20.1. Features of a design

The working brake system – hydraulic, double-circuit, with pressure regulator, the vacuum amplifier and the sensor of insufficient level of liquid in a tank of the main brake cylinder. One contour is connected with working cylinders of forward and back wheels, other contour – only with working cylinders of forward wheels. In the normal mode (when the system is serviceable) both contours work. At refusal (depressurization) of one of contours of the second provides braking of the car, though with smaller efficiency.

The brake pedal – suspended type, is fixed on one axis with a coupling pedal, rotates in two plastic plugs, is supplied with a returnable spring. Over a pedal the switch of stoplights is located; its contacts become isolated when pressing a pedal. The free wheeling of a pedal of a brake has to make 3–5 mm (adjustment see in the section Removal of the Vacuum Amplifier of Brakes and Adjustment of a Free Wheeling of a Pedal of a Brake).

For decrease in effort to pedals of a brake the vacuum amplifier using depression in an inlet collector of the working engine serves. It is located between a pusher of a pedal and the main brake cylinder and fastens nuts to an arm on a forward board in a motor compartment. The amplifier – non-demountable, at failure he is replaced (the amplifier – from VAZ-2108). The elementary check: on the car with the idle engine it is several times pressed a pedal of a brake and, holding a pedal of pressed, we launch the engine. At the serviceable amplifier after launch of the engine the pedal has to leave forward. Remember that failure or insufficient efficiency of the vacuum amplifier can be caused also by leakage of the hose which is selecting depression from an inlet collector.

The main brake cylinder fastens to the case of the vacuum amplifier on two hairpins. Hoses on which in the cylinder liquid from a brake tank moves are put on unions in the top part of the cylinder. On a tank tags of the maximum and minimum levels of liquid are put, and in a cover the signaling device with the float closing contacts at liquid lowering of the level is mounted. Screws in the lower part of the cylinder limit movement of pistons. Screws are condensed with copper or aluminum laying. In a forward part of the cylinder (on the car course) the cap serving as an emphasis of a returnable spring and also condensed with copper or aluminum laying is screwed. Unions of brake tubes are screwed in openings of the cylinder on each side: in forward openings – the contour bringing liquid to forward wheels in back – to all wheels.

Brake mechanisms of forward wheels – disk, with a three-piston floating bracket. The top piston is given from one contour (together with pistons of working cylinders of back wheels), two lower – from another. The block of cylinders is fixed in a support on two guides and fixed by the sprung clamp. Between the block of cylinders and a support blocks settle down: internal leans on pistons of cylinders, external – on inflow of a support. The support can move in a guide of blocks, being drawn in to it by two sprung levers. The guide of blocks is rigidly attached by two bolts to a rotary fist. From an otvorachivaniye bolts are fixed by edges of the protection cover (they are unbent on the verge of bolts after an inhaling).

Brake disks – pig-iron. The minimum thickness of a disk at wear of 9,5 mm, the most admissible beating (on the largest radius) – 0,15 mm. Minimum admissible thickness of overlays of blocks of forward brakes – 1,5 mm.

Brake mechanisms of back wheels – drum, with two-piston wheel cylinders and automatic adjustment of a gap between blocks and a drum. The device of automatic adjustment of a gap is located in the wheel cylinder and represents two elastic steel cutting rings (on one on each piston) established on pistons with an axial gap of 1,25-1,65 mm.

Elasticity of a ring is picked up so that it was not displaced on a cylinder mirror from effort of coupling springs of blocks (and only from effort of pistons). In process of wear of blocks pistons when braking move rings on cylinders, supporting a constant settlement gap between blocks and a drum. In case of damage of a mirror of pistons because of mechanical impurity in brake fluid or corrosion of a ring and pistons can "sour" in the cylinder, having lost mobility. In this case it is necessary to replace cylinders and brake fluid.

Brake drums – aluminum, with the filled-in pig-iron rings (a working surface). Nominal internal diameter of a drum – 250 mm. The pro-point of drums at wear is allowed. The largest admissible diameter (at wear or after a pro-point) – 251 mm.

The regulator of pressure serves for decrease in brake effort on a back axis that prevents a car drift when braking. It limits pressure in back brake mechanisms depending on the provision of a back part of a body concerning the road: at increase in load of a back axis when coupling of back wheels with the road improves, the regulator provides bigger pressure in wheel cylinders and vice versa, with reduction of loading pressure falls. The regulator fastens two bolts to an arm in the right back part of a body and is given by the elastic lever attached through thirst for a beam of the back bridge. With increase in load of a back axis of the car the elastic lever is also loaded, transferring effort to the regulator piston. When pressing a brake pedal pressure of liquid seeks to put forward the piston outside that is interfered by effort from the lever. When the system equilibrates, the valve located in the regulator isolates back brake cylinders from the main thing brake, without allowing the further growth of brake effort on a back axis. Due to ovality of openings in an arm the regulator can be turned, changing its situation concerning the lever (see Check of working capacity and adjustment of the drive of the regulator of pressure of back brakes). For extension of service life of the regulator in a protective rubber cap put 5–6 g of DT-1 lubricant (or graphite), cover with it an axis through which there passes the lever, and the acting part of the piston. The regulator of pressure is not recommended to be disassembled, at failure it is replaced.

The drive of the parking brake system – mechanical, hummock, on back wheels. It consists of the lever, a forward cable with a carving tip (with the plug and two nuts), an ottyazhny spring, a back cable, its guide, two levers and two expansion levels – on one (one) on each brake mechanism. The drive is adjusted by movement of nuts on a carving tip of a forward cable (after adjustment of a nut kontritsya). The full speed of the lever after adjustment has to correspond to rise on 4–5 teeth on the sector.