Scroll Device Lubrication via Idler Shaft Channels
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Solution Overview
Problem
Large scroll expander devices face issues with unpredictable and uneven lubrication, leading to bearing starvation and premature failure due to thermal expansion and incompatibility of grease with refrigerants, resulting in increased downtime and costs.
Innovation Solution
The implementation of a system that directs an oil/refrigerant mixture directly into the bearings through idler shaft assemblies with metering plugs to ensure consistent lubrication, combined with steel bearing sleeves to manage thermal expansion and prevent warping, and active oil lubrication for all internal bearings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If passive bearing lubrication using oil mist exiting the scroll is used, then the system is simple, but the lubrication is highly unpredictable, uneven, and dependent on expander speed and load
Solution Approach 1:
The lubrication system is segmented into multiple independent lubrication points, with separate oil delivery mechanisms for different bearing locations. Metering plugs are installed at specific locations to control oil flow to individual bearings, ensuring each bearing receives appropriate lubrication regardless of overall system conditions.
Solution Approach 2:
Metering plugs act as intermediary devices between the oil supply and the bearings. These plugs regulate and control the oil flow rate to each bearing, ensuring consistent and predictable lubrication delivery independent of expander speed and load variations.
2Duration of action of stationary object
If grease is used for lubrication, then lubrication retention is improved, but grease compatibility with refrigerants is poor and active cooling is not provided
Solution Approach 1:
The system uses the refrigerant-oil mixture already present in the expander to provide lubrication, eliminating the need for separate grease lubrication. The metering system ensures this self-service lubrication is delivered consistently to all bearings, providing both lubrication and cooling functions.
3Weight of moving object
If aluminum is used for scroll construction, then weight is reduced and heat transfer is improved, but thermal expansion causes bearing bores to increase in size non-uniformly
Solution Approach 1:
The system compensates for thermal expansion effects by designing bearing bores and sleeves that can accommodate dimensional changes. Steel bearing sleeves are used with clearance fits that maintain proper clearance despite aluminum thermal expansion, ensuring consistent bearing performance across temperature variations.
4Strength
If steel bearing sleeves are pressed into aluminum scroll components, then bearing retention is improved, but significant warping occurs causing premature scroll failure
Solution Approach 1:
Instead of pressing bearing sleeves into critical scroll areas, the system uses localized retention features such as bearing retainers or snap rings at specific locations. This approach provides strong bearing retention while avoiding the application of forming forces to the scroll body, preventing warping and maintaining scroll integrity.
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
This solution enhances bearing lubrication reliability, reduces downtime, and extends the lifespan of scroll devices by ensuring consistent lubricant flow and managing thermal expansion, thereby improving overall device performance and reducing maintenance costs.
Implementation Method 1
The implementation of a system that directs an oil/refrigerant mixture directly into the bearings through idler shaft assemblies with metering plugs to ensure consistent lubrication
Implementation Method 2
During high temperature operation, thermal expansion causes bearing bores to increase in size. The non-uniform thermal expansion may cause bearing outer races to spin within the bore.
Data Source
AI summary
A scroll device includes a fixed scroll with an idler shaft bearing, an orbiting scroll with another idler shaft bearing; and an eccentric idler shaft having first and second arms extending in opposite directions and ending at first and second ends, the first and second arms supported by the fixed scroll idler shaft bearing and the orbiting scroll idler shaft bearing, respectively. The eccentric idler shaft has a hollow core extending from the first end to the second end, with at least one channel extending through the first arm and enabling fluid communication between the hollow core and the at least one first bearing, and at least one second channel extending through the second arm and enabling fluid communication between the hollow core and the least one second bearing.