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The role of the automobile wheel bearing is mainly to bear the weight of the automobile and provide accurate guidance for the transmission of the wheel. The hub bearing bears both radial load and axial load, and is a very important safety part. At present, most domestic cars still use the traditional two sets of separate tapered roller bearings or angular contact ball bearings. This structure has to go through many processes such as clearance adjustment, pre-tightening, and grease addition during the assembly of the car. There are more manual controls. Factors, the assembly is more difficult, which causes the automobile assembly line to be lengthened, the cost is too high and the reliability is poor, and it is difficult to adapt to the fierce market competition.
In recent years, with the rapid development of front-drive cars, wheel bearings have undergone great changes, especially the joint research and development of well-known foreign automobile manufacturers and bearing manufacturers, and new wheel bearing units continue to emerge , Is currently the fourth generation.
Riveted forming of the third-generation hub uranium bearing In the design of the traditional third-generation hub bearing unit, the two inner rings are firmly connected together with a lock nut, and a new structure has been developed The axial force of the riveting forming of the shaft end causes the flanged inner ring to plastically deform, and it is pressed against the small inner ring. Removing the nut helps to reduce the weight and size of the hub unit and improve reliability. Both driving wheels and non-driving wheels are suitable. Using riveting forming technology, reliability will be improved, even if the connecting nut is loose, the bearing itself can provide preload guarantee.
The riveting process is used for riveting forming (as shown in the figure). When the inclined riveting head (upper die) is riveted on the bearing assembly, the shaft end of the flanged inner ring is generated by the pressure from the lower part. Plastic deformation until the small inner ring is firmly connected together. In the forming process, the deformation of the hub is divided into three stages: In the first stage, the riveting head descends and contacts the hub axle, and the deformation begins. In the second stage, the deformation further expands, and the hub axle expands in the radial direction and contacts the inner ring chamfer. Finally, the third stage is the completion of the riveting process. In the first stage, almost all of the riveting head pressure is used for the initial forming of the hub axle, and the load on the inner ring is small and constant. Entering the second stage, the pressure of the riveting head is transmitted to the inner ring, and the load of the inner ring increases rapidly. In the third stage, due to the pressure of the riveting head, the load of the inner ring gradually increases until it is saturated. After the riveting is finished, even if the riveting head has been lifted, the load of the inner ring has not been eliminated, and some load remains. It can be considered that the residual load forms the clamping force.
The traditional die forging compresses the entire workpiece and produces plastic deformation. Therefore, when processing large-size workpieces, a lot of pressure is required, and when applied to bearings, the deformation often exceeds the center area. Under the action of this huge pressure, the ball and raceway are squeezed, and the bearing is likely to be damaged during the machining process. However, the riveting process only deforms locally and only uses a small amount of pressure. By controlling the loading pressure, this kind of processing is very suitable for bearing assembly. The fatigue strength of the riveted forming edge and the creep resistance of the inner ring were tested through the durability test under heavy load. The static strength test is carried out to investigate the static strength of the riveting forming edge and the moment load rigidity test of the bearing, because the rigidity of the bearing will affect the steering stability of the vehicle when turning.
According to the results of various tests, the newly developed third-generation self-locking hub bearing with riveted inner ring is equal to or even better than the traditional hub bearing with lock nut. Under the premise of ensuring high reliability, the weight and size are reduced, which meets the current market demand and reduces vehicle fuel consumption.
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