Elastomeric Double Hooke's Joint for Rotor 2P Vibration Reduction
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Solution Overview
Problem
Rotary-wing aircraft using a Hooke's joint as a rotor gimbal experience 2P vibration due to the lengthening and shortening of the gimbal during flapping, which existing configurations fail to adequately address.
Innovation Solution
A double Hooke's joint system is employed, comprising an upper and lower Hooke's joint with elastomeric journal bearings, allowing the hub plane to float vertically and eliminating axial load generation, thereby reducing vibration and weight while maintaining a compact design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single Hooke's joint is used as a rotor gimbal, then the structure is simple and compact, but 2P vibration occurs due to lengthening and shortening of the gimbal during flapping
Solution Approach 1:
The single Hooke's joint is divided into two separate Hooke's joints (upper and lower) that are coupled together. This segmentation allows each joint to handle specific rotational movements independently, preventing the lengthening and shortening that causes 2P vibration while maintaining overall structural compactness.
Solution Approach 2:
A spherical bearing is introduced as an intermediary component between the upper and lower Hooke's joints. This spherical bearing allows the upper Hooke's joint to float and move laterally along the mast, accommodating flapping motion without transmitting axial loads that would cause vibration.
2Stability of the object's composition
If traditional rigid bearings are used in the Hooke's joint, then structural stability is maintained, but axial load generation causes increased vibration and weight
Solution Approach 1:
The bearing type is changed from rigid to elastomeric, fundamentally altering the mechanical parameters of the joint. Elastomeric bearings provide flexibility that allows accommodation of flapping motion without generating axial loads, thereby reducing vibration while maintaining joint stability through elastic deformation.
Solution Approach 2:
Elastomeric materials are used in the bearings to combine the properties of flexibility and load-bearing capability. This composite material approach allows the bearing to deform elastically under load, absorbing flapping motions without transmitting harmful axial loads to the rotor system.
3Strength
If the hub plane is constrained vertically, then structural support is provided, but vibration increases due to axial load generation during flapping
Solution Approach 1:
The hub plane is given dynamic freedom to float vertically through the spherical bearing rather than being rigidly constrained. This dynamic capability allows the system to adapt to flapping motions in real-time, maintaining structural support while eliminating the axial loads that generate vibration during operational cycles.
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 double Hooke's joint system effectively reduces 2P vibration and weight, enabling a more efficient and compact rotor assembly that maintains constant angular velocity during rotation.
Implementation Method 1
a first set of bearings coupled to each arm on the second axis of the upper Hooke's joint and to each arm on the fourth axis of the lower Hooke's joint, wherein the first set of bearings comprise an elastomer
Implementation Method 2
elastomeric journal bearings
Implementation Method 3
an upper Hooke's joint having four arms extending radially outward to define first and second axes, the upper Hooke's joint adapted to be coupled to a rotor system yoke; a lower Hooke's joint having four arms extending radially outward to define third and fourth axes
Implementation Method 4
a spherical bearing configured to allow the upper Hooke's joint to move laterally along a mast
Data Source
AI summary
Embodiments are directed to a double Hooke's joint gimbal in a rotor system. An upper Hooke's joint has four arms extending radially outward to define first and second axes, and a lower Hooke's joint has four arms extending radially outward to define third and fourth axes. A pair of connectors couple the upper Hooke's joint and the lower Hooke's joint. A first set of bearings are positioned between arms on the upper and lower Hooke's joints and the connectors. The first set of bearings comprise an elastomer, such as elastomeric journal bearings. The upper Hooke's joint is coupled to a yoke and rotor blades by a driver assembly that allows rotor blade flapping. The lower Hooke's joint is coupled to and driven by a mast. A spherical bearing allows the upper Hooke's joint to move laterally along the mast.