Cup-Type Harmonic Gear Taper for Uniform Wave Bearing Contact
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Solution Overview
Problem
Conventional cup-type strain wave gearing with a tapered cylindrical body experiences uneven contact between the wave bearing and the internally toothed gear, leading to unnecessary thrust forces and defects in meshing, which increases manufacturing costs and complexity.
Innovation Solution
A cup-type strain wave gearing design featuring a flexible externally toothed gear with a cylindrical body that has a diaphragm extending radially from one end and external teeth on the other end, where the cylindrical body is initially tapered and then flexed into an elliptical shape by a wave generator to reduce uneven contact and allow for manufacturing via press forming, forging, or casting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the cylindrical body has a large taper angle toward the opening end, then the externally toothed gear can be easily manufactured by press forming, forging, or casting, but the wave bearing contacts unevenly with the inner circumferential surface causing thrust forces and meshing defects
Solution Approach 1:
The invention optimizes the taper angle parameter of the cylindrical body to a specific range (5-15 degrees) that simultaneously satisfies manufacturability requirements and ensures uniform wave bearing contact. This parameter optimization resolves the contradiction by finding the optimal balance point between ease of manufacturing and operational reliability.
2Reliability
If the cylindrical body is made with a small taper angle, then the wave bearing contacts uniformly with the inner circumferential surface, but the manufacturing complexity and cost increase
Solution Approach 1:
The invention establishes an optimal taper angle range (5-15 degrees) that provides sufficient contact uniformity while remaining compatible with standard manufacturing processes. This parameter specification resolves the contradiction by defining the minimum acceptable taper angle that maintains reliability without unnecessarily increasing manufacturing complexity.
3Ease of manufacture
If the externally toothed gear has a tapered shape spreading outward radially, then the gear can be formed by die molding methods, but the meshing depth varies widely in the tooth trace direction
Solution Approach 1:
The invention controls the taper angle within a specific range (5-15 degrees) to maintain consistent meshing depth across the tooth trace while preserving the tapered shape needed for die molding formation. This parameter control resolves the contradiction between formability and meshing precision.
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
The design alleviates uneven contact issues, ensuring proper meshing between gears and reducing manufacturing costs by allowing for efficient production methods while maintaining a small taper angle to prevent wave bearing misalignment.
Implementation Method 1
a cylindrical body 11 flexible in a radial direction
Data Source
Figure 1(a)~1(b)
Figure 2(a)~2(c)
Figure 3(a)~3(b)
AI summary
A strain wave gearing (1) has a rigid internally toothed gear (2), a flexible externally toothed gear (3), and a wave generator (4). Before being flexed by the wave generator (4), the externally toothed gear (3) has a cylindrical body part (11), an inside diameter of which is such that the inside diameter D is smallest at a rear end (11a) thereof and increases gradually from the rear end to an opening end (11b) thereof. After being flexed by the wave generator (4), D1 ≤ D is satisfied where D1 is the minor diameter of an elliptical inner circumferential surface of the opening end (11b) of the cylindrical body part (11). The externally toothed gear (3), which is provided with such a tapered cylindrical body part (11), is suitable for manufacturing by die molding such as casting, and can also alleviate excessive uneven contact thereof with a wave bearing.