Wave Gear Tooth Trace Geometry for Lower-Cost Robot Arms
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Solution Overview
Problem
The high dimensional accuracy required in wave gear devices for robot arms makes them costly and difficult to reduce costs, as the tooth contact strength is determined by the accuracy of the gears and wave generator.
Innovation Solution
A gear device with an internal gear, a flexible external gear, and a wave generator that adjusts the meshing position in a circumferential direction, where the tooth trace of the internal gear intersects with the rotation axis, allowing for adjustable tooth contact strength without excessive dimensional accuracy, using a spacer to change the relative position of the gears.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the tooth contact strength is determined only by the dimensional accuracy of the gears and wave generator, then the gear device achieves reliable meshing, but the manufacturing cost increases due to the requirement for high dimensional accuracy
Solution Approach 1:
The patent changes the geometric parameters of the gear teeth by making the tooth trace direction non-parallel to the rotation axis. This parameter change allows the tooth contact strength to be determined by the tooth trace direction angle rather than solely by dimensional accuracy, thereby reducing the required manufacturing precision while maintaining reliability
Solution Approach 2:
The patent introduces asymmetry in the gear tooth design by setting the tooth trace direction at an angle to the rotation axis. This asymmetric configuration creates a mechanical advantage where the tooth contact strength is influenced by the angular orientation rather than just the dimensional precision, allowing for cost reduction while maintaining performance
2Device complexity
If the tooth trace direction is parallel to the rotation axis, then the gear structure is simplified, but the manufacturing cost increases due to the need for high dimensional accuracy
Solution Approach 1:
The patent changes the tooth trace direction parameter from parallel (0 degrees) to non-parallel (at an angle) to the rotation axis. This parameter change fundamentally alters how tooth contact strength is achieved, shifting from reliance on dimensional accuracy to reliance on geometric configuration, thereby reducing manufacturing costs
Solution Approach 2:
The patent introduces a dynamic element to the gear design where the tooth trace direction can be adjusted by changing the relative positions of the internal gear and external gear. This dynamic adjustability allows optimization of tooth contact strength without requiring high dimensional accuracy, reducing manufacturing complexity and cost
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 design reduces the need for high dimensional accuracy, lowering production costs while maintaining effective meshing and durability of the gear device.
Implementation Method 1
a flexible external gear provided inside of the rigid internal gear, and an elliptically contoured wave generator fitted inside of the flexible external gear. Here, the rigid internal gear and the flexible external gear have a difference in number of teeth, and the flexible external gear is flexed in an elliptical shape by the wave generator
Data Source
AI summary
A gear device includes an internal gear, an external gear partially meshing with the internal gear, relatively rotating around a rotation axis to the internal gear, and having flexibility, and a wave generator being in contact with an inner circumferential surface of the external gear and moving a meshing position of the internal gear and the external gear in a circumferential direction about the rotation axis, wherein a virtual straight line as an extension of a tooth trace of the internal gear intersects with the rotation axis in a sectional view cut along a plane containing the rotation axis.