JPH0374606A - Hydraulic circuit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a hydraulic circuit that supplies pressure oil to a plurality of actuators.

[Conventional technology]

2. Description of the Related Art Conventionally, a hydraulic circuit is known in which a plurality of closed center operation valves are provided in a discharge path of a pump, and each operation valve supplies pressure oil discharged from one pump to a plurality of actuators.

In such a hydraulic circuit, when a plurality of operating valves are operated simultaneously, discharge pressure oil is supplied only to actuators with a small load, so the following problem occurs.

A pressure compensation valve is provided in the connection circuit between each operation valve and each actuator, and each pressure compensation valve is set according to the highest load pressure among the load pressures of each actuator. 1 to the actuator of
This allows for the supply of pressure oil for the discharge of two pumps.

[Object to be Solved by the Invention 1] In such a hydraulic circuit, a closed center operating valve is used, so when the operating valve is in the neutral position, the discharge side of the pump does not communicate with the tank side through the operating valve. The pressure oil discharged from the pump is compressed between the operating valve and the actuator's static stability when the operating valve is suddenly operated. It is inferior to what it would have been if it had been.

In addition, since the pump's discharge pressure oil does not flow to the tank side through the operation valve, the pressure on the pump's discharge side increases, reducing the pump's discharge flow rate to almost zero, and specifically, the maximum discharge flow rate to the extent that it can compensate for leaks in various parts. The pressure on the discharge side of the pump is set to about 5% of that so that the pressure on the discharge side of the pump does not become too high.

For this reason, when the operating valve is suddenly operated from the neutral position to supply pressure oil to the actuator, there is a time delay in increasing the pump discharge flow rate, resulting in poor responsiveness.

Therefore, an object of the present invention is to provide a hydraulic circuit that can solve the above-mentioned problems.

(Means and actions for solving problem m) The discharge path of the variable pump is connected to the tank side by a bleed-off circuit, and a bleed-off valve is provided in the bleed-off circuit, so that when the operating valve is in the neutral position, the bleed-off valve is closed. When the valve is in the communication position, the discharge pressure oil of the variable pump flows to the tank side, and when it is in the first and second pressure oil supply positions, the bleed-off valve is set to the cutoff position to prevent the discharge pressure oil of the variable pump from flowing to the tank side. This is a hydraulic circuit in which the discharge pressure oil of the variable pump is not compressed and the discharge pressure does not become high when the operating valve is in the neutral position.

〔Example〕

The discharge path 1a of the variable pump 1 is connected to the inlet side of a plurality of closed center type operation valves 2, and the outlet side of each operation valve 2 is connected to an actuator 4 via a pressure compensation valve 3. The outlet side pressure of the valve 2 is the highest in comparison among the shuttle valves 5, that is, the load pressure Po is supplied to the spring chamber side of each pressure compensation valve 3, and the pressure compensation valve 3 has a pressure corresponding to the load pressure. is set to

The swash plate 1b of the variable pump 1 is operated by the control unit 1116 by the differential pressure between the discharge pressure P and the load pressure Po to control the tilting angle, that is, the discharge flow rate.

The operation valve 2 is always held at the neutral position, and the pilot pressure oil supplied to the first and second pressure receiving parts 21*22 is used to
It is switched to the $12 pressure oil supply position, and pilot pressure oil is supplied to the first◆second pressure receiving portion 21.22 by the pilot valve 7.

The pilot valve 7 is operated by operating the operating lever 8.
Pilot pressure oil flows out to the first and second ports 7m and 7b, and the pressure is proportional to the operation stroke of the operating lever 8, and the first and second ports 7a and 7b are connected to the first and second ports. connected to the pressure receiving part 21, 22, and the shuttle valve 9
The outlet 9C is connected to the pulp 10.

The discharge path 1a of the variable pump 1 is connected to a bleed-off circuit 11.
The bleed-off circuit 11 is connected to the tank side, and a bleed-off valve 12 is provided in the bleed-off circuit 11.

The bleed-off valve 12 is held at the communication position Ill by a spring force, and is moved toward the shutoff position (1) in proportion to the pressure of the pilot pressure oil supplied to the pressure receiving part 12a. It is connected to the pulp 10.

The pulp 10 serves as a shuttle valve as shown in FIG. 2, and its outlet side is connected to the pressure receiving part 12a.

Therefore, when the operating valve 2 is in the neutral position, the pilot valve 7
is also in a neutral state and pilot pressure oil is not supplied to 1st and 2nd ports) 7m and 7b, so bleed-off valve 1
Since pilot pressure is not supplied to the pressure receiving part 12a of variable pump 2 and the pressure receiving part 12a of variable pump 1 is in communication position I, the discharge pressure oil of variable pump 1 flows to the tank side via the bleed-off circuit 11. There is no compression between the cylinders and the pressure on the discharge side is high and even.

Therefore, when the operation valve 2 is suddenly operated, the static stability of the actuator 4 is improved, and the discharge flow rate of the variable pump 1 can be increased to improve responsiveness when the operation valve 2 is suddenly operated.

Also, operate the pilot valve 7 to supply pilot pressure oil to the ill of the operation valve 2 or the second pressure receiving part 21 or 22,
When the operation valve 2 is set to the first or second pressure oil supply position, the pilot pressure is supplied to the pressure receiving part 12a of the bleed-off valve 12 via the shuttle valve 9 and the valve 10, and is sequentially moved toward the cutoff position (2) to a predetermined position. When the pilot pressure is reached, the cut-off position (3) occurs, and the pressure oil discharged from the variable pump 1 no longer flows to the tank side through the bleed-off circuit 11, so the pressure oil discharged from the variable pump 1 can be supplied to each actuator 4 with pressure compensation.

The valve 10 may be configured as shown in FIG.

In other words, the first and second pressure receiving parts 1 are set to the cutoff position ■ by the spring force.
01-102 to the communication position I, connect the outlet side of each of the shuttle valves 9 to the first and second pressure receiving parts 101 and 102, and operate the pilot valve 7 to open the operating valve 2. When this is set to the first or second pressure oil supply position, the pressure oil discharged from the pilot pressure pump 13 is prevented from being supplied to the pressure receiving portion 12a of the bleed-off valve 12.

In the above embodiment, two operation valves 2 are provided, but the same effect can be achieved even if three or more operation valves are provided.

〔Effect of the invention〕

When the operation valve 2 is in the neutral position, the bleed-off valve 12 is in the communication position ail and the discharge pressure oil of the variable pump 1 flows to the tank side, so the discharge pressure oil of the variable pump 1 is compressed between it and the operation valve 2. When the operation valve 2 is set to the first and second pressure oil supply positions, the bleed-off valve 12 is set to the cutoff position (■) and the pressure oil discharged from the variable pump 1 no longer flows to the tank side. .

Therefore, it is possible not only to improve the static stability of the actuator 4 when the operating valve 2 is suddenly operated, but also to increase the discharge flow rate of the variable pump 1 when the operating valve 2 is in the neutral position, thereby improving responsiveness. When supplying pressure oil to the system, pressure can be compensated in the same way as before.

[Brief explanation of drawings]

FIG. 1 is a hydraulic circuit diagram showing an embodiment of the present invention, and FIGS. 2 and 3 are explanatory diagrams showing different examples of valves. 1 is a variable pump, 1a is a discharge path, 2 is an operating valve, 3 is a pressure compensation valve, 4 is an actuator, 11 is a bleed-off circuit, and 12 is a bleed-off valve.

Claims (1)

[Claims] A plurality of closed center operating valves 2 are provided in the discharge path 1a of the variable pump 1, and a pressure compensation valve 3 is provided in the connection circuit between each operating valve 2 and the actuator 4. 3 is set to a set pressure corresponding to the highest load pressure, the discharge passage 1a of the variable pump 1 is connected to a bleed-off circuit 11.
A bleed-off valve 12 is provided in the bleed-off circuit 11, which is connected to the tank side at the bleed-off circuit 11 and is in the communicating position I when the operation valve 2 is in the neutral position, and in the blocking position II when the operating valve 2 is in the first and second pressure oil supply positions. A hydraulic circuit characterized by: