Flight Control Gear Backlash Elimination via Friction Drive
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Solution Overview
Problem
Backlash in gear arrangements of flight control systems, such as thrust control levers, leads to loss of accuracy due to the clearance between gear teeth, which affects the precision of position sensors and the transmission of control signals.
Innovation Solution
Incorporating a friction drive mechanism with synchronous rotary elements, where a first rotary element on one axle frictionally drives a second rotary element on another axle, eliminating backlash by maintaining constant contact and transmitting torque without play, even at low levels of torque.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a gear train is used to transmit drive from the control lever, then mechanical advantage and torque multiplication are achieved, but backlash occurs due to clearance between gear teeth resulting in loss of accuracy
Solution Approach 1:
The patent combines a friction drive mechanism with a gear train in a hybrid configuration. The friction drive comprises a friction wheel that contacts and drives a friction-driven gear, while the gear train provides torque multiplication. This merging allows the system to benefit from both the zero-backlash characteristic of friction drive and the mechanical advantage of gear trains, resolving the contradiction between torque multiplication and position accuracy.
2Reliability
If clearance is provided between gear teeth to prevent jamming and allow lubrication, then gear reliability is improved, but backlash occurs resulting in loss of control signal accuracy
Solution Approach 1:
The patent merges friction drive and gear train mechanisms, where the friction drive component eliminates backlash through continuous contact while the gear train maintains reliability through controlled clearance. The friction wheel maintains constant contact with the friction-driven gear, ensuring accurate position transmission, while the gear teeth clearance is maintained for reliability.
3Measurement precision
If a spring-loaded split gear is used to eliminate backlash, then position accuracy is improved, but device complexity increases
Solution Approach 1:
The patent combines friction drive with a simple gear train, avoiding the complexity of spring-loaded split gears. The friction drive mechanism provides backlash elimination through its inherent continuous contact characteristic, while the gear train provides torque multiplication with simple meshing gears, resulting in a less complex overall system compared to spring-loaded solutions.
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 friction drive mechanism ensures zero or substantially zero backlash, enhancing the accuracy and reliability of the control system by immediately transmitting drive from the control lever to the position sensor, regardless of gear contact, thereby improving the overall precision and responsiveness of the flight control system.
Implementation Method 1
a friction drive comprising a first rotary element mounted on the first axle arranged to frictionally drive a second rotary element mounted on the second axle
Data Source
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AI summary
A gear arrangement comprising a gear train (1) having a first gear (10) on a first axle (12) and a second gear (20) on a second axle (22), the first and second gears (10, 20) arranged to intermesh, characterised in that the gear arrangement is provided with a friction drive (2) comprising a first rotary element (14) mounted on the first axle (12) arranged to frictionally drive a second rotary element (24) mounted on the second axle (22).