WO2011108313A1

WO2011108313A1 - Solenoid drive circuit

Info

Publication number: WO2011108313A1
Application number: PCT/JP2011/051659
Authority: WO
Inventors: 菊池　宏; 水野　博之
Original assignee: シーケーディ株式会社
Priority date: 2010-03-05
Filing date: 2011-01-27
Publication date: 2011-09-09
Also published as: KR101222315B1; CN102782779B; JP2011187520A; CN102782779A; KR20120124073A; JP4852160B2

Abstract

Provided is a solenoid drive circuit for suppressing a response delay caused by a surge voltage. The solenoid drive circuit (10) is provided with: a solenoid coil (11) which performs a plunger suction-attachment operation; a bidirectional Zener diode (40) which is connected in parallel to the solenoid coil (11) and absorbs, up to a Zener voltage, the surge voltage generated when the power supplied to the solenoid coil (11) is stopped; and a holding transistor (32) which is connected in series to the solenoid coil (11) and the bidirectional Zener diode (40). When a power supply voltage is applied, the holding transistor (32) turns on and a conduction path for the solenoid coil (11) is thereby formed. In this structure, the surge voltage reduced to the Zener voltage by the bidirectional Zener diode (40) is applied to the holding transistor (32).

Description

Solenoid drive circuit

The present invention relates to a solenoid drive circuit for driving a solenoid valve.

As a solenoid valve driving circuit, there is known a solenoid drive circuit that performs a plunger suction operation by energizing a solenoid coil. As a solenoid drive circuit, as shown in Patent Document 1, a timer circuit including a capacitor, an adsorption transistor through which an adsorption current corresponding to a plunger adsorption operation flows by being turned on for a timer time defined by the timer circuit, And a holding transistor in which a holding current smaller than the attracting current flows by turning on after the timer time elapses is known.

Here, a surge voltage is generated when the energization of the solenoid coil is stopped. In order to absorb the surge voltage, the solenoid drive circuit of Patent Document 1 includes a diode reversely connected in parallel to the solenoid coil. Since the surge voltage is absorbed up to the threshold voltage in the forward direction of the diode, the influence of the surge voltage on other elements is reduced.

JP-A-10-184974

However, current flows through the solenoid coil until the surge voltage becomes smaller than the threshold voltage. In this case, since the forward threshold voltage of the diode is a low voltage (about 1 V), the energization time of the solenoid coil based on the surge voltage becomes long, and the response delay time of the solenoid valve caused by the surge voltage becomes long.

Here, in recent years, solenoid valves that can be switched at high speed have been demanded. For this reason, when the response delay time by the said surge voltage is long, the problem that it cannot respond to high-speed switching may arise.

The present invention has been made in view of such circumstances, and has as its main object to provide a solenoid drive circuit that can be switched at high speed by suppressing a response delay caused by a surge voltage.

Hereinafter, effective means for solving the above-mentioned problems will be described while showing effects.

Means 1. A solenoid coil that generates a magnetic field when energized and drives an electromagnetic valve; and a switching element connected in series to the solenoid coil, the series connection body of the solenoid coil and the switching element being a power source The solenoid coil is connected to a pair of power supply terminals to which a voltage is applied. When the power supply voltage is applied, the switching element is turned on to form an energization path for the solenoid coil. In the solenoid driving circuit to be performed, as the switching element, a first switching element that is turned on until a predetermined time elapses after the power supply voltage is applied, and in parallel with the first switching element Connected and while the power supply voltage is applied And a second energization path through the first switching element and a second energization path through the second switching element as the energization path of the solenoid coil. And a limiting resistor is provided on the second energization path so that a current flowing on the second energization path is smaller than a current flowing on the first energization path. Separately from the path, a first input path connecting the input terminal of the first switching element and one of the pair of power supply terminals, and a first input path connecting the input terminal of the second switching element and the one power supply terminal. Two input paths are provided in parallel, provided on the first input path, and the first switching element is in an ON state with respect to the first switching element over the specific time. And a zener diode or varistor, and a surge voltage generated when the energization of the solenoid coil is stopped is absorbed up to a threshold voltage at which the zener diode or the varistor becomes conductive. A solenoid drive circuit, wherein a surge voltage absorbed up to the threshold voltage is applied to each switching element.

According to the means 1, when the power supply voltage is applied, each switching element is turned on. In this case, since a limiting resistor is provided on the second energization path, current flows through the first energization path. Thereafter, the first switching element is turned off at a timing when a specific time elapses with respect to the application voltage application start timing, and a current flows through the second energization path. The current is smaller than the current flowing on the first energization path. As a result, a current corresponding to the plunger adsorption operation of the solenoid valve is caused to flow based on the start of application of the power supply voltage, and after completion of the plunger adsorption operation, a current smaller than that current is caused to flow to reduce power consumption. You can plan.

In such a configuration, when a surge voltage is generated, the surge voltage is absorbed to a Zener voltage or a varistor voltage which is a threshold voltage by a Zener diode or a varistor. Since these Zener voltage or varistor voltage can be set higher than the threshold voltage in the forward direction of the diode, the threshold voltage maintaining time can be shortened compared to the configuration in which the diode is provided to absorb the surge voltage. it can. As a result, the response delay time of the solenoid valve can be shortened, and high-speed switching can be handled. Therefore, it can respond to the high-speed switching of a solenoid valve. However, when a surge voltage lowered to the threshold voltage is applied to an element having a relatively low withstand voltage in a situation where the threshold voltage is set high, the element may be destroyed. In particular, when a capacitor is provided as a timer circuit, the capacitor may be destroyed by a surge voltage.

On the other hand, according to this means, since the surge voltage absorbed up to the threshold voltage is applied to each switching element, application of the surge voltage to other elements is restricted. Thereby, the influence of the surge voltage on other elements can be reduced. Therefore, the response delay time of the solenoid valve can be shortened while suppressing destruction of other elements.

Means 2. The surge absorbing circuit is connected in parallel to the solenoid coil, and is connected in series to the switching elements, so that the surge voltage is not transmitted to the input paths. The solenoid drive circuit according to means 1, wherein the path and each of the energization paths are independent.

According to the means 2, since the surge absorption circuit is provided in parallel with the solenoid coil, when a surge voltage is generated, a closed loop circuit is formed by the solenoid coil and the surge absorption circuit. The surge voltage is absorbed by the closed loop circuit until the surge voltage reaches the threshold voltage.

In such a configuration, when each switching element is turned on by a surge voltage, the surge voltage is applied to other elements instead of the switching element, and the other elements may be destroyed.

In addition, when other circuits are provided in parallel to the solenoid drive circuit, a diode may be provided in parallel to the solenoid drive circuit so as to be forward with respect to the surge voltage from the viewpoint of surge voltage protection. . In this case, when the switching element is turned on by the surge voltage, a closed loop circuit is formed by the switching element, the diode, and the solenoid coil. Then, current continues to flow in the solenoid coil until the surge voltage becomes lower than the threshold voltage (threshold voltage in the forward direction of the diode). For this reason, the influence of the surge voltage on other elements can be reduced, while the response delay time of the solenoid valve becomes longer than the response delay time based on the threshold voltage of the Zener diode or varistor.

On the other hand, according to this means, since the input path of each switching element and each energization path for generating the surge voltage are independent from each other, the surge voltage is not transmitted to each input path. Thereby, each switching element is not turned on based on the surge voltage. Therefore, the inconvenience can be avoided.

Means 3. On the second input path, there is provided a defining resistor that defines driving power supplied to the input terminal of the second switching element, and the timer circuit is connected in series with the time constant resistor and the time constant resistor. A closed loop including the specified resistor, the time constant resistor, and the capacitor is formed by connecting the input paths, and the closed loop is configured to store the charge accumulated in the capacitor. 3. The solenoid drive circuit according to means 1 or 2, wherein a discharge path for discharging is formed.

According to the means 3, when the application of the power supply voltage is stopped, the charge accumulated in the capacitor is discharged in a closed loop formed by connecting the input paths. In this case, a time constant resistor and a capacitor are provided on the first input path, and a specified resistor is provided on the second input path, in order to define the drive power supplied to each switching element. ing. For this reason, it is not necessary to provide on each input path a semiconductor element that changes from a non-conductive state to a conductive state when a predetermined threshold voltage is applied. Thereby, by not providing the semiconductor element on the discharge path, the charge accumulated in the capacitor can be suitably discharged.

That is, if semiconductor elements such as light emitting diodes and transistors are provided on the discharge path of the capacitor, the charge corresponding to the threshold voltage necessary for these semiconductor elements to become conductive remains without being discharged. To do. Since this residual charge is released by natural discharge, the discharge time required until the charge accumulated in the capacitor is completely discharged becomes longer. Then, there is a case where electric charge remains in the capacitor at the timing when the application of the power supply voltage is started again after the application of the power supply voltage is stopped. In this case, since the specific time varies depending on the remaining charge amount, the first switching element may be turned off before the plunger adsorption operation is completed. However, if the specific time is set longer in response to the change in the on-time of the first switching element based on the residual charge amount, there is a concern that the power consumption increases.

On the other hand, according to the present means, since the semiconductor element is not provided on the discharge path, the charge accumulated in the capacitor can be completely discharged without performing the natural discharge. The discharge time can be shortened as compared with the case where the operation is performed. Thereby, specific time can be set short and reduction of power consumption can be aimed at.

Means 4. The resistance value of the specified resistor is set so that the time required to complete the discharge of the charge accumulated in the capacitor is shorter than the time required for the surge voltage to be absorbed to the threshold voltage. The solenoid drive circuit according to claim 3, wherein

According to the means 4, when the application of the power supply voltage is stopped in a situation where the capacitor is provided as the timer circuit, a surge voltage is generated and the discharge of the capacitor is started. In this case, the charge stored in the capacitor via the second input path is input to the input terminal of the second switching element, and the second switching element may be turned on.

On the other hand, according to this means, the resistance value of the specified resistor is set so that the discharge of the capacitor charge is completed at a timing before the timing at which the surge voltage becomes the threshold voltage. The second switching element is in the off state at the timing when the threshold voltage is reached. Thereby, the electric charge accumulated in the capacitor can be suitably discharged while ensuring the effect described in the means 2.

Means 5. The first switching element is an NPN-type first bipolar transistor, the second switching element is an NPN-type second bipolar transistor, and each energization path has one end of the solenoid coil connected to the pair of power supply terminals. And the other end is connected to the collector terminal of each bipolar transistor, and the emitter terminal of each bipolar transistor is connected to the-terminal of the pair of power supply terminals. The limiting resistor is provided between the collector of the second bipolar transistor and the other end of the solenoid coil, and the first input path constitutes the base terminal of the first bipolar transistor and constitutes the timer circuit Connected to the + terminal through a time constant resistor and capacitor, And the second input path connects the base terminal of the second bipolar transistor to the + terminal via a first specified resistor, and The zener diode or varistor is connected in parallel to the solenoid coil and connected to each of the bipolar transistors. The solenoid drive circuit according to any one of means 1 to 4, wherein the solenoid drive circuit is connected in series.

According to the means 5, when a power supply voltage is applied, an adsorption current corresponding to the plunger adsorption operation can be supplied to the solenoid coil, and when a specific time has elapsed, a holding current smaller than the adsorption current can be supplied. . When the application of the power supply voltage is stopped, each bipolar transistor is turned off. In this case, a surge voltage is generated in the solenoid coil, but since the surge voltage is not input to the base of each bipolar transistor, the bipolar transistor is prevented from being turned on based on the surge voltage. Yes.

Also, when the application of the power supply voltage is stopped, the electric charge accumulated in the capacitor is discharged through each input path. In this case, since no semiconductor element requiring a predetermined threshold voltage is provided on each input path to be in a conductive state, the charge accumulated in the capacitor is discharged without remaining. Thereby, the fluctuation | variation of the specific time through which adsorption current flows can be suppressed, and shortening of specific time can be aimed at. Therefore, power consumption can be reduced.

The circuit diagram of the solenoid drive circuit of 1st Embodiment. The timing chart for demonstrating the electric current change which flows into a solenoid coil, and operation | movement of a solenoid drive circuit. (A) Explanatory drawing for demonstrating the mode of absorption of a surge voltage, (b) Explanatory drawing for demonstrating the mode of discharge of a capacitor | condenser. The circuit diagram of the solenoid drive circuit of 2nd Embodiment.

<First Embodiment>
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a circuit diagram of a solenoid drive circuit 10 for driving a solenoid valve.

The solenoid drive circuit 10 includes a solenoid coil 11 that performs a plunger suction operation, and a suction transistor 12 (first switching element) connected in series to the solenoid coil 11. The adsorption transistor 12 is an NPN bipolar transistor. In the following description, the bipolar transistor is simply referred to as a transistor.

One end of the solenoid coil 11 is connected via a switch 13 to a + terminal 14a corresponding to one of the pair of power terminals 14a and 14b. The other end of the solenoid coil 11 is connected to the collector of the adsorption transistor 12. The emitter of the adsorption transistor 12 is connected through a diode 15 to a negative terminal 14b corresponding to the other power supply terminal. A + terminal 14 a is connected to the base of the adsorption transistor 12 through a switch 13 and a timer circuit 16. A path connecting the base of the adsorption transistor 12 and the + terminal 14a corresponds to a first input path.

The timer circuit 16 has a driving current that turns on the adsorption transistor 12 with respect to the base of the adsorption transistor 12 for a specific time after the switch 13 is turned on (after the power supply voltage is applied). Supply. Specifically, the timer circuit 16 includes a capacitor 21 and a resistor 22 (time constant resistor) connected in series to the capacitor 21. Each element is connected so that the power supply voltage from the + terminal 14 a is applied to the base of the adsorption transistor 12 through a series connection body of the resistor 22 and the capacitor 21. As a result, when the switch 13 is turned on from off and a power supply voltage (for example, + 24V) is applied from the + terminal 14a, a drive current is supplied to the base of the adsorption transistor 12 until electric charge is accumulated in the capacitor 21, The transistor 12 is turned on.

In this case, a predetermined current flows through the solenoid coil 11 via the adsorption transistor 12. The energization path via the adsorption transistor 12 corresponds to the first energization path A.

Incidentally, the solenoid drive circuit 10 includes a resistor 23 connected in series to the timer circuit 16. One end of the resistor 23 is connected to the capacitor 21, and the other end is connected to the negative terminal 14 b via the diode 15. Thereby, when the switch 13 is turned off (when application of the power supply voltage is stopped), the electric charge accumulated in the capacitor 21 is discharged through the

resistors

22 and 23. Therefore, it can be said that the

resistors

22 and 23 form a discharge path of the capacitor 21.

The resistance values of the

resistors

22 and 23 are set so that the drive current is supplied to the base of the adsorption transistor 12 when a power supply voltage is applied in a state where no charge is accumulated in the capacitor 21. Yes.

The solenoid drive circuit 10 is provided with a second energization path B through which a current smaller than a current flowing through the first energization path A flows in addition to the first energization path A as an energization path of the solenoid coil 11. Specifically, the solenoid drive circuit 10 includes a limiting resistor 31 and an NPN-type holding transistor 32 (second switching element) connected in series to the solenoid coil 11 and connected in parallel to the adsorption transistor 12. ). The limiting resistor 31 and the holding transistor 32 are connected in series. Specifically, one end of the limiting resistor 31 is connected to the collector of the holding transistor 32. The other end of the limiting resistor 31 is connected to the other end of the solenoid coil 11, and the emitter of the holding transistor 32 is connected to the − terminal 14 b via the diode 15.

The base of the holding transistor 32 is configured to be supplied with a drive current that turns on the holding transistor 32 when the switch 13 is turned on. Specifically, the solenoid drive circuit 10 includes a base current supply circuit 33 having a resistor 33a and a resistor 33b connected in series to the resistor 33a. The base current supply circuit 33 is configured such that a power supply voltage is applied. Specifically, one end of the resistor 33a is connected to the + terminal 14a via the switch 13, and the other end of the resistor 33b is connected to the diode 15. Is connected to the negative terminal 14b. The base of the holding transistor 32 is connected in parallel to the resistor 33b. The resistance values of the

resistors

33a and 33b are set so that the drive current is supplied to the base of the holding transistor 32 when the switch 13 is on. A path connecting the base of the holding transistor 32 and the + terminal 14a corresponds to the second input path, and the

resistors

33a and 33b correspond to the specified resistance.

According to this configuration, when the switch 13 is on, the drive current is supplied to the base of the holding transistor 32, and the holding transistor 32 is turned on. In this situation, when the adsorption transistor 12 is turned off, a current flows through the solenoid coil 11 via the limiting resistor 31 and the holding transistor 32. The energization path through the limiting resistor 31 and the holding transistor 32 corresponds to the second energization path B. The current flowing through the second energization path B is smaller than the current flowing through the first energization path A by the amount provided with the limiting resistor 31.

Here, when energization to the solenoid coil 11 is stopped, a surge voltage higher than the power supply voltage is temporarily generated in the solenoid coil 11. In response to the surge voltage, the solenoid drive circuit 10 is provided with a bidirectional Zener diode 40 as a surge absorbing circuit.

The bidirectional Zener diode 40 is connected in parallel to the solenoid coil 11 and is connected in series to the series connection body including the limiting resistor 31 and the holding transistor 32 and the adsorption transistor 12. The Zener voltage of the bidirectional Zener diode 40 is set to be smaller than the withstand voltage (for example, 50V) of the adsorption transistor 12 and the holding transistor 32, and is specifically set to 47V.

According to this configuration, when a surge voltage equal to or higher than the Zener voltage is generated in the solenoid coil 11, the bidirectional Zener diode 40 becomes conductive, and a surge current flows through the solenoid coil 11 through the bidirectional Zener diode 40. Thereafter, when the surge voltage becomes smaller than the Zener voltage due to the voltage drop, the bidirectional Zener diode 40 becomes non-conductive. As a result, the surge voltage is absorbed up to the Zener voltage.

The Zener voltage is set higher than the power supply voltage (24V) applied to the solenoid drive circuit 10. As a result, the bidirectional Zener diode 40 is in a non-conductive state in a situation where the power supply voltage is applied, and a predetermined current flows through the solenoid coil 11.

In order to notify that the solenoid drive circuit 10 is being driven, the solenoid drive circuit 10 is provided with a light emitting diode 50. The light emitting diode 50 has an anode connected to the + terminal 14 a via the switch 13 and a cathode connected to the − terminal 14 b via the diode 15. Thereby, the light emitting diode 50 emits light in a situation where the power supply voltage is applied.

Next, the operation of the solenoid drive circuit 10 will be described with reference to FIGS. 2A is a graph showing a change in current flowing through the solenoid coil 11, FIG. 2B is a timing chart showing ON / OFF of the switch 13, FIG. 2C is a timing chart showing ON / OFF of the adsorption transistor 12, and FIG. (D) is a timing chart showing ON / OFF of the holding transistor 32. FIG. 3A is an explanatory diagram for explaining how the surge voltage is absorbed, and FIG. 3B is an explanatory diagram for explaining how the capacitor 21 is discharged.

First, a case where the switch 13 is turned on from off will be described, and then a case where the switch 13 is turned off from on will be described.

When the switch 13 is turned on at the timing t0, charging of the capacitor 21 of the timer circuit 16 is started. In this case, a drive current is supplied to the base of the adsorption transistor 12, and the adsorption transistor 12 is turned on (see FIG. 2C). Thereby, a current flows through the first energization path A. The plunger is attracted by the current, and the solenoid valve is driven. The current (current at which the plunger suction operation is performed) is referred to as a suction current. That is, it can be said that the adsorption transistor 12 is a switching element for flowing an adsorption current to the solenoid coil 11.

As shown in FIG. 2D, when the switch 13 is turned on, a drive current is supplied to the base of the holding transistor 32, and the holding transistor 32 is turned on. In this case, since the limiting resistor 31 is provided on the second energization path B, the adsorption current flowing through the first energization path A becomes dominant.

Further, it is notified that the light emitting diode 50 emits light based on the application of the power supply voltage and the electromagnetic valve is driven.

Thereafter, the base current of the adsorption transistor 12 decreases as the amount of charge charged in the capacitor 21 increases. When the base current becomes smaller than the threshold current of the adsorption transistor 12 at the timing t1, the adsorption transistor 12 is turned off as shown in FIG. 2C, and the solenoid coil 11 is adsorbed via the adsorption transistor 12. Current stops flowing. In this case, a current flows through the second energization path B, and the position of the plunger is maintained. This current (current at which the position of the plunger is held) is referred to as holding current. That is, it can be said that the holding transistor 32 provided on the second energization path B is a switching element for flowing a holding current to the solenoid coil 11. As shown in FIG. 2A, the holding current is smaller than the adsorption current by the amount that the limiting resistor 31 is provided on the second energization path B.

From the above, the attracting current flows to the solenoid coil 11 over a predetermined time (the time from when the power supply voltage is applied until the base current of the attracting transistor 12 becomes smaller than the threshold current). When time elapses, the current flowing through the solenoid coil 11 is switched from the adsorption current to the holding current. Thereby, reduction of the power consumption which concerns on the drive of a solenoid valve can be aimed at, performing plunger adsorption | suction operation | movement.

Here, the adsorption time T1 (the time from the timing t0 to the timing t1) in which the adsorption current flows including the time of the transient phenomenon is determined by the resistance values of the

resistors

22 and 23 and the capacitance of the capacitor 21. For this reason, the adsorption time T1 can be adjusted by adjusting the resistance value and the capacitance.

Next, the case where the application of the power supply voltage is stopped will be described.

When the switch 13 is turned off at the timing t2, the energization to the solenoid coil 11 and the capacitor 21 is stopped. As a result, a surge voltage is generated in the solenoid coil 11 and the capacitor 21 is discharged. An operation based on each phenomenon will be described.

First, the surge voltage will be described. As shown in FIG. 3A, the surge voltage generated in the solenoid coil 11 is applied to the bidirectional Zener diode 40, and the bidirectional Zener diode 40 and the solenoid coil 11 constitute a closed loop circuit. Is formed. As a result, a surge current flows in the closed loop circuit until the surge voltage becomes a Zener voltage. The closed loop circuit is maintained until the bidirectional Zener diode 40 is turned off when the surge voltage is reduced to the Zener voltage.

Thereafter, at the timing t3 when the surge voltage becomes smaller than the Zener voltage, the closed loop circuit is not formed, and the surge current does not flow through the solenoid coil 11. That is, the time from when the supply voltage application is stopped (timing at t2) to when the surge voltage becomes smaller than the zener voltage (timing at t3) is the response delay time T2 of the solenoid valve.

Here, focusing on the viewpoint of absorbing the surge voltage, a configuration in which a diode is provided so that the surge voltage is applied in the forward direction instead of the bidirectional Zener diode 40 is also conceivable. However, in this case, since a surge current flows through the solenoid coil 11 until the surge voltage reaches a forward threshold voltage (about 1 V) in the diode, the response delay time T2 of the solenoid valve causes the bidirectional Zener diode 40 to It becomes longer compared to the case where it is provided.

On the other hand, according to the present embodiment, since the closed loop circuit is not formed based on the surge voltage dropping to a Zener voltage higher than the forward threshold voltage in the diode, the threshold voltage and Zener voltage of the diode are not formed. The response delay time T2 of the solenoid valve can be shortened by the difference from the above.

Further, in the situation where the closed loop circuit is not formed, the adsorption transistor 12 and the holding transistor 32 are off, so that a surge voltage corresponding to the Zener voltage is applied to each of the

transistors

12 and 32. Thereby, application of the surge voltage to the capacitor 21 and the light emitting diode 50 is suppressed. Therefore, the Zener voltage can be set high while suppressing destruction of the capacitor 21 and the light emitting diode 50.

That is, when a threshold voltage (zener voltage) at which the closed loop circuit is not formed is shortened in order to shorten the response delay time T2 of the solenoid valve, when the surge voltage corresponding to the threshold voltage is applied to the element, the element There is a risk of being destroyed. In particular, the capacitor 21 and the light emitting diode 50 are easily destroyed when a reverse voltage is applied.

On the other hand, according to the present embodiment, the adsorption transistor 12 and the holding transistor 32 are off in a situation where a surge voltage is generated, that is, in a situation where application of the power supply voltage is stopped. Thereby, a surge voltage is applied to each of the

transistors

12 and 32, and the application of the surge voltage to the capacitor 21 and the light emitting diode 50 is regulated. Therefore, the inconvenience of destruction of each element that can be caused by setting the Zener voltage high can be avoided. In other words, the adsorption transistor 12 and the holding transistor 32 can be said to be surge regulation transistors that regulate the surge voltage from being applied to the capacitor 21 and the light emitting diode 50.

In particular, the Zener voltage is set to a voltage (47V) close to the withstand voltage (50V) of each

transistor

12, 32 with respect to the reference potential (0V). As a result, the response delay time T2 can be shortened within a range in which the

transistors

12 and 32 are not destroyed.

Also, the bases of the

transistors

12 and 32 are formed so that no surge voltage is applied. Specifically, the bases of the

transistors

12 and 32 are directly connected to the + terminal 14 a without passing through the energization paths A and B of the solenoid coil 11. In other words, the input paths connecting the bases of the

transistors

12 and 32 and the + terminal 14a and the energization paths A and B of the solenoid coil 11 are independent. This suppresses the

transistors

12 and 32 from being turned on by the surge voltage. Therefore, even if the diode D is reversely connected to the solenoid drive circuit 10, the response delay time T2 of the solenoid valve does not vary.

That is, various circuits such as a controller circuit may be connected to the solenoid drive circuit 10. In this case, in order to prevent the surge voltage generated from the solenoid coil 11 from being applied to the various circuits, the diode D may be reversely connected as shown in FIG. In such a configuration, if the holding transistor 32 is turned on by the surge voltage, a closed loop circuit is formed by the holding transistor 32, the limiting resistor 31, the diode D, and the solenoid coil 11, and a surge current flows to the solenoid coil 11. It becomes. For this reason, as indicated by a two-dot chain line Z1 in FIG. 2A, there may be a disadvantage that the response delay time T2 of the electromagnetic valve becomes long although the bidirectional Zener diode 40 is provided.

On the other hand, according to the present embodiment, the base of the holding transistor 32 is connected to the + terminal 14a without passing through the energization paths A and B of the solenoid coil 11, so Surge voltage is not applied. As a result, the holding transistor 32 is turned on by the surge voltage, and the closed loop circuit is not formed. Therefore, the inconvenience can be avoided. That is, the response delay time T2 of the solenoid valve is constant regardless of other circuit configurations connected to the solenoid drive circuit 10.

Next, the discharge of the capacitor 21 will be described. As shown in FIG. 3B, a plurality (specifically, three) of

discharge paths

51, 52, and 53 are formed in the solenoid drive circuit 10. Each

discharge path

51, 52, 53 will be described below.

First, the first discharge path 51 will be described. Charge accumulated in the capacitor 21 is discharged through the light emitting diode 50.

Next, the second discharge path 52 will be described. A drive current is temporarily supplied to the base of the holding transistor 32 by the electric charge accumulated in the capacitor 21. Therefore, as shown in FIG. 2D, the holding transistor 32 is turned on for a predetermined time even after the switch 13 is turned off. Thereby, the electric charge accumulated in the capacitor 21 is discharged via the solenoid coil 11 and the holding transistor 32.

Here, semiconductor elements that require a predetermined threshold voltage to be turned on are provided on the two

discharge paths

51 and 52. Specifically, the light emitting diode 50 is provided on the first discharge path 51, and the holding transistor 32 is provided on the second discharge path 52. For this reason, the electric charge corresponding to the threshold voltage required to turn on these semiconductor elements remains without being discharged. Specifically, a charge corresponding to about 1 V remains. Since this residual charge is released by natural discharge, the discharge time required until the charge accumulated in the capacitor 21 is completely discharged becomes longer. Then, the charge 21 may remain in the capacitor 21 at the timing when the switch 13 is turned on again after the switch 13 is turned off. In this case, since the ON time of the adsorption transistor 12 varies depending on the remaining charge amount, the adsorption transistor 12 may be turned off before the plunger adsorption operation is completed. For this reason, as indicated by a two-dot chain line Z2 in FIG. 2A, it is necessary to set the adsorption time T1 longer in accordance with the change in the on-time of the adsorption transistor 12 based on the residual charge amount, thereby increasing the power consumption. There is a concern about conversion.

In contrast, the solenoid drive circuit 10 includes a closed loop circuit formed by the timer circuit 16, the resistor 23, and the base current supply circuit 33 as the third discharge path 53. Thereby, the electric charge accumulated in the capacitor 21 is discharged through the third discharge path 53 via the

resistors

33a and 33b, as shown in FIG. 3B. That is, it can be said that the

resistors

33a and 33b are discharging

resistors

33a and 33b of the capacitor 21, respectively.

Only resistors (specifically, the

resistors

22, 23, 33a, and 33b) are provided on the third discharge path 53, and no semiconductor element that requires a predetermined threshold voltage to be turned on is provided. Thereby, since the electric charge accumulated in the capacitor 21 can be completely discharged, the discharge time of the capacitor 21 can be shortened compared with the case where natural discharge is performed. Therefore, since the fluctuation of the on-time of the adsorption transistor 12 based on the residual charge amount of the capacitor 21 can be reduced, it is possible to shorten the adsorption time T1 through which the adsorption current flows. Therefore, power consumption can be reduced.

Here, since the holding transistor 32 is turned on by the discharge of the capacitor 21, as already described, if the diode D is provided, a surge current based on the surge voltage may flow through the diode D. On the other hand, the resistance values of the

discharge resistors

33a and 33b are set (lower) so that the discharge time of the capacitor 21 is shorter than the time required for the surge voltage to become the Zener voltage. As a result, as shown in FIG. 2D, at the timing when the surge voltage becomes smaller than the Zener voltage (timing at t3), the holding transistor 32 is off, so that no surge current flows. Therefore, while suitably discharging the electric charge accumulated in the capacitor 21, the inconvenience due to the discharge of the capacitor 21 (longening of the response delay time T2 of the solenoid valve that may occur when the holding transistor 32 is turned on) is caused. Can be suppressed.

According to the embodiment described above in detail, the following excellent effects are obtained.

The bidirectional Zener diode 40 is provided in parallel with the solenoid coil 11, and the adsorption transistor 12 and the holding transistor 32 are provided in series with the solenoid coil 11 and the bidirectional Zener diode 40. Thereby, when the power supply voltage is not applied, the

transistors

12 and 32 are turned off, so that the surge voltage lowered to the Zener voltage is not applied to other elements. Therefore, the Zener voltage can be set high while suppressing the destruction of the element due to the surge voltage.

The bases of the

transistors

12 and 32 were connected to the + terminal 14a without going through the solenoid coil 11. Thus, since the surge voltage is not applied to the bases of the

transistors

12 and 32, the

transistors

12 and 32 are not turned on based on the surge voltage. Therefore, even if the diode D is provided for the solenoid drive circuit 10, the response delay time T2 of the solenoid valve does not increase.

Furthermore, the base terminals of the

transistors

12 and 32 were connected to the negative terminal 14b. As a result, a third discharge path 53 is formed as a discharge path of the capacitor 21, which is not provided with a semiconductor element that requires a predetermined threshold voltage to be turned on. Therefore, the charge accumulated in the capacitor 21 is completely discharged. Can be made. Therefore, fluctuations in the on-time of the adsorption transistor 12 can be suppressed. Accordingly, since it is not necessary to set the suction time T1 to be long in response to the fluctuation, the suction time T1 can be set to be short, and power consumption can be reduced.

Second Embodiment
In the present embodiment, the configuration for absorbing the surge voltage is different from that of the first embodiment. The difference will be described with reference to FIG. FIG. 4 is a circuit diagram of the solenoid drive circuit 100 in the second embodiment. In addition, about the structure similar to the said 1st Embodiment, while attaching | subjecting the same code | symbol, the description is abbreviate | omitted.

In the first embodiment, the bidirectional Zener diode 40 is connected in parallel to the solenoid coil 11, but instead, the Zener diode 101 is connected between the base and collector of the adsorption transistor 12. Specifically, the anode of the Zener diode 101 is connected to the base of the adsorption transistor 12 and the cathode is connected to the collector of the adsorption transistor 12. As a result, the base path that is input to the base terminal of the adsorption transistor 12 via the Zener diode 101 and the first energization path A are connected.

According to such a configuration, the Zener diode 101 becomes conductive when a surge voltage larger than the Zener voltage is generated. Then, a surge current based on the surge voltage is supplied to the base of the adsorption transistor 12, and the adsorption transistor 12 is turned on. As a result, a closed loop circuit is formed via the adsorption transistor 12 and the

resistors

33a and 33b, and a surge current flows in the closed loop circuit until the surge voltage becomes a Zener voltage.

Thereafter, when the surge voltage becomes smaller than the Zener voltage, the surge current is not supplied to the base of the adsorption transistor 12, so that the adsorption transistor 12 is turned off. As a result, the surge current stops flowing through the solenoid coil 11, and the drive of the solenoid valve stops. Therefore, the response delay time T2 of the solenoid valve can be shortened. In other words, the Zener diode 101 transmits the surge voltage so that the surge current is supplied to the base of the adsorption transistor 12 in a situation where the surge voltage is larger than the Zener voltage, and the surge voltage is higher than the Zener voltage. In a small situation, it can be said that the transmission of the surge voltage is regulated.

By the way, the difference between the first embodiment and the discharge of the charge accumulated in the capacitor 21 will be described. The direction of the current flowing through the

resistors

33a and 33b is opposite between that based on the closed loop circuit and that based on the charge discharge. Therefore, when a closed loop circuit is formed, electric charges are not discharged through the

resistors

33a and 33b. For this reason, after the surge voltage becomes lower than the Zener voltage (after the closed loop circuit is no longer formed), the complete discharge of the capacitor 21 is completed after a predetermined period.

Note that the Zener diode 101 may be reversely connected between the collector and emitter of the adsorption transistor 12. Specifically, the cathode of the Zener diode 101 is connected to the collector, and the cathode of the Zener diode 101 is connected to the emitter. In this case, a closed loop circuit through the Zener diode 101 and the

resistors

33a and 33b is formed until the surge voltage becomes the Zener voltage without the adsorption transistor 12 being turned on.

The present invention is not limited to the description of the above embodiments, and may be implemented as follows, for example.

(1) In each of the above embodiments, the bidirectional Zener diode 40 or the Zener diode 101 is provided to reduce the surge voltage to the Zener voltage. However, the present invention is not limited to this, and a varistor may be provided instead. .

(2) In each of the above embodiments, an NPN transistor is used as a switching element. However, the present invention is not limited to this. For example, a PNP transistor may be used. In this case, the connection relationship is set according to the PNP transistor. Further, the switching element is not limited to a transistor, and another switching element such as a MOSFET may be used.

(3) In each of the above embodiments, a separate path for supplying current to the light emitting diode 50 is provided, but the present invention is not limited to this. For example, the resistor 33a or the resistor 33b may be replaced with the light emitting diode 50. Thereby, simplification of a structure can be achieved. However, if attention is paid to the fact that the capacitor 21 can be completely discharged, the configuration in which the resistor 33a or the resistor 33b is provided is superior.

(4) Another solenoid drive circuit and other peripheral circuits may be connected in parallel to the solenoid drive circuit 10. Even in such a case, the response delay time T2 of the solenoid valve is constant regardless of the circuit configuration of other circuits.

DESCRIPTION OF SYMBOLS 10 ... Solenoid drive circuit, 11 ... Solenoid coil, 12 ... Adsorption transistor as a switching element, 14a ... + terminal as one power supply terminal, 14b ...-terminal as the other power supply terminal, 16 ... Timer circuit, 21 ... Capacitor 31 ... Limiting resistor, 32 ... Holding transistor as switching element, 33 ... Base current supply circuit, 40 ... Bidirectional Zener diode, 51-53 ... Discharge path, 101 ... Zener diode, A, B ... Discharge path.

Claims

A solenoid coil that generates a magnetic field when energized and drives a solenoid valve;
A switching element connected in series to the solenoid coil;
With
The series connection body of the solenoid coil and the switching element is connected to a pair of power supply terminals for applying a power supply voltage,
In the solenoid drive circuit in which the energization path of the solenoid coil is formed by turning on the switching element in a state where the power supply voltage is applied, and the solenoid coil is energized.
As the switching element,
A first switching element that is turned on until a predetermined time elapses after the power supply voltage is applied;
A second switching element that is connected in parallel to the first switching element and is turned on while the power supply voltage is applied;
With
As the energization path of the solenoid coil,
A first energization path through the first switching element;
A second energization path through the second switching element;
Is provided,
On the second energization path, a limiting resistor is provided so that a current flowing on the second energization path is smaller than a current flowing on the first energization path,
Apart from the energization paths,
A first input path connecting the input terminal of the first switching element and one of the pair of power supply terminals;
A second input path connecting the input terminal of the second switching element and the one power supply terminal;
Are provided in parallel,
A timer circuit that is provided on the first input path and supplies driving power for turning on the first switching element to the first switching element over the specific time;
A surge absorption circuit that has a Zener diode or a varistor and absorbs a surge voltage generated when the energization to the solenoid coil is stopped to a threshold voltage at which the Zener diode or the varistor becomes conductive;
With
A solenoid drive circuit characterized in that a surge voltage absorbed up to the threshold voltage is applied to each of the switching elements.
The surge absorbing circuit is connected in parallel to the solenoid coil, and is connected in series to the switching elements.
2. The solenoid drive circuit according to claim 1, wherein the input paths and the energization paths are independent so that the surge voltage is not transmitted to the input paths.
On the second input path, a defining resistor that defines driving power supplied to the input terminal of the second switching element is provided,
The timer circuit includes a time constant resistor and a capacitor connected in series to the time constant resistor,
A closed loop including the specified resistor, the time constant resistor and the capacitor is formed by connecting the input paths,
3. The solenoid drive circuit according to claim 1, wherein the closed loop constitutes a discharge path through which electric charges accumulated in the capacitor are discharged. 4.
The resistance value of the specified resistor is set so that the time required to complete the discharge of the charge accumulated in the capacitor is shorter than the time required for the surge voltage to be absorbed to the threshold voltage. The solenoid drive circuit according to claim 3.
The first switching element is an NPN-type first bipolar transistor,
The second switching element is an NPN-type second bipolar transistor;
Each energization path has one end of the solenoid coil connected to the positive terminal of the pair of power supply terminals, the other end connected to the collector terminal of each bipolar transistor, and the emitter terminal of each bipolar transistor connected to the pair of power supply terminals. It is formed by connecting to the negative terminal of the power supply terminal of
The limiting resistor is provided between the collector of the second bipolar transistor and the other end of the solenoid coil,
The first input path connects the base terminal of the first bipolar transistor to the + terminal through a time constant resistor and a capacitor constituting the timer circuit and to the − terminal through a resistor. It is formed with
The second input path is formed by connecting the base terminal of the second bipolar transistor to the + terminal via a first specified resistor and to the − terminal via a second specified resistor. Is,
5. The solenoid according to claim 1, wherein the Zener diode or the varistor is connected in parallel to the solenoid coil and is connected in series to each of the bipolar transistors. Driving circuit.