The greatest efficiency of braking is reached at the maximum coupling of the tire with the surface of the road. When sliding the tire on a surface in the course of braking the linear speed of a wheel becomes less than the speed of the car. The minimum sliding (0%) is reached at freely sliding wheel, and maximum (100%) — if the wheel is blocked. Optimum efficiency of braking is reached at the sliding equal to 15%. At such size of sliding stability and controllability of the car fully remains.

The anti-blocking system is intended to limit pressure created in hydraulic system of brakes the size of sliding was close to optimum. The principle of action, separate for each wheel, is the basis for work of anti-blocking system. The system is designed to react immediately to each change of coefficient of coupling of a wheel with a surface and loads of the car.

The anti-blocking system interferes with blocking of wheels at sharp braking. Thanks to it the brake way decreases, especially at low coupling with a paving at a rain and snow. Force of adhesion between wheels and the road is more if when braking a wheel continue rotation. Besides, even at full braking the car remains operated. RPM meters — on one on each wheel — measure the speed of rotation of wheels. On signals, postupayemy from sensors, the electronic control unit calculates the average speed which is approximately corresponding to the speed of the movement of the car. Comparing the speed of rotation of each separate wheel with the average calculated speed, the electronic block defines coefficient of slipping of each separate wheel and by that defines what wheel is in a preblocking state.

When one of four sensors of speed of rotation of a wheel transmits a signal of blocking of the corresponding wheel, the electronic actuation device will give a closing signal to the corresponding inlet electromagnetic valve which will immediately block supply of brake fluid via the brake pipeline to a brake of this wheel and force of braking will remain to a constant. If sliding after all continues, the final valve will open and pressure in hydraulic system of this brake mechanism will decrease. As soon as the wheel starts over again rotating, inlet will open and the final valve will be closed. Pressure will increase in a contour, and the wheel will begin braking again.

The cycle of braking and free rotation of a wheel is carried out for very short period (several times in a second) and repeats to a full stop of the car or to a brake pedal otpuskaniye. Action of this process extends to each separate wheel.

The system of emergency shutdown provides shutdown of the ABS system at any malfunction or at low (lower than 10 V) tension in onboard network of the car.

The electronic actuation device performs also diagnostic function, warning the driver fire of a control lamp about registration of malfunction of electric chains or elements of anti-blocking system. At the faulty ABS system of a brake continue to work in the usual mode (without anti-blocking).

Fire of a control lamp of ABS during the movement signals about malfunction and shutdown of system. In this case it is necessary to arrive as follows:

stop the car, switch off and again start the engine;

check tension of the rechargeable battery. In case tension lower than 10,5 In, the rechargeable battery it is required to load;

PREVENTION If the control lamp of ABS burns at the beginning of a trip, and then dies away, it means that tension was below an admissible limit for ABS work, but then raised as a result of operation of the generator.

check whether conclusions of the rechargeable battery were oxidized;

you will hang out the car, remove wheels and check serviceability of an electrical wiring of sensors of speed of rotation of wheels;

if malfunction is not revealed, then a further inspection of anti-blocking system of brakes needs to be carried out at specialized service station.

NOTE Since June, 1988 the ABS control unit has the module which is defining and memorable the defects arising in use. At service station information is read out from the block of memory and defect is eliminated.