Hydraulic steering system for commercial vehicles

摘要

The steering system comprises the conventional components in and in addition a secondary electric motor driven pump with its own battery which is brought into operation only if the main pump fails by means of an electronic control unit. The conventional hydraulic steering system consists of a pump (200) feeding hydraulic fluid from a reservoir (204) to a back-pressure valve (210), a priority steering control unit (208), the steering valve unit (216) and the steering control vale unit (220). A safety hydraulic supply, in the event of failure, is provided by an auxiliary pump (256), the motor of which (250) is energised by a battery (254) controlled by an electronic unit (274) and relay (252), and a valve (260). A compression spring (268) holds the valve normally connected to the fluid reservoir. If the engine is in operation, detected by a sensor (278) and the pressure in the main circuit is low, detected by pressure sensor (276) the electronic control unit switches on the auxiliary pump to feed the steering unit.