Tripod Constant Velocity Universal Joint Dimensional Optimization

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Solution Overview

Problem

Existing tripod type constant velocity universal joints face challenges in achieving lightweight, compact, and low-cost designs while maintaining strength, particularly due to insufficient optimization of component dimensions and shapes.

Innovation Solution

The design includes specific dimensional ratios for the outer and inner rollers and the trunnion journal, along with a noncircular cross-section for the journal root portion, to balance strength, rigidity, and compactness, and incorporates undercuts for smooth assembly and constant radius of curvature for enhanced strength and compactness.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Weight of moving object

If the cross section of the journal root portion is made noncircular to reduce weight and size, then weight reduction and compactness are achieved, but strength at the root portion becomes insufficient

Engineering Contradiction:

Improveweight of universal jointVSAvoidstrength at root portion of trunnion journal

Core Design Contradiction:

Weight of moving objectVSStrength

Solution Approach 1:

The journal root portion employs a noncircular cross-section with different diameters in different directions (larger diameter in the joint circumferential direction, smaller diameter in the joint axial direction). This local variation in geometry optimizes strength distribution where needed while reducing material in less critical areas, achieving both weight reduction and maintained strength.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The invention specifies precise dimensional ratios for the journal root portion parameters (Dj1r = 0.42-0.50, Dj2r = 0.30-0.38) to optimize the balance between strength and weight. By carefully controlling these geometric parameters, the noncircular section achieves sufficient strength while minimizing material usage.

Inventive Principle:

Principle #35Parameter changes

2Volume of moving object

If dimensions of components are reduced to achieve lightweight and compact design, then weight and size are reduced, but overall strength of the universal joint becomes insufficient

Engineering Contradiction:

Improvesize of universal jointVSAvoidoverall strength of universal joint

Core Design Contradiction:

Volume of moving objectVSStrength

Solution Approach 1:

The invention establishes specific ratio ranges for multiple critical dimensions including outer roller (Dor = 0.80-0.88, Tor = 0.18-0.22), inner roller (Dir = 0.65-0.75, Tir = 0.10-0.15), and journal root portion (Dj1r = 0.42-0.50, Dj2r = 0.30-0.38). These coordinated parameter optimizations ensure that all components are scaled appropriately to maintain overall joint strength while achieving compact dimensions.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The journal root portion uses an asymmetric noncircular cross-section with different diameters in different directions. This asymmetric geometry allows optimization of material distribution - larger diameter where strength is needed (circumferential direction) and smaller diameter where weight reduction is prioritized (axial direction), achieving both compactness and strength.

Inventive Principle:

Principle #4Asymmetry

3Volume of moving object

If the journal root portion is made compact to reduce size, then compactness is improved, but assembly difficulty increases

Engineering Contradiction:

Improvesize of journal root portionVSAvoidease of assembly

Core Design Contradiction:

Volume of moving objectVSEase of operation

Solution Approach 1:

The roller cassette is pre-assembled as a complete unit before installation into the universal joint. This preliminary assembly ensures proper positioning and fit of all roller components, facilitating smoother installation into the compact journal root portion and reducing assembly complexity despite the compact dimensions.

Inventive Principle:

Principle #10Preliminary 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

This approach results in a tripod type constant velocity universal joint that achieves a balance of lightweight, compactness, and low cost while maintaining the required strength and operating angle, with improved assembly and reduced stress concentration.

Implementation Method 1

an outer roller that can roll along the track grooves of the outer joint member

Methodology Applied

Scientific EffectRolling: Roller

Implementation Method 2

a plurality of rolling elements disposed between the outer roller and the inner roller

Methodology Applied

Scientific EffectRolling contact: Ball Bearing

Data Source

PatentUS7473181B2Tripod type constant velocity universal joint

Publication Date: 2009.01.06 NTN CORP

AI summary

The present invention provides a lightweight, compact, and low-cost tripod type constant velocity universal joint while maintaining strength of overall tripod type constant velocity universal joint. The dimensional ratio of each component of the tripod type constant velocity universal joint is set as follows: 0.80<Dor<0.90, 0.105<Tor<0.115, 0.025<fir<0.045, 0.025<t2r<0.075, 0.53<Dir<0.63, 0.065<Tir<0.085, 0.32<Dj1r<0.42, and 0.32<Dj2r<0.35. In this event, the subscript "r" means that each dimension is divided by the trunnion journal pitch circle diameter D (=PCD) of the joint.