Two-loop steering system for motor vehicles

Abstract

The steering system of a motor vehicle includes a steering motor having the application of pressurized fluid applied thereto by a main loop and in the event of a fault in the main loop by an auxiliary loop with the main loop isolated from the auxiliary loop. The motor includes a first and a second chamber. A first change over valve is fluidly connected to the first chamber of the motor while a second change over valve is fluidly connected to the second chamber. During normal operation the steering wheel is connected through a change over device to the main loop but in the event of a main loop fault, connected through said device to the auxiliary loop. Each loop includes a pump fluidly connected to a steering unit which is fluidly connected by one motor line connected to the first change over valve and a second motor line fluidly connected to the second change over valve. Each valve has a slider in one position fluidly connecting the main loop to the motor chambers and in a second position to the auxiliary loop to the motor chambers. Control circuit dependent on main loop pressure changes the change over device from connecting the steering wheel to the main loop to the auxiliary loop and to move the sliders.