Constant-Velocity Joint Chamfered Groove Inlets for Stronger Cage Windows

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Solution Overview

Problem

In fixed type constant velocity universal joints with eight balls, the axial offset of track groove curvature centers is set to 0, leading to increased forces and stresses on cage window columns due to the inclination of adjacent track grooves, which degrades the strength and assembly workability of the joint.

Innovation Solution

The formation of chamfered portions on the track inlet ends of the outer joint member's track grooves increases the space required for ball incorporation, reduces the inclination angles of internal components, and shortens the length of cage windows, thereby enhancing the strength and assembly workability of the joint.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If axial offset amounts of track groove curvature centers are set to 0 and adjacent track grooves are inclined, then the joint achieves constant velocity transmission, but large forces and stresses are applied to the cage window columns, degrading the strength and assembly workability

Engineering Contradiction:
Improveconstant velocity transmissionVSAvoidcage window column strength
Core Design Contradiction:
ReliabilityVSStrength

Solution Approach 1:

The patent introduces axial offset amounts between the curvature centers of track grooves, changing the geometric parameters of the joint. This offset creates a non-zero distance between curvature centers, which modifies the force distribution and reduces the pressing forces on cage window columns while maintaining constant velocity transmission capability

Inventive Principle:
Principle #35Parameter changes

Solution Approach 2:

The patent adds a new dimensional parameter (axial offset distance) to the traditional design where curvature centers were coincident. By introducing this offset in the axial dimension, the force distribution is improved without compromising the constant velocity function

Inventive Principle:
Principle #17Another dimension (Dimensionality change)

2Reliability

If axial offset amounts of track groove curvature centers are set to 0 and adjacent track grooves are inclined, then the joint achieves constant velocity transmission, but the assembly workability is degraded due to difficult ball incorporation

Engineering Contradiction:
Improveconstant velocity transmissionVSAvoidassembly workability
Core Design Contradiction:
ReliabilityVSEase of manufacture

Solution Approach 1:

By changing the axial offset parameter of track groove curvature centers, the patent creates more favorable geometric conditions for ball incorporation during assembly, making the manufacturing process easier while maintaining constant velocity transmission

Inventive Principle:
Principle #35Parameter changes

3Ease of manufacture

If the length of cage windows is increased to accommodate ball movement, then the assembly workability is improved, but the strength of cage window columns is reduced

Engineering Contradiction:
Improveassembly workabilityVSAvoidcage window column strength
Core Design Contradiction:
Ease of manufactureVSStrength

Solution Approach 1:

The patent optimizes the axial offset parameter to reduce the required cage window length while maintaining adequate space for ball incorporation. This parameter adjustment allows shorter cage windows that preserve strength while still enabling proper assembly

Inventive Principle:
Principle #35Parameter changes

Data Source

PatentEP3418597B1Stationary constant-velocity universal joint
Publication Date: 2025.04.30 NTN CORP
  • EP3418597B1 patent drawingFigure 1~2
  • EP3418597B1 patent drawingFigure 3~4
  • EP3418597B1 patent drawingFigure 5~6

AI summary

In a fixed type constant velocity universal joint, an axial offset amount of a curvature center of each of track grooves of an outer joint member and an axial offset amount of a curvature center of each of track grooves of an inner joint member are set to 0. The track grooves of the outer joint member and the track grooves of the inner joint member are each inclined with respect to an axis line. The track grooves adjacent to each other in a circumferential direction are inclined in opposite directions. The track grooves of the outer joint member and the track grooves of the inner joint member, which are opposed thereto, are inclined with respect to the axis line in opposite directions. A chamfered portion is formed on a track inlet end of each of the track grooves of the outer joint member. In a state in which the cage and the inner joint member are inclined with respect to the outer joint member, balls are enabled to be incorporated into two cage windows at the same time through the chamfered portions on the track inlet ends.