Constant Velocity Joint Cage Structure for Easier Ball Assembly

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Solution Overview

Problem

The existing constant velocity universal joints face challenges in maintaining strength and ease of assembly, particularly under high load and high-speed rotation, due to increased circumferential moving amounts of balls which lead to reduced cage strength and longer pocket circumferential lengths, complicating ball assembly and potentially causing interference during assembly.

Innovation Solution

A fixed-type constant velocity universal joint design with eight track grooves on both the outer and inner joint members, where the track grooves are inclined opposite to each other, allowing for alternate wedge angles and reduced pocket lengths, enabling simultaneous assembly of two balls at a time, thus stabilizing the cage position and reducing assembly complexity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the number of balls is increased to eight and track grooves are inclined to improve load capacity and durability, then the circumferential moving amounts of balls increase, but this leads to reduced cage strength and longer pocket circumferential lengths

Engineering Contradiction:
ImprovedurabilityVSAvoidcage strength
Core Design Contradiction:
ReliabilityVSStrength

Solution Approach 1:

The cage is designed to be tiltable relative to the outer joint member, allowing dynamic adjustment of the cage's orientation. This tilting capability enables the pocket circumferential lengths to be effectively reduced while accommodating the increased ball movement, thereby maintaining cage strength despite the higher number of balls and improved durability requirements

Inventive Principle:
Principle #15Dynamics

2Reliability

If the pocket circumferential lengths are increased to accommodate larger ball moving amounts, then ball assembly becomes more difficult, but this also complicates the assembly process and increases interference risk

Engineering Contradiction:
Improveoperational smoothnessVSAvoidease of assembly
Core Design Contradiction:
ReliabilityVSEase of manufacture

Solution Approach 1:

The tiltable cage design allows the pockets to be positioned optimally during assembly. By tilting the cage, the effective pocket circumferential length is reduced, creating easier access for ball assembly and reducing interference, while still accommodating the operational requirements for smooth operation

Inventive Principle:
Principle #15Dynamics

Solution Approach 2:

The cage is pre-designed with specific tilting capability and pocket configuration that facilitates easier ball assembly before the joint is fully assembled. This preliminary design consideration allows workers to assemble balls more easily by utilizing the cage's tilting feature

Inventive Principle:
Principle #10Preliminary action

3Reliability

If the cage structure is strengthened to support high load and high-speed rotation, then durability improves, but this increases the overall size and weight of the joint

Engineering Contradiction:
ImprovedurabilityVSAvoidjoint weight
Core Design Contradiction:
ReliabilityVSWeight of moving object

Solution Approach 1:

The tiltable cage design allows for a more efficient structural configuration that provides necessary strength for high load and high-speed rotation without requiring excessive material. The dynamic tilting capability enables optimal force distribution, allowing for weight reduction while maintaining durability

Inventive Principle:
Principle #15Dynamics

Data Source

PatentEP2716925B1Constant velocity universal joint
Publication Date: 2024.01.17 NTN CORP
  • EP2716925B1 patent drawingFigure 1~2
  • EP2716925B1 patent drawingFigure 3~4
  • EP2716925B1 patent drawingFigure 5~6

AI summary

Provided is a constant velocity universal joint capable of performing smooth operation even under load and in high speed rotation, and also capable of suppressing heat generation and enhancing durability, specifically, a fixed type constant velocity universal joint capable of increasing easiness of ball assembly and enhancing cage strength. An offset in an axial direction between a center of curvature of each of track grooves (22) of an outer joint member (23) and a center of curvature of an inner surface (21) of the outer joint member (23), and an offset in the axial direction between a center of curvature of each of track grooves (25) of an inner joint member (26) and a center of curvature of an outer surface (24) of the inner joint member (26) are each set to zero. The track grooves (22) of the outer joint member (23) and the track grooves (25) of the inner joint member (26) are each inclined with respect to an axial line. A circumferential length of each of pockets (28) of a cage (29) is set so that two of the pockets (28) allow balls to be assembled therein at one time under a state in which the two of the pockets (28) are exposed from the outer joint member (23) through inclination of the cage (29) at a predetermined angle.