Offset-Lever Centrifugal Clutch for Compact High-Torque Gearboxes
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Solution Overview
Problem
Turboprop engines for small airplanes face challenges due to high fuel consumption and inefficiency when downscaled, making them economically unfeasible for smaller aircraft.
Innovation Solution
A centrifugal clutch design featuring an input assembly with levers that have weights and friction pads, where the pivot axis is laterally offset, allowing for minimized clutch size and increased friction force without the need for a hollow cylindrical member on the output side.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a conventional centrifugal clutch with weights and friction pads rotating within a hollow cylindrical body is used, then the clutch can transmit torque through centrifugal forces, but the overall dimension and diameter of the clutch become large
Solution Approach 1:
The patent inverts the conventional clutch architecture by moving the friction pads outward to engage with an outer cylindrical surface rather than having weights press inward against an inner hollow cylindrical body. This inversion allows the clutch to achieve the same torque transmission function with a more compact overall dimension, as the friction engagement occurs at the outer perimeter where leverage is maximized
Solution Approach 2:
The patent transitions from a conventional radial engagement scheme to a tangential engagement scheme by arranging friction pads to contact the outer cylindrical surface tangentially. This dimensional change in the engagement geometry allows for more efficient torque transmission with reduced clutch diameter, as the tangential force application maximizes the moment arm
2Force
If the mass of weights in the centrifugal clutch is increased to generate higher friction forces, then the friction force increases, but the weight and overall size of the clutch increases
Solution Approach 1:
The patent introduces a lever mechanism as an intermediary between the weights and friction pads. The lever amplifies the centrifugal force generated by the weights and directs it tangentially to the friction pads, allowing smaller weights to generate sufficient friction force through mechanical advantage rather than relying on weight alone
Solution Approach 2:
The patent changes the engagement parameter from radial to tangential, which fundamentally alters the force transmission mechanism. This parameter change allows the system to achieve higher friction forces with lighter weights by utilizing the tangential component of centrifugal force combined with lever mechanical advantage, rather than relying solely on radial weight compression
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 centrifugal clutch achieves a compact size and high torque transmission capability, suitable for small turboprop engines, by optimizing the lever design and mass distribution, thus reducing the overall size and weight of the turboprop engine.
Implementation Method 1
During operation, the weights on the first lever arms are forced outwardly by centrifugal forces thus forcing the friction pads on the second lever arms inwardly and towards a cylindrical outer surface of the cylinder body of the output assembly
Implementation Method 2
the friction between the friction pads and the inner wall of the hollow cylindrical member is strong enough to make the hollow cylindrical member and the output shaft rotating with the speed of the input shaft
Data Source
Figure 1
Figure 2
Figure 3a~3b
AI summary
The invention concerns a centrifugal clutch (32) in particular a centrifugal clutch (32) for a small turboprop engine (10). The centrifugal clutch (32) comprises an input assembly (32.1) with a lever carrier (50). A plurality of levers (52) are pivotally connected to the lever carrier (50) allowing each lever (52) to pivot around a pivot bearing (52.3) with a pivot axis, thus defining two lever arms (52.1, 52.2) that extend in opposite directions from the pivot axis, wherein. A first lever arm (52.1) is provided with a weight (54) while a second lever arm (52.2) is provided with a friction pad (56). The pivot axis for each lever (52) is arranged laterally offset from a central axis of rotation of the input assembly. The centrifugal clutch (32) comprises an output assembly (32.2) that comprises a cylinder body (6) coaxially arranged with the central axis of the input assembly.