Worm Wheel Tooth Flank Segmentation for Void Control
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Solution Overview
Problem
Conventional worm wheel manufacturing methods result in voids forming during injection molding, which can expand towards the tooth crest, compromising the strength and performance of the worm wheel.
Innovation Solution
A worm wheel design featuring non-cutting regions on the tooth flanks and ends, offset from the mid-position of the teeth, combined with a cutting region formed by a hob after injection molding, to suppress void expansion and enhance tooth strength and grease lubrication properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the entire tooth flank is formed by cutting with a hob after injection molding, then the meshing engagement with the worm shaft is improved, but voids expand toward the tooth crest reducing strength
Solution Approach 1:
The tooth flank is divided into two distinct regions: a cutting region that engages with the worm shaft and a non-cutting region that prevents void expansion. This segmentation allows each region to serve its specific function - the cutting region ensures proper meshing engagement while the non-cutting region maintains structural integrity by blocking void propagation toward the tooth crest.
Solution Approach 2:
Different portions of the tooth flank are given different qualities - the cutting region is machined to achieve precise engagement surfaces, while the non-cutting region retains the injection-molded structure that prevents void expansion. This local differentiation optimizes both meshing performance and structural strength without compromising either aspect.
2Strength
If non-cutting regions are provided on tooth flanks offset from mid-position, then void expansion is suppressed and tooth strength is improved, but manufacturing complexity increases
Solution Approach 1:
The mold is designed in advance to form teeth with predetermined non-cutting regions during the injection molding process itself. This preliminary action eliminates the need for subsequent machining operations in those regions, reducing manufacturing complexity while maintaining the strength benefits of the non-cutting structure. The offset positioning from mid-position is built into the mold cavity design.
3Reliability
If non-cutting regions are provided at end portions of tooth flanks, then grease lubrication properties are improved, but the tooth geometry becomes more complex
Solution Approach 1:
Non-cutting regions are strategically placed at the end portions of tooth flanks where grease retention is most beneficial. These localized non-cutting regions create natural grease pockets that improve lubrication properties without requiring complex overall tooth geometry. The end-positioning allows simple geometric modifications that provide functional benefits for grease retention and distribution.
Data Source
AI summary
A worm wheel including an annular worm wheel main body formed from a resin material; teeth on an outer periphery of the worm wheel main body in a circumferential direction of the worm wheel main body a; a first region on respective tooth flanks of the teeth and offset from a mid-position of a whole depth of the respective teeth in a radially outward direction of the worm wheel main body; a first region; and a second region.