Plastic Gear With Composite Core And Surface Layer
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Solution Overview
Problem
Plastic gears face challenges in high load, high revolution, and high temperature applications due to limitations in fatigue strength, abrasion resistance, impact resistance, and compatibility with engine oils, while existing methods increase manufacturing costs and require gear-cutting work.
Innovation Solution
A plastic gear design featuring a high elastic modulus inner core and a relatively low elastic modulus surface layer, where the inner core is revolvably fitted around a metal or ceramic gear inner circumferential member, allowing relative displacement and dispersing load across the gear tooth portions, without the need for reinforced materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If plastic gear is used for low cost and low noise, then manufacturing cost decreases and vibrations are reduced, but fatigue strength and impact resistance become insufficient for high load applications
Solution Approach 1:
The gear combines a thermoplastic resin matrix with dispersed elastomer particles to create a composite material that exhibits both thermoplastic processability and elastomeric impact resistance. The elastomer particles (5-50 μm diameter) dispersed in the thermoplastic resin create a composite structure that absorbs impact energy while maintaining the overall gear integrity and fatigue strength.
2Object-generated harmful factors
If plastic gear is used for low noise, then vibrations are attenuated, but impact resistance becomes insufficient under high load conditions
Solution Approach 1:
The invention changes the material parameters by controlling the elastomer particle size (5-50 μm) and concentration (1-50 parts by weight per 100 parts of thermoplastic resin) to optimize both vibration attenuation and impact resistance. The specific particle size range allows the elastomer to effectively absorb impact energy while the thermoplastic resin maintains structural integrity.
3Strength
If thermosetting resin is used to improve strength, then fatigue strength increases, but manufacturing complexity increases due to gear-cutting work and heat treatment
Solution Approach 1:
The invention replaces the traditional thermosetting resin system with a thermoplastic resin-based composite that achieves comparable strength through a different mechanism. The thermoplastic resin with dispersed elastomer particles provides fatigue strength through the composite structure, eliminating the need for complex gear-cutting operations and heat treatment processes required by thermosetting resins.
4Force
If conventional plastic gear is used for high load applications, then load capacity increases, but aggression to opposing steel gear increases
Solution Approach 1:
The invention applies local quality by incorporating elastomer particles specifically in the gear tooth contact regions where stress concentration occurs. The elastomer particles (5-50 μm) are dispersed throughout the thermoplastic resin, providing localized compliance and shock absorption at the tooth surfaces, which reduces aggression to the opposing steel gear while maintaining overall load capacity.
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 achieves low vibrations, high fatigue strength, high impact resistance, and abrasion resistance, maintaining low aggression to opposing gears while eliminating the need for gear-cutting work and reducing manufacturing costs.
Implementation Method 1
the plastic gear is obtained at low cost since gear-cutting work is not necessary because the tooth portion can be formed just by injection molding; and thus replacement from the steel gear advances, so that the plastic gears are broadly used in OA equipment, or audio products. However, the above physical properties providing low vibrations and low noise become constraint
Implementation Method 2
JP55-41273A has disclosed the plastic gear using the thermoplastic resin material, and further, JP2-8542A and JP2005-214338A have disclosed the plastic gear in which the plastic portion is made two-layer structure of the obverse layer tooth and the internal layer tooth
Data Source
AI summary
A plastic gear having a gear peripheral portion including a tooth portion is constituted by a plastic material, and a gear inner circumferential member with an annular shape or a disk shape is provided at the inner circumferential side of the gear peripheral portion. The gear peripheral portion includes an inner core and a surface layer member, the inner core being covered with the surface layer member and made of plastic with high elastic modulus and high strength, and the surface layer member being made of plastic with relatively low elastic modulus. The inner core is revolvably fitted around the gear inner circumferential member so as to revolve around the gear revolving axis, and an engaging portion is provided at an interface of the surface layer member and the gear inner circumferential member for preventing relative revolution around the gear revolving axis.