Rolling bearing structures and types
Rolling bearings (bearings hereinafter) normally comprise bearing rings, rolling elements and a cage (see Fig. 1-1). Rolling elements are arranged between inner and outer rings with a cage, which retains the rolling elements in correct relative position, so they do not touch one another. With this structure, a smooth rolling motion is realized during operation. Bearings are classified as follows, by the number of rows of rolling elements: singlerow, double-row, or multi-row (triple- or fourrow) bearings.
Note) In thrust bearings inner and outer rings and also called "shaft washer" and "housing washer" respectively; in tapered roller bearings, the respective forms are "cone"and "cup."
1) Bearing rings
The path of the rolling elements is called the raceway; and, the section of the bearing rings where the elements roll is called the raceway surface. In the case of ball bearings, since grooves are provided for the balls, they are also referred to as raceway grooves. The inner ring is normally engaged with a shaft; and, the outer ring with a housing
2) Rolling element
Rolling elements may be either balls or rollers. Many types of bearings with various shapes of rollers are available.
The cage guides the rolling elements along the bearing rings, retaining the rolling elements in correct relative position. There are various types of cages including pressed, machined, molded, and pin type cages. Due to lower friction resistance than that found in full complement roller and ball bearings, bearings with a cage are more suitable for use under high speed rotation.
The contact angle (α) is the angle formed by the direction of the load applied to the bearing rings and rolling elements, and a plan perpendicular to the shaft center, when the bearing is loaded.
Bearings are classified into two types in accordance with the contact angle (α).
• Radial bearings (0˚ ≤ α ≤ 45˚) ... designed to accommodate mainly radial load.
• Thrust bearings (45˚ < α ≤ 90˚) ... designed to accommodate mainly axial load.
Rolling bearings are classified in following drawing