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In order to prolong rolling bearing fatigue life under mixed or boundary lubrication conditions, we have developed a specific smooth surface with small indentations by using the concept of micro EHL (elastohydrodynamic lubrication). These indentations or pits act as a carrier of lubricant from the inlet to the inside of the contact area. Therefore, lubrication performance of this surface is better than that of a superfinished surface. We have already demonstrated the ability of forming an oil film using this proposed surface. However, reliability of fatigue life for this surface was not sufficiently investigated. Therefore, we have conducted several rolling bearing fatigue life tests with this surface as compared to a superfinished surface. Lambda values of these tests were from 0.45 to 2.10. Results of these tests indicated that the life of the bearings containing rollers with this surface texture was between 2.0 to 13 times longer than that of normal bearings.

There has not been any established theory regarding the behavior of needle roller bearings used for idler gears in transmission or transfer case applications. This type of bearing tends to produce loud noises because they generate self-exciting vibration when certain operating conditions (such as temperature, relative number of revolutions of the gear and shaft, etc.) are overlapped and when the resonant vibration of the gear-shaft series coincides with that of the housing series. The theory introduced here shows the analysis of the behavior of an idler needle roller bearing itself while an experimental verification of the mechanism to oroduce noises is also attempted.