The most widely used bearings in electric motors are rolling bearings. Rolling bearings are a standardized component with the advantages of low friction, easy starting and simple replacement. When we are engaged in daily maintenance or mechanical design, reasonable and correct selection of bearing fit is crucial. Influence of rolling bearing with the selection of many factors, in the choice of fit, must be a combination of various factors to consider, and combined with the actual work of the analogical method, in order to achieve the best fit state.
Correct selection of advanced bearings for electric compressors fit, to ensure the normal operation of the motor, improve the service life of the bearing and full use of the bearing capacity of the relationship is great. Rolling bearing with the choice is mainly based on the nature and size of the load bearing collar, and combined with the type of bearing, size, working conditions, shaft and shell material and structure and working temperature and other factors to consider.
A major key factor affecting the operation of the advanced bearings for electric compressors is the working clearance of the bearing, the main factors affecting the working clearance of the bearing include the inter-axial inner ring and shaft fit, bearing outer ring and bearing chamber fit, bearing non-assembly conditions under its own clearance, motor operating conditions and turnover environment and other objective factors. The same a motor, in different conditions of use may have a different fate, to ensure that the motor operation process bearing guarantee effect, should be from the selection of bearings, with the relationship between the determination of the working conditions to understand, lubrication and maintenance and other aspects of a comprehensive consideration.
Whether the advanced bearings for electric compressors rings are rotating or not
When the inner or outer ring bearing work for the rotating circle, should be used slightly tight with the size of the surplus should be so that the surface in the working load does not occur “crawl” (customarily known as running), because once crawling, with the surface to be worn to produce sliding, the higher the speed of the ring, the more serious the wear and tear.
The higher the speed of the ring, the more serious the wear. Bearing work, if the inner ring or outer ring for the non-rotating ring, in order to disassemble and adjust the convenience, it is appropriate to use a loose fit.
As a result of different operating temperature rise, will make the journal or shell hole in the longitudinal direction to produce a different amount of elongation. Therefore, when selecting the fit, in order to achieve the advanced bearings for electric compressors along the axial direction can move freely, eliminate the support of internal stress as the principle. But too large a gap will reduce the rigidity of the whole part, cause vibration and increase wear.
Bearing load types and fit relationships
Advanced bearings for electric compressors collar to bear radial load, according to the load and collar relative motion relationship can be divided into the following three types.
Local load – local load is the role of the bearing on the synthetic radial load and the collar relative stationary, that is, the radial load by the collar of the local raceway bear.
Circular load – circular load refers to the role of the bearing on the synthetic radial load and the collar relative rotation, that is, the radial load in turn on the entire circumference of the raceway of the collar.
Oscillating load – Oscillating load refers to the role of the bearing on the synthetic radial load and the collar in a certain area relative to the swing, advanced bearings for electric compressors bear a directionally invariant radial load and a rotational load, their synthetic radial load in the fixed collar of a section of the raceway relative to the swing.
Bear local load rings should be selected loose transition fit or clearance smaller fit, so that the friction torque between the ring raceway to drive the ring transposition, so that the ring force uniformity, prolonging the service life of the bearing. Withstand cyclic loads of the collar should be selected with the interference fit or tighter transition fit, the size of the surplus, in order not to make the collar and shaft or shell hole with the surface of the phenomenon of crawling as a principle. Withstand swing load, the requirements of its fit and cyclic load or slightly looser.
Advanced bearings for electric compressors load size and fit relationship
Bearing collar and journal and shell with the minimum interference depends on the size of the load. Withstand shock load or heavy load of the collar, easy to produce deformation, so that with the surface force is not uniform, cause with loose, therefore should choose a tighter fit, that is, the minimum amount of interference should be greater; bear light load of the collar, should choose a looser fit.
Impact of other factors on fit
- Working temperature – advanced bearings for electric compressors work, due to friction heat and other heat sources, the temperature of the collar is higher than the temperature of its mating parts. The thermal expansion of the inner ring will cause it to loosen with the journal of the fit, while the thermal expansion of the outer ring will cause it to tighten with the shell hole of the fit. Therefore, when the operating temperature of the bearing is high, the selected fit should be adjusted appropriately.
- Rotational accuracy and rotational speed – for bear load and require high rotational accuracy of the bearing, in order to eliminate the impact of elastic deformation and vibration, should avoid the use of clearance fit. For some precision machine tool light load bearings, in order to avoid and shaft shape error on the bearing accuracy, often with clearance fit. It is generally believed that the higher the rotational speed of the bearing, the tighter the fit should be.
- Installation and dismantling of bearings conditions – consider the convenience of advanced bearings for electric compressors installation and dismantling, it is appropriate to use the looser fit, for heavy machinery with large and extra-large bearings, this is particularly important. Such as the requirements of easy mounting and dismounting and the need for a tight fit, can be used to separate the type of bearing, or the inner ring with a tapered hole, with a tight sleeve and unloading groove bearings.