Fluid handling – Systems – Supply and exhaust
Patent
1999-08-11
2000-10-24
Michalsky, Gerald A.
Fluid handling
Systems
Supply and exhaust
60452, 91446, 137596, F15B 1308, F15B 1105
Patent
active
061351490
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a pressure compensating valve used for a hydraulic circuit distributing and supplying a hydraulic fluid delivered from one hydraulic pump to a plurality of actuators.
BACKGROUND ART
When a hydraulic fluid delivered from one hydraulic pump is supplied to a plurality of actuators, the hydraulic fluid is supplied only to the actuator having a lower load pressure and thus as a proposal for dissolving the problem, there has been known a hydraulic circuit disclosed in JP, A 60-11706, for example. This hydraulic circuit is shown in FIG. 6.
In FIG. 6, a delivery line 102 of a hydraulic pump 101 is connected to actuators 106, 116 via a valve unit 150. The valve unit 150 comprises pressure compensating valves 103, 113, hold check valves 104a, 114a, directional control valves 105, 115, and a shuttle valve 107. The pressure compensating valves 103, 113 are connected in parallel to the delivery line 102, and the directional control valves 105, 115 are respectively connected to outlet lines 104, 114 of the pressure compensating valves 103, 113 through the hold check valves 104a, 114a and outlet sides of the respective directional control valves 105, 115 are respectively connected to the actuators 106, 116. The pressure compensating valves 103, 113 are configured to be urged in their opening directions by a delivery pressure of the hydraulic pump 101 and outlet pressures of the directional control valves 105, 115 and to be urged in their closing directions by inlet pressures of the directional control valves 105, 115 and the highest load pressure. The shuttle valve 107 compares the load pressures of the actuators 106, 116 to select the higher one thereof to supply the same to the pressure compensating valves 103, 113 and a load sensing valve 120. With such a circuit structure, when the plurality of the directional control valves 103, 113 are operated simultaneously, a hydraulic fluid delivered from the hydraulic pump 101 is supplied to the respective actuators 106, 116 at a predetermined distribution ratio by the function of the pressure compensating valves 103, 113.
DISCLOSURE OF THE INVENTION
As mentioned above, the hold check valves 104a, 114a are essential for the valve unit 150 for driving the actuators 106, 116. The hold check valves 104a, 114a are provided for preventing reverse flows of the pressure fluids from the actuators to hold the position thereof when the delivery pressure of the hydraulic pump 101 is lower than the load pressure in a case where the directional control valves 105, 115 are being operated, for example, at a starting time of the actuators or at a time when the loads acting on the actuators have been increased. For this reason, in the valve unit 150, a space is required for providing the hold check valves 104a, 114a in the outlet lines 104, 114 of the pressure compensating valves 103, 113.
Also, in the valve unit 150 provided with the pressure compensating valves 103, 113 shown in FIG. 6, it is necessary to provide the shuttle valve 107 for comparing the load pressures of the actuators to supply the higher one to the pressure compensating valves. Thus, in the valve unit 150, a space is also required for providing the shuttle valve 107 in signal fluid lines 108, 118.
Consequently, the entire valve unit 150 including the pressure compensating valves 103, 113 and the directional control valves 105, 115 is large-sized and the structure of the valve 150 becomes complicated, thereby increasing the manufacturing cost.
Also, in the hydraulic circuit shown in FIG. 6, assuming that, when the two actuators 106, 112 are operated together, the load pressure of the actuator 106 is larger than that of the actuator 112, the pressure in the line 108 in the valve 150 is introduced to a line 109 via the shuttle valve 107 as the highest pressure. Further, assuming that the load pressure of the actuator 116 becomes larger than that of the actuator 106 due to variation of the load pressures, when the shuttle valve 107 is switched, ventilation occurs from the s
Aoki Minoru
Ichiki Nobuhiko
Nishimura Yoshizumi
Nozawa Yusaku
Takahashi Kinya
Hitachi Construction Machinery Co. Ltd.
Michalsky Gerald A.
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