A permanent magnet system with a large range and high uniformity magnetic field

Abstract

The present invention discloses a permanent magnet system with a large-range high-uniformity magnetic field, comprising a magnetic yoke and magnetic poles arranged at the upper and lower positions of the magnetic yoke, the magnetic poles comprising magnetic steel and pole shoes, the magnetic steel being arranged at the relative positions of two magnetic yokes, and the pole shoes being arranged on the magnetic steel; the side of the pole shoe in contact with the magnetic steel adopts a curved surface structure, and is embedded into the interior of the magnetic steel through the curved surface structure; the side of the pole shoe away from the contact with the magnetic steel adopts a planar structure, thereby forming a flat air gap between the two relative pole shoes. The beneficial effects of the present invention are: 1) The magnetic pole structure has a simple shape, low processing cost, and the magnetization direction of the magnetic steel is consistent, and there is no need to splice multiple magnetic steels with different magnetization directions. 2) The pole surface of the magnetic pole can be made into a plane. Compared with the pole shoes with complex design shapes, the average length of the air gap between the magnetic poles of the present invention can be reduced, which is conducive to increasing the magnetic field strength and reducing the cost.

Description

Technical Field

[0001] The invention relates to the technical field of permanent magnet systems, and in particular to a permanent magnet system with a large-range and high-uniformity magnetic field. Background Art

[0002] Permanent magnet systems are widely used and can play an important role in nuclear magnetic resonance imaging devices, atomic absorption spectrophotometers, electromagnetic pumps and other similar devices.

[0003] The Chinese patent number is: 85103498, and the name is: Permanent magnet with high uniformity magnetic field and the Chinese patent number is: 94115507.2, and the name is: Large air gap C-type permanent magnet. The structural characteristics of these two patents are that there are many magnetic steels in the magnetic pole, and these magnetic steels have different magnetization directions and different sizes. Since the magnetic steels are assembled after saturation magnetization, the mutual repulsion between the magnetic steels during the assembly process is very large, and complex installation tools are required to ensure the accuracy of the installation and the safety of the installation process.

[0004] The Chinese patent number is 200610114716.X, and its name is a permanent magnet for fully open magnetic resonance imaging. The structural characteristics of this patent are that the shape of the magnetic steel is relatively simple, but the shape of the pole shoe is complex, which is difficult to process and requires precise design and calculation. Summary of the invention

[0005] In order to solve the problems existing in the prior art, the present invention provides a permanent magnet system with a large range and high uniformity magnetic field and a reasonable structural design.

[0006] The technical solution of the present invention is as follows:

[0007] A permanent magnet system with a large-range, highly uniform magnetic field, characterized in that it comprises a yoke and magnetic poles arranged at upper and lower positions of the yoke, the magnetic poles comprising magnetic steel and pole shoes, the magnetic steel being arranged at relative positions of two yokes, and the pole shoes being arranged on the magnetic steel; the side of the pole shoe in contact with the magnetic steel adopts a curved surface structure, and is embedded in the interior of the magnetic steel through the curved surface structure; the side of the pole shoe away from the contact with the magnetic steel adopts a planar structure, thereby forming a uniform air gap between the two opposite pole shoes.

[0008] The permanent magnet system with a large-range and highly uniform magnetic field is characterized in that the magnetizing directions of the magnetic poles at the upper and lower positions of the magnetic yoke are consistent.

[0009] The permanent magnet system with a large-range and highly uniform magnetic field is characterized in that the planar structure of the pole shoe is higher or lower than the bottom surface of the magnetic steel, or is flush with the bottom surface of the magnetic steel.

[0010] The permanent magnet system with a large-range and highly uniform magnetic field is characterized in that the yoke adopts a mouth-shaped structure, the magnetic pole adopts a cylindrical structure, and the pole shoe adopts an ellipsoidal cross-section structure.

[0011] The permanent magnet system with a large-range and highly uniform magnetic field is characterized in that the magnetic yoke adopts a C-shaped structure, the magnetic pole adopts a rectangular parallelepiped structure, and the pole shoe adopts a structure in which two ellipsoids intersect.

[0012] The permanent magnet system with a large-range and highly uniform magnetic field is characterized in that the magnetic yoke adopts a C-shaped structure, the magnetic pole adopts a rectangular parallelepiped structure, and the pole shoe adopts a structure formed by merging two ellipsoids.

[0013] The permanent magnet system with a large range and high uniformity magnetic field is characterized in that the maximum outer diameter of the pole shoe is smaller than the outer diameter of the magnetic steel, and the outer diameter of the pole shoe is greater than 0.4 times the outer diameter of the magnetic steel and less than 0.9 times the outer diameter of the magnetic steel, the thickness of the magnetic steel is greater than the thickness of the pole shoe, and the width of the air gap between the pole shoes is greater than 0 and less than 3 times the thickness of the pole shoe.

[0014] The permanent magnet system with a large range and high uniformity magnetic field is characterized in that the length and width of the pole shoe are respectively smaller than the length and width of the magnetic steel, the length of the pole shoe is greater than 0.4 times the length of the magnetic steel and less than 0.9 times the length of the magnetic steel, the width of the pole shoe is greater than 0.4 times the width of the magnetic steel and less than 0.9 times the width of the magnetic steel, the thickness of the magnetic steel is greater than the thickness of the pole shoe in the length and width directions, and the width of the air gap between the pole shoes is greater than 0 and less than 3 times the length and thickness of the pole shoe in the width direction.

[0015] The permanent magnet system with a large range and high uniformity magnetic field is characterized in that the length and width of the pole shoe are respectively smaller than the length and width of the magnetic steel, the length of the pole shoe is greater than 0.4 times the length of the magnetic steel and less than 0.9 times the length of the magnetic steel, the width of the pole shoe is greater than 0.4 times the width of the magnetic steel and less than 0.9 times the width of the magnetic steel, the thickness of the magnetic steel is greater than the thickness of the pole shoe in the length and width directions, and the width of the air gap between the pole shoes is greater than 0 and less than 3 times the length and thickness of the pole shoe in the width direction.

[0016] The permanent magnet system with a large range and high uniformity magnetic field is characterized in that the material of the yoke is 416 stainless steel, 1010 stainless steel or Q235 steel, the material of the magnetic steel is sintered ferrite, sintered SmCo or NdFeB, and the material of the pole shoe is electrical pure iron DT4, 1J22 or hiperco50.

[0017] The beneficial effects of the present invention are:

[0018] 1) The magnetic pole structure has a simple shape, low processing cost, and the magnetization direction of the magnetic steel is consistent. There is no need to splice multiple magnetic steels with different magnetization directions, thereby improving production efficiency.

[0019] 2) The pole surface of the magnetic pole can be made into a plane. Compared with the pole shoes with complex shapes, the average length of the air gap between the magnetic poles of the present invention is reduced, which is beneficial to increase the magnetic field strength and reduce the cost; at the same time, the effective space of the air gap between the magnetic poles can also be increased, which can improve the comfort of customers when used in nuclear magnetic resonance.

[0020] 3) The magnetic pole structure can be assembled without magnetizing the magnetic steel first, and then magnetized as a whole after assembly, which greatly reduces the assembly cost and difficulty. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a rendering of Embodiment 1 of the present invention;

[0022] Figure 2 This is a schematic diagram of the three-dimensional structure of the magnetic pole of Example 1 of the present invention;

[0023] Figure 3 This is a schematic diagram of the pole shoe structure of Example 1 of the present invention;

[0024] Figure 4 This is a schematic diagram of the front structure of the magnetic pole of Example 1 of the present invention;

[0025] Figure 5 This is a rendering of Embodiment 2 of the present invention;

[0026] Figure 6 A schematic diagram of the three-dimensional structure of the magnetic pole of the pole shoe design 1 of embodiment 2 of the present invention;

[0027] Figure 7 A schematic diagram of the structure of the pole shoe design of embodiment 2 of the present invention;

[0028] Figure 8 A schematic diagram of the front structure of a magnetic pole of a pole shoe design 1 of Embodiment 2 of the present invention;

[0029] Fig. 9 A schematic diagram of the side structure of a magnetic pole of a pole shoe design 1 of embodiment 2 of the present invention;

[0030] Fig.10 A schematic diagram of the three-dimensional structure of the magnetic pole of the pole shoe design 2 of embodiment 2 of the present invention;

[0031] Fig.11 This is a schematic diagram of the second structure of the pole shoe design of embodiment 2 of the present invention;

[0032] Fig.12 This is a schematic diagram of the front structure of the magnetic pole of the pole shoe design 2 of embodiment 2 of the present invention;

[0033] Fig.13 It is a schematic diagram of the side structure of the magnetic pole of the pole shoe design 2 of embodiment 2 of the present invention;

[0034] Fig.14 A uniform magnetic field diagram in the air gap of the present invention;

[0035] Fig.15 This is a magnetic field uniformity diagram within a spherical region with a diameter of 400 mm according to the present invention;

[0036] Fig.16 It is the magnetic field intensity diagram in the spherical region with a diameter of 400 mm of the present invention;

[0037] Fig.17 The magnetic field uniformity of the magnetic pole area of ​​450×70mm^2 of the present invention;

[0038] Fig.18 The magnetic field strength of the magnetic pole area of ​​450×70mm^2 of the present invention;

[0039] Fig.19 is a magnetic field line distribution diagram of the present invention;

[0040] In the figure: 1- yoke, 2- magnet, 3- pole shoe, 4- air gap. DETAILED DESCRIPTION

[0041] The present invention will be further described below in conjunction with the accompanying drawings.

[0042] A permanent magnet system with a large-range high-uniformity magnetic field comprises a yoke 1 and magnetic poles arranged at the upper and lower positions of the yoke 1, the magnetic poles comprising magnetic steel 2 and pole shoes 3, the magnetic steel 2 is arranged at the relative positions of two yokes 1 (the magnetic steel 2 and the yoke 1 are bonded and fixed), and the pole shoes 3 are arranged on the magnetic steel 2; the side of the pole shoe 3 in contact with the magnetic steel 2 adopts a curved surface structure and is embedded in the interior of the magnetic steel 2 through the curved surface structure (the pole shoe 3 and the magnetic steel 2 are bonded and fixed); the side of the pole shoe 3 away from the contact with the magnetic steel 2 adopts a flat structure, so as to form a uniform air gap between the two opposite pole shoes 3.

[0043] The invention can achieve high magnetic field uniformity in a larger air gap and is a permanent magnet system with a new magnetic pole structure. The invention can achieve the effect of uniform magnetic field as follows: Fig.19 : In the figure, there is a magnetic yoke 1, a magnetic steel 2, a pole shoe 3 and an air gap 4, wherein the width of the air gap and the width of the magnetic pole are set to 25 mm. By adopting the magnetic pole design of the present invention, a very uniform magnetic field can be generated in the air gap between the two pole shoes with a width of 25 mm, such as Fig.14 As shown, the magnetic field changes very little in the range of 5mm-20mm.

[0044] Embodiment 1:

[0045] As shown Figure 1-4 in the figure, the permanent magnet system for a large - range and high - uniformity magnetic field is composed of a U - shaped yoke + cylindrical magnetic pole structure.

[0046] The yoke 1 adopts a U - shaped structure, and the magnetic poles adopt a cylindrical structure. The curve of the curved surface structure is a part of an ellipse, a circle, a parabola, a hyperbola, etc., or a stepped or serrated broken line approximating the curve. Among them, the elliptical cross - section structure (the upper curve of the ellipse) can generate high magnetic field strength and magnetic field uniformity.

[0047] In this embodiment, the mathematical model of the elliptical cross - section structure satisfies:[[]]END]]

[0048]

[0049] where a is the major axis, b is the minor axis, k is a constant and a > b > 0, z≥k, k∈[-b,b];

[0050] The surface of the pole shoe 3 facing the air gap is a plane. The plane structure of the pole shoe 3 is higher than, lower than, or flush with the bottom surface of the magnet 2. When the plane is flush with the bottom surface of the magnet 2, it has high magnetic field strength and magnetic field uniformity; the maximum outer diameter b of the pole shoe 3 should be less than the outer diameter g of the magnet 2. When 40%*g < b < 90%*g, it has high magnetic field strength and magnetic field uniformity. The smaller the air gap, the closer the maximum outer diameter b of the pole shoe is to 90%*g; the larger the air gap, the closer the outer diameter b of the pole shoe is to 40%*g.

[0051] The selection of the air gap e is related to d. When 0 < e < 3*d, it has high magnetic field strength and magnetic field uniformity, and the smaller the value of e, the higher the magnetic field strength and uniformity.

[0052] The material of the yoke 1 can be conventional magnetic - conducting materials such as 416 stainless steel, 1010 stainless steel, or Q235 steel; the material of the pole shoe 3 can be materials with high saturation magnetic field strength such as pure iron for electrical engineering DT4, 1J22, hiperco50, etc.; for the yoke 1 and the pole shoe 3, materials with high magnetic permeability and high saturation magnetic field strength can improve the magnetic field strength and magnetic field uniformity in the air gap. The yoke 1 can be processed integrally or segmented and then spliced according to the actual size.

[0053] The material of the magnet 2 can be strong magnetic materials such as sintered ferrite materials, sintered SmCo materials, or NdFeB materials, and the higher the magnetic performance, the higher the magnetic field strength in the air gap of the gap; the magnet 2 can be processed integrally or segmented and then spliced according to the actual size; the thickness f of the magnet 2 should be greater than the thickness d of the pole shoe 3. Increasing the thickness f of the magnet 2 helps to improve the magnetic field strength in the air gap.

[0054] The magnetization directions of the upper and lower magnetic poles are the same, both parallel to the thickness f of the magnetic steel, and there is no need to splice multiple magnetic steels with different magnetization directions.

[0055] Embodiment 2:

[0056] like Figure 5-13 As shown: The permanent magnet system with a large range and high uniformity magnetic field is composed of a C-type yoke + long hair pole structure.

[0057] The yoke 1 adopts a C-shaped structure, the magnetic pole adopts a rectangular structure, the pole shoe 3 is embedded in the magnetic steel 2, and the curve of the curved surface structure is a part of an ellipse, a circle, a parabola, a hyperbola, etc., or a stepped or serrated broken line approximating the curve, wherein the structure in which two ellipsoids intersect or merge can generate high magnetic field strength and magnetic field uniformity.

[0058] There are two designs of pole shoe shapes:

[0059] Pole shoe design 1: The pole shoe 3 curved surface structure consists of two ellipsoidal intersecting structures:

[0060] The two ellipsoids are ellipsoid 1 and ellipsoid 2, where

[0061] Mathematical model of ellipsoid 1: Where a is the major axis and c is the minor axis;

[0062] Mathematical model of ellipsoid 2: Where b is the major axis and c is the minor axis;

[0063] For both ellipsoid 1 and ellipsoid 2, a>c>0 and b>c>0, z≥k, k∈[-c,c];

[0064] If there is a point A with coordinates (x, y, z) that satisfies the mathematical models of ellipsoid 1 and ellipsoid 2, then the collection of this point is the intersection structure of ellipsoid 1 and ellipsoid 2;

[0065] Pole shoe design 2: Pole shoe 3 curved surface structure Two parts of the ellipsoidal structure are combined:

[0066] The two ellipsoids are ellipsoid 1 and ellipsoid 2, where

[0067] Mathematical model of ellipsoid 1: Where a is the major axis and c is the minor axis;

[0068] Mathematical model of ellipsoid 2: Where b is the major axis and c is the minor axis;

[0069] For both ellipsoid 1 and ellipsoid 2, a>c>0 and b>c>0, z≥k, k∈[-c,c];

[0070] If there is a point A with coordinates (x, y, z), and it satisfies the mathematical model of either ellipsoid 1 or ellipsoid 2, then the set of such points is the combined structure of ellipsoid 1 and ellipsoid 2;

[0071] The following rules apply to both pole shoe design 1 and pole shoe design 2:

[0072] The surface of pole shoe 3 facing the air gap is a plane, which can be slightly higher or lower than the surface of the permanent magnet. When it is flush with the bottom surface of permanent magnet 2, it has high magnetic field strength and magnetic field uniformity; for the length b1 and width b2 of pole shoe 3 and the length g1 and width g2 of the permanent magnet, there is the following relationship: b1 < g1 and b2 < g2; when 40% * g1 < b1 < 90% * g1 and 40% * g2 < b2 < 90% * g2, the air gap has high magnetic field strength and magnetic field uniformity. Among them, the smaller the air gap, the closer the outer diameter b1 (b2) of the pole shoe is to 90% * g1 (90% * g2); the larger the air gap, the closer the outer diameter b1 (b2) of the pole shoe is to 40% * g1 (40% * g2).

[0073] The selection of the air gap e is related to the thickness d1 in the width direction and the thickness d2 in the length direction of pole shoe 3. When 0 < e < 3 * d1 and 0 < e < 3 * d2, it has high magnetic field strength and magnetic field uniformity, and the smaller the value of e, the higher the magnetic field strength and uniformity; when d1 = d2, the magnetic field uniformity of the air gap can be further increased.

[0074] The material of yoke 1 can be conventional magnetic conductive materials such as 416 stainless steel, 1010 stainless steel or Q235 steel; the material of the pole shoe can be materials with high saturation magnetic field strength such as pure iron for electrical engineering DT4, 1J22, hiperco50, etc.; for yoke 1 and pole shoe 3, materials with high maximum magnetic permeability and high saturation magnetic field strength can improve the magnetic field strength and magnetic field uniformity of the air gap; yoke 1 can be selected for integral machining or segmented machining and then splicing according to the actual size.

[0075] The material of permanent magnet 2 can be strong magnetic materials such as sintered ferrite material, sintered SmCo material, or NdFeB material, and the higher the magnetic performance, the higher the magnetic field strength of the air gap in the gap; permanent magnet 2 can be selected for integral machining or segmented machining and then splicing according to the actual size; the thickness f of permanent magnet 2 should be greater than the thicknesses d1 and d2 of pole shoe 3. Increasing the thickness f of permanent magnet 2 helps to improve the magnetic field strength of the air gap.

[0076] The magnetization directions of the upper and lower two magnetic poles are the same, both parallel to the magnetic induction thickness f direction.

[0077] Example 3:

[0078] A permanent magnet system that can be used for nuclear magnetic resonance, such as Figure 1 , using a cylindrical magnetic pole structure, the yoke 1 is selected as a mouth shape. The overall appearance size is 2400*2200*1200mm, the air gap length is 500mm, the pole face diameter is 1800mm, and the magnetic field strength reaches 3900Gs in the spherical area with a diameter of 400mm in the center of the air gap. The uniformity of the air gap is less than 20ppm, and the overall weight is less than 20 tons. The material of the magnetic steel 2 is N48H, the material of the magnetic yoke is electrical pure iron DT4, and the pole shoe material is Hiperco50; the simulated calculation of the magnetic field uniformity and magnetic field strength of the permanent magnet structure, such as Fig.15 and Fig.16 .

[0079] Embodiment 4:

[0080] A permanent magnet system that can be used in an atomic absorption spectrophotometer such as Figure 5 , using a rectangular magnetic pole structure (the pole shoe adopts design 2), the yoke 1 is selected as C type, and the overall appearance size is 541*550*370mm. The air gap width is 20mm, the magnetic pole area is 550*200mm^2, and within the range of 450*70mm^2 of the magnetic pole center gap, the magnetic field uniformity is less than 1000ppm and the magnetic field value is greater than 1T; the magnetic steel 2 material is N48H, the yoke material is 1010 steel, and the pole shoe material is electrical pure iron DT4. Simulate and calculate the magnetic field uniformity and magnetic field strength of the permanent magnet structure, such as Fig.17 and Fig.18 .

[0081] The results of the comparison between this application and the prior art (patent number CN94115507.2) are as follows:

[0082]

[0083] Conclusion: Compared with the prior art, the diameter of the uniform field in this application is greatly improved. The uniformity of the uniform field is the percentage difference between the maximum and minimum values, and the smaller the value, the better. Therefore, the uniformity of the uniform field is also greatly improved, and the uniform field volume generated per unit weight is increased by 1.89 times.

Claims

1. A permanent magnet system with a large-range and highly uniform magnetic field, characterized in that: It comprises a magnetic yoke (1) and magnetic poles arranged at upper and lower positions of the magnetic yoke (1), the magnetic poles comprising magnetic steel (2) and pole shoes (3), the magnetic steel (2) being arranged at relative positions of two magnetic yokes (1), and the pole shoes (3) being arranged on the magnetic steel (2); a side of the pole shoes (3) in contact with the magnetic steel (2) adopts a curved surface structure, and is embedded into the magnetic steel (2) through the curved surface structure; a side of the pole shoes (3) away from contact with the magnetic steel (2) adopts a flat surface structure, so that a uniform air gap is formed between the two opposite pole shoes (3); The magnetizing directions of the magnetic poles at the upper and lower positions of the magnetic yoke (1) are consistent; The planar structure of the pole shoe (3) is higher or lower than the bottom surface of the magnetic steel (2), or is flush with the bottom surface of the magnetic steel (2).

2. A permanent magnet system with a large-range and high-uniformity magnetic field according to claim 1, characterized in that: The magnetic yoke (1) adopts a mouth-shaped structure, the magnetic pole adopts a cylindrical structure, and the pole shoe (3) adopts an ellipsoidal cross-section structure.

3. A permanent magnet system with a large-range and high-uniformity magnetic field according to claim 1, characterized in that: The magnetic yoke (1) adopts a C-shaped structure, the magnetic pole adopts a rectangular parallelepiped structure, and the curved surface structure of the pole shoe (3) adopts a structure in which two ellipsoids intersect.

4. A permanent magnet system with a large-range and high-uniformity magnetic field according to claim 1, characterized in that: The magnetic yoke (1) adopts a C-shaped structure, the magnetic pole adopts a rectangular parallelepiped structure, and the curved surface structure of the pole shoe (3) adopts a structure in which two ellipsoids are combined.

5. A permanent magnet system with a large-range and high-uniformity magnetic field according to claim 2, characterized in that: The maximum outer diameter of the pole shoe (3) is smaller than the outer diameter of the magnetic steel (2), and the outer diameter of the pole shoe (3) is greater than 0.4 times the outer diameter of the magnetic steel (2) and less than 0.9 times the outer diameter of the magnetic steel (2), the thickness of the magnetic steel (2) is greater than the thickness of the pole shoe (3), and the width of the air gap between the pole shoes (3) is greater than 0 and less than 3 times the thickness of the pole shoes (3).

6. A permanent magnet system with a large-range and high-uniformity magnetic field according to claim 3, characterized in that: The length and width of the pole shoe (3) are respectively smaller than the length and width of the magnetic steel (2); the length of the pole shoe (3) is greater than 0.4 times the length of the magnetic steel (2) and less than 0.9 times the length of the magnetic steel (2); the width of the pole shoe (3) is greater than 0.4 times the width of the magnetic steel (2) and less than 0.9 times the width of the magnetic steel (2); the thickness of the magnetic steel (2) is greater than the thickness of the pole shoe in the length and width directions; and the width of the air gap between the pole shoes (3) is greater than 0 and less than 3 times the thickness of the pole shoe (3) in the length and width directions.

7. A permanent magnet system with a large-range and high-uniformity magnetic field according to claim 4, characterized in that: The length and width of the pole shoe (3) are respectively smaller than the length and width of the magnetic steel (2); the length of the pole shoe (3) is greater than 0.4 times the length of the magnetic steel (2) and less than 0.9 times the length of the magnetic steel (2); the width of the pole shoe (3) is greater than 0.4 times the width of the magnetic steel (2) and less than 0.9 times the width of the magnetic steel (2); the thickness of the magnetic steel (2) is greater than the thickness of the pole shoe in the length and width directions; and the width of the air gap between the pole shoes (3) is greater than 0 and less than 3 times the thickness of the pole shoe (3) in the length and width directions.

8. A permanent magnet system with a large-range and high-uniformity magnetic field according to claim 1, characterized in that: The material of the magnetic yoke (1) is 416 stainless steel, 1010 stainless steel or Q235 steel, the material of the magnetic steel (2) is sintered ferrite, sintered SmCo or NdFeB, and the material of the pole shoe (3) is electrical pure iron DT4, 1J22 or hiperco50.

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