VOLKSWAGEN GOLF IV

since 1997 of release

Repair and car operation

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

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

The role of anti-blocking system consists in restriction of the pressure created in hydraulic system of brakes so that the size of sliding 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 (factor of coupling) and load of the car.

In anti-blocking system functions of power supply, a drive of brakes and the vacuum amplifier, and also management of anti-blocking of wheels are carried out. The hydraulic block is established instead of the serial established vacuum amplifier with the built-in main brake cylinder. The ABS installation is possible only at plant when manufacturing the car and cannot be established in addition. 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 in this case is more, when when braking a wheel continue rotation. In addition, even at complete braking the car remains operated. Sensors of turnovers, of one on each wheel, measure speed of rotation of a wheel. On signals from sensors of turns of a wheel in the electronic operating block the average speed approximately corresponding to speed of movement of the car is calculated. Comparing speed of rotation of each separate wheel with the average calculated speed, the electronic block defines a condition of a proskalzyvaniye of a separate wheel and by that establishes, what wheel is in a preblocking condition.

When one of four sensors of speed of rotation will transmit a signal about blocking of the corresponding wheel, immediately the electronic actuation device gives out a signal of closing to the corresponding inlet electromagnetic valve which immediately blocks supply of brake liquid via 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 this brake opens decreases – the wheel is not braked (surplus of brake liquid comes back to 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, and the wheel is again braked.

Such cycle of braking and free rotation of a wheel occurs very quickly (several times in a second) and proceeds to a stop cars or to an otpuskaniye of a pedal of a brake.

This process repeats at sharp braking separately for each wheel until the pedal of a brake will be released or at reduction of speed of the car to 2–3 km/h. The driver defines work of ABS on a pulsation of a pedal of a brake.

The system of an emergency shutdown provides ABS system shutdown at any malfunction or a low voltage in an electric network of the car (below 10В).

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 anti-blocking system. At faulty system ABS of a brake are nevertheless serviceable and function as if this system is not present in the car.