POWER STEERING SYSTEM

摘要

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.

主权项

1. A power steering system comprising:
an electric power steering including a motor serving as an electric actuator that generates a first steering assist force based on a torsion amount of a first torsion bar to which steering torque is applied; and a hydraulic power steering including a hydraulic actuator that generates a second steering assist force based on a flow rate of a hydraulic fluid supplied from a pump that operates using an internal combustion engine as a driving source, and a control valve that controls supply of the hydraulic fluid to the hydraulic actuator and drain of the hydraulic fluid from the hydraulic actuator based on a torsion amount of a second torsion bar to which the steering torque and the first steering assist force are applied, wherein the second torsion bar has a torsional stiffness that is equal to or substantially equal to a torsional stiffness of the first torsion bar.