Hydraulic control unit for double acting working cylinder esp. in vehicle steering unit - controls both working volumes by one 4/3-way valve with hydraulic shut off valve connected between each working vol. and 4/3-way valve

摘要

A braking unit (23) is provided for the working cylinder (11), which is activated by a spring. A control valve (44) is connected in the supply line between the 4/3 valve (12) and the pressure medium source (43). A pilot valve (54) is provided which has a spring loaded central position. The pilot valve in its test position (66) has a choked transverse connection (67) between its connections assigned to the pressure medium source and the tank (29). A pressure sensor (68) is connected in the supply line (42) upstream of the pilot valve, which works in conjunction with the electronic control unit (22). ADVANTAGE - Gives high functional safety, ensures reliable arresting of piston rod. Monitoring of pilot valve is carried out in simple and cost effective way.