Open large image in new tab »
Pic. 29. Scheme of the brake system: 1. Guide pads; 2. Guide pin; 3. Front brake pads; 4. Caliper; 5. Hose of a contour of a drive of the left forward and right back brakes; 6. Front brake wheel cylinder; 7. Wheel cylinder piston; 8. Piston O-ring; 9. Brake disc; 10. Piston stroke limit screw; 11. O-ring; 12. Resistant cup; 13. Piston return spring; 14. Piston drive right front and left rear brakes; 15. O-ring spring; 16. Reservoir of the master cylinder; 17. Emergency liquid level sensor assembly; 18. Left front and right rear brake drive piston; 19. Seal; 20. Vacuum amplifier; 21. Valve body; 22. Diaphragm; 23. Piston; 24. Vacuum booster valve; 25. Valve spring; 26. Pusher return spring; 27. Air filter; 28. Pusher; 29. Brake pedal release spring; 30. Pressure regulator piston; 31. Piston sleeve; 32. Sealant; 33. Piston spring; 34. Pusher sealing rings; 35. Valve seat; 36. Valve spring; 37. Cork; 38. Valve; 39. O-ring valve seat; 40. Pusher; 41. Piston head seal; 42. Loop piping "left front and right rear brakes"; 43. Stoplight switch; 44. Tip of the brake light switch; 45. Brake pedal; 46. Stock; 47. Valve body return spring; 48. Coupling spring pads; 49. Rear brake pad; 50. Rear brake wheel cylinder piston; 51. Piston seal; 52. Thrust rings; A - vacuum cavity; B - atmospheric cavity; C - channel connecting the atmospheric cavity with the internal cavity of the valve; D - channel connecting the vacuum cavity with the internal cavity of the valve; F is the force of pressure on the piston from the details of its drive; R1 - fluid pressure in the main cylinder; R2 - fluid pressure in the wheel cylinders; E, G - pressure regulator chambers connected to the main cylinder; L, N - pressure regulator chambers. connected to wheel cylinders; K, M, H - gaps; I. The pedal is not depressed; II. Braking; III. Release.
When the brake pedal is depressed, it moves away from the tip 44 of the brake light switch, and the lamp circuit is completed, as a result of which the brake lamp lights up. At the same time, the pusher 28 moves along with the piston 23 and the valve body 21. Following the piston, the valve moves under the action of the spring 25 until it stops against the valve seat. When adhering to the seat, the valve separates chambers A and B. With further movement of the piston 23, its end moves away from the valve 24 and through the resulting gap the chamber. In communicates with the atmosphere. Therefore, atmospheric air enters chamber B through filter 27, through the resulting gap between the piston and the valve, and then through channel C. Atmospheric air creates pressure on diaphragm 22.
Due to the difference in pressure in chambers A and B and the force of pressing the brake pedal, the valve body moves along with the stem 46, which in turn acts on the piston 18 of the master cylinder. When the piston 18 moves, the spacer ring moves away from the locking screw 10, and the sealing ring 11 is pressed against the end of the piston groove by the spring 15. The compensation gap is blocked, and the main cylinder and reservoir are separated. With further movement of the piston 18 in the working cavity of the drive "left front - right rear brakes" fluid pressure is created, which is transmitted through pipelines to the wheel cylinders of the brake mechanisms. It also affects the floating piston 14, which, moving, creates pressure in the circuit "right front - left rear brakes". Under increasing fluid pressure, the high-pressure rings 11 begin to expand and fit more closely to the cylinder walls and to the end of the grooves, which improves the sealing of the pistons in the cylinder.
With an increase in pressure in the circuits, the force on the piston 30 of the pressure regulator increases, which tends to push it out of the regulator housing. When the force from the fluid pressure begins to exceed the force from the elastic lever, the piston begins to move out of the housing. Following the piston, under the force of the pusher sleeve spring and spring 36, the pusher 40 is displaced together with the sleeve and rings 34. In this case, the gap M between the plate and the seat 35 increases, and the gaps H and K decrease. When the gap H is completely selected and the valve 38 isolates the chamber G from the chamber N, the pusher 40, together with the parts located on it, stops moving after the piston. From now on, the pressure in the N chamber will change depending on the pressure in the L chamber. With further increase in the force on the brake pedal, the pressure in the chambers E, G and L increases, and the piston will continue to move out of the body.
At the same time, under the pressure of the fluid, the pusher bushing together with the sealing rings 34 and the spring plate of the pusher bushing will move towards the plug 37. In this case, the gap M and the volume of the chamber N will decrease. With a decrease in the volume of the chamber N, the pressure in it, and hence in the rear wheel drive, will increase and will almost always be equal to the pressure in the chamber L. When the clearance K is completely selected, that is, the piston head 30 touches the seal 41, the pressure in the chamber L, this means that in chamber N, it will grow to a lesser extent compared to chamber E and only due to the throttling of fluid between the piston head and seal 41. The pressure dependence in chambers L and E is determined by the ratio of the difference between the areas of the head and piston rod to the area of the head.
With an increase in the load on the car, the elastic lever 5 (see fig. 26) is loaded more, and the force on the piston from the side of the lever 7 increases. This means that the moment of contact between the piston head and the seal will be reached at a higher pressure in the master cylinder. Therefore, the efficiency of the rear brakes with increasing load on the car increases.
Fluid pressurized pistons 7 and 50 (see fig. 27) the wheel cylinders of the front and rear brakes move. In this case, the pistons 7 press the inner brake pads 3 against the disk 9, and the wheel cylinder assembly with the caliper 4 moves in the opposite direction under the force of the resulting reaction. The movable caliper presses the outer pad against the brake disc. When moving the pistons 50, a part of the gap is selected (1.25-1.65 mm) between the shoulders of the thrust screws and rings 52. In this case, the pads 49 are pressed against the brake drum, creating a braking torque on the wheels. When the pads are worn, the gap of 1.25-1.65 mm is completely selected, and the thrust screws press on the shoulders of the thrust rings 52 with a force that ensures the rings are shifted along the cylinder mirror by the amount of wear of the pads. That is, the rings 52 will take a new position in the cylinders, restoring again the optimal gap between the shoes and the drum.
If one of the circuits fails, the pressure regulator will work with part of its chambers, turning off the faulty circuit. So, if the circuit fails "right front - left rear brakes" O-rings 34, pusher bushing 40 will move under fluid pressure towards plug 37 until the pusher bushing spring plate stops against the valve seat. The pressure in the rear brake will be controlled by the part of the regulator that includes the piston 30 with the seal 41 and the housing sleeve into which the piston head goes. This part of the regulator will work in the same way as with a working system.
In the event of a circuit failure "left front - right rear brakes" fluid pressure pusher 40 together with its sleeve, sealing rings 34 are displaced towards the piston 30, pushing it out of the housing. In this case, the gap M increases, and the gap H decreases. When the valve 38 touches the seat 35, the pressure increase in the chamber N stops, i.e. The regulator acts as a pressure limiter.
When released, the brake pedal and all parts of the vacuum booster take their original position under the action of the springs, which leads to the cessation of the flow of atmospheric air into chamber B, and when valve 24 moves away from the seat of chambers A and B, they communicate with each other. The pistons 18 and 14 of the main cylinder under the action of the return springs are pressed all the way into the locking screws 10. At the same time, the spacer rings, abutting against the screws 10, divert the sealing rings 11 from the ends of the piston grooves, as a result of which compensation gaps are formed through which the working cavities of the cylinder communicate with cistern, i.e. the pressure in the circuits drops to atmospheric.
Chambers E and G of the regulator communicate with chambers L and N. The springs of the rear brakes remove the pads from the drums by the amount of the gap between the crackers and the shoulders of the thrust rings 52, and the pistons of the front brake wheel cylinders are removed from the pads due to the elasticity of the sealing rings.