ESP control mode
VN 9.060 f. High pressure; g. pre-pressure
The ESP control unit performs a braking control action to regulate the driving stability of the vehicle.
At the start of regulation of the ESP system, the switching solenoid valves (y18, y19) brought into position «blocking» (closing), and the charge/exhaust pump unit is activated (ml). From speed >20 km/h (starting range) activated (opens) BAS solenoid valve (A7/7u1) in the brake booster (A7/7). Atmospheric pressure is applied to the rear side of the diaphragms in the brake booster, which results in a pressure of approx. 5 bar as pre-pressure on the inlet side of the charge/discharge pump unit.
intake solenoid valve (y22) only opens during pressurization. At the same time, a self-priming pressure/discharge pump (p1) through intake solenoid valve (y22) and the brake master cylinder draws brake fluid from the reservoir.
To limit the high pressure in the switching solenoid valve (at 18) integrated pressure reducing valve (about 170 bar).
ESP control mode: pressure maintenance
VN 9.061 A. Suction pipeline; b. brake pressure; g. pre-pressure
The valve adjustment procedure shown in the example applies to the VR brake (front right wheel).
If more intensive braking control action is no longer necessary to stabilize the movement, the pressure maintenance mode is activated as part of the ESP control.
intake solenoid valve (y22) closes.
As a result, the pressurization of the wheel brake by means of the pressure/bleeder pump (p1) impossible.
ESP Control Mode: Pressure Relief
VN 9.062 A. Suction pipeline; e. Reduced pressure
The valve adjustment procedure shown in the example applies to the VR brake (front right wheel).
If the brake pressure required to stabilize the movement is excessively high, then the ESP control mode is activated «pressure reduction».
The pressure reduction process starts when the switching solenoid valve is opened (y18). Solenoid valve (y8) remains open and the solenoid valve (y9) - closed.
The brake fluid flowing back passes through the pressure-discharge pump (p1), via switching solenoid valve (y18) and then through the master brake cylinder into the brake fluid reservoir.
In these control modes, the self-priming pressure/discharge pump (p1) also activated.