Elastomeric Centrifugal Force Bearing for Low-Friction Feathering
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing rotorcraft bearings oppose unnecessary torsional movement and fail to efficiently manage centrifugal forces when the rotorcraft is not in operation or when forces are minimal, leading to increased resistance and reduced lifespan.
Innovation Solution
The implementation of an elastomeric bearing assembly with a sliding cap and nonstick surface coatings, allowing for free rotation when centrifugal forces are below a threshold, reducing friction and enabling tailored, lightweight design by relaxing elastomeric components and preventing extended feathering torque and motion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If discrete bearings are used to manage centrifugal forces and feathering motions, then the rotorcraft can operate with controlled blade movement, but the bearings oppose unnecessary torsional movement even when centrifugal forces are minimal, leading to increased resistance and reduced lifespan
Solution Approach 1:
The bearing assembly transitions from a static constraint system to a dynamic one where the elastomeric bearing's stiffness changes with rotational speed. At low speeds, the bearing is compliant and allows free torsional movement; at high speeds, centrifugal force stiffens the bearing to provide necessary support, eliminating unnecessary resistance while maintaining reliability
Solution Approach 2:
The system exploits changes in the physical parameter of the elastomeric bearing's stiffness modulus with rotational speed. The bearing's effective stiffness increases with centrifugal force, transforming it from a flexible state at low speeds to a rigid state at high speeds, thereby adapting its mechanical properties to operational conditions
2Productivity
If traditional bearings are used that constrain all movement, then structural stability is maintained, but friction and stress increase unnecessarily when centrifugal forces are low, reducing efficiency
Solution Approach 1:
The bearing assembly dynamically adapts its constraint level based on operational state. During idle or low-speed operation, the elastomeric bearing remains compliant, allowing free blade feathering and minimizing frictional energy loss. During high-speed operation, centrifugal force activates the bearing's stiffness, providing necessary structural support only when required
Solution Approach 2:
The invention extracts the unnecessary constraint function from the bearing system during low-speed operation. By allowing the elastomeric bearing to remain compliant when centrifugal forces are minimal, the system removes unnecessary torsional resistance and energy-dissipating friction while maintaining structural integrity when needed
3Reliability
If elastomeric components are designed to handle maximum centrifugal forces, then reliability under load is ensured, but the bearing weight and complexity increase, and friction is not reduced when forces are minimal
Solution Approach 1:
The design leverages the speed-dependent stiffness parameter of elastomeric materials. The bearing is designed to be lightweight and simple in structure, relying on the physical property that elastomer stiffness increases with centrifugal force. This eliminates the need for complex active control mechanisms or heavy pre-loaded structures, achieving reliability through material physics rather than mechanical complexity
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 reduces resistance to torsional rotation, extends the lifespan of the bearing, and enables a more efficient and lightweight design by accommodating centrifugal forces effectively, allowing the rotorcraft to operate with reduced friction and stress.
Implementation Method 1
The sliding cap further comprises an exterior profile configured to complement a receiving profile of the housing so that, in response to a torsional force, rotation of the centrifugal force bearing about a center axis is allowed when the centrifugal force bearing is loaded with less than a threshold amount of centrifugal force
Implementation Method 2
Each bearing assembly can include an inboard beam mount configured to receive a centrifugal force bearing. The centrifugal force bearing can comprise a bearing stack of alternating rigid shims and flexible elastomeric members
Implementation Method 3
The sliding cap further comprises an exterior profile configured to complement a receiving profile of the housing so that, in response to a torsional force, rotation of the centrifugal force bearing about a center axis is allowed
Data Source
AI summary
An elastomeric bearing assembly has a housing, a centrifugal force bearing axially captured relative to the housing, and a sliding cap disposed between the housing and the centrifugal force bearing.