Electric power steering apparatus

• US 6,129,172 A
• Filed: 07/15/1998
• Issued: 10/10/2000
• Est. Priority Date: 07/23/1997
• Status: Expired due to Fees

• Current Assignee: Koyo Seiko Co., Ltd. (Toyota Motor Corporation)
• Original Assignee: Koyo Seiko Co., Ltd. (Toyota Motor Corporation)
• Inventors: Yoshida, Kazuyuki, Nishimoto, Mitsuhiko
• Primary Examiner(s): Swann, J. J.
• Assistant Examiner(s): LUM VANNUCCI, LEE SIN YEE
• Application Number:
  US09/116,086
• Time in Patent Office: 818 Days
• Field of Search: 180/443, 180/446, 364/424.051, 701/41
• US Class Current: 180/446
• CPC Class Codes: B62D 5/0466 for returning the steering wheel to neutral position

Abstract

An electric power steering apparatus is disclosed in which steering return control is maintained when vehicle speed reaches a predetermined vehicle speed range after the vehicle speed has been lower than the speed range, and steering return control is disabled when the vehicle speed reaches the predetermined vehicle speed range after the vehicle speed has been higher than the speed range and steering angular velocity has been higher than a predetermined value. Therefore, the control state between the steering return control and convergence control can preferably be switched so that the steering wheel settles quickly to a steering angle predetermined point based on the vehicle speed and the steering angular velocity even while the steering state is not changing.

Claims

1. An electric power steering apparatus for a vehicle including a steering wheel, comprising:

a motor for steering force assistance;

a steering torque detector detecting a steering torque applied to said steering wheel;

a target value generator producing a target value of said motor current on the basis of the value of said steering torque detected by the steering torque detector;

a motor driver driving said motor utilizing PWM control so that the current of said motor becomes the target value;

a steering angular velocity detector detecting steering angular velocity;

a vehicle speed sensor;

a braking controller braking said motor when the detected value of said steering torque is within a predetermined range, the vehicle speed detected by said vehicle speed sensor is higher than a first vehicle speed, and the steering angular velocity detected by said steering angular velocity detector is higher than a first steering angular velocity;

a driving controller, driving said motor and restoring said steering wheel to a steering angle predetermined point when the vehicle speed is lower than the first vehicle speed, and when the vehicle speed is between the first vehicle speed and a second vehicle speed which is higher than the first vehicle speed and the steering angular velocity is lower than the first steering angular velocity;

a steering return controller controlling restoring of said steering wheel to the steering angle predetermined point when the vehicle speed is lower than a third vehicle speed which is lower than the first vehicle speed, and when the vehicle speed is between the third vehicle speed and the first vehicle speed while carrying out steering return control; and

a steering return control inhibitor disabling steering return control when the vehicle speed is higher than the first vehicle speed, the steering angular velocity is higher than the first steering angular velocity, and the vehicle speed is between the first vehicle speed and the third vehicle speed while inhibiting the steering return control.

2. The electric power steering apparatus according to claim 1, further comprising:

a further controller controlling restoring of said steering wheel to the steering angle predetermined point when the steering angular velocity is lower than a second steering angular velocity which is lower than the first steering angular velocity and falls between the second angular velocity and the first steering angular velocity while carrying out the steering return control; and

a further inhibitor disabling steering return control when the steering angular velocity is higher than the first steering angular velocity and is between the first steering angular velocity and the second steering angular velocity while inhibiting the steering return control.

3. An electric power steering apparatus for a vehicle including a steering wheel, comprising:

a motor for steering force assistance;

a steering torque detector detecting a steering torque applied to said steering wheel;

a target value generator producing a target value of said motor current on the basis of the value of said steering torque detected by the steering torque detector;

a motor driver driving said motor utilizing PWM control so that the current of said motor becomes the target value;

a steering angular velocity detector detecting steering angular velocity;

a vehicle speed sensor;

a braking controller controlling braking of said motor when the detected value of said steering torque detector is within a predetermined range, the vehicle speed detected by said vehicle speed sensor is higher than a first vehicle speed, and the steering angular velocity detected by said steering angular velocity detector is higher than a first steering angular velocity;

a restoring controller controlling driving of said motor and restoring of said steering wheel to a steering angle predetermined point when the vehicle speed is lower than a third vehicle speed which is lower than the first vehicle speed, and when the vehicle speed is between the third vehicle speed and a second vehicle speed which is higher than the first vehicle speed and the steering angular velocity is lower than a second steering angular velocity which is lower than the first steering angular velocity;

a restoring control inhibitor, disabling control of restoring said steering wheel to the steering angle predetermined point when the vehicle speed is between the third vehicle speed and the first vehicle speed and the steering angular velocity is higher than the second steering angular velocity, and when the vehicle speed is between the first vehicle speed and the second vehicle speed and the steering angular velocity is between the second steering angular velocity and the first steering angular velocity, while said braking controller controls braking of said motor; and

a further controller continuously controlling restoring of said steering wheel to the steering angle predetermined point when the vehicle speed is between the third vehicle speed and the first vehicle speed and the steering angular velocity is higher than the second steering angular velocity, and when the vehicle speed is between the first vehicle speed and the second vehicle speed and the steering angular velocity is between the second steering angular velocity and the first steering angular velocity, while said restoring controller carries out the steering return control.

4. An electric power steering apparatus for a vehicle including a steering wheel, comprising:

a motor for steering force assistance;

a steering torque detector detecting a steering torque applied to said steering wheel;

a target value generator producing a target value of said motor current on the basis of the value of said steering torque detected by the steering torque detector;

a motor driver driving said motor utilizing PWM control so that the current of said motor becomes the target value;

a steering angular velocity detector detecting steering angular velocity;

a vehicle speed sensor;

a braking controller controlling braking of said motor in a first vehicle-speed/steering-angular-velocity region when the detected value of said steering torque detector is within a predetermined range, the vehicle speed detected by said vehicle speed sensor is higher than a first vehicle speed, and the steering angular velocity detected by said steering angular velocity detector is higher than a first steering angular velocity;

a restoring controller controlling driving of said motor and restoring of said steering wheel to a steering angle predetermined point in a second vehicle-speed/steering-angular-velocity region where the vehicle speed is lower than a third vehicle speed which is lower than the first vehicle speed, and where the vehicle speed is between the third vehicle speed and a second vehicle speed which is higher than the first vehicle speed and the steering angular velocity is lower than a second steering angular velocity which is lower than the first steering angular velocity;

an inhibitor disabling restoring control in a state wherein said braking controller controls braking of said motor when the relationship between the vehicle speed and the steering angular velocity shifts from the first vehicle-speed/steering-angular-velocity region to a third vehicle-speed/steering-angular-velocity region where the vehicle speed is between the third vehicle speed and the first vehicle speed and the steering angular velocity is higher than the second steering angular velocity, and where the vehicle speed is between the first vehicle speed and the second vehicle speed and the steering angular velocity is between the second steering angular velocity and the first steering angular velocity; and

a further controller controlling restoring of said steering wheel to the steering angle predetermined point when the relationship shifts to the third vehicle-speed/steering-angular-velocity region from a state wherein said restoring controller carries out the control.