JP2920883B2 - Hydraulic actuator drive circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic actuator drive circuit for driving and controlling a hydraulic actuator provided in an aircraft or the like.

[0002]

2. Description of the Related Art When controlling a blade pitch of a flap or a helicopter of an airplane by a hydraulic actuator, high-speed response is emphasized. Therefore, when the actuator is suddenly displaced or a large load is suddenly applied to the actuator, feedback is performed. The control becomes unstable and the actuator easily oscillates.

In order to solve such a problem, there is a hydraulic actuator drive circuit that electrically detects a displacement of an actuator and feeds back a value obtained by differentiating the detected displacement to obtain a damping effect. However, in such a case where the damping effect is generated electrically, the controller becomes complicated, and there is a problem that the failure rate increases.

In contrast to such a hydraulic actuator drive circuit having an electric damping mechanism, a hydraulic actuator drive circuit having a mechanical damping mechanism has been proposed.

FIG. 2 is a schematic diagram showing a simplified configuration of a conventional hydraulic actuator drive circuit 1 having a mechanical damping mechanism. Hydraulic actuator drive circuit 1
Is composed of a hydraulic actuator 3 and an electro-hydraulic servo valve 2 for controlling the actuator 3 according to a control signal. The actuator 3 has a cylinder 17 and a piston 18 inserted into the cylinder 17. The electro-hydraulic servo valve 2 has first and second oil chambers 21 and 22 provided on the left and right of the piston 18 of the actuator 3. The actuator 3 is controlled by controlling the pressure of the hydraulic oil. A load 20 such as a helicopter rotor blade acts on the piston rod 19 of the actuator 3.

The electro-hydraulic servo valve 2 has a servo valve 38 for controlling hydraulic oil supplied to and discharged from the actuator 3.
The servo valve 38 has a sleeve 29 and a spool 4 fitted in the sleeve 29. The servo valve 38 is provided with a first oil facing a left end surface 5 of the spool 4 on the left side in FIG. The pressure difference between the chamber 7 and the second oil chamber 8 facing the other end surface 6 is controlled by the servo valve control device 10, and the spool 4 is displaced. Such a servo valve 38 has a first port 39 communicating with the first oil chamber 21 of the actuator 3 via the first pipeline 23 and a second port 24 communicating with the second oil chamber 22 of the actuator 3. It has a second port 40 that communicates with it, and supplies hydraulic oil supplied from the pressure supply port 9 of the electrohydraulic servo valve 2 from one of the pair of ports, and the cylinder of the actuator 3 from the other port. The hydraulic oil discharged by 17 is collected and discharged from the discharge port 34 of the electro-hydraulic servo valve 2.

[0007] From the pressure supply port 9, a pressure supply line 14 is provided.
The hydraulic oil is supplied to the servo valve 38 via the pressure supply port 9, and the pipeline from the pressure supply port 9 is branched to the first and second pressure control pipelines 15, 16. These first and second
The pressure control lines 15, 16 are each further branched,
One end forms nozzles 12 and 13 facing each other, and the other end is connected to the first oil chamber 7 and the second oil chamber 8 of the servo valve 38, respectively. First and second pressure control lines 1
A nozzle flapper 11 of the servo valve controller 10 is interposed between the nozzles 12 and 13 of the nozzles 5 and 16, and the nozzle flapper 11 is provided so as to be tiltable left and right in FIG. The hydraulic oil supplied from the pressure supply port 9 to each of the first and second pressure control lines 15 and 16 and the flow rate of which is restricted by the orifices 41 and 42 is directed from the nozzles 12 and 13 to the tip of the nozzle flapper 11. When the nozzle flapper 11 is at the neutral position as shown in FIG. 2, the pressure loss of each of the nozzles 12 and 13 becomes equal, so that the first oil chamber 7 and the second oil chamber of the servo valve 38 are provided. 8, the spool 4 becomes stationary.

When the nozzle flapper 11 tilts rightward, the pressure loss from the nozzle 13 increases, and the pressure in the second oil chamber 8 of the servo valve 38 becomes relatively higher than the pressure in the first oil chamber 7. Thus, the spool 4 of the servo valve 38 is displaced leftward in FIG. When the spool 4 is displaced to the left, the pressure supply line 14 and the first line 23 communicate with each other, and the second line 24 and the discharge port 34 communicate with each other. The hydraulic oil in the second oil chamber 22 is supplied to the first oil chamber 21 of the actuator 3 and discharged to the discharge port 34 via the second pipe 24.
Thereby, the piston 18 of the actuator 3 is displaced rightward.

Conversely, when the nozzle flapper 11 is tilted to the left, the spool 4 of the servo valve 38 is displaced to the right, and the pressure supply port 9 and the second oil chamber 22 of the actuator 3 communicate with each other. The oil chamber 21 communicates with the discharge port 34, and the piston 18 of the actuator 3 is displaced to the left. In this manner, the servo valve control device 10 can control the displacement of the piston 18 of the actuator 3 by tilting the nozzle flapper 11 according to the control signal.

Such a hydraulic actuator drive circuit 1
A damping mechanism composed of a pressure detection cylinder 25 and a bypass valve 26 is interposed between the first pipeline 23 and the second pipeline 24. Pressure detection cylinder 25
A first oil chamber 45 connected to the first pipe line 23 is formed at one end of the piston 27 so as to be displaceable in the cylinder 43 and on the left side of FIG. A second oil chamber 46 is formed at the other end of the piston 27. A compression spring 36 is interposed in each of the first and second oil chambers 45 and 46, and the piston 27 is elastically supported so as to return to a neutral position.

A spool 28 is inserted into the bypass piston 26 so as to be displaceable in a sleeve 30.
8 has a first oil chamber 3 connected to the second pipe 24.
The second oil chamber 32 is formed at the other end of the spool 28.
The second oil chamber 32 is connected to a second oil chamber 46 of the pressure detection cylinder 25 via a connection pipe 47.
In each of the first and second oil chambers 31, 32, a compression spring 37 is interposed, whereby the spool 28 is elastically supported so as to return to the neutral position. The bypass valve 26 is connected to the first pipe 23 via a first connection pipe 44 and connected to the second pipe 24 via a second connection pipe 35.

Therefore, when the control signal is switched and the piston 18 is suddenly displaced rightward while the piston 18 of the actuator 3 is displaced leftward, the piston 18 has been discharged to the discharge port 34 until now. Conversely, the hydraulic oil is supplied to the first pipe line 23, so that the pressure of the hydraulic oil in the first oil chamber 21 of the actuator 3 sharply increases. Also, when the piston 18 of the actuator 3 is displaced rightward and the load is suddenly applied to the piston rod 19 in a direction that hinders the displacement, the hydraulic oil in the first oil chamber 21 of the actuator 3 is As shown in FIG. 3A, the pressure of the hydraulic oil in the first oil chamber 21 of the actuator 3 rapidly increases in a step-like manner, and the hydraulic oil in the second oil chamber 22 is simultaneously increased. As shown in FIG. 3B, the pressure rapidly decreases. When the pressure of the hydraulic oil in the first oil chamber 21 rises sharply in this way, the piston 27 of the pressure detection cylinder 25 is displaced rightward against the spring force of the compression spring 36, Second oil chamber 46
The hydraulic oil in the bypass valve 26
Flows into the second oil chamber 32. A part of the hydraulic oil discharged from the pressure detecting cylinder 25 to the connecting pipe 47 escapes to the second pipe 24 via the fixed orifice 33, so that the pressure of the hydraulic oil in the second oil chamber 32 of the bypass valve 26 is reduced. Figure 3
As shown in (c), the stepwise change in pressure is differentiated, and a gentle mountain-shaped pressure change in which the peak pressure is suppressed is obtained. Further, the pressure of the hydraulic oil in the first oil chamber 31 of the pressure detection cylinder 25 is substantially equal to the pressure of the hydraulic oil in the second oil chamber 22 of the actuator 3, and is substantially the same as the pressure shown in FIG. It will change. Therefore, the bypass valve 2
6 is displaced to the left, and the first connection pipe 44 and the second connection pipe 35 communicate with each other, whereby the hydraulic oil in the first oil chamber 21 of the actuator 3 is supplied to the first pipe 23, First
The fluid flows into the second oil chamber 22 of the actuator 3 via the connection pipe 44, the second connection pipe 35, and the second pipe 24.

The hydraulic oil in the first oil chamber 31 and the hydraulic oil in the second oil chamber 32 of the bypass valve 26
3 through the first oil chamber 3 with time.
The pressure difference between the hydraulic oil in the first oil chamber 32 and the hydraulic oil in the second oil chamber 32 is reduced.
Eventually, it returns to the neutral position, and the communication between the first connection pipe 44 and the second connection pipe 35 is cut off. Therefore, the pressure change in the second connecting pipe 35 is as shown in FIG.

As described above, the first oil chamber 2 of the actuator 3
As shown in FIG. 3A, when the pressure of the hydraulic oil in the cylinder 1 rapidly rises, the hydraulic fluid flows into the second oil chamber 22 of the actuator 3 via the pressure detection cylinder 25 and the bypass valve 26, and then flows into the first oil chamber. An abrupt pressure difference between 21 and second oil chamber 22 is reduced, and a damping effect is obtained.

[0015]

In the hydraulic actuator drive circuit 1 having such a conventional mechanical damping mechanism, the pressure difference between the first oil chamber 21 and the second oil chamber 22 of the actuator 3 rises sharply. Then, the first hydraulic pressure 21 and the second hydraulic pressure 22 of the actuator 3 are communicated via the pressure detection cylinder 25 and the bypass valve 26 to suppress the peak pressure and provide a damping effect. If the damping mechanism breaks down, for example, adheres to the spool 28 of the bypass valve 26 and sticks in a state where the spool 28 is displaced, the first connection pipe 44 and the second connection pipe 35 are always in communication. ,
That is, the first oil chamber 21 and the second oil chamber 2 of the actuator 3
2 is always in a state of communication, which causes a problem that the actuator 3 cannot be controlled.

The damping effect is obtained by the fixed orifice 3
Since it depends on the hydraulic oil passing through the hydraulic fluid 3, there is a problem in that the contaminants and air mixed in the hydraulic oil cause variations in the damping effect. As described above, the reliability of the conventional hydraulic actuator drive circuit 1 is reduced with respect to the failure of the damping mechanism and the intrusion of air of the hydraulic oil.

An object of the present invention is to provide a hydraulic actuator drive circuit having a highly reliable damping mechanism against failure or air mixing.

[0018]

SUMMARY OF THE INVENTION The present invention comprises a cylinder,
A hydraulic actuator comprising a piston displaced in accordance with a pressure difference in the cylinder, a spool, a first oil chamber facing one end face of the spool, and a second oil chamber facing the other end face of the spool; A spool is displaced by controlling a pressure difference between the first oil chamber and the second oil chamber in accordance with the control signal, and hydraulic oil is supplied to the cylinder from one of the pair of ports, and is supplied from the other port. A servo valve for collecting hydraulic oil discharged from the cylinder, a pressure detecting means having a detecting piston elastically supported so as to be displaced in accordance with a pressure difference of the cylinder and to return to a neutral position; Pressure feedback having a return piston interposed in the middle of a pipeline communicating with the second oil chamber and interlocking with the detection piston and displacing the spool in a direction to reduce the pressure difference between the first oil chamber and the second oil chamber. With means A hydraulic actuator drive circuit according to claim and. According to the present invention, the spool of the servo valve that controls the hydraulic actuator is controlled by the pressure difference between the first oil chamber and the second oil chamber. That is, by increasing the pressure in the first oil chamber in response to the control signal, the spool is displaced toward the second oil chamber, and when the spool is displaced in this way, one of the two ports of the servo valve is moved from one of the ports. Hydraulic oil is supplied to the cylinder, and the hydraulic oil discharged from the cylinder is collected from the other port. This causes a pressure difference in the cylinder of the hydraulic actuator, and the piston of the hydraulic actuator is displaced in accordance with the pressure difference. In this way, the servo valve is controlled by displacing the piston of the hydraulic actuator according to the control signal.
Such a hydraulic actuator drive circuit includes a pressure detection unit that is displaced in accordance with a pressure difference between cylinders, a pressure feedback unit that displaces a spool in a direction that reduces a pressure difference between the first oil chamber and the second oil chamber. Is provided. Therefore, for example, when the piston of the hydraulic actuator is displaced to one side, the displacement direction of the spool of the servo valve is switched to rapidly displace the piston of the hydraulic actuator to the other, or to the piston displaced by the hydraulic actuator, If the pressure difference in the cylinder of the hydraulic actuator suddenly increases due to a sudden load being applied in a direction that hinders the displacement, the detection piston of the pressure detection means is displaced against the elastic force. When the detection piston is displaced, the first pressure is returned by the pressure feedback means linked to the detection piston.
The spool is displaced in a direction in which the pressure difference between the oil chamber and the second oil chamber decreases. When the spool is displaced in this manner, the amount of hydraulic oil supplied to the cylinder decreases, and thereby the pressure difference in the cylinder decreases. That is, a sudden pressure difference in the cylinder is suppressed, and a damping effect is obtained, whereby the stability of control of the hydraulic actuator is compensated. The damping mechanism of the present invention comprising such a pressure detecting means and a feedback means has a structure in which a sudden pressure difference in the cylinder is fed back to the servo valve to generate a damping effect. Even if the damping mechanism breaks down, for example, if the return piston is stuck, only the damping effect cannot be obtained, and the problem that the hydraulic actuator cannot be controlled as in the above-described conventional technique is prevented. Further, since the damping mechanism of the present invention does not have a configuration that obtains a damping effect via a fixed orifice unlike the related art, the damping effect varies depending on the state of the hydraulic oil such as contaminants in the hydraulic oil or the mixing of air. The problem that air bubbles occur does not occur, and the reliability against air mixing and the like is improved.

Further, the present invention is characterized in that it comprises a displacement detection sensor for detecting a displacement amount of a piston of the hydraulic actuator, and a feedback circuit for feeding back a detection output of the displacement detection sensor to a control signal. According to the present invention, the displacement of the piston is detected by the displacement detection sensor, and the detection output is fed back to the control signal, so that the displacement of the cylinder of the actuator can be controlled with high accuracy.

[0020]

FIG. 1 is a schematic diagram showing the configuration of a hydraulic actuator drive circuit 60 according to an embodiment of the present invention. The hydraulic actuator drive circuit 60 includes a hydraulic actuator 62 and an electro-hydraulic servo valve 61 that controls the actuator 62 according to a control signal. The electro-hydraulic servo valve 61 has a servo valve 63 and a servo valve control device 72 for controlling the servo valve 63 according to a control signal. The servo valve 63 is displaceably fitted into the sleeve 59 and the sleeve 59. A first oil chamber 68 is formed facing one end face 67 on the left side of FIG. 1 of the spool 66, and faces the other end face 69 on the right side of the spool 66 in FIG. Thus, the second oil chamber 70 is formed.

The actuator 62 includes a cylinder 73,
The cylinder 73 can be displaced in the left-right direction on the plane of FIG.
A first oil chamber 75 of the actuator 62 is formed on the left of the piston 74, and a second oil chamber 76 of the actuator 62 is formed on the right of the piston 74. A piston rod 79 is connected to a piston 74 of the actuator 62, and a load 80 such as a rotor blade of a helicopter or a flap of an airplane acts on the tip of the piston rod 79.

The servo valve 63 has a first port 91 and a second port 92. The first port 91 is connected to a first oil chamber 75 of the actuator 62 via a first pipe 77, and a second port 92 Is connected to a second oil chamber 76 of the actuator 62 via a second conduit 78. Hydraulic oil is supplied to the servo valve 63 from a pressure supply port 64 of the electro-hydraulic servo valve 61 via a pressure supply line 65, and hydraulic oil is supplied from one of the first and second ports 91 and 92. The hydraulic oil is supplied to the cylinder 73 of the actuator 62, and the hydraulic oil discharged from the cylinder 73 is recovered from the other port and discharged from the discharge port 71 of the electro-hydraulic servo valve 61.
A first pressure control line 84 and a second pressure control line 85 branch off from the pressure supply port 64, and the first and second pressure control lines 84 and 85 further branch off, respectively, with one ends facing each other. The other ends of the first and second oil chambers 68 and 7 of the servo valve 63 are formed.
0. Servo valve controller 72
Has a nozzle flapper 90 interposed between the nozzles 86 and 87 and capable of tilting left and right. Pressure supply port 64
From the first pressure control line 84 and the second pressure control line 85
The hydraulic oil supplied via the orifices 8
The flow rate is restricted by 8, 89, and hydraulic oil is injected from nozzles 86, 87 toward nozzle flapper 90. The servo valve controller 72 tilts the nozzle flapper 90 left and right in response to a control signal in the same manner as the above-described conventional servo valve controller 10, thereby forming the first oil chamber 68 and the second oil chamber of the servo valve 63. The spool 66 is displaced by controlling the pressure difference with the chamber 70.

For example, when the nozzle flapper 90 is tilted to the left, the pressure in the first oil chamber 68 of the servo valve 63 increases, and the spool 66 moves to the right, whereby the pressure supply line 65 and the second line 78 and the first conduit 7
7 communicates with the discharge port 71, and the piston 74 of the actuator 62 moves to the left. Conversely, when the nozzle flapper 90 is tilted rightward, the second
The pressure in the oil chamber 70 increases, and the spool 66 moves to the left, whereby the pressure supply pipe 65 and the first pipe 77 communicate with each other, and the second pipe 78 and the discharge port 71 communicate with each other. The piston 74 of the actuator 62 moves rightward. Thus, the actuator 62 is controlled by the electro-hydraulic servo valve 61 according to the control signal.

Such a hydraulic actuator drive circuit 6
0 is provided with a damping mechanism including a pressure detection device 93 and a pressure feedback device 94. Pressure detector 93
Has a cylinder 95 and a detection piston 96 that is inserted into the cylinder 95 so as to be displaceable left and right in FIG. 1. A first oil chamber 97 of the pressure detection device 93 is formed on the left side of the detection piston 96, and a second oil chamber 98 of the pressure detection device 93 is formed on the right side of the detection piston 96. ,
Is connected to the first pipe 77 via the first connecting pipe 100,
The second oil chamber 98 is connected to the second pipe 78 via the second connection pipe 101. A compression spring 99 is interposed in each of the first and second oil chambers 97 and 98, whereby the detection piston 96 is elastically supported so as to return to the neutral position.

The pressure feedback device 94 has a cylinder 103 and a return piston 104 which is inserted into the cylinder 103 so as to be displaceable left and right. The return piston 104 is connected to a detection piston 96 of the pressure detection device 93 by a piston rod 102. Are connected via. The return piston 104 is provided on the side to which the connecting piston rod 102 from the pressure detecting device 93 is connected, that is, on the left side in FIG.
4, a first oil chamber 105 is formed, and a second oil chamber 106 of the pressure feedback device 94 is formed on the right side of the return piston 104. The second oil chamber 106 is connected to the first oil chamber 68 of the servo valve 63 via a first return line 107, and the first oil chamber 105 of the pressure feedback device 94 is servo-controlled via a second return line 108. The valve 63 is connected to the second oil chamber 70.

The first oil chamber 75 and the second oil chamber 76 of the actuator 62 are displaced by displacing the spool 66 of the servo valve 63.
And the piston 7 of the actuator 62
4 is controlled, the first oil chamber 75 and the second oil chamber 75 are usually controlled.
Since the pressure difference from the oil chamber 76 is not so large, the detection piston 96 of the pressure detection device 93 is stopped at the neutral position by the spring force of the compression spring 99.

On the other hand, when the spool 66 of the servo valve 63 is displaced rightward and the piston 74 of the actuator 62 is displaced leftward, the displacement direction of the spool 66 of the servo valve 63 is rapidly switched. And spool 66
Is displaced to the left so that the piston 74 of the actuator 62
Is suddenly displaced to the right, or when the spool 66 is displaced to the left and the piston rod 79 is displaced to the right. , The pressure of the hydraulic oil in the first oil chamber 75 rapidly increases, whereby the detection piston 96 of the pressure detection device 93 is displaced rightward against the spring force of the compression spring 99. When the detection piston 96 is displaced rightward, the pressure feedback device 9 is connected via the connecting piston rod 102.
4 is displaced rightward in conjunction with the return piston 104.

When the return piston 104 is displaced rightward,
Hydraulic oil is supplied to the servo valve 63 via the first return line 107.
Is supplied to the first oil chamber 68 of the servo valve 63, and the operating oil of the second oil chamber 70 of the servo valve 63 is guided to the first oil chamber 105 of the pressure feedback device 94 and the first oil chamber 68 of the servo valve 63 and the second oil Room 7
The pressure difference from zero decreases. As a result, the displacement of the spool 66 that has been displaced to the left is reduced, and a sudden increase in the pressure of the first oil chamber 75 of the actuator 62 is suppressed. That is, a damping effect is given to the actuator 62, and thereby the stability of the hydraulic actuator drive circuit 60 is compensated. Conversely, when the pressure of the hydraulic oil in the second oil chamber 76 of the actuator 62 suddenly increases,
The first oil chamber 6 of the servo valve 63 is operated in the same manner as described above.
The pressure difference between the oil chamber 8 and the second oil chamber 70 is reduced, and a damping effect is given to the actuator 62.

Even if the damping mechanism fails, for example, if the pressure detecting device 93 or the pressure feedback device 94 of such a damping mechanism sticks in a state where the pistons 96 and 104 are displaced due to, for example, contaminants, the damping mechanism is damped by the actuator 62. Only the effect is not obtained, and the problem that the control of the actuator becomes impossible as in the above-described conventional technique is prevented. Also, since the damping effect is not obtained through the fixed orifice as in the above-described conventional technology, the problem that the damping effect varies due to the mixing of hydraulic oil air and the like and the control becomes unstable is prevented. And the actuator 6
Since this peak pressure is suppressed in proportion to the magnitude of the peak pressure in the second cylinder 73, controllability is improved.

The displacement of the piston rod 79 of the actuator 62 is detected by a displacement detection sensor 81 such as an LVDT (Linear Differential Transformer). The detection output from the displacement detection sensor 81 is fed back to a subtractor 82 to which a control signal is input.
Then, the difference between the control signal and the detection output is calculated and given to the amplifier 83, and the difference between the control signal and the detection output of the displacement of the piston rod 79 is amplified by the amplifier 83 and input to the servo valve control device 72. The displacement of the piston rod 79 of the actuator 62 can be accurately controlled by the feedback circuit including the displacement detection sensor 81 and the subtractor 82.

[0031]

As described above, according to the present invention, the drive circuit of the hydraulic actuator controlled by the servo valve is provided with the pressure detecting means and the pressure feedback means.
When an abrupt pressure difference occurs in the cylinder of the hydraulic actuator, the displacement of the spool of the servo valve is reduced by the pressure detecting means and the pressure feedback means, and a sudden increase in the pressure of the cylinder is suppressed. That is, the damping effect is given to the hydraulic actuator, and the stability of the hydraulic actuator is compensated. Even if such a pressure detecting means or a pressure feedback means fails, the control of the actuator cannot be disabled as in the related art,
The reliability against failure is improved. In addition, the damping mechanism of the present invention does not provide a damping effect through a fixed orifice as in the prior art, so that there is no variation in the damping effect with respect to the mixing of hydraulic oil air, and the reliability is further improved. Be improved.

Further, according to the present invention, since the displacement detection sensor and the feedback circuit for feeding back the output of the displacement detection sensor to the control signal are provided, the displacement of the piston of the hydraulic actuator can be accurately controlled.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating a configuration of a hydraulic actuator drive circuit 60 according to an embodiment of the present invention.

FIG. 2 is a schematic diagram showing a simplified configuration of a conventional hydraulic actuator drive circuit 1 having a mechanical damping mechanism.

FIG. 3 shows a first oil chamber 21 and a second oil chamber 2 of the actuator 3.
2 is a graph showing a relationship between each pressure P1, P2, P3, and P4 of the hydraulic oil in the second oil chamber 32 and the second connection pipe line 35 of the bypass valve 26 and the passage of time.

[Explanation of symbols]

 Reference Signs List 60 Hydraulic actuator drive circuit 61 Electro-hydraulic servo valve 62 Hydraulic actuator 63 Servo valve 64 Pressure supply port 66 Spool 67 One end face 68 First oil chamber 69 Other end face 70 Second oil chamber 73 Cylinder 74 Piston 81 Displacement detection sensor 93 Pressure detector 94 Pressure feedback device 96 Detection piston 104 Return piston

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-52-19875 (JP, A) JP-A-63-145801 (JP, A) JP-A-3-223504 (JP, A) 70293 (JP, U) (58) Field surveyed (Int. Cl. ⁶ , DB name) F15B 9/08 F15B 11/00

Claims (2)

(57) [Claims] 1. A hydraulic actuator comprising a cylinder, a piston displaced according to a pressure difference in the cylinder, a spool, a first oil chamber facing one end face of the spool,
A second oil chamber facing the other end surface of the spool, and controlling a pressure difference between the first oil chamber and the second oil chamber in accordance with a control signal to displace the spool, thereby to set one of the pair of ports; A servo valve that supplies hydraulic fluid to the cylinder from one port and collects hydraulic fluid discharged from the cylinder from the other port. A pressure detecting means having a piston, interposed in the middle of a pipe communicating with the first oil chamber and the second oil chamber, and interlocking with the detection piston to detect a pressure difference between the first oil chamber and the second oil chamber. Pressure feedback means having a return piston for displacing the spool in a decreasing direction. 2. The hydraulic actuator according to claim 1, further comprising: a displacement detection sensor that detects a displacement amount of a piston of the hydraulic actuator; and a feedback circuit that feeds back a detection output of the displacement detection sensor to a control signal. Drive circuit.