The use of ball bearings
The purpose of a ball bearing is to determine the relative position of two parts (usually a shaft and a bearing housing) and to ensure that they rotate freely while transmitting the load between them. At high rotational speeds (for example in gyro ball bearings), this use can be expanded to include free rotation with virtually no wear in the bearing. To achieve this state, the two parts of the bearing can be separated by a layer of adhesive fluid called an elastomeric hydrodynamic lubricating film. Denhardt (1966) pointed out that elasticity can be maintained not only when the bearing is subjected to a load on the shaft, but also when the bearing is subjected to pretension so that the positioning accuracy and stability of the shaft do not exceed 1 micro-inch or 1 nano-inch. Hydrodynamic lubrication film。
Ball bearings are used in various machines and equipment with rotating parts. Designers often decide whether ball bearings or fluid film bearings should be used in specific applications. The following features make ball bearings more desirable than fluid film bearings in many situations.
1. The starting friction is small and the working friction is suitable.
2. Can withstand radial and axial joint loads.
8. Not sensitive to the interruption of lubrication.
4. No self-induced instability.
5. Cold start is easy.
Within a reasonable range, changing the load, speed, and operating temperature has only a small effect on the good performance of the ball bearings.
The following features make ball bearings less desirable than fluid film bearings.
1. Limited changes in fatigue life.
2. The required radial space is large.
3. Low damping capability.
I. The noise level is high. ·
6. The stricter requirement for the middle.
6. higher cost.
According to the above characteristics, a piston film engine generally employs a fluid film bearing, and a jet engine almost exclusively uses a ball bearing. Various types of bearings have their own unique advantages. In a given application, the most suitable bearing type should be carefully selected. The British Engineering Scientific Data Organization (ESDU 1965, 1967) has provided useful guidelines for selecting important bearings.