Composite Worm Wheel Structure for Tooth Pitch Accuracy
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Solution Overview
Problem
The existing worm wheel structures suffer from manufacturing errors in the tooth parts due to differences in radial thickness and molding shrinkage, leading to pitch errors and reduced accuracy in the worm wheel tooth parts.
Innovation Solution
A worm wheel design featuring an inner metal wheel element with an annular concave part and a synthetic resin outer wheel element, where the outer resin enters into the concave part, providing a cylindrical surface for uniform thickness and improved holding power, and incorporating a concave-convex structure to enhance adhesiveness and reduce manufacturing errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a concave-convex part is provided in the outer circumferential surface of the inner wheel element to improve holding power, then the holding power of the outer wheel element is improved, but the radial thickness becomes non-uniform causing manufacturing errors in the worm wheel tooth part
Solution Approach 1:
The inner wheel element is divided into two distinct functional zones: an annular concave part for mechanical interlocking and holding power, and a cylindrical surface part with uniform radial thickness for precise tooth formation. This segmentation allows each zone to optimize its specific function without compromising the other.
Solution Approach 2:
Different regions of the inner wheel element are given different geometric properties: the annular concave part has a non-uniform profile optimized for holding power, while the cylindrical surface part has a uniform profile optimized for manufacturing precision. This local differentiation resolves the contradiction between the two competing requirements.
2Strength
If the radial thickness of the outer wheel element is increased to improve holding power, then the holding power is improved, but the molding shrinkage increases causing pitch errors in the tooth part
Solution Approach 1:
The inner wheel element is segmented into an annular concave part that accommodates resin infiltration for holding power, and a cylindrical surface part that maintains uniform radial thickness for consistent molding shrinkage and pitch accuracy.
Solution Approach 2:
The annular concave part acts as an intermediary zone where the synthetic resin can infiltrate and bond with the inner wheel element, providing enhanced holding power without requiring increased radial thickness of the outer wheel element itself.
3Ease of manufacture
If the outer wheel element is made entirely of synthetic resin to reduce manufacturing cost and noise, then ease of manufacture and noise reduction are improved, but manufacturing errors occur in the tooth part due to non-uniform thickness
Solution Approach 1:
The worm wheel combines a metal inner wheel element with a synthetic resin outer wheel element. The metal core provides structural stability and uniform thickness reference, while the resin layer provides noise reduction and cost benefits. This composite structure enables both ease of manufacture and manufacturing precision.
Solution Approach 2:
The inner wheel element provides a localized cylindrical surface with uniform radial thickness where the teeth are formed, ensuring manufacturing precision in the critical tooth area while allowing the rest of the outer wheel element to be made of cost-effective synthetic resin.
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 effectively suppresses manufacturing errors in the worm wheel tooth parts, ensuring consistent radial thickness and improved holding power, thereby enhancing the accuracy and reliability of the worm wheel.
Implementation Method 1
The radially outer end part of the inner wheel element is embedded over an entire circumference through an injection molding
Data Source
AI summary
An outer wheel element (16a) formed in an annular shape with a synthetic resin and having a worm wheel tooth part (19a) on an outer circumferential surface thereof embeds a radially outer end part of an inner wheel element (15a) formed in an annular shape with a metal. An outer circumferential surface of the inner wheel element (15a), which is radially superimposed with an engaging part between the worm tooth part (19a) and a the worm wheel tooth part serves as a cylindrical surface part (24). This realizes a structure capable of suppressing manufacturing error of the worm wheel tooth part engaging with the worm tooth part.