PURPOSE: To enable steering at low speed large steering angles and prevent rear wheels from being steered to large steering angles in the vicinity of the neutral position by providing an operation limiting relief valve for relieving the oil pressure of a power cylinder through a steering angle reacting shutoff and variable relief pressure control valve.
CONSTITUTION: A steering angle reacting shutoff and variable relief pressure control valve 30 drives a valve body according to a steering wheel angle. When a rear wheel steering angle exceeds a specified range, an operation limiting relief valve 50 is opened to relieve the oil pressure of a rear power cylinder 22 through the steering angle reacting shutoff and variable relief pressure control valve 30. Accordingly, when the steering wheel angle is within the specified range, the steering angle reacting shutoff and variable relief pressure control valve 30 is opened, and the oil pressure of the rear power cylinder 22 is relieved by the operation limiting relief valve 50 so as to limit the rear wheel steering angle to a small steering angle. When the steering wheel angle is large, the steering angle reacting shutoff and variable relief pressure control valve 30 is closed, so that relief pressure becomes high to steer rear wheels to large steering angles.
TAKEO TAKESHI
SUZUKI HIDEKAZU
TANAKA TADAO
