JPS6257857B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a closed circuit hydraulic control device.

Conventionally, as shown in the first diagram, a reversible variable displacement pump a and a reversible motor b are connected in a closed circuit c, and the pump a is reciprocatingly movable to control its discharge amount and direction. It is known that a control cylinder d is provided, and the cylinder d is operated by the pilot pressure of a pilot circuit h that selectively acts on chambers e or f on both sides of the cylinder d via a control valve g. Valve g is shown in Figures 1 and 2.
As shown in the figure, the spool i is generally constructed so that the control pressure of the control circuits j and k and the pressure of the closed circuit c introduced via the feedback circuits l and m act on the spool i. This causes the following inconveniences. That is, the control valve d shown in the first diagram cannot generate a brake pressure in the closed circuit c that would decelerate the hydraulic motor b due to the control pressure of the control circuit j or k, and when the control valve is in the neutral state, no external force is applied to the hydraulic motor b. When the pressure is generated in the closed circuit c, the pressure is transferred to the feedback circuit l.
or actuating control valve d to the switching position via m;
It is dangerous because the fluid that drives motor b is inadvertently discharged from pump a, and the control valve g shown in the second diagram
Then, hydraulic motor b can be decelerated by the brake pressure corresponding to the elasticity of the spring applied to this spool, but when the action of the control pressure is switched from, for example, circuit j to k in order to reverse hydraulic motor b, closed circuit c
, the pressure of the closed circuit c is increased, and the relief valve o of the closed circuit c tends to perform a relief operation, causing the disadvantage that the temperature of the working fluid tends to increase.

The object of the present invention is to provide a control device that does not have such inconveniences, and in which a reversible variable displacement pump and a reversible motor are connected in a closed circuit, and the discharge amount is controlled by the variable displacement pump. A reciprocating control cylinder is provided to control the discharge direction, and the pilot pressure is controlled by a spool-type control valve which is held in a neutral position by a spring and is switched by the control pressure acting against the pressure in the closed circuit. In the case where the control valve is applied to one of the chambers on both sides of the control cylinder, a force due to the pressure of the closed circuit and an opposing force due to the control pressure act on both sides of the spool of the control valve, thereby controlling the control valve. A piston is provided that switches the spool when the pressure is high, and the chambers on both sides of the control cylinder are connected to a brake control valve through the spool and the throttle, so that when the brake control valve opens, the two chambers communicate with each other. At the same time, the brake control valve is controlled to open and close by a spring and pressure in a closed circuit via the piston acting against the spring.

To explain an embodiment of the present invention with reference to FIG. 3, 1
is a reversible plunger pump or other variable displacement pump; 2 is a plunger motor or other reversible motor; 3 is a closed circuit connecting the pump 1 and motor 2; 4 is a fixed displacement pump driven together with the pump 1. An auxiliary pump 4 is shown with a replenishment circuit 6 equipped with a relief valve 5 with a relatively low set pressure.
The closed circuit 3 is replenished with working fluid via the control valve 7 via the pilot circuit 8, and the relief valve 5 is supplied via the pilot circuit 8.
Provides controlled pilot pressure.
9, 9 is a relief valve with a check valve that controls the maximum pressure of the closed circuit 3. 10 is variable displacement pump 1
When the piston 11 of the cylinder 10 is held in the neutral position by the springs 14 of the chambers 12 and 13 on both sides of the piston 11 as shown in the figure, the fluid is discharged from the variable displacement pump 1. For example, when the piston 11 is moved from the neutral position to the right in the drawing, it gradually discharges more fluid to the A side of the closed circuit 3 according to the distance of movement, and when the piston 11 is moved to the left in the drawing. is B of closed circuit 3.
Dispense more and more fluid to the side. The control valve 7 has a spool 17 maintained in a neutral position by springs 15, 15 on both sides in the valve housing, and a spool 17 is provided in the chambers 18, 19 at both ends of the spool 17 through the partition walls. A feedback circuit 22 is provided with pistons 20 and 21 having rods extending to oppose both ends of the spool 17, and introduces pressure from the A side and B side of the closed circuit 3 into each rod side of each piston 20 and 21, respectively. , 23 are connected to the piston 2, and control circuits 24 and 25 for introducing arbitrarily controlled control pressure to the head side thereof
0 or 21 pushes one end of the spool 17 when the force due to the control pressure acting on the head side is greater than the force due to the pressure of the closed circuit 3 acting on the rod side,
The pushed spool 17 bends the spring 15 at the other end and moves to the switching position. Spool 1 of the control valve 7
7, the pilot pressure in the pilot circuit 8 from the auxiliary pump 4 is changed to the operating circuit 26 or 2.
7 into either one of the chambers 12, 13 of the control cylinder 10.
3 is connected to the tank 16 via an operating circuit 26 or 27. 28 is the force of spring 29 and closed circuit 3
A brake control valve that operates at a pressure of
The spool 17 of the control valve 7 is connected to the valve 28 by connecting passages 34 and 35 equipped with throttles 32 and 33. The actuating circuits 26, 27 of the control cylinder 10 are connected thereto. An annular groove similar to that of a general spool-type valve is formed in the valve housing of the control valve 7, facing the spool land of the spool 17 located at the neutral position, and the connecting passages 34, 3
5 and the actuating circuits 26, 27 communicate in the annular groove. The valve body 30 of the valve 28 is connected to a closed circuit 3 which acts on the valve body 30 and the piston 31 via circuits 39 and 40.
When the force due to the pressure of the spring 29 is smaller than the elastic force of the spring 29, the connection paths 34 and 35 are allowed to communicate with each other via the valve body 30, and the force due to the pressure of the valve body 30 or 35 is smaller than the elastic force of the spring 29. When the force acting on the piston 31 is large, the valve body 30 slides to the right in the drawing, cutting off the communication between the connecting passages 34 and 35 therethrough. In the illustrated example, each connection path 34, 35 has a throttle 3.
2 and 33, but it is also possible to provide a throttle only in one of the connecting paths. 36 is a screw that adjusts the elastic force of the spring 29 of the brake control valve 28, and 37 is a control circuit 2 that controls the pressure from the pilot pump 38 depending on the operating direction and operating angle of the lever.
This is a joystick valve that controls and acts on one of the pressure points 4 and 25 and uses the other as the tank pressure.

To explain its operation, the joystick valve 3
7 to input control pressure into the control circuit 24, for example, the piston 20 of the control valve 7 moves to the left in the drawing, and the spool 17 is moved largely to the left switching position, so that the pilot from the auxiliary pump 4 The pressure of the circuit 8 acts via the actuating circuit 26 on the left chamber 12 of the control cylinder 10 and thus the piston 1
1 is moved to the right, the variable displacement pump 1 discharges fluid to the A side of the closed circuit 3. A of the closed circuit 3
The pressure generated on the side acts on the rod side of the piston 20 of the control valve 7 via the feedback circuit 22, but if the force due to the pressure acting on the piston 20 becomes larger than the force due to the control pressure of the control circuit 24, the The piston 20 is pushed back and the spool 17
is returned toward the neutral position by the spring 15. In this case, the pressure generated in the closed circuit 3 simultaneously acts on the valve body 30 of the brake control valve 28 via the circuit 39, thereby closing the connection paths 34 and 35. The control cylinder 10 is therefore controlled by the pressure in the chamber 12,
Furthermore, the pressure in the chamber 12 is controlled by the spool 17 of the control valve 7.
As mentioned above, when the spool 17 is returned to the neutral position and its opening becomes smaller, the pressure in the chamber 12 becomes lower and the piston 11 of the control cylinder 10 moves to the right as described above. movement is stopped, a pressure corresponding to the control pressure of the control circuit 24 can be generated in the closed circuit 3, and the motor 2 can be accelerated at a pressure corresponding to the pressure of the control circuit 24.

In order to further accelerate the motor 2, the pressure in the control circuit 24 may be further increased.
0 piston 11 moves to a position where the pressure in the closed circuit 3 is further increased and stops. For example, when the motor 2 is controlled by the pressure of the control circuit 24 and driven at an arbitrary speed, if the pressure of the control circuit 24 is lowered, the control valve 7, which was previously located on the left, will be moved.
The spool 17 and piston 20 of the left spring 1
5 and move toward the neutral position and to the right, respectively. With this movement of the spool 17, the control cylinder 10
The pressure acting on the chamber 12 becomes smaller, and the piston 11 begins to return toward the neutral position by the force of the spring 14, reducing the discharge amount of the pump 1 into the closed circuit 3. The return of the piston 11 is limited by the opening degree of the spool 17 and is slow at this time, but the piston 11 moves quickly in the next operation that occurs subsequently. That is, as the discharge amount of the pump 1 decreases, the pressure in the closed circuit 3 that is driving the motor 2 at a given speed decreases, and this pressure is applied to the brake via the feedback circuit 22 and the circuit 39 or the feedback circuit 23 and the circuit 40. The signal is transmitted to the control valve 28, and the valve body 30 is pushed by the spring 29, so the connecting circuits 34 and 35 communicate with each other, and since the spool 17 is near the neutral position, fluid is not flowing from the pilot circuit 8 to the operating circuit 26 and the connecting circuit 34. At the same time, the fluid from the operating circuit 27 and the connecting circuit 34 to the tank 16 is throttled, so the fluid in the chamber 12 on the left side of the control cylinder 10 flows from the operating circuit 26 to the connecting circuit 34 via the periphery of the spool 17. flow, further brake control valve 28, connection circuit 35,
It flows into the chamber 13 via the spool 17 and the actuating circuit 27, and the piston 11 of the control cylinder 10 moves quickly to the left in order to reduce the output of the pump 1. When the discharge amount of pump 1 decreases, B of closed circuit 3
Brake pressure is generated on the side and acts on the piston 31 of the brake control valve 28 via the feedback circuit 23, the left piston 19 of the control valve 17 and the circuit 40, so that the valve body 30 is connected to the actuation circuit 34,
Close communication between 35 and 35. Thus the control cylinder 10
Since the fluid stops flowing into the chamber 13 and its movement to the left stops, the pump 1 discharges a smaller flow rate into the closed circuit 3 than before. When the closed circuit 3 is quantified to this small flow rate, the brake pressure on the B side is also released and the brake control valve 28 is opened, but at this time, discharge pressure is generated on the A side of the closed circuit 3, and the This applied pressure keeps the brake control valve 28 closed, so that the motor 2
can perform deceleration with a pressure corresponding to the pressure of the control circuit 24. The brake pressure generated in the closed circuit 3 can be adjusted arbitrarily by adjusting the spring 29 of the brake control valve 28.
Since the set brake pressure is generated, deceleration operation can be performed without the brake pressure exceeding the set pressure of the relief valves 9,9. Brake control valve 2
8 actually exists in a balanced state in which the open and close states are frequently repeated from the time when the control pressure of the control circuit 24 is reduced until the discharge pressure is generated on the A side of the closed circuit 3.

When the operation of the closed circuit 3 is controlled by the control pressure of the control circuit 24, if the joystick valve 37 is operated to the opposite side to generate control pressure in the control circuit 25, the piston 21 of the control valve 7 moves to the right. This pushes the spool 17 and the pilot circuit 8 communicates with the actuating circuit 27 which leads to the right chamber 13 of the control cylinder 10. Due to the pressure of the pilot circuit 8, the piston 11 of the control cylinder 10 moves from the right position, where it had been discharging fluid from the pump 1 to the A side of the closed circuit 3, to the left and moves to the B side of the closed circuit 3. begins discharging fluid. The pressure generated on the B side of the closed circuit 3 acts on the piston 21 of the control valve 7 and pushes it back, and the spool 17
returns to neutral position.

Thus, the closed circuit 3 can reversely accelerate the motor 2 according to the control pressure of the control circuit 25. At this time, the force acting on the valve body 30 of the brake control valve 28 changes from the force due to the pressure on the A side of the closed circuit 3 controlled by the control circuit 24 to the B side of the closed circuit 3 controlled by the control pressure of the control circuit 25. Since the brake control valve 28 is momentarily switched to the force due to the pressure, the brake control valve 28 is temporarily opened, but immediately becomes closed.

When the control pressures of the control circuits 24 and 25 are both zero, the control cylinder 10 is in a neutral position and the hydraulic pump 1 does not discharge fluid to either side A or B of the closed circuit 3. In this case, even if an external force is applied to the motor 2 and pressure is generated on either side A or B, the control valve 7
remains neutral without operating, and the operating circuit 2
6 and 27 are in the same pressure state, so the control cylinder 10
The piston 11 also does not operate.

When the control pressure of the control circuit 24 or 25 is low, the pressure generated on the A or B side of the closed circuit 3 is also low, but in this case, if the pressure on the A or B side is lower than the set pressure of the brake control valve 28, the brake The control valve 28 is in the open state, and the amount of movement of the piston 11 of the control cylinder 10 is determined by the pressure in the operating circuit 26 or 27, which is reduced in pressure by the throttle 32 or 33.

In this way, according to the present invention, a piston is provided which is actuated by closed circuit pressure and control pressure to control the operation of the spool of the control valve, and the chambers on both sides of the control cylinder are braked through the spool and the throttle of the control valve. The motor is connected to a control valve so that when the valve opens, the two chambers communicate with each other, and the control valve is controlled to open and close by the pressure of a closed circuit via a spring and the piston acting against the spring. Brake pressure for deceleration can be generated in the closed circuit, there is no risk of the pump inadvertently starting to operate due to external force applied to the motor, and the relief valve in the closed circuit does not operate when the motor is reversed, so the working fluid This has the effect of eliminating the inconvenience of high temperatures.

[Brief explanation of the drawing]

1 and 2 are diagrams of a conventional example, and FIG. 3 is a diagram of an embodiment of the apparatus of the present invention. 1...Variable displacement pump, 2...Motor, 3...
Closed circuit, 7...control valve, 8...pilot circuit,
10... Control cylinder, 12, 13... Chamber, 14
... Spring, 15 ... Spring, 16 ... Tank, 17
... Spool, 20, 21 ... Piston, 24,
25... Control pressure, 28... Brake control valve, 2
9...Spring.

Claims (1)

[Claims] 1 A reversible variable displacement pump and a reversible motor are connected in a closed circuit, and the variable displacement pump is provided with a control cylinder that can freely move back and forth to control its discharge amount and direction, and the neutral position is maintained by a spring. At the same time, the pilot pressure is applied to one of the chambers on both sides of the control cylinder and the other chamber is connected to the tank using a spool-type control valve that is switched and operated by a control pressure that acts against the pressure of the closed circuit. A piston is provided on both sides of the spool of the control valve to act on the force due to the pressure of the closed circuit and the opposing force due to the control pressure, and to switch the spool when the control pressure is large. , the chambers on both sides of the control cylinder are connected to the brake control valve through the spool and the throttle, and when the brake control valve is opened, the two chambers are communicated with each other, and the brake control valve is connected to the spring and resists this. A hydraulic control device for a closed circuit that performs opening/closing control using pressure in the closed circuit via the piston acting on the piston.