Strain Wave Gear Tooth-Recess Coupling for Flex Gear Stress Relief
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Solution Overview
Problem
Existing strain wave gear devices face issues with unwanted stress and twisting forces due to non-uniform force vectors and complex structures, leading to potential failure and difficulty in accurately mounting transmission pins.
Innovation Solution
A strain wave gear device with a simplified structure featuring a flex gear with a ring-shaped outer gear and an inner gear, where the cam has N poles that engage at N positions, and transmission pairs with teeth and recesses that tolerate relative displacement, reducing unwanted stress and twisting forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If transmission pins are mounted into the flex gear to transmit force, then torque transmission is improved, but the flex gear becomes fragile and mounting becomes difficult
Solution Approach 1:
The patent removes the transmission pins from the flex gear entirely. Instead, the flex gear's outer peripheral surface directly engages with the inner peripheral surface of the rigid gear, eliminating the need for transmission pins and thereby preventing the flex gear from becoming fragile due to pin mounting.
Solution Approach 2:
The patent merges the force transmission function directly into the gear engagement surfaces. The flex gear's outer peripheral surface and the rigid gear's inner peripheral surface directly contact and transmit force without intermediate transmission pins, simplifying the structure and improving reliability.
2Force
If the cam has N poles engaging at N positions, then force distribution is improved, but the structure becomes more complex
Solution Approach 1:
The cam is segmented into N poles positioned at equal intervals around its circumference. Each pole independently engages with the flex gear at a specific position, distributing the force transmission across multiple contact points. This segmentation achieves uniform force distribution while maintaining a relatively simple cam structure.
3Adaptability or versatility
If the recess width is wider than the transmission tooth, then relative displacement tolerance is improved, but transmission precision may be reduced
Solution Approach 1:
The recess in the rigid gear is designed with a width greater than the transmission tooth width, creating a local tolerance zone. This allows for relative displacement between the flex gear and rigid gear without compromising the overall engagement, while the tooth-recess geometry maintains sufficient transmission 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 solution effectively reduces the risk of failure by distributing force evenly and preventing unwanted stress, enhancing transmission efficiency and preventing flex gear breakage while maintaining a compact and easy-to-produce design.
Implementation Method 1
The cam has N poles, N being an integer of 2 or greater, positioned at equal intervals in a circumferential direction centered on the axis and causes the outer gear to engage with the inner gear at N positions
Implementation Method 2
a flex gear including an outer gear having a ring shape, formed along an outer peripheral surface of the flex gear
Data Source
AI summary
A strain wave gear device includes: an internal gear; a wave generator; a flex gear including an outer gear and a first annular portion integrally formed with the outer gear of the same material; and an outputter that rotates together with the flex gear and includes a second annular portion facing against the first annular portion in a radial direction centered on an axis. The second annular portion is provided with a transmission tooth protruding radially while the first annular portion is provided with a recess to receive the transmission tooth. The recess is circumferentially wider than the transmission tooth and tolerates relative circumferential displacement of the flex gear with respect to the outputter. Transmission pairs, each including the transmission tooth and the recess, are circumferentially arranged.