| 摘要 |
PURPOSE:To reduce a general power loss and prevent the occurrence of cavitation through a relatively simple hydraulic circuit by controlling actively an oil amount delivered from a hydraulic pump and running through a bypass passage, depending upon the temperature of a cooling system. CONSTITUTION:A hydraulic pump device 150 has a built-in hydraulic pump 15 and a built-in solenoid valve 21 for adjusting working oil. And the solenoid valve 21 has an electromagnetic changeover valve 22 and opens and closes the passage of a throttle 51. Also, a hydraulic motor 17 is connected in series to the halfway of a pipe line leading from the hydraulic pump 15 to a power steering device 16, and the rotary shaft of the hydraulic motor 17 is fitted with a cooling fan 18. Furthermore, a plurality of bypass passages 200 and 201 are provided for the hydraulic motor 17, and the passage 200 as one of said passages is provided with a plurality of electromagnetic differential pressure changeover valves 24 and 25. And ECU 33 is inputted with signals from each of sensors 34-36 for detecting the temperature of a cooling system, thereby controlling said valves 22, 24 and 25 depending upon the heat dissipation load of the cooling system.
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