The role of the hub bearing is mainly to bear the weight of the car and to provide accurate guidance for the hub drive.Hub bearing bears both radial and axial loads and is a very important safety component.Now domestic cars are mostly still adopts the traditional two separate set of tapered roller bearing and angular contact ball bearing, this structure should be adjusted when car assembly clearance, preloaded, fatliquoring process, mixed more artificial control factor, assembly is difficult, resulting in the automobile assembly line extension, high cost and poor reliability, it is difficult to adapt to the fierce market competition. 

In recent years, with the rapid development of front front drive car, the hub bearing has undergone great changes, especially the joint research and development of foreign well-known automobile manufacturers and bearing manufacturers, new hub bearing units have been emerging, and now it is the fourth generation. 

In the design of the traditional third-generation hub bearing unit, the two inner rings are firmly connected together by locking nuts, while the new structure developed by NSK is to produce plastic deformation of the inner ring with flange by riveting and pressing with the small inner ring through the axial force of the riveting and pressing at the shaft end.Removing the nut helps reduce the weight and size of the hub unit and improves reliability.Both drive and non-drive wheels are suitable.With riveting forming technology, the reliability can be improved, even if the connecting nut is loose, the bearing itself can also provide preload guarantee.

Riveting molding adopts the riveting process (as shown in the figure). When the inclined riveting head (upper die) rivets and presses on the bearing assembly, the shaft end with flange inner ring is subject to plastic deformation under the pressure from the lower part, until the small inner ring is firmly connected together.In the forming process, the hub deformation is divided into three stages: the first stage, the rivet head drops, contacts with the hub shaft, and the deformation begins.In the second stage, the deformation is further extended, and the hub shaft is extended radially and contacts with the chamfer of the inner ring.Finally, the third stage, the riveting process is completed.In the first stage, almost all the riveting head pressure is used for the initial forming of the hub shaft. The inner ring load is small and constant.In the second stage, the riveting head pressure is transferred to the inner ring, and the inner ring load increases rapidly.In the third stage, due to the riveting head pressure, the load of the inner ring gradually increases until it is saturated. After the end of riveting, even after the riveting head is lifted, the load of the inner ring is still not eliminated and some load is still retained.Residual load can be considered to form a clamping force. 

Traditional die forging compresses the whole workpiece and produces plastic deformation.Therefore, when processing large size workpiece, requires a great deal of pressure, and when applied to the bearing, deformation is often beyond the central area.Under this huge pressure, the ball and raceway are squeezed, the bearing is likely to be damaged during the processing, while the riveting process only produces local deformation and USES very little pressure.By controlling the loading pressure, this machining is suitable for bearing assembly.The fatigue strength and creep resistance of the inner ring of riveting forming edge were tested by the operation durability test under heavy load.The static strength test was carried out to investigate the static strength of the rivet forming edge and the torque load stiffness test of the bearing. 

According to the test results, NSK's newly developed riveting compression forming inner ring self-locking third-generation hub bearing is equal to or even better than the traditional hub bearing with locking nut.On the premise of ensuring high reliability, the weight and size are reduced to meet the current market demand and reduce vehicle fuel consumption.