GF42.45-P-3000D ABS Closed-Loop Operation Function

GF42.45-P-3000D ABS closed-loop operation function





Brake application in normal operation ABS control mode - build up pressure
Each ABS control phase begins with normal application of the brakes when the driver presses the brake pedal.

The ESP control unit detects that the brakes have been applied by means of the reduced wheel speeds.

The brake pressure is built up via the two change-over solenoid valves (y18 and y19) and the solenoid valves (y6, y8, y10 and y12).

This pressure build-up phase can occur separately at each wheel during the ABS control mode.

With normal brake application, pressure is built up via the same solenoid valves.





ABS control mode - hold pressure
The control procedure and value positions illustrated in the example refer to the FR brake.

If one wheel begins to lock during the braking procedure, the ABS prevents additional pressure build up. The ESP control unit initiates the pressure holding phase using the slip values of the braked wheels.

The pressure holding phase is initiated by controlling the solenoid valve (y8). In this control phase, the solenoid valves (y8 and y9) remain closed. The pressure in the FR brake caliper therefore remains constant.





ABS control mode - reduce pressure
The control procedure and value positions illustrated in the example refer to the FR brake.

The ESP control unit initiates the pressure reducing phase using the slip values of the braked wheels.

The pressure reducing phase is initiated by opening the solenoid valve (y9). Solenoid valve (y8) remains closed during this control phase.

During the pressure reduction phase brake fluid flows back into the front axle pump (p1) via the accumulator (11).

From there the brake fluid is delivered back into the master brake cylinder against the pressure prevailing in the front axle circuit.

Each brake circuit has a muffler (12) to dampen the pumping sound.