Composite Gear Structure for Shrinkage-Induced Crack Prevention
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Solution Overview
Problem
Conventional composite gears formed from different materials face challenges in maintaining coupling strength and preventing cracks due to shrinkage differences between materials, especially under high-temperature conditions, where distortion and breakage can occur within a relatively short timeframe.
Innovation Solution
A composite gear design featuring a first member with a rotation shaft and disk-shaped web, and a second member with engaging teeth, where spaces are created between the members to allow for relative positional changes due to shrinkage, ensuring firm coupling and preventing distortion by absorbing dimensional changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If composite gear is formed from different materials (first member with high rigidity and second member with high slidability), then mechanical strength and rotation lubricity are improved, but shrinkage differences between materials cause distortion and cracks
Solution Approach 1:
The gear is divided into two separate members (first member and second member) that are coupled together. The first member provides structural support while the second member provides gear functionality. This segmentation allows each material to be optimized for its specific function while managing the shrinkage differences through controlled coupling structures.
Solution Approach 2:
Different regions of the gear have different material properties - the first member uses material with high rigidity for structural integrity, while the second member uses material with high slidability for gear operation. The coupling structure between members is designed with specific local features (protrusions and recesses) to manage the interface between different materials.
2Stability of the object's composition
If high rigidity material is used for rotation supporting portion, then deformation under torque is suppressed, but coupling with gear portion becomes difficult due to material incompatibility
Solution Approach 1:
The first member is inserted into the second member, creating a nested structure where the rotation supporting portion is housed within the gear portion. This nesting arrangement facilitates coupling while maintaining the rigidity of the first member and the slidability of the second member.
Solution Approach 2:
The coupling structure acts as an intermediary between the two incompatible materials. Protrusions from the first member fit into recesses of the second member, creating a mechanical interface that accommodates both materials' properties while ensuring firm coupling.
3Manufacturing precision
If precision standards are set narrowly for high-quality products, then quality is improved, but dynamic precision under rotation cannot be ensured due to deformation
Solution Approach 1:
The gear uses a composite structure combining two different materials - a rigid material for the rotation supporting portion and a slidable material for the gear portion. This composite approach allows the rigid portion to maintain precision under load while the slidable portion ensures smooth operation, together achieving both high quality and dynamic precision.
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 suppresses breakage and distortion caused by shrinkage differences, maintaining strong coupling between the members and extending the endurance time of the composite gear, even under high-temperature conditions.
Implementation Method 1
deterioration of shape caused by shrinkage of resin at the time of molding
Data Source
AI summary
A composite gear includes: a first member comprising a rotation shaft portion and a disk-shaped web extending in radial directions from the rotation shaft portion; and a second member comprising at least one engaging tooth on an outer periphery thereof and provided being supported by the web so as to surround an outer periphery of the first member. A space is provided between the second member and an outermost peripheral surface of the first member in a radial direction, a space is provided between the first member and an innermost peripheral surface of the second member in a radial direction, and at least one of the first member and the second member is formed to nip another of the first member and the second member from both sides thereof in an axial direction of the rotation shaft portion.