Differences in Rolling Element, Inner Ring, and Outer Ring Guidance for Bearing Retainers

The retainer, as an essential component of bearings, plays a crucial role in guiding and separating the rolling elements. The guidance function of the retainer refers to the correction of the rolling elements' movement, which is achieved through collisions between the retainer and surrounding components. Generally, there are three common types of guidance methods for bearing retainers: rolling element guidance, inner ring guidance, and outer ring guidance.

Rolling Element Guidance:
The standard design for most bearings is rolling element guidance. For example, in short cylindrical roller bearings, rolling element guidance is employed, where the retainer does not come into contact with the inner and outer ring's stop surfaces. This type of retainer can be universally used. However, at higher speeds, instability may occur due to increased rolling element speed. Therefore, rolling element guidance is suitable for medium speeds and moderate loads, such as gear bearings.
In rolling element guidance, the retainer is positioned in the middle of the rolling elements. There is no contact or collision between the retainer and the inner and outer rings. The retainer corrects the movement of the rolling elements through collisions, while keeping the rolling elements separated at equal intervals.

Outer Ring Guidance:
The outer ring is typically stationary, and outer ring guidance facilitates lubrication oil entering the guiding surface and raceway. In high-speed gear bearings, for instance, which use oil mist lubrication, rotating inner ring guidance would squeeze out the oil. In outer ring guidance, the retainer is positioned near the outer ring on one side. During bearing operation, the retainer may collide with the outer ring, thereby correcting its position.
Outer ring guidance is generally used in high-speed and stable load conditions. Taking cylindrical roller bearings as an example, they only bear a fixed axial load, and the rotational speed of each rolling element does not vary significantly, ensuring a balanced rotation of the retainer.

Inner Ring Guidance:
The inner ring is typically a rotating sleeve that provides a dragging torque to the rolling elements during rotation. However, if the bearing load is unstable or light, slippage may occur.
By adopting inner ring guidance, a lubricating oil film is formed on the guiding surface of the retainer. The friction of the oil film provides additional driving torque to the retainer from the non-loaded area of the inner ring, preventing slippage.
In inner ring guidance, the retainer is positioned near the inner ring of the rolling elements. During bearing operation, the retainer may collide with the inner ring, thereby correcting its position.

The three types of retainer guidance methods can be found in different types of bearings, influenced by performance requirements as well as the design and manufacturing of the bearings themselves. Engineers can choose the appropriate guidance method based on specific needs.

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