Electronic Variable Brake Proportioning

Electronic Variable Brake Proportioning

Electronic variable brake proportioning is used to balance front-to-rear braking in place of a traditional rear proportioning valve. The EVBP system uses the ABS system to control the slip of the rear wheels in partial braking range. The braking force of the rear wheels is controlled electronically by using the inlet and outlet valves located in the integrated control unit.

EVBP activation is nearly invisible to the customer since there is no pump motor noise and minimal brake pedal feedback.

Upon entry into EVBP the inlet valve for the rear brake circuit is switched on so that the fluid supply from the master cylinder is shut off. In order to decrease the rear brake pressure, the outlet valve for the rear brake circuit is pulsed. This allows fluid to enter the low pressure accumulator in the hydraulic control unit resulting in a drop in fluid pressure to the rear brakes. In order to increase the rear brake pressure, the outlet valve is switched OFF and the inlet valve is pulsed. This increases the pressure to the rear brakes. This back-and-forth process will continue until the required slip difference is obtained. At the end of EVBP braking (brakes released) the fluid in the LPA drains back to the master cylinder by switching on the electronic shuttle valve.

The EVBP will remain functional during many ABS fault modes. If both the red brake and amber ABS warning indicators are illuminated, the EVBP may not be functioning.