| 摘要 |
To supply hydraulic fluid to a hydraulic apparatus, a plurality of pumps are used. One of the pumps is used as a main pump while the remaining pump or pumps are used as sub-pumps. A flow path switching mechanism selectively disconnects the sub-pumps from a supply passage to the hydraulic apparatus. In this manner, a required minimum supply of hydraulic fluid is assured with a simple arrangement while eliminating wasteful energy loss and reducing the dissipation of the horsepower. A reliable operation is maintained without any adverse influence upon the hydraulic apparatus. In one embodiment, a pair of pumps, and a control including a pair of switching valves operating as a pressure sensor and a flow controller are assembled into a pump body. The switching valves assure a reasonable supply of hydraulic fluid to the hydraulic apparatus while minimizing the dissipation of the horsepower. At this end, a pump receiving space is defined within the pump body, and a pair of valve openings are formed around the space and close to each other so that their axes extend parallel to each other. Openings and passages are cast into the pump body or formed by a simple boring operation to provide a communication between these elements. In this manner, the overall arrangement is simple and the manufacturing and assembly are facilitated, reducing the manufacturing cost. A reduction in the size and the weight of the overall unit is achieved.
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