There is a certain gap between the inner and outer rings of rolling bearings and the rolling body, so there can be relative displacement between the inner and outer rings.

When there is no load, one ring is fixed and the other ring moves from one limit position to another limit position along the radial and axial directions of the bearing, which are called radial clearance and axial clearance respectively, as shown in FIG. 2.

According to the state of the bearing, clearance is divided into three kinds.

1. Original clearance. Refers to the clearance of the rolling bearing in the free state before installation, which is determined by the manufacturer’s processing and assembly.

2, installation clearance, also called with clearance. It is the clearance between the bearing and the shaft and the bearing seat when they are installed and not yet working.

The mounting clearance is smaller than the original clearance due to interference mounting, either an increase in the inner ring, a decrease in the outer ring, or both.

3. Work gap. When the rolling bearing is in the working state, the temperature rise and thermal expansion of the inner ring are the largest, so that the bearing clearance is reduced.

At the same time, due to the effect of load, the contact between the rolling body and the raceway produces elastic deformation, which increases the bearing clearance. Whether the working clearance of the bearing is larger or smaller than the installation clearance depends on the comprehensive effect of these two factors.

Working clearance is an important quality index of rolling bearing and an important parameter in bearing application.

In practical use, the working clearance of bearings will affect the load distribution, vibration, noise, friction torque and life of bearings. Improper working clearance of bearings can cause harm to the reducer.

1.The working clearance of the bearing is too small

If the working clearance of bearings is too small, the friction torque of bearings will be increased, resulting in a lot of heat, which is easy to cause heat damage of bearings.

This is because, when the working clearance of the bearing is too small, it will lead to poor lubrication of the rolling body of the bearing and the inner and outer ring of the bearing. Due to dry friction, a lot of heat is generated, resulting in wear, cementation, swelling and other phenomena of the inner and outer ring of the bearing, which will cause bearing damage.

2.The working clearance of bearing is too large

The working clearance of bearings is too large, mainly caused by the selection of too large natural clearance of bearings, bearing compression force is not enough.

In the speed reducer, when the natural clearance of the bearing is large, the working clearance is relatively large, which will cause the vibration of the reducer in the operation process is large, reducing the service life of the bearing.

Through analyzing the fault of the reducer in production, it is considered that the bearing damage of the reducer is caused by too small working clearance of the bearing.

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