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The Brief introduction of Ball Bearing

wallpapers Resource 2020-05-07

 

Ball-bearing is a kind of rolling bearing, ball installed in the middle of the inner ring and the outer ring, can withstand a large load.

Structural Composition

Ball bearings are mainly composed of four basic elements: ball, inner ring, outer ring and cage, also known as cage or retainer. General industrial ball bearings meet AISI 52100 standards. Ball bearings and rings are usually made of high chromium steel with Rockwell c-scale hardness of about 61-65. The hardness of the retainer is lower than that of the ball and ring, and its materials are metal (such as medium carbon steel, aluminum alloy) or non-metal (such as Teflon, PTEF, polymer material). The rotational friction resistance of ball bearing is smaller than that of journal bearing, so the temperature generated by friction will be lower at the same rotational speed.

The purpose of ball bearings is to determine the relative position of two parts (usually the shaft and the bearing housing) and to ensure their free rotation while transferring the load between them. At high speeds (for example in gyro ball bearings) this use can be extended to include free rotation with little wear in the bearings. To achieve this state, the two parts of the bearing may be separated by an adhesive fluid film called an elastohydrodynamic lubrication film. Denhard (1966) pointed out that 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 micro-inch or 1 nano-inch.

Ball bearings are used in a variety of machines and equipment with rotary parts. Designers often have to decide whether to use ball bearings or fluid film bearings for specific applications. The following characteristics make ball bearings more desirable than fluid film bearings in many cases,

  1. Small starting friction and suitable working friction.
  2. Able to withstand the combined radial and axial loads.
  3. Not sensitive to interruption of lubrication.
  4. No self-excited instability.
  5. Easy to work at low temperatures.

Within a reasonable range, changes in load, speed and operating temperature have only a small impact on the good performance of ball bearings.

Advantage

(1) in general working conditions, the friction coefficient of rolling bearing is small and will not change with the change of friction coefficient, which is relatively stable; Small starting and running torque, small power loss, high efficiency.

(2) the radial clearance of the rolling bearing is small and can be eliminated by the method of axial preload, so the operation accuracy is high.

(3) the axial width of rolling bearings is small, and some bearings bear the combined load of radial and axial direction at the same time, with compact structure and simple combination.

(4) the rolling bearing is a standardized part with a high degree of standardization and can be produced in batches, so the cost is low.

Disadvantage

(1) the small contact area between rolling bearing and pipe, especially ball bearing, poor impact resistance.

(2) due to the structural characteristics of the rolling bearing, the radial clearance is relatively large, resulting in greater vibration and noise.

(3) under the condition of high speed and heavy load, the service life of the rolling bearing is reduced.

(4) the inner and outer rings of the rolling bearing adopt an integral structure, and part structure cannot be adopted, which makes it difficult to install the bearing in the middle of the long shaft.


you might interested in the relevant topics as follow:
Application Of High-Precision Bearings
The Introduction of Roller Bearings


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Tag: Ball Bearing