ESP Control Function

ESP Pressure Build-up Control Mode

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Part 2 Of 2:

(The control process or valve positions shown in the example relate to the FL brake).

A brake intervention to stabilize the vehicle is introduced by the ESP control module.
At the start of the ESP control the switchover solenoid valve (Y18) and pressure-holding solenoid valve (y8) is closed.
The ASR/ESP charging pump (M15) charges the high-pressure/return pump (p1) to 3-15 bar via the charging piston unit (14) and the front axle precharge solenoid valve (y16).
The pressure produced by the high-pressure/return pump (p1) is led to the FL wheel brake via the open pressure-holding solenoid valve (y6).
The pressure limiting valve (approx. 170 bar) integrated in the front axle switchover solenoid valve (y18) is required to limit high pressure.
The charging pressure is also applied to the actuated (closed) pressure-holding solenoid valves (y10 and y12) of the rear axle via the open rear axle switchover solenoid valve (y19).

ESP Pressure-Holding Control Mode





(The control process or valve positions shown in the example relate to the FL brake).

The pressure-holding phase is introduced by actuating (closing) the pressure-holding solenoid valve (y6). The pressure reduction solenoid valve (y7) remains closed in this control phase.

ASR Pressure Reduction Control Mode





(The control process or valve positions shown in the example relate to the FL brake).

The pressure reduction phase is introduced by actuating (opening) the pressure reduction solenoid valve (y7). The pressure-holding solenoid valve (y6) remains dosed. The ASR/ESP charging pump (M15) and high-pressure/return pump (p1) are also actuated in this control phase. The switchover solenoid valve (y18) is closed and the charging solenoid valve (y16) is opened.
The brake fluid flows back to the charging pressure circuit via the open charging solenoid valve (y16).
The brake fluid returned at the same time by the high-pressure/return pump (p1) is also fed back into the charging pressure circuit of the front axle though the pressure limiting valve (170 bar) integrated in the switchover solenoid valve (y18).