Vacuum Pump Rotor Inertia Moment Ratio Control
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Solution Overview
Problem
Turbo-molecular pumps in semiconductor manufacturing devices face rotor imbalance issues, leading to vibration and potential fatigue failure due to centrifugal forces and resonance, which complicates magnetic bearing support and gas exhaustion efficiency.
Innovation Solution
A vacuum pump design with a rotor and washer system where the inertia moment ratio γ (Jz/J) is adjusted by varying the washer thickness to control rotor deflection and vibration, ensuring γ > 1 to prevent resonance and reduce rotor deflection to less than 80 μm.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the rotor is rotated at high speed to achieve high vacuum state, then the gas exhaustion efficiency is improved, but the rotor vibration and deflection increase due to centrifugal force and resonance
Solution Approach 1:
The patent adjusts the inertia moment ratio γ (Jz/J) of the rotor as a key parameter to control vibration and deflection. By optimizing this parameter, the rotor's dynamic characteristics are improved, reducing resonance and deflection at high rotational speeds while maintaining gas exhaustion efficiency.
Solution Approach 2:
The patent adds a counterweight to the rotor to balance the centrifugal force caused by rotor imbalance. This counterweight offsets the unbalanced mass distribution, reducing vibration and deflection during high-speed rotation, thereby improving reliability without sacrificing productivity.
2Productivity
If the rotor is rotated at high speed to transfer gas efficiently, then the productivity is improved, but the magnetic bearing support becomes difficult due to increased vibration
Solution Approach 1:
The patent optimizes the rotor's inertia moment ratio γ to reduce vibration and deflection, making the rotor easier for the magnetic bearing to support at high speeds. This parameter adjustment simplifies the magnetic bearing control system while maintaining high gas transfer efficiency.
3Productivity
If the rotor blade repeatedly deflects due to resonance, then the gas exhaustion process continues, but fatigue failure occurs reducing the rotor lifespan
Solution Approach 1:
The patent adjusts the inertia moment ratio γ to avoid resonance conditions that cause repeated deflection and fatigue. By optimizing this parameter, the rotor blade operates smoothly without excessive vibration, extending its service life while maintaining continuous gas exhaustion capability.
Solution Approach 2:
The patent designs the rotor with optimized inertia characteristics beforehand to prevent resonance and excessive deflection before they can cause fatigue damage. This preventive design approach ensures the rotor blade can operate continuously without premature failure.
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
The design effectively reduces rotor vibration and deflection, enhancing magnetic bearing support and extending the lifespan of rotor blades by maintaining the inertia moment ratio above 1, thus preventing fatigue failure and improving gas exhaustion efficiency.
Implementation Method 1
a magnetic bearing which rotatably supports the rotating shaft
Implementation Method 2
a value of γ expressed in the following expression (1) is larger than 1... Jz is an inertia moment around an axis of the rotating shaft of the rotor, and J is the inertia moment around an axis orthogonal to the axis of the rotating shaft
Data Source
AI summary
A vacuum pump and a washer which can reduce vibration of a rotor and the rotor which can reduce the vibration are provided. When an inertia moment ratio which is a ratio between the inertia moment around a z-axis and the inertia moment around an x-axis or a y-axis is larger than 1, a natural frequency ω2 does not match a rotational frequency Ωz but goes away from that. When the natural frequency ω2 matches the rotational frequency Ωz, the rotor vibrates and thus, a fatigue failure occurs in a rotor blade. When the rotor is to be made larger in a radial direction of a rotating shaft, a value of the inertia moment ratio is set to a value larger than 1.