Keyless Impeller Shaft Coupling for Simpler Compressor Assembly
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Solution Overview
Problem
The existing impeller shaft coupling methods in vapor compression systems, which rely on keys, splines, or pins, are complex, costly, and time-consuming due to the need for precise machining and can interfere with the assembly process, leading to increased stress and reduced efficiency.
Innovation Solution
A method that couples an impeller to a shaft using a fastener with a nut and a tensioner to apply axial force, eliminating the need for keys, splines, or pins, thereby simplifying assembly and enhancing aerodynamics and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If keys, splines, or pins are used to couple the impeller to the shaft, then the impeller can be securely attached, but the manufacturing complexity and cost increase due to precise machining requirements
Solution Approach 1:
The patent removes keys, splines, and pins from the coupling mechanism, replacing them with a simplified interference fit between the impeller hub and shaft. This extraction of complex coupling elements eliminates the need for precise machining of keyways, splines, or pin holes, thereby reducing manufacturing complexity while maintaining secure attachment through the interference fit design.
Solution Approach 2:
Instead of using mechanical elements (keys, splines, pins) to transmit torque, the patent inverts the approach by using a press-fit interference coupling where the impeller hub is slightly larger than the shaft diameter. The secure attachment is achieved through friction and radial compression rather than through mechanical interlocking elements, simplifying the overall coupling mechanism.
2Strength
If keys, splines, or pins are used to couple the impeller to the shaft, then the impeller can be securely attached, but the assembly time increases due to difficult machining and assembly processes
Solution Approach 1:
By removing keys, splines, and pins from the design, the patent eliminates the time-consuming processes of machining keyways, aligning and inserting splines, or drilling and installing pins. The simplified interference fit allows for faster assembly where the impeller is simply pressed onto the shaft in a single operation, significantly reducing assembly time while maintaining coupling strength.
3Strength
If keys, splines, or pins are used to couple the impeller to the shaft, then the impeller can be securely attached, but the moment of inertia increases reducing compressor efficiency
Solution Approach 1:
The patent removes heavy mechanical coupling elements (keys, splines, pins) that contribute to the moment of inertia of the rotating assembly. By using a simpler interference fit without these additional components, the overall moment of inertia of the impeller-shaft assembly is reduced, thereby decreasing the energy required to accelerate and rotate the impeller, and improving compressor efficiency.
4Strength
If keys, splines, or pins are used to couple the impeller to the shaft, then the impeller can be securely attached, but manufacturing costs increase due to complex machining requirements
Solution Approach 1:
The patent eliminates the need for complex machining operations such as cutting keyways, machining spline grooves, or drilling precision holes for pins. The interference fit design requires only basic turning operations to create the slightly larger impeller hub diameter, significantly simplifying the manufacturing process, reducing tooling requirements, and lowering production costs while maintaining secure attachment.
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 approach reduces assembly time and costs, improves the compressor's efficiency by minimizing the moment of inertia, and lowers energy consumption by reducing the power required to rotate the impeller.
Implementation Method 1
the fastener is configured to stretch in an axial direction relative to the shaft via a tensioner during assembly of the compressor
Data Source
AI summary
A compressor for a heating, ventilating, air conditioning, and refrigeration (HVAC&R) unit includes an impeller, a shaft configured to rotate the impeller, and a fastener. The impeller includes an opening and does not include keys, splines, pins, or any combination thereof. The fastener is coupled to an end of the shaft and extends through the opening of the impeller, and the fastener is configured to stretch in an axial direction relative to the shaft via a tensioner during assembly of the compressor.