JPH0792090B2 - Hydraulic circuit - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a hydraulic circuit that supplies pressure oil discharged from a plurality of pumps to a plurality of actuators by a plurality of operating valves.

[Conventional technology]

As shown in FIG. 2, the discharge passages 1a and 2a of the first pump 1 and the second pump 2 are connected, and a plurality of closed center type operation valves 3 are arranged in the discharge passages 1a and 1b and the operation thereof is performed. The pressure compensating valve 5 is provided in the connection circuit 4 of the valve 3 and the actuator, the maximum pressure in the load pressure of each actuator is detected by the shuttle valve 6, and the load pressure is supplied to the spring chamber 5a of each pressure compensating valve 5. A hydraulic circuit is known in which the set pressure corresponds to the load pressure.

With such a hydraulic circuit, the pressure compensation valve 5 is set by the maximum pressure of the load pressures of the plurality of actuators when the plurality of control valves 3 are simultaneously operated, and the opening of the control valve 3 is opened even if the load pressures of the plurality of actuators are different. Depending on the area ratio, multiple actuators can distribute the flow rate.

[Problems to be Solved by the Invention]

With such a hydraulic circuit, when a plurality of actuators are simultaneously operated, the pressure compensation valve is set at a higher load pressure, and the pump discharge pressure becomes a pressure slightly higher than the set pressure. When it is large, the pressure loss in the pressure compensating valve on the actuator side with a small load pressure becomes large, and when the loss horsepower of the prime mover that drives the first and second pumps 1 and 2 becomes large, the temperature of the hydraulic oil also rises. This will accelerate the deterioration of the hydraulic oil.

For example, when pressure oil is supplied to the boom cylinder and swing motor of the power shovel, and the boom descends and the upper body swings, the boom falls by its own weight, so the load pressure is low.
Since the swing motor activates and accelerates the upper vehicle body, the load pressure becomes high, and the pump discharge pressure at that time is a little higher than the set pressure.Therefore, the pressure compensating valve on the boom cylinder side causes a pressure loss between high pressure and low pressure. As described above, since the difference in load pressure is large, the pressure loss becomes large.

This is the same as when the arm cylinder raises the arm and the bucket cylinder dumps the bucket to discharge the earth and sand, the load pressure on the arm cylinder is high and the load pressure on the bucket cylinder is low.

Therefore, an object of the present invention is to provide a hydraulic circuit capable of solving the above-mentioned problems.

[Means and Actions for Solving the Problems]

The first pump 1, the plurality of operating valves 3 provided in the discharge passage 1a of the first pump 1, and the primary side pressure provided in each operating valve 3 and the connecting circuit 4 of each actuator push in the opening direction. One hydraulic circuit comprising a pressure compensating valve 5 that is pushed in the closing direction by the set pressure to make the primary side pressure a pressure commensurate with the set pressure, and the highest pressure load among the load pressures of the actuators of the one hydraulic circuit. One of the load pressure introducing passages 17 for detecting the pressure and supplying it to each pressure compensating valve 5 as a set pressure, the second pump 2, and the plurality of operating valves 3 provided in the discharge passage 2a of the second pump 2, A pressure compensating valve that is provided in each operating valve 3 and each connecting circuit 4 of each actuator is pushed in the opening direction by the primary pressure and is pushed in the closing direction by the set pressure so that the primary pressure becomes a pressure commensurate with the set pressure. More than 5 The other hydraulic circuit, the other load pressure introducing passage 18 for detecting the highest load pressure among the load pressures of the actuators of the other hydraulic circuit and supplying it as a set pressure to each pressure compensating valve 5, the first pump 1 Of the discharge pressure oil of the second pump 2 and the discharge pressure oil of the second pump 2 are supplied to the respective operation valves 3 of the other hydraulic circuit, and the discharge pressure oil of the first pump 1 is supplied to the one state. Is supplied to each operation valve 3 of the hydraulic circuit of
The pressure oil discharged from the pump 2 is supplied to each operation valve 3 of the other hydraulic circuit.
Switching means for switching to a second state in which the pressure compensation valve 5 of one of the hydraulic circuits and the pressure compensation valve 5 of the other hydraulic circuit are switched when the first switching means is in the first state.
In the first state where the set pressures are equalized, and when the first switching means is in the second state, the set pressure of the pressure compensating valve 5 of the one hydraulic circuit is set to the pressure of the one load pressure introducing passage 17. Second switching means for bringing the set pressure of the pressure compensating valve 5 of the other hydraulic circuit into the second state in which the pressure of the other load pressure introducing passage 18 is set, the first switching means and the second switching means, The hydraulic circuit is configured by means 16a, 16b for switching from the first state to the second state by pilot control when there is a large difference in the highest load pressure between the one hydraulic circuit and the other hydraulic circuit.

In this hydraulic circuit, when the first switching means is brought to the first state, the pressure compensating valve 5 provided in one hydraulic circuit and the pressure compensating valve 5 provided in the other hydraulic circuit are respectively operated by the second switching means. It is set at the highest load pressure of the actuators, and the discharge pressure oils of the first and second pumps 1 and 2 can be merged while being pressure-compensated and supplied to each of the plurality of actuators in the other hydraulic circuit.

When the discharge passage 1a of the first pump 1 and the discharge passage 2a of the second pump 2 are made independent by setting the first switching means to the second state, the pressure compensation valve 5 of one hydraulic circuit has the highest load pressure of each actuator. Since the pressure compensation valve 5 of the other hydraulic circuit is set at the highest load pressure among the load pressures of the respective actuators, the plurality of actuators connected to the discharge passage 1a of the first pump 1 and the second Pump 2
Compensation valve 5 provided in one hydraulic circuit when a plurality of actuators connected to the discharge passage 2a of
And the pressure compensating valve 5 provided in the other hydraulic circuit is set by the highest load pressure among the load pressures of the plurality of actuators, respectively, and there is a large difference between the highest load pressures of one hydraulic circuit and the other hydraulic circuit. However, the pressure loss does not increase.

〔Example〕

The discharge passage 1a of the first pump 1 is provided with a plurality of operation valves 3, for example, the swing motor 10, the arm cylinder 11, and the left traveling motor 12 are provided with the operation valve 3 for supplying pump discharge pressure oil, and the discharge passage 2a of the second pump 2 is provided. Is provided with a plurality of operation valves 3, for example, a right traveling motor 13, a boom cylinder 14, and a bucket cylinder 15, and an operation valve 3 for supplying pump discharge pressure oil is provided.
Of the load pressure introducing passage 17 and the other load pressure introducing passage 18 are combined by the merging / dividing valve 19 serving as the second switching means. It can be so.

The merging / branching valve 16 and the merging / branching valve 19 are brought into the communicating position I by the springs 16a and 19a, and are switched to the shut-off position II by the pilot pressure oil supplied to the pressure receiving portions 16b and 19b.

Then, if the merging / branching valves 16 and 19 are set to the communication position I, the discharge passage 1a of the first pump 1 and the discharge passage 2a of the second pump 2 communicate with each other,
Since the one load pressure introducing passage 17 and the other load pressure introducing passage 18 communicate with each other, the pump discharge pressure oil can be supplied to each actuator in the same manner as in the conventional case.

Further, if the pilot pressure oil is supplied to the pressure receiving portions 16a, 19b to set the merging / dividing valves 16, 19 to the shutoff position II, the discharge passage 1 of the first pump 1
Since a and the discharge passage 2a of the second pump 2 are cut off, and one load pressure introduction passage 17 and the other load pressure introduction passage 18 are cut off, a plurality of operation valves 3 provided in the discharge passage 1a of the first pump 1 And the plurality of operation valves 3 provided in the discharge passage 2a of the second pump 2 are independent.

Therefore, any one of the swing motor 10, the arm cylinder 11, the left traveling motor 12, the right traveling motor 13, the boom cylinder 14,
When one of the bucket cylinders 15 is operated at the same time and the load pressure difference is large, the junction valves 16 and 19 are set to the shutoff position II so that the pressure compensating valve 5 can be set by each load pressure. The pressure loss can be reduced because it is not set to a very high pressure.

For example, when pressure oil is supplied to the swing motor 10 and the boom cylinder 14 to swing and lower the boom at the same time, the pressure compensating valve 5 provided in the operation valve 3 of the swing motor 10 increases the pressure by the load pressure of the swing motor 10. The pressure compensating valve 5 provided on the operation valve 3 of the boom cylinder 14 is set to a low pressure by the load pressure of the boom cylinder 14, and is not set to a high pressure by the load pressure of the swing motor 10 as in the conventional case. Pressure loss is reduced.

〔The invention's effect〕

When the first switching means is set to the first state, the pressure compensating valve 5 provided in one hydraulic circuit and the pressure compensating valve 5 provided in the other hydraulic circuit by the second switching means have the highest load pressure of each actuator. The discharge pressure oils of the first and second pumps 1 and 2 are set by the load pressure, and the pressure oils can be supplied to the plurality of actuators of the other hydraulic circuit while being pressure-compensated.

When the discharge passage 1a of the first pump 1 and the discharge passage 2a of the second pump 2 are made independent by setting the first switching means to the second state, the pressure compensation valve 5 of one hydraulic circuit has the highest load pressure of each actuator. Since the pressure compensation valve 5 of the other hydraulic circuit is set at the highest load pressure among the load pressures of the respective actuators, the plurality of actuators connected to the discharge passage 1a of the first pump 1 and the second Pump 2
Compensation valve 5 provided in one hydraulic circuit when a plurality of actuators connected to the discharge passage 2a of
The pressure compensating valve 5 provided in the other hydraulic circuit is set by the highest load pressure among the load pressures of the plurality of actuators, and there is a large difference in the highest load pressure between the one hydraulic circuit and the other hydraulic circuit. In addition, the pressure loss does not increase, the horsepower loss of the prime mover driven by the pump can be reduced, and the hydraulic oil can be prevented from rapidly deteriorating without increasing the temperature of the hydraulic oil.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, and FIG. 2 is a conventional circuit diagram. 1 is a first pump, 1a is a discharge passage, 2 is a second pump, 2a is a discharge passage, 3 is an operation valve, 5 is a pressure compensating valve, 5a is a spring chamber, 16 is a merging / dividing valve, and 17 is one load pressure. Introducing path, 18 is the other load pressure introducing path, and 19 is a diverging valve.

Continuation of front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical indication location F15B 11/05 Z 8512-3H (72) Inventor Naoki Ishizaki 3-20-1 Nakase, Kawasaki-ku, Kawasaki-shi, Kanagawa Komatsu Seisakusho Kawasaki Plant (72) Inventor Takahide Takiguchi Kanase Prefecture Kawasaki City Kawasaki-ku Nakase 3-20-1 Co., Ltd. Komatsu Ltd Kawasaki Plant (56) Reference JP-A-57-116965 (JP, A) )

Claims (1)

[Claims] 1. A first pump 1, a plurality of operation valves 3 provided in a discharge passage 1a of the first pump 1, and a primary side provided in a connection circuit 4 of each operation valve 3 and each actuator. One hydraulic circuit composed of a pressure compensating valve 5 that is pushed in the opening direction by the pressure and is pushed in the closing direction by the set pressure to make the primary side pressure a pressure commensurate with the set pressure, and the load pressure of each actuator of the one hydraulic circuit. One of the load pressure introducing passages 17 for detecting the highest load pressure in the above and supplying it to each pressure compensating valve 5 as a set pressure, the second pump 2, and a plurality of operations provided in the discharge passage 2a of the second pump 2. The valves 3 and the connection circuits 4 of the respective operating valves 3 and the respective actuators are respectively provided with the primary side pressure to push in the opening direction and the set pressure to push in the closing direction.
Pressure compensating valve 5 for adjusting the secondary pressure to a pressure commensurate with the set pressure
The other hydraulic circuit, the other load pressure introducing passage 18 for detecting the highest load pressure among the load pressures of the actuators of the other hydraulic circuit and supplying it to each pressure compensation valve 5 as a set pressure, the first A first state in which the discharge pressure oil of the pump 1 and the discharge pressure oil of the second pump 2 are merged and supplied to each operation valve 3 of the one hydraulic circuit and the discharge pressure oil of the first pump 1 It supplies to each operation valve 3 of said one hydraulic circuit, and said 2nd
The pressure oil discharged from the pump 2 is supplied to each operation valve 3 of the other hydraulic circuit.
Switching means for switching to a second state in which the pressure compensation valve 5 of one of the hydraulic circuits and the pressure compensation valve 5 of the other hydraulic circuit are switched when the first switching means is in the first state.
In the first state where the set pressures are equalized, and when the first switching means is in the second state, the set pressure of the pressure compensating valve 5 of the one hydraulic circuit is set to the pressure of the one load pressure introducing passage 17. Second switching means for bringing the set pressure of the pressure compensating valve 5 of the other hydraulic circuit into the second state in which the pressure of the other load pressure introducing passage 18 is set, the first switching means and the second switching means, A hydraulic pressure characterized by comprising means 16a, 16b for switching from the first state to the second state by pilot control when there is a large difference in the highest load pressure between one hydraulic circuit and the other hydraulic circuit. circuit.