Electric parking brake device and release method therefor

Patent metadata

Field	Value
Publication number	US-9631686-B2
Application number	US-201514660206-A
Country	US
Kind code	B2
Filing date	Mar 17, 2015
Priority date	Jul 31, 2014
Publication date	Apr 25, 2017
Grant date	Apr 25, 2017

Abstract

An electric parking brake device holds a parking brake in a braking state by a rotation-linear motion conversion mechanism that converts rotation of an electric motor into a motion in a linear direction, and releases the parking brake by the rotation-linear motion conversion mechanism. In a case of releasing the parking brake, the electric motor is controlled by combining PWM control and ON/OFF control with each other. When the electric motor is driven according to the PWM control, and a predetermined time has elapsed after start of the PWM control, then the electric motor is changed to drive according to the ON/OFF control. In the ON/OFF control, a change in which a drive current of the electric motor is decreased stepwise is detected, whereby a torque drop of the rotation-linear motion conversion mechanism is detected.

First claim

What is claimed is:

1. An electric parking brake device that holds a parking brake in a braking state by a rotation-linear motion conversion mechanism that converts rotation of an electric motor into a motion in a linear direction, and releases the parking brake by the rotation-linear motion conversion mechanism, the electric parking brake device comprising:
a drive control device configured to control the parking brake, the drive control device driving the electric motor according to pulse width modulation (PWM) control and changing the electric motor to drive according to ON/OFF control after a predetermined time has elapsed after start of the PWM control in a case of releasing the parking brake.

2. The electric parking brake device according to claim 1 ,
wherein the drive control device detects a torque drop of the rotation-linear motion conversion mechanism after changing the electric motor to the drive according to the ON/OFF control.

3. The electric parking brake device according to claim 2 ,
wherein, in a case of detecting the torque drop of the rotation-linear motion conversion mechanism, the drive control device changes the electric motor from the drive according to the ON/OFF control to the drive according to the PWM control.

4. The electric parking brake device according to claim 3 ,
wherein the drive control device executes the PWM control during a predetermined time.

5. The electric parking brake device according to claim 2 ,
wherein the drive control device detects the torque drop of the rotation-linear motion conversion mechanism based on a predetermined value or more of a change of a drive current in the ON/OFF control of the electric motor.

6. The electric parking brake device according to claim 5 ,
wherein the predetermined value or more of the change of the drive current is a change in which the drive current is decreased stepwise.

7. The electric parking brake device according to claim 2 ,
wherein, in a case of not detecting the torque drop of the rotation-linear motion conversion mechanism during a predetermined time, the drive control device prohibits start of a vehicle or notifies a driver of non-detection of the torque drop.

8. The electric parking brake device according to claim 1 ,
wherein the drive control device includes an electronic control unit (ECU) that makes control to drive the electric motor based on a signal from a parking switch or a vehicle.

9. An electric parking brake device comprising:
a piston that presses a brake pad against a rotor;
a transfer mechanism that moves the piston forward by converting rotation of an electric motor into a motion in a linear direction, presses the brake pad against the rotor, and holds the brake pad at a brake position;
a ball-and-ramp mechanism that temporarily stops actuation of the piston with respect to the rotation of the electric motor after the brake pad starts to be released; and
a drive control device that makes control to drive the electric motor, the drive control device drives the electric motor according to pulse width modulation (PWM) control when the brake pad starts to be released, and after a predetermined time has elapsed after start of the PWM control, changes the electric motor to ON/OFF control and drives the electric motor.

10. The electric parking brake device according to claim 9 ,
wherein the predetermined time is a time while the actuation of the piston is temporarily stopped with respect to the rotation of the electric motor after release control for the brake pad is started, or a time until the actuation of the piston is started after the release control for the brake pad is started.

11. The electric parking brake device according to claim 10 ,
wherein the drive control device detects a decrease of pressing force of the brake pad to the rotor based on a predetermined value or more of a change of a drive current in the ON/OFF control for the electric motor.

12. The electric parking brake device according to claim 11 ,
wherein the predetermined value or more of the change of the drive current is a change in which the drive current is decreased stepwise.

13. The electric parking brake device according to claim 11 ,
wherein, after detecting the decrease of the pressing force of the brake pad to the rotor, the drive control device performs the PWM control for the electric motor during a predetermined time, and spaces the brake pad apart from the rotor.

14. The electric parking brake device according to claim 9 ,
wherein the drive control device includes an electronic control unit (ECU) that makes control to drive the electric motor based on a signal from a parking switch or a vehicle.

15. A release method of an electric parking brake device that holds a parking brake in a braking state by a rotation-linear motion conversion mechanism that converts rotation of an electric motor into a motion in a linear direction, and releases the parking brake by the rotation-linear motion conversion mechanism, the release method comprising:
driving the electric motor according to pulse width modulation (PWM) control;
sensing that a predetermined time has elapsed after start of the PWM control; and
changing the electric motor to drive according to ON/OFF control.

16. The release method of an electric parking brake device according to claim 15 , further comprising:
detecting a torque drop of the rotation-linear motion conversion mechanism after the changing the electric motor to drive according to ON/OFF control.

17. The release method of an electric parking brake device according to claim 16 , further comprising:
changing the electric motor from the drive according to the ON/OFF control to the drive according to the PWM control during a predetermined time in a case of detecting the torque drop of the rotation-linear motion conversion mechanism.

18. The release method of an electric parking brake device according to claim 16 ,
wherein the torque drop of the rotation-linear motion conversion mechanism is detected based on a predetermined value or more of a change of a drive current in the ON/OFF control of the electric motor.

19. The release method of an electric parking brake device according to claim 18 ,
wherein the predetermined value or more of the change of the drive current is a change in which the drive current is decreased stepwise.

20. The release method of an electric parking brake device according to claim 16 , further comprising:
in a case of not detecting the torque drop of the rotation-linear motion conversion mechanism during a predetermined time, prohibiting start of a vehicle or notifies a driver of non-detection of the torque drop.

Assignees

• Hitachi Automotive Systems Ltd

Inventors

• Takei Osamu

Classifications

• F16D2125/48

  with parallel stationary axes, e.g. spur gears · CPC title

• F16D65/183

  with force-transmitting members arranged side by side acting on a spot type force-applying member · CPC title

• F16D2125/50

  with parallel non-stationary axes, e.g. planetary gearing · CPC title

• F16D2121/02

  Fluid pressure · CPC title

• F16D2121/24

  using motors · CPC title