Monolithic Permanent Magnet with Segmented Axial Sections
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Solution Overview
Problem
Monolithic permanent magnets generate stray magnetic fields that can interfere with sensitive applications, such as electron microscopes and vacuum pumps, leading to imaging errors and magnetization issues in thin films.
Innovation Solution
A monolithic permanent magnet design with varying axial dimensions and magnetizations between sections, where end sections have reduced dimensions and magnetization compared to adjacent sections, reducing the stray magnetic field effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a monolithic permanent magnet is used, then the magnetic bearing function is achieved, but a stray magnetic field is generated that interferes with sensitive applications
Solution Approach 1:
The permanent magnet is divided into multiple magnetized sections along the axial direction, with each section having alternating magnetization directions. This segmentation allows the stray magnetic fields from individual sections to partially cancel each other, reducing the overall stray magnetic field while maintaining the magnetic bearing function.
Solution Approach 2:
Different sections of the permanent magnet are given different axial dimensions and/or magnetization strengths. The end sections have reduced axial dimensions and/or reduced magnetization compared to the middle sections, creating local variations that reduce the stray magnetic field at the ends where it is most problematic.
2Object-generated harmful factors
If the axial dimension of end sections is reduced, then the stray magnetic field is minimized, but the magnetic strength may be compromised
Solution Approach 1:
The magnet is segmented into multiple sections with alternating magnetization directions. The middle sections maintain full axial dimensions and strong magnetization to provide sufficient magnetic strength, while the end sections are reduced to minimize stray fields. The alternating polarity arrangement ensures that the reduced end sections do not significantly compromise the overall magnetic bearing function.
Solution Approach 2:
The permanent magnet exhibits non-uniform properties along its axial length, with end sections having different axial dimensions and/or magnetization strengths compared to middle sections. This local differentiation optimizes the balance between reducing stray magnetic fields at the ends and maintaining sufficient magnetic strength in the center for bearing operation.
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 significantly minimizes stray magnetic fields, enabling the use of these magnets in sensitive applications like vacuum pumps and audio amplifiers by reducing magnetic interference.
Implementation Method 1
a monolithic permanent magnet (14), in particular for a permanent magnet bearing (10), with a longitudinal axis (L) and with a plurality of sections (16) arranged along this and at least approximately axially magnetized, the magnetizations of which are aligned in alternating opposite directions to one another
Implementation Method 2
The stray magnetic field can affect highly sensitive applications, e.g. by deflecting an electron beam of an electron microscope as a result of the Lorentz force
Data Source
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AI summary
The invention relates to a monolithic permanent magnet, in particular for a permanent magnet bearing of a vacuum pump, with a longitudinal axis and several sections arranged along this axis and magnetized at least approximately axially, the magnetizations of which are alternately oriented in opposite directions to each other, characterized in that the axial dimension and/or the magnetization of at least one magnetized section and the axial dimension and/or the magnetization of at least one other magnetized section differ.