Power plants – Pressure fluid source and motor – Having condition responsive control in a system of distinct...
Patent
1995-01-20
1996-10-01
Lopez, F. Daniel
Power plants
Pressure fluid source and motor
Having condition responsive control in a system of distinct...
60494, 91515, 91532, 180 648, F16D 3102
Patent
active
055602045
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a compensation system for a hydraulic circuit supplying pressurized fluid for left and right traveling hydraulic motors of a hydraulically driven vehicle in order to effect compensation for straight traveling.
BACKGROUND ART
In the prior art, there are various hydraulic circuits for hydraulically driven vehicles that have been employed mainly for constructional vehicles, work implements and so forth. FIG. 1 shows one example of such a hydraulic circuit for a hydraulically driven vehicle. The shown hydraulic circuit is constructed by connecting discharge output passage 2 of a hydraulic pump 1 to inlet ports 5a and 6a of left and right traveling valves 5 and 6 via left and right pressure compensation valves 3 and 4, connecting outlets of respective left and right traveling valves 5 and 6 to left and right traveling hydraulic motors 7 and 8 and connecting the inlets of the left and right traveling valves 5 and 6 through a by-pass passage 9.
With such a hydraulic circuit, compensation for straight traveling can be done by establishing communication between the inlets of the left and right traveling valves 5 and 6. However, when opening area is differentiated due to tolerance in machining of cut-outs of metering portions of the left and right traveling valves 5 and 6, fluid amounts to be supplied to the respective left and right traveling hydraulic motors 7 and 8 may be differentiated so that precision in compensation for straight traveling can be degraded.
The problem may be solved by connecting a left side fluid line 10 connected to the left side traveling valve 5 and the left side traveling hydraulic motor 7 to a right side fluid line 11 connected to the right side traveling valve 6 and the right side traveling hydraulic motor 8. However, in such construction, since there are respectively two left side fluid lines 10 and right side fluid lines 11, two by-pass passages become necessary, which are disadvantageous in viewpoint of cost and space.
CONSTRUCTION OF THE INVENTION
Therefore, it is an object of the present invention to provide a compensation system for a hydraulic circuit of a hydraulically driven vehicle for straight traveling, which can solve the above-mentioned problem.
More specifically, it is an object of the present invention to provide a compensation system for a hydraulic circuit of a hydraulically driven vehicle for straight traveling, which can equalize hydraulic supply pressure for hydraulic motors for driving to travel without requiring a plurality of by-pass passages.
In order to accomplish the above-mentioned and other objects, according to the first aspect of the present invention, a compensation system for a hydraulic circuit of a hydraulically driven vehicle for straight traveling, comprises:
left and right traveling valves connected to a pressurized fluid source at the inlet side via left side and right side pressurized fluid supply passages, connected to left and right hydraulic traveling motors at the outlet sides and having load detection ports;
left and right pressure compensation valves arranged in respective pressurized fluid supply passages between the fluid pressure source and the traveling valves and having check valve portions for establishing and blocking communication between the fluid pressure source and the left and right traveling valves, and a pressure reduction valve portion for lowering supply pressure supplied from the fluid pressure source, the check valve portion being constructed to be applied an inlet pressure in a communication establishing direction and output pressure in a communication blocking direction, the pressure reduction valve portion being contacted with the check valve portion by a spring, the pressure of one of pressure chambers being applied for establishing communication between the inlet side and the outlet side and to shift the pressure reduction valve portion in a direction away from the check valve portion, and apply the pressure of the other pressure chamber being applied for bl
REFERENCES:
patent: 4769991 (1988-09-01), Johnson
patent: 5063739 (1991-11-01), Bianchetti et al.
patent: 5138837 (1992-08-01), Obertrifter et al.
Ikei Kazunori
Ishihama Kazuyoshi
Kabushiki Kaisha Komatsu Seisakusho
Kananen Ronald P.
Lopez F. Daniel
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