Strain Wave Gear Bolt Hole Layout for Meshing Accuracy
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Solution Overview
Problem
In strain wave gearing with an inner-race integrated-type internally toothed gear, deformation occurs at the internal-tooth forming portion during bolt fastening, leading to reduced accuracy of engagement and assembly with the externally toothed gear.
Innovation Solution
The internally toothed gear is designed with bolt holes that have a screw hole part offset from the internal teeth along the axial direction, allowing the bolt-fastening force to be applied away from the internal teeth, thereby minimizing deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the internally toothed gear is fastened by bolts to another member, then the gear is securely attached, but the internal-tooth forming portion undergoes deformation which deteriorates engagement accuracy with the externally toothed gear
Solution Approach 1:
The bolt holes are designed to extend in the axial direction rather than radially through the gear body. This dimensional change allows the fastening force to be applied away from the internal teeth in the radial plane, preventing deformation of the tooth-forming portion while maintaining secure attachment through the axial direction.
Solution Approach 2:
The bolt holes are positioned and oriented specifically so that the fastening force is applied at locations and directions that do not interfere with the internal teeth. The local structural arrangement ensures that the critical tooth-forming areas remain free from deformation-causing stresses while still achieving overall gear fixation.
2Device complexity
If the screw hole is located near the internal teeth, then the structure is simplified, but deformation occurs during fastening which reduces assembling accuracy
Solution Approach 1:
The screw holes extend in the axial direction perpendicular to the plane containing the internal teeth. This spatial reorientation allows the fastening function to be separated from the tooth-forming region, achieving both structural simplicity and high assembling accuracy by eliminating the conflict between fastening and tooth integrity.
3Volume of moving object
If the internally toothed gear is miniaturized and flattened, then the overall size is reduced, but the placement of bolt holes becomes more constrained which may cause deformation
Solution Approach 1:
By extending bolt holes in the axial direction, the design utilizes the third dimension to resolve the spatial conflict between miniaturization and fastening requirements. This allows compact radial dimensions while maintaining adequate bolt hole positioning that avoids deforming the internal teeth, thus achieving both small size and high precision.
Data Source
AI summary
A strain wave gearing includes an internally toothed gear integrated with an inner ring. A bolt hole is formed in the internally toothed gear. The bolt hole includes a bolt passage hole part, and a screw hole part extending in the direction of an axial line, continuously from the bolt passage hole part. The screw hole part, to which a bolt-fastening force is applied, is formed at a location away in the direction of the axial line from a location adjacent to a radially outer side of an internally toothed gear. Deformation, occurring during fastening of a bolt, at a portion in which the internally toothed gear is formed can be reduced, and adverse effects caused by the deformation such as a decrease in the accuracy of engagement or meshing of the internally toothed gear and an externally toothed gear can be inhibited.