Coaxial Bearing System for Torque Stability Across Temperature
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Solution Overview
Problem
Bearing systems in vertical shaft motor devices face challenges in maintaining operating torque within a predetermined range when operating at extreme temperature ranges due to differences in coefficients of thermal expansion between dissimilar materials used for the bearings, shaft, and frame.
Innovation Solution
A bearing system comprising a first deep groove Conrad bearing and a second angular contact bearing with a larger pitch diameter and lower axial stiffness, where the first inner ring and second inner ring are coaxial and secured together, and an axial preload force is applied to maintain operating torque within a range of zero to 50 foot-pounds from -40°C to 85°C.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If dissimilar materials are used for bearings, shaft, and frame to reduce weight, then weight is reduced, but operating torque varies outside acceptable range at extreme temperatures due to differential thermal expansion
Solution Approach 1:
The patent applies parameter changes by selecting specific bearing types (angular contact bearing and deep groove ball bearing) with particular pitch diameter ratios and axial stiffness characteristics. The axial preload force is carefully controlled to achieve an axial stiffness ratio between 0.3 and 0.7, which compensates for thermal expansion differences and maintains operating torque within the predetermined range across extreme temperatures from -40°C to 85°C.
Solution Approach 2:
The patent directly addresses thermal expansion by designing a bearing system where the differential thermal expansion between dissimilar materials (aluminum shaft/frame and steel bearings) is compensated through the specific configuration of bearings with different axial stiffnesses. The axial preload force creates a stiffness ratio that counteracts the thermal expansion effects, ensuring operating torque remains stable despite temperature variations causing different expansion rates in various materials.
2Reliability
If axial preload force is applied to adjust axial stiffness ratio, then operating torque is maintained within range, but device complexity increases
Solution Approach 1:
The patent merges two different bearing types (angular contact bearing and deep groove ball bearing) into a single integrated bearing system. This combination allows the system to achieve the desired axial stiffness ratio and compensate for thermal expansion effects without requiring additional complex components or adjustment mechanisms. The bearings work together synergistically to maintain operating torque consistency.
Solution Approach 2:
The patent applies dynamics by designing a bearing system where the axial stiffness ratio can adapt to temperature changes. The specific configuration of bearings with different axial stiffnesses, combined with the axial preload force, creates a dynamic system that automatically compensates for thermal expansion variations across the operating temperature range, maintaining operating torque within the predetermined range without active control.
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 bearing system effectively maintains operating torque within a predetermined range across the specified temperature range by adjusting the axial stiffness ratio through the application of a preload force, ensuring reliable operation in extreme temperature conditions.
Implementation Method 1
a first plurality of balls rollingly positioned between the first inner ring and the first outer ring. The first plurality of balls rollingly engage a first exterior raceway of the first inner ring and a first interior raceway of the first outer ring
Implementation Method 2
a second plurality of balls rollingly positioned between the second inner ring and the second outer ring. The second plurality of balls rollingly engage a second exterior raceway of the second inner ring and a second interior raceway of the second outer ring, wherein the second plurality of balls engage the counter bore at an angle offset from second axial centerlines
Implementation Method 3
The magnitude of the axial stiffness ratio is based on an axial preload force applied to the second outer ring such that an operating torque of the bearing system is within a predetermined range at temperatures from minus 40 degrees Celsius to positive 85 degrees Celsius
Implementation Method 4
The first ball bearing has a first pitch diameter and a first axial stiffness. The second ball bearing has a second pitch diameter and a second axial stiffness. The bearing system has an axial stiffness ratio defined by the first axial stiffness divided by the second axial stiffness
Data Source
AI summary
A bearing system for a rotating vertical shaft includes a first ball bearing, having a first pitch diameter and a first axial stiffness and a second ball bearing having a second pitch diameter and a second axial stiffness. The first ball bearing is a deep groove Conrad bearing. The second ball bearing is an angular contact bearing. The first and second ball bearings are coaxial, secured to one another and rotatable together. The first pitch diameter is at least 1.5 times greater than the second pitch diameter. The bearing system has an axial stiffness ratio defined by the first axial stiffness divided by the second axial stiffness. The axial stiffness ratio is based on an axial preload force applied to the second outer ring such that an operating torque of the bearing system is within a predetermined range at temperatures from minus 40 to positive 85 degrees Celsius.