Ford Sierra

3.1.4.10.5. Antiblocking system

THE GENERAL DATA

Action principle

Efficiency of braking the greatest, when coupling of the tyre with a surface of road the maximum. In the course of braking the tyre slides on a surface and district speed of a wheel becomes less speeds of the car.

Sliding minimum (0 %) when the wheel slides freely, and maximum (100 %) when the wheel is blocked. Peak efficiency of braking is reached, when sliding makes 15 %. This size also allows to keep stability and controllability of the car.

The role of antiblocking system consists in restriction of the pressure created in hydraulic system of brakes so that the sliding size was kept about optimum size (15 %). Action of this system should be immediate and separate for each wheel. The system should answer immediately each change of a surface (coupling factor) and loading on the car.

Design

The antiblocking system (ABS) Teves contains four gauges of speed of rotation of wheels, hydraulic knot of management and the electronic actuation device.

Four gauges (at each wheel of the car) transmit the signals informing on speed of rotation of each wheel of the car in the electronic actuation device.

The electronic actuation device located on the right side under the forward panel, on the basis of the received information on unequal speed of rotation of separate wheels (or about them заблокировании) transfers a command of reduction of force of braking in hydraulic knot of management (the pressure submitted to a support of a brake) of a wheel, which beginning to test excessive sliding. The electronic actuation device carries out also autodiagnostic function, warning the driver fire of a control bulb about registration of malfunction of electric chains or elements of antiblocking system. At faulty system ABS of a brake nevertheless are serviceable and function as if this system is not present in the car. It is unique a control bulb warns the driver that system ABS does not correct its errors.

The hydraulic knot of management contains the main brake cylinder of type a tandem which operates forward brakes, and the hydraulic auxiliary device which operates back brakes. The hydraulic auxiliary device contains six electromagnetic valves, operated the electronic actuation device, regulating pressure in brakes of separate wheels, and consequently also force of braking. Three inlet electromagnetic valves during normal braking (without sliding) remain opened, and three final valves – closed. They are located in contours of the right forward brake, the left forward brake and back brakes.

Functioning

When one of four gauges of speed of rotation will transmit a signal about blocking of a corresponding wheel, immediately the electronic actuation device gives out a closing signal to corresponding inlet electromagnetic valve which immediately blocks giving of a brake liquid through the brake pipeline to a brake of this wheel – force of braking remains to a constant. If nevertheless sliding proceeds, the final valve and pressure in hydraulic system of the given brake opens decreases – the wheel is not braked (surplus of a brake liquid comes back in a tank). As soon as the wheel again will start to rotate, at once there is an opening of the inlet valve and closing of the final valve. Pressure increases in a contour also a wheel is again braked.

Such cycle of braking and free rotation of a wheel occurs very quickly (some times in a second) and proceeds to a stop cars or to release brake pedals.

The antiblocking system (ABS) operates at speed of movement more than 7 km/h.