Audi A4

Since 1994 of release

Repair and car operation



Audi А4
+ Running gear
+ Regular servicing
+ Engines
+ Turbo-supercharging
+ Exhaust system
+ Cooling system
+ Fuel tank and the fuel pump
+ The air filter and channels всасывания
+ Injection system
+ Coupling
+ Transmission and the main transfer
+ Suspension bracket of wheels and steering
- Brakes
   Independent work on brake system
   So the brake system works
   Check of brakes
   Brake liquid
   Check of level of a brake liquid
   Check of brake system on tightness and presence of damages
   Replacement of a brake liquid
   Disk brakes
   Measurement of a thickness of overlays of forward disk brakes
   Check of a condition of brake disks
   Replacement of overlays of disk brakes
   Back disk brakes
   Measurement of overlays of back disk brakes
   Manual brake
   Check of idling of the lever of a manual brake
   The main brake cylinder
   The brake amplifier
   Check of the brake amplifier
   Works on hydraulics of brake system
   Prorolling of brake system
   The help at malfunctions
   ABS and EDS
   What does ABS?
   Function of separate knots
   Electronic system of distribution of brake effort (EBV)
   Infringements in system ABS work
   Electronic blocking of differential (EDS)
+ Wheels and tyres
+ The electrotechnical equipment
+ Ignition system
+ Illumination
+ The alarm equipment
+ Tools and devices
+ Heating and ventilation
+ Body details
+ Salon
Search of malfunctions
Technical characteristics



Function of separate knots

The hydraulic module

The hydraulic module (1) systems of antiblocking takes places ahead at the left in an impellent compartment. It is connected by the central socket (2) with the management block under a back seat.

It is ahead at the left in an impellent compartment: the module is built in between brake pipelines of the main brake cylinder and the brake tubes conducting to brakes of wheels. According to orders of the electronic block of management pressure in contours of brake system remains or to constants, or goes down, or again raises. But pressure cannot be above what you create, pressing a brake pedal. Pressure is regulated by four quickly switched electromagnetic valves – on one on each wheel.

If electromagnetic valves are disconnected, pressure raises. If the maximum current there is a pressure decline arrives, at an average current strength pressure remains at one level. The particular interest is represented by a phase of removal of pressure: as for pressure decline it is impossible to let out somewhere simply a brake liquid (for this purpose the brake pedal would need to be wrung out completely), arriving here from the main brake cylinder a brake liquid pump out the powerful return pump back to the main brake cylinder. You notice it on behaviour of a pedal of a brake which starts to pulse slightly when the return pump works, i.e. Starts to work ABS. If attentively to listen, noise of the working pump is audible. Special демпферами in the hydraulic module this noise chokes a little.

Gauges of number of turns

Such gauges of number of turns (2) are established on all four wheels in apertures (1) suspension brackets of an axis. Behind them according to frequency of rotation of wheels gear elastic washers rotate.

Only four gauges fix speed of rotation of each wheel and hand over this information in the electronic block of management. On its basis the electronic block of management regulates work of the hydraulic module.

Gauges of number of turns consist of the magnetic core and the coil and are mounted on small distance from a gear disk – a rotor. The rotor – its name speaks for itself – rotates together with a wheel and forces to rotate зубцевидные cambers on its perimetre by the gauge faster or more slowly depending on speed. Each tooth which is passing under the gauge, induces short lifting of pressure in the gauge. In such a way in the gauge the alternating voltage which changes the frequency according to speed of rotation of a wheel is created. The signal arising thus is processed by the electronic block of management as the information on number of turns of a wheel.

In Audi A4 rotors take places on two or on four (quattro) drivers wheels on the external hinge of a power shaft and on naves неdrivers back wheels.

The electronic block of management

The combined block of management (arrow) system of antiblocking and electronic blocking of differential is approximately in the middle of the car under a back seat.

The electronic block of management is under a back seat and processes the information arriving from gauges of number of turns.

Simultaneously it operates the hydraulic module so that wheels were not blocked. Along with processing of signals and the subsequent logic part, the management block still has the blocking scheme. By means of it the device can check, distinguish itself failures and supervise working pressure. If malfunctions are fixed, it switches off ABS and the control bulb in the combined device lights up.