Power-assisted steering for motor vehicles

Abstract

In a servo steering unit which is designed particularly for motor vehicles, a pinion in a steering housing meshes with a steering rack. A steering valve which serves to control the pressure medium for the servo steering unit has two inlet seat valves (10, 11) and two outlet seat valves (12, 13) whose closing members (14, 18) are displaced by actuating tappets (16, 17) depending on the rotation of a steering spindle. The outlet seat valves (12, 13) are open in the neutral position of the steering valve. The inlet seat valves (10, 11) can be actuated by the force of pressure springs (15) in the closing direction and are not opened until after closing of the associated outlet seat valve (12, 13). The pressure springs of both inlet seat valves (10, 11) on one side press against the actuating tappets (16, 17) and on the other side press constantly on the closing member (14). The pressure springs (15) are designed so that they exert a closing force on the closing members (14) in the neutral position of the steering valve and so that during displacement of the steering valve away from its neutral position, one of the pressure springs (15) rests without applying force on the closing member (14) as soon as the associated outlet seat valve (12, 13) is closed. This provides a servo steering system which, to a large extent, operates irrespective of production tolerances with a desired and constant power take-off.

Dependencies are inferred from the claim text.