JPH03189404A - Hydraulic circuit - Google Patents

Abstract

PURPOSE:To improve responsiveness of volume control and facilitate processing by connecting a detecting pipe passage which is connected to an output side of a changeover valve in respect to a pressure receiving part of an operational valve through a shuttle valve, to one of a pressure receiving part of a volume control valve through a solenoid proportional pressure reducing valve to be controlled by a controller, and connecting the other pressure receiving part to a discharge passage of a variable volume pump. CONSTITUTION:Ports 9, 10 of a pilot pressure changeover valve 7 which is provided on a discharge passage 8a of an auxiliary pump 6 are connected to pressure receiving parts 5, 5 of an operational valve 5. A detecting passage 14 which is connected to the passage 6a through a shuttle valve 13 is connected to a first pressure receiving part 15a of a volume control valve 15 through a solenoid proportional pressure reducing valve 16, while discharge pressure of a variable volume pump 1 is input to a second pressure receiving part 15b. Outlet pressure of the changeover valve 7 is input to a controller 17 through a pressure sensor 18, and electric supply to a solenoid 16a is controlled. It is therefore possible to improve responsiveness of volume control of a pump 1, and facilitate adjusting and processing of time matching between the responsiveness above and changeover responsiveness of the operational valve 5.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a hydraulic circuit that supplies pressure oil discharged from a variable displacement pump to an actuator using a switching valve.

[Conventional technology]

In a hydraulic circuit that supplies the discharge pressure oil of a variable displacement pump to an actuator using a pilot pressure-operated switching valve that switches and operates the discharge pressure oil by the pilot pressure supplied to the pressure receiving part, if the switching valve is an open center type, switching is performed. When the valve is in the neutral position, the pump boat and tank boat communicate, and the discharge pressure oil flows into the tank and is wasted.If the switching valve is a frozen center type, the pump boat is shut off when the switching valve is in the neutral position. The discharge pressure oil becomes a dead end and the pressure becomes high.

For this purpose, in the case of an open center type switching valve, a flow rate sensor (jet sensor) is installed in the drain path connected to the tank boat, and the pilot pressure supplied to the pressure receiving part of the switching valve is used to spring the spool of the switching valve. The flow rate flowing into the drain path was reduced when the pump boat and the tank boat were communicated with each other to supply discharge pressure oil to the actuator by displacing the pump boat from the neutral position and reducing the communication area between the pump boat and the tank boat. is detected by a flow sensor, and the detection signal increases the capacity of the variable displacement pump.When the switching valve is in the neutral position, the flow rate flowing through the drain passage increases, which is detected by the flow sensor, and the detection signal increases the capacity of the variable displacement pump. The capacity of the variable displacement pump is reduced to prevent waste from flowing into the tank.

In addition, in the case of a closed center type switching valve, a load sensing circuit is installed to detect the load pressure of the actuator, and the capacity of the variable displacement pump is controlled based on the load pressure detected by this load sensing circuit. At the neutral position, the capacity is kept small to prevent the discharge pressure from becoming high.

[Problem to be solved by the invention]

In such a hydraulic circuit, after the pilot pressure displaces the spool of the operating valve from the neutral position against the spring, the flow rate sensor detection signal and load pressure are generated as a capacity control signal, so the capacity of the variable displacement pump is increased. Not only is the control response poor, but the switching response of the operating valve and the capacity control response cannot be controlled separately, so it is necessary to adjust the shock mitigation of the actuator through smooth pressure rise and the temporal matching of both responses. Can not.

In addition, in the case of the latter hydraulic circuit, it is necessary to provide a cutout passage hole for detecting the load pressure in the spool of the operating valve, making the structure of the operating valve complicated and laborious to process.

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] By controlling the displacement of a variable displacement pump using pilot pressure and discharge pressure for switching operation valves, it is possible to improve pump displacement control responsiveness and to improve pump displacement control. The response and operation valve switching response can be controlled individually to adjust the temporal matching of both responses, and there is no need to form a cutout or passage hole for load pressure detection on the operation valve spool, and the consumption is reduced. This is a hydraulic circuit that can maintain constant torque.

〔Example〕

As shown in Fig. 1, a variable displacement pump (hereinafter simply referred to as pump) 1 has a capacity changing member (hereinafter simply referred to as swash plate) 2.
This swash plate 2 is controlled by a cylinder 3, and the cylinder 3 is urged by a spring 4 in the direction of smaller displacement, and the pressure receiving chamber 3
The pressure inside a moves toward larger capacity.

A plurality of operating valves 5 are provided in the discharge path 1a of the pump 1, and the operating valves 5 are closed center type pilot operated operating valves, and the pilot operating valves 5 are supplied to the first and second pressure receiving parts 51 and 5□. It is displaced from the neutral position N by pressure and switched to the first and second pressure oil supply positions in.

A pilot pressure switching valve 7 is provided in the discharge passage 6a of the auxiliary pump 6, and when the operating lever 8 is operated from the neutral position n to the first and second positions
- A pilot pressure proportional to the operating stroke is supplied to the second port 9.
It is connected to the first and second pressure receiving parts 51, 5□, and
The highest pilot pressure in the shuttle valve 13 is detected by the detection path 14.
The detection path 14 is connected to a pressure receiving portion 15a of a capacity control valve 15 that connects and controls the discharge path 6a of the auxiliary pump 6 to the pressure receiving chamber 3a of the cylinder 3.

The capacity control valve 15 is in the cutoff position A when the pressure of the first pressure receiving part 15H and the pressure of the second pressure receiving part 15b are equal, and the first
When the pressure in the pressure receiving part 15a becomes small, the drain position B is set, and when the pressure in the first pressure receiving part 15a becomes large, the supply position C is set.
When the capacity control valve 15 is in the drain position B, the pressure oil in the pressure receiving chamber 3a flows out to the tank, and the swash plate 2 is operated in the direction of reducing the capacity. The swash plate 2 is operated in the direction of increasing capacity by being supplied with the discharge pressure oil of the auxiliary pump 6, the first pressure receiving part 15a is connected to the detection path 14, and the second pressure receiving part 15b is connected to the discharge path of the pump 1. Connected to 1a.

The detection path 14 is provided with an electromagnetic proportional pressure reducing valve 16, and the outlet pressure of the electromagnetic proportional pressure reducing valve 16 is lowered depending on the current value of the solenoid 16a.
A current is supplied from the controller 17.

The outlet pressure of each pilot pressure switching valve 7, that is, the pilot pressure, is inputted to the controller 17 by a pressure sensor 18, and the pilot pressure of each pilot pressure switching valve 7 is summed,
A current inversely proportional to the total pilot pressure is applied to solenoid 1.
6a, and as a result, the electromagnetic proportional pressure reducing valve I
The set pressure of 6 is set by operating lever 8 of each pilot pressure switching valve 7.
The value corresponds to the total number of operation strokes.

Note that the controller 17 is set with an appropriate current output cover turn for the type of pilot pressure switching valve 7 operated and the operating direction (actuator operating direction).
It is designed to determine whether the operation is single or combined, and calculate the appropriate current output accordingly.

Therefore, when the operating lever 8 is operated to operate the pilot pressure switching valve 7, a pilot pressure corresponding to the operating stroke is outputted to the first or second passage 11, 12 and facing the pilot pressure switching valve 7. The operation valve 5 is switched to supply discharge pressure oil to the actuator.

At the same time, pilot pressure is detected in the detection path 14, and the pilot pressure is supplied to the first pressure receiving part 15a of the capacity control valve 15, and the capacity control valve 15 moves to 0 (supply position C) and discharges the auxiliary pump 6. Pressure oil is supplied to the pressure receiving chamber 3a of the cylinder 3, and the swash plate 2 operates in the direction of increasing the capacity, increasing the discharge amount of the pump 1, so the capacity control responsiveness of the pump 1 improves,
When the pressure in the discharge path la of the pump 1 increases, the pressure in the second pressure receiving part 15b of the capacity control valve 15 increases and reaches the drain position B, and the pressure in the pressure receiving chamber 3a of the cylinder 3 decreases, and the swash plate 2 Since the pump 1 operates in the direction of decreasing capacity, the capacity of the pump 1 can be controlled in inverse proportion to the discharge pressure, so that the torque consumption of the pump 1 can be kept constant.

In addition, since the switching response of the operation valve 5 and the pump displacement control response can be controlled individually, it is possible to reduce the shock of the actuator due to a smooth pressure rise and to temporally match the switching response of the operation valve 5 and the pump displacement control response. Can be adjusted.

Furthermore, when a plurality of pilot pressure switching valves 5 are switched simultaneously, the highest pressure of each pilot pressure is detected in the detection path 14, and a current that is inversely proportional to the total operating stroke of the plurality of pilot pressure switching valves 7 is sent to the solenoid from the controller 17. 16
a, the output pressure of the electromagnetic proportional pressure reducing valve 16 becomes a pressure corresponding to the total operation stroke, and the pyro nod pressure supplied to the pressure receiving part 15a of the capacity control valve 15 becomes high pressure, and the pressure in the pressure receiving chamber of the cylinder 3 becomes high. The pressure inside 3a increases and the swash plate 2
operates in the direction of increasing capacity, so the capacity of the pump 1 has a value corresponding to the opening degree of the fifth operation valve.

〔Effect of the invention〕

Since the displacement control valve 15 is operated using the pilot pressure for switching the operation valve 5 and the discharge pressure to control the displacement of the variable displacement pump 1, pump displacement control responsiveness is improved, and
Not only can the operating valve switching response and pump displacement control response be controlled individually to adjust the temporal matching of both responses, but the spool of the operating valve can be formed with a cutout passage hole for detecting load pressure ( This makes processing easier and allows the pump torque consumption to be constant.

Even if the electrical system such as the controller 17 breaks down, the pump capacity can be controlled.

[Brief explanation of drawings]

FIG. 1 is a hydraulic circuit diagram showing an embodiment of the present invention. 1 is a variable displacement pump, 1a is a discharge path, 2 is a capacity control member, 3 is a cylinder, 5 is an operation valve, 7 is a pilot pressure switching valve, 13 is a shuttle valve, 14 is a detection path, 15 is a capacity control valve, 16 is an electromagnetic proportional pressure control valve, and 17 is a controller.

Claims (1)

[Claims] A capacity control valve 1 that is provided with a pilot-operated operation valve 5 in a discharge path 1a of a variable capacity pump 1 and supplies pressure oil to a cylinder 3 that operates a capacity control member 2 of the variable capacity pump 1.
5, a pilot pressure switching valve 7 for supplying pilot pressure to the pressure receiving part of the operating valve 5 is provided, and a detection path 14 is connected to the output side of the pilot pressure switching valve 7 via a shuttle valve 13. The passage 14 is connected to the first pressure receiving part 15a of the capacity control valve 15 via the electromagnetic proportional pressure reducing valve 16, and the second pressure receiving part 15b is connected to the discharge passage 1a of the variable displacement pump 1. A controller 17 is provided to energize the solenoid 16a of the valve 16, and the outlet pressure of the pilot switching valve 7 is input to the controller 17 to control the solenoid 1.
A hydraulic circuit that controls the amount of electricity supplied to 6a.