Pressure decreasing phase

Pressure decreasing phase

The electronic control unit measures the tendency of the wheel to lock and the ABS device comes into operation.

The solenoid valve (4) is energised by a 5 Amp current and the connection between the brake pump and the right rear brake caliper is cut off, while the connection between the brake caliper and the recovery pump (5) is opened, being activated at the same time as the solenoid valve (4).

In this way the pressure of the brake fluid in the right rear brake caliper and in the piston chamber (11) connected to it, decreases. The subtracted brake fluid is recirculated into the main circuit through the recovery pump (5). This is the origin of the intermittent hydraulic pulsations which can be perceived by the driver through the brake pedal.

The accumulator (6) in the circuit stores the part of the brake fluid subtracted from the brake caliper and at the same time acts as a damping chamber for the pressure peaks during the recovery phase.

The lack of balance between the forces acting on the piston (11), causes it and the rod (12) to move. Through piston (10) the rod moves piston (11) causing valve (14) to close.

The result is the gradual decrease of the pressure in the left rear brake caliper caused by the increased volume in the piston chamber (10).

The balance of the forces acting on pistons (10) and (11) will be reached when the braking pressures in the rear brake calipers reach the same value.

• A. Electronic control unit
• B. Brake pump outlet hose
• C. Brake pump outlet hose

1. Brake pump
2. Solenoid valve for front wheel brake circuit
3. Solenoid valve for front wheel brake circuit
4. Solenoid valve for rear wheel brake circuit
5. Electric recovery pump
6. Accumulator
7. Revolution sensors and phonic wheels for front wheels
8. Revolution sensors and phonic wheels for rear wheels
9. Sequential hydraulic valve
10. Piston
11. Piston
12. Stiff rod connecting pistons
13. Spring
14. Valve