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

• US 20080071454A1
• 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 7,734,408 B2
• Time in Patent Office: Days
• US Class Current: 701/70
• CPC Class Codes: B60L 2240/30 Parking brake position
• CPC Class Codes: B60L 7/24 with additional mechanical or electromagnetic braking
• 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

Abstract

In an electric parking brake system including a tension control unit that controls the friction member pushing force in a brake by controlling the tension of a cable, the target tension is set to a larger value when a vehicle is maintained at a standstill on a downhill slope than when the vehicle is maintained at a standstill on an uphill slope.

Claims

1. An electric parking brake system, comprising:

a drum brake that includes;

a drum which rotates together with a wheel of a vehicle and of which an inner peripheral face is used as a friction face;

a shoe which is fitted to a backing plate that is a non-rotating body so as to be movable relative to the backing plate, and which has a friction member on an outer peripheral face; and

a pushing mechanism that pushes the shoe against the friction face to suppress a rotation of the drum;

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 cable 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 drum brake, when electric current is not supplied to the electric motor; and

a tension control unit that controls a tension of the cable by controlling the electric motor such that the friction member pushing force in the drum brake is controlled, wherein the tension control unit includes an inclination-based tension control unit that makes the tension of the cable different depending on whether the vehicle is maintained at a standstill on an uphill slope or a downhill slope, even when an absolute value of an inclination angle of the uphill slope and an absolute value of an inclination angle of the downhill slope are equal to each other and a drive power is not applied to the vehicle.

2. The electric parking brake system according to claim 1, wherein the inclination-based tension control unit includes an inclination-based target value setting unit that sets a target value of the tension to a larger value when the vehicle is maintained at a standstill on a downhill slope than when the vehicle is maintained at a standstill on an uphill slope.

3. The electric parking brake system according to claim 2, wherein the inclination-based target value setting unit sets the target value based on at least one of an inclination angle of a road on which the vehicle is at a standstill and a shift position of a transmission of the vehicle.

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

the inclination-based tension control unit includes an application start-time control unit that executes a control such that the tension of the cable approaches the target value when the drum brake is applied; and

the tension control unit includes a standstill state maintenance control unit that actuates the electric motor to increase the tension, when the tension of the cable is lower than the target value in a state in which the friction member pushing force in the drum brake is maintained by the maintaining mechanism.

5. The electric parking brake system according to claim 4, wherein the standstill state maintenance control unit actuates the electric motor such that the tension is equal to or higher than the target value.

6. A method for controlling the electric parking brake system including:

a drum brake that includes;

a drum which rotates together with a wheel of a vehicle and of which an inner peripheral face is used as a friction face;

a shoe which is fitted to a backing plate that is a non-rotating body so as to be movable relative to the backing plate, and which has a friction member on an outer peripheral face; and

a pushing mechanism that pushes the shoe against the friction face to suppress a rotation of the drum;

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 cable 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 drum brake, when electric current is not supplied to the electric motor; and

a tension control unit that controls a tension of the cable by controlling the electric motor such that the friction member pushing force in the drum brake is controlled, the method comprising;

making the tension of the cable different depending on whether the vehicle is maintained at a standstill on an uphill slope or a downhill slope, even when an absolute value of an inclination angle of the uphill slope and an absolute value of an inclination angle of the downhill slope are equal to each other and a drive power is not applied to the vehicle.

7. The method according to claim 6, wherein a target value of the tension is set to a larger value when the vehicle is maintained at a standstill on a downhill slope than when the vehicle is maintained at a standstill on an uphill slope.

8. The method according to claim 7, wherein the target value is set based on at least one of an inclination angle of a road on which the vehicle is at a standstill and a shift position of a transmission of the vehicle.

9. The method according to claim 7, further comprising:

executing a control such that the tension of the cable approaches the target value when the drum brake is applied; and

actuating the electric motor to increase the tension, when the tension of the cable is lower than the target value in a state in which the friction member pushing force in the drum brake is maintained by the maintaining mechanism.

10. The method according to claim 9, wherein the electric motor is actuated such that the tension is equal to or higher than the target value.