Plunging CV Joint Geometry for Compact Eight-Ball Rear Drive Shafts

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Solution Overview

Problem

Current plunging type constant velocity universal joints, particularly those with eight balls, face challenges in reducing weight and size while maintaining strength and load capacity, especially when used exclusively for rear-wheel drive shafts where the maximum operating angle can be minimized.

Innovation Solution

The design incorporates an outer joint member with cylindrical inner grooves, an inner joint member with spherical outer grooves and a cage with offset curvature centers, optimized ratios of pitch circle diameter to ball diameter and radial thickness, and a reduced maximum operating angle to minimize component thickness and size, allowing for a smaller pitch circle diameter and reduced weight without compromising torque load capacity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If the number of torque transmission balls is increased to eight, then strength and load capacity are improved, but weight and size increase

Engineering Contradiction:

Improvetorque load capacityVSAvoidweight of universal joint

Core Design Contradiction:

StrengthVSWeight of moving object

Solution Approach 1:

The patent applies parameter changes by optimizing the pitch circle diameter to ball diameter ratio (PCDBALL/DBALL) to a specific range of 3.0 to 3.3. This parameter optimization allows the eight-ball design to achieve sufficient strength and load capacity while minimizing the pitch circle diameter and overall joint size, thereby reducing weight compared to conventional designs with larger dimensions

Inventive Principle:

Principle #35Parameter changes

2Volume of moving object

If the pitch circle diameter is reduced to minimize size, then weight and compactness are improved, but strength and load capacity deteriorate

Engineering Contradiction:

Improvesize of universal jointVSAvoidtorque load capacity

Core Design Contradiction:

Volume of moving objectVSStrength

Solution Approach 1:

The patent resolves this contradiction through precise parameter optimization, setting the pitch circle diameter to ball diameter ratio (PCDBALL/DBALL) within the range of 3.0 to 3.3. This optimized parameter range enables the joint to maintain adequate strength and load capacity with a reduced pitch circle diameter, achieving compact size without sacrificing structural integrity

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent employs composite material construction by combining the cage structure with eight torque transmission balls, where the cage provides structural framework and the balls provide torque transmission. This composite approach allows efficient load distribution across multiple contact points, enabling reduced overall dimensions while maintaining strength

Inventive Principle:

Principle #40Composite materials

3Strength

If the radial thickness of the inner joint member is increased to ensure strength, then load capacity is improved, but weight and size increase

Engineering Contradiction:

Improvestrength of inner joint memberVSAvoidweight of universal joint

Core Design Contradiction:

StrengthVSWeight of moving object

Solution Approach 1:

The patent optimizes the radial thickness of the inner joint member by correlating it with the ball diameter through a specific ratio range (TI/DBALL). This parameter optimization ensures the inner joint member has sufficient strength to handle radial loads from the eight balls while minimizing excess material, thereby reducing weight and size

Inventive Principle:

Principle #35Parameter changes

4Weight of moving object

If the maximum operating angle is minimized for rear-wheel drive application, then size and weight are reduced, but adaptability to different mounting conditions deteriorates

Engineering Contradiction:

Improveweight of universal jointVSAvoidadaptability to mounting conditions

Core Design Contradiction:

Weight of moving objectVSAdaptability or versatility

Solution Approach 1:

The patent applies local quality by designing the universal joint with specific structural features optimized for rear-wheel drive applications, where the inner joint member can slide axially within the outer joint member. This localized optimization for rear-wheel drive mounting conditions allows reduced operating angle and compact size while maintaining sufficient adaptability for the specific application context

Inventive Principle:

Principle #3Local quality

Data Source

PatentUS11359677B2Plunging type constant velocity universal joint for rear-wheel drive shaft

Publication Date: 2022.06.14 NTN CORP

AI summary

A plunging type constant velocity universal joint includes an outer joint member, an inner joint member, eight balls, and a cage. A curvature center of a spherical portion of an outer peripheral surface of the cage and a curvature center of a spherical portion of an inner peripheral surface of the cage are offset to opposite sides in the axial direction with respect to a joint center by an equal distance. A ratio PCDBALL/DBALL of a pitch circle diameter PCDBALL of the balls to a diameter DBALL of each of the balls is set from 3.3 to 3.6. A ratio TI/DBALL of a radial thickness TI of the inner joint member to the diameter DBALL of each of the balls is set from 0.30 to 0.45.