Dual-Type Strain Wave Gearing Gap Structure for Tooth Fatigue
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Dual-type strain wave gearing faces challenges in achieving uniform tooth-flank load distribution and suitable tooth contact along the tooth trace direction, leading to high stress concentration, torsion, and reduced fatigue strength and load transfer torque due to differences in tooth numbers and profiles, as well as uneven bearing-ball load distributions.
Innovation Solution
Incorporating a rigid first and second internally toothed gear with a flexible externally toothed gear and a wave generator that forms a gap between the external teeth, with specific dimensions and depth relationships to create a cutter clearance area, and positioning wave bearings to enhance rigidity and support, ensuring uniform load distribution and suitable contact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If first and second external teeth are formed in the outer peripheral surface of a shared flexible cylindrical body with different tooth numbers and profiles, then a dual-type strain wave gearing can easily realize a low speed ratio, but high stress concentration and large torsion occur in portions between the external teeth, causing non-uniform tooth-flank load distribution and reduced tooth bottom fatigue strength
Solution Approach 1:
The patent applies local quality by providing different tooth profiles (first and second external teeth) at different locations on the flexible externally toothed gear. Each tooth profile is optimized for its specific meshing requirements with corresponding internal teeth, enabling different speed ratios while maintaining adequate stress distribution through localized design optimization.
Solution Approach 2:
The patent changes geometric parameters by carefully designing the tooth profiles, tooth depths, and spacing of the first and second external teeth. By adjusting these parameters, the patent achieves uniform tooth-flank load distribution and reduces stress concentration, thereby improving tooth bottom fatigue strength while maintaining the ability to realize low speed ratios.
2Strength
If the tooth-flank load distribution is made uniform to increase tooth bottom fatigue strength, then the maximum tooth-flank load is reduced, but the meshing states along the tooth trace direction are affected by wave generator support rigidity
Solution Approach 1:
The patent applies preliminary action by pre-designing the tooth profiles and spacing of the first and second external teeth to anticipate and compensate for loading conditions. The tooth geometries are optimized in advance to ensure uniform load distribution and stable meshing states, preventing stress concentration and torsion before they occur during operation.
Solution Approach 2:
The patent adjusts geometric parameters including tooth depth, tooth thickness, and spacing between first and second external teeth to optimize both uniform load distribution and meshing stability. These parameter changes ensure that the gear system maintains reliable meshing states while achieving uniform tooth-flank load distribution.
3Reliability
If the support rigidity of the wave generator is increased to maintain appropriate meshing states, then tooth contact along the tooth trace direction is improved, but the device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent applies local quality by providing different tooth profiles at different locations, which allows the flexible externally toothed gear to maintain appropriate meshing states with corresponding internal teeth without requiring excessive wave generator rigidity. The localized optimization of tooth geometries compensates for potential support rigidity limitations.
4Reliability
If the externally toothed gear is not appropriately supported by the wave generator, then the bearing-ball load distributions become uneven, but increasing support rigidity increases manufacturing precision requirements
Solution Approach 1:
The patent applies local quality by optimizing the tooth profiles and spacing of first and second external teeth to distribute loads more evenly across the bearing-ball contact points. This localized geometric optimization helps achieve more uniform bearing-ball load distributions, improving bearing durability while reducing the need for extremely high support rigidity and manufacturing 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
This configuration enhances the wear resistance and fatigue strength of the externally toothed gear, reduces torsion, and improves the load transfer torque and bearing-ball load distribution, leading to increased durability and longer service life.
Implementation Method 1
a flexible externally toothed gear in which first external teeth capable of meshing with the first internal teeth and second external teeth capable of meshing with the second internal teeth are formed in an outer peripheral surface of a radially flexible cylindrical body
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 teeth numbers, and a gap formed between these teeth as a cutter clearance area for tooth cutters. Where L1 is the maximum width of the gap, t1 is a depth from the tooth top land of the first external teeth to the deepest part of the gap, h1 is the tooth depth of the first external teeth, t2 is a depth from the tooth top land of the second external teeth to the deepest part, and h2 is the tooth depth of the second external teeth, any one of the following conditions 1 to 3 is satisfied:L1=0.1L−0.35L, t1=0.9h1−1.3h1, and t2=0.3h2−0.9h2 Condition 1:L1=0.1L−0.35L, t1=0.3h1−0.9h1, and t2=0.9h2−1.3h2 Condition 2:L1=0.1L−0.35L, t1=0.3h1−0.9h1, and t2=0.3h2−0.9h2 Condition 3:It is possible to obtain a dual-type strain wave gearing in which wear resistance and tooth bottom fatigue strength are increased.