Composite X-ray Tube Bearing Thermal Expansion Compensation
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Solution Overview
Problem
Rotating anode x-ray tubes face issues with thermal expansion differences between outer and inner bearing races, leading to increased noise and reduced bearing life due to the need for significant internal radial clearance and costly high-temperature materials for cooling.
Innovation Solution
A composite outer bearing with rings made from high hot-hardness materials and a spacer with a lower coefficient of thermal expansion, allowing for thermal and mechanical compensation of growth rates to minimize end-play variations, eliminating the need for separate cooling arrangements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If high-temperature hardened materials are used for the outer bearing, then bearing life is extended, but manufacturing cost increases
Solution Approach 1:
The outer bearing is constructed as a composite structure with an inner hub made of high-temperature hardened material (such as Inconel or Hastelloy) and an outer race made of standard hardened material. This composite design allows the expensive high-temperature material to be used only where thermally critical (the inner hub exposed to x-ray tube heat), while the outer bearing race can use less expensive materials, thereby reducing overall manufacturing cost while maintaining bearing life
Solution Approach 2:
The patent applies different material qualities to different regions of the bearing. The inner hub receives high-temperature hardened material treatment to resist thermal degradation, while the outer race uses standard hardened material. This localized application of high-temperature materials optimizes cost by avoiding unnecessary use of expensive materials in regions not exposed to extreme temperatures
2Temperature
If large internal radial clearance is built into the bearing to accommodate thermal expansion, then thermal expansion is accommodated, but bearing noise increases and bearing life is reduced
Solution Approach 1:
The patent changes the thermal expansion parameters by using materials with matched or complementary coefficients of thermal expansion for the inner hub and outer race. This allows the bearing to accommodate thermal expansion through controlled dimensional changes rather than requiring excessive radial clearance, thereby maintaining proper bearing clearance and avoiding the noise and premature failure associated with oversized clearances
3Duration of action of stationary object
If high-temperature hardened materials are used for the outer bearing, then bearing life is extended, but device complexity increases
Solution Approach 1:
The bearing is designed as a composite structure integrating the inner hub and outer race with different material properties. This composite design, while using multiple materials, creates a unified bearing assembly that maintains structural simplicity and ease of installation, avoiding the need for complex cooling arrangements or multiple separate components
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 effectively reduces bearing noise and extends bearing life by optimizing thermal expansion compensation, potentially lowering costs and improving fatigue life through reduced vibration levels.
Implementation Method 1
a spacer positioned between the one ring and the other ring, the one outer race opposing the inner race on the shaft and the other outer race opposing the inner race on the inner ring; the one ring and the other ring made from high hot-hardness material; the spacer made from a constant coefficient of thermal expansion material
Data Source
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AI summary
The rotating anode x-ray tube has a composite outer bearing made from two rings of a high hot-hardness material and a spacer between the two rings made of a constant coefficient of thermal expansion material. The spacer is welded to the two rings providing the composite outer bearing. One inner bearing race is formed from the shaft and the other inner bearing race is a one-piece inner race mounted on the shaft while the two rings have the corresponding outer races.