JPS60249708A - Flow line selector valve - Google Patents

Abstract

PURPOSE:To relax shock upon changeover of a flow line, by providing an orifice and a check valve for permitting flow to a pressure oil supply passage as arranged in series to the orifice in a flow line bypassing the pressure oil supply passage to a cylinder, and communicating the flow line to a drain or a pump discharge oil passage. CONSTITUTION:While a piston 11 is being moved rightwardly, a pressure oil is fed through a selector valve 3 to a left chamber of a cylinder 10. There are provided an orifice 38a and a check valve 36a in a branch flow line 34, so as to permit a small amount of pressure fluid fed to the left chamber via the branch flow line 34. As to a right chamber of the cylinder, there is provided the same arrangement. Accordingly, even when an electromagnetic selector valve 2 is selected so as to reverse a moving direction of the piston, a small amount of the pressure oil is fed into the cylinder before a spool of the fluidic selector valve 3 is moved, thus relaxing shock upon changeover of the flow line.

Description

[Detailed Description of the Invention] a9 Purpose of the Invention (Field of Industrial Application) The flow path switching valve according to the present invention is capable of controlling pressure applied to hydraulic actuators such as hydraulic cylinders and hydraulic motors incorporated in various hydraulic machines. Used to control liquid supply and discharge.

(Prior Art) Hydraulic actuators such as hydraulic cylinders and hydraulic motors are incorporated in cranes, T-machines, press machines, and other various hydraulic machines. In order to change the operating direction of such a hydraulic actuator, the supply and discharge direction of the pressure fluid is switched using a separately provided flow path switching valve. However, when switching the pressure fluid supply direction tJj in this way, if the flow path is suddenly switched, a shock will be generated on the actuator due to the sudden change in fluid pressure, which will not only prevent the hydraulic machine from operating smoothly. Otherwise, it may cause damage to the actuator or hydraulic machine.

For this reason, the flow path switching valve is conventionally configured as shown in FIG. 9 to prevent impact from occurring on the hydraulic actuator when switching the supply/discharge direction of the pressure fluid. This flow path switching valve consists of an electromagnetic switching valve 2 whose flow path is switched by the action of solenoids 1a and lb, and a hydraulic switching valve 3 whose flow path is switched by pressure fluid sent through the electromagnetic switching valve 2. It has become. The pressure liquid that is sucked from the liquid tank 4 by the pump 5 and whose pressure has increased is transferred to the first port 7 of the electromagnetic switching valve 2 through the first flow path 6 and then through the 20th flow path 8. Each communicates with a first port 9 of the pressure switching valve 3.

Now, when the piston 11 fitted in the hydraulic cylinder 10 is moved to the right and the rod 12 is to be protruded, the spool of the switching valve 3 is moved to the right by energizing the solenoid Fla on the left side of the electromagnetic switching valve 3. The flow path is moved to the right against the compression spring 13b, and the flow path is switched to the left end state, and the first port 7 and the third port h14 are connected to the second port 15 and the fourth port 16, respectively. let For this reason, the pressure fluid passes through the left cylinder portion 18a of the hydraulic switching valve 3 through the check valve 61a provided in parallel with the throttle valve 28a in the middle of the third flow path 17 whose one end is connected to the third port 14. The spool of this hydraulic switching valve 3 is connected to the compression spring 19 on the right side.
b to the right and switch the flow path to the left end state. At this time, the liquid in the right cylinder portion 18b flows through the fourth flow path 2o.
, is returned to the liquid tank 4 through the flow path of the electromagnetic switching valve 2. Since the throttle valve 28b is provided in the middle of the fourth flow path 20, the spool of the hydraulic switching valve 3 moves slowly, and the first port 9 and the third port of the hydraulic switching valve 3 move slowly. The port 21, the second port 22, and the fourth port 23 are slowly connected to each other, and the hydraulic sill 1 is connected through the fifth flow path 24.
Pressure liquid is sent little by little into the left ventricle 25 of o. At this time, the liquid in the right chamber 33 of the hydraulic cylinder 10 is returned to the liquid tank 4 through the sixth flow path 26, the hydraulic switching valve 3, and the seventh flow path 27.

When retracting the rod 12 of the hydraulic cylinder 10, contrary to the above case, the solenoid 1b on the right side of the electromagnetic switching valve 2 is energized to switch the flow path of this switching valve 2 to the right end state, and accordingly Switch the flow path of the hydraulic switching valve 3 to the right end state.

As shown in FIG. 10, the hydraulic switching valve 3 includes a spool 31, which is made up of alternating large-diameter portions 29 and small-diameter portions 30, and is fitted inside a cylinder cylinder in a liquid-tight manner so as to be slidable in the axial direction. The first to fourth ports 9.22.2 are opened in the cylinder by adjusting the position of the spool 31.
1.23 communication is controlled. Large diameter part 29
A V-shaped groove 32 whose cross-sectional area gradually increases toward the small diameter part 30 is formed in each end edge of the spool 31. When the spool 31 moves, each port first communicates through this V-shaped groove 32, and the ports are connected to each other through the V-shaped groove 32. This prevents pressure fluid from flowing vigorously from the beginning.

(Problems to be Solved by the Invention) However, in the conventional flow path switching valve that is configured and operates as described above, the impact prevention effect when switching the flow path is still insufficient, and hydraulic type It was inevitable that some impact would be applied to the actuator.

It is an object of the present invention to provide a flow path switching valve that can minimize the occurrence of impact when switching the flow paths.

b1 Configuration of the Invention (Means for Solving the Problem) The flow path switching valve of the present invention has one end connected in the middle of a flow path that sends the pressure fluid discharged from the electromagnetic switching valve to the cylinder portion of the hydraulic switching valve. The other end of the branch flow path is connected to the hydraulic actuator without going through the hydraulic switching valve, and there is a check valve in the middle of the branch flow path that allows the pressure fluid to flow only towards the hydraulic actuator, and a check valve for flowing the pressure fluid only. Control parts that act as resistance are installed in series with each other, and if necessary, a pressure compensation type flow is installed in one of the flow path for feeding pressure liquid to the cylinder part and the branch flow path! ---
The present invention is characterized in that a control valve is provided in series with the reverse 1-hi valve and the control section.

That is, as shown in FIG. 1, a third flow path 17 that communicates between the third port 14 on the pressure fluid discharge side of the electromagnetic switching valve 2 and one cylinder portion 18a of the hydraulic switching valve 3 is provided. The other end of the first branch flow path 34 connected with one end is connected to the third port 21 on the pressure fluid discharge side of the hydraulic switching valve 3 and the hydraulic cylinder 1.
It is connected in the middle of a fifth flow path 24 that connects one of the supply and discharge ports of a hydraulic actuator such as No. 0 or the like.

Similarly, the fourth port 16 on the pressure fluid discharge side of the electromagnetic switching valve 3
The other end of the second branch channel 35, which has one end connected to the middle of the fourth channel 20, which has one end connected to the fourth channel 20, is connected to the fourth port on the pressure fluid discharge side of the hydraulic pressure switching valve 3 and the It is connected to the middle of the sixth flow path 26 that connects the other port. Throttle valves 28a, 28 in the middle of the third and fourth flow paths 17.20
When the check valves 61a and 61b are provided in parallel with the check valve 61b, the direction of each check valve is reversed from the conventional case shown in FIG. 9, but this check valve may be omitted.

In the middle of each of the first and second branch channels 34 and 35, there is a check valve 37a that allows the pressure liquid to flow only toward the hydraulic actuator.
37b, control portions 38a, 38b which serve as resistance to the pressure fluid flowing through each branch pipe 34, 35, and pressure-compensated flow control valves 36a, 36b, if necessary, are provided in series with each other. Each pressure compensation type flow control valve 36a, 36b allows only pressure liquid below a certain pressure to flow backward, and each branch flow path 3
4.35 When a pressure liquid of a certain pressure or higher is sent into the chamber, the flow path is closed and the pressure liquid is prevented from being sent to a hydraulic actuator such as a hydraulic cylinder. However, when the pressure compensation type flow control valves 36a and 36b are provided, the third and fourth ports 2 of the hydraulic switching valve 3 are connected in the middle of the second and fourth flow paths.
1.23 and the branch part of the branch flow path,
In this case, the throttle valves 28a and 28b can be omitted.

The other components are the same as the conventional flow path switching valve shown in FIG. 9. Next, the operation of the flow path switching valve of the present invention will be explained while adding a description of the parts that are equivalent to the conventional flow path switching valve.

(Function) When a hydraulic actuator such as the hydraulic cylinder 10 is stopped, neither of the solenoids 1a and 1b of the electromagnetic switching valve 2 is energized, and the switching valve 2 is shown in FIG. hold it in the same condition. For this reason, the hydraulic fluid sent via the first flow path 6 to the first port 7 of the electromagnetic switching valve 2 is not sent to any other port 14.15.16, so that the hydraulic Pressure liquid is not sent to any of the cylinder parts 18a, 18b of the switching valve 3, and the first to fourth ports 9, 21, 22, 24 of this hydraulic switching valve 3 are all
It will be in the closed state shown in the figure.

Therefore, the liquid in the left and right chambers 25, 33 of the hydraulic cylinder 10 is not supplied or discharged, and the piston 11 of the hydraulic cylinder 10 does not move.

Next, when moving the piston 11 of the hydraulic cylinder 10 to the right and protruding the rod 12, the left solenoid la of the electromagnetic switching valve 2 is energized, and the spool of the switching valve 2 is moved to the right side of the compression spring 13b. Move it to the right against the elastic force. Therefore, the first port 7 and the third port 1 of the electromagnetic switching valve 2
4, a second port 15 and a fourth port 16 are in communication with each other, and the pressure liquid sent to the first port 7 through the first flow path is transferred from the third port 14 to the third flow path. It is fed into the left cylinder portion 18a of the hydraulic switching valve 3 through the passage 17. As a result, the spool of the hydraulic switching valve 3 moves to the right against the right compression spring 19b, and the first port 9
, the third port 21 , the second port 22 , and the fourth port 24 communicate with each other. However, as the spool goes to the right, the right cylinder part l
The liquid in Bb is discharged slowly due to the action of the throttle valve 28b (pressure compensation type flow control valve 36b if the throttle valve is omitted) provided in the middle of the fourth flow path 20, so that the left cylinder It takes some time after the pressurized liquid is sent into the section 18a until the ports communicate with each other.

On the other hand, a branch flow path 34 branched from the middle of the third flow path 17
Pressure fluid is directly fed into the left chamber 25 of the hydraulic cylinder 10 without passing through the hydraulic switching valve 3. however,
In the middle of the branch flow path 34, there is a control portion 38a that acts as a resistance to the flow of liquid, and a pressure compensation type flow control valve 36a as the case may be.
Because of this, the flow rate of the pressurized liquid sent into the left ventricle 25 through this branch flow path 34 is small, and if the control valve 36a is provided, the pressure will also be below a certain value. Therefore, the piston 11 of the hydraulic cylinder 10 receives a shock from the hydraulic pressure and slowly starts moving to the right.

After a short period of time has passed immediately after the electromagnetic switching valve 2 is switched, the spool of the hydraulic switching valve 3 has completed its rightward movement, and the flow from the second flow path 8 to the first port 9 of the switching valve 3 has been completed. The pressurized liquid sent into the left chamber 25 is sent from the third port 21 through the fifth flow path 24, causing the piston 11 to quickly move to the right.

As the piston 11 moves to the right, the right chamber 3 of the hydraulic cylinder 10
The liquid pushed out from the liquid tank 3 is returned to the liquid tank 4 via the sixth flow path 26, the hydraulic switching valve 3, and the seventh flow path 27.

Further, the liquid pushed out from the right cylinder portion 18b as the spool of the hydraulic switching valve 3 moves to the right flows through the fourth flow path 20.
．． The liquid is returned to the liquid tank 4 via the electromagnetic switching valve 2.

Move the piston 11 of the hydraulic cylinder 10 to the left, and move the rod 1
2, in order to retract the hydraulic switching valve 3, the right solenoid lb of the electromagnetic switching valve 2 is energized, the spool of the switching valve 2 moves to the left, and the hydraulic switching valve 3 moves to the left. When the spool is moved to the left, the pressure fluid sent through the second flow path 8 is sent into the right chamber 33 of the hydraulic cylinder 10 via the hydraulic switching valve 3 and the sixth flow path 26, and the piston ll. move to the left. At this time, immediately after the electromagnetic switching valve 2 is switched, pressure liquid below a certain pressure is fed little by little into the right chamber 33 through the second branch flow path 35, and the piston 11 slowly starts moving to the left. .

(Example) Next, the illustrated embodiment will be described.

2 to 8 show embodiments of the flow path switching valve of the present invention.

At the center of the electromagnetic switching valve 2, which is provided with solenoids ta and tb at both left and right ends, there is provided a cylinder part 39, which is made up of five large diameter parts and four small diameter parts that are arranged in series alternately on the inside. A spool 40 is fitted inside the portion 39 so as to be slidable in the left and right direction. This spool 40 has two large diameter parts with an outer diameter approximately equal to the inner diameter of the small diameter part of the cylinder part 39, spaced apart from each other, and both end surfaces are directed toward the center by compression springs 13a and 13b. They are suppressing it. Therefore, when neither of the solenoids 1a and 1b is energized, the spool 40 is stopped at the central position shown in FIG.

The five large-diameter portions of the cylinder portion 39 include, in order from the large-diameter portion on the left side, a discharge passage 60, a third passage 17, and a first passage 6.
, the fourth passage 20, and the discharge passage 60 are open at one end, and among these passages 60, 17.6.20.60, the discharge passage and the first passage 60.6.60 are respectively open. The other end opens to the cylinder portion 41 of the hydraulic switching valve 3, and the other end of each of the third and fourth flow paths 17.20 opens to the pressure compensation type flow control valve 36a.
, 36b, respectively.

The cylinder portion 41 of the hydraulic switching valve 3 is made up of six small diameter portions and five large diameter portions that are alternately continuous, and the discharge passages 60 and 60 are provided in the large diameter portions at both left and right ends. The first flow passages each open at the central large-diameter portion. Also, 2 from the left
The fifth large diameter section has a fifth flow path 24 leading to one pressure fluid supply/discharge port of the hydraulic actuator, and the second large diameter section from the right has a fifth flow path 24 leading to the other pressure fluid supply/discharge port of the hydraulic actuator. A sixth flow path 26 communicates with the first flow path 6 and a second flow path 8 opening in the large diameter portion at the center. Furthermore, a cylindrical sleeve 42 having an outer diameter matching the inner diameter of the six small diameter portions is fitted into the cylinder portion 41, so that the outer peripheral surface of the sleeve 42 and the five large diameter portions are connected to each other. Short cylindrical gaps 43a to 43e are formed with the inner peripheral surface. As shown in FIG. 7, the sleeve 42 is provided with a large number of through holes 44.44, which are large and small, and these through holes 44.44 allow the gaps 43a to 43e to communicate with the inside of the sleeve 42. . A spool 45 for switching the axillary passage is fitted inside the sleeve 42 so as to be slidable in the left-right direction. Small diameter portions 46a and 46b are formed at two locations on the outer circumferential surface of the spool 45 with an interval between them, and a narrow passage 47 is formed with one end opened in each of the small diameter portions 46a and 46b.
The other ends of a and 47b (corresponding to the branch channels 36a and 36b in FIG. 1) are open to both end surfaces of the spool 45, respectively. The cross-sectional areas of the two-line passages 47a and 47b are smaller than the cross-sectional areas of the other channels, and serve as resistance when liquid passes through, and correspond to the control portions 38a and 38b in FIG. 1. The inner diameters of both wire passages 47a and 47b are made slightly larger near the openings at both ends, and the compression springs 48 and steel balls 49 are inserted into these larger diameter portions in order from the back, and finally a circular tubular sleeve 50 is press-fitted and fixed. These constitute check valves 37a and 37b, respectively.

A spool 4 incorporating such check valves 37a and 37b
Cylinder part 1 provided so as to surround both left and right end portions of 5.
Compression springs 19a, 19b are provided between the end faces of 8a, 18b and the ring body 51 loosely fitted to both end portions of the spool 45, and when no pressure liquid is sent to any of the cylinder parts 18a, 18b, the spool 45 is maintained in the neutral position shown in FIG.

Adjacent to these two cylinder parts 18a, 18b, pressure compensation type flow control valves 36a, 3 as shown in detail in FIG.
6b is provided. This flow control valve 36a (36b
The cylinder section of the hydraulic switching valve 3 is operated by a piston 53 that is slidably fitted in the left-right direction into a cylinder section 52 in which the end of the third (or fourth) flow path 17 is open. 1
It controls the opening and closing of the through hole 54 communicating with 8a (or 18b). A compression spring 57 is provided between the piston 53, which is formed entirely in a cylindrical shape and has an orifice-shaped portion 55 at one end opening, and the end surface of a hollow bracket 56 screwed onto the end opening of the cylinder portion 52. , elasticity is imparted to the piston 53 in the direction of opening the through hole 54 toward the flow path 17. A needle 59 having a tapered tip is screwed into the center hole 58 of the bracket 56 . A tapered end portion of the needle 59 is inserted into the orifice-shaped portion 55 of the piston 53. When pressure liquid is sent from the first branch flow path 34 side to the pressure compensation type flow control valve 36a configured as described above, a gap between the outer circumferential surface of the tip of the needle 59 and the inner circumferential edge of the orifice-shaped portion 55 increases. Since it is narrow, it takes some time for the pressure on the left side of the piston 53 to rise, and the piston 53 is pushed by the pressure fluid to move to the left and the through hole 54 is closed. After a short period of time, the pressure on the left side of the piston 53 increases, and the piston 53 moves to the right due to the elasticity of the compression spring 57, opening the through hole 54. Therefore, the pressure liquid on the left side of the piston 53 is sent to the cylinder portion 18a through the through hole 54, but the cross-sectional area of the through hole 54 is equal to the outer peripheral surface of the tip of the needle described above and the orifice-shaped portion 55.
When the through hole 54 is fully opened, the supply of pressure fluid from the flow path 17 side cannot keep up with the discharge of pressure fluid from the left side of the piston 53. The pressure on the left side decreases and the piston 53 tries to move to the left again. After performing such an operation, the piston 53 almost stops in a state where the cross-sectional area of the gap between the needle and the orifice, the opening area of the through hole 54, and the elasticity of the compression spring 57 are balanced. From the through hole 54, a constant pressure liquid is sent little by little toward the cylinder portion 18a. The amount of pressurized liquid sent toward the cylinder portion 54 can be adjusted by rotating the needle 59 and moving it in the left-right direction in the drawing.

Pressure compensated flow control valve 36 configured and operated in this manner
The operation of the flow path switching valve incorporating elements a and 36b is as follows.

When holding a hydraulic actuator in a stopped state,
Neither of the solenoids 1a and 1b is energized, and the spool 40 of the electromagnetic switching valve 2 is maintained in the state shown in FIG. As a result, the pressure liquid is not sent to any of the flow paths beyond the first and second flow paths 6.8, and the hydraulic actuator is held in a stopped state.

Next, when moving the hydraulic actuator (when retracting the rod 12 of the hydraulic cylinder 10 in FIG. 1),
Energize either solenoid lb? f. Move the spool 40 of the magnetic switching valve 2 to the right as shown in the third view. As a result, the first #path 6 and the fourth flow path 20 communicate with each other,
The pressure liquid flows from the first flow path 6 to the fourth flow path 20, the pressure compensated flow control valve 36b, the cylinder portion 18b, the check valve 37, the narrow passage 47b, the through hole 44 of the sleeve 42, and the sixth flow path. 26 to a hydraulic actuator, which slowly activates the actuator.

By feeding pressure fluid into the cylinder portion 18b, the spool 45 of the hydraulic switching valve 3 moves to the left against the elasticity of the left compression spring 19a, and accordingly, the left cylinder portion of the switching valve 3 moves to the left. As shown by the arrow in FIG.
7. The liquid is returned to the liquid tank via the discharge channel 60, and the remainder is sent to the hydraulic actuator via the check valve 37a and the fifth channel 24. However, since the pressure in the fifth flow path 24 immediately becomes higher than the pressure in the cylinder portion 8a, the check valve 37a is closed early.

When the spool 45 of the hydraulic switching valve 3 moves further to the left as shown in FIG. 44. At the same time, the second flow path 8 and the sixth flow path 26 communicating with one of the supply and discharge ports of the hydraulic actuator are communicated via The flow path 24 communicates with a seventh flow path 27 leading to the liquid tank. As a result, pressurized liquid is sent from one supply/discharge port of the hydraulic actuator, and liquid is discharged from the other supply/discharge port, thereby rapidly driving the actuator.

When stopping the hydraulic actuator after it has been moved, the energization to the solenoid 1b of the electromagnetic switching valve 2 that had been continued until then is stopped, and the spool 4 of this switching valve 2 is stopped.
0 is returned to the neutral position as shown in FIG. As a result, the right cylinder section 18 of the hydraulic switching valve 3
The pressure fluid sent into the pressure compensation type flow regulating valve 3
6b, fourth flow path 20, electromagnetic switching valve 2, discharge flow path 60
is returned to the liquid tank via the Also, the left cylinder chamber 1
8a includes a discharge channel 60. Liquid is sent through the third flow path 17 and the pressure-compensated flow control valve 36a. For this reason, the spool 45 of the hydraulic flow path switching valve 3 immediately doubles into the state shown in FIG. Cut off communication with the flow path.

When moving the hydraulic actuator in another direction, the other solenoid la of the electromagnetic switching valve 2 may be energized.

C1 Effects of the Invention Since the flow path switching valve of the present invention is configured and operates as described above, it is possible to minimize the impact generated by switching the flow path when starting the hydraulic actuator, and to control various hydraulic pressures. It is possible to improve the durability of working machines by smoothing their movement.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram of the flow path switching valve of the present invention, Figs. 2 to 6 are cross-sectional views showing embodiments of the flow path switching valve of the present invention according to the operation stroke, and Fig. 7 is a circuit diagram of the flow path switching valve of the present invention. FIG. 8 is an enlarged view of a pressure compensation type flow control valve, FIG. 9 is a circuit diagram of a conventional flow path switching valve, and FIG. 1O is a partial perspective view of a conventional spool. . la, 1b: solenoid, 2: electromagnetic switching valve, 3: hydraulic switching valve, 4: liquid tank, 5: pump, 6: first flow path, 7: first port, 8: second flow path, 9: first port, 10: hydraulic cylinder, 11: piston, 12: rod, 13a, 13b: compression spring, 14: @ third port,
15: second port, 16: fourth port, 17: third flow path, 18a, 18b cylinder part, 19a, 19b
: compression spring, 20: fourth flow path, 21: third port,
22: second port, 23: fourth port, 24: fifth flow path, 25: left ventricle, 26: sixth flow path, 27: seventh flow path, 28a, 28b: throttle valve, 29: Large diameter part, 30:
Small diameter part, 31 varnish spool, 32: 7-shaped groove, 33: right ventricle,
34: First branch flow path, 35: Second branch flow path, 36a
, 36b: pressure compensation type flow control valve, 37a, 37b: check valve, 38a, 38b = control part, 39 cylinder part,
40 nis spool, 41 niji cylinder part, 42 nis sleeve,
43a to 43e: gap, 44: through hole, 45 varnish spool,
46a, 46b: Small diameter part, 47a, 47b: Narrow passage, 4
8: compression spring, 49: steel ball, 50 sleeve, 51: ring body, 52 cylinder part, 53: piston, 54: through hole,
55 Niorifice-shaped part, 56: Bracket, 57: Compression spring, 58: Center hole, 59: Needle, 60: Discharge channel, 61a, 61b: Check valve. Patent applicant: Koshin Rashin Co., Ltd. Agent: Kinzo Koyama (and one other person) Figure 5 Figure 6 λ1244aB26 Figure 7 Figure 8

Claims (1)

[Claims] 1) Communication between the first and second ports provided on the l side and the third and fourth ports provided on the other side is controlled by a solenoid, and the A flow path whose one end is connected to the third and fourth ports of an electromagnetic switching valve that switches the state of sending pressure liquid to either the third or fourth port or not sending it to either port. The other end is connected to a cylinder section provided opposite to both ends of the spool of a hydraulic switching valve that moves the spool using hydraulic pressure to switch the communication state between the supply/discharge port of the hydraulic actuator and the pressure fluid supply device. In the flow path switching valve, one end of the branch flow path is connected in the middle of the flow path connecting both cylinders and the third and fourth ports of the electromagnetic type switching valve, and the other end is connected via a hydraulic type switching valve. A check valve is provided in the middle of this branch flow path to allow pressure fluid to flow only towards the supply and discharge port of the actuator, and a resistance against the pressure fluid flowing through the branch flow path is provided. A flow path switching valve characterized in that a control part and a control part are provided in series with each other. 2) Using a solenoid to control communication between the first and second ports provided on the l side and the third and fourth ports provided on the other side,
To the third and fourth ports of the electromagnetic switching valve that switches the pressure liquid sent to the first port to either the third or fourth port or not to send it to either port. The other ends of the channels, each connected at one end, are provided opposite to both ends of the spool of a hydraulic switching valve that moves the spool using hydraulic pressure to switch the communication state between the supply/discharge port of the hydraulic actuator and the pressure fluid supply device. In a flow path switching valve connected to a cylinder section, both cylinder sections and the third solenoid switching valve,
The other end of the branch flow path, one end of which is connected to the middle of the flow path connecting the fourth port, is connected to the supply/discharge port of the hydraulic actuator without going through the hydraulic switching valve. ,
A check valve that allows pressure fluid to flow only toward the supply/discharge port of the actuator, and a control portion that provides resistance to the pressure fluid flowing through the branch flow path are installed in series with each other. A flow path switching valve characterized in that a pressure compensation type flow control valve is provided on one side of the flow path leading to the port in series with the check valve and the control section.