HYDRAULIC POWER STEERING SYSTEM

1. Hydraulic power steering system.2. A hydraulic power steering system, at least consisting of a steering actuator (10), for the actuation of which in opposite steering directions two subsystems (12; 14) are used, each in the form of flow-regulating valve arrangements (16; 18) having release valves (V3; V6), a fault detection device (30), by means of which at least one faulty component (V1, V2; V4, V5) of a respective subsystem (12; 14) can be determined and deactivated and by means of which the fault-free components (V1, V2, V3; V4, V5, V6) of at least one subsystem (12; 14) can be caused to keep up the actuation of the steering actuator (10), is characterized in that each flow-regulating valve arrangement (16; 18) has supply valves (V1; V4) and discharge valves (V2; V5), which are assigned to each other in pairs, and designed as proportional servo valves (28), which can be actuated electrically by means of actuation signals, which, compared to each other by means of the fault detection device (30), lead to deactivation of at least one valve (V1, V2, V3; V4, V5, V6) detected as faulty in the event of deviations detected as relevant.