ETS Control Mode, Function
ETS Control Mode, Function
ETS control mode - pressure build-up
The control process or valve positions shown in the example relate to the FR brake.
If one or more drive wheels tends to spin when starting off or accelerating, the control module introduces the control mode ETS pressure build-up.
At the start of the ETS control, the switchover solenoid valve (y25) and the left rear solenoid valve, pressure holding (y10) is closed and the self-priming high-pressure/return pump (p1) is actuated. The inlet solenoid valve (y27) is actuated depending on the pressure in the brake calipers:
A At a calculated pressure of > 60 bar in the brake calipers the inlet solenoid valve (y27) is only opened during the pressure build-up phases. The self-priming high-pressure/return pump (p1) draws brake fluid out of the reservoir via the Inlet solenoid valve (y27) and via the master brake cylinder.
B At a calculated pressure of > 60 bar in one brake caliper the inlet solenoid valve (y27) Is also opened during the pressure holding phase.
The pressure at the brake caliper is built up by the self-priming high-pressure/return pump (p2) via the solenoid valve (y8; not actuated - open).
The pressure limiting valve integrated in the switchover solenoid valve (y25) serves to limit high-pressure (approx. 150 bar).
ETS control mode - pressure holding
The control process or valve positions shown in the example relate to the FR brake.
If strong brake intervention is no longer required to prevent drive slip, the ETS control mode pressure holding begins.
The pressure holding phase is introduced by actuating (closing) the solenoid valve (y8). The Inlet solenoid valve (y27) is closed below a calculated pressure of 60 bar in one brake caliper. In this control phase the solenoid valve (y8) is closed and as a result the pressure in the FR brake caliper remains constant.
The self-priming high-pressure/return pump (p2) is also actuated and the switchover solenoid valve (y25) is closed in this control phase. With regulations of > 60 bar brake caliper pressure, the pressure occurring between the high-pressure/return pump (p2) and switchover solenoid valve (y25) is reduced via the pressure limiting valve integrated In the switchover solenoid valve.
ETS control mode - pressure build-up
The control process or valve positions shown in the example relate to the FR brake.
If the brake pressure required to prevent drive slip is too high, the ETS control mode pressure reduction starts.
The pressure reduction phase is introduced by actuating (opening) the solenoid valve (y9). The solenoid valve (y8) remains closed. The inlet solenoid valve is closed at a calculated pressure of < 60 bar in the brake calipers.
The self-priming high-pressure/return pump (p2) is also actuated and the switchover solenoid valve (y25) is closed in this control phase.
The returning brake fluid flows back to the brake fluid reservoir via the self-priming high-pressure/return pump (p2) and the pressure limiting valve integrated in the switchover solenoid valve (y25) via the master brake cylinder.
At the end of the pressure reduction phase, after the pump (p2) is switched off, the system pressure (approx. 150 bar) occurring between the self-priming high-pressure/return pump (p2), switchover solenoid valve (y25) and solenoid valve (y8) is first led into both brake calipers of the circuit. A sudden relief of system pressure in the tandem brake master cylinder is thus avoided and the associated noise is reduced.