Abstract: 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.

Abstract: An auxiliary power steering mechanism with a working piston installed in the steering gear has a rotary valve comprising a rotary member and a fixed valve sleeve. A piston valve is inserted in a bore provided in the rotary member. The piston valve is connected with an adjustment device, such as an electromagnet, via a tube supported by a torsion bar. The electromagnet adjusts the piston valve as a function of various influencing variables such as speed, and controls the condition of a plurality of hydraulic fluid flow return bores arranged in longitudinally spaced relation in the rotary member for noise-free control of the build-up of pressure in a surge chamber that is active at the moment. The bores have flat portions of different contours and circumferential lengths.

Abstract: A rotary valve assembly having a valve sleeve and a rotary valve core are provided with flow control grooves having control edges distributed over the peripheries for regulation of pressurized fluid. Such pressure regulation occurs at the control edges forming sets of three gaps in each rotational direction of the steering control valve. One of such gaps forms a relatively deep return flow passage that is fully opened in the neutral position of the valve assembly and two throttle gaps on opposite sides thereof that are relatively shallow for restricted return flow. Rotational displacement of the valve core initially effects pressure regulation through the intermediate deep gap within a low pressure range.