ELECTRIC PARKING BRAKE SYSTEM AND METHOD FOR CONTROLLING THE ELECTRIC PARKING BRAKE SYSTEM

• US 20080071456A1
• Filed: 09/14/2007
• Published: 03/20/2008
• Est. Priority Date: 09/15/2006
• Status: Active Grant

• Current Assignee: Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Original Assignee: Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Inventors: SHIRAKI, Takahiro
• Granted Patent: US 7,925,408 B2
• Time in Patent Office: Days
• US Class Current: 701/70
• CPC Class Codes: B60T 13/746 and mechanical transmission of the braking action
• CPC Class Codes: B60T 2201/06 Hill holder; Start aid systems on inclined road
• CPC Class Codes: B60T 7/122 for locking of reverse movement
• CPC Class Codes: H02P 3/04 Means for stopping or slowing by a separate brake, e.g. friction brake or eddy-current brake

Abstract

During the standstill state maintenance control executed by an electric parking brake system, the moving force-based target tension Frefb is determined based on the inclination angle of a vehicle and the shift position each time the predetermined program is executed, and the tentative target tension Fref(n) in the current routine is set to a smaller value from among the moving force-based target tension Frefb and the maximum value Fmax. The control target tension Fref(n)* is set to a larger value from among the control target tension (the final target tension) Fref(n−1)* in the immediately preceding routine and the tentative target value Fref(n). Even if the tentative target tension Fref(n) is smaller than the control target tension Fref(n−1)*, the control target value Fref(n)* is not set to a value smaller than the control target tension Fref(n−1)*.

Claims

1. An electric parking brake system, comprising:

a brake that includes a rotating body which has a friction face and which rotates together with a wheel, a friction member which is fitted to a non-rotating body so as to be movable relative to the non-rotating body and which suppresses a rotation of the rotating body when being pushed against the friction face of the rotating body, and a pushing mechanism that pushes the friction member against the friction face of the rotating body;

an electric motor;

a motion conversion mechanism that converts a rotation of a rotating shaft of the electric motor into a linear motion of an output member of the motion conversion mechanism;

a connection unit that is connected at one end to the output member of the motion conversion mechanism, and that is connected at the other end to the pushing mechanism;

a maintaining mechanism that maintains a friction member pushing force that is a force with which the friction member is pushed against the friction face in the brake, when electric current is not supplied to the electric motor; and

a pushing force control unit that controls the electric motor such that the friction member pushing force in the brake approaches a target value that is set based on a moving force applied to a vehicle,

wherein the pushing force control unit includes a tentative target value setting unit that sets a tentative target value of the friction member pushing force each time a predetermined condition is satisfied while the brake is on; and

a final target value setting unit that sets a target value in a current routine to a target value in an immediately preceding routine when the tentative target value in the current routine, which is set by the tentative target value setting unit, is equal to or smaller than the target value in the immediately preceding routine, and that sets the target value in the current routine to the tentative target value in the current routine, which is set by the tentative target value setting unit, when the tentative target value in the current routine is larger than the target value in the immediately preceding routine.

2. The electric parking brake system according to claim 1, wherein:

the pushing force control unit includes a brake-application time control unit that applies the brake by controlling the electric motor based on a command to apply the brake, and a standstill state maintenance control unit that controls the friction member pushing force to a value at which the vehicle is maintained at a standstill when the brake is on after a control executed by the brake-application time control unit ends; and

the standstill state maintenance control unit includes the tentative target value setting unit and the final target value setting unit.

3. The electric parking brake system according to claim 1, wherein the tentative target value setting unit includes an inclination angle-based target value setting unit that sets the tentative target value based on an inclination angle of the vehicle.

4. The electric parking brake system according to claim 3, wherein the inclination angle-based target value setting unit includes a malfunction-time setting unit that sets the target value to a maximum value of an output power that can be produced by the electric motor when an inclination angle sensor that detects the inclination angle of the vehicle malfunctions.

5. The electric parking brake system according to claim 1, wherein the tentative target value setting unit includes a shift position-based target value setting unit that sets the tentative target value based on a shift position selected in the vehicle.

6. The electric parking brake system according to claim 2, wherein the standstill state maintenance control unit causes the friction member pushing force to approach the target value when the friction member pushing force is smaller than the target value.

7. The electric parking brake system according to claim 6, wherein the standstill state maintenance control unit controls the friction member pushing force to a value equal to or larger than the target value.

8. A method for controlling an electric parking brake system, comprising:

setting a tentative target value of a friction member pushing force in a brake, which is set based on a moving force applied to a vehicle, each time a predetermined condition is satisfied while the brake is on, the brake including;

a rotating body that has a friction face and that rotates together with a wheel;

a friction member that is fitted to a non-rotating body so as to be movable relative to the non-rotating body and that suppresses a rotation of the rotating body when being pushed against the friction face of the rotating body; and

a pushing mechanism that pushes the friction member against the friction face of the rotating body;

setting a target value in a current routine to a target value in an immediately preceding routine when the set tentative target value in the current routine is equal to or smaller than the target value in the immediately preceding routine; and

setting the target value in the current routine to the tentative target value in the current routine when the tentative target value in the current routine is larger than the target value in the immediately preceding routine.

9. The method according to claim 8, wherein the brake is applied by controlling the electric motor based on a command to apply the brake, and the friction member pushing force is controlled to a value at which the vehicle is maintained at a standstill when the brake is on after a control to apply the brake ends.

10. The method according to claim 8, wherein the tentative target value is set based on an inclination angle of the vehicle.

11. The method according to claim 10, wherein the target value is set to a maximum value of an output power that can be produced by the electric motor when an inclination angle sensor that detects the inclination angle of the vehicle malfunctions.

12. The method according to claim 8, wherein the tentative target value is set based on a shift position selected in the vehicle.

13. The method according to claim 9, wherein the friction member pushing force is caused to approach the target value when the friction member pushing force is smaller than the target value.

14. The method according to claim 13, wherein the friction member pushing force is controlled to a value equal to or larger than the target value.