1、Lesson8Rolling BearingsRolling bearings can carry radial, thrust or combination of the two loads. Accordingly, most rolling bearings are categorized in one of the three groups: radial bearings for carrying loads that are primarily radial, thrust bearings for supportin
2、g loads that are primarily axial, and angular contact bearings or tapered roller bearings for carrying combined radial and axial loads. Figure 8.1a shows a common single-row, deep groove ball bearing. The bearing consists of an inner ring, an outer ring, the balls an
3、d the separator. To increase the contact area and. hence permit larger loads to be carried, the balls run in curvilinear grooves in the rings called raceway. The radius of the raceway is very little larger than the radius of the ball. This type of bearing can stand a
4、radial load as well as some thrust load. Some other types of rolling bearings are shown in Figs. 8. 1b, 8. lc and 8. 1d.Figure8.1Sometype:ofrollingbearings:(a)deepgrooveballbearing;(b)thrustballbearing;(c)taperedrollerthrustbearing;(d)needlerollerbearing. The concern
5、of a machine designer with ball and roller bearings is fivefold as follows: (a) life in relation to load; (b) stiffness, i. e. deflections under load; (c) friction; (d) wear; (e) noise. For moderate loads and speeds the correct selection of a standard bearing on the ba
6、sis of load rating will usually secure satisfactory performance. The deflection of the bearing elements will become important where loads are high, although this is usually of less magnitude than that of the shafts or other components associated with the bearing. Wher
7、e speeds are high special cooling arrangements become necessary which may increase frictional drag. Wear is primarily associated with the introduction of contaminants, and sealing arrangements must be chosen with regard to the hostility of the environment. Because the
8、 high quality and low price of ball and roller bearings depends on quantity production, the task of the machine desig
