Motors: expansible chamber type – With motive fluid valve – Relatively movable serial valves
Patent
1996-01-19
2000-02-22
Nguyen, Hoang
Motors: expansible chamber type
With motive fluid valve
Relatively movable serial valves
91448, 91461, 91519, F15B 1108
Patent
active
060267305
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a flow control circuit for an operating fluid in a hydraulic circuit that includes a plurality of hydraulic actuators which are supplied with a pressurized discharge fluid from a single hydraulic pump. More particularly, this invention relates to a flow control apparatus for use in such a hydraulic circuit, in which a large volumetric flow is supplied into a particular one of the hydraulic actuators and/or is flushed out of a particular one of the hydraulic actuators into a tank.
BACKGROUND ART
In order for a plurality of hydraulic actuators to be supplied with a pressurized discharge fluid from a single hydraulic pump, a discharge path of the single hydraulic pump can be provided with a plurality of operating valves in parallel to one another so that by switching over the operating valves the respective hydraulic actuators may be supplied with the pressurized fluid. If such an arrangement is adopted, however, when a plurality of the hydraulic actuators should be supplied with the pressurized fluid at the same time, it will follow that the pressurized fluid may be supplied only to an actuator whose load is small and may not be supplied to an actuator whose load is large.
Designed to resolve this problem, there has hitherto been known a pressurized fluid supply apparatus as shown in FIG. 1.
Specifically, as shown in FIG. 1, the hydraulic pump 10 will, by changing the angle of inclination of a swash plate 11, be rendered a hydraulic pump of variable displacement type in which its displacement, that is, its discharging flow per one revolution, is varied, and in which the swash plate 11 is inclined by means of a large diameter piston 12 in a displacement decreasing direction and is inclined by means of a small diameter piston 13 in a displacement increasing direction.
The above mentioned large diameter piston 12 has a pressure receiving chamber 12a which in the sense of communication is connected to and disconnected from a discharge path 10a of the hydraulic pump 10 by way of a switching valve 14, whereas the above mentioned small diameter piston 13 has a pressure receiving chamber 13a which is connected to the above mentioned discharge path 10a.
The discharge path 10a of the above mentioned hydraulic pump 10 is provided with a plurality of directional control valves 15. In each circuit 17 for connecting each of the directional control valves 15 to each hydraulic actuator 16, there is provided a pressure compensation valve 18, respectively. And they are constructed in such a manner that the said pressure compensation valve 18 may be thrusted towards a low pressure setting side under a pressure effective at a first pressure receiving portion 19 and may be thrusted towards a high pressure setting side under a pressure effective at a second pressure receiving portion 20. The first pressure receiving portion 19 is connected to an outlet side of each directional control valve 15 so as to be applied with an outlet side pressure that is effective therein, whereas the second pressure receiving portion 20 is connected to the respective circuit 17 via a shuttle valve 21 so as to be applied with the highest load pressure that is effective therein.
The above mentioned switching valve 14 is thrusted in the direction of communication under a pressure effective within the discharge path 10a and is thrusted in the direction of drain both by a spring 22 and under the above mentioned load pressure. When the discharge pressure P1 becomes higher than a force applied by the spring 22, the switching valve 14 will be shifted to apply the discharge pressure to the pressure receiving chamber 12a of the large diameter piston 12, thereby inclining the swash plate 11 in the displacement decreasing direction. When the discharge pressure P1 becomes lower than the force applied by the spring 22, the switching valve 14 will be returned to its original position to cause the the pressurized fluid in pressure receiving chamber 12a of the large diameter piston 12 to flow out into the tank side
REFERENCES:
patent: 4955283 (1990-09-01), Hidaka et al.
patent: 5333449 (1994-08-01), Takahashi et al.
patent: 5347811 (1994-09-01), Hasegawa et al.
patent: 5409038 (1995-04-01), Yoshida et al.
patent: 5579642 (1996-12-01), Wilke et al.
Honda Nobuhisa
Karakama Tadao
Yoshida Nobumi
Kananen Ronald P.
Komatsu Ltd.
Nguyen Hoang
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