Abstract: A valve arrangement includes a housing arrangement (12), (18), a first spool valve (1a, 1b) having a first spool (3a, 3b) and a second spool valve (2a, 2b) having a second spool (4a, 4b), wherein the first spool valve (1a, 1b) and the second spool valve (2a, 2b) each includes a supply channel arrangement having a pump channel (5) and a tank channel (6), and a working port arrangement having two working ports (8, 9), wherein the spools (3a, 3b; 4a, 4b) control a flow path between the supply channel arrangement (5, 6) and the working port arrangements (7, 8). In such a valve arrangement, it should be possible to simply adapt the control behaviour to different purposes. To this end, the working port arrangement (7, 8) is arranged in a flange (16a, 16b) connected to the housing arrangement (13, 14; 19, 20).

Abstract: The present application provides a full hydraulic synchronous steering system for a low-speed heavy-load vehicle, where the system includes: a steering control mechanism and a steering actuator; by determining a desired steering curve between a steering wheel angle and a rear wheel angle, when a steering error exceeds an allowable error, a controller controls the opening and closing of an oil replenishment solenoid valve (5) and an oil discharge solenoid valve (4) to adjust a flow rate of the oil flowing into a steering cylinder (7), so as to ensure that the steering error is within an allowable error range, thereby implementing synchronous steering. A method for manipulating the full hydraulic synchronous steering system is further provided. The full hydraulic synchronous steering system and the method can improve synchronous steering capability of the low-speed heavy-load vehicle and change a steering ratio, thereby improving safety and direction feeling of a driver.

Abstract: A hydraulic system for controlling a pair of steerable caster wheels includes a left side actuator and a right side actuator. A rear steering control valve is moveable between a first state for disabling direct control of the left and side actuators and a second state for enabling direct control the left and right side actuators to provide a steer response. A fluid connection continuously connects the pressure source and the fluidic tie rod fluid circuit in fluid communication when the rear steering control valve is disposed in one of the first state and the second state to continuously supply the pressurized fluid to the fluidic tie rod fluid circuit.

Abstract: A power adjustment system and a power adjustment method of an autonomous mobile device are provided. In the power adjustment method, two first current control signals respectively transmitted to two drivers are outputted by a control module. A tilt angle of the autonomous mobile device is detected by an inertial measurement module. A travel route is planned by a navigation module, and the control module obtains a steering angle of the autonomous mobile device during a traveling process. According to different weight values of the autonomous mobile device stored in a database module, a weight of the autonomous mobile device is estimated by the control module. According to the two first current control signals and the weight, the steering angle, and the tilt angle of the autonomous mobile device, two second current control signals respectively transmitted to the two drivers are outputted by the control module.

Abstract: A method for adjusting the position of a steered wheel of a vehicle includes detecting a steering position value of a steering control device of a vehicle such that the steering position value corresponds to an angular position of the steering control device; calculating a traction speed breakpoint at or above which steering desensitization may occur; and defining a maximum commencement steer angle at or below which steering desensitization may commence.

Abstract: A valve for hydraulic parallel work systems is provided. The valve includes a first pair of ports, a second pair of ports, a first connection, and a second connection. The first connection is between the first pair of ports when the valve is in a load reaction-enabling state. The first connection transmits a load reaction from a load at a steering actuator to a steering device of a hydrostatic steering circuit. The second connection is between the second pair of ports when the valve is in an electro-hydraulic steering enabling state. The second connection fluidly connects a fluid source to an electro-hydraulic steering circuit.

Abstract: A hydraulic steering arrangement (1) is described comprising a supply port arrangement (P, T) having a pressure port (P) and a tank port (T), a working port arrangement having two working ports (L, R), a main flow path (2) having a main orifice (A1), at least one further orifice (A2, A3, A4) downstream the main orifice (A1), and a measuring motor (3), the main flow path (2) being arranged between the pressure port (P) and the working port arrangement (L, R), a return flow path (4) arranged between the working port arrangement (L, R) and the tank port (T), an amplification flow path (6) having an amplification orifice (AU) and being arranged between the pressure port (P) and the working port arrangement (L, R), and an adjustable pressure source (9) connected to the pressure port (P) and having a load sensing port (18), wherein a main drain orifice (Amd) is connected between the main flow path (2) downstream the main orifice (A1) and the return flow path (4).

Abstract: A power steering system for a motorcycle, such as a motorcycle trike. The power steering system includes a piston having a piston rod disposed within a cylinder. A distal end of the piston rod is pivotably coupled to a fork tube of a motorcycle fork. A power source drives the piston rod away from the cylinder and retracts the piston rod within the cylinder. A control switch controls the piston between a neutral position, a first turn position, and a second turn position. The neutral position includes the piston rod partially extended from the cylinder. The first turn position includes the piston rod extending further from the cylinder than the neutral position. The second turn position includes the piston rod retracted further within the cylinder than the neutral position.

Abstract: An assembly includes a steering rack. The assembly includes a first pinion meshed with the steering rack. The assembly includes an internal gear coupled to the first pinion. The assembly includes a second pinion meshed with the internal gear.

Abstract: A method for adjusting the position of a steered wheel of a vehicle includes detecting a steering position value of a steering control device of a vehicle such that the steering position value corresponds to an angular position of the steering control device; calculating a traction speed breakpoint at or above which steering desensitization may occur; and defining a maximum commencement steer angle at or below which steering desensitization may commence.

Abstract: Controlling a vehicle steering system includes determining a rack position of a rack needed to execute a maneuver. A minimum velocity allowing the desired steering angle to be reached is determined. The velocity of the vehicle is increased to the determined minimum velocity. The rack is moved to the rack position needed.

Abstract: Methods and systems are provided for conducting a dual test monitor for the presence or absence of undesired evaporative emissions in a vehicle fuel system and evaporative emissions control system. In one example, the dual test monitor includes conducting an evaporative emissions test diagnostic procedure during both boosted and non-boosted conditions during a single drive cycle. In this way, results from the test diagnostic procedure conducted under boost conditions may be compared to the results of the test diagnostic procedure under non-boosted conditions, to unambiguously diagnose functionality of a plurality of components in the fuel system and evaporative emissions system, which may thus reduce undesired evaporative emissions.

Abstract: A steering arrangement including a first, second, third and fourth hydraulic chamber, the first and third chambers being operable to steer in a first direction and the second and fourth chambers being operable to steer in a second direction. A pump system supplies fluid to a steering system, which is operable to supply the pressurized fluid to one or more of the first, second, third and fourth hydraulic chambers. The steering system having a first mode wherein fluid is supplied to the first and third hydraulic chambers to steer in the first direction, or pressurized fluid is supplied to the second and fourth hydraulic chambers to steer in the second direction. The steering system having a second mode to steer in the first direction, or to steer in the second direction, such that the steering ratio is higher in the second mode than in the first mode.

Abstract: A hydraulic steering system (1) is described comprising a steering unit (3) and a pressure source (4), said steering unit (3) comprising a working port arrangement (L, R) having two working ports, a supply port arrangement having a high pressure port (P) and a low pressure port (5), a main flow path (7) having a main bleed (A1) and a metering device (8) and being arranged between said high pressure port (P) and said working port arrangement (L, R), an amplification flow path (9) having an amplification bleed (Au) and being arranged between said high pressure port (P) and said working port arrangement (L, R), said main bleed (A1) and said amplification bleed (Au) being controlled together by means of a steering handle (6) and being closed in neutral position of said steering handle, and said pressure source (4) having a variable displacement.

Abstract: A power steering assist system includes a hydraulic assist power steering assembly configured to couple to a vehicle steering gear, and a hydraulic pump having an electric motor, the hydraulic pump configured to supply pressurized hydraulic fluid to the hydraulic assist power steering assembly.

Abstract: Disclosed is a steering system which is capable of ensuring that a wheeled excavator travels straight while being driven on a paved road. The steering system for wheeled construction equipment includes: a hydraulic oil pump; a steering motor connected to the hydraulic oil pump; a steering valve controlling the operation of the steering motor; a steering handle operating the steering motor and the steering valve according to steering manipulation by the driver; and a steering cylinder steered by the manipulation of the steering handle. The steering system further includes an idle mode control unit which converts working mode into a steering mode not having straight line driving recovery performance when working mode, in which working and driving are enabled, is selected, and which converts exclusive driving mode into a steering mode having the straight line driving recovery performance through a signal input when the exclusive driving mode, in which only driving is enabled, is selected.

Abstract: The invention concerns a hydraulic steering (1) comprising a supply connection arrangement, a steering motor (2), a high pressure supply (P), and a steering unit (3) arranged between the supply connection arrangement (S) and the steering motor (2), the supply connection arrangement comprising a steering valve (9), and a valve arrangement (27). The task of the hydraulic steering is to improve the safety and faults detection over the state of the art. For this purpose, the steering valve (9) is only deflectable if the valve arrangement (27) is deflected.

Abstract: A hydraulic power steering system includes: a hydraulic cylinder in which an interior is partitioned into first and second hydraulic chambers by a piston on a steered shaft; a variable displacement electric pump that supplies hydraulic fluid to the hydraulic cylinder; a selector valve selectively set in a mode in which the hydraulic fluid is supplied to the first hydraulic chamber and drained from the second hydraulic chamber or in a mode in which the hydraulic fluid is supplied to the second hydraulic chamber and drained from the first hydraulic chamber; a detector that detects torque, steering angle, and/or vehicle speed; and a controller.

Abstract: The invention concerns a hydraulic steering (1) with a steering motor (8), a steering unit (2) with feedback behavior, a steering member activating the steering unit (2) and a shock valve arrangement (50) between the steering motor (8) and the steering unit (2). It is endeavored to enable changes of the feedback behavior in a simple manner. For this purpose it is ensured that a switchable feedback suppression device (9) is located at the side of the shock valve arrangement (50) facing away from the steering motor (8).

Abstract: The invention concerns a hydraulic steering arrangement with a hydraulically actuated steering valve arrangement, steering motor connections (CL, CR), which are connected to supply connections (HP, T) via the steering valve arrangement, and a steering unit. It is endeavored to equalize in a simple manner the steering behavior in both directions. For this purpose, it is ensured that the steering valve arrangement has a directional valve and a flow control valve.

Abstract: In a stroke-limiter equipped integral power steering apparatus, a valve body of a spring-loaded-plunger-equipped limiter valve is configured to enable a position of the valve body relative to a housing to be adjusted in a longitudinal direction of the valve body via an intermediate sleeve.

Abstract: A damping control unit sets a damping torque command value that corresponds to a steering angular velocity when a direction of a detected steering torque is a turning direction, a magnitude of the detected steering torque is larger than or equal to a first threshold, a direction of the steering angular velocity is a returning direction and a magnitude of the steering angular velocity is higher than or equal to a second threshold. An addition unit adds the damping torque command value generated by the damping control unit to a basic assist torque command value set by a basic assist torque command value setting unit.

Abstract: A hydraulic steering device is provided comprising a supply port arrangement having a pressure port (P) and a tank port (5), a working port arrangement having two working ports (L, R), a main flow path (14) between the pressure port (P) and the working port arrangement, a return flow path (16) between the working port arrangement and the tank port (5), flow meter means (15) being arranged in said main flow path (14), an amplification flow path (17) being arranged in parallel to said main flow path (14), said amplification flow path (17) being connected to said main flow path (14) downstream said flow meter means (15) in a direction from said pressure port (P) to said working port arrangement. A risk of dangerous situations in case of jamming of the flow meter should be reduced. To this end pressure increasing means are provided increasing a pressure over said flow meter means (15) in case a flow through said main flow path (14) is blocked by said flow meter (15).

Abstract: In a linear solenoid 107n, an electromagnetic coil 71n, a pressure sensor 72n, and label resistors 73n and 74n for correcting an inherent variation in a pressure detection characteristic are integrated; the standard characteristic of the pressure sensor 72n is stored in a control module 120M; when driving is started, the resistance values of the label resistors 73n and 74n are read, the pressure detection characteristic of the utilized pressure sensor 72n is corrected, and an excitation current for the electromagnetic coil 71n is controlled in such a way that a target adjusted hydraulic pressure is obtained. Even when due to a change in the oil temperature, the valve opening characteristic of the linear solenoid 107n changes, the adjusted hydraulic pressure is controlled to be constant.

Abstract: A power steering system includes an EPS and a HPS. At normal times, an assist force required by a steering system is computed based on a steering torque and a vehicle speed, and the required assist force is generated by the EPS and the HPS. The torsional stiffness of a torsion bar of the HPS is equal to or substantially equal to the torsional stiffness of a torsion bar of the EPS. Therefore, even if the EPS malfunctions, it is possible to gain the steering feel similar to that when the EPS is operating properly.

Abstract: A hydraulic power steering system includes a rotation angle sensor that detects a rotation angle of a shaft. A rotary valve includes a valve element that rotates together with the shaft of an electric motor and a housing that has an internal space connected to oil passages. A control unit reflects an output from the rotation angle sensor on control of the electric motor.

Abstract: A method is provided for performing an evaporative leak diagnostic for a vehicle. A valve in a diagnostic module is commanded to a vent position. The valve connects a fuel system to atmosphere. A pump in the diagnostic module is operated to measure a reference pressure across an orifice in the diagnostic module to provide a threshold. The valve is commanded to a test position. The pump is operated to place the fuel system in a low pressure state. A series of pressures in the fuel system is measured. A diagnostic code is provided after comparing the series of pressures to the threshold.

Abstract: A pump apparatus includes a pump housing; a drive shaft; a pump element; a cam ring arranged to vary an inherent discharge amount based on the eccentric amount of the cam ring; a steering state sensing section configured to sense or estimate a steering angle, a steering angular speed or a steering angular acceleration, and to output the steering angle, the steering angular speed or the steering angular acceleration as a steering state sensing signal; and a solenoid configured to be controlled to suppress the eccentric amount of the cam ring so as to decrease the inherent discharge amount with respect to the steering state sensing signal when the vehicle speed is equal to or greater than a first predetermined vehicle speed, relative to the inherent discharge amount when the vehicle speed is smaller than the first predetermined vehicle speed.

Abstract: A hydraulic power steering system controllable by left and right steering wheels has two control valves, each valve connected to a respective left and right steering wheel, and a valve arrangement that selectively connects one control valve to a source of high-pressure fluid and disconnects the other control valve from the source of high-pressure fluid.

Abstract: A hydraulic steering assist assembly is provided for a vehicle with a mechanical steering assembly operable by a user to steer the vehicle. The hydraulic steering assist assembly includes a hydraulic actuator adapted to be coupled to the mechanical steering assembly and has a first side and a second side. A bi-directional hydraulic pump is placed in fluid communication with the first side and the second side of the hydraulic actuator. The hydraulic steering assist assembly further includes a valve in fluid communication with the first side and the second side of the hydraulic actuator, and a control system for controlling the bi-directional hydraulic pump and the valve. The bi-directional hydraulic pump provides a pressurized fluid to the hydraulic actuator, which applies a force on the mechanical steering assembly to assist steering the vehicle. The valve can act as a steering damper.

Abstract: A method for selectively charging and discharging a steering accumulator are provided. One vehicle steering system includes a hydraulic pump configured provide a source of pressurized hydraulic fluid for use in steering the vehicle. The steering system also includes an accumulator configured to hold pressurized hydraulic fluid from the pump for use in steering the vehicle in case of need. The steering system includes a charging circuit configured to selectively allow the hydraulic fluid to flow from the hydraulic pump to the accumulator based on a fluid pressure applied by a first pilot and a second pilot. The steering system includes a charging bypass circuit configured to allow the hydraulic fluid to flow to a steering control unit and to bypass the charging circuit. The hydraulic pump supplies fluid to the charging circuit and the bypass circuit.

Abstract: There is provided a circulation line (39) for circulating pressurized oil from an accumulator (11) into a housing (15) of a steering valve (14). An orifice joint (41) is provided along the path of the circulation line (39). The orifice joint (41) is removably mounted on the housing (15) of the steering valve (14) from outside. An orifice portion (42) of the orifice joint (41) applies a throttling function to the circulating oil liquid whereby a frictional heat is generated therein. The oil liquid in a warm state flows through a communication passage (21), passages in a spool valve (16), and a low pressure side passage (18B), thus enabling the steering valve (14) to be always in a warm state.

Abstract: An apparatus (10) for use in turning steerable vehicle wheels (14, 16) includes a hydraulic power steering motor (12). A pump (26) is connected in fluid communication with the hydraulic power steering motor (12) by a supply conduit (30). A continuously variable transmission (50) is connected with the engine (52) of the vehicle and with the pump (26). The continuously variable transmission (50) is operable under the influence of force transmitted from the engine (52) to drive the pump at a first speed when the flow of fluid from the pump (26) is at a first level. The continuously variable transmission (50) drives the pump (26) at a second speed different than the first speed when the flow of fluid from the pump is at a second level different than the first level.

Abstract: A steering system includes a fluid pump and an electro-hydraulic steering circuit in selective fluid communication with the fluid pump. The electro-hydraulic steering circuit defines a first flow path having a first proportional valve and a first load-sense passage in selective communication with the first proportional valve. The first proportional valve includes a closed position. A hydrostatic steering circuit is in selective fluid communication with the fluid pump and defines a second flow path having a second proportional valve and a second load-sense passage in selective fluid communication with the second proportional valve. The second flow path is in a parallel flow configuration with the first flow path. An isolation valve is disposed in the first flow path in series with the first proportional valve. The isolation valve includes a closed position and is piloted to the closed position by fluid communicated through the second load-sense passage.

Abstract: A hydraulic steering control valve, including a valve core. When an automobile runs in a straight line or the steering angle is maintained, the valve core of the hydraulic steering control valve is positioned in a middle position to cut off hydraulic pipelines of oil cylinders on two sides of a steering power cylinder or a hydraulic shock-absorbing part, and a piston of the steering power cylinder or the hydraulic shock-absorbing part is unable to move. A self-aligning mechanism is arranged at an input shaft end of the hydraulic steering control valve, and after a driver eliminates the steering torque and loosens the control to a steering wheel, the self-aligning mechanism drives the input shaft or the steering wheel to turn to the middle position, so as to fulfill the self-aligning function.

Abstract: A steering system, in a state where a first steering means is not operated, a third signal pressure output means outputs a third signal pressure in response to a second signal pressure fed to the third signal pressure output means, and feeding and discharging control means operates based in the third signal pressure, while in a state where the first steering means is operated, the third signal pressure output means stops outputting of the third signal pressure regardless of whether or not the second signal pressure is fed to the third signal pressure output means, and the feeding and discharging control means operates based on the first signal pressure.

Abstract: A hydraulic steering system for a vehicle includes a first steering member and a second steering member, wherein the first steering member is operationally connected to a first steering valve unit including a first steering valve, and wherein a priority valve controls a flow of a hydraulic fluid to one or more steering cylinders which provide for steering of the vehicle in a desired steering direction, wherein the priority valve gives priority to steering with the first steering member over the steeling with the second steering member. A second steering valve is provided functionally operable in series with a proportional flow control valve, wherein the second steering valve and/or the proportional flow control valve are controlled at least by the second steering member.

Abstract: A hydraulic power steering apparatus assists in steering of a vehicle with a hydraulic cylinder. The hydraulic power steering apparatus includes a flow control valve, a steering torque sensor, a steering angle sensor, a vehicle speed sensor, and an ECU. The flow control valve changes the supply/drainage amount of hydraulic fluid for the hydraulic cylinder. The ECU sets a supply/drainage mode for supplying/draining the hydraulic fluid with respect to the hydraulic cylinder based on detection results from the aforementioned sensors and controls the flow control valve in accordance with the supply/drainage mode of the hydraulic fluid.

Abstract: Power steering systems and methods to improve efficiency and performance of vehicle power steering systems. In one embodiment, there is provided an engine driven positive displacement hydraulic pump, a rotary valve coupled to a steering shaft for receiving hydraulic fluid under pressure in a rotary valve inlet and providing a differential pressure to a steering rack piston for a steering boost responsive to a torque exerted on the steering shaft, valving coupled between an output of the hydraulic pump, the rotary valve inlet and the hydraulic pump input for controllably coupling the output of the hydraulic pump to the rotary valve inlet or an input of the hydraulic pump, and a controller coupled to valving to maintain a flow rate of hydraulic fluid coupled to the rotary valve responsive to a pressure sensor output. Other embodiments are disclosed.

Abstract: A system and method for selectively charging and discharging a steering accumulator are provided. One vehicle steering system includes a hydraulic pump configured provide a source of pressurized hydraulic fluid for use in steering the vehicle. The steering system also includes an accumulator configured to hold pressurized hydraulic fluid from the pump for use in steering the vehicle in case of need. The steering system includes a charging circuit configured to selectively allow the hydraulic fluid to flow from the hydraulic pump to the accumulator based on a fluid pressure applied by a first pilot and a second pilot. The steering system includes a charging bypass circuit configured to allow the hydraulic fluid to flow to a steering control unit and to bypass the charging circuit. The hydraulic pump supplies fluid to the charging circuit and the bypass circuit.

Abstract: In order to provide a solenoid valve or solenoid that allows easy and accurate wire winding for an electric annular coil employed therein, a simple shape is possessed by the electric annular coil with inner and outer cylindrical surfaces that entirely extend in parallel with an axis of the electric annular coil and a sleeve for axially sliding therein an armature together with a plunger is shaped to have a larger diameter portion that is put between a smaller diameter portion of a front core and the inner cylindrical surface of the electric coil, a smaller diameter portion that is put between the armature and a rear core integral with a solenoid housing and a sloped annular intermediate portion that extends between the larger and smaller diameter portions.

Abstract: A vehicle is provided with a fuel system, a controller, and a diagnostic module with an orifice, a pressure sensor, and a pump, the module connecting the fuel system to atmosphere. The controller measures a reference pressure across the orifice to provide a threshold, isolates the fuel system, and provides a code in response to comparing a series or measured pressures to the threshold. A method for performing an evaporative leak diagnostic is provided. A valve in a diagnostic module is commanded to a vent position. A pump is operated to measure a reference pressure across an orifice to provide a threshold. A valve is commanded to a test position. The pump is operated to place the fuel system in a low pressure state, and a series of pressures in the fuel system is measured. A diagnostic code is provided after comparing the series of pressures to the threshold.

Abstract: The invention concerns a hydraulic steering (1) with a steering unit (2) with feedback behavior, a steering motor (8) connected to the steering unit (2) via working pipes (L, R), a steering member (6) and a feedback suppression device (9), which is located in at least one working pipe (L, R). It is endeavored to change the feedback behavior of such a steering in a simple manner. For this purpose, the feedback suppression device (9) has a valve arrangement (10) with hydraulic control inlet (C).

Abstract: An apparatus for use in turning steerable vehicle wheels includes a first pump driven by an engine of the vehicle to supply fluid under pressure to a power steering motor assembly through a supply conduit. A second pump driven by the engine of the vehicle supplies fluid under pressure to the power steering motor assembly when the flow of fluid in the supply conduit is below a predetermined value. The second pump is inactive when the flow of fluid in the supply conduit is above the predetermined value. The second pump has vanes located in slits. A valve which is in fluid communication with the slits has a first condition in which fluid under pressure is supplied to the slits. The valve has a second condition in which the slits are in fluid communication with a reservoir.

Abstract: A hydraulic power steering unit has an assist force generating unit that uses oil to generate assist force for steering by a steering device, a variable flow oil pump unit that supplies oil to the assist force generating unit, and a controller that controls the oil pump unit. The controller has a command flow setting device that sets a command flow rate Qc of the oil supplied from the oil pump unit to the assist force generating unit in accordance with a vehicle quantity of state such as a vehicle speed, steering angle or the like. The controller also has a flow correcting device that corrects the command flow rate Qc in accordance with the speed of the oil pump unit.

Abstract: A power steering system for a ground vehicle includes an accumulator that supplies high-pressure fluid through a control valve to a fluid motor that drives the steerable wheels of the vehicle. A normally open control valve between the accumulator and the fluid motor closes prior to the steerable wheels reaching an axle stop to relieve power assist.

Abstract: A force steer axle assembly is disclosed for providing redundant fail-safe steering control to an axle. The assembly includes a centering cylinder for maintaining the axle in a centered position and for steering the axle as directed. The assembly further includes a hydraulic control system for providing centering and steering actuation to the cylinder, and an electrical control system for receiving user input and controlling the hydraulic system.

Abstract: An apparatus includes a hydraulic power steering motor. A continuously variable transmission has an input shaft rotatable under the influence of force transmitted from the engine and an output shaft operable to drive a pump. The continuously variable transmission is operable to drive the pump at a first speed when one of the input and output shafts of the continuously variable transmission rotates at a first speed. The continuously variable transmission is operable to drive the pump at a second speed when the one of the input and output shafts rotates at a second speed. A centrifugal sensor is connected with the one of the input and output shafts. The centrifugal sensor transfers rotational movement of the one of the input and output shafts to a linearly displaceable input member of the continuously variable transmission to change the speed at which the pump is driven.

Abstract: An electronic control unit monitors pressure conditions present at the input to the steering system and other vehicle data signals and then provides override control of a hydro-mechanical flow control device. An electro-hydraulic valve is connected to the supply side of the hydro-mechanical flow control device and reacts to the electronic monitoring of pressure and other vehicle data to alter the counter-balancing forces within the hydro-mechanical flow control device. This causes a by-pass diversion of steering fluid to the source by the hydro-mechanical flow control device and thereby relieves backpressure on the pump when relatively little steering assist is required to be provided by the steering system. The control of steering fluid diversion at such times results in a significant reduction in parasitic losses within the steering system and improves the operating and fuel efficiency of the vehicle.

Abstract: An apparatus (10) for use in turning steerable vehicle wheels (14, 16) includes a hydraulic power steering motor (12). A pump (26) having an outlet port (28) is connected in fluid communication with the power steering motor (12) and operable to supply hydraulic fluid to the power steering motor (12). A continuously variable transmission (50) is connected with the engine of the vehicle and the pump (26). The continuously variable transmission (50) is operable to drive the pump (26) at a first speed when the pressure at the outlet port (28) is at a first pressure. The continuously variable transmission (50) is operable to drive the pump (26) at a second speed when the pressure at the outlet port (28) is at a second pressure different than the first pressure. The first speed at which the pump (26) is driven is greater than the second speed.