| 摘要 |
PURPOSE:To achieve safety steering, by constructing a power steering device such that a gate valve arranged in the way of an oil bypath detouring a power multiply regulation valve is opened upon missing of hydraulic pressure of a vehicle speed pump which increases delivery as the vehicle speed increases thereby requiring heavy steering force regardless of the vehicle speed. CONSTITUTION:A vehicle speed responsive hydraulic power steering device comprises an oil supply path 24 continuous to a working oil pressure source 20, an oil discharge path 24 continuous to a tank 23 and a changeover valve 12 interlocked with a steering shaft 10 to switch between a pair of hydraulic chambers 4, 5 of a power cylinder 2 selectively. The changeover valve 12 is energized toward the neutral position by the pressure of a hydraulic reaction chamber 26. A power multiply regulation valve 30 being energized in the open valve direction by delivery pressure of a vehicle speed pump 38 which increases as the vehicle speed increases is arranged in the way of an oil path 31 communicating between the hydraulic reaction chamber 26 and the oil supply path 21. Here, the opposite ends of an oil bypath 49 detouring the power multiply regulation valve 30 is coupled to the communication oil path 31, and a gate valve 50 openable through a spring 55 upon fault of the vehicle speed pump 38 is arranged in the way of said oil path 49.
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