Vacuum Pump Cover Rigidity and Sealing Design
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Solution Overview
Problem
In turbo-molecular pumps, the tightening of bolts can cause gaps between the flexible cover and the rotor, leading to potential leakage and reduced sealing efficiency.
Innovation Solution
A vacuum pump design featuring a cover portion with a reinforcing periphery and a contact-pressure generating portion to prevent deflection and ensure a secure seal, even during high-speed rotation, by using a container-shaped cover with a cylindrical insertion portion and a disc portion, and a low-head cover-portion fixing bolt to maintain contact pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a thin disc-shaped flexible cover is used and fastened with a bolt, then the cover can be simple in structure and easy to manufacture, but the center part gets pressed and deflected by bolt tightening, creating gaps between the cover and rotor
Solution Approach 1:
The cover portion is designed with non-uniform thickness, featuring a thicker rim portion at the periphery and a thinner center portion. This local quality variation allows the rim to maintain rigidity and sealing contact while the center remains flexible, resolving the contradiction between ease of manufacture and sealing precision.
Solution Approach 2:
The cover portion is segmented into functionally distinct regions: a rim portion for structural support and sealing, and a center portion for flexibility. This segmentation allows each region to optimize its properties independently, maintaining sealing precision while keeping the overall structure simple to manufacture.
2Device complexity
If a thin disc-shaped flexible cover is used, then the cover can be simple in structure, but the cover becomes wavy microscopically after bolt tightening, generating gaps
Solution Approach 1:
By concentrating the thickness in the rim portion and reducing it in the center, the design achieves sufficient structural integrity and sealing reliability at the critical periphery while keeping the overall device complexity low through the simple thin-disc geometry.
Solution Approach 2:
The solution moves from considering only the two-dimensional thin disc shape to incorporating the third dimension of thickness variation. This dimensional change allows the rim to provide structural stability and sealing reliability while the center remains thin and simple.
3Reliability
If the cover is fastened tightly to prevent particle leakage, then sealing performance improves, but the cover deflects and creates gaps that reduce air-tightness
Solution Approach 1:
The non-uniform thickness distribution concentrates the sealing function in the thick rim portion that maintains stable contact with the rotor, while the thin center portion avoids deflection-induced gaps. This local quality differentiation resolves the contradiction between sealing performance and gap control.
Data Source
AI summary
A main-body casing having an inlet port or an outlet port, a rotatable rotor shaft, and a rotor coupled to the rotor shaft are provided. A recess portion opened toward the inlet port is formed in the rotor and a fastening portion (a first shaft portion and a second shaft portion) of the rotor shaft is exposed to the recess portion. A cover portion, which is fastened to the fastening portion by a cover-portion fixing bolt and covers at least a part of the recess portion, is formed having a container shape and has a reinforcing portion located in a periphery of the fastening portion that prevents deflection by increasing rigidity. The cover portion also has a contact-pressure generating portion which is pressed by fastening to the fastening portion in a fastening direction and causes a contact pressure to be generated in the fastening direction.