ASR V/ETS Hydraulic Unit

Location





In left of engine compartment.

Task
The ASR V/ETS hydraulic unit (A7/3) performs the control functions of the brake moment control circuit.

Design/Function

Part 1 Of 2:

Part 2 Of 2:

The ABS and ASR or ETS switching components are combined in the ASR/ETS/ESP hydraulic unit (A7/3).

For control a 2/2-way valve for pressure build-up/holding or pressure holding/reducing function are used for each wheel. The self-priming high-pressure/return pump (p1) integrated in the hydraulic unit (A7/3) is used for the ASR/ETS pressure supply. The return pump (p2) which is also integrated is used for return during ABS controls. The suction solenoid valve (y15) on the Bosch version and the intake valve (15) on the Teves version is located in the suction line of the self-priming high-pressure/return pump).

At a calculated pressure of 60 or less bar in the rear axle brake calipers, the suction solenoid valve (y15, Bosch version) is opened for the duration of the actuation of the solenoid valves (y10 and y12) only during the ASR or ETS pressure build-up phase. At a calculated pressure of greater than 60 bar in one of the rear axle brake calipers, the suction solenoid valve (y15) remains permanently open during ASR or ETS control. On the Teves version the suction valve (15) remains open in each case, even if it is applied with a pressure of greater than 0.6 bar via the brake pedal.

The switchover solenoid valve (y5) shuts off the rear axle circuit to the master brake cylinder during ASR control. At the same time it is designed as a pressure limiting valve and opens at approx. 160 bar. The pulsating brake fluid being discharged is silenced by a diaphragm discharge silencer (12) and returned to the master brake cylinder.

Each brake circuit has a silencer (10) to silence the delivery noise. The low pressure accumulator receives the fluid during the ABS/ETS/ASR pressure reducing phase and releases it to the high-pressure/return pump.