Audi A4

Since 1994 of release

Repair and car operation

The hydraulic module

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

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 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.