resistor 31 is greater than the reference voltage Vref. In the state, a high level signal is output. That is, the comparator 32 of the current detection circuit 30 outputs a low level signal when the coil current is equal to or lower than the reference current Iref, and outputs a high level signal when the coil current is larger than the reference current Iref. Therefore, from the time when the pulse signal output from the output port P1 falls from the high level to the low level (in other words, when the FET 12 is turned on and the pulse voltage for driving the plunger 21 rises), the input port P2 The position of the plunger 21 in the electromagnetic solenoid 20 can be determined based on the time (coil current response time) until the input signal (the output voltage of the comparator 32) rises from the low level to the high level. Since the waveform of the coil current and the waveform of the voltage V1 across the current detection resistor 31 have the same shape, a common waveform is used in FIG.

Next, a usage example of the solenoid driving device will be described.
[Determination of Specific Position of Plunger 21 in Electromagnetic Solenoid 20]
In this solenoid drive device, the specific position of the plunger 21 in the electromagnetic solenoid 20 (in other words, the specific position of the driven object) can be determined. For example, a data table showing the correspondence between the response time of the coil current and the position of the plunger 21 is stored in a ROM (not shown) of a microcomputer and the position of the plunger 21 is determined by referring to this data table. To do. Instead of the data table, for example, the position of the plunger 21 may be determined by performing an operation using a calculation formula indicating the correspondence between the response time of the coil current and the position of the plunger 21.

[Control to keep plunger 21 at a fixed position]
In the present solenoid drive device, it is possible to perform control to keep the position of the plunger 21 (in other words, the position of the driving object) at a fixed position even under a situation where an external force is applied to the plunger 21. For example, feedback control is performed so as to keep the plunger 21 at the target position by changing the duty ratio of the pulse voltage applied to the coil 22 based on the deviation between the target position of the plunger 21 and the actual position. It should be noted that the duty ratio of the pulse voltage applied to the coil 22 is changed based on the deviation between the target value of the inductance of the coil 22 (in other words, the response time of the coil current) and the detected value, and the inductance of the coil 22 is set as the target. Feedback control may be performed so as to maintain the value.

[Detection of external force applied to plunger 21]
In this solenoid drive device, it is possible to detect an external force applied to the plunger 21 (in other words, an external force applied to the driven object). For example, it is detected that an external force is applied based on a change in the position of the plunger 21 (in other words, a change in the inductance of the coil 22) while a pulse voltage having a constant duty ratio is being applied to the coil 22. Furthermore, the direction and magnitude of the external force can be detected based on the moving speed of the plunger 21 due to the external force. Further, the position of the plunger 21 can be controlled so as to change the adjustment degree of the duty ratio of the pulse voltage in accordance with the magnitude of the external force applied to the plunger 21. For example, it is possible to perform control such that the duty ratio of the pulse voltage is increased as the external force applied to the plunger 21 is increased. In this way, efficient driving according to the degree of external force applied to the plunger 21 can be realized.

  In the solenoid drive device of the first embodiment, the current detection circuit 30 and the processing of the microcomputer 40 that detects the response time of the coil current correspond to inductance detection means, and include a drive power supply 11, an FET 12, The processing of the microcomputer 40 that outputs a pulse signal corresponds to the pulse voltage applying means.

  As described above, in the solenoid drive device according to the first embodiment, since the inductance of the coil 22 that changes in accordance with the position of the plunger 21 is detected, a sensor for detecting the position of the plunger 21 or the like. The position of the plunger 21 can be determined based on the inductance of the coil 22. Further, in the configuration in which the position of the plunger is detected by a sensor or switch that is turned on / off according to the position of the plunger, it is difficult to detect the fine position of the plunger. Since the size can be detected finely, the position of the plunger 21 can be accurately determined. In particular, in this solenoid drive device, the inductance of the coil 22 is detected based on the response time of the coil current in the state where the pulse voltage for driving the plunger 21 is applied. In addition, since it is not necessary to apply a pulse voltage for detecting the inductance of the coil 22, the inductance of the coil 22 can be detected efficiently. In addition, since the inductance of the coil 22 appears most prominently as a delay in the response time of the coil current, the inductance of the coil 22 can be detected with high accuracy. In addition, since the response time of the coil current can be detected every time the pulse voltage rises, the change in the position of the plunger 21 can be determined in detail.

  In the solenoid drive device of the first embodiment, when the pulse signal output from the output port P1 falls from the high level to the low level (when the FET 12 is turned on, the pulse voltage applied to the coil 22 is The inductance of the coil 22 (in other words, the position of the plunger 21) is detected based on the time from when the output voltage of the comparator 32 rises from the low level to the high level after the rise from the low level to the high level. However, it is not limited to this. For example, from the time when the pulse signal output from the output port P1 rises from the low level to the high level (when the FET 12 is turned off and the pulse voltage applied to the coil 22 falls from the high level to the low level). The inductance of the coil 22 may be detected based on the time until the output voltage of the comparator 32 falls from the high level to the low level. In particular, if the inductance of the coil 22 is detected both when the FET 12 is on and when it is off, the change in the position of the plunger 21 can be determined in more detail.

  In the solenoid drive device of the first embodiment, a P-channel MOSFET is used as a switching element for applying a pulse voltage to the coil 22, but an N-channel MOSFET may be used instead. . Since the N-channel MOSFET is more versatile than the P-channel MOSFET, cost reduction can be achieved.

  Specifically, for example, in the N-channel MOSFET, the drain is connected to the resistor 31 and the source is connected to the ground potential on the ground side (the side opposite to the connection side with the coil 22) of the current detection resistor 31 in FIG. Can be arranged as follows. In this case, the freewheeling diode 13 is connected in parallel with the coil 22 and the current detection resistor 31 connected in series.

  For example, if the response time of the coil current when the FET 12 is turned on is detected and the response time of the coil current when the FET 12 is turned off is not detected, the N-channel MOSFET is connected to the coil 22 in FIG. It can also be arranged between the detection resistor 31. In this case, the freewheeling diode 13 is connected in parallel with the coil 22.

On the other hand, it goes without saying that elements other than MOSFETs (for example, bipolar transistors, thyristors, IGBTs, etc.) can be used as switching elements.
By the way, in the solenoid drive device of the first embodiment, the inductance of the coil 22 (in other words, the position of the plunger 21) is detected based on the response time of the coil current. However, the present invention is not limited to this. . For example, the inductance of the coil 22 can be detected based on the voltage across the coil 22.

Therefore, a solenoid drive device according to a second embodiment configured to detect the inductance of the coil 22 based on the voltage across the coil 22 will be described.
FIG. 4 is a circuit diagram of the solenoid driving apparatus according to the second embodiment.

  As shown in the figure, the solenoid driving device of the second embodiment is different from the solenoid driving device of the first embodiment (FIG. 1) in that it does not have a current detection circuit 30 and the coil 22 A resistor 60 is provided between the FET 12 and the coil 22 and an A / D conversion circuit 50 that performs analog / digital conversion (A / D conversion) of the both-end voltage V2 and outputs it to the input port P3 of the microcomputer 40. However, the point that the free-wheeling diode 13 is connected in parallel with the resistor 60 and the coil 22 that are connected in series differs from the processing that the microcomputer 40 performs to determine the position of the plunger 21 in the electromagnetic solenoid 20. In addition, the same code | symbol is attached | subjected about the same structure as the solenoid drive device of the said 1st Embodiment, and detailed description is abbreviate | omitted.

  In the solenoid drive device of the second embodiment, the microcomputer 40 has the input port P3 connected to the output terminal of the A / D conversion circuit 50 as described above, and based on the signal input from the input port P3. The position of the plunger 21 in the electromagnetic solenoid 20 (in other words, the position of the driving object) is determined. Specifically, the microcomputer 40 determines the position of the plunger 21 based on the magnitude of the overshoot that occurs in the voltage V2 across the coil 22.

Here, the reason why the position of the plunger 21 in the electromagnetic solenoid 20 can be determined in this way will be described.
As described above, in the electromagnetic solenoid 20, since the inductance of the coil 22 changes according to the position of the plunger 21, the position of the plunger 21 can be determined based on the inductance of the coil 22.

  On the other hand, the inductance of the coil 22 of the electromagnetic solenoid 20 appears as the magnitude of the overshoot that occurs in the voltage V <b> 2 across the coil 22 when a stepped voltage is applied to the coil 22. That is, as shown in FIG. 5, the equivalent circuit of the coil 22 of the electromagnetic solenoid 20 can be expressed as an inductance component L and a resistance component R connected in series, and a capacitance component C connected in parallel thereto. Therefore, the voltage V2 across the coil 22 basically has the same waveform as the pulse voltage applied to the coil 22, but when the voltage V2 rises from a low level to a high level as shown in FIG. Overshoot occurs in the case. Note that when the voltage V2 across the coil 22 falls from the high level to the low level, an undershoot occurs, but the illustration is omitted.

  The magnitude (amplitude) of the overshoot that occurs in the voltage V2 across the coil 22 increases as the inductance of the coil 22 increases. For this reason, the inductance of the coil 22 can be detected based on the magnitude of the overshoot generated in the voltage V2 across the coil 22.

Therefore, the position of the plunger 21 can be determined based on the magnitude of the overshoot that occurs in the voltage V2 across the coil 22.
Here, the magnitude of the overshoot generated in the voltage V2 across the coil 22 can be detected based on the output signal of the A / D conversion circuit 50. For example, the voltage V2 across the voltage V2 within a predetermined period in which overshoot occurs. The maximum value can be detected as the size of the overshoot. However, in this solenoid drive device, the occurrence of overshoot is suppressed by the action of the protective diode 12a. Therefore, by providing the resistor 60, the amount of current when overshoot occurs is limited so that the voltage V across the coil 22 becomes higher. That is, by using the resistor 60, it is easy to detect overshoot.

  In the solenoid drive device of the second embodiment, the A / D conversion circuit 50 and the processing of the microcomputer 40 that detects the magnitude of the overshoot that occurs in the voltage V2 across the coil 22 correspond to inductance detection means. .

  As described above, in the solenoid drive device of the second embodiment, the inductance of the coil 22 is detected based on the magnitude of the overshoot generated in the voltage V2 across the coil 22, and based on the inductance of the coil 22. Since the position of the plunger 21 can be determined, the same effect as that of the solenoid driving device of the first embodiment can be obtained.

  In the solenoid drive device of the second embodiment, the inductance of the coil 22 (in other words, the position of the plunger 21) is detected based on the magnitude of the overshoot generated in the voltage V2 across the coil 22. This is not the only one. For example, the inductance of the coil 22 may be detected based on the overshoot vibration period T (FIG. 6). That is, the greater the inductance of the coil 22, the longer the overshoot vibration period T. Therefore, the inductance of the coil 22 can be detected based on the vibration period T.

For example, the inductance of the coil 22 may be detected based on the rate of change of the overshoot waveform.
On the other hand, the inductance of the coil 22 (in other words, the position of the plunger 21) may be detected based on the state of the undershoot that occurs in the voltage V2 across the coil 22. Since undershoot also has a waveform corresponding to the inductance, detection similar to detection based on overshoot is possible. In particular, if the inductance of the coil 22 is detected based on both the overshoot and the undershoot generated in the voltage V2 across the coil 22, the change in the position of the plunger 21 can be determined in more detail.

  In the solenoid drive device of the second embodiment, a P-channel MOSFET is used as a switching element for applying a pulse voltage to the coil 22, but an N-channel MOSFET may be used instead. . Specifically, for example, an N-channel MOSFET is arranged on the ground side of the coil 22 in FIG. 4 (the side opposite to the connection side with the resistor 60), and the freewheeling diode 13 includes the resistor 60 and the coil 22 connected in series. Connected in parallel. In this way, it can be configured using an N-channel MOSFET that is more versatile than a P-channel MOSFET. Needless to say, an element other than the MOSFET can be used as the switching element.

  On the other hand, in the solenoid drive device of the second embodiment, instead of the FET 12 provided with the protective diode 12a, an FET having no protective diode (however, a high withstand voltage performance against a reverse voltage is required) is used. If configured, an overshoot of the voltage V2 across the coil 22 can be remarkably generated. Thereby, the detection accuracy of the inductance of the coil 22 (detection accuracy of the position of the plunger 21) can be improved.

  Similarly, in the solenoid drive device of the second embodiment, if the freewheeling diode 13 is not used (however, the FET 12 is required to have a high withstand voltage performance with respect to a positive voltage), the voltage across the coil 22 V2 undershoot can be remarkably generated.

Furthermore, in the solenoid drive device of the second embodiment, it is possible to adopt a configuration in which the resistor 60 is not used.
As mentioned above, although one Embodiment of this invention was described, it cannot be overemphasized that this invention can take a various form.

For example, a superconducting coil may be used as the coil 22 of the electromagnetic solenoid 20.
Further, the method for detecting the inductance of the coil 22 is not limited to the methods exemplified in the above embodiments.

It is a circuit diagram of the solenoid drive device of a 1st embodiment. It is a schematic diagram showing schematic structure of an electromagnetic solenoid. It is a time chart for demonstrating the detection method of the response time of a coil current. It is a circuit diagram of the solenoid drive device of 2nd Embodiment. It is an equivalent circuit of the coil of an electromagnetic solenoid. It is explanatory drawing for demonstrating the overshoot which arises in a coil both-ends voltage.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Power supply for drive, 12 ... FET, 13 ... Freewheeling diode, 20 ... Electromagnetic solenoid, 21 ... Plunger, 22 ... Coil, 30 ... Current detection circuit, 31 ... Current detection resistor, 32 ... Comparator, 33 ... Reference voltage source, 40 ... microcomputer, 50 ... A / D conversion circuit

Claims (9)

A solenoid driving device for driving an electromagnetic solenoid configured to move a plunger by a magnetic force generated by a coil,
A solenoid drive device comprising: inductance detection means for detecting an inductance of the coil that changes in accordance with a position of the plunger. A solenoid driving device for driving an electromagnetic solenoid configured to move a plunger by a magnetic force generated by a coil,
Pulse voltage applying means for applying a pulse voltage for driving the plunger to the coil;
Inductance detecting means for detecting an inductance of the coil that changes in accordance with a position of the plunger based on a current flowing through the coil in a state where the pulse voltage for driving the plunger is applied;
A solenoid drive device comprising: In the solenoid drive device according to claim 2,
The solenoid drive device according to claim 1, wherein the inductance detection means detects the inductance of the coil based on a response time of a current flowing through the coil in a state where the pulse voltage for driving the plunger is applied. A solenoid driving device for driving an electromagnetic solenoid configured to move a plunger by a magnetic force generated by a coil,
Pulse voltage applying means for applying a pulse voltage for driving the plunger to the coil;
Inductance detection means for detecting the inductance of the coil that changes according to the position of the plunger, based on the voltage across the coil in a state where the pulse voltage for driving the plunger is applied;
A solenoid drive device comprising: In the solenoid drive device according to claim 4,
The solenoid drive device according to claim 1, wherein the inductance detection means detects the inductance of the coil based on at least one of an overshoot state and an undershoot state generated in a voltage across the coil. In the solenoid drive device according to any one of claims 2 to 5,
According to the degree of change in the inductance of the coil detected by the inductance detecting means in a state where a pulse voltage having a constant duty ratio is applied to the coil as the plunger driving pulse voltage by the pulse voltage applying means. And detecting an external force applied to the plunger. In the solenoid drive device according to any one of claims 2 to 6,
The solenoid drive device characterized in that the pulse voltage application means changes a duty ratio of the pulse voltage for driving the plunger based on the inductance of the coil detected by the inductance detection means. In the solenoid drive device according to claim 7,
The solenoid drive device, wherein the pulse voltage application means adjusts a duty ratio of the pulse voltage for driving the plunger so as to keep the inductance of the coil detected by the inductance detection means constant. In the solenoid drive device according to claim 7 or 8,
The pulse voltage application means is adapted to a degree of change in inductance of the coil detected by the inductance detection means in a state where a pulse voltage having a constant duty ratio is applied to the coil as the pulse voltage for driving the plunger. Accordingly, the degree of adjustment of the duty ratio of the pulse voltage for driving the plunger is changed accordingly.

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