Curved Gear Tooth Flank Geometry to Reduce Stress Concentration
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Solution Overview
Problem
Existing gear designs face stress concentration issues at the tooth flanks due to sharp edges formed when the radius of curvature of adjacent tooth flanks intersect, compromising strength and durability.
Innovation Solution
A gear mechanism with a bottom land and differentiated radii of curvature for the first and second tooth flanks, along with specific shaping to mitigate stress concentration, including curved designs that avoid sharp edges and reduce the distance from the shaft center towards connection points.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the radius of curvature of the tooth flank is made greater to improve strength, then stress concentration at the tooth flank is mitigated, but sharp edges are formed at the boundary region between adjacent teeth
Solution Approach 1:
The patent applies different radius of curvature values to different regions of the tooth flank. Specifically, the first tooth flank has a different radius of curvature than the second tooth flank, allowing each region to be optimized independently. This local differentiation enables the first tooth flank to have sufficient curvature for strength while preventing sharp edge formation at the boundary, thus resolving the contradiction between improving tooth flank strength and avoiding stress concentration at boundaries.
Solution Approach 2:
The patent introduces asymmetry by making the radius of curvature of the first tooth flank different from that of the second tooth flank. This asymmetric design allows the boundary region between adjacent teeth to be optimized specifically, preventing sharp edge formation while maintaining the required strength of individual tooth flanks. The asymmetric curvature distribution resolves the contradiction by treating the two flanks differently to avoid the harmful effect at their interface.
2Strength
If the radius of curvature of the tooth flank is increased to improve strength, then the tooth flank becomes more durable, but the gear size increases
Solution Approach 1:
By applying different radius of curvature values to different tooth flanks locally, the patent achieves the required strength and durability in specific critical regions without uniformly increasing the entire gear size. This localized optimization allows the gear to maintain adequate durability where needed while keeping the overall volume minimized, thus resolving the contradiction between durability improvement and gear downsizing.
Data Source
AI summary
The gear mechanism includes a gear shaped to have a bottom land, a first tooth flank connected to the bottom land, a second tooth flank connected to the bottom land, a first tooth face connected to the first tooth flank, and a second tooth face connected to the second tooth flank. The bottom land is curved, a radius of curvature of the first tooth flank is greater than a radius of curvature of the second tooth flank, and parts of the first tooth flank and the second tooth flank connected to connection points with the bottom land are curved such that a distance of each of the parts from a shaft center of the gear decreases toward the connection points and that a gradient of each of the parts decreases toward the connection points.