ESP Control Function

ESP Pressure Build-up Control Mode





The control process or valve positions shown in the example relate to the FR brake.

A brake intervention to stabilize the vehicle is introduced by the ESP control module.

At the start of ESP control the switchover solenoid valves (y18 and y19) are switched to the "shut-off position" (closed) and the high-pressure/return pump (m1) is actuated, From a speed of greater than 20 km/h (starting off range) the BAS solenoid valve (A7/7y1) in the brake booster (A7/7) is actuated (opened). Atmospheric pressure is led to the back of the diaphragms in the brake booster and consequently a pressure of approx. 5 bar is generated which is applied as pilot pressure on the suction side of the high-pressure/return pumps.

The inlet solenoid valve (y22) is only opened during the pressure build up phases, and the self-priming high-pressure/return pump (p1) draws brake fluid out of the reservoir via the inlet solenoid valve (y22) and via the master brake cylinder.

The pressure limiting valve (approx. 170 bar) integrated in the switchover solenoid valve (y18) serves to limit high pressure.

ESP Hold Pressure Control Mode





The control process and valve positions shown in the example relate to the FR brake.
The ESP hold pressure control mode starts if a more powerful brake intervention is no longer required for stabilization.

The inlet solenoid valve (y22) is closed. As a result the pressure in the brake caliper cannot be increased via the high-pressure/return pump (p1).

ESP Pressure Reduction Control Mode





The control process and valve positions shown in the example relate to the FR brake.
If the brake pressure required for stabilization is too high, the ESP pressure reduction control mode starts.

The pressure reduction phase is introduced by opening the switchover solenoid valve (y18). The solenoid valve (y8) remains open and the solenoid valve (y9) closed.
The returning brake fluid flows back to the brake fluid reservoir via the high-pressure/return pump (p1) through the switchover solenoid valve (y18) via the master brake cylinder.
The self-priming high-pressure/return pump (p1) is also actuated in these control phases.