3D Tooth Profile in Strain Wave Gears for Interference-Free Meshing
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Solution Overview
Problem
Existing cup-shaped or top-hat-shaped strain wave gearing technologies face difficulties in achieving three-dimensional meshing due to restrictions in tooth cutting processes, making it challenging to create tooth profiles with varying tooth thickness, pressure angle, and tooth depth along the tooth trace direction without interference.
Innovation Solution
The solution involves forming three-dimensional tooth profiles for both internal and external teeth, where the internal teeth have a basic profile at the outer end and a proportionally reduced profile at other positions, and the external teeth have a basic profile at the outer end and a proportionally increased profile along the tooth trace direction, ensuring easy cutting and preventing interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a three-dimensional tooth profile with varying tooth thickness, pressure angle, and tooth depth is implemented, then three-dimensional meshing is achieved, but tooth cutting process becomes difficult
Solution Approach 1:
The patent applies parameter changes by systematically varying tooth thickness, pressure angle, and tooth depth along the tooth trace direction. These parameter variations enable three-dimensional meshing while maintaining compatibility with conventional tooth cutting processes, resolving the contradiction between manufacturing precision and ease of manufacture
Solution Approach 2:
The patent implements local quality by creating different tooth profile characteristics at different positions along the tooth trace. The tooth thickness, pressure angle, and tooth depth are locally adjusted to achieve three-dimensional meshing, allowing each region of the gear to have optimized properties for its specific functional requirements
2Ease of manufacture
If external teeth have uniform tooth profile across tooth-trace-direction positions, then cutting process is simple, but meshing state varies and interference occurs
Solution Approach 1:
The patent changes the tooth profile parameters (tooth thickness, pressure angle, tooth depth) along the tooth trace direction to maintain consistent meshing state. This prevents interference between teeth while remaining compatible with manufacturing processes
Solution Approach 2:
The patent applies different tooth profile characteristics at different tooth-trace-direction positions. Each position has locally optimized tooth parameters that account for the varying flexing state of the external gear, ensuring reliable meshing without interference
3Reliability
If tooth profile is optimized for one axially perpendicular cross-section, then meshing is achieved at that position, but other positions do not form suitable meshing state
Solution Approach 1:
The patent makes each tooth-trace-direction position have its own locally optimized tooth profile. The tooth thickness, pressure angle, and tooth depth are specifically tailored for each position to achieve suitable meshing state, making the system adaptable across all positions rather than optimized for just one
Solution Approach 2:
The patent transitions from two-dimensional tooth profiles (uniform across the tooth trace) to three-dimensional tooth profiles that vary along the tooth trace direction. This dimensional change enables simultaneous optimization of meshing state at multiple positions, achieving both local and global meshing reliability
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 approach allows for seamless three-dimensional meshing across the entire tooth trace direction, alleviating restrictions in the tooth cutting process and ensuring easy processing of both internal and external teeth profiles, thereby facilitating reliable gear operation without interference.
Implementation Method 1
Each tooth of the externally toothed gear is repeatedly flexed at a given amplitude in the radial direction by the wave generator, repeatedly reaching a state of meshing with the internally toothed gear and a state of coming out of mesh with the internally toothed gear
Data Source
Figure 1(a)~1(b)
Figure 2(a)~2(c)
Figure 3
AI summary
A three-dimensional tooth profile of internal teeth (20) in a strain wave gearing (1) is a basic internal-teeth tooth profile (20(0)) at an internal-teeth outer end (20a), and is a reduced tooth profile, in which the basic internal-teeth tooth profile (20(0)) is proportionally reduced only in the lateral direction, at other tooth-trace-direction positions. A three-dimensional tooth profile of external teeth (3) is a basic external-teeth tooth profile (30(0)) at an external-teeth outer end (30a), and is an increased tooth profile, in which the basic external-teeth tooth profile (30(0)) is proportionally increased only in the lateral direction, at other tooth-trace-direction positions. The tooth tip circle of an internal-teeth inner-end (20b)-side portion of the internal teeth (20) is larger than that of other portions and does not interfere with the external teeth (30). The external teeth (30) and the internal teeth (20) mesh three-dimensionally, the teeth do not interfere at the internal-teeth inner-end (20b) side, and it is possible to realize three-dimensional tooth profiles of the external teeth (30) and the internal teeth (20) such that a tooth cutting process is easy.