Development of a Shrink Fitter for Ceramics Bearings

采用6204型Si_3N_4陶瓷球轴承，研究了新型机械元件收缩滤器对轴承寿命的影响。轴和外壳由高铬钢SUJ2制成。陶瓷轴承保持架的材质为不锈钢，SUS304。两种油被用作润滑剂。一台测试机器的转速为每分钟7000转。陶瓷轴承和金属轴之间以及陶瓷和金属外壳之间的干涉在高温下会增加或减少，因为它们的热膨胀系数彼此不同。陶瓷轴承和金属外壳之间的间隙可以认为引起轴承外圈的大弯矩并导致外圈失效。如果在轴承和外壳之间的界面处放置铝合金A2017收缩滤芯，即使在高温下也不会出现这种间隙，因为收缩滤芯的热膨胀足够。因此，缩短轴承寿命的外圈弯矩将永远不存在。通过实验验证了收缩滤芯对轴承寿命的影响。安装了收缩滤芯的陶瓷轴承寿命比未安装收缩滤芯的陶瓷轴承寿命更长。

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.