ETS, ABS control mode, function

P42.35-0206-76

Braking process in normal mode

ABS control mode pressure increase

Each ABS control process starts with a normal braking process which the driver performs via the brake pedal. The ETS control module recognizes the braking process via the stop lamp switch and decelerated wheel speeds.

The brake pressure is first increased via the switchover solenoid valves (y18 and y19) and then at the front axle via the solenoid valves (y6 and y8) and at the rear axle via the solenoid valves (y10 and y12).

The pressure is reduced via the same solenoid valve during a normal braking process.

b Brake pressure

P42.35-0207-76

ABS control mode pressure holding

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

If a wheel tends towards locking during the braking process, ABS prevents a further pressure increase. The ETS control module introduces the pressure holding phase from the slip values of the braked wheels.

The pressure holding phase is introduced by actuation of the solenoid valve (y8). The solenoid valves (y8 and y9) are closed in this control phase, as a result pressure in theVR brake caliper remains constant.

b Brake pressure

P42.35-0208-76

ABS control mode pressure reduction

b Brake pressure

e Reduced pressure

ABS control mode pressure reduction

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

The ETS control module introduces the pressure reduction phase from the slip values of the braked wheels.
The pressure reduction phase is introduced by actuation (opening) of the solenoid valve (y9). The solenoid valve (y8) remains actuated (closed) in this control phase.

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During the pressure reduction phase, brake fluid flows back into the high pressure/return pump (p1) via the accumulator (11). From there the high pressure/return pump in the front axle brake circuit delivers brake fluid back to the master brake cylinder against the existing pressure. A silencer (10) is fitted for each brake circuit to reduce delivery noise

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