Flexible Internally Toothed Gear for Strain Wave Gearing
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Solution Overview
Problem
Existing strain wave gearings face challenges in achieving uniform meshing between the externally and internally toothed gears, leading to variations in transmission and strength characteristics due to manufacturing and assembly precision issues.
Innovation Solution
The strain wave gearing employs a flexible internally toothed gear that can flex radially and is supported by a floating ring, while the externally toothed gear is caused to flex in a non-circular shape by a wave generator, resulting in an overlapping meshing state between the two gears.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a rigid internally toothed gear is used, then manufacturing and assembly are simplified, but meshing uniformity deteriorates due to coning effects in cup-shaped externally toothed gears
Solution Approach 1:
The internally toothed gear is changed from a rigid structure to a flexible structure capable of radial flexing. This parameter change allows the gear to adapt its shape to compensate for coning effects in the externally toothed gear, thereby maintaining uniform meshing characteristics without requiring high manufacturing precision
Solution Approach 2:
The internally toothed gear is designed with dynamic flexibility in the radial direction, allowing it to flex and change shape during operation. This dynamic capability enables the gear to maintain optimal meshing contact with the externally toothed gear despite variations in manufacturing and assembly precision
2Manufacturing precision
If pronounced relieving and tooth-profile shifting are applied to external teeth, then meshing differences are mitigated, but device complexity increases
Solution Approach 1:
Instead of modifying the externally toothed gear with complex relieving and profile shifting operations, the invention inverts the approach by making the internally toothed gear flexible. This allows the internal gear to adapt to the external gear's geometry, achieving uniform meshing without complex modifications to the external teeth
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 mitigates differences in meshing at tooth-trace-direction positions, enhancing the transmission and strength characteristics of the strain wave gearing by maintaining a consistent meshing state and reducing rotational variations.
Implementation Method 1
a flexible internally toothed gear capable of flexing in a radial direction
Implementation Method 2
a wave generator fitted inside the externally toothed gear so as to be capable of relative rotation, the wave generator causing the externally toothed gear to flex in a non-circular shape
Data Source
Figure 1A~1B
Figure 2
Figure 3A~3C
AI summary
In a strain wave gearing (1), a flexible externally toothed gear (4) flexed by a wave generator (5) meshes with a flexible internally toothed gear (2) while in an overlapping meshing state. A floating ring (25), which supports the internally toothed gear (2) from the outer circumferential side, maintains the overlapping state of the meshing and supports the internally toothed gear (2) in a floating state that allows displacement following a state of radial flexion in the tooth trace direction of the internal teeth (2a) of the internally toothed gear. Differences between the meshing states of both gears (2, 4) can be alleviated at each position in the tooth trace direction. Degradation in the transmission characteristics and the strength characteristics of the strain wave gearing caused by manufacturing dimensional accuracy of each component and assembly accuracy can be suppressed.