Electrohydraulic steering system for automobile has emergency hydromechanical steering circuit for back-up of steer-by-wire steering circuit utilising same switching valve

摘要

The electrohydraulic steering system (10) has a primary steer-by-wire steering circuit (54) and an emergency hydromechanical steering circuit (55), with an electromagnetically-operated switching valve (21) inserted in both steering circuits. The valve is normally operated via an electronic control in dependence on the detected rotation of the steering wheel (11), which is coupled to the hydromechanical steering circuit for mechanical operation of the valve via a mechanical control input (49).