Increase pressure phase (Brakes)

Increase pressure phase

1. Master cylinder
2. Hydraulic modulator
3. Piston
4. Cut – off valve
5. Wheel Caliper
6. Speed sensors
7. ECU
8. Solenoid valve
9. Modulator reservoir
10. Pump
11. Accumulator
12. Pressure switch

With the vehicle in motion, the ECU receives signals from the four speed sensors. From these signals the ECU can determine the approximate speed of the vehicle. The ECU uses this speed as a reference when evaluating the deceleration of each wheel.

The reference speed is continually calculated, even during braking. If one or more of the wheels are decelerating faster than the others, indicating a wheel is near the point of locking, the anti – lock sequence will be initiated.

In the increase pressure phase the ABS system is at rest with the modulator cut – off valve in the open position. Hydraulic pressure can be transmitted from the master cylinder to the brake caliper via chambers A and B of the modulator. The solenoid valve in its normal position connects chamber C of the modulator to the pump reservoir. The fluid in chamber C is therefore at atmospheric pressure and has no effect on the operation of the modulator.