Electric Parking Brake (EPB) Description and Operation

Description

EPB Description. The EPB (Electronic Parking Brake) system is an electronic parking brake. Unlike conventional parking brake systems, which are operated by a parking brake pedal or lever, the EPB system sends a signal to the ECU when the driver presses the EPB switch. The ECU then operates the EPB actuator with the motor-reducers, pushing the piston into the caliper to generate braking force. The main EPB functions are as follows:

• Static Application
• Emergency braking in case of hydraulic brake failure
• Automatic Application

EPB Function

1. 1
   Switch operation while stationary (Static Park)

   • Manually apply the parking brake by pressing the EPB switch while the vehicle is stationary.
   • With the ignition ON, the parking brake is applied by reducing the clamping force on a slope of less than 8%.
   • Otherwise, it always applies at full clamping force.
2. 2
   Switch release while stationary (Static Release)

   • Release the parking brake manually by pressing the EPB switch while the vehicle is stationary.
   • For safety, it is released only when the ignition is on and the brake pedal is depressed.
3. 3
   Dynamic Emergency Braking (Dynamic Braking)

   • Electronically Controlled Deceleration (ECD): When the EPB switch is used while driving, a request is sent to the VDC only when the switch is operated, so that hydraulic braking is performed by the VDC instead of the EPB actuator.
   • Rear Wheel Unlock (RWU): If the VDC is not operating normally (VDC Fail) when the EPB switch is used while driving, and wheel speed information can be received, the EPB actuator will maintain safe vehicle deceleration by itself only while the switch is operated.
   • Slow Ramp Up (SRU): If the VDC is not operating normally (VDC Fail) when the EPB switch is pressed while driving, and wheel speed information cannot be received, the EPB will gradually increase the parking force by itself to perform braking only while the switch operation is maintained.
4. 4
   Automatic EPB Apply (Auto Apply)

   • When the vehicle stops while Auto Vehicle Hold (AVH) is ON, the EPB will apply automatically after the engine is turned off.
5. 5
   Automatic EPB Release (Release on Acceleration)

   • The parking brake is automatically released when the accelerator pedal is depressed while the EPB is applied.
   • For safety, automatic release occurs only when all of the following conditions are met:

   1. Engine running
   2. The seat belt is fastened.
   3. Driver's door, trunk and hood are closed.

   • To prevent the vehicle from rolling down a slope, it is released automatically only after a torque above a certain level, based on the grade, has been generated.
6. 6
   Re-application of EPB force when the vehicle moves downhill (Roll-back Re-clamping)

   • Additional EPB force is generated when downhill vehicle movement is detected after EPB force has been applied.
   • With the engine off, this function is active only when wheel speed information can be received (i.e., within 3 minutes after the engine is turned off).
7. 7
   P to X (Automatic EPB Force Release for Gear Shifting): When the shift lever is moved from P or N to D or R, the parking brake is automatically released. However, this is possible only when the engine is running and the brake pedal is depressed, to ensure safe automatic release.