Design features of the brake system (Kalina 1118)

The vehicles use a service brake system with diagonally divided circuits, which significantly increases the safety of driving the vehicle. One circuit of the hydraulic brake drive ensures the operation of the right front and left rear brake mechanisms, the other - the left front and right rear.

If one of the circuits of the service brake system fails, the second circuit is used, ensuring that the vehicle stops with sufficient efficiency.

The hydraulic drive includes a vacuum booster and a dual-circuit rear brake pressure regulator.

The parking brake system has a drive to the brake mechanisms of the rear wheels.

Vacuum brake booster (figure 8.1) the diaphragm type operates on the principle of pressure difference in the vacuum and atmospheric chambers, as a result of which additional force is created on the piston of the main brake cylinder when the brake pedal is pressed. The vacuum chamber is connected to the engine fuel system receiver through a hose and a check valve, and the atmospheric chamber is connected to the atmosphere through a filter at the moment the brake pedal is pressed. When the brake pedal is released, the vacuum and atmospheric chambers communicate with each other through a special valve.

Brake pressure regulator regulates the pressure in the hydraulic drive of the rear wheel brake mechanisms depending on the load on the rear axle of the vehicle. The brake pressure regulator is included in both circuits of the brake system, and through it the brake fluid is supplied to both rear brake mechanisms.



Brake pressure regulator 1 (figure 8.2) attached to bracket 9 by two bolts 2 and 16. Front bolt 2 simultaneously fastens fork bracket 3 of lever 5 of brake pressure regulator drive. On the finger of this bracket, a double-arm lever 5 is pivotally attached by pin 4. Its upper arm is connected to an elastic lever 10, the other end of which is pivotally connected to the bracket of the rear suspension lever via an earring 11.

Bracket 3 together with lever 5 can be moved relative to the brake pressure regulator due to the oval holes for the mounting bolt. In this way, the force with which lever 5 acts on the brake pressure regulator piston is regulated.

The brake pressure regulator has four chambers: A and D (figure 8.3) connected to the master brake cylinder, IN - with the left one, WITH - with the right wheel cylinder of the rear brakes.

Original posted on the website LADAMAN

In the initial position of the brake pedal, piston 2 is pressed by lever 5 (see figure 8.2) through the leaf spring 7 to the pusher 20 (see figure 8.3), which, under the action of this force, is pressed against the seat 14 of the valve 18. In this case, the valve 18 is pressed away from the seat and a gap is formed N, and also a gap TO between the piston head and the seal 21. Through these gaps the chambers A and D communicate with cameras IN and WITH.

When you press the brake pedal, brake fluid flows through the gaps TO and N, as well as cameras IN and WITH enters the wheel cylinders of the brake mechanisms. As the brake fluid pressure increases, the force on the piston increases, tending to push it out of the housing. When the force from the brake fluid pressure exceeds the force from the elastic lever, the piston begins to move out of the housing, and after it, under the action of springs 12 and 17, the pusher 20 moves together with the sleeve 19 and rings 10. The gap M increases, and the gaps N and TO are decreasing. When the gap N will be selected completely and valve 18 will isolate the chamber D from the camera WITH, the pusher 20 together with the parts located on it will stop moving after the piston. Now the pressure in the chamber WITH will vary depending on the pressure in the chamber IN. As the force on the brake pedal increases further, the pressure in the chambers D, IN and A increases, piston 2 continues to move out of the housing, and sleeve 19 together with sealing rings 10 and plate 11 under increasing pressure in the chamber IN shifts towards plug 16. Gap M begins to decrease. By reducing the volume of the chamber WITH the pressure in it, and therefore in the brake drive, increases and will be practically equal to the pressure in the chamber IN. When the gap TO will become equal to zero, the pressure in the chamber IN, and therefore in the chamber WITH will increase to a lesser extent than the pressure in the chamber A, due to the throttling of the brake fluid between the piston head and the seal 21. The relationship between the pressure values in the chambers IN and A is determined by the ratio of the difference between the areas of the head and the piston rod to the area of the head. As the vehicle load increases, the elastic lever 10 is loaded more and the force from the lever 5 on the piston increases, i.e. the moment of contact between the piston head and the seal 21 is achieved with greater pressure in the main brake cylinder. Thus, the effectiveness of the rear brakes increases with increasing load.



In case of failure of the brake circuit, the left front - right rear sealing rings 10 and bushing 19 are under pressure of the fluid in the chamber IN will shift towards plug 16 until plate 11 stops in seat 14. The pressure in the rear brake will be regulated by the part of the brake regulator, which includes piston 2 with seal 21 and bushing 7. The operation of this part of the brake regulator in the event of failure of the named circuit is similar to the operation with a serviceable system. The nature of the pressure change at the regulator outlet is the same as with a functioning brake system.

If the right front - left rear brake circuit fails, under the pressure of the brake fluid, the pusher 20 with the sleeve 19 and sealing rings 10 moves towards the piston, pushing it out of the housing. Gap M increases, and the gap N decreases. When valve 18 touches seat 14, the pressure in the chamber increases WITH stops, i.e. the brake pressure regulator in this case works as a pressure limiter. However, the achieved pressure value is sufficient for reliable operation of the rear brake.

In the housing 1 there is a hole closed by a plug 24. Leakage of brake fluid from under the plug when it is squeezed out indicates a leak in the rings 10.

Master brake cylinder (figure 8.4) two-section, with sequential arrangement of pistons. A reservoir is attached to the body of the main brake cylinder, in the filler neck of which a brake fluid emergency level sensor is installed.





Front wheel brake mechanism disc, with automatic adjustment of the gap between the brake pads and the brake disc, with a floating caliper and a brake pad wear sensor. The bracket is formed by the brake caliper 3 (figure 8.5) and wheel cylinder 5, which are tightened with bolts. The movable bracket is attached with bolts to the pins 10 installed in the holes of the guide 2 of the brake shoes. Lubricant is placed in these holes, and rubber covers 9 are installed between the pins and the brake shoe guide. Brake shoes 4 are pressed against the guide grooves by springs, of which the inner one is equipped with a brake shoe lining wear sensor 7.



A piston 6 with a sealing ring 8 is installed in the cavity of the brake cylinder 5. Due to the elasticity of this ring, an optimal gap is maintained between the brake pads and the brake disc. Rear wheel brake mechanism (figure 8.6) drum, with automatic adjustment of the gap between the pads and the drum. The automatic clearance adjustment device is located in the wheel brake cylinder.





Its main element is a split thrust ring 9 (figure 8.7), installed on piston 4 between the flange of stop screw 10 and two crackers 8 with a gap of 1.25-1.65 mm.

The thrust rings 9 are inserted into the brake cylinder with an interference fit that ensures a ring shear force along the cylinder surface of at least 343 N (35 kgf), which exceeds the force on the piston from the tension springs 3 and 7 (see figure 8.6) brake pads.

When the gap of 1.25-1.65 mm is completely selected due to wear of the brake linings, the flange on the stop screw 10 (see figure 8.7) will be pressed against the flange of ring 9, as a result of which the thrust ring will move after the piston by the amount of wear. When braking stops, the pistons are moved by the force of the tension springs until the crackers stop against the flange of the thrust ring. This automatically maintains the optimum clearance between the brake shoes and the brake drum.



Parking brake system with mechanical drive acts on the brake mechanisms of the rear wheels. The parking brake drive consists of a lever 2 (figure 8.8), adjusting rod 4, equalizer 5, cable 8, lever 10 (see figure 8.6) manual drive of brake shoes and expansion bar 8.

Brake fluid emergency level sensor mechanical type. Building 2 (figure 8.9) the sensor with seal 4 and base 3 with reflector 6 are pressed by clamping ring 5 to the end of the tank neck.

A pusher 7 passes through the opening of the base, connected to a float 9 by means of a sleeve 8. A movable contact 11 is located on the pusher, and fixed contacts 10 are located on the sensor body. The cavity of the contacts is sealed with a protective cap 1. When the level of brake fluid in the brake reservoir drops to the maximum permissible level, the movable contact drops onto the fixed contacts and closes the circuit of the hazard warning lamp in the instrument cluster.