1 - front wheel
2 - electronic sensor for determining the number of wheel revolutions
3 - double-circuit pump with electric motor
4 - hydraulic valves
5 - compensation tank
6 - master brake cylinder
7 - vacuum controlled brake booster
8 - rear wheel
9 - electronic sensor for determining the number of wheel revolutions
10 - pressure distribution valve, depending on the load
11 - electronic control device
12 - brake pedal stroke sensor
Usually, if the car is equipped with an anti-lock device, disc brakes are mounted on its rear axle. However, in the embodiment «Golf» this device (depending on the model) can also function when drum brakes are placed on the rear axle.
The decisive safety factor provided by the anti-lock device is its ability to prevent the wheels from locking when the vehicle is braked hard; thanks to this, the possibility of further driving in this situation is guaranteed. Even with emergency braking, there is still a chance that the obstacle can be driven around while maintaining control of the rear wheels. But we must never forget that an anti-lock device cannot perform a miracle. If the physical capabilities of the device are exceeded, i.e. speed is too high, the vehicle with the anti-lock device will also start to skid.
The speed of rotation of each of the wheels is independently controlled by four electronic sensors that record the readings of the number of revolutions of the wheels. The sensors are mounted on the stub axle or rear wheel hub support and are actually «are in control» for the number of revolutions of the gear rims located at the end of the axle. In the figure, where the sensors and gear rims sit in versions with disc and drum brakes, respectively.
Shows what a front-mounted disc brake looks like when an anti-lock device is built in. The computer captures these signals indicating the number of revolutions and evaluates any deviations in relation to pre-programmed values. Thanks to this process, in combination with a hydraulic device, the braking pressure on the corresponding wheel can be increased or decreased by 4-10 times per second, which is much faster than can be achieved with «intermittent» pressing the brake pedal. In addition, it is possible to brake control of each wheel individually, and not all four wheels at the same time, which occurs when the brake pedal is depressed in vehicles that do not have an anti-lock device.
Two hydraulic valves distribute the necessary pressure to the front wheel brakes exactly according to road conditions. Another control valve controls the rear wheel brakes. In this case, the electronic control system reacts first to the wheel that is locked first. With optimal braking, you can still control the car.
Since the anti-lock device should provide you with additional security, we do not recommend any other work on it, although some operations will not give you any trouble. However, the workshop will be able to better understand the situation. However, the car is always subjected to some kind of work, which undoubtedly affects the anti-lock device, since even with normal work carried out in the braking system. for example, the removal of air from the system is carried out in various ways. For this reason, when performing any work on the braking system, the following requirements must be taken into account.
Thoroughly clean all connecting elements, as well as the areas around them, before disconnecting them.
Place the dismantled parts on a clean surface and cover with synthetic film or clean paper. Do not use any fibrous cloths for this.
Carefully cover or close the exposed parts of the device if repairs are to be carried out a little later. This is especially important when the car is parked outdoors.
Mount only perfectly clean parts, in no case use parts that have lain for a long time.
With air compressors that can be connected instead of the cigarette lighter, you can always successfully use compressed air to clean parts. Never carry out this operation with open connecting elements of the device.
After switching on the ignition system, the hydraulic pump sets the required working pressure in the device within 60 seconds. The special lighting of the anti-lock device flashes for 2-20 seconds, depending on the amount of pressure in the device. Now the electronic control unit checks the individual components of the anti-lock device. In the event that any deviations are noticed, the braking system will operate like a traditional system without an anti-lock device. In this case, i.e. if the signal light is still on, contact the workshop. Specialists, using the failure diagnostic system, will be able to find a malfunction in the device due to failures in the electronics or hydraulics.
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