Vacuum Pump Imbalance Correction via Rounded Mass Removal
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Solution Overview
Problem
Existing vacuum pump imbalance correction methods, particularly mass removal techniques, face issues with stress concentration due to the use of sharp tools like drills, which can lead to instability and potential failure during operation, especially when handling corrosive gases or plasma environments.
Innovation Solution
The method involves cutting a portion of the axial end portion of the rotating cylindrical body to reduce its thickness, forming a removal portion with a large circumferential width and rounded corners, minimizing axial width and stress concentration, and using tools like end mills or routers for cutting to avoid sharp edges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If mass removal is performed using a drill with a sharply pointed tip, then imbalance correction can be achieved, but stress concentration occurs at the removal portion
Solution Approach 1:
The patent applies curvature by forming rounded corners at the removal portion instead of sharp edges. The removal portion is designed with a curved surface that transitions smoothly from the cylindrical body, eliminating stress concentration points. This is achieved by using a router or similar tool to create a rounded removal portion rather than a sharp-edged hole from drilling.
2Strength
If the rotating cylindrical body is cut to reduce thickness, then stress concentration is reduced, but the structural integrity may be compromised
Solution Approach 1:
The patent applies local quality by making the removal portion localized rather than reducing the overall thickness of the cylindrical body. The removal is confined to a specific axial end portion with controlled dimensions, while the rest of the body maintains its full thickness and structural integrity. The removal portion width and depth are carefully controlled to balance stress reduction with structural strength.
3Manufacturing precision
If mass adding means such as epoxy resin is used for imbalance correction, then imbalance can be corrected, but the mass adding means may fall off or disappear due to ozone or plasma
Solution Approach 1:
The patent extracts the problematic mass adding means (epoxy resin) and replaces it with a mass removal approach. Instead of adding material that can deteriorate in corrosive environments, the patent removes material from the cylindrical body to achieve imbalance correction. This eliminates the reliability issue of mass adding means falling off or disappearing while maintaining the imbalance correction function.
Data Source
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Figure 3(a)~3(d)
AI summary
Provided are a vacuum pump having a structure which reduces stress concentration in imbalance correction based on mass removal, a rotating portion included in the vacuum pump, and an imbalance correction method. At least a portion of a lower end portion (closer to an outlet port) of a rotating cylindrical body is cut in an axial direction thereof to form an imbalance correction portion (removal portion). Preferably, the removal portion is formed by cutting the lower end portion of the rotating cylindrical body so as to minimize an axial width of the rotating cylindrical body and set a circumferential width of the rotating cylindrical body to a value of not less than a thickness (width in a radial direction) of the rotating cylindrical body. Additionally, a corner formed in the removal portion is formed to have a large dimension (e.g., R3 or more). With this configuration, in the rotating cylindrical body, the removal portion is formed to have a shape in which a removal width (depth) in the axial direction of the rotating cylindrical body is small and a removal width in the circumferential direction thereof is large. This can reduce/lessen stress concentration after the imbalance correction in the vacuum pump.