A vehicle steering for turning the steerable wheels of a vehicle having a fluid motor with a housing defining a fluid chamber and a piston in the chamber dividing the chamber into first and second chamber portions. A rotatable steering input member is supported by the housing. A rotatable follow-up member is associated with the piston and rotatable upon movement of the piston in the chamber. A valve controls pressurized fluid flow to the first and second chamber portions. The valve comprises first and second relatively movable valve parts. One of the valve parts is connected with the input member and the other of the valve parts is connected with the follow-up member forming a unit therewith. The unit has a surface against which fluid pressure in the first and second chamber portions acts tending to create an axial force on the unit. Pressure is applied to another surface area of the unit to balance the axial force acting on the unit.
A power steering system includes a pair of valve members (42, 46) which are interconnected by a torsion-tension spring (52). During a steering maneuver, torque is applied to the torsion-tension spring (52) to effect increasing torsional deformation of the torsion-tension spring. Tensile force is also applied to the torsion-tension spring (52) to effect increasing axial deformation of the torsion-tension spring. The tensile force is applied to the torsion-tension spring (52) by interaction between rollers (110) of a thrust bearing (80) and annular arrays (84, 92) of cam surfaces (86, 94) which engage opposite sides of the rollers. The cam surfaces (86, 94) are connected with opposite ends of the torsion-tension spring (52) by rigid bodies(42, 62, 102, 76) so that any increase in the distance between the cam surfaces results in a corresponding elongation of the torsion-tension spring. The cam surfaces (86, 94) have a configuration such that the extent of axial deformation of the torsion-tension spring (52) during each increment of relative rotation decreases. This results in a decrease in the force required to effect each succeeding increment of axial deformation of the torsion-tension spring (52).
A power steering motor is operatively connectable with steerable vehicle wheels for steering the vehicle wheels. An actuatable power steering valve has a neutral position in which fluid flows through the steering valve to a fluid reservoir and an actuated position in which fluid flows through the steering valve to the steering motor. A main conduit conducts fluid from the outlet port of a pump to the steering valve. A return conduit conducts fluid from the steering valve to the reservoir when the steering valve is in its neutral position and in its actuated position. An orifice is located in the return conduit. A bypass valve bypasses fluid from the main conduit to the reservoir. The bypass valve is controlled in response to a pressure drop across the orifice located in the return conduit.
A power steering assembly (10) includes a rotatable valve core (40) which is encircled by a rotatable valve sleeve (41). The valve core (40) and valve sleeve (41) have surfaces which cooperate to direct a flow of power steering fluid during relative rotation between the valve core (40) and valve sleeve (41). A bearing assembly (100) is disposed between the valve core (40) and the valve sleeve (41) at a location adjacent to an axially outer end portion of the valve core (40). The bearing assembly (100) includes a plurality of rotatable bearing elements (124) which transmit sidewise loads between the valve core (40) and the valve sleeve (41). A bearing surface (102) is disposed on an axially inner end portion of the valve core (40). The bearing surface (102) is slidable along an inner surface area (104) on the valve sleeve (41) to transmit a sidewise load during relative rotation between the valve core (40) and the valve sleeve (41).
An apparatus (10) for use in turning steerable vehicle wheels (14, 16) includes a hydraulic power steering motor (12). A pump (26) is operable to supply hydraulic fluid to the power steering motor (12). A gearset (50) is connected with the engine of the vehicle and the pump (26). The gearset (50) is operable to drive the pump at a first speed during turning of the steerable vehicle wheels (14, 16) at relatively low vehicle speeds. The gearset (50) is operable drive the pump at a second speed during turning of the steerable vehicle wheels at relatively high vehicle speeds. The second speed which is less than the first speed. The gearset is a differential gear mechanism.
A hydraulic power steering apparatus (10) comprises a rotatable input member (31), a rotatable output member (130), and a housing supporting (11) the input member (31) and the output member (130) for rotation about an axis (45) relative to each other. A hydraulic control valve assembly (30) in the housing (11) includes a valve core (40), a valve sleeve (41) and a plurality of hydraulic seals (120-126) which block leakage of hydraulic fluid from the valve assembly (30). The hydraulic power steering apparatus (10) further includes an elastomeric damping ring (200) extending circumferentially between the valve core (40) and the valve sleeve (41). The elastomeric damping ring (200) damps vibrations of the valve core (40) relative to the valve sleeve (41), and thereby attenuates noise in the apparatus (10).
