Vacuum Pump Rotor Sleeve Decouples Magnet Rings
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Solution Overview
Problem
Higher rotor speeds in turbomolecular pumps lead to mechanical stresses in permanent magnet rings due to centrifugal forces, causing potential cracking or breakage, and existing solutions like one-piece rotors or complex welding are not effective in managing these stresses.
Innovation Solution
A vacuum pump design featuring a sleeve surrounding the rotor-side permanent magnet bearing, made of a material with a lower coefficient of thermal expansion and higher modulus of elasticity than the rotor components, which decouples the magnet rings from the rotor components, preventing radial expansion and thus reducing mechanical stresses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If rotor speed is increased to improve pumping performance, then productivity increases, but mechanical stresses in permanent magnet rings increase causing cracking or breakage
Solution Approach 1:
The rotor structure is segmented into distinct components: the rotor shaft, rotor disks, and a separate decoupling element. This segmentation allows the permanent magnet rings to be isolated from the rotating rotor components, preventing stress transmission while maintaining rotational integrity for high-speed operation
Solution Approach 2:
A decoupling element is introduced as an intermediary component between the rotor components and the permanent magnet rings. This mediator prevents direct mechanical coupling, allowing the rotor to rotate at high speeds while the permanent magnet rings remain stationary and stress-free
2Ease of manufacture
If press fit is used to secure permanent magnet rings and rotor disks, then ease of manufacture improves, but mechanical stresses increase at higher rotor speeds
Solution Approach 1:
The permanent magnet rings are extracted from the rotating assembly and placed in a stationary decoupled position. This removes them from the high-stress press fit environment while maintaining the ease of assembly through simple radial placement into the decoupling element
3Reliability
If one-piece rotor design is used to eliminate stresses between rotor shaft and disks, then reliability improves, but manufacturing complexity and cost increase
Solution Approach 1:
Rather than creating a complex one-piece rotor, the invention segments the rotor into standard components (shaft, disks, bearing halves) and introduces a decoupling element. This maintains manufacturing simplicity while achieving the stress elimination goal through modular assembly
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 allows for significant increase in rotor speed without adverse mechanical stresses in the permanent magnet rings, preventing cracking or breakage, and ensures reliable operation even at higher speeds.
Implementation Method 1
a permanent magnet bearing supporting the rotor shaft on the intake side, which has a stator-side bearing half and a rotor-side bearing half arranged radially outside the stator-side bearing half, each comprising several axially successive permanent magnet rings
Implementation Method 2
the correspondingly higher centrifugal forces that occur at higher rotor speeds also impair the press fit between the rotor shaft and the rotor disks pressed onto it
Data Source
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AI summary
A vacuum pump (66), in particular a turbomolecular pump, comprises a stator and a rotor (68) with a rotor shaft (72) rotatably mounted about a rotor axis (70) and several rotor disks (76) provided on the rotor shaft, each comprising several rotor blades (74), as well as a permanent magnet bearing (78) supporting the rotor shaft on the intake side, which has a stator-side bearing half and a rotor-side bearing half (80) arranged radially outside the stator-side bearing half, each comprising several axially successive permanent magnet rings (80'). The rotor-side bearing half (80) of the permanent magnet bearing is enclosed by a sleeve (82) surrounding it circumferentially, which radially decouples the permanent magnet rings (80') of the rotor-side bearing half (80) of the permanent magnet bearing from the surrounding rotor components (72, 76).