Study on ball bearings with excessive internal clearance (Part 2): influences of internal clearance on fatigue life

摘要

Using a bearing with slit inserted in one place in the axial direction of the outer ring, we attached housing with larger internal diameter than normal to increase the apparent internal clearance, and conducted fatigue life tests in order to study the influences of internal clearance on bearing life. As a result, we learned the following. (1) With the bearings and test conditions used in our study, the life ratio of bearings with clearance of 0 and with increased internal clearance declines virtually in step with the theoretical value for clearances of up to 72μm, but declines much faster than the theoretical value at 135μm or more. (2) The load exponent p in the fatigue life theory for bearings with excessive clearance is larger than the value p = 3 applied in the past, and may possibly reach p = 4～5. (3) While the inner ring was most easily broken in our test, an increased clearance caused an increase in the failure ratio of balls. Finally, we wish to express our gratitude to Chiba University graduate students Takushi Toda (now at R & D Co., Ltd.) and Masanori Chiba (now at Nsk Ltd.) for their cooperation in this test.