A steering assist system for a hybrid vehicle capable of being driven by both of an engine and a drive motor, including a first assist portion and a second assist portion configured to assist a steering force respectively utilizing the engine and an electric motor each as a drive source, wherein the steering force is assisted only by the second assist portion in a motor-driven state in which the vehicle is driven only by the drive motor, and wherein the steering assist system is configured to, upon occurrence of a failure of the second assist portion in the motor-driven state, drive the engine, execute assist switching from an assist by the second assist portion to an assist by the first assist portion, and gradually increase, in the assist switching, an assist force by the first assist portion up to a set assist force when the vehicle is being steered.

A vehicle steering assist system, including an engine pump, a flow-rate restricting mechanism, a motor pump, a motor-pump controller, and a steering-force assist device, wherein the steering assist system is configured to restrict an engine-pump ejection flow rate to be lower than a required receiving flow rate to be received by the assist device when the engine pump is operated by being driven by an engine rotating at an idling speed, the engine-pump ejection flow rate being a flow rate of a working fluid ejected from the engine pump to the assist device via the restricting mechanism, and wherein the motor-pump controller is configured to control a motor-pump ejection flow rate such that an insufficient flow rate of the working fluid is covered by the motor-pump ejection flow rate, the insufficient flow rate being a shortage in the required receiving flow rate not covered by the engine-pump ejection flow rate.

Methods and systems are provided for a vehicle adapted to be operated based on fuel combustion or electric power. In one example, an accessory train of the vehicle, including an air conditioning pump and a power steering pump, may be operated according to a first mode or according to a second mode based on a power system of the vehicle. When in the second mode, the vehicle may be instructed to coordinate operation of the air conditioning pump and the power steering pump.

A method of differentially steering a hydraulically driven vehicle includes measuring left and right swash plate angles of pumps which drive left and right wheels of the vehicle and if the angles are different from one another and the larger swash plate angle is equal to or exceeds a threshold value then reducing the larger swash plate angle. If the larger swash plate angle is between the threshold value and a lower limit, or below the lower limit the swash plate angle is increased. Control systems and vehicles include swash plate angle sensors and actuators in communication with a controller which effects the steering control method.

A steering system installed on a vehicle, including: a steering mechanism including a steering member and configured to enable a wheel to be steered in accordance with a movement of the steering member; an operation assist device configured to apply a torque to a steering shaft for assisting an operation of a steering operation member; a steering assist device configured to assist the movement of the steering member utilizing a working fluid; and a controller configured to control a torque applied to the steering shaft by the operation assist device and control a supply flow rate of the working fluid, wherein the steering assist device assists the movement of the steering member with an assist force that depends on the supply flow rate, and the controller increases the supply flow rate when an operation speed of the steering operation member becomes equal to or higher than a set threshold speed.

Methods, apparatus, and articles of manufacture are disclosed to modify a steering assist of a hydraulic power steering system. A disclosed method includes calculating modifier values based on sensor data of a vehicle, calculating a torque modifier value based on the modifier values, and generating a final torque assist based on the torque modifier value and a base torque assist, the final torque assist to be applied to a steering system of the vehicle.

A calculator or an electronic control unit (ECU) calculates an instruction value of a column assist torque and a rack assist torque output from a column actuator, or a column motor, and a rack actuator, or a rack motor, based at least on a torsion torque. The calculator includes a base assist controller, a stabilization controller, and an adder. The base assist controller individually or commonly calculates a base assist torque based on the torsion torque. The stabilization controller individually or commonly calculates a stabilization torque for stabilizing a steering system. The adder performs addition of the base assist torque and the stabilization torque.

A turning system is configured to move a turning shaft to turn a left wheel and a right wheel of a vehicle. The turning shaft is configured to couple the left wheel and the right wheel to each other. A torsion bar is engaged with the turning shaft via a steering gear box. The turning system includes: a turning mechanism including (i) an electric turning mechanism including an electric motor configured to rotate a portion of the torsion bar which is located upstream of the steering gear box and (ii) a hydraulic turning mechanism configured to apply a moving force to the turning shaft in an axial direction, the moving force being produced by a hydraulic pressure; and an electric-motor controller configured to control the electric motor based on a frictional force in the turning mechanism and a road-surface reaction force that acts between (a) a tire on the left wheel and a tire on the right wheel and (b) a road surface.

Methods and systems are provided for a vehicle adapted to be operated based on fuel combustion or electric power. In one example, an accessory train of the vehicle, including an air conditioning pump and a power steering pump, may be operated according to a first mode or according to a second mode based on a power system of the vehicle. When in the second mode, the vehicle may be instructed to coordinate operation of the air conditioning pump and the power steering pump.

An apparatus for use in turning steerable vehicle wheels includes first and second pumps driven by a vehicle engine to supply fluid under pressure to a power steering motor assembly connected with the vehicle wheels. The first pump is sized to provide a fluid flow required by the power steering motor assembly to effect a first vehicle maneuver when the engine speed is at or above a first predetermined speed. A valve directs fluid flow from the second pump to the power steering motor assembly, which when combined with the fluid flow of the first pump is sufficient for the power steering assembly to effect a second vehicle maneuver when the engine speed is at or above the first predetermined speed. A greater fluid flow is required to effect the second vehicle maneuver than to effect the first vehicle maneuver.