CV Joint Cassette Assembly Using Cage Gripping and Orthogonal Rotation

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Solution Overview

Problem

The fixed type constant velocity universal joint faces assembly failures due to positional deviation of the cage and inner joint member, particularly when the diameter of the reference ball is smaller than the pocket width, leading to potential ball dislodgment and interference with the outer joint member during assembly.

Innovation Solution

An automatic assembly method that includes gripping the inner peripheral surface of the cage using a gripping means, allowing precise rotation and insertion of the cassette into the outer joint member, thereby preventing positional deviation and ensuring accurate assembly of balls into the pockets without requiring a reference ball.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If the diameter of the reference ball is smaller than the pocket width, then the reference ball can be easily assembled into the pocket, but the reference ball may fall off from the pocket during movement

Engineering Contradiction:
Improveease of assemblyVSAvoidretention of reference ball
Core Design Contradiction:
Ease of manufactureVSReliability

Solution Approach 1:

The patent applies preliminary action by performing the ball assembly operation before the cassette rotation operation. The reference ball is assembled into the pocket while the cassette is in its initial position, and then the cassette is rotated to the final position. This sequencing ensures the ball is securely in place before any movements that might cause it to fall off.

Inventive Principle:
Principle #10Preliminary action

2Device complexity

If the cassette is assembled to the outer joint member without assembling the reference ball, then the assembly process is simplified, but the cage interferes with the outer joint member causing positional deviation

Engineering Contradiction:
Improveassembly process complexityVSAvoidpositional alignment
Core Design Contradiction:
Device complexityVSManufacturing precision

Solution Approach 1:

The patent uses the reference ball as an intermediary element that facilitates proper positioning. The reference ball, when assembled into the pocket, acts as a mediator that prevents the cage from interfering with the outer joint member during rotation, thereby maintaining positional alignment between the pockets and track grooves.

Inventive Principle:
Principle #24Intermediary (Mediator)

Solution Approach 2:

The reference ball is assembled into the pocket before the cassette rotation operation. This preliminary action ensures that the cage is properly positioned and will not interfere with the outer joint member during the subsequent rotation, maintaining manufacturing precision.

Inventive Principle:
Principle #10Preliminary action

3Manufacturing precision

If the reference ball is used for positioning, then the pockets and track grooves are aligned, but additional assembly steps are required

Engineering Contradiction:
Improvepositional alignmentVSAvoidassembly steps
Core Design Contradiction:
Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent applies self-service by designing the system so that the reference ball performs multiple functions automatically. The reference ball not only positions the pockets relative to the track grooves but also prevents cage interference with the outer joint member. This multi-functionality reduces the need for separate positioning mechanisms or additional alignment steps.

Inventive Principle:
Principle #25Self-service

Data Source

PatentEP3978771A1Automatic assembly apparatus and automatic assembly method for fixed type constant velocity universal joint
Publication Date: 2022.04.06 NTN CORP
  • EP3978771A1 patent drawingFigure 1
  • EP3978771A1 patent drawingFigure 2
  • EP3978771A1 patent drawingFigure 3A~3B

AI summary

A cassette (5) is retained by fitting a shaft part (42), which is provided for a cassette cage part (32) of an automatic assembly apparatus, into a shaft hole (9) of an inner joint member (2) and by gripping an inner peripheral surface of a cage (4) by a gripping means (50) of the cassette cage part (32). The cassette (5) retained by the cassette cage part (32) as mentioned above is inserted into an inner periphery of an outer joint member (7) in a state in which an axis line of the cassette (5) and an axis line of the outer joint member (7) are made to be orthogonal to each other, and thereafter, the cassette (5) is rotated in the inner periphery of the outer joint member (7).