Abstract: In a steering system for a motor vehicle, the steered vehicle wheels, during normal operation, are coupled with a steering handle only through an electronic regulating system that constantly checks for correct function. The regulating system controls an actuator for the steering adjustment of the steered vehicle wheels in response to a signal from a set value transmitter which is actuated by the steering handle. During abnormal operation, a mechanical or hydraulic forced coupling is introduced between the steering handle and the steered vehicle wheels. At the same time the actuator and/or a manual force adjuster associated with the steering handle operate as a servo motor.

Abstract: A steering system of a non-tracked motor vehicle whose steered vehicle wheels are connected in the normal operation with respect to the effect with a steering handle only by way of an electronic automatic control unit which continuously monitors itself with respect to a correct operation. As a function of a desired-value generator, which is operated by the steering handle, and an actual-value generator operated by the vehicle wheels, this automatic control system operates an adjusting drive for the steering adjustment of the steered vehicle wheels. In the event of a malfunctioning of the automatic control system, a forced coupling is automatically switched effective between the steering handle and the steered vehicle wheels. When the forced coupling is switched on, the steering system operates as much as possible in the manner of a conventional power steering system.

Abstract: A switching valve (50) for a hydraulic power steering system (10) includes a longitudinally movable valve spool (80). A spring (86) biases the spool (80) to a neutral position. The switching valve (50) is configured to direct hydraulic fluid from a primary pump (34) to a steering control valve (14) when the spool (80) is in a primary position, and to direct hydraulic fluid from an auxiliary pump (38) to the control valve (14) when the spool (80) is in an auxiliary position. The spool (80) is movable against a bias of the spring (86) from the neutral position to the primary position under the influence of a hydraulic fluid pressure differential between the opposite ends of the spool (80). The switching valve (50) defines a flow path for directing hydraulic fluid from the primary pump (34) to an end of the spool (80) when the spool (80) is in the neutral position. The flow path extends axially over a flat portion (124) of an outer surface of the spool (80).

Abstract: A vehicle steering system is provided with a manually operable steering member and a hydraulically operated steering actuator unit operable to control the steering movements of at least one vehicle wheel in response to movement of the steering member. Steering forces are transmitted between the steering member and actuator unit by a pair of selectively engageable independent hydraulic circuits. A safety valve arrangement is operable to switch operation between the two circuits.

Abstract: In a hydraulically operated steering for a motor vehicle comprising a control motor with first and second double acting piston and cylinder units arranged in axial alignment and a single piston rod extending through the first and second double acting piston and cylinder units, at least one of the double acting piston and cylinder units includes an annular piston which is fastened on the pistons rod in a predetermined axial position and an annular divider wall is disposed between the pistons for slidably supporting the piston rod and separating the cylinders of said first and second double acting piston and cylinder units fluidically from one another so as to form cylinder chambers for said pistons limited at one side by an annular divider wall and by guide sleeve members disposed in the opposite ends of the cylinder units.

Abstract: A hydraulic power steering system is provided in which a manual steering device and the steering vehicle wheels are normally coupled only by way of a control path with a desired-value generator operated by the manual steering device and an actual-value generator operated by the steering vehicle wheels. For controlling a hydraulic servomotor used for the steering operation of the steering vehicle wheels, a servo valve arrangement is operated by a desired-value/actual-value comparison. Only when there is a disturbance in the control path, will a hydraulic forced coupling take place between the manual steering device and the steering vehicle wheels.

Abstract: The invention changes over to another steering ratio automatically and very safely on the transition from servo to emergency operation. In the steering system, only a few of the lines (13) link the metering pump (10) to one of the cylinder connections (7, 8) and in each of the other lines (13') there is a changeover unit (16) which also links the lines (13) to the cylinder connections (7, 8) or the delivery connection (6) depending on the method of operation. These steering systems are used in mobile systems, especially slow-moving vehicles.

Abstract: The inventive steering system is of the type having an engine, a fluid reservoir, a steering valve unit, an actuator control valve unit, a main fluid pump driven by the engine for pumping the fluid in the reservoir to feed pressure fluid to the steering valve unit and the actuator control valve unit and a priority valve for enabling the pressure fluid to be first supplied to the steering valve unit. Characteristically, the steering system includes an electric motor, a battery selectively connected to the electric motor for supplying electric current to the electric motor, an auxiliary fluid pump rotatingly driven by the electric motor to produce emergency steering fluid to be fed to the steering valve unit and a power supply controller for disconnecting the electric motor from the battery while the main pump produces the pressure fluid and for connecting the electric motor to the battery when no pressure fluid is discharged from the main pump.