Constant Velocity Universal Joint Cage Insertion and Strength

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Solution Overview

Problem

Conventional fixed constant velocity universal joints experience reduced strength and durability due to interference issues during cage insertion, which compromises the spherical surface angle and inner diameter, leading to decreased torsional fatigue and quasi-static torsional strength at high operating angles.

Innovation Solution

The solution involves retracting one or two frontal sections of the outer member in an outward radial direction to allow cage insertion, maintaining required spherical surface angles and inner diameters in other sections, thereby enhancing joint strength and reducing play.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If the cage is inserted into the outer member by tilting the cage axial line perpendicular to the outer member axial line, then the cage can be inserted, but the spherical surface angle and inner diameter are compromised, reducing joint strength

Engineering Contradiction:
Improvecage insertionVSAvoidjoint strength
Core Design Contradiction:
Ease of operationVSStrength

Solution Approach 1:

The outer member is divided into multiple frontal sections, with specific sections (one or two opposing sections) retracted to create insertion paths for the cage. This segmentation allows the cage to be inserted without compromising the overall spherical surface angle and inner diameter of the outer member, thereby resolving the contradiction between ease of cage insertion and joint strength.

Inventive Principle:
Principle #1Segmentation

2Ease of operation

If frontal sections are retracted to allow cage insertion, then cage insertion is enabled, but the spherical surface area and spherical angle are reduced

Engineering Contradiction:
Improvecage insertionVSAvoidspherical surface area
Core Design Contradiction:
Ease of operationVSArea of stationary object

Solution Approach 1:

Only specific frontal sections (one or two opposing sections) of the outer member are retracted, while other sections maintain their original spherical surface characteristics. This local modification approach allows cage insertion while preserving the majority of the spherical surface area and angle, thus enabling cage insertion without significantly compromising the spherical surface properties.

Inventive Principle:
Principle #3Local quality

3Strength

If the outer member inner diameter is reduced to increase spherical surface angle, then joint strength is improved, but cage insertion becomes difficult

Engineering Contradiction:
Improvejoint strengthVSAvoidcage insertion
Core Design Contradiction:
StrengthVSEase of operation

Solution Approach 1:

The outer member is segmented into multiple frontal sections, with specific sections retracted to create sufficient clearance for cage insertion. This allows the overall inner diameter to remain small (maintaining joint strength) while specific localized sections provide the necessary space for cage insertion, thus resolving the contradiction between joint strength and ease of cage insertion.

Inventive Principle:
Principle #1Segmentation

Data Source

PatentEP2003355B1Fixed uniform motion universal joint
Publication Date: 2015.12.02 NTN CORP
  • EP2003355B1 patent drawingFigure 1A~1B
  • EP2003355B1 patent drawingFigure 2A~2B
  • EP2003355B1 patent drawingFigure 3A~4

AI summary

In a fixed constant velocity universal joint with eight balls, the present invention achieves improvement in cage strength by increasing a smallest outer diameter of a cage and improvement in joint strength at a high operating angle by ensuring required inner spherical area and spherical surface angle in an outer member regardless of the smallest outer diameter of the cage. In the fixed constant velocity joint of the present invention, among eight frontal sections adjacent to an inner spherical surface 12 on an outer member 12 opening side, present between adjacent ball grooves 14 formed on the inner spherical surface 12, and forming a smallest inner diameter øB of an outer member 10 opening, any one or any two mutually opposing frontal sections are retracted from the smallest inner diameter in an outward radius direction by a distance required to allow insertion of the cage through the one or two frontal sections (cylindrical surfaces 16c or planar surfaces 16d) in a state in which a cage axial line is perpendicular to an outer member axial line.