Strain Wave Gearing Ratcheting for Integrated Overload Protection
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Solution Overview
Problem
Prior rotation transmission mechanisms face issues with increased mass and assembly errors due to the addition of torque limiters and other components to prevent damage from overloading, which complicates the powertrain and increases dimensions.
Innovation Solution
A rotation transmission mechanism utilizing a strain wave gearing as a speed reducer, where the strain wave gearing is designed to function as a mechanical fuse by adjusting the tooth depth, fastening force, or flexure of its gears to absorb overload, thereby preventing damage to other powertrain components without adding additional components like torque limiters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a torque limiter is added to the power transmission path to prevent overload damage, then component protection is improved, but device complexity and mass increase
Solution Approach 1:
The patent combines the speed reducer and torque limiting functions into a single integrated strain wave gearing unit. The strain wave gearing simultaneously performs speed reduction and acts as a mechanical fuse that slips when overload occurs, eliminating the need for a separate torque limiter component while maintaining both protection and speed reduction functions.
Solution Approach 2:
The strain wave gearing is designed to perform multiple functions: it serves as both the speed reducer and the overload protection device. By making the strain wave gearing slip under overload conditions, it universally provides both motion control and safety protection functions within a single component.
2Reliability
If a torque limiter is added to prevent overload damage, then component protection is improved, but mass increases
Solution Approach 1:
The patent merges the torque limiter and speed reducer into one integrated strain wave gearing component. This eliminates the need for additional mass from separate torque limiter components while maintaining the protective function through the inherent slipping characteristic of the strain wave gearing under overload conditions.
3Reliability
If additional components like torque limiters are added, then overload protection is improved, but assembly precision requirements increase
Solution Approach 1:
By integrating the torque limiting function into the strain wave gearing itself, the patent eliminates the need for precise assembly between separate torque limiter and speed reducer components. The single integrated component reduces cumulative assembly errors while providing reliable overload protection through the strain wave gearing's slipping mechanism.
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 strain wave gearing effectively absorbs overload, preventing damage to other components by ratcheting and functioning as a mechanical fuse, maintaining the speed reduction functionality while ensuring the powertrain components are protected from excessive load.
Implementation Method 1
a strain wave gearing provided with a rigid internally toothed gear, a flexible externally toothed gear disposed on the inner side of the internally toothed gear, and an ellipsoidally contoured wave generator fitted to the inner side of the flexible externally toothed gear. The externally toothed gear is made to flex into an ellipsoidal shape by the wave generator
Data Source
AI summary
In a rotation transmission mechanism that transmits the rotational driving force of a motor to a load-side member via a speed reducer, a strain wave gearing is used as the speed reducer, and the allowable load torque of members in the powertrain other than the strain wave gearing is greater than a predetermined upper-limit load torque. The allowable load torque of the strain wave gearing is dictated by the ratcheting torque, which is set so as not to exceed the upper-limit load torque. In an overload state, ratcheting is generated in the strain wave gearing, so that the strain wave gearing functions as a mechanical fuse. Other power transmission members can be protected from an overload state without adding a separate member such as a torque limiter.