Application of ball bearing
The purpose of ball bearing is to determine the relative position of two parts (usually shaft and bearing seat), ensure their free rotation, and transfer the load between them. At high speeds, such as in gyro ball bearings, this use can be extended to include free rotation with little wear in the bearings. In order to achieve this state, two parts of the bearing can be separated by an adhesive fluid film called elastohydrodynamic lubrication film. Denhard (1966) pointed out that the elastohydrodynamic lubrication film can be maintained not only when the bearing bears the load on the shaft, but also when the bearing bears the preload so that the positioning accuracy and stability of the shaft do not exceed 1 microinch or 1 nanoinch.
Ball bearings are used in various machines and equipment with rotating parts. Designers often have to decide whether ball bearings or fluid film bearings should be used in specific applications. The following characteristics make ball bearings more desirable than fluid film bearings in many situations,
1. The starting friction is small and the working friction is appropriate.
2。 Capable of withstanding combined radial and axial loads
8. Not sensitive to interruption of lubrication
4. No self excitation instability.
5. It is easy to start at low temperature.
In a reasonable range, changing the load, speed and working temperature has little effect on the good performance of ball bearings.
The following characteristics make ball bearings less desirable than fluid film bearings.
1. The finite fatigue life varies greatly
2. The required radial space is large
3. Low damping capacity.
1. The noise level is high·
6. The alignment requirements are strict.
6. High cost
According to the above characteristics, piston engines usually use fluid film bearings, while jet engines almost only use ball bearings. All types of bearings have their unique advantages. In a given application, the most appropriate bearing type should be carefully selected. The British Engineering Science Data Organization (ESDU 1965, 1967) provided useful guidelines for the selection of bearings.
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