Analysis Of Automobile Hub Bearings Failure

The main function of hub bearing is to support the automotive and guide for thetransmission of hub, moreover, it bears both radial load and axial load.When the automotiveturning on the incline, torque brought about by the axial force also can be bore. So, the hubbearing is important safety component, meanwhile, it is vulnerable.When fault occurs to thehub bearing, the fault site will cause noise and bearing heat. If fault occurs in the front hubbearing that will easily cause the direction of loss of control. Recently, In the domestic marketsome kind of car was reported failure of the front wheel hub bearing and this failure tends toincrease. When this failure happens, consumer use it for a short time and the mileage is alsovery short, and the bearing noise is very quite big which greatly troubled the consumer. Inorder to solve this problem and eliminate the complaint, we should take measure to find outthe cause of problem and make properly countermeasure.Based on the actual needs and the defective products collected from the market, thebearing fault characteristics and types are studied by statistics method. The studies show thatthe fault has no relation with any regions, but occurs when the car work in a short time or ashort mileage.A fault bearing choosed radomly is mouned in a passenger car, the vibration signals ofthe fault bearing and the normal one are collected, respectively, when the car runs fromlow-speed to high-speed. Then the signals are analyzed in time domain and frequency domain.In time domain, vibration signals of fault bearing and normal one are compared to checkwhether there are impact phenomena. While in the frequency domain, Hilbert transformdemodulation analysis is used to the frequency band with the vibration energy concentrated toget the modulation frequency. Comparision with the modulation frequency and the calculationpassing frequencied, the fault is identifed in the bearing outring, and the modulationbecomes serious with the vehcile speed increases. By increasing the shaft shoulder height of0.45mm and improving the surface roughness, defective rate in the same period decreasesfrom11.41%to0.63%.