GF42.45-P-3000B ABS control function 15.10.96

MODEL  215 with CODE (472a) Electronic stability program (ESP)


Braking process in normal mode
ABS pressure build-up control mode

Every ABS control starts with a normal braking process which the driver performs via the brake pedal.

The ESP control module recognizes the braking process via the stop lamp switch and decelerated wheel speeds.

The brake pressure is built up via the two switchover solenoid valves (y18 and y19) and the solenoid valves (y6, y8, y10 and y12).
This pressure build up phase can take place individually at each wheel during the ABS control process.

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

b Brake pressure
 
    P42.45-0260-76

ABS hold pressure control mode
The control process or valve positions shown in the example relate to the FR brake.

If a wheel tends to lock during the braking process, ABS prevents a further pressure build-up. The ESP control module introduces the hold pressure phase from the slip values of the braked wheels.

The hold pressure phase is introduced by actuating the solenoid valve (y8). The solenoid valves (y8 and y9) remain closed in this control phase, with the result that the pressure in the FR brake caliper remains constant.





b Brake pressure
 
    P42.45-0261-76

ABS pressure reduction control mode
The control process or valve positions shown in the example relate to the FR brake.
The ESP control module introduces the pressure reduction phase from the slip values of the braked wheels.
The pressure reduction phase is introduced by actuating (opening) the solenoid valve (y9). The solenoid valve (y8) remains actuated (closed) in this control phase. 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 the brake fluid back to the master brake cylinder against the existing pressure.
There is a silencer (10) for each brake circuit to damp delivery noise.

b Brake pressure
e Reduced pressure
 
    P42.45-0262-76

  ESP control module, location/task/function   GF42.45-P-4500B
  Traction systems hydraulic unit, location/task/design/function   GF42.50-P-4000B