Downstream Torque Limiter Braking Input Shaft
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Solution Overview
Problem
In aircraft secondary flight control systems, traditional torque limiters face challenges in setting the torque limit due to temperature and efficiency changes over time, leading to either inadequate torque transmission at low efficiency and high drag or excessive torque transmission at high efficiency and low drag, necessitating over-engineering of components to withstand potential torque.
Innovation Solution
Positioning the torque limiter downstream of the gear unit and applying a brake to the input shaft when overtorque conditions are detected, allowing the torque limiter's limit to be set closer to the ideal value, thus enabling lighter and smaller component design by eliminating the need to accommodate efficiency and drag bandwidths of the gear unit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the torque limiter limit is set high to ensure sufficient torque transmission at low efficiency and high drag conditions, then adequate torque transmission is achieved, but excessive torque is transmitted to components at high efficiency and low drag conditions, requiring over-engineering
Solution Approach 1:
The torque limiter is made adjustable rather than fixed, allowing the limit to be dynamically changed based on operating conditions. The system includes a controller that receives feedback about drive train conditions and adjusts the torque limiter setting accordingly, transforming a static component into a dynamic one that adapts to varying efficiency and drag conditions
Solution Approach 2:
The torque limiter's limiting parameter is made variable through electronic control. The controller modifies the torque limit parameter based on measured or estimated drive train efficiency and drag conditions, allowing optimal torque transmission when needed while preventing excessive torque when conditions are favorable
2Strength
If the torque limiter limit is set low to minimize design loads on aircraft structure, then structural loads are reduced, but the torque limiter trips during normal operation when efficiency is low and drag is high, causing system arrest
Solution Approach 1:
The torque limiter transitions from a fixed static device to a dynamic adjustable device. The controller continuously monitors drive train conditions and adjusts the torque limiter setting in real-time, allowing the system to maintain low limits for structural protection while raising limits when operating conditions require higher torque transmission
Solution Approach 2:
The system incorporates feedback mechanisms that monitor drive train efficiency and drag conditions. This feedback enables the controller to distinguish between normal high-drag conditions that require higher torque and actual fault conditions, adjusting the torque limiter accordingly to prevent nuisance tripping while maintaining structural protection
3Device complexity
If a traditional torque limiter is positioned upstream of the gear unit, then torque limitation is applied at the source, but the efficiency and drag bandwidths of the gear unit must still be accommodated by downstream components
Solution Approach 1:
The torque limiter is made adjustable with its limit parameter dynamically controlled based on actual drive train conditions. This dynamic adjustment eliminates the need to design downstream components for worst-case scenarios, as the torque limiter adapts to actual operating conditions rather than accommodating maximum possible torque variations
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 minimizes the size and weight of components downstream of the torque limiter, reducing the overall weight and size of the actuator system while ensuring safe operation by preventing excessive torque buildup, thereby optimizing aircraft design and reducing fuel consumption and emissions.
Implementation Method 1
the torque limiter is adapted such that when it experiences a torque above its torque limit it applies a brake to said input shaft
Data Source
AI summary
A torque limited drive system comprising: an input shaft; at least one gear unit driven by the input shaft; a torque limiter having a torque limit and being driven by the at least one gear unit; and a torque limited output shaft driven by the torque limiter; wherein the torque limiter is adapted such that when it experiences a torque above its torque limit it applies a brake to said input shaft. The fact that the torque limiter is situated downstream of the gear units combined with the fact that the torque limiter brakes the input shaft upstream of the gear unit allows minimization of component weight within the gear units and within equipment driven by the output shaft due to the removal of the effect of efficiency and drag bandwidths associated with the gear units.