Patent ID: 8672084

Claim:
A rear wheel steering system that is applicable to a four-wheel steering vehicle of which front wheels and rear wheels are both able to be steered, comprising: a coupling arm that is provided between and connected to a pair of the rear wheels, and that slides in a vehicle-width direction to steer the pair of the rear wheels; a recess that is formed in the coupling arm; a pin member that is able to be fitted into the recess from an outer side of the coupling arm, that is provided at a position at which the pin member faces the recess when the coupling arm is in a neutral position in which the coupling arm does not slide in the vehicle-width direction, that is fitted into the recess to lock sliding of the coupling arm when the pin member is placed in an advanced state, and that is disengaged from the recess to cancel slide lock on the coupling arm when the pin member is placed in a retracted state; and advance/retraction control means for placing the pin member in the retracted state when a vehicle speed is lower than or equal to a predetermined speed and for placing the pin member in the advanced state when the vehicle speed is higher than the predetermined speed, wherein the coupling arm has guide grooves that are formed on respective sides of the recess in a longitudinal direction of the coupling arm so as to be contiguous with the recess, and that are used to guide the pin member in the advanced state toward the recess; and the guide grooves each gradually deepen in a stepwise manner toward the recess.