Turbomachine Bearing Preloading via Threaded Slinger
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Solution Overview
Problem
Turbocharger bearing assemblies face issues during disassembly due to interference fits, leading to damage and high replacement costs, and preloading methods can cause axial slip and efficiency losses due to tensile forces on the shaft.
Innovation Solution
A lubricating fluid slinger with a screw thread is used to preload the bearing assembly, eliminating the need for compressor nut tightening and preventing axial slip by compressing the bearing assembly, allowing for a transition fit that facilitates easy disassembly without interference fits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If an interference fit is used to fix the inner race to the shaft, then the bearing assembly is securely fixed, but the shaft and bearing cartridge cannot be easily separated during disassembly, leading to damage
Solution Approach 1:
The invention divides the bearing assembly into separable components: the bearing cartridge (containing inner race, outer race, and bearing elements) and the shaft. The inner race is no longer interference-fit to the shaft but is instead held by the bearing cartridge structure, allowing the cartridge to be removed as a unit from the shaft during disassembly while maintaining secure operation during use.
Solution Approach 2:
The invention extracts the interference fit relationship between the inner race and shaft, eliminating the problematic direct interference fit. Instead, the inner race is supported by the bearing cartridge structure which can be independently removed, separating the securing function from the connection function.
2Reliability
If the compressor nut is tightened to preload the bearing elements, then the bearing assembly is properly preloaded, but a tensile axial force is applied to the shaft causing extension and axial slip
Solution Approach 1:
The invention introduces the bearing cartridge as an intermediary component between the inner race and the shaft. The cartridge structure (including the flange and positioning features) mediates the connection, allowing the inner race to be securely positioned and preloaded without directly transmitting tensile axial forces to the shaft that would cause extension and slip.
3Ease of repair
If the shaft is pulled through the bearing housing during disassembly, then the bearing assembly can be removed, but the interference fit causes the inner race to strip away from the bearing cartridge, resulting in damage
Solution Approach 1:
The invention segments the bearing assembly into a removable bearing cartridge unit that can be pulled from the shaft during disassembly without damaging the inner race. The cartridge structure is designed to maintain the integrity of the bearing elements during removal, allowing the entire cartridge to be extracted as one piece rather than causing the inner race to strip away.
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 lubricating fluid slinger effectively preloads the bearing assembly, reducing axial slip and enabling easy disassembly of the turbocharger shaft without damaging the bearing cartridge, thereby enhancing operational efficiency and reducing maintenance costs.
Implementation Method 1
a slinging formation arranged to propel a lubricating fluid away from the shaft as the shaft rotates
Implementation Method 2
the first lubricating fluid slinger comprising a screw thread that is engageable therewith such that the first lubricating fluid slinger is screwable along the threaded section of the shaft from a first position to a second position and wherein when the first lubricating fluid slinger is in the second position, it acts to compress the bearing assembly
Data Source
AI summary
A turbomachine with a shaft supporting a turbine wheel is supported for rotation in a housing. The shaft extends through a bore in the housing and a bearing assembly is disposed in the bore. The turbomachine has a first lubricating fluid slinger comprising a screw thread that is engageable with a threaded section of the shaft such that the first lubricating fluid slinger is screwable along the threaded section of the shaft so as to apply a compressive preload to the bearing assembly.