Worm Wheel Boss Coupling Strength via Curved Wave Pattern
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Solution Overview
Problem
Conventional worm wheels for electric power steering systems face issues with coupling strength due to potential gaps formed between the boss and tooth-shaped parts during injection molding, which can compromise the reliability of the coupling portion.
Innovation Solution
The coupling surfaces of the boss and tooth-shaped parts are designed with a curved wave pattern, increasing the contact area and forming a curve along the rotational direction, thereby enhancing coupling strength and reducing shrinkage after injection molding to prevent gaps between the teeth and the boss part.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the boss part and tooth-shaped part are coupling-molded with a conventional flat surface design, then the manufacturing process is simple, but gaps are formed between the coupling surfaces due to shrinkage, reducing coupling strength
Solution Approach 1:
The coupling surfaces of the boss part and tooth-shaped part are designed with curved wave patterns instead of flat surfaces. The first coupling surfaces include first convex and first concave surfaces, while the second coupling surfaces include second convex and second concave surfaces that continuously repeat along the peripheral surfaces. This curved design increases the contact area between coupling surfaces and prevents gap formation due to shrinkage, thereby enhancing coupling strength between the boss part and tooth-shaped part
2Reliability
If the coupling surfaces are designed with a curved wave pattern to increase contact area, then coupling strength is enhanced, but the manufacturing complexity increases
Solution Approach 1:
The coupling surfaces are designed with curved wave patterns including continuously repeating convex and concave surfaces. This design increases the contact area between the boss part and tooth-shaped part, improving coupling reliability. The curved structure distributes shrinkage forces more evenly across the coupling interface, preventing gap formation and ensuring reliable coupling despite the increased molding process complexity
3Manufacturing precision
If the coupling surfaces are designed to reduce shrinkage, then gaps are prevented at the coupling portion, but the structural integrity may be compromised
Solution Approach 1:
The curved wave pattern design of the coupling surfaces distributes the shrinkage forces evenly across the entire coupling interface rather than concentrating them at specific points. The continuously repeating convex and concave surfaces ensure uniform contact and stress distribution, preventing gap formation while maintaining the overall structural integrity of both the boss part and tooth-shaped part
Data Source
AI summary
A worm wheel of a reduction gear for an electric power steering includes: a boss part including a hollow portion formed along an axial-direction center for coupling of a shaft and having first coupling surfaces, each of which is formed by a first convex surface and a first concave surface continuously repeated along an outer peripheral surface; and a tooth-shaped part having second coupling surfaces, each of which is formed by a second convex surface and a second concave surface continuously repeated along an inner peripheral surface, such that the second coupling surfaces are coupled corresponding to the first coupling surfaces, wherein a plurality of teeth are continuously formed along a periphery thereof with spacing portions interposed therebetween.