Power plants – Pressure fluid source and motor – Having condition responsive control in a system of distinct...
Patent
1992-01-09
1993-12-21
Look, Edward K.
Power plants
Pressure fluid source and motor
Having condition responsive control in a system of distinct...
60426, 60459, 60484, 91446, 91447, 91468, F16D 3102, F15B 1108
Patent
active
052712273
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a hydraulic apparatus for driving a plurality of hydraulic actuators by discharge hydraulic oil from a single hydraulic pump.
BACKGROUND ART
To drive a plurality of hydraulic actuators by a single hydraulic pump, such a parallel circuit type hydraulic apparatus A as shown in FIG. 7 has commonly been used.
In the hydraulic apparatus A, hydraulic oil discharged from a hydraulic pump B is fed to a first hydraulic actuator D1 through a first actuating valve C1 and to a second hydraulic actuator D2 through a second actuating valve C2.
However, the above-mentioned arrangement of the hydraulic apparatus A has such a drawback that if the hydraulic oil is simultaneously fed to the plurality of hydraulic actuators D1 and D2, then the quantity of hydraulic oil fed to a lower load side hydraulic actuator becomes larger which results in that a higher load side hydraulic actuator is not supplied with a sufficient quantity of hydraulic oil.
FIG. 8 shows a hydraulic apparatus which has been proposed to obviate the drawback mentioned above. In this hydraulic apparatus A', a first and a second pressure compensating valves E1 and E2 are interposed between the first actuating valve C1 and the first hydraulic actuator D1 and between the second actuating valve C2 and the second hydraulic actuator D2.
Inlet side pressures of the first and second pressure compensating valves E1 and E2 are applied as pilot pressure to the flow rate increasing side pressure receiving surfaces of the spools in the respective pressure compensating valves E1 and E2, and output pressure from a shuttle valve F interposed between a hydraulic passage extending from the first pressure compensating valve E1 to the first hydraulic actuator D1 and a hydraulic passage extending from the second pressure compensating valve E2 to the second hydraulic actuator D2, is applied as pilot pressure to the flow rate decreasing side pressure receiving surface of the respective spools.
With the foregoing hydraulic apparatus A', the maximum hydraulic pressure at the higher load side hydraulic actuator D1 or D2 is permitted to act on the flow rate decreasing side pressure receiving surfaces of the pressure compensating valves E1, E2 under the action of the shuttle valve F, so that the flow rate of hydraulic oil at that one of the pressure compensating valves which is coupled to the higher load side hydraulic actuator, is restrained, while the flow rate of hydraulic oil at that one of the pressure compensating valves which is coupled to the lower load side hydraulic actuator, is increased.
Thus, even if the first and second hydraulic actuators D1 and D2 are loaded differently, a quantity of hydraulic oil which is proportional to the hydraulic passage opening area, i.e., the extent of lever actuation in the respective actuating valve C1, C2, is distributed to the respective hydraulic actuator D1, D2, irrespective of the difference in load between the hydraulic actuators.
In the above-described hydraulic apparatus A', the outlet port side pressure of the pressure compensating valve is permitted to act on the flow rate decreasing side pressure receiving surface of the spool therein, and outlet side pressure P3 is caused to be lower than the inlet side pressure P2 of the valve due to pressure loss which tends to be caused when the hydraulic oil passes through the pressure compensating valve.
The flow rate Q1 in the lower load side pressure compensating valve and the flow rate Q2 in the higher load side pressure compensating valve are given as follows: ##EQU1## where C is a constant, and a1 and a2 are the opening areas of the respective actuating valves.
In effect, an error corresponding to the pressure loss (P2-P3) in the pressure compensating valve is induced in the quantity of hydraulic oil distributed to each hydraulic actuator.
The drawback mentioned just above can be eliminated by causing the inlet port side pressure of the pressure compensating valve to act on the flow rate decreasing side pressure receiving surface of th
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Akiyama Teruo
Ishizaki Naoki
Shinozaki Shin-ichi
Shirai Kiyoshi
Yamashita Koji
Kabushiki Kaisha Komatsu Seisakusho
Look Edward K.
Ryznic John
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