CN105161249B - A kind of permanent magnetism solenoid - Google Patents

Abstract

A permanent solenoid solenoid, whose geometric structure has axial symmetry, consists of 2n+3 magnetic rings (1), n>2, a magnetically permeable shell (2) and a cylindrical magnetic field space (3). A magnetic field with axial symmetry is generated in the cylindrical space, and an axial magnetic field is mainly generated in the axial middle region of the magnetic field space (3). 2n+3 magnetic rings (1) are stacked in sequence along the axial direction, the inner cylindrical space of 2n+3 magnetic rings (1) is the magnetic field space (3), and the shell (2) is coaxially placed on 2n+3 magnetic rings ( 1) Perimeter. The main magnetic circuit of the present invention is composed of 2n+1 magnetic rings (1) in the middle, and the magnetic field intensity of the magnetic field space (3) is greatly improved by utilizing the axial magnetic field after the magnetic ring is decomposed and the radial magnetic field to superimpose each other; the main magnetic circuit The two ends adopt the end magnetic ring with the magnetic moment opposite to that of the n+2th magnetic ring, and at the same time, a magnetically permeable shell (2) is installed on the outer circumference of the 2n+3 magnetic rings (1), thereby reducing the magnetic flux leakage on the outer circumference of the magnet.

Description

A permanent solenoid magnet

technical field

The invention relates to a permanent magnet.

Background technique

Plasma is widely used in the fields of space, materials, microelectronics, environment and energy. Helicon wave discharge plasma is a kind of high-density plasma with high ionization rate. broad attention. A helicon wave is a wave with a whistling wave mode propagating in a finite-diameter, axially magnetized cylindrical plasma. A helicon wave plasma device usually uses one or more electromagnetic coils to provide an axially applied magnetic field. Electromagnetic coils not only require a huge DC power supply, but also have a large Joule heat loss, requiring peripheral cooling facilities. This makes the cost of the electromagnetic coil high, the energy consumption is large, and the volume (weight) is large, and it is not suitable for occasions with strict requirements on the external dimension, weight and maneuverability. With the improvement of the performance of permanent magnet materials and the vigorous development of industrial production, people are increasingly using permanent magnet materials to generate various spatially distributed magnetic fields. Chinese patent CN1862718B proposes a tubular permanent magnet with opposite poles, which produces a strong magnetic field whose polarity is constant along the circumferential direction; Chinese patent CN1866700B proposes a cylindrical permanent magnet system, which generates a sinusoidal wave cycle in a cylindrical space Radial air-gap magnetic field. The above-mentioned tubular or cylindrical permanent magnet adopts a plurality of permanent magnetic rings with axisymmetric magnetic moments in series, and the mutual superposition of the axial magnetic field and the radial magnetic field after the magnetic ring is decomposed makes the inner or outer magnetic ring The magnetic field strength in the cylindrical space is greatly improved, which effectively reduces the volume and weight of the magnet and improves the utilization rate of the permanent magnet material. However, there is still flux leakage in the non-effective magnetic field space of the above-mentioned magnetic circuit structure, especially at both ends of the axial direction. This not only reduces the magnetic field strength and uniformity of the effective magnetic field space, but also affects the Interference and influence of electromagnetic equipment.

Contents of the invention

In order to overcome the defects of the prior art, the present invention proposes a permanent solenoid magnet with low flux leakage.

The present invention is composed of 2n+3 magnetic rings and a magnetic shell, n>2; 2n+3 magnetic rings are stacked in sequence along the axial direction, and the shell is coaxially placed on the outer circumference of 2n+3 magnetic rings to form a hollow cylinder body. The inner cylindrical space of the cylinder is the magnetic field space. The geometry and magnetization direction of each magnetic ring have axisymmetrical. The No. 2 magnetic ring to the No. 2n+2 magnetic ring form the main magnetic circuit, and the magnetization direction changes counterclockwise from the No. 2 magnetic ring to the No. The magnetization directions differ by 360°/2n. The magnetization directions of the end magnetic rings, that is, No. 1 and No. 2n+3 magnetic rings, and the middle magnetic ring, that is, the No. n+2 magnetic ring, are both axial, and the magnetization directions of the end magnetic ring and the middle magnetic ring are opposite; The magnetization directions of the No. 2 magnetic ring and No. 2n+2 magnetic ring are both radial and opposite. The axial lengths of the end magnetic ring, No. 2 magnetic ring and No. 2n+2 magnetic ring are 1/2 of the axial lengths of the remaining magnetic rings. The two ends of the end magnetic ring and the outer peripheral surfaces of the remaining magnetic rings are magnetically permeable shells.

The main magnetic circuit of the present invention utilizes the mutual superposition of the axial magnetic field and the radial magnetic field after the magnetic ring is decomposed, so that the magnetic field intensity in the inner cylindrical space of the magnetic ring is greatly improved, and the magnetic flux leakage in the outer peripheral space of the magnetic ring is greatly reduced. The magnetization direction of the end magnetic block is opposite to that of the middle magnetic block, and the magnetic potential of the two end magnetic blocks is equal to that of the middle magnetic block, which improves the utilization rate of the permanent magnet while reducing the magnetic flux leakage at the end; the outer circumference of the magnetic ring In order to accommodate the magnetic lines of force around the outer circumference of the magnetic ring in order to accommodate the magnetically permeable housing, the magnetic flux leakage at the 5mm outer circumference of the housing is further reduced to below 100Gs.

The invention has the advantages of simple structure, light weight, small volume and no magnetic leakage around the periphery.

Description of drawings

Fig. 1 is the schematic diagram of the specific embodiment of the present invention, and among the figure 1 is magnetic ring, and 2 is shell, and 3 is magnetic field space, and oo ' is axis; Arrow represents the magnetization direction of magnetic ring;

Fig. 2 is the magnetic flux density vector distribution of the axial section of the embodiment of the present invention;

Fig. 3 is the magnetic field distribution on the axis of the embodiment of the invention;

Fig. 4 is the magnetic field distribution on the axial straight path of 5 mm from the outer surface of the magnet in the embodiment of the present invention;

Fig. 5 is the magnetic field distribution on a radial straight path 5mm away from the outer surface of the magnet according to the embodiment of the present invention.

detailed description

The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

Fig. 1 is the specific embodiment of the present invention.

As shown in Fig. 1, the present invention is made up of 9 magnetic rings 1, namely 2n+3=9 magnetic rings 1 and the shell 2 of magnetic permeability, n=3; Coaxially placed on the outer circumference of 9 magnetic rings to form a hollow cylinder. The inner space 3 of the cylinder is a magnetic field space. The geometric structure and magnetization direction of the 9 magnetic rings 1 are axisymmetric; the 2# magnetic ring to the 8# magnetic ring form the main magnetic circuit, and the magnetization direction changes counterclockwise from the 2# magnetic ring to the 8# magnetic ring . Viewed from any axial section, the magnetization directions of adjacent magnetic rings in the main magnetic circuit differ by 60°. The magnetization direction of the end magnetic ring is the 1# and 9# magnetic ring, and the middle magnetic ring is the 5# magnetic ring is along the axis oo', and the magnetization direction of the 1# and 9# magnetic ring is along the oo 'Downward, the magnetization direction of the 5# magnetic ring is along oo' upward; the magnetization directions of the 2# and 8# magnetic rings are both radial, and the magnetization direction of the 2# magnetic ring deviates from the axis oo', the 8th #The magnetization direction of the magnetic ring points to the axis oo'. The axial lengths of No. 1# and No. 9 magnetic rings, No. 2 and No. 8 magnetic rings are 1/2 of the axial lengths of the other five magnetic rings. The axial ends of the 1# and 9# magnetic rings and the outer peripheral surfaces of the remaining 7 magnetic rings are magnetically permeable shells 2 .

When the permanent magnet material is NdFeB, remanence B _r = 1.3T, relative magnetic permeability μ _r = 1.05, magnetic ring inner diameter 70mm, thickness 35mm, the 1# and 9# magnetic rings, the 2nd and the 8th The axial length of the No. 1 magnetic ring is 7.5mm, and when the axial length of the other 5 magnetic rings is 15mm, the overall size of the magnet is Ф155mm*130mm and the weight is 14kg.

Figure 2 shows the distribution of magnetic field vectors on its axial section, where the size of the arrow represents the size of the magnetic field. It can be seen that there is not only an axial magnetic field but also a radial magnetic field in the air gap. In the axial middle region of the air gap, the axial magnetic field is mainly; on the axis oo’, the axial magnetic field is basically. The magnetic field distribution on the axis is shown in Figure 3, where the abscissa 140mm corresponds to the axial center of the magnet. It can be seen that the axial magnetic field at the center of the air gap is 0.525T.

The magnetic field distributions on the typical axial and radial linear paths 5 mm away from the outer surface of the magnet are shown in Figure 4 and Figure 5, respectively, where the abscissa 70 mm in Figure 4 corresponds to the axial center of the magnet, and the abscissa 0 in Figure 5 corresponds to the magnet The center of the air gap, ie r=0, r∈[0,35mm] is the magnetic field space. It can be seen that, except for the two ends of the magnetic field space, the magnetic flux leakage at the 5mm circumference of the magnet is less than 100Gs.

Claims (1)

1. a kind of permanent magnetism solenoid, it is characterised in that：The geometry of the permanent magnetism solenoid has axial symmetry, by 2n Magnetic field space (3) composition of+3 magnet rings (1), the shell (2) of magnetic conductivity and cylinder；The permanent magnetism solenoid is in cylinder Space produces the magnetic field with axial symmetry, and mainly produces axial magnetic field in the axial intermediate region of magnetic field space (3)；2n+3 Individual magnet ring (1) is sequentially overlapped vertically, and the inner cylinder space of 2n+3 magnet ring (1) is magnetic field space (3), and shell (2) is coaxial It is placed in the periphery of 2n+3 magnet ring (1), n>2；

The geometry and the direction of magnetization of each magnet ring have axial symmetry；No. 2 magnet ring constitutes main magnetic to 2n+2 magnet rings Road, the direction of magnetization is from No. 2 magnet ring to 2n+2 magnet rings by change counterclockwise, in terms of any shaft section, the magnetic of adjacent magnet ring Change direction and differ 360 °/2n；It is No. 1 magnet ring and 2n+3 magnet rings to hold magnet ring, and middle magnetic ring is the magnetization of the n-th+No. 2 magnet rings Direction is axial direction, and the direction of magnetization of end magnet ring and middle magnetic ring is opposite；The direction of magnetization of No. 2 magnet ring and 2n+2 magnet rings Be radially and the direction of magnetization is opposite；

The axial length for holding magnet ring, No. 2 magnet ring and 2n+2 magnet rings is the 1/2 of remaining ring axial magnetic length.