Flex Spline Geometry for Torque, Compliance, and Load Distribution
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Solution Overview
Problem
Conventional strain wave drives for rotary actuation of flight control surfaces in aircraft require large and heavy gear systems due to the need for high torque and compactness, with existing flex splines adding complexity and cost through built-in compliance for load distribution and engagement.
Innovation Solution
A straight tubular flex spline with sections of changed geometry, such as perforations, thinner sections, or corrugations, is used to provide compliance and flexibility, reducing weight and size while maintaining torsional stiffness and load distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional strain wave drives use built-in compliance for load distribution and engagement, then reliability and load distribution improve, but device complexity and manufacturing cost increase
Solution Approach 1:
The flex spline incorporates sections of changed geometry with specific geometric features (perforations, thinner sections, or corrugations) at localized positions along the body. These local modifications provide compliance specifically in regions where it is needed for load distribution and tooth engagement, while maintaining structural integrity and minimizing overall complexity in other regions of the flex spline.
2Reliability
If conventional strain wave drives use built-in compliance for correct engagement, then tooth engagement reliability improves, but manufacturing complexity and cost increase
Solution Approach 1:
Rather than implementing compliance mechanisms throughout the entire flex spline structure, the invention applies geometric features only in specific localized sections where compliance is required for proper tooth engagement. This localized approach simplifies manufacturing compared to global compliance mechanisms while ensuring reliable engagement where needed.
3Ease of manufacture
If flex spline uses uniform geometry throughout, then manufacturing is simpler, but flexibility and torsional stiffness are compromised
Solution Approach 1:
The flex spline employs sections of changed geometry with specific geometric features in certain regions while maintaining uniform geometry in other regions. This allows the structure to achieve the necessary flexibility and torsional stiffness in critical areas without overly complicating the overall manufacturing process, as the non-uniform sections are integrated into the existing manufacturing workflow.
4Force
If conventional gear systems are used for high torque, then torque capability is achieved, but size and weight increase
Solution Approach 1:
The invention utilizes a flex spline with a tubular body that incorporates geometric features to provide the necessary flexibility and strength for high torque transmission. This flexible structure replaces traditional rigid gear systems, achieving comparable torque capability with significantly reduced weight by using a thin-walled tubular construction with strategic geometric modifications.
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 solution allows for full torque and deformation capability without compromising design space, manufacturing, assembly, cost, and weight, while enhancing flexibility and torsional stiffness through geometric features that vary along the flex spline body.
Implementation Method 1
the body further comprises one or more sections of changed geometry located between the first and second sets of teeth and/or the second and third sets of teeth, the sections of changed geometry being provided with a geometric feature in the flex spline body that is not present in the remainder of the flex spline body
Data Source
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AI summary
A flex spline for a strain wave drive, the flex spline comprising: a flexible tubular body (110) having a first open end (221) and a second open end (222); a first set of radially outwardly extending teeth around its outer periphery at the first open end; a second set of radially outwardly extending teeth around its outer periphery at the second open end; and a third set of radially inwardly outwardly teeth located axially between the first and the second sets of teeth; and wherein the body further comprises one or more sections of changed geometry located between the first and second sets of teeth and/or the second and third sets of teeth, the sections of changed geometry being provided with a geometric feature in the flex spline body that is not present in the remainder of the flex spline body.