Fluid handling – Line condition change responsive valves – Pilot or servo controlled
Patent
1997-02-04
1998-03-24
Ferensic, Denise L.
Fluid handling
Line condition change responsive valves
Pilot or servo controlled
1374925, 137906, 137489, F15B 1105, F15B 1116
Patent
active
057301824
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a pressure compensation valve to be employed in a hydraulic circuit for distributing in flow rate a discharged pressurized fluid of one or more hydraulic pumps in a constructional machine for supplying a plurality of actuators.
BACKGROUND ART
Supplying a discharge pressurized fluid of a hydraulic pump to a plurality of actuators, can be done by providing a plurality of operation valves in a discharge path of the hydraulic pump and supplying a pressurized fluid to respective hydraulic actuators by switching the operation valves. With such construction, upon supplying the pressurized fluid to a plurality of hydraulic actuators simultaneously, the pressurized fluid may supplied to only hydraulic actuators having small load, and not pressurized fluid can be supplied to the hydraulic actuator having large load.
As a hydraulic circuit solving the problem, there has been proposed one disclosed in Japanese Unexamined Patent Publication No. Showa 59-197603.
This is constructed by providing a plurality of operation valves in a discharge path of a hydraulic pump, providing pressure compensation valves in circuits connecting respective operation valves and respective hydraulic actuators, respectively, detecting the highest load pressure among pressures, namely load pressure in all of the circuits by a shuttle valve, setting respective pressure compensation valve at a pressure corresponding to the load pressure by applying the detected load pressure to respective pressure compensation valves and whereby equalizing the output side pressures of the operation valves to enable supply of the pressurized fluid to respective actuators at distribution ratio proportional to open areas of respective operation valves when respective operation valves are operated simultaneously.
In such hydraulic circuit, since flow amount can be distributed proportional to open areas of respective operation valves without respect to large and small of the load pressures in respective hydraulic actuators, by the function of the pressure compensation valves. Therefore, the discharged pressurized fluid of one hydraulic pump can be supplied to respective hydraulic actuators proportionally to operation amount of the operation valves.
As the pressure compensation valve to be employed in such hydraulic circuit, there is one illustrated in FIG. 1, for example.
Namely, this is constructed by coaxially forming a bore 8 communicating an inlet port 1 and an outlet port 2 and a mounting bore 9 opening to the output port 2, in the valve body 7. In the bore 8, a valve 3 for establishing and blocking communication between the inlet port 1 and the output port 2 are slidably disposed. Within a sleeve 4 threadingly engaged with the mounting bore 9, a piston 5 pushing the valve 3 in blocking direction is slidably disposed. Between the sleeve 4 and the piston 5, a pressure receiving chamber 6 is defined. Then, the piston 5 is pushed by a pressure (load pressure) P2 in the pressure receiving chamber 6 in a direction for pushing the valve 3 in blocking direction so that a pressure (inlet pressure) P3 of the input port 1 becomes equal to the pressure P2.
In the conventional pressure compensation valve as set forth above, a force for pushing the piston 5 in the blocking direction is a product of an area A of a pressure receiving portion 5a of the piston 5 and the load pressure P2. Thus, when the area A becomes greater, the force for pushing the piston 5 in the blocking direction becomes greater to make the inlet pressure P3 higher, and when the area A becomes smaller, the force for pushing the piston 5 in the blocking direction becomes smaller to make the inlet pressure P3 lower.
Therefore, in order to vary a pressure compensation characteristics (the inlet pressure P3 according to the same load pressure P2), the area A of the pressure receiving portion 5a of the piston 5 may be varied. For example, when the pressure receiving area A of the pressure receiving portion 5a is set greater, the force to pushing the piston 5
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Ishizaki Naoki
Takano Toshiro
Ferensic Denise L.
Kim Joanne Y.
Komatsu Ltd.
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