JPH03149477A - Solenoid changeover valve driving circuit - Google Patents

Abstract

PURPOSE:To stabilize shockless operation by continuously producing a hold output of a prescribed voltage level from the start of a changeover command signal, and by adding it to an increasing pattern signal for driving a solenoid. CONSTITUTION:When a changeover command light signal is input into a terminal 26a, it is converted into an electric signal by an input circuit 24a to reset a (b)-side signal hold circuit 20b, and also the switch 34a of an input changeover circuit 22a is turned off, and the hold output of a prescribed voltage value being output from a signal hold circuit 20a and the increasing pattern output from a pattern producer 18 are added by an add-substract circuit 16. Since an output changeover circuit 12 turns off Qb, and turns of Qa by a changeover command, a solenoid (a) is subjected to PWM drive by the output from the add-substract circuit 16 via a current drive circuit 14. When the load reaches the stop position, a stop signal is input into an input circuit 24c to forcibly stop the operation of the pattern producer 18. Thus, shockless operation can be stably realized.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a drive circuit for controlling the excitation current of an electromagnetic switching valve that switches open/close of a fluid flow path using a switching command signal, and particularly relates to a drive circuit for controlling an excitation current of an electromagnetic switching valve that switches open/close of a fluid flow path. This invention relates to an electromagnetic switching valve drive circuit that controls the excitation current to be gradually increased or decreased during switching in order to reduce fluid shock during switching.

[Prior Art] In electromagnetic switching valves that open and close fluid flow paths, if the valve body moves suddenly, a pressure shock is generated in the fluid, causing unexpected trouble in the equipment, so various countermeasures have been taken in the past. , so-called shock prevention measures are taken.

Typical conventional shock prevention measures include modifying the shape of the spool valve driven by a solenoid device and changing the switching speed of the spool valve by throttling the fluid flow generated by the movement of the spool valve. Regardless of which method is used, this method not only complicates the mechanical structure, but also consists of fixed control elements that cannot be variably adjusted.
The switching time of the spool valve varies due to differences in operating pressure, flow rate, and load conditions, and satisfactory results are often not obtained.

This drawback is due to the use of solenoid devices with parallel attraction force characteristics, such as proportional electromagnetic control valves, and the shape of the flow path opening/closing control section so that the opening degree of the opening/closing flow path changes smoothly according to the stroke. The problem is solved by using a spool valve assembly and electrically controlling the spool valve to move slowly by gradually increasing and decreasing the excitation current of the solenoid device when it is turned on and off. Patent application No. 62-217035 (Unexamined patent application No. 64-0511)
890 Calyx Publication).

In other words, in the drive circuit of this electrically controlled shockless electromagnetic switching valve, a time constant circuit is individually provided for each of the rising edge when on and the falling edge when turning off in response to a step-like switching command signal. In addition, in combination with a comparator circuit, when the output voltage level of the on-time constant circuit exceeds a predetermined value, the power supply charge is accumulated in the off-time constant circuit, and this accumulation is performed when off. By discharging the charge with the off-time constant circuit,
Obtain the desired gradual increase/decrease signal at each on/off time,
This gradual increase/decrease signal pulse-width modulates the power switching element of the solenoid excitation current, making it possible to slowly switch the spool valve.Also, by introducing a resistor voltage divider circuit into the time constant circuit for turning on, An offset corresponding to the partial pressure ratio is given to the gradual increase/decrease signal at the moment of time and moment of off, thereby shortening the time through which the spool valve flow path opening/closing control section passes through the overlap section until it begins to open and close. This makes it possible to shorten the so-called dead zone time.

[Problem to be Solved by the Invention 1] In the drive circuit of the electrically controlled shockless electromagnetic switching valve mentioned above in the conventional example, the output level of the time constant circuit for on-time is detected by a comparator, and Since this method supplies charge for current control from the power supply and stores it in the off-time constant circuit, if the time constant of the on-time constant circuit is set to a large value, the off-time Charge accumulation in the time constant circuit used for this purpose may not be sufficient, and there is a risk that shockless operation during off-time may be impaired when operating with a short switching cycle.

Also, regarding the offset voltage when on and off, the time constant circuit for on is combined with a voltage divider circuit to provide the same on/off voltage as an offset, so the magnitude of the offset can be adjusted separately for on and off. The problem remained that it was not possible.

In addition, with this method, due to circuit configuration reasons, it is necessary to provide an independent switching control circuit for each solenoid device in order to use it for dual solenoid type electromagnetic switching valves, so there are few common circuit parts and the circuit configuration becomes complex and large. I hated doing that.

Furthermore, in the conventional method, the switching shock when off is performed by controlling the excitation current of the solenoid device to gradually decrease using a time constant pattern, so even if the time for the flow rate to decrease is constant, the load pressure changes or the oil temperature changes. When this happens, this appears as a change in the flow rate, which causes the problem that the stop position of the load actuator changes.

Therefore, an object of the present invention is to provide an electromagnetic switching valve drive circuit that can solve these remaining problems.

[Means for solving the problem] In the electromagnetic switching valve drive circuit according to the invention according to claim 1,
In order to solve the above-mentioned problem, an electromagnetic switching valve drive circuit is provided which controls the switching operation of the electromagnetic switching valve by controlling on/off the excitation current of the solenoid device of the electromagnetic switching valve via a power switching element in response to a switching command signal. , a hold circuit that immediately generates a hold output at a predetermined level when receiving the switching command signal and continues to generate the hold output until the arrival of a reset signal even after the switching command signal disappears; a pattern generator that generates a signal output with a pattern that gradually increases and decreases in the downward direction; and an adder circuit that outputs a sum signal of the signal output of the rainbow pattern generator and the hold output of the hold circuit at the rising edge of the switching command signal. and switching the input conditions for the hold output from the hold circuit in the adder circuit means so that when the switching command signal disappears, the addition signal from the adder circuit means until then is substantially reduced in a stepwise manner. a manual switching circuit, and stopping the drop in the signal output level of the pattern generator when the level of the addition signal from the addition circuit means drops to a preset comparison reference level after the switching command signal disappears; a comparator circuit that fixes and holds the pattern generator at a relatively low level; a stop circuit means that forcibly resets the pattern generator by giving a stop command signal to the pattern generator from the outside; and a current drive circuit that drives switching of the power switching element using a switching control signal that is pulse-width modulated by outputting an added signal.

In addition, the electromagnetic switching valve drive circuit according to the invention set forth in claim 2 is provided with the configuration according to the invention set forth in claim 1 for a double solenoid type electromagnetic switching valve that performs bidirectional switching by a pair of solenoid devices. In this case, the hold circuit includes a first hold circuit that receives a first switching command signal for one solenoid device, and a second hold circuit that receives a second switching command signal for the other solenoid device. The first hold circuit is supplied with the second switching command signal as a reset signal, the second hold circuit is supplied with the first switching command signal as a reset signal, and the second holding circuit is supplied with the first switching command signal as a reset signal. A pattern generator, the adder circuit means, the comparator circuit, and the stop circuit means are shared by the first and second hold circuits, and between the current drive circuit and the power switching element, the first When the second hold circuit is generating an output, the output of the current drive circuit is applied to only the one solenoid device, and when the second hold circuit is generating an output, the output of the current drive circuit is applied to the one solenoid device. An output switching circuit is provided that is controlled by the outputs of the first and second hold circuits so as to apply only to the other solenoid device.

[Function] In the electromagnetic switching valve drive circuit of the present invention, the power switching element that switches and controls the solenoid excitation current of the electromagnetic switching valve is finally pulse-driven by the pulse output of the current drive circuit, and this pulse output is a switching command. At the rise and fall of the signal, the average current is controlled to gradually increase or decrease by pulse width modulation.

Now, the switching command signal given from the outside via a signal line in the form of a minute current signal or an optical signal is a step voltage signal, and when it rises, it starts supplying the solenoid excitation current, and when it falls, it excites the solenoid. This is to start cutting off the current.

In the electromagnetic switching valve drive circuit according to the invention as claimed in claim 1, when this switching command signal is given to start excitation of the solenoid device in order to move the spool valve in the direction of opening the flow path against the spring. , the hold circuit immediately
- A hold output is generated at a predetermined level, and even after the switching command signal disappears, the hold output continues to be generated until the arrival of a separately given reset signal. In this case, the reset signal may be provided separately from the outside for a solenoid type electromagnetic switching valve, or may be applied after a predetermined time by an appropriate internal timer circuit. In the case of a valve, it is also possible to use a switching command signal for one solenoid device to reset a hold circuit belonging to the other solenoid device.

On the other hand, the pattern generator generates a signal output with a pattern that gradually increases and decreases at the rising edge and falling edge in response to the switching command signal, and the starting points of the rising edge and the falling edge of this signal output are synchronized with those of the switching instruction signal. There is. This pattern generator uses one whose time constant can be set and adjusted separately so that the rising and falling patterns of gradual increase and gradual decrease each change with a predetermined time constant. can be easily configured using existing technology.

summing circuit means receives the signal output of the pattern generator and the hold output of the hold circuit as summing inputs;
At the rising edge of the switching command signal, a sum signal of the signal output of the pattern generator and the hold output of the hold circuit is output. That is, this addition signal rises in a stepwise manner by an offset amount corresponding to the value of the hold output at the same time as the switching command signal rises, and then
It gradually increases as the signal output of the pattern generator changes, and reaches a certain level after a predetermined rise time constant.

The addition signal output from the addition circuit means that changes in such a signal pattern is input to the current drive circuit, and the current drive circuit adjusts the pulse width so as to gradually increase the pulse width in accordance with the level change of the addition signal output. A modulated pulse output is generated, and the switching control of the power switching element is performed by this pulse output.

Therefore, the average excitation current to the solenoid first becomes a current value corresponding to the offset amount at the same time as the switching command signal rises, and then becomes a current that gradually increases as the signal output of the pattern generator changes. In response to this, the spool valve of the electromagnetic switching valve begins to move at an initial speed corresponding to the offset amount, passes through the overlap part of the flow path opening/closing control section, and after reaching the position where the opening/closing control section begins to open, the moving speed increases. gradually increases toward the switching position.

Conversely, when the switching command signal is turned off and disappears in order to return the spool valve from the switching position to its original position in order to close the flow path, the manual switching circuit removes the previous addition signal from the addition circuit means. The input conditions for the hold output from the hold circuit in the adder circuit means are switched so that the hold output is substantially reduced stepwise. At this time, the hold circuit still produces a hold output, but the input switching circuit, for example, separately supplies this hold output to the adder circuit means as a subtraction input. In the adder circuit means, the previously applied hold output as the addition input is stepwise subtracted by the newly applied hold output as the subtraction input, and this reduction becomes the off-state offset amount. In this case, by adjusting the gain and polarity of both hold outputs in various settings, the off-state offset amount can be independently and arbitrarily set.

Therefore, the output from the adder circuit means decreases stepwise by the off-time offset amount at the same time as the switching command signal disappears, and then gradually decreases in accordance with the gradual decrease pattern of the signal output of the pattern generator. In the same manner as described above, the spool valve of the electromagnetic switching valve begins to move at an initial speed corresponding to the off-state offset amount, passes through the overlap part of the flow path opening/closing control section, and reaches a position where it begins to throttle the flow rate flowing to the opening/closing control section. After reaching this point, it returns to its original position while gradually increasing its movement speed.

In general, in switching valves, when the spool valve is on or off, the spool valve starts moving from the fully closed or open state of the flow control section, and it takes longer than in the case of a proportional control valve to actually start changing the flow rate. Move distance B. When this moving distance is called the overlap distance, the overlap distance when on and off may be the same or different depending on the switching valve, and the relationship between the output torque of the solenoid device, the force of the valve return spring, and the flow force. Since the values often do not match, it is significant to be able to individually set and adjust the offset amount for each on-time and off-time as described above.

Now, when the level of the gradually decreasing signal outputted from the adder circuit means falls below the comparison reference voltage level of the comparator circuit after the switching command signal disappears in the OFF state, the comparator circuit supplies a hold signal to the pattern generator to The drop in the signal output level of the pattern generator is stopped at that point, and thereafter the signal output is maintained at that relatively low level. As a result, the excitation current flows at a constant low current, and the spool valve controls the flow path in the low flow rate range, so that the load actuator operates at a constant speed in the low speed range immediately before deceleration and stop. When the load reaches the position where it should be stopped, a stop command signal is given from, for example, a position detector installed at the target stop position, and in response to this, the stop circuit means externally stops the pattern generator. Forcibly reset the pattern generator by giving a command signal.

As a result, the signal output of the pattern generator disappears, and the output of the summing circuit means also disappears, so the current drive circuit cuts off the power switching element and cuts off the excitation current, and the spool valve immediately springs back to the flow cutoff position. The load actuator will stop at a predetermined stop position.

In the electromagnetic switching valve drive circuit according to the invention according to claim 2,
Since the dual solenoid type electromagnetic switching valve performs bidirectional switching by a pair of solenoid devices, the hold circuit receives a first switching command signal for one solenoid device, and a first hold circuit receives a first switching command signal for one solenoid device, and a first hold circuit receives a first switching command signal for one solenoid device, and a first hold circuit receives a first switching command signal for one solenoid device. and a second hold circuit that receives a second switching command signal for. The first hold circuit receives the second switching command signal as a reset signal, and the second hold circuit receives the first switching command signal as a reset signal, thereby alternately suppressing the rising edge of the switching command signal of the other party. The hold circuit is reset by

The pattern generator, the adder circuit means, the comparator circuit, and the stop circuit means are shared by the first and second hold circuits, each of which has a single pattern generator, adder circuit means, comparator circuit, and stop circuit. The means performs shockless drive control and fixed position stop control for the pair of solenoid devices.

the current drive circuit is also shared by both solenoid devices;
Therefore, an output switching circuit is interposed between the current drive circuit and the power switching element. This output switching circuit is controlled by the outputs of the first and second hold circuits, and when the first hold circuit is producing an output, the excitation current is controlled by the output of the current drive circuit. is applied only to the one solenoid device, and when the second hold circuit is producing an output, it is applied only to the other solenoid device.The solenoid excitation current is gradually increased by this barber switching command signal. - The gradual reduction control itself is the same as in the case of the invention described in claim 1 above.

In order to clarify the features and advantages of the present invention, embodiments of the present invention will be described below with reference to the drawings.

[Example] A: Circuit configuration Figure 1 is a block circuit diagram showing the basic configuration of a drive circuit according to an embodiment of the present invention for a dual-solenoid type electromagnetic switching valve, in which solenoid devices a and b are powered by 24 V DC. It is connected to a power source via power switching transistors Qa and Qb, and the excitation current is controlled by the switching operation of these power switching transistors.

A control electrode of each power switching transistor Qa, Qb is connected to an output terminal of a pulse width modulation current drive circuit 14 via an output switching circuit 12.
Current feedback is applied from both solenoid devices 1a and 1b via a current feedback circuit 15, and stabilization is achieved against changes in resistance value due to temperature rise of the solenoid devices and changes due to power supply voltage fluctuations.

The output switching circuit 12 includes switching elements 12a and 1 on the base sides of the power switching transistors Qa and Qb on the a side and the b side to selectively turn off these transistors.
2b, and these switching elements include a hold circuit 20a on the a or b side to which each belongs, as will be described later.
When the solenoid device a on the a side is energized under the control of the hold output of 20b, the switching element 12
When the solenoid device on the b side is energized, the switching element 12a is used to turn off the transistor Qa.

Specifically, the current drive circuit 14 can be configured with a voltage-controlled variable pulse width oscillator circuit and a base drive circuit that generate a PWM waveform output with a variable pulse width that changes according to the voltage level of the human input signal, and has a high input voltage level. This is a pulse width modulation device that generates a pulse output whose pulse width becomes wider as the pulse width increases.

An input signal to the current drive circuit 14 is given from an adder/subtracter circuit 16, and in this embodiment, the adder/subtracter circuit 16 has three addition input terminals and two subtraction input terminals. A signal output from the pattern generator 18 is input to one of the addition input terminals, and a solenoid device a is input to the remaining two addition input terminals.
The hold outputs from the signal hold circuit 20a belonging to the solenoid device and the signal hold circuit 20b belonging to the solenoid device are each manually input. Further, hold circuits 20a and 20 are connected to each subtraction input terminal via input switching circuits 22a and 22b, respectively.
The hold output from b is input separately. Each of these addition input terminals and subtraction input terminals is gain adjustable.

One hold circuit 20a receives a switching command signal from the input circuit 24a hl, and the other hold circuit 20b receives another switching command signal from another input circuit 24b, and each holds a predetermined level at the same time as the switching command signal rises. It generates an output and then holds the hold output until it is reset by a reset signal. The output of each hold circuit becomes an addition or subtraction input to the addition/subtraction circuit 16 as described above, and is further applied to the output changeover switching element 12a or 1 belonging to the other side of the solenoid device a or b to which it belongs.
This becomes a control signal for 2b.

The input circuits 24a and 24b are composed of, for example, a photocoupler and a waveform shaping circuit, and one of the input circuits 24a receives a step-like minute current signal applied to the switching signal input terminal 26ae for the solenoid device a or externally applied via an optical fiber. The other input circuit 24b converts the optical signal into an electrical signal, shapes it, and outputs it. It converts the optical signal given from the outside into an electrical signal, shapes it, and outputs it.

The switching command signal output from one input circuit 24a is given to the pattern generator 18 and one manual switching circuit 22a in addition to one hold circuit 20a, and is also given as a reset signal to the other hold circuit 20b. Similarly, the switching command signal output from the other input circuit 24b is given to the pattern generator 18 and the other input switching circuit 22b in addition to the other hold circuit 20b, and is further applied to the other hold circuit 20a for resetting. given as a signal.

The other input terminal 28c and input circuit 24C receive an optical signal from an external stop position detector (limit switch, etc.) of a load actuator, generate a stop command signal, and send this to the pattern generator 18. This is to force the pattern generator to reset at that point. In this embodiment, the input circuit 24c also consists of a photocoupler and a waveform shaping circuit.

The comparison circuit 36 receives a fixed high potential 44 or the output of the addition/subtraction circuit 16 via a switching circuit 42 at one input 36a, and receives a preset comparison reference voltage 38 at the other input 36b.
When the human power 36a is at a higher potential than the input 36, a hold signal is not output, and when the - input 36a is at a lower potential than the human power 36, a hold signal is output and the output level of the pattern generator 1B is set at that point. fixed at the level of In this case, the switching circuit 42 connects the input 36a of the comparison circuit 36 to the high potential 44 side by the output of the NOR circuit 40 while any switching command signal output from the input circuits 24a, 24b is present. When the switching command signal disappears, the output of the NOR circuit 40 is inverted and the input 36a is connected to the output side of the addition/subtraction circuit 16.

The pattern generator 18 has an on-time adjuster 28a for the rising edge of the switching command signal from one input circuit 24a, an off-time adjuster 29a for the falling edge of the switching command signal from one input circuit 24a, and an on-time regulator 28a for the rising edge of the switching command signal from the other input circuit 24b. Adjuster 28b and off-time adjuster 2 for falling
9b, so that when each switching command signal is manually inputted, a smooth gradual increase/decrease badan signal output is produced by each of these regulators.

Further, when this pattern generator 18 receives a stop command signal from the input circuit 24c as described above, it is immediately reset and cuts off the signal output, or when it receives a hold signal from the comparison circuit described above, it outputs the signal at that point. It has a function to maintain the signal output level.

The input switching circuit 22a includes a control element 32a and a switching element 34a, and when a switching command signal is given from the input circuit 24a, the associated hold circuit 20a
The hold output from the adder/subtractor circuit 16 is cut off from being supplied to the subtraction input terminal of the adder/subtracter circuit 16, and when the switching command signal it receives is turned off and disappears, the associated hold circuit The hold output of 20a is supplied to the subtraction input terminal of the addition/subtraction circuit 16.

The other input switching circuit 22b4) is similar to the other input switching circuit 22b4), and corresponding elements are indicated by corresponding symbols with a suffix b, so a detailed explanation will be omitted, but the operation is based on the switching command signal for the solenoid device. It should be noted that this is done by

B: Explanation of Operation FIG. 2 shows waveforms of various parts for explaining the operation of the circuit of this embodiment having the above-mentioned circuit configuration.

In FIG. 2, (A) is the switching command signal waveform from the input circuit 24a, (B) is the signal output waveform of the pattern generator 18, and (C) is the signal output from the hold circuit 20a or 20b to the addition input terminal of the addition/subtraction circuit 16. Given the hold output waveform,
(D) is a hold output waveform applied from the hold circuit 20a or 20b to the subtraction input terminal of the addition/subtraction circuit 16;
) is the output waveform of the addition/subtraction circuit 16, (F) Gf NOR circuit 4
0, (G) is the hold signal output waveform from the comparison circuit 36, and (H) is the stop command signal waveform from the input circuit 24c.

Now, to explain the operation when the switching signal of the solenoid device a arrives at the input terminal 268, the input terminal 26a
The optical signal given to the input circuit 24a is converted into an electric signal by the input circuit 24a, and the waveform is shaped into a step-like switching command signal as shown in FIG. 2 (A).
1 pattern generator 1B, the manual switching circuit 22a, and the NOR circuit 40, and at the same time, the hold circuit 20b on the side is set. As a result, the NOR circuit 40 (F
), the output is stopped as shown in FIG. I'm letting you do it.

The hold circuit 20a on the a side immediately generates a hold output of the set voltage value shown by Va in FIG. The hold output Va continues to be held until a switching command signal (switching command signal) is received. In response to this hold output, the output switching circuit 12 keeps the power switching transistor Qb on the side in a cut-off state by the switching element 12b on the b side while the hold output exists.

The manual switching circuit 22a cuts off the subtraction input terminal of the addition/subtraction circuit 16 from the hold circuit 20a via the control element 32a and the switching element 34a at the same time as the switching command signal rises, and maintains this state until the switching command signal disappears.

The pattern generator 18 starts producing a pattern signal output as shown in FIG. 2 (B) at the rising edge of the switching command signal.
The rise is a gradual increase pattern in which the output level gradually increases according to the time constant set by the on-time adjuster 28a.

The adder/subtracter circuit 16 receives the hold output Va of the hold circuit 20a at the same time as the switching command signal rises to one of its addition input terminals, and receives the gradual increase pattern signal output from the pattern generator 18 to another addition input terminal. Therefore, the added output is a signal that rises steeply by Va at the same time as the switching command signal rises, as shown in (E) in FIG. becomes.

The current drive circuit 14 generates a pulse output with a PWM waveform while gradually widening the pulse width in accordance with the rise in the level of the output signal from the addition/subtraction circuit 16.

As described above, in the output switching circuit 12, in this case, the switching element 12b receives the hold output from the hold circuit 20a on the a side, and this hold output causes the switching element 12b to switch the base N of the power switching transistor Qb. The transistor Qb is controlled to be kept in a cut-off state.

Therefore, the output pulse of the current drive circuit 14 pulse-drives only the power switching transistor Qa, and only the transistor Qa is operated by the switching control signal having the PWM waveform of the gradual increase pattern as described above.

The excitation current supplied to the solenoid device a by the transistor Qa flows at the average current value of the offset amount corresponding to the hold output level Va at the same time as the switching command signal rises, so that the spool valve passes through the overlap portion at the corresponding speed. do.

The average value of the excitation current is then gradually increased in an increasing pattern by the pattern generator 18, and therefore, by setting the hold output level appropriately, the spool valve can, for example, gradually increase its speed from the position where it begins to open the flow path. The flow path will open without any shock.

When the switching command signal is turned off and the spool valve is returned to its original position by a return spring, for example, the manual switching circuit 22a is connected to the subtraction input terminal of the addition/subtraction circuit 16 at the same time as the switching command signal falls. As shown, a hold output of voltage level vb is given, and as a result, the output level of the adder/subtractor circuit 16 drops steeply by the subtracted value vb, as shown in FIG. 2(E).

Next, the signal output of the pattern generator 18 gradually decreases according to the time constant set by the off-time adjuster 29a, and the output of the adder/subtractor circuit 16 also gradually decreases accordingly.

After this switching command signal is turned off, the reset signal of the hold circuit 20b on the b side disappears, so that a switching command signal on the b side can be applied at any time thereafter.

In response to such a steep fall in the level vb and the subsequent gradual decrease pattern of the signal input, the current drive circuit 1'4 controls the switching of the power switching transistor Qa accordingly, so that the average excitation current is initially offset. There is a sudden drop corresponding to the amount vb, and then a gradual decrease according to the gradual decrease pattern of the pattern generator 18.

As a result, the spool valve is returned by the force of the return spring, but the force of the opposing solenoid device decreases in accordance with the decreasing pattern of its excitation current, so that the spool valve's movement is initially at a speed corresponding to the offset amount vb. Then, the speed is gradually increased in accordance with the excitation current value that gradually decreases from the position where the flow path starts to be throttled, and the flow path opening/closing portion is closed without fluid shock.

Here, as the switching command signal turns off, the NOR circuit 40 switches the switching circuit 42, and therefore the input 3 of the comparison circuit 36
The output voltage of the adder/subtractor circuit 16 is manually input to 6a.

The output voltage level of the adder/subtractor circuit 16 gradually decreases according to the gradual decrease pattern generated by the pattern generator 18, and when it becomes below the level of the reference voltage 38, the comparator circuit 36 outputs a hold signal. At that point, the pattern generator 18 has its output level fixed by this hold signal, and as a result,
Thereafter, the output of the addition/subtraction circuit 16 will also be at a constant level. As a result, the solenoid excitation current by the power switching transistor Qa whose switching is controlled via the current drive circuit 14 becomes a constant value, and the switching valve spool is in a balanced state with a low flow rate flowing near the end of the process of closing the flow path. As a result, the load actuator continues to move slowly at a low speed just before deceleration to a stop. When the load reaches the stop position, a position detector (not shown) gives a stop signal to the input terminal 26c, which causes the input circuit 24c to give a stop command signal as shown in FIG. 2(H) to the pattern generator 16. Force a reset. When the pattern generator 16 is reset, the output of the addition/subtraction circuit 16 also disappears, the power switching transistor Qa is also cut off by the current drive circuit 14, the solenoid excitation current is cut off, and the spool valve is returned to its final return position by the spring force. It turns out.

Note that the a-side hold circuit 20a is reset when a switching signal arrives at the b-side input terminal 26b.
This is done when a switching command signal is generated from b.

In addition, the operation of the circuit on the b side is almost the same, and in that case,
The pattern generator 1B, addition/subtraction circuit 16, comparison circuit 36, stop command input circuit 24c, current drive circuit 14, etc. are shared with the a side.

[Effects of the Invention] As described above, according to the present invention, since a hold circuit is provided that continuously generates a hold output at a predetermined voltage level from the rising edge of the switching command signal, shockless operation with a short switching cycle is possible. can be realized stably, and the amount of offset can be adjusted individually to reduce the dead zone time due to passing through the overlap section in each case of on/off, and even when used in a dual solenoid type electromagnetic switching valve, there are many common parts of the circuit. In addition to being able to achieve this with a small and simple circuit configuration, the load can be moved at low speed just before stopping, and then forced to complete the stop position using an external stop command signal, so that the stop position of the load can be accurately stopped at a predetermined target position when the load is off. It can be turned off.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing the configuration of a drive circuit according to an embodiment of the present invention when applied to a double-sided solenoid type electromagnetic switching valve, and Fig. 2 is a diagram showing waveforms of each part for explaining operation. be. (Explanation of symbols of main parts) a, b: Solenoid device, Qa, Qb: Power switching transistor, 12: Output switching circuit, 14:
Current drive circuit, 16: Addition/subtraction circuit, 1, 8: Pattern generator, 20a, 20b: Hold circuit, 22a, 22
b: Manual switching circuit, 24a, 24b: Input circuit, 24c
: Stop command signal input circuit, 26a, 26b: Input terminal, 26c: Stop signal input terminal, 36: Comparison circuit.

Claims (1)

[Scope of Claims] 1. An electromagnetic switching valve drive circuit that controls the switching operation of the electromagnetic switching valve by controlling on/off the excitation current of a solenoid device of the electromagnetic switching valve via a power switching element in response to a switching command signal, a hold circuit that immediately generates a hold output at a predetermined level when receiving the switching command signal and continues to generate the hold output until a reset signal arrives even after the switching command signal disappears; a pattern generator that generates a signal output in a pattern that gradually increases and decreases at a rate of 1 to 2; addition circuit means that outputs a sum signal of the signal output of the pattern generator and the hold output of the hold circuit at the rising edge of the switching command signal; an input switching circuit that switches input conditions for the hold output from the hold circuit in the addition circuit means so that when the switching command signal disappears, the addition signal from the addition circuit means until then is substantially reduced in a stepwise manner; and, when the level of the addition signal from the addition circuit means drops to a preset comparison reference level after the switching command signal disappears, the signal output level of the pattern generator stops decreasing to a relatively low level. a comparison circuit for holding the pattern generator fixed at a level; stop circuit means for forcibly resetting the pattern generator by giving a stop command signal to the pattern generator from the outside; and the addition signal output from the addition circuit means. An electromagnetic switching valve drive circuit comprising: a current drive circuit that drives switching of the power switching element using a switching control signal pulse width modulated by the switching control signal. 2. The electromagnetic switching valve drive circuit according to claim 1, for a dual solenoid type electromagnetic switching valve that performs bidirectional switching by a pair of solenoid devices, wherein the hold circuit is a first solenoid switching valve for one solenoid device. A first hold circuit receives a switching command signal for the other solenoid device, and a second hold circuit receives a second switching command signal for the other solenoid device, and the first hold circuit receives the second switching command signal. signal is given as a reset signal, the first switching command signal is given to the second hold circuit as a reset signal, and the pattern generator, the addition circuit means, the comparison circuit, and the stop circuit means and a second hold circuit, and between the current drive circuit and the power switching element, when the first hold circuit is producing an output, the output of the current drive circuit is connected to the first and second hold circuits. control by the outputs of the first and second hold circuits so that the output of the current drive circuit is applied only to the other solenoid device, and when the second hold circuit is producing an output, the output of the current drive circuit is applied only to the other solenoid device. 1. An electromagnetic switching valve drive circuit characterized by being provided with an output switching circuit.