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

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





ABS closed-loop operation, pressure buildup (shown on model 230)
Each ABS control phase begins with normal application of the brakes when the driver presses the brake pedal. The SBC control unit calculates the brake pressure and begins the control phase.

The ESP, SPS [PML] and BAS control unit (N47-5) detects the brake application via signals (pedal value sensor, wheel speeds, brake pressure) from the SBC control unit.

The left and right front separation valves (y1 and y2) are closed at the start of the braking application. They only remain closed during the control and are otherwise (de-energized).

All outlet control valves (y7, y9, y11, y13) are also closed. All inlet control valves (y6, y8, y10, y12) are opened. The front axle and rear axle balance valves (y3 and y4) remain open.

The pressure from the pressure reservoir (3) can now be increased at the brake calipers of the front axle via the front left and right dividing pistons (7 and 8). The pressure is increased directly at the rear axle.





ABS closed-loop operation pressure holding
The control process shown in the example and the valve positions refer to the FR brake.

If a wheel shows a tendency to lock during the brake application, the ABS prevents a further buildup of pressure. The ESP, SPS [PML] and BAS control unit (N47-5) introduces the pressure holding phase from the slip values of the braked wheels.

The pressure holding phase is introduced by actuating the solenoid valves (y8 and y3). In this control phase the solenoid valves (y3, y8 and y9) remain closed; the pressure in the FR brake caliper remains constant as a result.





ABS closed-loop operation, depressurization
The control process shown in the example and the valve positions refer to the FR brake.

The ESP, SPS [PML] and BAS control unit (N47-5) 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.

Brake fluid flows back into the reservoir via the return line during the pressure reduction phase.