Strain Wave Gearing Segmented Coupling for Torque Rigidity
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Solution Overview
Problem
Conventional flat strain wave gearing has inferior holding rigidity due to the need for an externally toothed gear to elastically deform, limiting its ability to transmit large torque effectively.
Innovation Solution
The strain wave gearing incorporates a tube body that can flex radially, with first and second externally toothed gear portions forming non-circular cross-sections, a coupling externally toothed gear portion maintaining a circular shape, and wave generators causing these gear portions to flex into ellipsoidal shapes, increasing meshing rigidity and torque transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the externally toothed gear is made to elastically deform to enable strain wave gearing operation, then the gearing can achieve backlash-free transmission and large reduction ratio, but the holding rigidity deteriorates and large transmission torque cannot be ensured
Solution Approach 1:
The externally toothed gear is divided into three distinct portions along the axial direction: a first externally toothed gear portion, a coupling externally toothed gear portion, and a second externally toothed gear portion. This segmentation allows different regions to perform different functions - the first and second portions can elastically deform for strain wave operation, while the coupling portion maintains rigidity for stable torque transmission.
Solution Approach 2:
Different portions of the externally toothed gear are given different structural properties. The coupling externally toothed gear portion is designed with higher rigidity to maintain a circular cross-sectional shape, while the first and second externally toothed gear portions are designed to elastically deform. This local differentiation of mechanical properties resolves the contradiction between needing elasticity for operation and rigidity for torque transmission.
2Ease of operation
If the externally toothed gear flexes into an ellipsoidal shape, then the wave generator can cause meshing with internally toothed gears, but the meshing rigidity decreases and torque transmission capability is limited
Solution Approach 1:
The gear is segmented axially into deformation zones (first and second externally toothed gear portions) and a non-deformation zone (coupling externally toothed gear portion). This allows the gear to achieve the necessary ellipsoidal flexing for meshing operation while maintaining a rigid coupling portion that does not deform, thereby preserving meshing rigidity during torque transmission.
Solution Approach 2:
The coupling externally toothed gear portion is specifically designed to maintain a circular cross-sectional shape and not flex into an ellipsoidal shape, while the first and second portions are designed to flex. This local differentiation ensures that the coupling portion provides stable, rigid meshing for torque transmission while the other portions enable the necessary wave generation motion.
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 meshing rigidity and allows for greater torque transmission by maintaining a circular cross-sectional shape for the coupling externally toothed gear portion, ensuring stable linking with the coupling internally toothed gear throughout the periphery.
Implementation Method 1
a tube body capable of flexing in a radial direction; a wave generator causing the tube body to flex in the radial direction so that the coupling externally toothed gear portion has a circular cross-sectional shape and the first and second externally toothed gear portions have a non-circular cross-sectional shape
Data Source
AI summary
First and second external tooth gear parts of a strain wave gearing are bent in an elliptic shape by a wave generator to engage with first and second internal tooth gears, respectively. The first and second external tooth gear parts are bent so as to have elliptic shapes the phases of which are rotated 90 degrees from each other about a rotational center line. A coupling external tooth gear part that maintains a circular cross-sectional shape which does not deform is formed in between the first and second external tooth gear parts. The coupling external tooth gear part is maintained so as to be coupled with a coupling internal tooth gear in an engaged manner. The strain wave gearing has high engagement rigidity and is capable of transmitting large torque.