JPH0419407A - Hydraulic circuit - Google Patents

Abstract

PURPOSE:To prevent generation of drive sound when an operation valve is restored to the neutral position by controlling capacity of a hydraulic pump by a selector valve in such a way that it decreases at pump discharge pressure and increases at load pressure, and connecting a circuit which leads load pressure into the selector valve to a tank via a throttle. CONSTITUTION:A tilted plate 11 is operated by large and small diameter pistons 12, 13, and a selector valve 14 which operates the large diameter piston 12 is mounted in a hydraulic pump 10 which increases and decreases discharge amount and a circuit 10a which leads to an operation valve 15. The high pressure side of load pressure at an outlet of the operation valve 15 is selected by a shuttle valve 21, and load pressure is led into a pressure receive section 14a of the selector valve 14 via a circuit 23. On the other hand, it is branched from the circuit 23 and connected with a tank 25 via a throttle 24. Consequently, when the operation valve 15 is set to the neutral position, it is possible to reduce load pressure rapidly and prevent generation of drive sound of the hydraulic pump 10 so that operator does not feel a sense of incongruity.

Description

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

[Conventional technology]

In order to supply pressure oil discharged from one hydraulic pump to multiple hydraulic actuators, it is sufficient to provide multiple operating valves in the discharge path of the hydraulic pump and supply pressure oil to each hydraulic actuator by switching the operating valves. Otherwise, when pressure oil is supplied to a plurality of hydraulic actuators at the same time, pressure oil is supplied only to the hydraulic actuators with a small load, and no pressure oil is supplied to the hydraulic actuators with a large load.

As a hydraulic circuit that solves this problem, for example, JP-A-59
The one shown in Japanese Patent No. 197603 has been proposed.

Such a hydraulic circuit is schematically shown in FIG.

That is, a plurality of operation valves 2 are provided in the discharge path 1a of the hydraulic pump 1, and pressure compensation valves 5 are provided in the circuits 4 connecting each operation valve 2 and each hydraulic actuator 3, and the pressure in each circuit 4, that is, the load The highest pressure in the pressure is detected by the shuttle valve 6, and the detected load pressure is applied to each pressure compensation valve 5.
When the pressure on the outlet side of each operation valve 2 is equalized and each operation valve 2 is operated simultaneously, each operation valve 2 is divided at a dividing ratio proportional to the opening area of each operation valve 2. This allows pressure oil to be supplied to the hydraulic actuator 3.

[Problem to be solved by the invention]

With such a hydraulic circuit, the function of the pressure compensating valve 5 makes it possible to distribute the flow rate in proportion to the opening area of the operating valve 2, regardless of the magnitude of the load on each hydraulic actuator 3. It can be supplied to each hydraulic actuator 3 in proportion to the amount of operation of the operation valve 2.

However, the capacity (discharge flow rate per rotation) of the hydraulic pump 1 is controlled by the pump pressure and load pressure so that the capacity becomes smaller when the pump pressure increases and becomes larger when the load pressure decreases. In the neutral position, discharge path 1
A and the circuit 4 are cut off, the circuit 4 is blocked, and a load pressure remains, and the pump capacity does not decrease until the load pressure decreases due to leaks from various parts.

For this reason, the capacity of the hydraulic pump 1 increases for a predetermined period of time after the operator returns the operating valve 2 to the neutral position, producing a hydraulic pump drive sound and giving the operator a sense of discomfort.

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

[Means and effects for solving the problem] A circuit that introduces load pressure to a switching valve that controls the capacity of a hydraulic pump is connected to a tank through a throttle, and when the operation valve is set to the neutral position, the load pressure in the circuit is It is designed so that the temperature decreases immediately.

〔Example〕

As shown in FIG. 1, the hydraulic pump 10 is a variable displacement hydraulic pump in which the displacement, that is, the discharge flow rate per rotation, is changed by changing the angle of the swash plate 11.
The large diameter piston 12 tilts in the direction of decreasing capacity, and the small diameter piston 13 tilts in the direction of increasing capacity.

The pressure receiving chamber 12a of the large diameter piston 12 is communicated with and cut off from the discharge passage 10a of the hydraulic pump 10 by a switching valve 14, and the pressure receiving chamber 13a of the small diameter piston 13 is connected to the discharge passage 10a.

A plurality of operation valves 1 are provided in the discharge passage 10H of the hydraulic pump 10.
5 are provided, each operation valve] 5 and a hydraulic actuator 1.
A pressure compensation valve 18 is provided in each of the circuits 17 connecting the 6 and 6, and the pressure compensation valve 18 is pushed to the low pressure setting side by the pressure oil of the first pressure receiving part 19, and is pushed to the high pressure setting side by the pressure oil of the second pressure receiving part 20. The first pressure receiving part 19 is connected to the outlet side of the operation valve 15 and is supplied with outlet side pressure, and the second
The pressure receiving section 20 is connected to each circuit 17 via a shuttle valve 21 and is supplied with the highest load pressure.

The switching valve 14 is pushed in the communication direction by the pressure in the discharge passage 10a, and pushed in the drain direction by the spring 22 and the load pressure, and when the discharge pressure P increases, the discharge pressure is applied to the pressure receiving chamber 12a of the large diameter piston 12. is supplied to tilt the swash plate 11 in the capacity decreasing direction, and when the discharge pressure P becomes low, the pressure receiving chamber 12a of the large diameter piston 12 flows out to the tank side and the swash plate 11 is tilted in the capacity increasing direction.

A circuit 23 that supplies the load pressure to the pressure receiving section 14a of the switching valve 14, that is, a circuit 23 that connects the pressure receiving section 14a and the output side of the shuttle valve 21, is connected to a tank 25 through a throttle 24.

Next, the operation will be explained.

When the operating valve 15 is set to the pressure/[t] supply position I, the pressure oil discharged from the hydraulic pump 10 or the hydraulic actuator 16 is
At the same time, the load pressure is supplied to the shuttle valve 21, the circuit 2
3 to the pressure receiving part 14a of the switching valve 14.

At this time, the pressure oil flowing into the circuit 23 is passed through the throttle 24 and into the tank 2.
5, or because pressure oil always flows in, the pressure on the upstream side of the throttle 24 is maintained and supplied to the pressure receiving part 14a of the switching valve 14 as load pressure.

When the operating valve 15 is set to the neutral position N from the above-mentioned state, the discharge passage 10a and the circuit 17 are blocked, but the pressure oil in the circuit 23 flows out from the throttle 24 to the tank 25, and the load pressure in the circuit 23 rapidly increases. The pressure receiving chamber 12a of the large-diameter piston 12 communicates with the discharge passage 10a, and the capacity of the hydraulic pump 10 immediately becomes the minimum.The discharge flow rate of the hydraulic pump 10 decreases and the pump pressure decreases, so that the drive of the hydraulic pump 10 decreases. The sound becomes quieter.

〔Effect of the invention〕

With the operation valve 15 at the neutral position N, the discharge path 10a and the circuit 17
When the hydraulic pump 1 is blocked, the pressure oil in the circuit 23 that introduces the load pressure flows out into the tank 25 through the throttle 24 and the pressure in the circuit 23, that is, the load pressure, decreases rapidly.
When the displacement of 0 is set to the neutral position N of the operation valve 15, it immediately becomes the minimum, and the driving sound of the hydraulic pump 10 is not generated, so that the operator does not feel uncomfortable.

[Brief explanation of the drawing]

FIG. 1 is a hydraulic circuit diagram showing an embodiment of the present invention, and FIG. 2 is a hydraulic circuit diagram of a conventional example. 10 is a hydraulic pump, 10a is a discharge path, 14 is a switching valve, 1
5 is an operating valve, 16 is a hydraulic actuator, 17 is a circuit,
18 is a pressure compensating valve, 19°20 is the first and second pressure receiving part, 2
3 is the circuit, 24 is the aperture, and 25 is the tank.

Claims (1)

[Claims] A plurality of operation valves 15 are provided in the discharge path 10a of the hydraulic pump 10, and a pressure compensation valve 18 is provided in the connection circuit between each operation valve 15 and each hydraulic actuator 16, and each pressure compensation valve 1
8 is set at the highest pressure among the load pressures of each hydraulic actuator 16, the switching valve 14 that controls the displacement of the hydraulic pump 10 is operated in the direction of decreasing the displacement by the pump discharge pressure, and the load pressure A hydraulic circuit characterized in that a circuit 23 that operates in the direction of capacity increase and that guides the load pressure to a switching valve 14 is connected to a tank 25 via a throttle 24.