SKF轴承知识培训.ppt

Bearing Basics 1 - * Types of Rotation ? It is very important to establish the type of rotation, i.e. which ring rotates and which is stationary, as this defines what type of fit is required for each ring. To prevent creep, which can be very damaging to the bearing and the shaft or housing, the rotating ring requires an interference fit, the stationary one a transition or “loose” fit. For vibration applications and out of balance loads, the stationary ring can also require an interference fit. This type of application is referred to as “direction of rotation indeterminate.” ? The radial location of the bearing rings is extremely important to the performance of the bearing. The rings are relatively thin and without proper support from the shaft and housing will distort and result in early failure. Bearing Basics 1 - * Effect of Loose Fit ? The effect of only a 0,01 mm clearance between shaft and inner ring bore can be very significant in a rotating inner ring application. Assuming that there is no wear – which would increase the effect – a relative movement of approximately 2 kilometers will occur over 30 days in the example given. In practice, wear would occur, and the movement increase proportionally. Bearing Basics 1 - * Axial Location of Rolling Bearings Axial location of the shaft must be achieved in all bearing arrangements. This is usually done by axially fixing one bearing, and allowing axial freedom to the other bearing(s). This is to allow for changes in length of the shaft caused by thermal expansion or contraction. In some applications this expansion is accommodated by the type of bearings used; for example, cylindrical roller bearings. Often the bearing outer ring is a loose or transition fit to allow the complete bearing to move axially as required. This is another important reason why the correct fit must be used. Bearing Basics 1 - * Axial Freedom in a Fan ? This fan is a good practical example of the how the requirement for axial freedom in the