Harmonic Drive Flex Ring Asymmetry for Energy Management
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Solution Overview
Problem
Existing harmonic drives used in electric camshaft adjusters and internal combustion engine compression ratio adjustment lack efficient energy management and precise control, particularly due to the rigid nature of their components which do not effectively utilize stored spring energy for stable positioning and low energy consumption.
Innovation Solution
A harmonic drive with a flexible, externally toothed gear component that exhibits an out-of-round shape, storing spring energy that fluctuates with angular position, utilizing these fluctuations to maintain preferred positions through a snap moment, reducing the energy required for holding positions and potentially eliminating the need for additional torque, by exploiting self-aligning torque and featuring a polygon or elliptical shape to manage stress and equilibrium.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a circular flex ring is used in conventional harmonic drives, then the structure is simple and easy to manufacture, but the spring energy is not effectively utilized for stable positioning
Solution Approach 1:
The patent applies asymmetry by changing the flex ring from a circular shape to a polygonal shape with out-of-round geometry. This asymmetric configuration creates varying spring energy storage capabilities at different angular positions, enabling stable positioning through snap moments while reducing the energy required to maintain position compared to conventional circular flex rings.
2Measurement precision
If the flexible gear component is made more compliant to improve positioning, then the control precision improves, but the material stress increases leading to potential failure
Solution Approach 1:
The patent applies local quality by strategically rounding only the corners of the polygonal flex ring while maintaining the out-of-round geometry. This localized modification reduces stress concentration at critical points (corners) where stress is highest, while preserving the overall compliant behavior and snap moment characteristics needed for precise angular positioning control.
3Use of energy by moving object
If conventional rigid components are used, then the structure is simple, but the system cannot effectively exploit self-aligning torque for energy reduction
Solution Approach 1:
The patent applies dynamics by transforming the rigid gear component into a flexible, polygonal-shaped component that can dynamically adapt its shape during operation. This dynamic flexibility enables the component to exploit self-aligning torque and generate snap moments that reduce energy consumption for position holding, while the polygonal geometry provides a manageable level of complexity for manufacturing.
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 harmonic drive achieves precise control and low energy consumption by utilizing the snap moment to maintain stable positions, reducing energy requirements and allowing for efficient operation with minimal external energy input, especially in high transmission ratios, ensuring stable and precise angular adjustments with reduced material stress.
Implementation Method 1
the spring energy, which is stored in the flexible, externally toothed gear component of the harmonic drive according to the invention, is subject to permanent fluctuations during the operation of the wave generator
Data Source
AI summary
A harmonic drive (1), including a wave generator (8), a flexible, externally toothed gear component (14), in particular in the form of a flex ring, which can be deformed by said wave generator, and at least one internally toothed gear component (4, 5) that meshes with the flexible, externally toothed gear component (14). The flexible, externally toothed gear component (14) has a non-circular basic shape in relation to its mechanically non-loaded state.