Machining Tool Rounded Root for Spline Stress Reduction

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Solution Overview

Problem

Conventional machining tools for forming spline teeth on vehicle hub units experience high stress concentration, leading to potential breakage and increased manufacturing costs due to fatigue, which affects both the durability of the punch and the spline teeth.

Innovation Solution

The machining tool features tooth forming portions with a rounded-portion forming portion at the root, where the radius gradually changes in the radial direction, reducing stress concentration and enhancing durability, while maintaining sufficient strength and durability of the spline teeth.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If the tooth forming portions are pressed against the axial end face of the hub wheel to plastically form the spline teeth, then the spline teeth are formed successfully, but large stress is produced in the tooth forming portions leading to potential breakage due to fatigue

Engineering Contradiction:

Improvespline teeth formationVSAvoidtooth forming portions durability

Core Design Contradiction:

Manufacturing precisionVSReliability

Solution Approach 1:

A rounded portion is formed at the root of each tooth forming portion, where the radius of curvature gradually changes in the radial direction. This curved geometry eliminates stress concentration at sharp corners, reducing the risk of fatigue breakage while maintaining the ability to form precise spline teeth through plastic deformation

Inventive Principle:

Principle #14Spheroidality (Curvature)

2Reliability

If the shape of each tooth forming portion is changed to reduce stress concentration, then the durability of the tooth forming portions is increased, but the shape of the spline teeth may be affected

Engineering Contradiction:

Improvetooth forming portions durabilityVSAvoidspline teeth shape

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The rounded portion is specifically located only at the root of the tooth forming portion, while the rest of the tooth forming geometry remains unchanged. This localized modification reduces stress concentration at the critical root area without affecting the tooth profile geometry that determines spline teeth shape, thus resolving the contradiction between durability and manufacturing precision

Inventive Principle:

Principle #3Local quality

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 design balances the durability of the punch and spline teeth, reducing manufacturing costs by minimizing stress concentration and improving the longevity of both components.

Implementation Method 1

multiple tooth forming portions for plastically forming spline teeth on an axial end face of a vehicle hub unit

Methodology Applied

Scientific EffectPlastic deformation: Plasticity

Data Source

PatentUS9180734B2Machining tool for vehicle hub unit and vehicle hub unit

Publication Date: 2015.11.10 JTEKT CORP

AI summary

In a machining tool, multiple tooth forming portions for plastically forming spline teeth on an axial end face of a vehicle hub unit, the axial end face facing inward in the vehicle lateral direction, are formed in a circular pattern about the central axis of the machining tool. In the machining tool, a rounded-portion forming portion is formed to form a rounded portion between a tooth flank and a top land of each spline tooth, and the radius of the rounded-portion forming portion gradually changes in the radial direction about the central axis.