The rolling bearing itself does not generate noise. The bearing noise is a sound phenomenon caused by the vibration and collision of parts during the operation of the bearing. The ratio of elastic vibration and strong vibration of bearing parts is solid sound, and the air vibration caused by solid sound in the sound frequency range is the noise of the bearing.
The usual "bearing noise" is actually the sound effect of the bearing directly or indirectly generating vibrations with the surrounding structure. This is why many times the noise problem can be regarded as a vibration problem involving the entire bearing application.
Types of bearing noise
The vibration of rolling bearings is the source of bearing noise. Different bearing noise comes from different types of bearing vibration. Like the vibration of the bearing, the mechanism of bearing noise is also very complicated. According to the characteristics of bearing noise, the bearing noise can be divided into the following forms:
The noise generated by factors such as the structural type and size of the bearing is the basic noise: such as the noise generated by the elastic deformation of the bearing, rolling elements, clearance, cage, etc.
Noise caused by bearing surface effects: such as the noise caused by the roundness, waviness, roughness, defects, etc. of the inner and outer rings of the bearing and the working surface of the steel ball. A large number of experimental studies have shown that the ratio of the surface quality of the outer ring, inner ring and steel ball of the deep groove ball bearing to the bearing noise is 1:3:10, and the surface quality of the steel ball has the greatest impact on the noise of the deep groove ball bearing .
Noise caused by friction and lubrication: Friction and lubrication have a great influence on the noise of rolling bearings. If the friction is small and the lubrication state is good, the noise generated by the bearings is small.
Noise caused by working conditions: bearing load, rotation speed, and installation coordination state directly affect the bearing noise. The higher the bearing speed and the greater the load, the greater the noise generated by the bearing. In addition, relevant research shows that 50% of bearing noise is caused by poor installation.
Causes of bearing noise
Excitation due to changes in the number of loaded rolling elements: When a radial load is loaded on a bearing, the number of rolling elements carrying the load will change slightly during operation, causing a deviation in the load direction. The resulting vibration is inevitable, but it can be reduced by axial preloading, which is loaded on all rolling elements (not applicable to cylindrical roller bearings).
Local damage: Due to operation or installation errors, a small part of the bearing raceways and rolling elements may be damaged. During operation, damaged bearing components will produce specific vibration frequencies; vibration frequency analysis can identify damaged bearing components. This principle has been applied to condition monitoring equipment to monitor bearing damage.
Accuracy of related components: When the inner and outer rings of the bearing are in close cooperation with the bearing housing or the transmission shaft, the inner and outer rings of the bearing may be deformed due to improper matching of the shapes of adjacent components. If deformation occurs, vibration may occur during operation.
Contaminants: If the equipment is operated in a polluted environment, impurities may enter the bearings and be crushed by the rolling elements. The degree of vibration generated depends on the number, size and composition of the crushed foreign particles. Although this situation does not produce the typical frequency form, you can hear a disturbing noise.
Others: The reasons for the noise of rolling bearings are more complicated. One is the wear of the matching surfaces of the inner and outer rings of the bearing. Due to this wear, the matching relationship between the bearing and the housing, and the bearing and the shaft is destroyed, causing the axis to deviate from the correct position. The shaft produces abnormal noise when moving at high speed. When the bearing is fatigued, the metal on the surface will peel off, which will also increase the radial clearance of the bearing and produce an abnormal noise. In addition, insufficient bearing lubrication, dry friction, and broken bearings can all produce abnormal sounds. Bearing wear and loose cage damage will also produce abnormal noise.