ETS Control Function

ETS Control Mode Pressure Increase





The control process or valve positions shown in the example relate to the VR brake.

If one of the drive wheels tends towards spinning when starting of for accelerating, the control module introduces the Electronic Traction Support (ETS) pressure increase control mode.

At the start of the ETS control the switchover solenoid valves (y18, y19) are switched (closed) into the "shut-off" position and the self-priming high pressure/return pumps (p1, p2) are actuated.

The inlet solenoid valve (y22) is actuated differently depending on the pressure in the brake calipers:

A When a calculated pressure of greater than 60 bar is reached in the brake calipers, the inlet solenoid valve (y22) is only opened during the pressure increase phases. The self-priming high pressure/return pump (p1) draws in brake fluid from the reservoir via the inlet solenoid valve (y22) and via the brake master cylinder.

B When a calculated pressure of greater than 60 bar is reached in one of the brake calipers, the inlet solenoid valve (y22) remains open continuously during the entire control process. The pressure to the brake caliper VR (5a) is built up by the self priming high-pressure/return pump (p1) via the solenoid valve (y8; not actuated - open).

The pressure limiting valve integrated in the switchover solenoid valve (y18) is used for high-pressure limiting (approx. 170 bar).

ETS Control Mode Pressure Holding





The control process or valve positions shown in the example relate to the VR brake when a calculated brake pressure of> 60 bar is reached in the brake caliper.

If a major brake intervention is no longer required to prevent drive slip, the ETS control mode pressure holding starts. When a calculated pressure of greater than 60 bar is reached in the brake caliper, the inlet solenoid valve (y22) is closed. As a result the brake pressure in the caliper cannot be increased by the high pressure/return pump (p1).

When a calculated pressure of greater than 60 bar is reached in the brake caliper, the pressure holding phase is introduced by valves actuation (closure) of the solenoid valve (y8). The solenoid (y8 and y9) are closed in this control phase, and as a result the pressure in the brake caliper remains constant. The self-priming high pressure/return pump (p1) is also actuated in this control phase and the switchover solenoid valves (y18 and y19) closed. The pressure occurring between the high pressure/return pump (p1) and the switchover solenoid valve (y18) is reduced by the pressure limiting valve integrated in the switchover solenoid valve.

ETS Control Mode Pressure Reduction





The control process or valve positions shown in the example relate to the VR brake when a calculated brake pressure of greater than 60 bar is reached in the brake caliper.

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

When a calculated pressure of greater than 60 bar is reached in the brake caliper the pressure reduction phase is introduced by actuation (opening) of the solenoid valve. Solenoid valve (y8) remains closed. The brake fluid flowing back flows partly through the inlet solenoid valve (y22), partly via the high pressure/return pump (p1) and the pressure limiting valve integrated in the switchover solenoid valve (y18) via the brake master cylinder back to the brake fluid reservoir.

When a calculated pressure of 60 or less bar is reached in the brake caliper the pressure reduction phase is introduced by opening of the switchover solenoid valve (y18). Solenoid valve (y8) remains open and solenoid valve (y9) remains closed.

The brake fluid flowing back flows via the high pressure/return pump (p1) through the switchover solenoid valve (y18) via the brake master cylinder back to the brake fluid reservoir

The self-priming high pressure/return pump (p1) is also actuated in these control phases

ETS Control Mode Pressure Increase At A Rear Wheel (HR)






ETS Control Mode Pressure Increase At Both Rear Wheels






ETS Control Mode Pressure Increase At Both Rear Wheels And One Front Wheel (VL)






ETS Control Mode Pressure Increase HL And Pressure Holding HR And VL





(Example: Calculated brake pressure in the A brake caliper less than 60 bar)

ETS Control Mode Pressure Increase HL, Pressure Reduction HR And Pressure Holding VL





(Example: Calculated brake pressure in brake caliper less than 60 bar)