HYDRAULIC POWER STEERING SYSTEM

• US 20130138297A1
• Filed: 11/16/2012
• Published: 05/30/2013
• Est. Priority Date: 11/24/2011
• Status: Active Grant

• Current Assignee: Jtekt Corporation (Toyota Motor Corporation)
• Original Assignee: Jtekt Corporation (Toyota Motor Corporation)
• Inventors: SAKAMAKI, Masahiko
• Granted Patent: US 8,930,077 B2
• Time in Patent Office: Days
• US Class Current: 701/41
• CPC Class Codes: B62D 5/09 characterised by means for actuating valves
• CPC Class Codes: B62D 6/08 responsive only to driver input torque

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.

Claims

1. A hydraulic power steering system that generates a steering assist force by supplying hydraulic fluid from a hydraulic pump to a power cylinder that is coupled to a steering mechanism of a vehicle, via a hydraulic control valve that is not mechanically coupled to a steering member, characterized by comprising:

steering torque detection means for detecting a steering torque that is applied to the steering member;

steering angular velocity detection means for detecting a steering angular velocity of the steering member;

a valve driving motor that is used to control an opening degree of the hydraulic control valve;

opening degree command value computation means for computing an opening degree command value for the hydraulic control valve; and

valve driving motor control means for controlling the valve driving motor based on the opening degree command value computed by the opening degree command value computation means, wherein

the opening degree command value computation means includes;

basic command value setting means for setting a basic command value used to obtain a basic opening degree command value, using the steering torque detected by the steering torque detection means;

damping control means for setting a damping control value used to increase the steering assist force in a turning direction when a direction of the steering torque detected by the steering torque detection means is the turning direction, a magnitude of the steering torque is larger than or equal to a first threshold, a direction of the steering angular velocity detected by the steering angular velocity detection means is a returning direction and a magnitude of the steering angular velocity is higher than or equal to a second threshold; and

computation means for computing the opening degree command value based on the basic command value set by the basic command value setting means and the damping control value set by the damping control means.

2. The hydraulic power steering system according to claim 1, further comprising:

vehicle speed detection means for detecting a vehicle speed of the vehicle, wherein

the basic command value setting means is configured to set a basic steering assist force command value as the basic command value, based on the steering torque detected by the steering torque detection means and the vehicle speed detected by the vehicle speed detection means,

the damping control means is configured to set the damping control value that corresponds to the steering angular velocity detected by the steering angular velocity detection means, when the direction of the steering torque detected by the steering torque detection means is the turning direction, the magnitude of the steering torque is larger than or equal to the first threshold, the direction of the steering angular velocity detected by the steering angular velocity detection means is the returning direction and the magnitude of the steering angular velocity is higher than or equal to the second threshold, and

the computation means is configured to compute the opening degree command value based on the basic steering assist force command value set by the basic command value setting means and the damping control value set by the damping control means.

3. The hydraulic power steering system according to claim 2, wherein the damping control means is configured to set an absolute value of the damping control value such that the absolute value of the damping control value increases as an absolute value of the steering angular velocity detected by the steering angular velocity detection means increases, and to set a direction of the damping control value such that the direction of the damping control value is opposite to the direction of the steering angular velocity.