Effect of Rolling Bearing Gap on Vibration And Noise

As a key component of the mechanical transmission system, the operation stability of the rolling bearing directly affects the overall performance of the equipment. Radial gap is one of the important parameters of bearing, which has a significant impact on vibration, noise and bearing life. Too large or too small the gap may lead to abnormal vibration, noise increase, and even shorten the bearing life. In this paper, we will discuss the influence of bearing gap on vibration and noise, and analyze the importance of tolerance control in bearing stability and life optimization.

1. Definition and classification of bearing gaps

Bearing gap refers to the gap between the inner and outer bearing rings, mainly divided into the following two types:

The radial swimming gap (Radial Clearance) rolling body is in the gap perpendicular to the bearing axis, affecting the bearing capacity, vibration and noise of the bearing.

The clearance of the axial gap (Axial Clearance) rolling body along the axis of the bearing mainly affects the axial positioning accuracy of the bearing.

According to the ISO 5753 and GB / T 4604 standards, the radial swimming gaps are usually divided into several grades, such as C2, C0 (standard), C3, C4, C5, etc., in which:

C2: minimum swimming gap, suitable for high precision, low vibration occasions.

C0: Standard gap, suitable for general applications.

C3~C5: Large gap is suitable for high temperature and high load conditions.

2. Influence of bearing gap on vibration and noise

2.1 Cause vibration and impact noise

When the radial swimming gap is too large, the bearing rolling body will have an impact during the operation process, resulting in the unstable contact between the inner and outer rings of the bearing, mainly manifested as:

The low-frequency vibration increases, and the operation is unstable.

The impact noise of rolling body and rolling road is intensified, resulting in the increase of equipment noise.The bearings may be unstable during operation, resulting in additional wear.

Experimental data show that in a motor bearing test, by increasing the standard gap C0 to C4, the measured vibration value is increased by about 30%, and the noise level increases by about 4~6dB.

2.2 Too small swimming gap may lead to noise spikes and shortened life span

If the bearing gap is too small, the lubrication film of the rolling body is insufficient, resulting in an increase of friction, and may increase due to thermal expansion, resulting in:

High-frequency noise spike, bearing running sound sharp.

The bearing produces internal stress due to excessive pretightening, increases friction heat and accelerates fatigue failure.

In the case of high speed operation, the lubricating oil film is damaged, the roller channel directly contact with the rolling body, increasing wear.

Case analysis: the spindle bearing of a high speed machine tool, working under C2 gap, found that the noise level increased by 7dB, and the bearing life was reduced by about 20%.

3. Function of bearing tolerance control on life and stability

3.1 Relationship between bearing gap and service life

Reasonable swimming gap can optimize the rolling contact state and extend the bearing life.

Experiments show that C0 or C3 gaps can provide optimal vibration control and life balance under conventional conditions.

3.2 Tolerance control optimization strategy

To ensure the stability and life of the bearings in different application scenarios, the tolerance control should be optimized, including:

Accurately control the bearing, shaft, bearing seat coordination to avoid excessive surplus or too small clearance.

Considering the influence of working temperature on swimming gap, it is recommended to choose C3 and above to compensate for the size change caused by thermal expansion.

Optimize the lubrication mode to ensure the stability of the lubricating oil film within the swimming range, and reduce the noise and friction wear.

4. Example analysis of bearing gap selection

Case 1: High-speed motor bearings

Operating condition: motor speed 12,000 rpm, temperature 80℃, requiring low noise operation. Optimization scheme: select C3 gap bearing to ensure that the gap is kept in a reasonable range after temperature rise, and use low noise grease. Results: vibration level was reduced by 15%, noise reduced by 5dB, and bearing life increased by 30%.

Case 2: Heavy-load construction machinery bearings

Working condition: excavator rotary bearing, low speed and heavy load, large temperature change in working condition. Optimization scheme: use C4 gap to avoid bearing jamming due to load and thermal expansion and cold contraction, and use high viscosity grease. Results: Reduce the rolling body impact and improve the bearing life by 20%.