Patent ID: 7631722
Filing Date: 2009-12-15
Classification: B62D

Abstract:
1. A power steering system, comprising: a hydraulic power cylinder for assisting a steering force of a steering mechanism connected to wheels, and having a first hydraulic chamber and a second hydraulic chamber, a first pathway connected to said first hydraulic chamber, a second pathway connected to said second hydraulic chamber, a reversible pump having a pair of outlet openings continuously connected to said first pathway and said second pathway, said reversible pump selectively supplying an outlet pressure to said pair of outlet openings, an electric motor for revolving said reversible pump in a forward/reverse direction, steering-load detection means for detecting or estimating steering load of a steering wheel for executing a steering control over said wheels, steering-speed detection means for detecting or estimating steering speed of said wheels, and motor control means for outputting, based on said steering load, a driving signal to said electric motor so as to causing said electric motor to generate a desirable hydraulic pressure, said motor control means also executing a torque control over said electric motor if said steering speed is higher than a predetermined value so that a difference between a torque command value of said driving signal and an actual torque of said electric motor becomes smaller, and executing a control over said electric motor based on revolution speed of said electric motor if said steering speed is lower than said predetermined value so that a difference between a revolution speed command valued of said driving signal and an actual revolution speed of said electric motor becomes smaller.