| 摘要 |
A closed hydraulic system (22) is provided for transmitting steering movement to a rear wheel steering assembly (16) in response to steering movement of a front wheel steering assembly (14). The front wheel steering assembly is controlled by a steering wheel (18) and a power steering assembly (20). The closed hydraulic system (22) includes a pump assembly (56) and an actuator assembly (58) connected together by conduits (60,62) to define closed fluid flow branches (164,166) for moving a piston (112) in the actuator assembly in response to movement of a piston (78) in the pump assembly. Movement of the actuator piston is transmitted to the rear wheel steering assembly via first and second cam assemblies (122,124) which effect same direction rear wheel steering for rather small front wheel steering angles and which effect opposite direction rear wheel steering for greater front wheel steering angles. Pump assembly (56) includes first and second neutral valves (92,94) for intercommunicating opposite sides of the pump piston (78) with a chamber ( 83) when the piston is in a neutral position. System (22) also includes a reservoir (68) disposed above the normal fluid level of the system and exposed to atmospheric pressure.
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