ASR V/ETS Control Functions

ASR or ETS Control Mode - Pressure Build-Up





If one or both drive wheels tends to spin when starting off or accelerating, the control module introduces the ASR or ETS control mode,

At the start of ASR or ETS control the switchover solenoid valve (y5) switches into "locking position" (closed) and the self-priming high-pressure pump/return pump (p1) is actuated.

Bosch Version:
The intake solenoid valve (y15) is actuated differently depending on the pressure in the rear axle brake calipers:

A When a calculated pressure 0f 60 or less bar is reached in the rear axle brake calipers the intake solenoid valve (y15) is only opened during the pressure build-up phases, The self-priming high-pressure pump/return pump (p1) draws in brake fluid from the reservoir via the intake solenoid valve (y15) and via the master brake cylinder.

B When a calculated pressure of greater than 60 bar is reached in one of the rear axle brake calipers, the intake solenoid valve (y15) remains open continuously during the entire control. The pressure to the rear axle brake calipers is built up by the self priming high-pressure pump/return pump (p1) via the solenoid valves (y10, y12; not actuated - open).

Teves version:
The inlet solenoid valve (y15) is continuously open. The pressure to the rear axle brake calipers is build up via the self-priming high-pressure/return pump (p1) via the solenoid valves (y10, y 12; not actuated - open).

The pressure limiting valve integrated in the switchover solenoid valve (y5) is used for high-pressure limiting (approx. 160 bar). The diaphragm discharge damper (12) is used to reduce noise.

ASR or ETS Control Mode - Pressure Holding





If a major brake intervention is no longer required to prevent the drive slip, the ASR or ETS control mode pressure holding starts. The pressure holding phase is introduced by actuating (closing) the solenoid valves (y1O and y12). The intake solenoid valve (y15) is closed below a calculated pressure of 60 bar in both rear axle brake calipers (Bosch only). In this control phase the solenoid valves (y1O to y13) are closed and thus the pressure in the brake calipers remains constant. The self-priming high-pressure pump/return pump (p1) is also actuated in this control phase and the switchover solenoid valve (y5) is closed. The pressure occurring between the high-pressure pump/return pump (p1) and the switchover solenoid valve (y5) is reduced via the pressure limiting valve integrated in the switchover solenoid valve.

ASR or ETS Control Mode - Pressure Reduction





If the brake pressure to prevent acceleration slip is too high, the ASR or ETS control mode pressure reduction starts.

The pressure reduction phase is introduced by the actuation (opening) of the solenoid valves (y11 and y13). The solenoid valves (y1O and y12) remain closed.
The inlet solenoid valve is closed at a calculated pressure of less than 60 bar in the rear axle brake calipers (Bosch only).
The self-priming high pressure/return pump (p1) is also actuated in this control phase and the switchover solenoid valve (y5) closed.
The brake fluid flowing back flows partly through the inlet solenoid valve (y15) and partly via the self-priming high-pressure/return pump (p1) and the pressure limiting valve integrated in the switchover solenoid valve (y5) via the brake master cylinder back to the brake fluid reservoir.
At the end of the pressure reduction phase a sudden release of the of the system pressure (approx. 170 bar) existing between the self-priming high pressure,return pump (p1), the switchover solenoid valve (y5) and the solenoid valves (y1O and y12) is prevented by a cycled actuation of the switchover solenoid valve (y5) and the associated noise is reduced.