Lightweight Gear Structure With Rounded Resin Coupling Irregularities
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Solution Overview
Problem
Existing lightweight gears face challenges in reducing weight while maintaining structural integrity, particularly due to stress concentration at corners of irregularities, which can lead to fatigue fracture during long-term operation.
Innovation Solution
A lightweight gear design featuring an annular metal tooth portion, a metal shaft, and a resin coupling element with irregularities that are rounded to reduce stress concentration, allowing for effective torque and force transmission while minimizing weight through the use of sintered metal components and a thermoplastic resin coupling element with optimized thickness and through-holes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If a resin coupling element is used to reduce weight, then weight is reduced, but stress concentration occurs at corners of irregularities leading to fatigue fracture
Solution Approach 1:
The patent applies curvature by rounding the corners of irregularities in the coupling element. Specifically, the inner peripheral surface and outer peripheral surface of the coupling element have rounded corners at the irregularities, which eliminates stress concentration points and prevents fatigue fracture while maintaining the weight reduction benefits of using a resin coupling element.
2Volume of moving object
If a thin coupling element is used to reduce weight, then weight and volume are reduced, but structural integrity and stress resistance deteriorate
Solution Approach 1:
The patent applies local quality by providing different properties at different locations of the coupling element. The corners of irregularities are rounded to have higher stress resistance, while other portions of the coupling element can maintain thinner dimensions for weight reduction. This localized modification of geometry optimizes both weight and strength.
Solution Approach 2:
The rounded corners at the irregularities of the coupling element eliminate stress concentration points, allowing the coupling element to be made thinner while maintaining sufficient stress resistance. The curvature at critical locations compensates for the reduced overall thickness.
3Strength
If metal components are used for tooth portion and shaft, then strength is maintained, but weight increases
Solution Approach 1:
The patent applies composite materials by combining metal components (tooth portion and shaft) with a resin coupling element. The metal parts provide necessary strength for load-bearing functions, while the resin coupling element reduces overall weight. The irregularities with rounded corners ensure reliable stress transmission between the metal and resin components.
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
The design effectively reduces weight and prevents excessive stress concentration, enabling a thin coupling element with improved surface hardness and durability, while maintaining the strength of metal components and facilitating heat dissipation and resistance to lubricants.
Implementation Method 1
The tooth portion and the shaft are made of sintered metal
Data Source
AI summary
A light-weight gear including: an annular tooth portion made of metal; a shaft extending along a central axis of the tooth portion and made of metal; and a coupling element configured to couple the shaft to the tooth portion and made of a resin, in which a joining part between the shaft and the coupling element and a joining part between the tooth portion and the coupling element are provided with irregularities configured to be engaged with one another in a circumferential direction, and corners of the irregularities are rounded to release a stress. Also, provided is a manufacturing method of a light-weight gear including: disposing the tooth portion and the shaft in a mold and injecting a molten resin into a cavity of the mold, thereby simultaneously performing injection molding of the coupling element and joining the coupling element to the tooth portion and the shaft.