| 摘要 |
PROBLEM TO BE SOLVED: To prevent a power loss or oil temperature rise, in a travel transmission of a working vehicle connecting a steering control valve of a hydraulic steering actuator operating a steering clutch mechanism to a hydraulic pump in parallel with a switch valve of a hydraulic actuator which is different from the hydraulic steering actuator. SOLUTION: A relief circuit 151 for pressure oil supplied from the hydraulic pump P to the steering control valves 111, 112 can be switched between a relief pressure setting state and a state releasing relief pressure setting by a switching means 152. When the steering control valves 11, 112 operating the steering clutch mechanism are switched to be in a steering operation state, and when the switch valve 121 of the hydraulic actuators 23a, 26a is changed to be in an oiling state, the switching 152 switches the relief circuit 151 to a relief pressure setting state. When the steering control valves 111, 112 are switched to be in a straight ahead operating state, and when the switch valve 121 is switched to be in an oil discharging state, the switching means 152 switches the relief circuit 151 to the state releasing the relief pressure. COPYRIGHT: (C)2008,JPO&INPIT
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