TRW Aftermarket explains electric park brake features and benefits

ZF TRW recently announced production of its sixty millionth Electric Park Brake (EPB) motor-on-caliper unit. An important milestone for ZF TRW, this highlighted the success of the company’s field proven, EPB product portfolio, now in production in its fifth generation.

ZF TRW was first to market with its EPB system in 2001 which pioneered with Lancia, Audi and VW and has since launched on Renault, Nissan and Daimler platforms, and more recently on the BMW X4 and BMW i8, Jeep Renegade, Fiat 500X, Ford F150, Honda Accord, Nissan Qashqai, Range Rover Evoque and more.

The breakthrough technology was first developed at ZF TRW’s global technical centre in Koblenz, Germany and the company also now produces EPB in North America and China.

Electric Park Brakes are used on passenger vehicles to hold the vehicle stationary on grades and flat roads. This was traditionally carried out using a manual parking brake.

With EPB, the driver activates the holding mechanism with a button and the brake pads are then electrically applied onto the rear brakes. This is accomplished by an Electronic Control Unit (ECU) and an actuator mechanism.

There are two mechanisms currently used in vehicle production, cable puller systems and caliper integrated systems, such ZF TRW’s EPB.

In caliper integrated systems, the brake caliper provides a connection between hydraulic actuation of the foot brake and electrically actuated parking brake.

The motor or transmission unit (actuator), which operates the parking brake, is screw-fixed directly to the brake caliper housing. The parking brake is actuated via a switch in the vehicle interior. The absence of a hand brake lever frees up space inside the vehicle. With no hand brake cables, there are no temperature problems (such as freezing) or mechanical wear, offering optimum brake power in all conditions.

EPB is part of ZF TRW’s ongoing commitment to enhance overall brake system performance and driver safety and comfort. In addition to providing park brake functionality, EPB is a fully integral part of the brake system with features such as dynamic actuation and brake pad wear sensing and reduces the degradation associated with mechanical systems.

The EPB also helps enhances safety in emergency situations. For example, in the case of a hydraulic system failure (which is the only reason to apply the parking brake during driving), the rear wheels are alternately braked, so that breakaway of the vehicle caused by a blocked rear axle is ruled out.

Further, the hill-hold function, which applies brakes to prevent roll-back when pulling away on a gradient, can also be implemented using the EPB. An example is driving into a full multi-storey car park. When vehicles are moving slowly, and the driver has to stop on a steep ramp, moving off smoothly is difficult. However, EPB solves this issue by being equipped with a drive away assist system. This opens the parking brake automatically when the engine provides sufficient torque to safely get the car moving. And in the unlikely event of the engine stalling and the car rolling backwards, the system detects this and automatically closes the parking brake.