DREHSCHIEBERVENTIL FUER HYDRAULISCHE HILFSKRAFTLENKUNGEN

摘要

PCT No. PCT/EP87/00523 Sec. 371 Date Jan. 31, 1989 Sec. 102(e) Date Jan. 31, 1989 PCT Filed Sep. 16, 1987 PCT Pub. No. WO88/01958 PCT Pub. Date Mar. 24, 1988.An auxiliary power steering mechanism has a rotary valve that includes a rotary member integrally formed with the steering shaft of the vehicle and a fixed valve sleeve integrally formed with a threaded spindle. The rotary member contains a plurality of radial hydraulic fluid return bores arranged in two parallel rows with the bores of each row being spaced longitudinally. A guide groove in the valve sleeve, which is connected with a power cylinder, is assigned to each row of bores. An additional radial return bore is arranged in the middle of the two rows of bores and has a fixed residual cross section. All of the return bores include flat portions of different circumferential lengths to control the build-up of pressure in a surge chamber. The hydraulic return cross section produced by the bores is varied by a piston valve arranged in a concentric bore in the rotary member. The piston valve can be adjusted as a function of a pressure in accordance with speed. Operating forces at the steering wheel that are synchronized with the drive situation at the moment are obtained by changing the cross section of the row of bores in an open operating condition at that moment for setting the pressure of the rotary valve.