① When the load is small and stable, roller bearings should be used.
② When the bearing only bears radial load, centripetal ball bearing or centripetal short cylindrical roller bearing can be selected; When the bearing only bears axial load, thrust ball bearing can be selected.
③ When the bearing is subjected to both axial load and radial load, it shall be considered according to the relative value of axial load a and radial load R.
A when a is much smaller than R, radial ball bearing can be selected.
B when a < R, radial thrust ball bearing or tapered roller bearing shall be selected.
C when a > R, radial thrust ball bearing with large contact angle and tapered roller bearing with large cone angle can be selected.
D when a is much larger than R, thrust bearing and radial bearing can be combined to bear axial and radial loads respectively.
1. When the size and accuracy are the same, the limit of the ball bearing is higher than that of the roller bearing, so the ball bearing is easy to be used on the shaft with high speed.
2. For high-speed shaft with large axial load, it is better to select centripetal thrust ball bearing rather than thrust ball bearing. Due to the large centrifugal force of the rolling element at high speed, the working conditions of the bearing will deteriorate.
C. special requirements for bearings
If the radial dimension of the component is limited and the radial load is large, needle roller bearing shall be selected.
The bearing with ordinary structure is cheaper than that with special structure; Ball bearings are cheaper than cylindrical or tapered roller bearings; Spherical roller bearings are expensive. As long as the basic requirements are met, spherical bearings shall be selected as far as possible. When selecting the accuracy grade of bearing, generally use the ordinary grade as far as possible.
(1) Installation and disassembly of rolling bearing
Because the inner ring of general bearing fits tightly with the journal, during installation, large-size bearing can be pressed on the inner ring by a press to make it tightly sleeved on the journal. Medium and small size bearings can be installed with hammer and sleeve. In order to improve the assembly quality, the bearing can be installed on the journal after heating in hot oil by means of hot sleeve and using the phenomenon of thermal expansion and cold contraction. In order to facilitate disassembly, enough height shall be reserved for the inner ring on the shaft shoulder and the outer ring in the sleeve for placing the hook head of the disassembly tool.