FOUR-WHEEL STEERING DEVICE

PURPOSE:To enable checking an electric drive source for a control valve, a bypass valve, a valve displacement sensor by keeping the bypass valve open, and driving the electric drive source, when an engine signal is turned on and a vehicle speed signal indicates a zero-speed. CONSTITUTION:A controller 6 operates the stepping motor 13 of a control valve 10 over the whole range of the operation stroke thereof, while a by-pass valve 15 being kept open and both chambers 3a and 3b of a rear wheel steering power cylinder 3 being made continuous to each other, when an engine signal from an engine start sensor 26 is turned on and a vehicle speed signal from a vehicle speed sensor 19 indicates a zero-speed. In this state, valve displacement is detected with a valve displacement detection sensor 14, thereby performing the self-check of a motor 13, a by-pass valve 15 and a sensor 14. At the same time, the output of a rear wheel steering angle sensor 20 is detected. Upon finding any failure, the bypass valve 15 is kept open, rear wheels 5 are turned into a non-steering state and only front wheels 3 are kept in two-wheel steering state.