Tripot Joint Retainer Structure for Cyclic Load Durability

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Solution Overview

Problem

Constant velocity joints, particularly tripot joints, are prone to fracturing roller or ring retainers under high torque durability tests due to cyclic loads causing fatigue, which existing designs fail to adequately address.

Innovation Solution

A tripot joint design featuring a single, unitary retainer ring and cap structure that consolidates components to support higher cyclic loads, and a method to determine the shape of trunnions using parametric equations for improved load distribution, reducing the risk of retainer fracture and enhancing durability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If existing retainer designs are used in constant velocity joints, then the device complexity is lower, but the reliability deteriorates due to retainer fracture under high torque durability tests

Engineering Contradiction:

Improveretainer durabilityVSAvoidretainer structure complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent merges the retainer and cap into a single unitary structure, eliminating the need for separate retainers and caps. This consolidation reduces the number of parts and assembly steps while improving reliability by eliminating potential failure points at connection interfaces between separate components.

Inventive Principle:

Principle #5Merging (Combining)

2Strength

If traditional multi-component retainer designs are used, then the ease of manufacture is better, but the strength deteriorates under cyclic loads

Engineering Contradiction:

Improveretainer load capacityVSAvoidmanufacturing complexity

Core Design Contradiction:

StrengthVSEase of manufacture

Solution Approach 1:

By combining multiple components into a single unitary retainer structure, the patent improves strength under cyclic loads by eliminating weak connection points between separate parts. The unitary construction allows for optimized load paths and uniform material properties throughout the structure.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent employs parametric equations to define the trunnion shape, allowing optimization of geometric parameters to improve load distribution and stress characteristics. This enables the retainer structure to better withstand cyclic loads while maintaining manufacturability through standardized forming processes.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If existing retainer designs are used, then the productivity is maintained, but the reliability deteriorates due to fatigue failure

Engineering Contradiction:

Improveservice lifeVSAvoidcomponent integration

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The consolidation of retainer and cap into one unitary component improves reliability by eliminating fatigue failure points at interfaces between separate parts. The integrated structure reduces the total number of potential failure locations while enhancing overall component life.

Inventive Principle:

Principle #5Merging (Combining)

Data Source

PatentUS11585388B2Needle retainer for constant velocity joint and method of determining trunnion shape

Publication Date: 2023.02.21 STEERING SOLUTIONS IP HOLDING CORP

AI summary

A constant velocity joint includes a trunnion extending radially outwardly about a trunnion axis. The joint also includes a ball surrounding the trunnion and rotatable relative thereto about a plurality of needle rollers. The joint further includes a retainer that is a single, unitary structure coupled to the trunnion and positioned to limit movement of the ball and the needle rollers in a direction parallel to the trunnion axis.