Rotor Transmission Joint With Decoupled Torque and Force Paths
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Solution Overview
Problem
Current transmission joints for tilt-rotor aircrafts with elastomeric bearings face issues of reduced fatigue life, increased cost and weight, and complex maintenance due to overheating and the need for frequent inspection, which complicates the transition between 'airplane' and 'helicopter' configurations.
Innovation Solution
A transmission joint using a constant velocity joint design with rollers and dampening elements, allowing oscillation of the hub relative to the control shaft by a variable angle, and featuring independent torque and force transmission paths, eliminating the need for elastomeric components and simplifying maintenance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If elastomeric bearings are used to transmit torque and aerodynamic forces, then the transmission joint can handle both driving torque and aerodynamic forces, but the fatigue life is reduced and the cost and weight increase
Solution Approach 1:
The transmission joint is divided into two independent functional subsystems: a torque transmission subsystem using a constant velocity joint with rollers, and an aerodynamic force transmission subsystem using a spherical bearing. This segmentation allows each subsystem to be optimized for its specific function, eliminating the fatigue life problems associated with elastomeric bearings that must handle both types of loads simultaneously.
Solution Approach 2:
A spherical bearing is introduced as an intermediary component to transmit aerodynamic forces from the hub to the control shaft, while a constant velocity joint with rollers serves as a separate intermediary for torque transmission. This mediator approach allows each type of force to be transmitted through a mechanism specifically suited for that purpose, resolving the contradiction between versatility and reliability.
2Adaptability or versatility
If elastomeric bearings are used to transmit torque and aerodynamic forces, then the transmission joint can handle both driving torque and aerodynamic forces, but the cost and weight increase
Solution Approach 1:
The transmission joint is divided into two independent functional subsystems: a torque transmission subsystem using a constant velocity joint with rollers, and an aerodynamic force transmission subsystem using a spherical bearing. This segmentation allows each subsystem to be optimized for its specific function, eliminating the fatigue life problems associated with elastomeric bearings that must handle both types of loads simultaneously.
Solution Approach 2:
A spherical bearing is introduced as an intermediary component to transmit aerodynamic forces from the hub to the control shaft, while a constant velocity joint with rollers serves as a separate intermediary for torque transmission. This mediator approach allows each type of force to be transmitted through a mechanism specifically suited for that purpose, resolving the contradiction between versatility and reliability.
3Adaptability or versatility
If elastomeric bearings are used, then the transmission joint can transmit both driving torque and aerodynamic forces, but maintenance becomes complex due to overheating and contamination
Solution Approach 1:
The transmission joint is divided into two independent functional subsystems: a torque transmission subsystem using a constant velocity joint with rollers, and an aerodynamic force transmission subsystem using a spherical bearing. This segmentation allows each subsystem to be optimized for its specific function, eliminating the fatigue life problems associated with elastomeric bearings that must handle both types of loads simultaneously.
Solution Approach 2:
A spherical bearing is introduced as an intermediary component to transmit aerodynamic forces from the hub to the control shaft, while a constant velocity joint with rollers serves as a separate intermediary for torque transmission. This mediator approach allows each type of force to be transmitted through a mechanism specifically suited for that purpose, resolving the contradiction between versatility and reliability.
4Difficulty of detecting and measuring
If a long probe is used to visually inspect the articulated joint, then inspection can be performed, but the procedure becomes time-consuming
Solution Approach 1:
The spherical bearing and constant velocity joint design allows the transmission joint to be self-inspecting through visible external features. The spherical bearing's position and condition can be observed without requiring long inspection probes, and the constant velocity joint's rollers and dampening elements are accessible for visual inspection, reducing the time required for maintenance checks.
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 enhances the fatigue life, reduces weight and cost, and simplifies maintenance by decoupling torque and force transmission, preventing overheating and contamination, while allowing efficient operation across different aircraft configurations.
Implementation Method 1
a spherical bearing (54) allowing said relative oscillation by rolling on said spherical surface (55)
Implementation Method 2
a plurality of dampening elements (49) in contact with said spherical surface (55) radially externally to said spherical bearing (54), configured to dampen said oscillations by friction
Data Source
Figure 1
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AI summary
An articulated transmission joint (20; 20'; 20") for connecting a drive shaft (10) to a hub (15) of a rotor (8, 8', 8"), comprising: a first element (45, 45', 45") rotatable about a first axis (C); a second element (50, 51, 52; 50", 51'', 52'') rotatable about a second axis (D); and connecting means (60, 60', 60") to allow transmitting the motion between the first and the second element (45, 45', 45"; 50, 51, 52; 50", 51", 52") of a torque having a main component along the first axis (C) and a torque having a main component along the second axis (D); the connecting means (60, 60', 60") comprise, a roller (54) articulated on the first element (45, 45', 45''); and a chamber (53) defined at least partially by the second element (50, 51, 52; 50", 51", 52") and housing at least partially the roller (54); the chamber (53) is delimited towards the roller (54) by a first surface (59) that contacts the roller (54) circumferentially to the first axis (C), after the rotation of the first element (45) about the first axis (C); the first and second element (45, 45', 45"; 50, 51, 52; 50", 51", 52") are coupled so as to allow a tilt of an angle (α) between the first and second axis (C, D).