Abstract: 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.

Abstract: An apparatus provides hydraulic fluid for power steering assistance for steering a vehicle. A valve controls flow of hydraulic fluid from a first, engine driven, pump and a second, wheel driven, pump. The valve includes a valve housing and a valve member. The valve member is movable relative to the valve housing in response to a pressure differential in the hydraulic fluid from the first pump. The valve member in one range of relative positions provides a first flow passage from the first pump toward a steering valve, provides a variable second flow passage from the first pump toward the steering valve, and blocks hydraulic fluid flow from the second pump toward the steering valve. The first and second flow passages are in fluid parallel. The valve member in a control position provide a third flow passage from the second pump to the steering valve.

Abstract: A method and apparatus are disclosed for controlling a vehicle steering system of the type having front steerable wheels and rear steerable wheels. The present invention permits the vehicle operator to select front wheel only steering, crab steering, or curl steering. If the vehicle speed is above a predetermined value, steering control is automatically switched to front wheel only steering, and the rear steerable wheels are locked in the straight-ahead direction. The lock mechanism is not actuatable until the rear steerable wheels are sensed to be within a predetermined angle of a straight-ahead direction. If the vehicle operator switches from one steering mode to another steering mode, the rear steerable wheels must return to a near straight-ahead direction before the mode will be switched.

Abstract: 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.

Abstract: A multiple speed fluid motor includes a housing having an inlet port for receiving high pressure fluid and an exhaust port for exhausting low pressure fluid, and a gerotor gear set. An output shaft is supported for rotation relative to the housing. One of the gerotor gears is coupled with the output shaft for rotating the output shaft in response to fluid being supplied to the inlet port. The motor includes fluid passages for conducting fluid to the fluid displacement means. A control valve member is movable to control fluid flow through the fluid passages to control the rotational speed of the output shaft. The control valve member is mounted in a valve chamber defined by a plurality of plates.

Abstract: A method and apparatus for controlling a vehicle steering system of the type having front steerable wheels and rear steerable wheels. The present invention permits the vehicle operator to select front wheel only steering, crab steering, or curl steering. If the vehicle speed is above a predetermined value, steering control is automatically switched to front wheel only steering, and the rear steerable wheels are locked in the straight-ahead direction. The lock mechanism is not actuatable until the rear steerable wheels are sensed to be within a predetermined angle of a straight-ahead direction. If the vehicle operator switches from one steering mode to another steering mode, the rear steerable wheels must return to a near straight-ahead direction before the mode will be switched.

Abstract: A vehicle steering system having more than one set of steerable wheels includes a hydrostatic steering unit connected in fluid communication with actuatable hydraulic steering motors operatively coupled with one set of wheels. The hydraulic steering motors are actuated when hydraulic fluid is applied thereto. Steering movement of the one set of wheels is effected in response to actuation of the hydraulic steering motors. The hydrostatic steering unit has an input shaft drivingly connected with an output shaft of an electric motor. The speed and direction of rotation of the output shaft of the electric motor, and hence the speed and direction of rotation of the input shaft of the hydrostatic steering unit, is controlled in response to a control output signal from a microcomputer. The control output signal from the microcomputer is generated in response to the magnitude and direction of steering torque applied to the steering wheel, the vehicle speed, and the positions of the sets of steerable wheels.

Abstract: A power steering system includes a bypass valve for bypassing fluid from a main fluid conduit connected between an engine-driven, power steering pump and an actuatable, open-center, steering control valve which is actuated upon turning of a vehicle steering wheel. When the steering control valve is actuated, the demand for fluid through the steering control valve to a power steering motor increases. The fluid pressure in the main conduit varies as a function of the demand for fluid to the steering control valve. The bypass valve is urged toward an open condition by a fluid pressure signal. The bypass valve is urged toward a closed condition by a spring and by a fluid pressure which varies as a function of the demand for fluid to the steering control valve and as a function of an electrical signal which varies as a function of at least one vehicle operating parameter, such as vehicle speed.

Abstract: A power steering system includes a bypass valve assembly which bypasses fluid from a main conduit connected with a power steering pump and motor. The bypass valve assembly is urged toward an open condition, bypassing fluid from the main conduit, with a force which varies as a function of the fluid pressure drop across an orifice in the main conduit. The bypass valve assembly is urged toward a closed condition by a spring. In addition a pressure responsive pilot valve assembly opens to communicate the fluid pressure in the main conduit to the bypass valve to urge the bypass valve assembly toward the closed condition. This decreases the rate at which fluid from the power steering pump is bypassed to thereby increase the amount of fluid available for actuation of the power steering motor.

Abstract: A power steering system includes a hydraulic pump and a hydraulic steering mechanism. A flow control orifice passes fluid from the pump to the steering mechanism and generates a hydraulic control signal proportional to the fluid flow rate therethrough. A flow control valve is connected between the pump to bypass fluid away from the steering mechanism in response to the hydraulic control signal. A solenoid operated valve is located in a pilot fluid circuit between the pump and the flow control orifice to vary the hydraulic control signal in response to an electrical control signal. The electrical control signal is a pulse width modulated signal having a duty cycle proportional to vehicle speed. Maximum power assist occurs when vehicle speed is below a predetermined value and decreases with increasing vehicle speed above the predetermined value.

Abstract: A hydraulic motor which varies its displacement in accordance with varying torque loads on its output shaft. The motor is biased to a low displacement, low torque, high speed mode, and changes to a high displacement, high torque, low speed mode when the torque load on its output shaft increases. The motor has eccentrically disposed gerotor gears that rotate and orbit relative to each other to expand and contract fluid chambers on opposite sides of a center line of eccentricity. The gerotor gears can change their orientation relative to each other in response to changes in the torque load on the output shaft, changed, in order to change the displacement of the motor.

Abstract: A hydraulic device with fluid pockets formed by a gerotor gear set, including a rotatable and orbital rotor, has a special commutation valve structure for valving fluid flow to and from the fluid pockets in timed relation to the movement of the rotor. The gear set is disposed between a pair of housing members. One end face of the rotor and the face of the adjacent housing member cooperate to define separate pressure areas which are continuously communicated with high and low fluid pressures, respectively. The other end face of the rotor has a circular array of openings which number twice the number of teeth of the rotor. A series of passages extending through the rotor communicate all of the openings of the circular array with the separate pressure areas, alternate openings being communicated with areas at different pressures. The face of the housing member adjacent the other end face of the rotor has radially extending, generally T-shaped recesses facing the fluid pockets.

Abstract: A controller for controlling fluid flow from a source to a motor, such as the steering motor of a motor vehicle. The controller includes a metering section and a control valve section comprising a stacked assembly of plate valve members which control flow and, along with the metering section, define the outer periphery of the controller, and minimize the need for complex cast housing members. The controller is compact and yet is constructed to respond to an input signal from an input shaft to direct needed flow from the source to the primary steering motor, and excess flow to an auxiliary motor. The controller is also characterized by a unique spring centering mechanism which applies a spring centering force to the assembly of plate valve members. Additionally, the controller is characterized by a special seal arrangement for resisting leakage of high pressure fluid about the input shaft, and by structure for forming pressure dams to resisting leakage of metered fluid.

Abstract: An assembly of plate members for forming a commutator valve for hydraulic devices of the expanding-contracting pocket type, such as hydraulic motors. The assembly includes a first end plate, a second end plate and a plurality of intermediate plates therebetween. The first end plate includes first and second arrays of fluid passageways for communicating with expanding and contracting fluid pockets, respectively, during operation of the motor. The intermediate plates may be assembled together in either a first or a second alignment depending upon the desired direction of rotation of the hydraulic motor. The intermediate plates are designed such that in the first alignment they direct high pressure fluid from a high pressure port to the first array of passageways and low pressure fluid from the second array of passageways to a low pressure port. The output shaft of the hydraulic motor thus rotates in one direction.

Abstract: An improved controller assembly is utilized in a hydrostatic steering system having an engine driven pump with a servomotor which is effective to vary the displacement of the pump upon operation of a pressure responsive valve assembly. The controller assembly includes a housing having a valve chamber with an inlet port which receives fluid from the pump. Upon rotation of a steering wheel, a controller valve member is moved to an actuated position and a metered flow of fluid is conducted from the valve chamber through a motor port to a steering motor. In addition, fluid is conducted from the steering motor through another motor port to the controller valve chamber. The fluid from the steering motor is then discharged from the valve chamber to reservoir or drain through an outlet port. The controller assembly also includes a control port connected in fluid communication with the pressure-responsive valve assembly.