Compressor Shaft Venting to Manage Variable-Speed Lubricant Oversupply
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Solution Overview
Problem
Variable-speed compressors face challenges in managing lubricant supply, as fixed-displacement pumps often oversupply lubricant at higher speeds, leading to excess lubricant accumulation.
Innovation Solution
Incorporating a vent through the shaft of the compressor, which allows excess lubricant to be directly returned to the sump, primarily when other surfaces are sufficiently lubricated, thereby preventing oversupply and ensuring efficient lubrication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fixed-displacement lubricant pump is used in a variable-speed compressor, then the pump structure is simple and reliable, but the lubricant supply becomes excessive at higher speeds leading to lubricant accumulation
Solution Approach 1:
The patent extracts the excess lubricant from the main lubrication circuit by providing a dedicated vent passage through the shaft. This vent passage allows the separation and removal of surplus lubricant that cannot be utilized by the bearing surfaces, preventing lubricant accumulation while maintaining the simplicity of the fixed-displacement pump.
Solution Approach 2:
The patent creates different functional zones within the shaft structure. The shaft includes both a lubricant supply channel for delivering lubricant to bearing surfaces and a vent passage for removing excess lubricant. This local differentiation allows the system to handle both lubricant delivery and excess removal functions within the same component.
2Reliability
If lubricant is supplied continuously to all surfaces, then all surfaces are adequately lubricated, but excess lubricant accumulates and cannot be returned to the sump
Solution Approach 1:
The patent converts the harmful effect of excess lubricant accumulation into a beneficial feature by designing the vent passage to utilize centrifugal force. The excess lubricant, which would otherwise be wasted, is channeled through the rotating shaft where centrifugal force naturally directs it toward the vent passage, enabling automatic excess removal without additional energy consumption.
Solution Approach 2:
The shaft structure serves itself by incorporating the vent passage that automatically removes excess lubricant through centrifugal action during rotation. The system self-regulates the lubricant quantity without requiring external control mechanisms, as the rotating shaft inherently creates the conditions for excess lubricant to be directed to the vent and returned to the sump.
3Quantity of substance
If the vent is positioned to remove excess lubricant efficiently, then lubricant oversupply is prevented, but the vent may interfere with other compressor components
Solution Approach 1:
The patent nests the vent passage within the shaft structure itself, utilizing the hollow interior of the rotating shaft. The lubricant supply channel and vent passage are arranged concentrically within the shaft, with the vent passage positioned to receive excess lubricant from the supply channel and discharge it through the shaft wall. This nested arrangement eliminates the need for separate external venting components.
Solution Approach 2:
The patent transitions the vent discharge from a radial direction to an axial direction by positioning the vent passage to discharge lubricant along the length of the shaft toward the sump. This dimensional change in the discharge direction allows the vent to clear excess lubricant away from the rotor-stator assembly area, preventing interference with compression components while maintaining efficient excess lubricant removal.
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 venting system effectively manages lubricant supply, ensuring appropriate lubrication at all speeds by returning excess lubricant to the sump, thus enhancing compressor efficiency and reducing wear on components.
Implementation Method 1
The vent can be provided within the crankshaft, for example at the center thereof, such that the vent receives lubricant after other surfaces due to centrifugal force within the compressor.
Implementation Method 2
a lubricant pump, and a lubricant channel configured to convey lubricant from the lubricant pump to a distal end of the shaft
Implementation Method 3
The vent can be provided in a position below the rotor-stator assembly, such that the lubricant does not become entrained with the gas in the compressor.
Data Source
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AI summary
A compressor (200) includes a lubricant pump (226) and a shaft (208) having a lubricant vent (218) extending through the shaft. The vent has an outlet (220), which can be provided below a stator-rotor assembly (210, 222) of a motor of the compressor. The shaft can be used in a variable speed compressor to convey excess lubricant when the pump is over-supplying lubricant due to operation at speeds greater than the minimum speed. The vent (218) can be positioned at a center of the shaft. The outlet (220) of the vent can direct gas and/or lubricant onto windings of the stator (222) so as to provide cooling.