10Rolling Element Bearings

10.1 Introduction

10.1.1 Definition

A rolling element bearing facilitates rotary motion between two mechanical elements. Specifically, it uses rolling elements between two races to carry the bearing load and allow motion with low friction and wear. A rolling element bearing is different from a sleeve bearing, where two components rotate relative to each other without rolling elements, instead separated by lubricant.

10.1.2 Terminology and Geometry

Figure 10.1 shows an isometric view of a rolling element bearing, identifying its components. A rolling element bearing typically comprises an outer ring and an inner ring, with rolling elements in between. The contact surfaces between the rolling elements and the inner and outer ring are the inner and outer races. The rolling elements maintain a uniform spatial distribution along the perimeter of the bearing by means of a separator, i.e. a cage‐like structure that maintains the spacing between the different rolling elements. Often, rolling element bearings are sealed, i.e. a seal is integrated between the inner and outer ring, which prevents dirt from entering the bearing and acting as a third‐body abrasive between the rolling elements and the races, thus accelerating wear and, ultimately, failure. Furthermore, the seal prevents bearing grease to leave the bearing, again contributing to reducing failure.

We characterize the geometry of a rolling element bearing by its inner diameter because this dimension ...

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