Development of a Shrink Fitter for Ceramics Bearings

以6204型Si3N4陶瓷球轴承为研究对象，考察了新型机械元件--热套对轴承寿命的影响。轴和外壳由高铬钢SUJ2制造。陶瓷轴承保持架材质为SUS304不锈钢。使用了两种油作为润滑剂。试验机的转速为每分钟7000转，陶瓷轴承与金属轴、陶瓷与金属壳体之间的干涉随着温度的升高而增大或减小，因为它们的热膨胀系数不同。陶瓷轴承和金属轴承座之间的间隙可能会导致轴承外圈的较大弯矩，导致外圈失效。如果将铝合金热配合件A2017放置在轴承和轴承座之间的界面上，则即使在高温下也不会出现这种间隙，因为热配合件有足够的热膨胀。因此，外圈弯矩是不存在的，它缩短了轴承的寿命。我们从实验上证实了缩套对轴承寿命的影响。陶瓷轴承有过热配合后的寿命比无过热过盈的寿命长。

All ceramic ball bearings of Si_3N_4, type 6204, were used to examine an effects of a shrink fitter, a new machine element, on the bearing life. The shaft and the housing were made of a high Cr steel, SUJ2. The material of the cage of the ceramic bearing was stainless steel, SUS304. Two kinds of oils were used as lubricants. A rotational speed of a test machine was 7,000 rpm.The interferences between the ceramic bearing and a metal shaft, and between the ceramic and a metal housing, will increase and decrease at elevated temperature, since their coefficient of thermal expansions are different from each other. The interstice between the ceramic bearing and the metal housing can be thought to cause a large bending moment of the outer race of the bearing and lead to a failure of the outer race. If the shrink fitter of aluminum alloy, A2017, is placed at the interface between the bearing and the housing, such interstice will never appear even at the elevated temperature, because of the sufficient thermal expansion of the shrink fitter. Therefore the bending moment of the outer race, which shorten the bearing life will never exist.We confirmed the effect of the shrink fitter on the bearing life experimentally. The life of the ceramic bearing with the shrink fitter was longer than that without the shrink fitter.