tailieunhanh - Bearing Design in Machinery Episode 3 Part 4

Tham khảo tài liệu 'bearing design in machinery episode 3 part 4', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | the bearings. The first type of an adjustable bearing arrangement is shown in Fig 13-8. In this arrangement the apex points A are outside the two bearings. As shown in Fig. 13-8 tightening a threaded ring on the housing side does the adjustment. In this way the bearing cup outer ring is shifted in the axial direction and thus the clearance in the two bearings can be adjusted. In this arrangement a temperature rise will always result in a tighter bearing clearance. In the bearing arrangement of Figs. 13-8a and 13-8b if the bearings are preloaded when the machine is cold the temperature rise results in a higher bearing preload and rolling contact stresses. If some bearing clearance is left after the adjustment the clearance will be reduced due to the thermal expansion. As discussed earlier the advantage of this arrangement type is that it can be designed to allow a final adjustment during operation after the machine has reached a steady thermal equilibrium. Apex points between the two bearings This arrangement is often referred to as O arrangement because the lines in the direction normal to the contact lines intersecting at point S form an O shape. These lines are the directions of the forces acting on the rolling element. In angular contact ball bearings see Fig. 13-9d these lines form the contact angle. In general arrangement of apex points between the two bearings O arrangement is preferred whenever a strong axial guidance is required. This means that the shaft is supported more rigidly than the adjustable arrangement with apex points outside the bearings. The direction of the rolling-elements reaction force resists better any rotational vibrations of the shaft around an axis perpendicular to the shaft centerline. The effect of a temperature rise may be different in the second arrangement type which is shown in Figs. 13-9a 13-9b and 13-9c where the apex points are between the bearings. As shown in these figures tightening a nut on the shaft side does .