Worm Wheel Embedding Structure for Holding Power and Pitch Accuracy
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Solution Overview
Problem
The existing worm wheel structures face challenges in enhancing the holding power of synthetic resin outer wheel elements with respect to metal inner wheel elements, leading to manufacturing errors such as pitch errors due to uneven tooth sizes caused by differential molding shrinkage.
Innovation Solution
The proposed worm wheel design incorporates a metal inner wheel element with a first and second annular concave part, where the synthetic resin outer wheel element is embedded over the entire circumference, including tilted and non-tilted surface parts, and a cylindrical surface part, to improve adhesiveness and uniformity, reducing manufacturing errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If only the radially outer end part of the inner wheel element is embedded in the outer wheel element, then the structure is simple, but the holding power is insufficient
Solution Approach 1:
The inner wheel element is divided into multiple segments along the axial direction, with first and second annular concave parts creating distinct embedding zones. This segmentation allows the outer wheel element to be embedded at multiple locations, significantly improving holding power while maintaining a relatively simple overall structure.
Solution Approach 2:
The embedding structure is extended from a single radial embedding at the outer end to multi-dimensional embedding through annular concave parts at both axial ends. This dimensional extension improves holding power by distributing the embedding force across multiple surfaces and locations.
2Manufacturing precision
If the outer wheel element is embedded only at the radially outer end part, then the manufacturing process is simple, but manufacturing precision deteriorates due to uneven tooth sizes
Solution Approach 1:
The molding process is segmented into multiple stages corresponding to the first and second annular concave parts. This segmentation allows for controlled embedding at different locations, ensuring uniform tooth sizes while maintaining a manageable manufacturing process through systematic multi-stage molding.
Solution Approach 2:
The first annular concave part is formed preliminarily to enable initial embedding and establish a foundation for uniform tooth sizing. This preliminary action ensures that subsequent molding stages can proceed with controlled precision, reducing manufacturing errors.
3Manufacturing precision
If the radial thickness varies in portions with teeth, then the structure adapts to the concave-convex part geometry, but molding shrinkage becomes uneven causing pitch errors
Solution Approach 1:
The annular concave parts are strategically positioned and dimensioned to provide localized embedding zones that ensure uniform radial thickness in the tooth portions. This local quality control through specific geometric design prevents differential shrinkage and pitch errors while adapting to the overall wheel structure.
Solution Approach 2:
The geometric parameters of the annular concave parts (depth, width, positioning) are optimized to control the embedding depth and ensure uniform radial thickness. By changing these parameters, the design achieves both uniform tooth dimensions and accurate pitch while accommodating the necessary structural variations.
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 configuration significantly enhances the holding power of the synthetic resin outer wheel element and minimizes manufacturing errors like pitch errors by ensuring consistent radial thickness and uniform molding shrinkage across the worm wheel tooth parts.
Implementation Method 1
The outer wheel element 16 is made of a synthetic resin, and a radially outer end part of the inner wheel element 15 is embedded therein over the entire circumference through an injection molding (insertion molding).
Data Source
AI summary
An inner wheel element (15a) is embedded in an outer wheel element (16a), such that a continuous range from an inner diameter side circumferential surface configuring an inner surface of a first annular concave part (22), through an outer circumferential surface of the inner wheel element (15a), to an inner diameter side circumferential surface configuring an inner surface of a second annular concave part (38) in a surface of the inner wheel element (15a) is covered over the entire circumference. Accordingly, a structure is achieved which easily secures a holding power of the synthetic resin outer wheel element with respect to the inner wheel element.