Valve block, function: Notes
The valve block, which is an integral part of the hydraulic unit, modulates the brake pressure to the calipers when ABS and TCS braking is activated.
The valve block contains 12 solenoid valves: four inlet valves, four outlet valves, two pressure increase valves and two pressure reducing valves. These are arranged as follows: one inlet and one outlet valve for each of the four wheels and one pressure increase and one pressure reducing valve for each of the front wheels. The pressure increase and pressure reducing valves are activated only in TCS mode and are described in.
In the rest position, the inlet valve is open and the outlet valve closed. During ABS control the inlet valve is closed to maintain a constant pressure. The outlet valve opens at the same time as the return pump starts.
The valve block incorporates an accumulator chamber and a pressure chamber for each brake circuit. The accumulator chamber, which is located between the outlet valve and the return pump, accumulates the brake fluid until the return pump starts.
The function of the pressure chamber, which is located between the return pump and master cylinder, is to dampen both noise and pressure fluctuations when the return pump is operating (ABS mode).