Daewoo Nexia

since 1994 of release

Repair and car operation

The modulator of back wheels works similarly except for the following features. Both back wheels cope synchronously and, besides, in a design of the modulator there is no EMK. Synchronous management of braking of back wheels allowed to apply one electromechanical drive instead of two and to simplify ABS design. The principle of "Select Low" which provides a simultaneous rastormazhivaniye of both back wheels at the beginning of blocking of any of them is applied to management of braking of back wheels. This principle provides good cross-section stability of the car when braking. Absence in the modulator of back wheels of EMK is caused by that the contribution of back wheels to efficiency of braking is rather insignificant and at ABS refusal the car can be braked with the set delay by one forward wheels. At refusal of ABS which puts out of action brake contours of back wheels, TEBU establishes the corresponding code of malfunction and includes both signaling devices: yellow "ABS" and red "BRAKE".

ABS starts to work only at the included stoplight after the TEBU microprocessor will find the blocking beginning at least one of car wheels. In this case TEBU carries out by means of the modulator regulation of pressure of brake liquid in a brake contour соответ a stvuyushchy wheel (or wheels) for the purpose of prevention of its blocking and preservation of stability and controllability of the car. Cycles of regulation of pressure repeat several times in a second. It should be noted that the ABS VI system cannot increase pressure of brake liquid in wheel cylinders in comparison with pressure in the main brake cylinder which completely depends on effort on a brake pedal. As a result of application of ABS brake efficiency, and also course controllability and controllability of braking in various road conditions improves. At the beginning of blocking of wheels of TEBU operates turning on of electric motors and EMK of three modulators. At turning on of the modulator of a forward wheel of EMK at the command of TEBU closes section of one through passage of channels, I connect shchy the wheel brake cylinder to the main cylinder (see fig. The modulator of a forward wheel – braking at ABS work). Then TEBU regulates pressure in the isolated contour of a wheel, operating the electric motor of a drive of the piston of the modulator. At turning on of the electric motor the brake spring twists with simultaneous radial compression of rounds and releases a leading gear wheel (see fig. Spring brake). When lowering piston the return valve is closed, completely disconnecting the wheel brake cylinder from the main cylinder. Pressure in the wheel cylinder depends on volume of a nadporshnevy cavity of the modulator. Pressure reduction in a brake contour of a wheel is reached by lowering of the piston of the modulator. For increase in pressure of brake liquid the piston rises up. Movement of the piston is carried out by sharikovintovy transfer and an electromechanical drive of the modulator. If the wheel started to be blocked on a slippery surface (for example, on ice) at small pressure in a brake drive, and then in a phase of a zatormazhivaniye of ABS it is a wheel got on a site of a surface of the road with high factor of coupling, the piston of the modulator will move to extreme top situation and will open the return valve. Thus pressure in the wheel cylinder will be defined by pressure in the main brake cylinder and effort on a brake pedal. The piston will remain in the top situation until pressure of brake liquid does not become sufficient for blocking of a wheel and ABS will not begin a new cycle of regulation. The maximum level of pressure in the wheel cylinder in the course of work of ABS is limited by pressure size in the main brake cylinder. If in the course of car braking at working ABS the driver reduces effort on a brake pedal, the return valve and a part of liquid from the wheel cylinder will open will flow in the main brake cylinder. At ABS shutdown the piston of the modulator comes back to the top situation and EMK (on modulators of forward wheels) opens. After that the Brake system continues to work in the main mode. The modulator of back wheels at inclusion of ABS works similarly except for absent EMK. Synchronous movings of pistons in the course of regulation of pressure of brake liquid are carried out by one electromechanical drive and sharikovintovy transfer. In working cylinders of back wheels identical pressure of brake liquid is supported approximately.

At inclusion of ignition the signaling device of "ABS" which dies away in 3 seconds lights up. ABS is automatically given in a ready state on reaching speed of the car of 8 km/h. Thus pistons move to extreme top situation. Moving of pistons and work of electromechanical drives of modulators can be accompanied by small noise. If the driver presses at this time a brake pedal, it can feel a little push of a pedal. Thus process of reduction of ABS in a ready state will be interrupted.

The standard Brake system is equipped with one red signaling device of "BRAKE". In ABS two signaling devices are used: red "BRAKE" and yellow "ABS".