Coaxial Helicopter Pitch Control Device
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Solution Overview
Problem
Current coaxial double-propeller helicopter pitch control systems face issues with long motion transmission distance, complex structures, poor mechanical rigidity, and high manufacturing difficulties, leading to reduced precision and stability.
Innovation Solution
A centrally positioned pitch control device is introduced, featuring a central shaft with a stepped cross arm, conical gears, sector reversing gears, and a gear box, which reduces the transmission distance and simplifies the structure by directly controlling the upper and lower propeller hubs through interconnected swash plates and rocker mechanisms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the steering gear controls the lower swash plate to control upper propeller variable pitch via a link mechanism, then the upper propeller variable pitch can be controlled, but the transmission distance is long, the structure is complicated, and the control precision deteriorates
Solution Approach 1:
The pitch control system is segmented into independent control paths: the lower propeller pitch is controlled directly by the steering gear through the lower swash plate, while the upper propeller pitch is controlled independently through the connecting rod and upper swash plate, eliminating the need for a complex link mechanism that transferred motion from lower to upper control
Solution Approach 2:
The connecting rod serves as an intermediary element that directly connects the steering gear to the upper swash plate, providing a simplified transmission path that reduces the number of intermediate links and improves control precision while maintaining the ability to control upper propeller pitch
2Ease of manufacture
If the connecting rod controls upper propeller pitch through the whole central shaft, then the upper propeller pitch can be controlled, but the motion transmission distance is long and the manufacturing difficulty increases
Solution Approach 1:
Instead of transmitting motion from the lower end of the central shaft upward to control the upper propeller, the control is inverted by having the steering gear directly control the upper swash plate through the connecting rod, eliminating the need for long-distance motion transmission through the entire central shaft
3Manufacturing precision
If the steering gear controls lower swash plate for upper propeller variable pitch, then the control function is achieved, but the accumulated error of fit clearances of many links is large
Solution Approach 1:
The control system is divided into separate control paths for upper and lower propellers, with the upper propeller control being directly linked to the steering gear through the connecting rod and upper swash plate, thereby eliminating multiple intermediate links and their associated fit clearances that would accumulate errors
Solution Approach 2:
The connecting rod acts as a direct intermediary between the steering gear and upper swash plate, creating a simplified transmission path with fewer intermediate connections, thereby reducing the accumulation of fit clearance errors and improving control reliability
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 solution enhances control precision and stability, reduces manufacturing complexity, and conserves space, resulting in a more efficient and reliable pitch control system for coaxial double-propeller helicopters.
Implementation Method 1
conical gear I 26 meshing with the lower part of the sector reversing gear 24; conical gear II 22 meshing with the upper part of the sector reversing gear 24
Implementation Method 2
upper swash plate 5 and a lower swash plate 15, the upper swash plate 5 and the lower swash plate 15 respectively controlling variable pitch of the upper propeller and the lower propeller
Implementation Method 3
outer ends of the upper variable pitch ring 3 and the lower variable pitch ring 14 are respectively provided with a rocker I 7 and a rocker 11 12, with the outer ends of the rocker I 7 and the rocker II 12 respectively hinging with the upper swash plate 5 and the lower swash plate 15 via a connecting rod I 6 and a connecting rod II 13
Data Source
Figure 1
Figure 2
AI summary
The present invention provides a centrally positioned pitch control device for a coaxial double-propeller helicopter, belonging to the technical field of helicopter structure. The coaxial double-propeller helicopter comprises an upper propeller hub (2) and a lower propeller hub (18); a blade I (1) being mounted on the outside of the upper propeller hub (2); and a blade II (16) being mounted on the outside of the lower propeller hub (18), characterized in that said centrally positioned pitch control device is located between the upper propeller hub (2) and the lower propeller hub (18). The centrally positioned pitch control device is located at the middle part of a central shaft (19) between the upper propeller hub (2) and the lower propeller hub (18). The centrally positioned pitch control device may shorten the motion transmission distance, decrease the number of conversion links, enhance the control precision and stability, and reduce the manufacturing difficulty.