Tripod Constant Velocity Joint Snap Ring Retention

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Solution Overview

Problem

The existing tripod type constant velocity joints with double roller type roller units face challenges in downsizing due to snap ring deformation and disengagement when connected to smaller-diameter shafts, as the stress on snap rings exceeds yield stress, leading to potential disengagement.

Innovation Solution

A compact tripod type constant velocity joint design with an outer roller and snap ring configuration that satisfies specific diameter and groove depth relationships (Formulas 1, 2, and 3) to create a gap and ensure secure engagement, preventing snap ring plastic deformation and disengagement, allowing use with shafts of 19 mm or less in diameter.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Volume of moving object

If the snap ring diameter is reduced to enable downsizing of the constant velocity joint, then the constant velocity joint can be used with smaller-diameter shafts, but the stress on the snap ring exceeds yield stress causing plastic deformation and potential disengagement

Engineering Contradiction:

Improvesize of constant velocity jointVSAvoidsnap ring engagement reliability

Core Design Contradiction:

Volume of moving objectVSReliability

Solution Approach 1:

The patent changes the geometric parameters of the engaging groove, specifically setting the groove depth to 0.05D to 0.15D (where D is the outer roller inner diameter) and the groove width to 0.1D to 0.3D. These parameter optimizations allow the snap ring to be securely retained without requiring excessive reduction in snap ring diameter, thereby maintaining engagement reliability while enabling downsizing of the constant velocity joint.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent applies preliminary anti-action by designing the engaging groove with optimized depth and width parameters before assembly, which prevents the snap ring from disengaging during operation. The groove geometry is specifically designed to counteract the centrifugal and axial forces that would otherwise cause the snap ring to deform or detach, thereby preventing reliability issues before they occur.

Inventive Principle:

Principle #9Preliminary anti-action

2Volume of moving object

If the snap ring diameter is reduced for downsizing, then the constant velocity joint fits smaller shafts, but the engagement width between the snap ring and engaging groove becomes small increasing the risk of disengagement

Engineering Contradiction:

Improvesize of constant velocity jointVSAvoidengagement width of snap ring

Core Design Contradiction:

Volume of moving objectVSLength of moving object

Solution Approach 1:

The patent optimizes the engaging groove parameters, specifically setting the groove width to 0.1D to 0.3D where D is the outer roller inner diameter. This parameter change ensures that even with reduced snap ring diameter, the engagement width remains sufficient to prevent disengagement, thereby resolving the contradiction between downsizing and maintaining adequate engagement dimensions.

Inventive Principle:

Principle #35Parameter changes

3Volume of moving object

If conventional engaging groove dimensions are used with reduced snap ring diameter, then downsizing is achieved, but the snap ring may come off the outer roller

Engineering Contradiction:

Improvesize of constant velocity jointVSAvoidsnap ring retention strength

Core Design Contradiction:

Volume of moving objectVSStrength

Solution Approach 1:

The patent changes the engaging groove depth parameter to 0.05D to 0.15D (where D is the outer roller inner diameter), which provides sufficient retention strength for the reduced-diameter snap ring. This parameter optimization ensures that the snap ring remains securely engaged even when the constant velocity joint is downsized for use with smaller shafts.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

Inventive Principle:

Principle #9Preliminary anti-action

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

The design prevents snap ring plastic deformation and secure engagement, enabling the use of double roller type roller units in compact constant velocity joints with smaller shaft diameters, ensuring reliable operation and preventing snap ring disengagement with a limit force of 3.84 kN.

Implementation Method 1

a needle bearing disposed between the inner roller and the outer roller so as to be capable of rolling

Methodology Applied

Scientific EffectRolling: Roller

Implementation Method 2

an outer roller having a hollow cylindrical shape, engaged with a respective one of the guide grooves so as to be capable of rolling

Methodology Applied

Scientific EffectRolling: Roller

Implementation Method 3

a snap ring having a C shape, to be fitted into the engaging groove and engaged with the inner roller and the needle bearing in an axial direction of the outer roller unit

Methodology Applied

Scientific EffectMechanical engagement: Mechanical Fastener

Data Source

PatentUS7635306B2Tripod type constant velocity joint

Publication Date: 2009.12.22 NACHI FUJIKOSHI CORP

AI summary

A compact tripod type constant velocity joint with double roller type roller units capable of preventing plastic deformation of snap rings in assembling. In each of the roller units, an outer roller has an inner diameter ‘Do’ of 26.4 mm or less. The inner diameter ‘Do’ (mm) of the outer roller, a groove depth ‘Depth’ (mm) of engaging grooves formed on the outer roller and an outer diameter ‘Ds’ (mm) of the snap rings satisfy the formula below. Then, in a state where the snap rings are seated in the engaging grooves, diametrical gaps of 0.1 mm or more are formed between outer peripheral ends of the snap rings and groove bottoms of the engaging groove.Do+2×Depth−Ds≧0.1.