GF42.45-P-3700D ESP Control Mode, Function

GF42.45-P-3700D ESP control mode, function





ESP control mode, pressure build-up
The control procedure and value positions illustrated in the example refer to the FR brake.

A brake intervention to stabilize the vehicle is introduced by the []front right[] wheel by the ESP and BAS control unit (N47-5)

In normal operation at the start of the ESP control the right front solenoid valve (pressure hold) (y8) is opened, the front axle switchover solenoid valve (y18) is switched into the "Lock position" (closed) and the front axle pump (p1) is actuated.

The front axle inlet solenoid valve (y22) is only opened during the pressure buildup phases.

In the process the front axle pump VA (p1) draws brake fluid out of the reservoir via the inlet solenoid valve (y22) and via the master brake cylinder and prepares high pressure for introduction into the corresponding wheel brake.

If extremely rapid stabilizing action is required, the pressure buildup phase is boosted by active actuation of the Brake Assist system. This directs atmospheric pressure against the rear of the diaphragms in the brake booster, producing a pressure of approx. 5 bar in the brake circuits.

The pilot pressure thus produced is lead via the check valve (7) from the front axle switchover solenoid valve (y18) into the active brake circuit to the right front brake caliper until the pressure downstream of the check valve (7) is higher than the primary pressure.

At the same time the pilot pressure is applied via the front axle inlet solenoid valve VA (y22) to the intake side of the front axle pump (p1) and improves its fill level and delivery rate. The pilot pressure is kept away from the inactive wheel brakes by closing the solenoid valves (y6, y10, y12).

The pressure limiting valve integrated in the rear axle switchover solenoid valve (y19) serves high-pressure limitation. The valve opens at pressure valves > 150 bar.





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

When no more severe brake intervention is required to stabilize the vehicle, the ESP pressure hold control mode commences. The front axle inlet solenoid valve (y22) and right front solenoid valve (pressure hold) (y8). As a result the pressure in the brake caliper cannot be increased via the front axle pump (p1).





ESP control mode, pressure reduction The control sequence and valve positions described in the example refer to the right front brake.

If the brake pressure required to stabilize the vehicle is too high, the ESP pressure reduction control mode commences.

The pressure reduction phase is introduced by the opening of the right front solenoid valve (pressure release) (y9). The right front solenoid valve (pressure hold) (y8) remains closed.

The brake fluid flowing back returns via the front axle pump (p1) through the pressure limiting valve integrated in the front axle switchover solenoid valve (y18) via the master brake cylinder to the brake fluid reservoir.

The rear axle pump (p2) is actuated pulsed during all control phases (depending on the requirement)..

Various damping components (12, 13, 14) are installed to further reduce noise levels.