Multi-Stage Vacuum Pump Rotor Structure for Modal Frequency Control
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Solution Overview
Problem
Existing multi-stage vacuum pumps face challenges with modal frequency of the rotor to cause difficulties, and the diameter of the shaft extending between adjacent rotary vanes may cause the rotor to cause mechanical issues with the rotor to cause mechanical issues with the rotor to cause mechanical issues with the rotor to cause mechanical issues with the rotor to cause mechanical issues with the rotor to cause mechanical issues with the rotor to cause mechanical issues with the rotor to cause mechanical issues with the rotor to cause mechanical issues with the rotor to cause mechanical deflection of the rotor during operation.
Innovation Solution
The rotor is provided with a pair of end shafts and an inter-vane shaft with a larger diameter than the end shafts, and shims or inserts are used to modify the modal frequency by fitting onto an internal shaft between the rotary vanes, enhancing the rotor's stiffness and modal frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the shaft diameter between adjacent rotary vanes is increased to reduce mechanical deflection, then the rotor stiffness is improved, but the device complexity increases due to the need for shims or inserts
Solution Approach 1:
The shaft is segmented into different diameter sections: a first shaft section with a first diameter connecting to the rotary vanes, and a second shaft section with a second (larger) diameter between adjacent rotary vanes. This segmentation allows the shaft to have localized increased stiffness where needed without uniformly increasing the entire shaft diameter, thus reducing mechanical deflection while maintaining reasonable overall complexity.
Solution Approach 2:
The shaft exhibits local quality variation with different diameters in different sections. The second shaft section has a larger diameter specifically positioned between adjacent rotary vanes to provide localized increased stiffness and reduce mechanical deflection in the critical region, while the first shaft section maintains a smaller diameter to minimize overall device complexity and weight.
2Reliability
If the shaft diameter between adjacent rotary vanes is increased to change the modal frequency, then the operational stability is improved, but the manufacturing complexity increases
Solution Approach 1:
The shaft is divided into segments with different diameters, allowing the modal frequency to be adjusted by modifying only the second shaft section between the rotary vanes. This segmented approach enables targeted frequency adjustment without requiring complete shaft redesign, improving operational stability while managing manufacturing complexity.
Solution Approach 2:
Shims or inserts are introduced as intermediary elements within the second shaft section to achieve the desired larger diameter and modal frequency adjustment. These intermediaries are fitted into a cavity or bore in the shaft, providing the necessary stiffness and frequency characteristics without requiring the entire shaft to be manufactured as a single complex piece with varying diameters.
3Strength
If a larger diameter inter-vane shaft is used to reduce mechanical deflection, then the rotor performance is improved, but the weight of the rotor increases
Solution Approach 1:
The shaft is segmented such that only the second shaft section between adjacent rotary vanes has the larger diameter needed for reduced mechanical deflection. The first shaft section connecting to the rotary vanes maintains a smaller diameter, thereby reducing the overall weight increase while still achieving the performance benefit in the critical region where deflection occurs.
Solution Approach 2:
The shaft has local quality variation with a larger diameter specifically where needed between the rotary vanes to resist mechanical deflection. This localized reinforcement minimizes the overall weight increase compared to uniformly increasing the entire shaft diameter, as the larger diameter is applied only in the critical region rather than throughout the entire shaft length.
Data Source
Figure 1A~1B
Figure 2~4
Figure 5~7
AI summary
A rotor for a multi-stage vacuum pump, a multi-stage vacuum pump and a method are disclosed. The rotor comprises: a plurality of rotary vanes, the plurality of rotary vanes being axially displaced and coaxially aligned; a pair of end shafts, each end shaft extending from opposing axial ends of the plurality of rotary vanes; and an inter-vane shaft extending between adjacent rotary vanes of the plurality of rotary vanes, the inter-vane shaft having a diameter which is greater than that of the end shafts. In this way, the inter-vane shaft provided between each rotary vane may have an increased diameter, which improves the stiffness of the shaft and changes the modal frequency of the rotor. Such a change in the modal frequency is typically sufficient to improve its operation.