Abstract: A power steering apparatus includes a steering shaft, a hydraulic power cylinder, a hydraulic pump, a steering shaft actuator, a condition sensor, and a fluid pressure controller. The steering shaft is connected to a steering wheel. The hydraulic power cylinder is mechanically linked to the steering shaft. The hydraulic power cylinder has first and second fluid pressure chambers for producing an assist steering effort. The hydraulic pump supplies a first fluid pressure to the hydraulic power cylinder. The steering shaft actuator receives a second fluid pressure from the hydraulic pump, and applies a torque to the steering shaft by the second fluid pressure. The condition sensor collects information concerning at least one of an associated host vehicle, an associated driver and an associated road. The fluid pressure controller receives the collected information from the condition sensor, and controls the steering shaft actuator based on the collected information.

Abstract: Right-turn and left-turn aimed input shaft drive mechanisms are provided, each comprising a piston unit that slides in a bore formed in an output shaft and a contact surface that is formed on an input shaft. Under normal cruising of a vehicle, a comfortable steering feeling is given by a relatively small counter torque that is produced by a contact between the piston unit and a second inclined surface of the contact surface, and upon stray running of the vehicle due to doze in driving or the like, a relatively large steering torque is produced by a contact between the piston unit and a first inclined surface of the contact surface. An inclination angle of the second inclined surface relative to a traveling path of the piston unit is greater than that of the first inclined surface.

Abstract: A power steering apparatus includes a steering shaft, a hydraulic power cylinder, a hydraulic pump, a steering shaft actuator, a condition sensor, and a fluid pressure controller. The steering shaft is connected to a steering wheel. The hydraulic power cylinder is mechanically linked to the steering shaft. The hydraulic power cylinder has first and second fluid pressure chambers for producing an assist steering effort. The hydraulic pump supplies a first fluid pressure to the hydraulic power cylinder. The steering shaft actuator receives a second fluid pressure from the hydraulic pump, and applies a torque to the steering shaft by the second fluid pressure. The condition sensor collects information concerning at least one of an associated host vehicle, an associated driver and an associated road. The fluid pressure controller receives the collected information from the condition sensor, and controls the steering shaft actuator based on the collected information.