Thrust Roller Bearing Cage with Crank-Shaped Bent Portions

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Solution Overview

Problem

Thrust roller bearings with short rollers face issues of rollers coming out of the cage due to inclination under external forces, leading to reduced load capacity and cage fatigue, especially with small roller lengths and narrow pocket dimensions.

Innovation Solution

A thrust roller bearing design featuring a cage with crank-shaped bent portions and precisely formed pockets with inner and outer guiding surfaces and roller retaining pawls, along with chamfered roller ends and rounded pocket corners, to prevent roller ejection and enhance load capacity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Length of moving object

If the roller entire length is reduced to use short rollers, then the bearing size and cost are reduced, but the roller may come out of the cage due to inclination under external forces

Engineering Contradiction:

Improveroller entire lengthVSAvoidroller retention in cage

Core Design Contradiction:

Length of moving objectVSReliability

Solution Approach 1:

The cage is divided into multiple functional regions: the pocket for housing the roller, the roller retaining portion for preventing axial ejection, and the roller end surface guiding surface for guiding roller positioning. This segmentation allows each component to perform its specific function effectively, ensuring reliable roller retention even with short rollers.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The roller end surface guiding surface acts as an intermediary between the roller and the rib inner surface. It guides the roller end surface to contact the rib inner surface at the correct position, preventing roller inclination and ejection while allowing the use of short rollers with reduced chamfers.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Strength

If the roller effective length is increased by reducing chamfer, then the load capacity is increased, but the roller end edges may interfere with the pocket inner corners

Engineering Contradiction:

Improveload capacityVSAvoidinterference between roller end edges and pocket inner corners

Core Design Contradiction:

StrengthVSObject-affected harmful factors

Solution Approach 1:

The harmful interference between roller end edges and pocket inner corners is eliminated by extracting the guiding function into a separate roller end surface guiding surface. This allows the pocket inner corners to be designed with large radius of curvature for fatigue strength without causing interference with the roller end edges.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The roller end surface guiding surface replicates the guiding function that would otherwise require direct contact between the roller end edges and the pocket structure. This copying allows the pocket inner corners to be optimized for fatigue strength while the guiding surface handles the positioning function.

Inventive Principle:

Principle #26Copying

3Strength

If the radius of curvature of pocket inner corners is increased to improve cage fatigue strength, then the cage strength is improved, but the roller retaining portions become narrower and harder to form precisely

Engineering Contradiction:

Improvecage fatigue strengthVSAvoidroller retaining portion formation precision

Core Design Contradiction:

StrengthVSManufacturing precision

Solution Approach 1:

The cage structure is segmented into the pocket region with large radius of curvature for fatigue strength and the roller retaining portion with precise dimensions for roller retention. This segmentation allows each region to be optimized independently: the pocket inner corners can have large radius of curvature while the roller retaining portions can maintain precise dimensions.

Inventive Principle:

Principle #1Segmentation

4Reliability

If the clearance between pocket radial end surface and rib inner surface is minimized to prevent roller ejection, then the roller retention is improved, but the rib pressing process cannot achieve sufficient precision

Engineering Contradiction:

Improveroller retentionVSAvoidclearance control in rib pressing

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The roller end surface guiding surface serves as an intermediary that ensures precise roller positioning and contact with the rib inner surface. It compensates for the clearance control limitations of the rib pressing process by providing a dedicated guiding surface that maintains the correct contact position.

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS7878715B2Thrust roller bearing

Publication Date: 2011.02.01 JTEKT CORP

AI summary

A cage of a thrust roller bearing includes: a pair of crank-shaped bent portions arranged in a circumferential direction of the cage; a pair of inner wall surfaces arranged in a radial direction of the cage; and a pocket for housing a roller defined by the pair of bent portions and the pair of inner wall surfaces and formed by punching the cage. Radially inner one of the inner wall surfaces is formed as a guiding surface for guiding a substantial roller PCD position of an end surface of the roller. Each of the pair of bent portions includes a first extended portion extending in one of cage thickness directions and a second extended portion extending in the other cage thickness direction. A roller retaining pawl for retaining the roller is provided at each of the first and second extended portions so as to protrude into the pockets.