Dual-Type Strain Wave Gearing Flexing Control
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Solution Overview
Problem
Dual-type strain wave gearings face challenges in independently flexing first and second external teeth with different numbers, leading to suboptimal meshing states and bearing-ball load distribution, which affects wear resistance, tooth fatigue, and bearing service life.
Innovation Solution
A dual-type strain wave gearing design with a flexible externally toothed gear having first and second external teeth on a shared cylindrical body, where both teeth are flexed by the same amount to maintain suitable meshing states and average bearing-ball load distribution, using a wave generator to cause ellipsoidal flexing and aligning internally toothed gears coaxially, with specific relationships between tooth numbers and flexing amounts to enhance wear resistance and tooth fatigue strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If first and second external teeth with different numbers are formed on a shared cylindrical body, then a strain wave gearing with low speed ratio is realized, but the meshing state and bearing-ball load distribution become suboptimal
Solution Approach 1:
The externally toothed gear is divided into two distinct tooth sets: first external teeth for meshing with the first internally toothed gear, and second external teeth for meshing with the second internally toothed gear. This segmentation allows each tooth set to be optimized independently for its specific meshing requirements, resolving the conflict between achieving low speed ratio and maintaining optimal meshing state.
Solution Approach 2:
Different regions of the externally toothed gear are given different local properties through the formation of first and second external teeth with different tooth numbers. The first external teeth are designed with specific characteristics for meshing with the first internally toothed gear, while the second external teeth have different characteristics for meshing with the second internally toothed gear, allowing each local region to operate in its optimal state.
2Reliability
If first and second external teeth are flexed by different amounts, then optimal meshing state is achieved, but the cylindrical body cannot be flexed uniformly
Solution Approach 1:
The patent changes the geometric parameters of the externally toothed gear by forming two sets of external teeth with different tooth numbers on the same cylindrical body. This parameter differentiation allows the gear to achieve different effective flexing characteristics for each tooth set during operation, enabling optimal meshing state without requiring complex differential flexing control mechanisms.
3Reliability
If the externally toothed gear is pressed radially outward by ball bearings, then the meshing is sustained, but the bearing-ball load distribution becomes uneven
Solution Approach 1:
The bearing support system is segmented into two independent sets: first wave bearings supporting the first external teeth and second wave bearings supporting the second external teeth. This segmentation allows each bearing set to be independently optimized and loaded, ensuring that the bearing-ball load distribution is averaged and balanced, thereby extending bearing service life while sustaining reliable meshing.
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 design allows for a strain wave gearing with a low speed ratio, improved wear resistance, and extended bearing service life by ensuring suitable meshing states and load distribution, providing greater design freedom and reducing the risk of suboptimal flexing.
Implementation Method 1
a cylindrical externally toothed gear capable of flexing in a radial direction
Data Source
AI summary
An externally toothed gear of a dual-type strain wave gearing is provided with first and second external teeth having different tooth numbers, and is flexed into an ellipsoidal shape by a wave generator. When the theoretical values of the radial flexing amounts at major-axis positions of the first and second external teeth flexed into the ellipsoidal shape are expressed by d1=m1n1 and d2=m2n2 (m1 and m2 represent the modules of the first and second external teeth, and n1 and n2 represent positive integers), the radial flexing amount of the first and second external teeth flexed by the wave generator satisfies d=(d1+d2)/ω(1.4≤ω≤2.6). Accordingly, a dual-type strain wave gearing can be achieved with which the first and second external teeth having different numbers can be suitably flexed to form excellent mating states with respective internally toothed gears.