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Pic. 20: 1. Gearbox. 2. Output shaft flange. 3. Elastic driveline coupling. 4. Flexible coupling flange. 5. Front driveshaft. 6. Intermediate support. 7. Front universal joint. 8. Rear driveshaft. 9. Rear universal joint. 10. Rear axle. 11. Car wheel. 12. Pillow support. 13. The propeller shaft support housing. 14. Bearing support cardan, shaft. 15. Support bracket. 16. Crossbar of the intermediate support. 17. Distance sleeve. 18. Rubber bushing. 19. Needle bearing snap ring. 20. Needle bearing. 21. Needle bearing seal. 22. Universal joint cross. 23. Cardan yoke. 24. Nut of fastening of a universal joint fork. 25. Flange - universal joint fork. 26. Balancing plate. 27. Front propeller shaft safety bracket. 28. Gland clip. 29. Plug holes for lubrication of splines. 30. Elastic element of an elastic coupling. 31. Metal insert of an elastic coupling. 32. The secondary shaft of the gearbox. 33. Nut. 34. Centering ring seal. 35. Bolts for fastening the flexible coupling to the flanges. 36. Centering ring. 37. Centering sleeve. 38. retaining ring. 39. Oil seal. 40. Splined shank of the front propeller shaft. I - Scheme of cardan transmission. II - Cardan joint.
The torque from the secondary shaft of the gearbox to the mechanisms of the rear axle is transmitted by a driveline, which operates under conditions of a changing angle of torque transmission due to the elastic suspension of the rear axle. At the same time, the distance between the fixed gearbox and the oscillating rear axle also changes. Therefore, in the cardan transmission there are elements that shorten or lengthen it, as well as break at a certain angle. Such elements are: a spline connection of an elastic coupling 3 and three cardan joints - two rigid 7 and 9 and one elastic 3.
The cardan gear is two-shaft with an intermediate support 6, which significantly reduces its vibration and runout. Between themselves and the main gear gear, the cardan shafts are connected by rigid cardan joints 7 and 9, and with the secondary shaft of the gearbox by an elastic joint 3 (clutch). The flexible coupling significantly reduces driveline noise and vibration and allows torque to be transmitted at an angle.
The clutch consists of six rubber elements 30, between which there are metal inserts 31. The elastic rubber elements of the clutch are vulcanized to the inserts and form a single whole. The elastic coupling is located between two flanges 2 and 4, which are connected to the coupling by bolts 35. In this case, the protrusions of the liners go into the grooves of the flanges, centering the elastic coupling on the flanges. Self-locking nuts with nylon inserts are screwed onto the coupling mounting bolts.
To ensure backlash-free connection of the coupling with the flanges and create a constant tightness in the mounting bolts, the holes in the elastic coupling for the mounting bolts are made from the center at a larger diameter than in the flanges. Therefore, before connecting the coupling to the flanges, it is compressed with a special clamp until the holes in the coupling and flanges match, and then the fastening bolts are installed. After removing the clamp, the gaps are selected, and an interference is created in the fasteners. The same clamp is also used when removing the clutch.
The front cardan shaft 5 is made of a thin-walled pipe, to the ends of which splined tips are welded. On the splines of the front tip 40 is the flange 4 of the elastic coupling. The rear tip rests on the ball bearing 14 of the intermediate support 6. The bearing is located in the steel housing 13 and is fixed in it with a retaining ring. On the shaft, the bearing is clamped with a nut 24 between the shoulder of the tip and the yoke 23 of the cardan joint. The bearing is of closed type, with seals that securely retain the lubricant incorporated during assembly. Additionally, the bearing is protected by two dirt deflectors. To dampen the vibrations of the driveline, the bearing housing is located in a rubber cushion 12, which is vulcanized to the metal surfaces of the bearing housing 13 and the bracket 15 of the intermediate support. The cushion configuration is such that the front driveshaft can have some axial movement. Bracket 15 of the intermediate support is attached to the cross member with two bolts and nuts, and the cross member of the intermediate support is fixed on two bolts welded to the floor of the body. Metal spacer bushings 17 and rubber bushings 18 are installed on the fastening bolts, which isolate the cross member from the floor of the body.
For the safety of the car, a safety bracket 27 is installed under the front propeller shaft, which prevents the shaft from falling when the elastic coupling is destroyed.
The rear propeller shaft 8 differs in its design from the front propeller shaft in that not tips, but forks of universal joints are welded to the ends of the shaft tube. With the help of universal joints, the rear propeller shaft is connected at one end to the front propeller shaft, and at the other end to the final drive gear.
The universal joint consists of two forks 23, a cross 22, four needle bearings 20, oil seals 21 and circlips 19.
The cross connects two forks pivotally; at the same time, the spikes of the cross come into the holes of the forks. Needle bearings are installed on the spikes, the bodies of which are pressed into the holes of the forks with a force of 8000 N (800 kgf). During assembly, the bearings are lubricated with FIOL-2U grease. To hold the lubricant in the needle bearings and seal them, a steel cage is pressed onto each spike of the cross, in which the oil seal 21 is located. It seals the cavity of the needle bearing.
The bearings are held in the holes of the forks by retaining rings 19. These rings are available in five thicknesses. By selecting the rings by thickness, the axial clearance of the cross is set within 0.1-0.4 mm. This gap is needed to center the cross in the forks.
Each ring is painted in its own color. The color of the ring depends on the thickness: the 1.62 mm thick ring is yellow, 1.59 black, 1.56 blue, 1.53 dark brown, 1.50 natural. The selection of retaining rings is carried out using a special caliber, which has four probes with a thickness of 1.53; 1.56; 1.59 and 1.62 mm.
After pressing one of the needle bearings into the fork hole, a 1.56 mm thick retaining ring is installed in the groove and then the other bearing is pressed all the way into the end of the cross (in this case, there is no axial clearance of the cross). Noise measures the distance between the bearing housing and the end face of the annular groove. Depending on the measured distance, taking into account a gap of 0.1-0.4 mm, a second retaining ring of the appropriate thickness is inserted. So, for example, if a probe with a thickness of 1.56 mm passes, then a ring with a thickness of 1.53 mm should be installed. If the stylus is the thinnest (1.53mm) does not enter the groove, then the previously installed ring must be replaced with a ring having a thickness of 1.50 mm. If the probe with a thickness of 1.62 mm passes into the groove with a gap, then the previously installed ring must be replaced with a new one with a thickness of 1.62 mm.
After installing the retaining rings, it is necessary to hit the bearings with a hammer with a plastic striker. Under the impact and elastically compressed glands, the gap between the bottoms of the bearing housings and the retaining rings is selected and gaps appear between the bearing housings and the ends of the cross spikes. After assembly, the universal joint forks should turn easily, without jamming.
After assembly, the driveline is balanced on special balancing stands. The imbalance is eliminated by welding metal plates 26 to the pipes of the cardan shafts. In order not to disturb the factory balance during disassembly caused by the replacement of worn or damaged parts, it is necessary to put marks on the parts to be separated before disassembly and install them in their original places during assembly. Any imbalance causes vibration and rapid wear of the car transmission.
Noise and vibration of the cardan transmission appear when the bolts and nuts fastening its parts and assemblies are loosened, when the bearings of the crosses and the intermediate support are worn, as well as when the cardan shafts are deformed. Due to wear or damage to the seals, grease leaks from the bearings of the crosses or from the spline connection, which leads to their intensive wear.
In order to increase the service life of universal joints, a new universal joint has been produced since 1988, with new joints of increased durability. Cardan joints of a new design have improved sealing of needle bearings and better dirt protection, which is achieved by using radial-end seals.
Cardan transmission operates in the most unfavorable conditions: in the zone of environmental impact (dirt, moisture) and under constantly changing loads. In order to prevent intensive wear of the hinges under these conditions, in addition to improving the design of the bearing seals, it is important to monitor the tightness of the bearings of the crosses and the intermediate support and prevent the driveline from beating, which can occur when the shafts are deformed due to rubbing against road obstacles or loosening of the bolts for fastening the forks of the hinges or intermediate support. Balancing imbalance is possible if the rules for assembling the driveline during its repair are not followed.
After a long period of car use (over 100,000 kilometers) it is recommended to remove the cardan gear and check the cardan joints for ease and smoothness of turning the forks and for the absence of axial and radial clearances in the bearings of the crosses and intermediate support. It is also necessary to make sure that there are no traces of rubbing against road obstacles on the cardan shafts.
If the turning of the forks is smooth, there are no jamming and tangible radial and axial clearances in the bearings and circumferential clearances in the spline connection, and lubricant is not ejected through the seals of the crosses, then the driveline is suitable for further operation. Otherwise, it will be repaired.