The main function of hub bearing is to bear the load and provide accurate guidance for the rotation of hub. It bears both axial and radial loads, and is a very important part. The traditional bearings for automobile wheels are composed of two sets of tapered roller bearings or ball bearings. The installation, oiling, sealing and clearance adjustment of bearings are all carried out on the automobile production line. This kind of structure makes it difficult to assemble, high cost and poor reliability in the automobile factory. In addition, when the automobile is maintained in the maintenance point, the bearings need to be cleaned, oiled and adjusted. Hub bearing unit is developed on the basis of standard angular contact ball bearing and tapered roller bearing. It integrates two sets of bearings, and has the advantages of good assembly performance, omitting clearance adjustment, light weight, compact structure, large load capacity, fitting grease in advance for sealed bearing, omitting external hub sealing and avoiding maintenance. It has been widely used in cars There is also a trend of gradually expanding the application of trucks.