ESP control mode, function

P42.45-0236-79

a Suction line

c Depressurized

g Pilot pressure (brake pressure circuit)

d Pilot pressure (precharge circuit)

f High pressure

ESP control mode - pressure build-up

(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 ESP control the front axle switchover solenoid valve (y18) and the solenoid valve (hold) (y8) are closed.

The ASR/ESP charging pump (M15) charges the high pressure and return pump (p1) with 3 - 15 bar via the pressurizing piston unit (14) and the front axle precharge solenoid valve (y16).

The pressure produced by the high pressure and return pump (p1) is led to the FL wheel brake via the opened solenoid valve (hold) (y6) .

The pressure limiting valve integrated in the front axle switchover solenoid valve (y18) is required to limit high pressure (approx. 170bar).

The pilot pressure is also applied to the actuated (closed) rear axle solenoid valves (hold) (y10 and y12) via the opened rear axle switchover solenoid valve (y19)

P42.45-0237-79

a Suction line

b Brake pressure

f High pressure

g Pilot pressure (brake pressure circuit)

c Depressurized

d Pilot pressure (precharge circuit)

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 solenoid valve (hold) (y6). The solenoid valve (release) (y7) remains closed in this control phase.

P42.45-0238-79

a Suction line

c Depressurized

f High pressure

g Pilot pressure (brake pressure circuit)

d Pilot pressure (precharge circuit)

e Reduced pressure

ESP pressure reduction control mode

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

The pressure reduction phase is introduced by actuating (opening) the solenoid valve (release) (y7). The pressure solenoid valve (hold) (y6) remains closed. The ASR/ESP charging pump (M15) and high pressure and return pump (p1) are also actuated in this control phase. The switchover solenoid valve (y18) is closed and the precharge solenoid valve (y16) is open.

The brake fluid flows back into the precharge pressure circuit via the opened precharge solenoid valve (y16).

The brake fluid delivered which is delivered back from the high pressure and return pump (p1) at the same time is also led back into the front axle precharge pressure circuit through the pressure limiting valve (170 bar) integrated in the switchover solenoid valve (y18).