| 摘要 |
PURPOSE:To aim at lowering the consumption power and the load of an engine by providing a bypass passage having a line pressure adjusting section, in parallel to a relief valve for setting a normal line pressure, so that the line pressure is lowered when the vehicle speed is below a set value. CONSTITUTION:A hydraulic pump 1 coupled to a power output shaft 2a of an engine 2, is connected at its discharge side to a hydraulic pressure pipe line 5 which is connected with a plurality of pressure control valves 12a through 12d corresponding to a plurality of wheels through a pressure holding section 11. Further, the pressure control valves 12a through 12d are connected to an oil tank 3 through the intermediary of a drain pipe line 13. In this arrangement, a bypass passage 21 having a line pressure adjusting part 22 is arranged in parallel with a relief valve 15 for setting a normal line pressure for the pressure holding section 11. The line pressure adjusting part 22 is composed of a solenoid shut-off valve 24 controlled by a line pressure control device 23 and a relief valve 25 having a pressure set to a value lower than the set pressure of the above-mentioned relief valve 15, which are connected together in series.
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