Brake Fluid Accumulator: Description and Operation

Accumulator Cross-section:

ACCUMULATOR
The hydraulic accumulator accumulates the hydraulic pressure and make it available to the hydraulic system for the booster and rear wheel brakes.

Owing to the fact that fluids are incompressible they cannot be used for an accumulation of energy. The additional use of compressible nitrogen gas in the hydraulic accumulator enables an energy accumulation. The gas and fluid must be separated by means of a membrane.

The hydraulic accumulator is composed of a reservoir which is divided into two chambers by a membrane (1). The upper chamber (2) is filled with nitrogen gas to an initial pressure of 84 bar. Brake fluid supplied by the pump fills the lower chamber (3).

With an increasing amount of brake fluid the pressure in the system also increases, the nitrogen gas is compressed and the gas pressure is increased i.e. the nitrogen volume becomes smaller. Equally the accumulator volume for the brake fluid increases up to the cut-off pressure of 180 bar. The pressure in the accumulator is maintained by means of a check valve which is integrated in the motor pump unit and is available up to the annular chamber of the control piston in the booster.