JPH0579869B2 - - Google Patents

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 and close a fluid flow path using a switching command signal. In particular, the present 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 improving the shape of the spool valve driven by a solenoid device and reducing the switching speed of the spool valve by restricting the fluid flow generated by the movement of the spool valve. However, this method not only complicates the mechanical structure, but also consists of fixed control elements that cannot be variably adjusted, so the spool valve The switching time varies, often resulting in unsatisfactory results.

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. For example, Japanese Patent Application No. 62-217035 (Japanese Unexamined Patent Publication No. 64-058890)
etc. can be mentioned.

In other words, in the drive circuit of this electrically controlled shockless electromagnetic switching valve, individual time constant circuits are provided for each of the rising edge when on and the falling edge when turning off with respect to the step-shaped switching command signal. , in combination with a comparator circuit, when the output voltage level of the on-time constant circuit reaches a predetermined value or higher, the power supply charge is accumulated in the off-time constant circuit, and this accumulated charge is stored in the off-time constant circuit. A desired gradual increase/decrease signal is obtained at each on/off time by discharging in the off time constant circuit, and this gradual increase/decrease signal pulse width modulates the power switching element of the solenoid excitation current. By introducing a resistor voltage divider circuit into the time constant circuit for ON, the voltage division ratio is adjusted to the gradual increase/decrease signal at the moment of ON and OFF. By giving a corresponding offset, it is possible to shorten the time through which the flow path opening/closing control section of the spool valve passes through the overlap section until it begins to open and begins to close, thereby shortening the so-called dead zone time.

[Problems to be Solved by the Invention] In the drive circuit of the electrically controlled shockless electromagnetic switching valve mentioned in the conventional example described above, 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 In some cases, charge accumulation in the time constant circuit used for the switch is not performed sufficiently, and there is a risk that the off-time shockless operation may be impaired when operating with a short switching cycle.

In addition, 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 offset, so the magnitude of the offset must 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 a dual solenoid type electromagnetic directional valve.There are few common circuit parts, and the circuit configuration becomes complex and large. I hated doing that.

Furthermore, in the conventional system, the off-state switching is performed by controlling the excitation current of the solenoid device to gradually decrease using a time constant pattern. There was also a problem in that if the temperature changed, this would appear as a change in the flow rate, and the stopping position of the load actuator would change.

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 order to solve the above-mentioned problem, in the electromagnetic switching valve drive circuit according to the invention as claimed in claim 1, the solenoid of the electromagnetic switching valve is activated via a power switching element in response to a switching command signal. In the electromagnetic switching valve drive circuit that controls the switching operation of the electromagnetic switching valve by controlling the excitation current of the device on and off, upon receiving the switching command signal, a hold output at a predetermined level is immediately generated and the switching command signal disappears. a hold circuit that continues to generate a hold output until the reset signal arrives; a pattern generator that generates a pattern of signal output that gradually increases and decreases at the rising edge and the falling edge in response to the switching command signal; addition circuit means for outputting an addition signal of the signal output of the pattern generator and the hold output of the hold circuit; an input switching circuit for switching the input condition of the hold output from the hold circuit in the adder circuit means such that the input condition for the hold output from the hold circuit in the adder circuit means is substantially reduced; and a level of the add signal from the adder circuit means is preset after the switching command signal disappears. a comparison circuit that stops the drop in the signal output level of the pattern generator and fixes it at a relatively low level when the signal output level of the pattern generator drops to a comparison reference level, and sends an external stop command signal to the pattern generator; stop circuit means for forcibly resetting the pattern generator by applying a signal to the pattern generator; and a current drive circuit for driving the power switching element by switching with a switching control signal pulse width modulated by the addition signal output from the addition circuit means. It is equipped with the following.

Furthermore, the electromagnetic switching valve drive circuit according to the invention set forth in claim 2 includes 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, and the second hold circuit is supplied with the second switching command signal as a reset signal.
a switching signal is given as a reset signal, the pattern generator, the adder circuit means, the comparator circuit and the stop circuit means are shared by the first and second hold circuits, the current drive circuit and the power Between the switching element and the first hold circuit, when the first hold circuit is producing an output, the output of the current drive circuit is given only to the one solenoid device, and the second hold circuit is producing the output. An output switching circuit is provided which is controlled by the outputs of the first and second hold circuits so as to provide the output of the current drive circuit 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 used as a switching command signal. The average current is controlled to gradually increase or decrease by pulse width modulation at the rise and fall of the current.

Now, a 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 starts supplying the solenoid excitation current. This is to start cutting off the excitation 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 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 switching valve, the voltage can be supplied separately from the outside, or after a predetermined period of time using an internal appropriate timer circuit. The hold circuit belonging to the other solenoid device may be reset by a switching command signal to the 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. 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 decrease are changed with a predetermined time constant. It can be easily configured using existing technology.

The addition circuit means receives the signal output of the pattern generator and the hold output of the hold circuit as addition inputs, and generates an addition 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. 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 thereafter increases gradually in accordance with changes in the signal output of the pattern generator, A certain level will be reached after a period of time according to 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 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 is reduced. It will move towards the switching position while increasing gradually.

Conversely, when the switching command signal is turned off and disappeared in order to return the spool valve from the switching position to the original position in order to close the flow path, the input switching circuit changes the addition signal from the addition circuit means up to that point. 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 separately supplies this hold output to the adder circuit means as a subtraction input, for example. In the adder circuit means, the previously applied hold output as the addition input is subtracted in a stepwise manner 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 set arbitrarily.

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 decreasing pattern of the signal output of the pattern generator. Then, in the same way as described above, the spool valve of the electromagnetic switching valve begins to move at an initial speed corresponding to the offset amount at the time of OFF, 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, the movement speed is gradually increased while returning to the original position.

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. 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 is also the same. Therefore, it is significant to be able to individually set and adjust the offset amounts for on and off 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 supplies a hold signal to the pattern generator to pattern the pattern generator. The drop in the signal output level of the generator is stopped at that point, and thereafter the signal output is maintained at the relatively low level at that time. As a result, the excitation current flows at a constant low current, the spool valve is maintained in a flow path control state in a certain low flow rate range, and the load actuator moves at a constant speed in the low speed range immediately before deceleration and stop. . When the load reaches the position where it should stop, a stop command signal is given, for example, from a position detector installed at the target stop position.
In response to this, the stop circuit means forcibly resets the pattern generator by giving an external stop command signal to the pattern generator. As a result, the signal output of the pattern generator disappears, and the output of the adder 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 path blocking 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 switches in both directions by a pair of solenoid devices,
The hold circuit comprises 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. There is. 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 resetting the switching command signal of the other party. The hold circuit is reset at the rising edge of .

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, and 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, it is controlled by the output of the current drive circuit. The excitation current is applied only to the one solenoid device, and conversely, when the second hold circuit is producing an output, it is applied only to the other solenoid device.

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

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. Each power switching transistor Qa,
The control electrode of Qb is connected to the output terminal of a pulse width modulated current drive circuit 14 via an output switching circuit 12, and this current drive circuit 14 receives a current feedback circuit 15 from both solenoids a and b.
Current feedback is applied through the solenoid to stabilize against changes in resistance due to temperature rise in the solenoid device and changes due to power supply voltage fluctuations.

The output switching circuit 12 includes switching elements 12a and 12b on the base sides of the power switching transistors Qa and Qb on the a side and the b side for selectively turning off these transistors. Hold circuit 20a, 2 on the a or b side to which
Controlled by the hold output of 0b, when the solenoid device a on the a side is energized, the switching element 12b turns off the transistor Qb, and when the solenoid device b on the b side is energized, the switching element 12a turns off the transistor Qb.
This puts Qa in a cut-off state.

Specifically, the current drive circuit 14 has a variable pulse width that changes depending on the voltage level of the input signal.
It can be configured with a voltage controlled variable pulse width oscillator circuit that generates a PWM waveform output and a base drive circuit.
It is a type of pulse width modulation device that produces a pulse output whose pulse width becomes wider as the input voltage level is higher.

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.
Hold outputs from a signal hold circuit 20a belonging to the solenoid device b and a signal hold circuit 20b belonging to the solenoid device b are respectively input. In addition, each subtraction input terminal has an input switching circuit 22a, 22b.
Hold outputs from hold circuits 20a and 20b are separately inputted via the hold circuits 20a and 20b. Each of these addition input terminals and subtraction input terminals is gain adjustable.

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

The input circuits 24a and 24b are composed of, for example, a photocoupler and a waveform shaping circuit, and one input circuit 2
4a converts a step-like minute current signal applied to the switching signal input terminal 26a for the solenoid device a or an optical signal applied from the outside via an optical fiber into an electric signal, shapes it, and outputs it; The input circuit 24b converts a step-shaped minute current signal separately applied to the switching signal input terminal 26b for the solenoid device b or an optical signal applied from the outside via an optical fiber into an electric signal and then shapes the signal. Output.

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

Another input terminal and 26c and input circuit 2
4c receives an optical signal from an external stop position detector (limit switch, etc.) of a load actuator, generates a stop command signal, and supplies this to the pattern generator 18 to forcibly reset the pattern generator at that point. It is for. 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, receives a preset comparison reference voltage 38 at the other input 36b, and
When the potential of the input 36a is higher than that of the input 36b, no hold signal is outputted, and when the potential of the input 36a becomes lower than that of the input 36b, a hold signal is outputted to fix the output level of the pattern generator 18 to the level at that time. In this case, the switching circuit 42 changes 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 is connected to one input circuit 24
On-time adjuster 28a for the rising edge of the switching command signal from A and OFF-time regulator 29a for the falling edge of the switching command signal from the other input circuit 24b; Vessel 2
9b, and when each switching command signal is input, these regulators produce signal outputs in a smooth gradual increase/decrease pattern set individually. Also, this pattern generator 1
8 is a function to immediately reset and cut off the signal output when receiving the stop command signal from the input circuit 24c as described above, or to maintain the signal output level at that time when receiving the hold signal from the comparison circuit described above. It has

The input switching circuit 22a includes a control element 32a and a switching element 34a.
When a switching command signal is given from
The hold output from the hold circuit 20a to which it belongs is cut off from being supplied to the subtraction input terminal of the addition/subtraction circuit 16, and synchronizes with the falling edge of the switching command signal it receives when it is turned off and disappears. The hold output of the associated hold circuit 20a is supplied to the subtraction input terminal of the addition/subtraction circuit 16.

The same applies to the other input switching circuit 22b, and corresponding elements have a suffix b added to the corresponding symbol.
Although a detailed explanation will be omitted since it is shown with the numeral , it should be noted that its operation is performed by a switching command signal for the solenoid device b.

B: Explanation of Operation FIG. 2 shows waveforms of various parts for explaining the operation of the circuit of this embodiment having the above-described 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 hold circuit 20a or 2.
0b to the hold output waveform given to the addition input terminal of the addition/subtraction circuit 16, D is the hold circuit 20
The hold output waveform applied from a or 20b to the subtraction input terminal of the addition/subtraction circuit 16, E is the output waveform of the addition/subtraction circuit 16, F is the output waveform of the NOR circuit 40, G is the hold signal output waveform from the comparison circuit 36, 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 26a, the optical signal given to the input terminal 26a is converted into an electrical signal by the input circuit 24a, and the waveform is shaped. A step-like switching command signal as shown by A is input to the hold circuit 20a on the a side, the pattern generator 18, the input switching circuit 22a, and the NOR circuit 40, and at the same time, the hold circuit 20b on the b side is reset. The NOR circuit 40 thereby stops outputting as shown in F in FIG.
The input 36 of the comparison circuit 36 is controlled by the switching circuit 42.
Connect a to the fixed high voltage 44 side to connect the comparison circuit 3.
The hold signal output of No. 6 is stopped as shown at G in FIG.

The hold circuit 20a on the a side immediately generates a hold output of the set voltage value shown by Va in C in FIG. Hold output until receiving signal)
Continue to hold Va. In response to this hold output, the output switching circuit 12 switches the power switching transistor Qb on the b side by the b side switching element 12b while the hold output exists.
is kept in a blocked state.

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

At the rising edge of the switching command signal, the pattern generator 18 starts producing a pattern signal output as shown by B in FIG.
This is a gradual increase pattern in which the output level gradually increases according to the time constant set in step 8a.

The hold output Va of the hold circuit 20a is applied to one of the addition input terminals of the addition/subtraction circuit 16 at the same time as the switching command signal rises.
The incremental pattern signal output from the pattern generator 18 is applied to another summing input terminal, so that the summing output rises steeply by Va at the same time as the switching command signal rises, as shown by E in FIG. This results in a signal that gradually increases in level according to the gradual increase pattern of the signal output of the generator 18.

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 power switching transistor.
Transistor Qb is kept in a cut-off state by controlling the base potential of Qb.

Therefore, the output pulse of the current drive circuit 14 pulse-drives only the power switching transistor Qa, and the PWM of the gradual increase pattern as described above is generated.
Only transistor Qa operates according to the waveform switching control signal.

Solenoid device a by transistor Qa
At the same time as the switching command signal rises, the excitation current supplied to the spool valve flows at an average current value of an offset amount corresponding to the hold output level Va, so that the spool valve passes through the overlap portion at a corresponding speed. 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. This will open the flow path 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 input switching circuit 22a is activated at the same time as the switching command signal falls.
gives a hold output of voltage level Vb to the subtraction input terminal of the addition/subtraction circuit 16 as shown by D in FIG. descend.

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 addition/subtraction circuit 16 also gradually decreases.

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

In response to such a steep fall in level Vb followed by a signal input with a gradual decrease pattern, the current drive circuit 14 switches the power switching transistor.
The switching control of Qa is performed accordingly, so that the average excitation current is first adjusted by the offset amount.
There is a sudden drop corresponding to Vb, and then it 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 movement of the spool valve initially corresponds to the offset amount Vb. Then, the speed is gradually increased according to the excitation current value, which gradually decreases from the position where the flow path starts to be throttled, and the flow path opening/closing portion is closed without a fluid shock.

Here, as the switching command signal turns off, the NOR circuit 40 switches the switching circuit 42, and therefore, the output voltage of the addition/subtraction circuit 16 is input to the input 36a of the comparison circuit 36. This addition/subtraction circuit 1
6 gradually decreases according to the decreasing 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, from now on, the adder/subtracter 1
The output of No. 6 is also at a constant level. As a result, the solenoid excitation current by the power switching transistor Qa, which is switching-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 near the end of the process of closing the flow path. Then,
As a result, the load actuator continues to move slowly at a low speed just before decelerating to a stop. When the load reaches the stop position, a position detector (not shown) gives a stop signal to the input terminal 26c,
As a result, the input circuit 24c applies a stop command signal as shown in FIG. 2H to the pattern generator 16 to forcibly reset it. When the pattern generator 16 is reset, the output of the adder/subtracter 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. will be returned to.

Note that the a-side hold circuit 20a is reset when a switching signal arrives at the b-side input terminal 26b and a switching command signal is generated from the b-side input circuit 24b.

In addition, the operation of the circuit on the b side is almost the same,
In that case, the pattern generator 18 and the addition/subtraction circuit 1
6. Comparison circuit 36 and stop command input circuit 24c
The current drive circuit 14 and the like 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 can be achieved stably with a short switching cycle, and the amount of offset can be adjusted individually to reduce the dead zone time due to passing through the overlap section in each on/off situation.It is also suitable for use in dual solenoid type electromagnetic switching valves. In addition to increasing the number of common parts in the circuit and realizing a compact and simple circuit configuration, the load can be moved at a low speed just before stopping, and an external stop command can be issued to accurately stop the load at a predetermined target position when the load is off. It can be forcibly turned off completely using a signal.

[Brief explanation of drawings]

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 solenoid type electromagnetic switching valve, and Fig. 2 is a diagram showing waveforms of various parts 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, 22
b: input switching circuit, 24a, 24b: input circuit,
24c: Stop command signal input circuit, 26a, 26
b: Input terminal, 26c: Stop signal input terminal, 3
6: 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 the arrival of a reset signal even after the switching command signal disappears; a pattern generator that generates a pattern of signal outputs that gradually increases and decreases at a rate of 1 to 2; addition circuit means that outputs an addition 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 at a fixed 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 switches and drives the power switching element using a switching control signal whose pulse width is modulated by the switching control signal. 2. The electromagnetic switching valve drive circuit according to claim 1 for a double solenoid type electromagnetic switching valve that performs bidirectional switching by a pair of solenoid devices, wherein the hold circuit A first hold circuit receives a switching command signal for one solenoid device, and a second hold circuit receives a switching command signal for the other solenoid device.
and a second hold circuit that receives the switching command signal, the first hold circuit receives the second switching command signal as a reset signal, and the second hold circuit receives the switching command signal as a reset signal.
The first switching command signal is given as a reset signal to the hold circuit, and the pattern generator, the addition circuit means, the comparison circuit, and the stop circuit means are applied to the first and second hold circuits. 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 provided only 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 the output of the current drive circuit only to the other solenoid device when the second hold circuit is producing an output. An electromagnetic switching valve drive circuit characterized by: