Compact Belted Strain Wave Gear With Circular Tooth Engagement
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Solution Overview
Problem
Traditional harmonic drive gearing systems face challenges with high noise, vibration, and harshness (NVH) due to increased forces on the flexspline, which reduces fatigue life and positional accuracy, and are not adaptable to different vehicle architectures while maintaining a compact and lightweight design.
Innovation Solution
A wave gear apparatus with a spline, wave generator, and belt system where the belt has fewer teeth than the spline, allowing for reduced rotational speed and increased torque, and made from elastomeric materials to minimize NVH, featuring a unique teeth profile for efficient engagement and assembly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If traditional harmonic drive gearing uses an elliptical wave generator with two fewer teeth on the flexspline than the circular spline, then the teeth mesh in two zones increasing torque capacity, but the forces on the flexspline greatly increase reducing fatigue life and the system becomes unbalanced increasing noise and vibration
Solution Approach 1:
The patent uses a circular wave generator instead of an elliptical one, creating a different meshing pattern where teeth engage in a single zone rather than two diametrically opposed zones. This asymmetric change in the wave generator geometry redistributes the contact forces, maintaining torque capacity while reducing the peak forces that cause noise and vibration.
Solution Approach 2:
The patent changes the tooth count relationship from the traditional two-tooth difference to a one-tooth difference between the flexspline and circular spline. This parameter change modifies the meshing characteristics and force distribution, reducing the harmful forces on the flexspline while maintaining adequate torque capacity.
2Power
If traditional harmonic drive gearing uses an elliptical wave generator with two fewer teeth, then torque capacity increases, but fatigue life of the flexspline is greatly reduced
Solution Approach 1:
By using a circular wave generator instead of an elliptical one, the patent creates a different stress distribution pattern on the flexspline. The single-zone meshing approach reduces peak contact forces and their cyclic variations, thereby extending the fatigue life of the flexspline while maintaining sufficient torque capacity through optimized tooth geometry and material selection.
Solution Approach 2:
Changing the tooth difference from two to one, and optimizing the tooth profiles and dimensions, the patent reduces the stress amplitude on the flexspline during operation. This parameter optimization allows the system to achieve the required torque capacity with lower cyclic stresses, significantly improving fatigue life.
3Power
If traditional harmonic drive gearing is designed for high torque capacity, then the system becomes unbalanced, but positional accuracy is reduced
Solution Approach 1:
The circular wave generator design creates a more balanced force distribution compared to the elliptical design. By meshing teeth in a single zone rather than two opposed zones, the system maintains better rotational balance, reducing vibrations that would compromise positional accuracy while still achieving high torque capacity through optimized engagement geometry.
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 wave gear apparatus achieves reduced noise, vibration, and harshness levels, enhanced positional accuracy, and adaptability to various vehicle architectures while maintaining a compact and lightweight design, improving the overall performance and reliability of the system.
Implementation Method 1
The belt is made from an elastomeric material to minimize NVH
Implementation Method 2
The belt includes a plurality of belt teeth extending radially outwardly from the belt for engaging the spline teeth
Data Source
AI summary
A wave gear apparatus comprises a spline having top, bottom, exterior, and interior surfaces. A plurality of spline teeth extend from the interior surface toward a center axis. A wave generator is rotatably disposed in the spline. A belt extends about the wave generator. The belt includes a plurality of belt teeth extending radially outwardly from the belt whereby a total number of the belt teeth is less than a total number of the spline teeth. An output member defines a recess receiving the wave generator and the belt whereby, in response to a rotational movement from the wave generator, the output member rotates in a direction same or opposite of the wave generator. A vehicle lifting system including the wave gear apparatus is also disclosed herein.