Brushless Motor Four-Pole Rotor Vacuum Pump Magnetic Shielding
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Solution Overview
Problem
Existing vacuum pumps face challenges in achieving a compact design while minimizing magnetic interference, which is crucial for sensitive scientific and manufacturing equipment, as traditional motors with two-pole configurations generate stray magnetic fields due to rotor extensions for hall effect sensors.
Innovation Solution
A brushless motor with a four-pole permanent magnet rotor and non-overlapping stator coils, integrated with a sensor-less motor control system, is used to rotate the vacuum pumping mechanism at high speeds, utilizing a pump housing made of high electrical conductivity or magnetic permeability materials for eddy-current shielding, reducing stray magnetic fields.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a two-pole permanent magnet rotor with hall effect sensors is used, then the motor can be controlled, but stray magnetic fields leak out and interfere with sensitive equipment
Solution Approach 1:
The patent changes the pole configuration from two-pole to at least four-pole, which increases the commutation frequency. This parameter change transforms the motor control approach while simultaneously reducing magnetic interference through eddy-current shielding at higher frequencies
Solution Approach 2:
The patent converts the harmful stray magnetic fields into a beneficial shielding effect by using the high-frequency alternating magnetic field generated by the at least four-pole rotor to induce eddy currents in the conductive housing, which then shields the external environment from magnetic interference
2Difficulty of detecting and measuring
If the rotor extends axially beyond the stator for sensor measurement, then rotation sensing is enabled, but magnetic fields extend beyond the pump and increase interference
Solution Approach 1:
The patent replaces the mechanical/sensor-based rotation detection system (hall effect sensors requiring axial extension) with an electronic sensorless control system that determines rotor position through current sensing and computational algorithms, eliminating the need for axial rotor extension
Solution Approach 2:
The patent extracts and removes the hall effect sensors and their associated axial rotor extension from the motor design, eliminating the source of excessive magnetic field extension while maintaining rotation control capability through alternative means
3Adaptability or versatility
If different motor types are provided for Holweck and Siegbahn mechanisms, then each mechanism gets optimized motor, but manufacturing complexity and cost increase
Solution Approach 1:
The patent creates a universal motor design with at least four-pole configuration that can be adapted to drive different vacuum pumping mechanisms (Holweck, Siegbahn, Gaede) through variable speed control, eliminating the need for multiple specialized motor types while maintaining compatibility with various pump mechanisms
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 solution enables high-speed vacuum pumping with reduced magnetic interference, making the system suitable for sensitive equipment, while also allowing for a more compact design and reduced manufacturing costs by eliminating the need for multiple motor types.
Implementation Method 1
the housing of the vacuum pump is made of a material having a high electrical conductivity or a high magnetic permeability and said motor control means is configured to rotate said vacuum pumping mechanism at at least 20,000 revolutions per minute which together with said at least four poles causes a high commutation frequency for protecting the equipment by eddy-current shielding
Data Source
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AI summary
A vacuum pump 10 comprises a vacuum pumping mechanism 12 mounted for rotation by a shaft 14 and a brushless motor 16 for rotating the shaft. The vacuum pumping mechanism 12 comprises a turbo pumping mechanism 18 comprising a plurality of pumping stages, and a molecular drag pumping mechanism 20 comprising at least one pumping stage. Shaft 14 is supported for rotation by bearings 22. The motor 16 comprises a permanent magnet rotor 24 fixed relative to the shaft 14. The rotor 24 has four poles and a stator 26 has non-overlapping stator coils..