1、 Working principle of hub bearing the hub bearing is divided into the first generation, the second generation and the third generation according to the structure. The first generation hub bearing is mainly composed of inner ring, outer ring, steel ball and cage. Its working principle is shown in Figure 1. The working principle of the first, second and third generations of wheel bearing is similar to that of ordinary bearing. They all use the rolling of steel ball in the inner ring, outer ring or flange raceway to carry and rotate relative to each other, so that the car can run.

2、 Abnormal noise of hub bearing

1. Abnormal noise characteristics of hub bearing

According to the working principle and stress characteristics of the hub bearing, its abnormal sound has three important characteristics: ① the hub bearing rotates with the wheel, and the abnormal sound frequency is proportional to the wheel speed. With the increase of vehicle speed, the abnormal noise of hub bearing becomes stronger continuously, and it will not occur only in a narrow speed range. ② The noise intensity of hub bearing is directly proportional to the load it bears. When the car turns, the hub bearing bears a large load and the abnormal noise is obvious. ③ The abnormal noise of hub bearing is easy to be confused with that of tire, engine, transmission, transmission shaft, universal joint and other transmission systems.

2. Abnormal noise of hub bearing

The main abnormal noise forms of hub bearing are as follows:

(1) Buzz

There are defects such as wear, peeling and indentation in the inner raceway of hub bearing, or when the bearing is loose, the abnormal noise of "guru" and "buzz" will continue to occur. With the increase of vehicle speed, the periodic grunt gradually turns into buzzing. When driving at high speed, it finally turns into high-frequency whistling.

(2) Squeak

When the hub bearing seal fails and the amount of internal lubricating grease is insufficient, the grease can not form oil film on the groove and the steel ball surface, resulting in the contact friction between the groove and the steel ball surface, resulting in sharp squeak.

(3) Giggle

When the surface of the ball inside the bearing is bruised, the ball is broken, and there are hard foreign matters inside the bearing, the ball will roll over the abnormal part of the raceway during the driving process, resulting in "yawning" abnormal sound.