JPH03149478A - Solenoid changeover valve driving circuit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

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 is suddenly driven, 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.

The typical conventional shock prevention measure is a solenoid device! This is done by devising the shape of the spool valve that is controlled by MwJ, or by changing the switching speed of the spool valve by throttling the fluid flow generated by driving the spool valve, but this method does not require the complexity of the mechanical structure. Not only that, but since it is composed of fixed control elements that cannot be variably adjusted, the switching time of the spool valve fluctuates due to differences in working 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 slowly drive the spool valve by gradually increasing and decreasing the excitation current of the solenoid device when it is turned on and off. Patent application No. 82-217035 (Japanese Patent Application No. 64-05889)
Publication No. 0).

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.

[WI problem to be solved by the invention] In the drive circuit of the electrically controlled shockless electromagnetic switching valve mentioned in the conventional example mentioned above, the output level of the time constant circuit for on-time is detected by a comparator, and the output level after on-time is detected by a comparator. 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 system, the switching shock when the spool valve is turned off is controlled by gradually reducing the excitation current of the solenoid device using a time constant pattern until the spool valve switches and stops at the switching return position. Even after the flow path opening/closing control section is closed, it is subject to deceleration control using a time constant, and it takes time for the spool valve to pass through the overlapping section for reducing leakage, which is essential for the spool valve, and this is the start of the switching operation for the next cycle. This caused problems in applications with short cycle times.

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 it receives the switching command signal and continues to generate the hold output even after the switching command signal disappears until the arrival of a reset signal; a pattern generator that generates a signal output with a pattern that gradually increases and decreases at the falling edge; and an adder circuit 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 for switching the manual condition of the hold output from the hold circuit in the adder circuit means so that when the switching command signal disappears, the previous addition signal from the adder circuit means is substantially reduced in a stepwise manner; a switching circuit; and a pattern generator by providing a stop command signal to 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. and a current drive circuit that drives switching of the power switching element using a switching control signal pulse width modulated by the addition signal output from the addition circuit means.

Further, in the electromagnetic switching valve drive circuit according to the invention set forth in claim 2, in addition to the above-mentioned invention set forth in claim 1, the pattern generator This is provided with a stop signal input circuit means for forcibly resetting.

Furthermore, in the electromagnetic switching valve drive circuit according to the invention described in claim 3, the electromagnetic switching valve drive circuit according to claim 1 or 2 is used for a dual 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;
a second hold circuit that receives a second switching command signal for the other solenoid device; the second switching command signal is given as a reset signal to the first hold circuit; The first switching command signal is given to the hold circuit as a reset signal, and the pattern generator, the addition circuit means, and the comparison circuit are connected to the first switching command signal.
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 one solenoid device. an output controlled by the outputs of the first and second hold circuits so that when the second hold circuit is producing an output, the output of the current drive circuit is provided only to the other solenoid device. A switching circuit is provided.

[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 Hals output is generated by the switching command signal. The rise of
At the time of falling, the average current is controlled to gradually increase or decrease by Hals 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 drive the spool valve in the direction of opening the flow path against the spring. , the hold circuit immediately generates a hold output at a predetermined level and continues to generate a hold output even after the switching command signal disappears until the arrival of a separately applied reset signal. In this case, the reset signal is
In the case of a single solenoid type electromagnetic directional valve, it can be applied separately from the outside, or after a predetermined period of time using an appropriate internal timer circuit; in the case of a dual solenoid type electromagnetic directional valve, in addition to this The holding circuit belonging to the other solenoid device may be reset by a switching command signal to the 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 start points of the rising edge and the falling edge of this signal output are synchronized with those of the switching instruction signal. I'll do it. 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. It 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 increases gradually in accordance with changes in the signal output of the pattern generator until it reaches a predetermined value. A certain level will be reached after the elapse of time determined by the 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 starts to be driven at an initial speed corresponding to the offset amount, passes through the overlap part of the flow path opening/closing control part, and opens/closes 1.
After reaching the position where the 111111 part begins to open, the opening speed is gradually increased as the moving speed moves towards 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 gradually decreases according to the gradual decreasing 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 work at an initial speed corresponding to the offset amount at the off time, passes through the overlap part of the flow path opening/closing control section, and throttles the flow rate flowing to the opening/closing control section. After reaching the starting position, it returns to the original position while gradually increasing the moving speed.

In general, in switching valves, when on or off, the spool valve starts moving from the fully closed or open state of the flow control section, and it takes a longer distance than in the case of a proportional control valve before the flow rate actually starts to change. move. Overlap this travel distance with vP! When called "heel", 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 FD-force may also not match. Therefore, it is significant to be able to individually set and adjust the on-time and off-time offset amounts as described above.

Now, when the level of the gradual decrease 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 gives a stop command signal to the pattern generator to Force a reset of the pattern generator. As a result, the signal output of the pattern generator disappears and the output of the summing circuit means also disappears, so that the current drive circuit cuts off the excitation current by cutting off the power switching element, and the spool valve immediately springs back. The reference voltage level of this comparator circuit is preferably set and adjusted to match the output level of the adder/subtractor circuit when the spool valve reaches the position where the flow path is completely closed when the spool valve is off. It is possible to minimize the wasted time from when the spool valve is stopped until the spool valve is completely restored.

In the electromagnetic switching valve drive circuit according to the invention according to claim 2,
In addition to the forcible stop using the comparison circuit described above, the pattern generator is also provided with a stop signal input circuit means for forcibly resetting the pattern generator using an external signal. Therefore, in this case, for example, by installing a detector at the movement limit position of the load actuator, detecting that the load has reached that point C, and applying this detection signal to the stop signal input circuit means, it is possible to detect that the switching is still in the process of returning. The spool valve can be forcibly switched and returned to completion, and the cycle time can be significantly shortened.

In the electromagnetic switching valve drive circuit according to the invention according to claim 3,
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 and the comparator circuit are shared by the first and second hold circuits, and each of the single pattern generator and adder circuit means has a pair of comparator circuits and the stop circuit means. Shockless drive control and forced return control for the solenoid device are performed.

the current drive circuit is also shared by both solenoid devices;
Therefore, an output switching circuit h is interposed between the current drive circuit and the Howard switching element. This output switching circuit is controlled by the output of the Hl and the second hold circuit, and When the first hold circuit generates an output, an excitation current controlled by the output of the current drive circuit is applied to only the one solenoid device, and the second hold circuit generates an output. On the other hand, when the signal is applied to the other solenoid device only.

In this case, the control itself of gradually increasing/decreasing the solenoid excitation current by the switching command signal is the same as that of the invention described in claim 1 above.

In order to further 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 pulse width modulated current 11 is connected to the control electrode of each power switching transistor Qa, Qb via an output switching circuit 12.
The current drive circuit 1 is connected to the output terminal of the current drive circuit 14.
4 is subjected to current feedback from both solenoid devices a and b via a current feedback circuit 15, and is stabilized 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, 1 on the base sides of the power switching transistors Qa, Qb on the a side and b side to selectively turn off these transistors.
2b, and these switching elements include hold circuits 20a on the a or b side to which they belong, as 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 depending on the voltage level of the input signal (the voltage level of the input signal is high). This is a type of pulse width modulation device that produces 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 inputted to one of the addition input terminals, and a solenoid device a is input to the remaining two addition input terminals.
Hold outputs from a signal hold circuit 20a belonging to the solenoid device and a signal hold circuit 20b belonging to the solenoid device are respectively inputted. Further, each subtraction input terminal is connected to a hold circuit 20a, 20 via a manual switching circuit 22a, 22b, respectively.
The hold output from b is manually generated 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 circuits 24a and 24a, 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 and 24b receives a step-like minute current signal applied to the switching signal input terminal 26a for the solenoid device a or from the outside via an optical fiber. The applied optical signal is converted into an electrical signal, shaped, and outputted. converts the optical signal provided 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 input switching circuit 22a in addition to one hold circuit 20a, and is further given as a reset signal to the other hold circuit 20b. There is. 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 given to the one hold circuit 20a as a reset signal. It is being

Another input terminal 26c and an 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 a pattern via an OR circuit 46. Generator 18
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 on one human power 36a, and receives a preset comparison reference voltage 3B on the other human power 36b.
When the human power 36a has a higher potential than the input 36, it does not output a stop command signal, and when the input 36a has a lower potential than the input 36, it outputs a stop command signal and sends it to the pattern generator via the OR circuit 46. 18 is forcibly reset. 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 waveform is lost, 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 and an off-time adjuster 29a for the rising edge of the switching command signal from one input circuit 24a, and an on-time regulator 29a for the rising edge of the switching command signal from the other input circuit 24b. Time adjuster 28b and off time adjuster 2 for falling
9b, so that when each switching command signal is input manually, a signal output with a smooth gradual increase/decrease pattern set individually by these regulators is produced.

Further, when this pattern generator 18 receives a stop command signal from the comparator circuit 36 or the input circuit 24c via the OR circuit 46 as described above, it is immediately reset and cuts off the signal output, and at that point the signal output level is changed. It has a function to make the τ 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 manual switching circuit 22b is similar, and its operation is based on a switching command signal for a 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 NOR circuit 40, (F) is the stop command signal output waveform from the comparator circuit 36, (G) is a waveform showing a change in the flow rate due to the switching valve spool, (H) is the output waveform of the addition/subtraction circuit 16, (1) 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 26a, 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).
, the pattern generator 18, the input switching circuit 22a, and the NOR circuit 40, and simultaneously reset the hold circuit 20b on the side. This causes the NOR circuit 40 to operate as shown in (E) in FIG.
The output is stopped as shown in FIG. 2, and the human power 36a of the comparison circuit 36 is connected to the fixed high voltage 44 side by the switching circuit 42, and the stop command signal output of the comparison circuit 36 is stopped as shown in (F) in FIG. I'm letting you do it.

The hold circuit 20a on the second side immediately generates a hold output of the set voltage value shown by Va in (C) of FIG. The hold output Va continues to be held until it receives a switching command signal (as shown from the side input circuit 24b). 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 input 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 1B to the other 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 by (H) in FIG. 2, and then gradually increases in level according to the gradual increase pattern of the signal output of the pattern generator 18 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.

In the output switching circuit 12, as described above, in this case, the switching element 12b receives the hold output from the a-side hold circuit 20a, and the switching element 12b controls the base potential of the power switching transistor Qb by this hold output. The transistor Qb is 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 valves overlap at the corresponding speed. pass through the section.

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 using 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 (FIG. 2(D)). As shown in FIG. 2, 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(H).

Next, the signal output of the pattern generator 1B 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/fall of the level vb and the subsequent gradual decrease pattern of the signal, the current drive circuit 14 controls the switching of the power switching transistor Qa accordingly, so that the average excitation current is initially adjusted to the offset amount. vb, and then gradually decreases 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 initially moves 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 portion is closed without fluid shock.

Here, the NOR circuit 4-0 switches the switching circuit 42 as the switching command signal turns off, and therefore, the output voltage of the addition/subtraction circuit 16 is input to the input 36a of the comparison circuit 36. 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 issues a stop command as shown in (F) in FIG. Output a signal. At this point, the flow rate is T as shown in (G) in Figure 2, and the reference voltage 38 of the comparator circuit 36 is set so that the stop command signal is generated at the same time as the spool valve closes the flow path. The pattern generator 18 receives this stop command signal via the NOR circuit 46 and is immediately reset. As a result, when the pattern generator 16 is reset, the output of the adder/subtractor 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 moved by the spring force to counter electromagnetic force. It will be returned to the final return position without any delay.

Further, even before the idle stop command signal is output from the comparison circuit 36, for example, when the load reaches the stop position, a stop signal is applied to the input terminal 26c from a position detector (not shown), which causes the input circuit 24c to activate the NOR circuit 46. A similar stop command signal is given to the pattern generator 16 via the pattern generator 16 to forcibly reset it.

Note that the hold circuit 20a on the a side is reset when a switching signal arrives at the input terminal 26b on the side as shown in (1) in FIG. 2 and a switching command signal is generated from the input circuit 24b on the side. It is done. This switching command signal on the b side can be given at any time after the stop command signal is generated from the comparison circuit 36 or the stop command input circuit 24c, and the time constant given by the off time adjuster of the pattern generator 18 is It is possible to give before the time has passed.

In addition, the operation of the circuit on the b side is almost the same, and in that case,
The pattern generator 18, addition/subtraction circuit 16, comparison circuit 36, stop command input circuit 24c, current drive circuit 14, etc. are shared with those on the a side.

[Advantageous Effects of the Invention 1] 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 in a short switching cycle is possible. can be realized stably, and the offset amount can be individually adjusted 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, the common part of the circuit can be adjusted. Not only can it be realized with a small and simple circuit configuration, but also the dead time of the time constant after the spool valve closes the flow path when it is off can be eliminated automatically or forcibly from the outside.

[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, 18: Pattern generator, 20a, 20b: Hold circuit, 22a, 22b
:Manual switching circuit, 24a, 24b: Input circuit, 24c:
Stop command signal input circuit, 26a, 26b: input terminals,
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, a stop command signal is given to the pattern generator to forcibly turn the pattern generator. an electromagnetic switching device comprising: a comparison circuit for resetting the power switching element; and a current drive circuit for driving the switching of the power switching element using a switching control signal pulse width modulated by the addition signal output from the addition circuit means. Valve drive circuit. 2. The electromagnetic switching valve drive circuit according to claim 1, further comprising stop signal input circuit means for forcibly resetting the pattern generator by applying a stop command signal to the pattern generator from the outside. 3. Claim 1 or 2 for a double solenoid type electromagnetic switching valve that performs bidirectional switching using a pair of solenoid devices.
The electromagnetic switching valve drive circuit according to , wherein the hold circuit receives a first switching command signal for one solenoid device, and a second switching command signal for the other solenoid device. and a second hold circuit that receives a command signal, the first hold circuit is given the second switching command signal as a reset signal, and the second hold circuit is reset with the first switching command signal. the pattern generator, the adder circuit means, and the comparison circuit are shared by the first and second hold circuits; and between the current drive circuit and the power switching element, the When the first 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 other solenoid device. An electromagnetic switching valve drive circuit comprising: an output switching circuit controlled by the outputs of the first and second hold circuits so as to apply the output only to the solenoid device.