Strain Wave Drive Cam Profile for Uniform Gear Load Distribution
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Solution Overview
Problem
Conventional strain wave drives for rotary actuation in aircraft require additional components for compliance, increasing cost, complexity, size, and weight due to uneven load distribution and interference between meshing gears.
Innovation Solution
A strain wave drive with a modified wave generator cam surface featuring a curved profile and self-aligning roller bearings to ensure uniform load distribution, eliminating the need for additional compliance components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional strain wave drives are designed with built-in compliance components to ensure correct load distribution and engagement, then reliability and correct operation are improved, but device complexity, manufacturing cost, size, and weight increase
Solution Approach 1:
The invention extracts and eliminates the need for additional compliance components from the strain wave drive system. By modifying the cam surface geometry of the wave generator to be curved rather than cylindrical, the system achieves uniform load distribution without requiring separate compliance elements, thus reducing device complexity while maintaining reliability
Solution Approach 2:
The invention changes the geometric parameter of the wave generator from a cylindrical shape to a curved cam surface profile. This parameter change allows the system to inherently provide compliance and uniform load distribution through the cam surface geometry itself, eliminating the need for additional compliance components and reducing overall system complexity
2Reliability
If conventional strain wave drives are designed with built-in compliance components to ensure correct load distribution and engagement, then reliability and correct operation are improved, but manufacturing cost increases
Solution Approach 1:
The invention removes the need for separate compliance components from the design. By integrating the compliance function directly into the cam surface geometry of the wave generator, the system reduces the number of parts that need to be manufactured and assembled, thereby reducing manufacturing cost while maintaining correct load distribution and engagement
Solution Approach 2:
The invention merges the compliance function with the wave generator structure itself. The curved cam surface of the wave generator simultaneously provides both the driving motion and the compliance needed for uniform load distribution, eliminating the need for separate compliance components and reducing manufacturing complexity and cost
3Reliability
If conventional strain wave drives are designed with built-in compliance components to ensure correct load distribution and engagement, then reliability and correct operation are improved, but size and weight increase
Solution Approach 1:
The invention extracts and eliminates additional compliance components from the strain wave drive system. By modifying the cam surface geometry of the wave generator to be curved rather than cylindrical, the system achieves uniform load distribution without requiring separate compliance elements, thus reducing weight while maintaining reliability
Solution Approach 2:
The invention merges the compliance function with the wave generator structure itself. The curved cam surface of the wave generator simultaneously provides both the driving motion and the compliance needed for uniform load distribution, eliminating the need for separate compliance components and reducing overall system weight
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
Reduces manufacturing costs and complexity while maintaining compactness and reliability by ensuring uniform stress distribution and reducing interference between meshing gears.
Implementation Method 1
roller bearings provided between the cam surface and the flex spline
Implementation Method 2
the flex spline takes up the elliptical form of the wave generator shaft
Data Source
AI summary
A strain wave drive includes an elliptical wave generator shaft rotatable about an axis (X), a flexible flex spline mounted around the wave generator shaft and a ring gear assembly mounted around the flex spline. The ring gear assembly includes an output ring gear having a circular inner periphery and is sandwiched between two earth ring gears each having a circular inner periphery. The flex spline has a first number of radially outwardly extending teeth around its outer periphery and each earth ring gear has the first number of radially inwardly extending teeth to engage with the teeth of the flex spline.