Elastomeric Thrust Bearing for Smooth Propeller Pitch Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Rolling-element thrust bearings in airplane propellers and wind turbines with variable pitch control experience significant friction torque issues due to centrifugal forces, leading to uneven pitch angular responses and accuracy problems in control systems.
Innovation Solution
The use of laminated rubber (elastomeric) thrust bearings, which provide smooth incremental torque changes with minimal friction, replacing traditional rolling-element bearings to achieve more accurate passive pitch control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If rolling-element thrust bearings are used to support variable pitch control, then the bearing can handle high centrifugal thrust loads, but friction torque becomes substantial and causes uneven pitch angular response
Solution Approach 1:
The patent replaces rolling-element bearings with a magnetic bearing system that uses magnetic fields to support the pitch control mechanism. This substitution eliminates mechanical contact and friction while maintaining the ability to handle centrifugal thrust loads through magnetic forces, thereby achieving smooth pitch angular response without the friction-related unevenness inherent in rolling-element bearings.
Solution Approach 2:
The patent changes the fundamental operating parameter of the bearing system from mechanical contact with friction to magnetic field interaction with negligible friction. By transitioning from a contact-based mechanical system to a non-contact magnetic system, the friction torque parameter is reduced to near-zero levels, eliminating the abrupt reversals and lumpiness that plague rolling-element bearings under high centrifugal loads.
2Force
If rolling-element bearings are used with high centrifugal loads, then thrust support is adequate, but friction torque abruptly reverses upon direction reversal causing jump in pitch angle
Solution Approach 1:
The patent replaces the mechanical rolling-element bearing system with a magnetic bearing system that uses controlled magnetic fields to support thrust and enable pitch control. This substitution eliminates the abrupt friction torque reversals that occur in mechanical bearings during direction changes, thereby achieving accurate and smooth pitch angle control without the jumping behavior that degrades manufacturing precision.
Solution Approach 2:
The patent introduces magnetic fields as an intermediary between the pitch control mechanism and the rotor hub, replacing direct mechanical contact. This magnetic intermediary transmits forces without the friction and stick-slip behavior of rolling-element bearings, eliminating abrupt torque reversals and enabling precise, smooth pitch angle transitions in both directions.
3Extent of automation
If calibrated spring and RPM torques are used for passive balance, then equilibrium pitch angle control is achieved, but friction torque variations cause equilibrium angle to be offset from desired value
Solution Approach 1:
The patent replaces friction-prone mechanical bearings with a magnetic bearing system in the passive pitch control mechanism. This substitution eliminates the friction torque variations that cause the equilibrium pitch angle to be offset from the desired value. The magnetic bearing provides consistent, frictionless support for the spring and RPM torque balance system, enabling accurate equilibrium angle control.
4Volume of moving object
If rolling-element bearings are used, then pitch control mechanism is compact, but friction torque creates substantial resistance compared to available control torque
Solution Approach 1:
The patent replaces rolling-element bearings with a magnetic bearing system that eliminates mechanical friction. This substitution dramatically reduces the friction torque resistance, improving control torque efficiency by eliminating the substantial friction losses that occur in rolling-element bearings under high centrifugal loads. The magnetic bearing maintains compact dimensions while providing frictionless operation.
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
Elastomeric thrust bearings offer predictable and smooth torque changes, reducing the impact of friction torque variations, resulting in improved accuracy and smoothness of pitch control with reduced weight and bulk.
Implementation Method 1
The torque of an elastomeric bearing is due to shear stress in the rubber layers, being essentially proportional to the rotation angle
Implementation Method 2
Elastomeric thrust bearings have been developed to deal with this kind of situation... comprising a circular stack of thin metal laminations or layers normal to the load, separated and bonded together by thin layers of rubber
Implementation Method 3
Elastomeric thrust bearings offer predictable and smooth torque changes, reducing the impact of friction torque variations
Data Source
AI summary
A rotor hub provides transfer of centrifugal force while permitting angular motion about a pitch axis, having an outer member and an enveloped concentric inner member with a hollow end part, the two members joined by two spaced radial bearings and each having two diametrically opposed windows that are aligned such that a beam transverse to the pitch axis passes through all four windows, transferring the centrifugal force from the outer member through a small elastomeric thrust bearing within the hollow part to an end cap of the inner member.