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Pic. 26. Wheel brakes: 1. Front wheel brake disc. 2. Protective cover. 3. Fitting for pumping the drive of the front brakes. 4. Connecting tube of cylinders. 5. Cotter pin. 6. Wheel cylinder lock. 7. Pins for fastening the brake pads. 8. O-ring. 9. Wheel cylinder piston. 10. Protective cap. 11. Linings * brake pads. 12. Spring of a finger of fastening of a block. 13. Front brake wheel cylinder. 14. Clamping spring pads. 15. Brake shoe. 16. Brake caliper. 17. Caliper mounting bolts. 18. Caliper mounting bracket. 19. Swivel fist. 20. Brake block of the brake mechanism of a back wheel. 21. Support column pads. 22. The lever of a manual drive of pads. 23. Lever pin. 24. Wheel cylinder. 25. Stop screw. 26. Thrust ring. 27. Crackers. 28. Spring. 29. Support cup. 30. Sealant. 31. Wheel cylinder piston. 32. Fitting for pumping the rear brake drive. 33. Fitting of the brake fluid supply pipe. 34. Shoe stop. 35. Protective cap of the wheel cylinder. 36. Top coupling spring pads. 37. Brake pad spacer. 38. Sheath of the rear cable. 39. Support shield brake pads. 40. Lower coupling spring of pads. 41. Rivet fastening the support and guide plates. 42. Support plate pads. 43. Pad guide plate. 44. Rear parking brake cable. 45. Rear cable spring. 46. The tip of the rear cable. I - Front wheel brake. II - Rear wheel brake.
Brake mechanisms of wheels are mounted directly in wheels of the car. They are designed to create resistance to the movement of the car.
The brake mechanism of the front wheel is disc, open, which ensures its good cooling and, as a result, more efficient braking with frequent use of the brakes, when the friction coefficient of their linings can decrease due to heating of the pads.
The brake mechanism consists of a caliper 16 assembled with working cylinders, a disc 1, two brake shoes 15, pins 7 for fastening the shoes and pipelines.
The caliper is cast from ductile iron. It is attached to the bracket 18 with two bolts 17, which are fixed by bent locking plates on the edge of the bolts. The bracket 18 is attached to the flange of the steering knuckle 19 together with the protective cover 2 and the swing arm. The caliper has a radial groove to accommodate the brake disc and two transverse grooves in which the brake pads are located. In the lugs of the caliper, there are two windows with guide grooves, in which two opposite wheel cylinders 13 are installed. The exact location of the cylinders relative to the caliper is ensured by spring clips 6. When the cylinder is installed in the caliper groove, the lock enters the special side groove of the caliper under the action of the spring.
The body of the working cylinder is cast from aluminum alloy. The cylinder contains a steel hollow piston 9, which is sealed with an elastic rubber ring 8. It is located in the groove of the cylinder and serves not only to seal the gap, but also to return the piston to its original position when released. The cylinder cavity is protected from contamination by a rubber cap 10, the outer edge of which is held on the cylinder shoulder, and the inner edge covers the piston seat band.
The working cavities of the cylinders are interconnected by a tube 4. A fitting 3 is screwed into the outer cylinder for pumping the front brake drive, and into the inner fitting for supplying fluid. The pistons 9 abut against the brake shoes 15, on which the friction linings 11 are glued. The shoes are mounted on the guide pins 7, which are kept from axial displacement by cotter pins 5, and so that there are no vibrations of the shoes on the fingers, springs 14 are used, pressing the shoes to the fingers. Springs 12 are installed under the finger heads.
The brake disc is connected to the wheel hub with two dowel pins. Part of its working surface is located between the brake pads. The friction surface of the disc is processed with great precision, which increases the service life of the brake mechanism.
When braking, pistons under fluid pressure move out of the wheel cylinders and press the pads against the brake disc. Braking torque is generated on the front wheels. When moving, the pistons carry along the sealing rings 8, which are twisted. When releasing, when the pressure in the drive of the front wheels drops, the pistons are pushed back into the cylinders due to the elastic deformation of the rings 8. In this case, the linings 11 of the brake pads will be in light contact with the brake disc.
As the pads wear, as the gap in the brake mechanism increases, more fluid pressure is created in the actuator to create a braking torque. Under the action of fluid pressure, the pistons 9 slip relative to the rings 8 and take a new position in the cylinders, which provides an optimal clearance between the disc and the pads. When replacing pads, when the thickness of the pads is reduced to 1.5 mm, the pistons are manually recessed into the cylinders to install new pads.
The brake mechanism of the rear wheel is drum, mounted on the support shield 39, which is bolted to the flange of the rear axle beam. A package of plates is attached to the lower part of the shield with two rivets 41, of which the plate 42 is a support for the brake shoes 20, and the plates 43 limit the axial movement of the lower part of the shoes. The inner curved plate limits the movement of the cable 44 towards the shield. In the upper part of the shield 39, a wheel cylinder 24 is fastened with two bolts. Outside, a fitting 32 is screwed into the threaded hole of the cylinder for pumping the rear brake drive and a fitting 33 of the pipe for supplying fluid to the cylinder.
On both sides, pistons 31 are installed in the cylinder, complete with seals and parts of the automatic device. The main element of the automatic device is a split thrust ring 26, located in this subassembly between the shoulder of the thrust screw 25 and two crackers 27 with a gap of 1.4; 1.6 mm. Thrust rings are installed in the cylinder with an interference fit, providing a shear force of the ring along the cylinder mirror of at least 35 kgf, which exceeds the force from the coupling springs of the brake shoes. A slot is made in the thrust ring for air to escape when pumping the brake system.
To the end surface of the piston through the support plate 29, the seal 30 is pressed by the spring 28. From the outside, stops 34 are pressed into the pistons, into the grooves of which the upper ends of the brake shoes enter. The cavity of the wheel cylinder is sealed with a rubber cap 35, which is put on the piston with the inner edge, and on the cylinder body with the outer edge.
With the optimal clearance between the pads and the drum, the pistons 31 in the wheel cylinder move by the amount of the gap between the shoulder of the thrust screw 25 and the shoulder of the thrust ring (1.4-1.6mm). In this case, the pads are pressed against the brake drum, creating the necessary braking torque, and the thrust rings 26 remain in place.
When the linings are worn, the clearance of 1.4-1.6 mm is completely selected and the shoulder of the thrust screw rests against the shoulder of the thrust ring, as a result of which the thrust ring moves after the piston by the amount of wear of the linings. When braking is stopped, the pistons are shifted by the force of the coupling springs until the crackers 27 stop against the shoulder of the stop screw 25. Thus, the optimal gap between the shoes and the drum is automatically maintained.
For fixation from axial displacement of the middle part of the pads, springs are installed on the racks 21, which press the middle part of the pads to the shield 39 of the brake. Due to the non-rigid connection of the pads to the brake shield, they self-align themselves at the moment of contact with the brake drum, which improves braking efficiency and leads to more uniform wear of the linings glued to the pads.
Brake drum 4 (see fig. 21) cast from an aluminum alloy, has stiffening ribs on the outer surface and through holes for communicating the inner cavity of the drum with the atmosphere. Inside the drum there is a cast-iron ring 5 with which the brake pads are in contact. The drum is attached to the axle shaft flange with two pins 2 and additionally together with the wheel with bolts 1. Two threaded holes are made in the drum, into which dowel pins 2 are screwed when the drum is removed. This removal is only possible when the drum "not stuck" to the flange of the axle shaft, otherwise the threads in the holes of the drum may be broken. To prevent this from happening "sticking" during assembly, it is necessary to apply graphite grease to the contact surfaces of the drum and axle shaft.
When using the parking brake, the brake pads 20 (see fig. 26) are pressed against the drum by moving the lever 22 and the expander bar 37. The lever 22 is seated on the pin 23 and, together with the rib of the brake shoe, rests against the groove of the expander bar. The tip 46 of the rear cable 44 is put on the lower end of the lever. The second end of the cable is connected to the brake mechanism of the other wheel. For protection and abutment against the brake shield, both knees of the cable are enclosed in a multilayer sheath 38 of plastic tubes and wire braid. Return springs 45 are put on the ends of the cable, which return the rear cable to its original position when it is released from the force.