An automotive vehicle power steering system including a control valve mechanism having a reduced length longitudinally of the steering wheel shaft. An annular collar is fitted over the outer periphery of the rotor, over the end of the pin which connects the rotor and the torsion bar so as to permit the seal ring for providing proper oil sealability between the housing and the rotor to be arranged much closer to the pin. Another annular collar is also fitted over the outer periphery of the rotor so as to overlie the outer periphery of the thrust bearing disposed between the rotor and the housing so as to permit the seal ring for providing proper oil sealability between the rotor and the housing to be arranged much closer to the thrust bearing. Additionally, the stub shaft has a sleeve extending inwardly a distance sufficient to carry a radial bearing for maintaining the stub shaft concentric with respect to the rotor.

A power steering control valve comprises a pair of rotatable elements respectively attached to input and to output members for controlling fluid flow toward first and second actuator chambers. A disc-shaped chamber having two end walls and a circumferential wall is defined by structure attached to one of the rotatable members. The other rotatable element is a star-shaped rotor coaxial with and rotatably mounted in the disc-shaped chamber, and includes a hub from which extends a plurality of legs cooperating with the walls of the disc-shaped chamber so as to separate the latter into a plurality of pressure chambers which are circumferentially distributed. Two consecutive pressure chambers communicate respectively with the first and second actuator chambers via first and second work passages. Two consecutive legs respectively face an inlet passage opening and an outlet passage opening. In a rest position of the control valve, each leg substantially closes fluid communication from a corresponding opening to the disc-shaped chamber. The star-shaped rotor moves in response to actuator of the input member so that each leg moves past its corresponding opening to allow substantially uninhibited fluid communication between the inlet passage and one of the actuation chambers and to restrict fluid communication between the outlet passage and the other actuation chamber.

A power assisted steering mechanism comprises a steering column in two parts which are connected by a plain cylindrical torsion bar which may be solid or hollow and which allows a certain degree of relative angular displacement. An abutment is also provided to prevent excessive relative angular displacement resulting from failure of the torsion bar. The torsion bar has one of its ends bonded to one of the parts in any relative angular position and the other end is bonded to the other part as by welding, brazing or adhesive bonding, and a power assistance means are adapted device operates in response to relative movement of the parts resulting from a steering movement.

An assisted steering device for a vehicle has a steering column in two parts which are capable of limited relative angular play, permitting angular offsetting of the parts under the effect of the steering wheel. This enables two rotor discs, movable respectively with the two parts, to be offset relative to each other. These discs are located between two stators formed with annular grooves, and one of the discs has a circular series of passages which extend over a mean radius the value of which is between the values of the mean radii of two circular series of passages provided in the other disc.

A power steering mechanism includes a control valve which acts both to control the flow of pressurized fluid to and from a pair of working chambers of the mechanism and as a pressure relief valve to limit the maximum pressure which may be communicated to the working chambers. The valve includes a stack of plane annular discs which are relatively rotatable and arranged coaxially with the control shaft of the steering mechanism. The discs are resiliently biased together and define valve ports and compartments which cooperate to control the flow of pressure fluid dependent upon the relative rotational positions of the discs. Rotation of the control shaft causes rotation of one of the discs relative to the others to correlate the ports and chambers so as to supply pressure fluid to one chamber and to vent fluid from the other chamber. If the fluid pressure within the compartments of the control valve should exceed a predetermined value, the resilient bias holding the discs together is overcome and the discs separate slightly to open communication between the fluid supply ports and the vent ports. Another embodiment of the mechanism includes a linkage arranged to separate the discs and an abutment which cooperates with the linkage when the mechanism reaches either end of its range of travel. The working chambers are incapacitated when the linkage separates the discs so as to prevent damage to the mechanism from a too-high fluid pressure.