Molecular Vacuum Pump Rotor Speed Variation
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Solution Overview
Problem
Vacuum pumps operated at fixed speeds experience significant vibration excitation due to natural frequency resonance, leading to increased costs and reduced vacuum performance, as well as heat-related issues from electrical and mechanical losses.
Innovation Solution
Variation of the rotor speed between two values periodically, with temporary cessation of motor coil current supply to reduce vibration and heat generation, while maintaining compatible vacuum data through careful control of the variation phase.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the vacuum pump is operated at a fixed speed, then the vacuum data (final pressure and pumping speed) remain stable, but natural frequencies of the chamber are strongly excited causing significant vibrations
Solution Approach 1:
The rotor speed is periodically varied between a first speed value and a second speed value in a variation phase, creating a modulated operation pattern that reduces continuous resonance excitation while maintaining average vacuum performance
2Object-affected harmful factors
If additional components are installed between the vacuum pump and chamber to reduce vibrations, then vibration excitation is reduced, but additional costs and deterioration in vacuum data occur
Solution Approach 1:
The vacuum pump system uses its own rotor speed modulation capability to reduce vibrations, eliminating the need for additional external vibration reduction components and their associated costs and conductance losses
3Object-affected harmful factors
If the rotor speed is varied periodically between two speed values, then vibration excitation is significantly reduced, but the complexity of speed control increases
Solution Approach 1:
The control device modulates the rotor speed parameter between two discrete values, using parameter variation to achieve vibration reduction while maintaining manageable control complexity through defined speed states
4Temperature
If electrical and mechanical losses are reduced by varying the drive power, then heat generation is reduced improving temperature balance, but the pumping performance may fluctuate
Solution Approach 1:
The drive power is periodically reduced during the variation phase when the rotor speed is modulated, creating intermittent cooling periods that improve temperature balance while the periodic nature maintains average pumping performance
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
Significantly reduces vibration excitation and heat generation, improving the temperature balance and vacuum performance with minimal disruption to the evacuation process.
Implementation Method 1
A motor coil (14) on the stator side interacts with a motor magnet (27) arranged on the shaft
Implementation Method 2
The gas is drawn in through the opening provided in the pump flange, compressed in the vacuum pump and passed through the pump outlet
Implementation Method 3
Due to electrical and mechanical losses, various parts of the pump system and the drive unit heat up
Data Source
Figure 1
Figure 2
AI summary
The method involves rotating a rotor (8) of a molecular vacuum pump (1) with a number of revolutions by a drive (13), where the number of revolutions of the rotor is periodically varied between two speed values in a variation phase. Power for acceleration of the rotor is limited at a value in the variation phase, where the value is reduced with respect to maximum power. A measuring device (25) is arranged at a measuring flange (24) of a chamber (2) for measuring pressure in the chamber in the variation phase, where a pump flange (4) is connected with a chamber flange (3). An independent claim is also included for a molecular vacuum pump comprising a rotor.