Impeller Segmentation for Machining Access
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Solution Overview
Problem
The manufacturing of impellers for rotary machines, such as centrifugal compressors, faces challenges in processing time and cost due to interference from cylindrical and cover portions during machining, and the need to increase shrink fitting thickness for centrifugal force resistance, which can lead to increased costs and reduced shaft rigidity.
Innovation Solution
The impeller design features an inner peripheral side part formed in a cylindrical shape with an annular disc and blades on one side, allowing easy machining access and integration through external fitting of an outer peripheral side part, which includes an annular disc, blades, and a cover, enabling efficient molding and shrink fitting without the need for diffusion bonding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the impeller is integrally molded with conventional configuration, then manufacturing precision is improved, but processing time increases due to machining tool interference
Solution Approach 1:
The impeller is divided into two separate parts: an inner peripheral side part and an outer peripheral side part. These parts are manufactured separately and then integrated through shrink fitting, allowing easier machining of each component while maintaining overall integration precision.
Solution Approach 2:
The inner peripheral side part acts as an intermediary component that connects the rotating shaft to the outer peripheral side part. This intermediary structure facilitates easier machining access while ensuring precise integration through the shrink fitting process.
2Ease of manufacture
If the cylindrical portion is extended to improve machining access, then ease of manufacture is improved, but the shrink fitting place approaches the center of gravity requiring increased thickness
Solution Approach 1:
By segmenting the impeller into inner and outer peripheral side parts, the design achieves good machining access without needing to extend the cylindrical portion, thus avoiding the problem of increased thickness requirements near the center of gravity.
Solution Approach 2:
The solution moves the machining access improvement to a different dimensional approach by creating an insertion hole in the cover portion, allowing machining tools to access the flow path from the axial direction rather than requiring radial extension.
3Manufacturing precision
If diffusion bonding is used to connect inner and outer peripheral side parts, then manufacturing precision is improved, but manufacturing cost increases
Solution Approach 1:
The connection method is changed from diffusion bonding to shrink fitting, altering the manufacturing parameter from a high-temperature chemical process to a mechanical fitting process, thereby reducing manufacturing cost while maintaining sufficient connection precision.
Solution Approach 2:
The patent adopts a more economical connection method (shrink fitting) that is simpler and less costly than diffusion bonding, accepting that the connection is sufficient for the application without requiring the premium precision and cost of diffusion bonding.
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 design reduces manufacturing time and cost by facilitating easy access for machining tools, enhancing the structural integrity of the impeller, and maintaining the center of gravity while avoiding interference issues, thus improving the efficiency and cost-effectiveness of the manufacturing process.
Implementation Method 1
a portion on the other side in the axis line O direction on an inner peripheral surface of the cylindrical portion 82a of the disc 82 is integrally fixed to the rotating shaft by being shrink-fitted to the rotating shaft
Implementation Method 2
a manufacturing method of integrally molding the disc 82, the blades 83 and the cover 84 by performing a cutting process on an impeller material as a base material using a machining tool 90
Data Source
Figure 1
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Figure 4
AI summary
An impeller (10) is formed of two parts, i.e., an inner peripheral side part (20) and an outer peripheral side part (30). The inner peripheral side part (20) is molded in a cylindrical shape. The outer peripheral side part (30) is formed by integrally molding an annular disc (31) externally fitted to an outer peripheral surface (21) of the inner peripheral side part (20), a plurality of blades (40) provided at an interval in a circumferential direction on a surface that faces the other side in the axis line O direction of the annular disc (31) and forming al flow path extending in a radial direction, and a cover (50) covering the plurality of blades (40) from the other side in the axis line direction and having an insertion hole (53) to which the inner peripheral side part (20) is inserted in the axis line O direction at an interval in a radial direction.