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Pic. 27: 1. Disc brake. 2. The main cylinder of the hydraulic drive of the brakes. 3. The pipeline of the front brake drive circuit. 4. Front brake guard. 5. Front brake caliper. 6. Tip with pipeline. 7. Master cylinder reservoir. 8. Fixed contact. 9. Moving contact. 10. Terminal body. 11. Pusher for checking the serviceability of the liquid level control device. 12. Tank cover. 13. The body of the contact device. 14. Reflector. 15. Float. 16. The pipeline of the rear brake drive circuit. 17. Flange of the rear tip of the cable sheath. 18. Rear brake wheel cylinder. 19. Rear brake pressure regulator. 20. Pressure regulator drive lever. 21. Plug of the pressure regulator housing. 22. Sleeve. 23. piston head seal. 24. Spring plate. 25. Pressure regulator housing. 26. Spring. 27. Piston sealing ring. 28. Pressure regulator piston. 29. The axis of the lever. 30. Lever plate. 31. Block of the brake mechanism. 32. The lever of the manual drive of the pads. 33. Rack lever drive pressure regulator. 34. Bracket for fastening the cable sheath. 35. Rear cable. 36. Locknut. 37. Adjusting nut. 38. Sleeve. 39. Rear cable guide. 40. Guide roller. 41. Front cable. 42. The return lever of the parking brake. 43. Bracket for parking brake lever. 44. Latch lever. 45. Emphasis of the switch of a control lamp of a parking brake. 46. lever latch rod. 47. Parking brake lever. 48. Parking brake lever button. 49. Stoplight switch. 50. Brake pedal. 51. Vacuum amplifier. 52. O-ring spring plate. 53. Fitting. 54. Lock washer. 55. Sealing gasket. 56. Spacer ring. 57. Vacuum valve body. 58. Vacuum valve. 59. Rod seal holder. 60. Stem seal. 61. Stock. 62. Valve body return spring. 63. Diaphragm. 64. Cover of the vacuum booster housing. 65. Vacuum booster valve body. 66. Buffer rod. 67. The outer sheath of the hose. 68. Thread sheath. 69. Inner shell. 70. Piston thrust plate. 71. Valve piston. 72. Seal of the cover of the vacuum booster housing. 73. Vacuum booster valve. 74. Protective cover of the valve body. 75. Air filter. 76. Vacuum booster valve pusher. 77. Valve return spring. 78. Valve spring. 79. The body of the vacuum booster. 80. Adjusting bolt. 81. Front brake drive piston. 82. Piston return spring. 83. thrust washer. 84. Rear brake drive piston. 85. Piston stop screw. 86. O-ring. 87. O-ring spring. 88. Plug of the main cylinder body. I - master cylinder reservoir. II - Pressure regulator. III - Scheme of the brake drive. IV - Master cylinder and vacuum booster.
The brake system of a car, according to its purpose and functions, is divided into working, spare and parking.
The service brake system ensures the regulation of the vehicle speed and its stopping with the required efficiency, the spare system provides for stopping the vehicle with the required efficiency in the event of failure of the service brake system, and the parking system serves to hold the vehicle at a standstill. It can also be used as an emergency in case of failure of the working or spare brake systems.
The working brake system has a double-circuit separate hydraulic drive to the brake mechanisms of the front and rear wheels, which significantly increases the safety of the car. If one of the circuits fails, the other is used as a spare brake system, i.e. it is part of the service brake system.
Brake drive
The hydraulic drive includes a brake pedal 50, a vacuum booster 51, a master cylinder 2 of the hydraulic brake drive, a reservoir 7, a rear brake pressure regulator 19, wheel (workers) brake cylinders, pipelines and hoses.
Pedal 15 (see fig. 15) the brake is suspended from the bracket 4 together with the clutch pedal using the axis 8. Split plastic bushings 9 are installed in the pedal hub, through which the inner metal bushing 5 passes. The brake pedal rotates relative to this bushing. The pedal is pivotally connected to the pusher of the vacuum booster and returns to its original position by the force of the withdrawal spring. In this position, the pedal stop rests against the switch buffer 49 (see fig. 27) stop signal.
The vacuum booster reduces the force applied to the brake pedal when braking. It is attached to the clutch and brake pedal bracket plate on four studs with nuts. A rubber insulating gasket is installed between the vacuum booster and the bracket plate.
Between the housing 77 and the cover 64 of the housing of the vacuum booster, the outer belt of the rubber diaphragm 63 is clamped, separating the booster into vacuum and atmospheric cavities. The vacuum cavity is connected to the engine inlet pipe through a hose 6 with a tip and valve 58. To seal the connection, the tip 6 is connected to the vacuum booster through a rubber flange.
Inside the vacuum booster there is a plastic valve body 65, the shank of which is sealed with a seal 72 at the exit from the vacuum booster body. To protect the movable shank of the valve body from contamination, a corrugated protective cover 74 is put on the flanged part of the amplifier body and on the shank of the valve body.
The valve body 65 contains: a buffer 66, a piston 71 with a pusher 76, a rubber valve 73, springs with support cups and an air filter 75.
The thrust plate 70 enters the groove of the piston 71, the other end of which abuts against the belt of the diaphragm 63, which prevents it from falling out. The plate 70 fixes in the housing 65 the piston assembly with the pusher 76 and the valve 73. The rod 61 of the master cylinder piston drive rests against the buffer 66. At the exit from the housing of the vacuum booster, the rod is crimped with a seal 60, which is pressed by the clip 59 to the seat of the booster housing. A bolt 78 is screwed into the end hole of the rod, which regulates the output of the rod from the amplifier housing (1.05-1.25mm) The ball head of the pusher 76 is crimped into the piston seat.
Rubber valve 73 is assembled on the pusher. The movable valve head, reinforced with a metal washer, is pressed by a spring through the support cup to the rear end of the piston (at full disengagement). The body 65 has a seat for the moving valve head. The fixed shoulder of the valve 73 is pressed by a spring through the support cup to the inner wall of the valve body shank, creating a reliable seal. To clean the atmospheric air, a foam air filter 75 is installed in the shank of the valve body. The valve body 65 is constantly pressed by the spring 62 towards the cover 64. The body 77 and the cover of the amplifier are connected to each other by inserting the protrusions of the cover into the depressions of the body and further turning the cover to the factory of its edges under the protrusions of the body. The connector of the cover and the body of the amplifier is sealed with a shoulder of a rubber diaphragm 63, sandwiched between them.
In the amplifier housing, a plastic hose tip 6 is attached through a rubber flange, in which a vacuum valve 58 is mounted, which prevents the combustible mixture from entering the vacuum cavity of the amplifier.
The main cylinder 2 of the hydraulic brake drive is mounted on two studs to the vacuum booster. On top of its body, there are three threaded holes for fittings of pipelines that drain fluid into the front and rear brake drive circuits, and two sockets in which fittings are fastened with lock washers, connected by hoses to the reservoir of hydraulic brakes. The inner cylindrical bore of the cylinder is machined with great precision and high surface finish. On the one hand, the cylinder cavity is closed with a screw plug 86. Two pistons are installed in series in the cylinder, one of which actuates the rear brakes, the other - the front ones. Return springs 80 are installed between the plug and piston 82, as well as between pistons 82 and 79, under the action of which they return to their original position when released. In this case, the stroke of the pistons in the cylinder is limited by screws 83, the shanks of which go into the longitudinal grooves of the pistons. The piston 82 of the rear brake drive is sealed in the cylinder with two rings 84. The front ring is pressed against the end surface of the groove by the spring 85. The other end of the spring rests against the plate 52. The rear ring is pressed against the end of the piston-spring 80 through the washer 81.
The piston 79 of the front brake drive has a similar seal, only the rear ring is located in the piston groove and has a different shape.
Spacer rings 56 are freely put on both pistons. In the initial position of the piston, the spacer ring, abutting against the locking screw, removes the sealing ring from the end of the groove. At the same time, through the resulting gap, the working cavity of the cylinder communicates with the reservoir of the hydraulic brake drive.
The groove of the front sealing ring through the radial hole and the axial channel in the piston communicates with the working cavity of the cylinder. Therefore, when the fluid pressure increases in the working cavity, the sealing ring is pressed more tightly against the cylinder mirror.
The sequential arrangement of the pistons in the cylinder provides a separate drive for the front and rear brakes.
The reservoir of the hydraulic cylinder is two-section, made of translucent plastic, which provides visual control of the liquid level. At the bottom of the tank body there are two tips for connecting hoses. A cover 12 is screwed onto the filler neck of the tank, which presses the body 10 of the terminal device and the reflector 14 to the end of the neck. In case 10, a device for monitoring the level of liquid in the tank is mounted. It consists of a float 15, on the stem of which there is a movable contact 9, and a fixed contact 8, fixed in a plastic housing 10. When the liquid level drops, the float drops, the contacts close the control lamp circuit, and it lights up.
A pusher 11 is installed in the central hole of the terminal device housing, when pressed, the operability of the control lamp circuit is checked at a full liquid level in the tank.
The pressure regulator 19 is included in the rear brake drive in order to prevent an increase in pressure in this circuit with a decrease in the load on the rear axle of the wheels. Otherwise, it is possible to block the rear wheels and their skidding. The pressure regulator is attached with two bolts with spring washers to the body bracket, and one hole in the bracket is oval, which allows you to adjust the position of the pressure regulator.
The pressure regulator is actuated by a torsion lever 20, which is attached to the body by a clip 32 (see fig. 23) through the rubber support sleeve 33. The long arm of the lever 31 of the pressure regulator drive is pivotally connected through the rack 13 to the rear axle beam, and the short arm passes through the axle hole 29 (see fig. 27) and enters the cutout of the lower part of the piston 28 of the pressure regulator. This shoulder transmits the oscillatory movement of the rear axle beam to the piston.
Fittings of two pipelines are screwed into the pressure regulator housing: the lower one for supplying fluid from the master cylinder, the upper one for supplying fluid to the rear brake wheel cylinders.
The piston 28 of the pressure regulator at the outlet of the housing is sealed with a ring 27 located in a metal cage. This ring is pressed against the lower part of the body by a spring 26. The upper end of the spring abuts against the floating plate 24 and through it into the shoulders of the piston. The spring tends to press the piston until it stops in the plug 21, which is screwed into the pressure regulator housing. A sealing gasket is installed under the cork. Sleeve 22 is loosely put on the piston head. It limits the rise of the seal 23 up to the piston head.
Three-layer high pressure hose. The inner 69 and outer 67 shells of the hose are rubber, a filament shell 68 is placed between them. During operation of the car, cracks and other damages on the outer shell of the hose are not allowed.