JPS6224643B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a pressure-reducing electromagnetic pilot valve that operates in response to applied current to a solenoid, and a two-stage electromagnetic pilot valve that operates a main spool with a secondary pressure controlled by the valve. The present invention relates to a two-stage electromagnetic proportional throttle switching valve with a pressure reducing pilot valve that integrally connects a proportional throttle valve, and particularly to one having a control circuit that feeds back the position signal of the main spool to the applied current of the solenoid.

Conventionally, this type of electromagnetically operated proportional throttle valve has been designed such that a changeover switch switches the connection between an electric controller and a solenoid to select the direction of movement of the main spool, while the electric controller controls the setpoint value signal. The opening degree of the main spool is controlled by controlling the current flowing through the solenoid in response to the so-called
Open loop control was used.

Problems to be Solved by the Invention By the way, as described above, in a device that controls the opening degree of the main spool of an electromagnetic proportional throttle valve by open-loop control, if a disturbance etc. is input to the controller, the target value signal will be affected. Since this directly affects the proportional accuracy of the opening degree of the main spool, there is a problem in that the static accuracy with respect to the target value signal of the main spool is low. The first invention of the present application is a pressure reducing pilot valve equipped with a pressure reducing pilot valve 2 having a control circuit that has a control circuit that has little influence on the proportional accuracy of the opening degree of the main spool with respect to the target value signal due to disturbance etc. and has high static accuracy with respect to the target value signal of the main spool. The object of the present invention is to provide a stepped electromagnetic proportional throttle switching valve.

Further, the first invention of the present application is a decompression pilot having a control circuit that improves the stability of the control system against disturbances etc. that are superimposed and input on the target value signal, and prevents a decrease in transient response to sudden changes in the target value signal. The object of the present invention is to provide a two-stage electromagnetic proportional throttle switching valve with a valve.

Furthermore, in addition to the above object, the second invention of the present application uses an electric circuit to compensate for the nonlinearity of the throttle opening characteristic of the main spool, thereby greatly improving the stability and static accuracy of the control system that is caused by nonlinearity. It is an object of the present invention to provide a two-stage electromagnetic proportional throttle switching valve with a pressure reducing pilot valve having an improved control circuit.

Means for Solving the Problems Therefore, the first invention of the present application provides a pressure-reducing electromagnetic pilot valve that operates according to the current applied to a solenoid, and a pressure-reducing electromagnetic pilot valve that is controlled by the pressure-reducing electromagnetic pilot valve.
A two-stage proportional throttle valve that operates the main spool with the next pressure, a position detection means that detects the position of the main spool and converts it into an electrical signal, and a position signal (positive voltage) of the main spool and a specific target value. a proportional-integral circuit that performs an addition operation with a signal (negative voltage) and integrates the result; a feed-forward circuit that bypasses the target value signal to the proportional-integral circuit; and an output of the feed-forward circuit. The present invention is characterized in that it includes an adder circuit that outputs a sum signal of the signal and the output signal of the proportional-integral circuit, and outputs the sum signal to the drive circuit of the pressure-reducing pilot valve.

The second invention of the present application also provides a pressure-reducing electromagnetic pilot valve that operates according to the applied current to a solenoid, and a two-stage proportional throttle that operates the main spool with the secondary pressure controlled by the pressure-reducing electromagnetic pilot valve. valve and
a position detection means for detecting the position of the main spool and converting it into an electrical signal; and a position detecting means for detecting the position of the main spool and converting it into an electric signal, and adding the main spool position signal (positive voltage) and a specific target value signal (negative voltage) and integrating the result. A proportional-integral circuit,
a feed-forward circuit that bypasses the target value signal to the proportional-integral circuit; an adder circuit that outputs a sum signal of the output signal of the feed-forward circuit and the output signal of the proportional-integral circuit; a gain switching circuit that connects a subtraction circuit to the input side of the addition circuit when the target value signal exceeds a threshold value determined corresponding to a sudden change portion of the aperture opening gain of the main spool; The present invention is characterized in that the output signal is outputted to the drive circuit of the pressure reducing type pilot valve.

Operation In the first invention of the present application, the proportional integration circuit adds the target value signal and the main spool position signal output from the position detection means and integrates the result. Further, the feedforward circuit bypasses the target value signal without passing through the proportional-integral circuit. The adder circuit outputs a sum signal of the output signal of the feedforward circuit and the output signal of the proportional-integral circuit to the drive circuit of the pressure reducing type pilot valve. The proportional-integral circuit performs feedback control on the position of the main spool to improve control accuracy of the main spool with respect to the target value signal, and also provides a time constant to the main spool control system to improve its stability.
Further, the feedforward circuit bypasses the sudden change component of the target value signal to the adder circuit, thereby preventing a decrease in transient response caused by the proportional-integral circuit.

On the other hand, in the second invention of the present application, the proportional-integral circuit provides a time constant to the control system of the main spool, and the feed forward circuit bypasses the sudden change component of the target value signal to the adder circuit. When the value signal exceeds a threshold value set corresponding to a sudden change in the aperture opening gain of the main spool, the gain switching circuit connects a subtraction circuit to the input side of the addition circuit, and to compensate for the nonlinearity of the aperture opening characteristic.

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

First, before entering into the description of the embodiments of the first invention and the second invention of the present application, with reference to FIGS. 1 and 2, the control common to the first invention and the second invention of the present application will be explained. The basic configuration of the circuit and the two-stage electromagnetic proportional throttle switching valve with a pressure reducing pilot valve will be explained.

1 and 2, the electromagnetic proportional throttle switching valve 6 is integrally equipped with a pressure reducing type electromagnetic pilot valve (hereinafter referred to as an electromagnetic pilot valve) 3. As shown in FIG. The electromagnetic proportional throttle switching valve 6 includes cylinder ports A, B, tank port T, and pump port P.
It is equipped with an inlet valve block 1 having a diameter. A constant hydraulic pressure, that is, primary pressure (pump discharge pressure) supplied from the pump port P of the inlet valve block 1 through the main line 2, is operated as two pressure reducing valves having a switching function by solenoids 3a and 3b. The pressure is reduced by the activated electromagnetic pilot valve 3. Then, the pressure is reduced by the electromagnetic pilot valve 3.
The next pressure (pilot pressure) is the pilot line 4,
5 to both ends of a main spool 7 which is slidably built in the electromagnetic proportional throttle switching valve 6 in the axial direction. The electromagnetic pilot valve 3 receives an operating force from an applied current flowing through one of the solenoid 3a or 3b, and the above-mentioned 2 actuation force applied from the pilot line 9a or 9b to each end of the electromagnetic pilot valve 3 on the opposite side to the solenoid 3a or 3b. It is controlled so that it is stopped at a position where the next pressure is balanced.
On the other hand, the electromagnetic proportional throttle switching valve 6 has push springs 8a and 8b respectively compressed at both ends of the main spool 7.
It is controlled to stop at a position where the spring force and the secondary pressure acting on the electromagnetic pilot valve 3 and the secondary pressure acting on the end of the main spool 7 are balanced. The amount of sliding of the main spool 7 toward the corresponding side is controlled depending on the magnitude of the applied current flowing through either of the solenoids 3a and 3b, and the opening degree for each port A, B, and T is adjusted. It's becoming like that. In addition, in Figures 1 and 2, 9
a and 9b are pilot lines 4 and 5 for guiding secondary pressure to the above-mentioned ends of the electromagnetic pilot valve 3, respectively;
are pilot lines for guiding secondary pressure to each end of the electromagnetic proportional throttle switching valve 6, 10a and 10b are variable throttle valves provided in the pilot lines 4 and 5,
11 and 12 are a drain and a tank connected to the electromagnetic pilot valve 3, respectively.

As shown in FIG. 1, the electromagnetic proportional throttle switching valve 6
As a control circuit, a potentiometer 14 is provided as a position detection means on the main spool 7, and a target value as an electric signal is provided between the potentiometer 14 and the solenoids 3a and 3b of the electromagnetic pilot valve 3. A comparator 15 is provided to introduce the signal, and the position signal of the main spool 7 is transmitted to the solenoid 3.
Feedback is made as the applied currents of a and 3b. That is, the control circuit basically detects the position signal of the main spool 7 using the potentiometer 14, and adds the position signal and a preset target value signal introduced from the outside to the comparator 15. They are compared at the matching point, and the difference between the two signals is input to the electric controller 13, and the applied current is applied to either solenoid 3 according to the + or - difference and its magnitude.
Drive a and 3b. As a result, the control circuit controls the main spool 7 until the position signal matches the target value signal, thereby performing so-called closed-loop feedback control.

With pressure reducing pilot valve 2 having the above basic configuration
In the stepped electromagnetic proportional throttle switching valve, primary pressure oil is always supplied to the main line 2 from the pump port P of the inlet valve block 1, and current is applied to, for example, the left solenoid 3a of the electromagnetic pilot valve 3. When is applied, the electromagnetic pilot valve 3 moves to the right by an amount corresponding to the magnitude of the applied current to the solenoid 3a, allowing secondary pressure oil to flow from the main line 2 to the pilot line 5 on the right side, and as a result, The main spool 7 of the electromagnetic proportional throttle switching valve 6 is moved to the left by an amount corresponding to the oil pressure of the pilot line 5, and the oil in the main line 2 flows out to the cylinder port B by an amount corresponding to the current value applied to the solenoid 3a. let The electromagnetic pilot valve 3 then applies oil at the secondary pressure from the pilot line 9b to its right end, and stops at a position where the secondary pressure and the current applied to the solenoid 3a are balanced. At this time, the solenoid 3a
The secondary pressure of the pilot line 9b is fed back to the applied current of the electromagnetic pilot valve 3 to the applied current of the solenoid 3a.
is moved more accurately, and therefore the switching of the main spool 7 of the two-stage proportional throttle switching valve is performed more reliably. In addition, the main spool 7 switched in this way
potentiometer 1 using the current position as a position signal.
Since it is extracted and fed back in step 4,
The current applied to the solenoid changes depending on the current position of the main spool 7, and the solenoid 3a,
3b allows the electromagnetic pilot valve 3, and therefore the main spool 7, to be controlled more accurately and reliably to the desired value.

Next, a specific example of the first invention of the present application is as follows.
It is shown in Figure 3.

In FIG. 3, 20 is a potentiometer for generating a target value signal, and 21 is the potentiometer 20.
A proportional-integral circuit 22 adds the target value signal outputted from the main spool 7 and the position signal of the main spool 7 outputted from the potentiometer 14 as a position detection means, and integrates the result.
This is a feed forward circuit that bypasses the target value signal to the adder circuit 23 without passing through the adder circuit 23.

Further, 25 is a main amplifier that generates a constant current corresponding to the output of the adder circuit 23, and 26 is an electromagnetic proportional switching throttle valve, which is the same as that shown in FIG.

The potentiometer 20 has one end of its resistor connected to ground and the other end connected to a constant voltage Vs.
is applied, and a target value signal e _s is output corresponding to the position of the slider.

Proportional-integral circuit 2 into which the target value signal e _s is input
1 consists of an operational amplifier OA ₁ , a capacitor C, a variable resistor VR ₁ , and resistors R ₁ , R ₂ and R ₃ , and a connection between the inverting input terminal of the operational amplifier OA ₁ and the slider of the potentiometer 20 A resistor R ₁ is placed between them, and
A resistor R ₂ is connected between the slider of the potentiometer 14 and the above-mentioned inverting input terminal, and
A resistor _R3 and a capacitor C are connected in parallel between the output terminal of the operational amplifier _OA1 and the inverting input terminal, while the non-inverting input terminal is connected to ground via a resistor _R4 .

From the above, operational amplifier OA ₁ has its output e ₀₁
Then, the target value signal e _s and the position signal e _p of the main spool 7 output from the potentiometer 14
When the change in is sufficiently slower than the time constant C×R ₃ , it operates as an adder circuit of e ₀₁ =−( _es R ₃ /R ₁ +e _p R ₃ /R ₂ )…(1) (R ₁ = R ₂ = R ₃ , then e ₀₁ =-( _es + e _p ). On the other hand, when the change in the target value signal e _s and the position signal e _p is about or faster than the time constant C×R ₃ , the operational amplifier circuit OA ₁ changes the time constant to the target value signal e _s . It operates as a Miller integration circuit with a time constant of C×R ₁ and a time constant of C×R ₂ for the position signal e _p .

In addition, a variable resistor VR ₁ is connected between the output terminal of the operational amplifier OA ₁ and the ground.
The output e ₀₁ of OA ₁ is adjusted.

On the other hand, the feed forward circuit 22 includes an operational amplifier OA ₂ , resistors R ₅ , R ₆ , R ₇ and a variable resistor VR ₂
Consisting of A resistor is connected between the inverting input terminal of the operational amplifier OA ₂ and the slider of the potentiometer 20.
R ₅ , also the above inverting input terminal and operational amplifier OA ₂
A resistor R ₆ is connected between the output terminal of each. On the other hand, the non-inverting input terminal of the operational amplifier _OA1 is connected to ground via a resistor _R7 . As a result, the operational amplifier OA ₂ has a voltage gain A _V1 =
- Construct an inverting amplifier of (R ₆ /R ₅ ).

A variable resistor VR ₂ is connected between the output terminal of the operational amplifier OA ₂ and the ground, and the operational amplifier OA ₂
I'm trying to adjust the output.

The output e' ₀₂ of the feedforward circuit 22 and the output e' ₀₁ of the proportional-integral circuit 21 are respectively input to an adder circuit 23 and added together. This adder circuit 23 consists of an operational amplifier _OA5 and four resistors.
It consists of R ₁₆ , R ₁₇ , R ₁₈ and R ₂₀ .

The non-inverting input terminal of the operational amplifier OA ₅ above is a resistor
The inverting input terminal is connected to ground via R ₁₆ , while the inverting input terminal is connected to the variable resistor via resistors R ₁₇ and R ₁₈ , respectively.
Connect to the slider of VR ₁ and the slider of variable resistor VR ₂ , and connect the inverting input terminal to the operational amplifier.
A resistor _R20 is connected between the output terminal of _OA5 .

With the above connection, the adder circuit 23 performs the calculation e ₀₅ =−(e′ ₀₁ +e′ ₀₂ ) (3).

However, e ₀₅ is the output of the adder circuit 23, and it is assumed that R ₁₇ =R ₁₈ =R ₂₀ .

The output e ₀₅ of the adder circuit 23 is input to the main amplifier 25 . On the other hand, the output terminal of the main amplifier 25 is connected to a movable contact 26c of a changeover switch SW.

The fixed contact 26R of the changeover switch SW is connected to the solenoid 3a of the decompression pilot valve 3, and the other fixed contact 26L is connected to the solenoid 3a of the decompression pilot valve 3.
are connected to the respective solenoids 3b.

In FIG. 3, B ₁ and B ₂ are batteries serving as constant voltage sources for the potentiometer 14 that detects the position of the main spool 7.

To explain the operation of the control circuit having the above configuration, when the target value signal e _s output from the potentiometer 20 is set to a constant value, the position of the main spool 7 of the main valve 6 is In the same way as the control circuit already explained in the figure, ( _es + e _p )
≒0, and the electromagnetic proportional throttle switching valve 6 has a predetermined throttle opening corresponding to the target value signal e _s .

Furthermore, when the target value signal e _s changes sufficiently slower than the time constant C×R ₃ , the proportional integral circuit 21 operates as an adding circuit, and as in the above case, the proportional integral circuit 21 operates as a main circuit of the electromagnetic proportional throttle valve 6. The position of spool 7 is (e _s
+e _p )≈0, and the main spool 7 changes its aperture opening following changes in the target value signal e _s .

Further, when the target value signal e _s changes at a speed equal to or faster than the time constant C×R ₃ , the output e ₀₁ of the proportional-integral circuit 21 changes by the time constant C×R with respect to the target value signal e _s . ₁ and responds to the position signal e _p of the main spool 7 with a time constant C×R ₂ , so the response of the output e ₀₁ of the proportional-integral circuit 21 is delayed.

However, in this case, the target value signal e _s
A fast change in is bypassed to the adder circuit 23 through the feedforward circuit 22 without response delay, without going through the proportional-integral circuit 21. As a result, the main amplifier 25 drives the main spool 7 without delay.

Moreover, the feedforward circuit 22 is
Since it is not included in the closed loop that controls the main spool 7, it has no effect during closed loop control.

Next, a specific example of the second invention of the present application is as follows.
It is shown in Figure 4.

In the embodiment shown in FIG. 4, a gain switching circuit 24 is already added to the control circuit of the two-stage electromagnetic proportional throttle switching valve with pressure reducing pilot valve having the control circuit of the first invention explained in FIG. It is something.

Note that in FIG. 4, parts corresponding to those in FIG. 3 are indicated with corresponding reference numerals, and redundant explanation will be omitted.

The gain switching circuit 24 includes operational amplifiers OA ₃ ,
OA ₄ , OA ₆ , Zener diode D ₁ , variable resistor
VR ₃ , VR ₄ and resistors R ₈ ,..., R ₁₆ and R ₂₁ ,
R ₂₂ and a field effect transistor TR ₁ .

A resistor _R11 is connected between the inverting input terminal of the operational amplifier _OA3 and the slider of the variable resistor _VR3 , and one end of the resistor of the variable resistor _VR3 is connected to a resistor.
The other end of the resistor is connected to the power supply -Vcc via _R12 , and to the ground via a resistor _R13 .

Also, the non-inverting input terminal of operational amplifier OA ₃ is connected to a resistor.
Connected to ground via R′ ₁₃ . On the other hand, the inverting input terminal of the operational amplifier OA ₃ is connected to the slider of the potentiometer 20 via a resistor R ₈ , and the Zener diode D 1 whose cathode side is connected to the output terminal of the operational amplifier OA ₃ is connected to the slider of the potentiometer 20 via a resistor R ₈ . connected to the anode. The target value signal e _s is the variable resistor above.
When the threshold voltage e _th (described later) set by VR ₃ is smaller, the operational amplifier OA ₃
is clamped to a constant positive voltage whose output is limited by the Zener diode _D1 . Further, when the target value signal e _s is larger than the threshold voltage e _th , the operational amplifier OA ₃ clamps its output to a constant negative voltage corresponding to the resistance of the Zener diode D ₁ . . operational amplifier
The inverting input terminal of OA ₆ is connected to the output terminal of the above operational amplifier OA ₃ via resistor R ₉ , and
It is connected via R ₂₁ to the output terminal of the operational amplifier OA ₆ . Further, the non-inverting input terminal of the operational amplifier OA ₆ is connected to ground via a resistor R ₂₂ . Therefore, the output e ₀₃ of the operational amplifier OA ₆ is:
When the target value signal e _s is smaller than the threshold value e _th , it is clamped to a constant negative voltage, and when the target value signal e _s is larger than the threshold value e _th , it is clamped to a constant positive voltage.

On the other hand, one end of variable resistor VR ₄ is connected to the variable resistor
While connecting the slider of VR ₁ , the variable resistor VR ₄
A resistor _R'14 is connected between the slider and the inverting input terminal of the operational amplifier _OA4 . Also, the other end of VR ₄ is connected to ground.

The operational amplifier OA ₄ has a resistor R ₁₅ connected between its inverting input terminal and output terminal, and
The non-inverting input terminal is connected to ground via a resistor _R16 . The above operational amplifier OA ₄ is connected to the above resistor
With R' ₁₄ , R ₁₅ and R ₁₆ the voltage gain A _V2 = -
(R ₁₅ /R′ ₁₄ ) constitutes an inverting amplifier. Further, the output of the operational amplifier OA ₄ is connected to the source terminal of the N-channel field effect transistor TR ₁ ,
The drain terminal of the transistor TR ₁ above is connected to the resistor R ₁₉
It is connected to the adder circuit 23 via. Also,
The gate terminal of the transistor _TR1 is connected to the output terminal of the operational amplifier _OA6 . When a positive voltage is applied to the gate terminal of the transistor _TR1 , the source terminal and the drain terminal are made conductive, and when a negative voltage is applied to the transistor TR1, the source terminal and the drain terminal are cut off.

The output e ₀₄ of the gain switching circuit 24 having the above configuration (output from the drain terminal of the field effect transistor TR ₁ ) is input to the adder circuit 23 via the resistor R ₁₉ .

This gain switching circuit 24 operates as follows.

Generally, the solenoid 3a of the pressure reducing pilot valve 3
Or, the opening degree of the main spool 7 relative to the solenoid current flowing through the solenoid 3b is as shown in FIG.
When the solenoid current is small, the rate of change (diaphragm opening gain) is small, and when the solenoid current is large, the rate of change is large.

Therefore, the threshold value ith of the solenoid current is determined so that the rate of change falls within the range where tanθ ₁ changes to tanθ ₂ , as shown in FIG.
The target value signal e _s that causes the threshold value ith to flow through the solenoid 3a or 3b is selected as the threshold voltage e _th , the variable resistor VR ₃ is adjusted, and the operational amplifier OA ₃
When the threshold voltage e _th is applied to the non-inverting input terminal of the gain switching circuit 24, the gain switching circuit 24 operates as follows.

When e _s <e _th , the potential at the output terminal of the operational amplifier OA ₃ is clamped to a constant positive voltage by the Zener diode D ₁ . On the other hand, a constant negative voltage is generated at the gate terminal of the field effect transistor _TR1 by the operational amplifier _OA6 acting as an inverting amplifier. At this time,
The source terminal and drain terminal of the transistor _TR1 are cut off. As a result, the gain switching circuit 24
The output e ₀₄ becomes zero. In this case, as is clear from the third equation, the gain switching circuit 24 has no relation to the gain of the control loop of the main spool 7. Further, when e _s > e _th , contrary to the above, a positive voltage acts on the gate terminal of the transistor _TR1 , so that the source terminal and the drain terminal are electrically connected. As a result, a signal proportional to the output e' ₀₁ of the slider of the variable resistor VR ₁ is inverted and amplified by the operational amplifier OA ₄ and output to the adder circuit 24.

In this case, since the output e ₀₄ is inverted and amplified as described above, the output e' ₀₁ of the proportional-integral circuit 21 and the output e' 01 of the _feed forward circuit 22 are ′ ₀₂ changes in the opposite direction.

Therefore, as is clear from the third equation, the output e ₀₄ of the gain switching circuit 24 acts to reduce the control loop gain of the main spool 7.

However, at this time, since the control opening gain of the main spool 7 is large (see FIG. 5), the control loop gain of the main spool 7 is high and the stability of the control system is reduced, but the gain switching circuit 24 acts to reduce the control loop gain of the main spool 7, as described above. This improves the stability of the control system. On the other hand, the nonlinearity of the throttle opening characteristic of the main spool with respect to the target value signal is compensated for.

Effects of the Invention According to the first invention of the present application, the current position of the main spool is fed back to the proportional-integral circuit to control the main spool, and the control system of the main spool is controlled by the time constant by the proportional-integral circuit. At the same time, the target value signal is bypassed through the feed forward circuit, so the static accuracy of the main spool target value signal is high due to the above feedback, and the stability of the control system against disturbances etc. is improved due to the above time constant. At the same time, the sudden change component of the target value signal bypasses the proportional-integral circuit and is transmitted to the subsequent stage of the control system, thereby preventing a decrease in transient response due to the time constant of the proportional-integral circuit. can.

Further, according to the second invention of the present application, the first invention of the present application
In addition to the effects of the invention, when the target value signal exceeds the threshold set in response to the sudden change in the aperture opening gain of the main spool, the control loop gain decreases and the main spool Since the nonlinearity of the throttle opening characteristic is compensated for, the stability of the control system due to the nonlinearity is improved, and the static accuracy with respect to the target value signal of the main spool is greatly improved.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of the basic configuration of the first and second inventions of the present application, Fig. 2 is a sectional view showing the structure of the switching valve of Fig. 1, and Fig. 3 is an embodiment of the first invention of the present application. FIG. 4 is an explanatory diagram of the embodiment of the second invention of the present application, and FIG. 5 is an illustration of the throttle opening characteristic of the main spool. 14, 20... Potentiometer, 21... Proportional integral circuit, 22... Feed forward circuit,
23... Addition circuit, 24... Gain switching circuit, 25
...Main amplifier, 26...Electromagnetic proportional switching throttle valve.

Claims (1)

[Scope of Claims] 1. A pressure-reducing electromagnetic pilot valve 3 that operates according to the applied current to the solenoids 3a and 3b, and a two-stage type that operates the main spool 7 with the secondary pressure controlled by the pressure-reducing electromagnetic pilot valve. A proportional throttle valve, a position detection means 14 that detects the position of the main spool and converts it into an electric signal, and performs an addition operation between the main spool position signal (positive voltage) and a specific target value signal (negative voltage). a proportional-integral circuit 21 that integrates the result, a feed-forward circuit 22 that bypasses the target value signal to the proportional-integral circuit, and an output signal of the feed-forward circuit and an output of the proportional-integral circuit. Addition circuit 23 that outputs a signal added to the signal
A two-stage proportional throttle switching valve with a pressure-reducing pilot valve, comprising a control circuit configured to output the added signal to a drive circuit of the pressure-reducing pilot valve. 2. A pressure-reducing electromagnetic pilot valve 3 that operates according to the applied current to the solenoids 3a and 3b, a two-stage proportional throttle valve that operates the main spool 7 with the secondary pressure controlled by the pressure-reducing electromagnetic pilot valve, and the above-mentioned A position detection means 14 detects the position of the main spool and converts it into an electric signal, and adds the main spool position signal (positive voltage) and a specific target value signal (negative voltage) and integrates the result. a proportional-integral circuit 21; a feed-forward circuit 22 that bypasses the target value signal to the proportional-integral circuit; and an addition signal of the output signal of the feed-forward circuit and the output signal of the proportional-integral circuit. Addition circuit 23 to output
and a gain switching circuit 24 that connects a subtraction circuit to the input side of the addition circuit when the target value signal exceeds a threshold value determined in response to a sudden change in the aperture opening gain of the main spool. A two-stage proportional throttle switching valve with a pressure-reducing pilot valve, comprising a control circuit configured to output an output signal of the adding circuit to a drive circuit of the pressure-reducing pilot valve.