Brake pedal release

With the car without A.B.S. the driver is able to act intermittently on the brake pedal with a frequency of 2 cycles per second (2 presses and 2 releases). With the A.B.S. system, the cycles increase to 4, 10 per second (depending on grip). Normally operation of the A.B.S. ceases at speeds below 2.75 km/h to allow the wheels lock completely when the car reaches a halt.

NOTA: The recovery pump is of the free piston type with double circuit, driven by an electric motor that turns constantly during the recovery phase. The pistons are not coupled with the electric motor but they are moved by the cam, only upon arrival of the brake fluid. Therefore, the pump can perform only one impelling stroke while suction is not possible owing to the lack of mechanical connection between motor and pump.

Brake pedal release

1. Electronic control unit
2. Low pressure accumulator (reservoir)
3. Recovery pump drive motor
4. Recovery pump
5. High pressure accumulator (damping chamber)
6. Brake control pump
7. Servobrake
8. Fast pressure reduction valve
9. Charge solenoid valve
10. Discharge solenoid valve
11. Brake caliper
12. Revolution sensor
13. Phonic wheel
14. Restrictor

To enable rapid reduction of the pressure on the brake caliper (11) when the brake pedal is released, the system is fitted with a non return valve (8) in parallel with the inlet solenoid valve (9).