JPS6312110A - Apparatus for generating uniform magnetic field - Google Patents

Abstract

PURPOSE:To form the title apparatus at a low cost by providing one ring in which a plurality of permanent magnet blocks having at least more than two different sectional areas at a cross section vertical to the ring axis are circularly arrange, and providing adjusting jigs for moving the blocks to adjust the magnetic field, thereby facilitating the adjusting work of the uniform magnetic field. CONSTITUTION:A permanent magnetic unit consists of one ring magnet 1, which is formed with circularly disposed eight permanent magnet blocks 2. The blocks 2 consist of a main portion 6, a narrow portion 7 and an end portion 8, and a back plate 5 of a non-magnetic substance is bonded to the side corresponding to the outer side of the ring when the blocks 2 constitute the magnet 1. Adjusting jigs 4, 4' for moving the blocks 2 to adjust the magnetic field are fixed to a ring-shaped mount 3 which can slidably fit the magnet 1. The jigs 4, 4' are attached to the back plate 5. And the position of the blocks 2 is moved by the jigs 4, 4' to improve the uniformity of the magnetic field. By this, the adjusting work of the magnetic field becomes easy, and the apparatus is formed at a low cost.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a uniform magnetic field generator, and more specifically, a uniform magnetic field generator comprising a ring in which a plurality of anisotropic permanent magnet blocks are arranged annularly. Regarding.

[Prior Art] Various proposals have been made to obtain a uniform magnetic field using permanent magnets. For example, U.S. Patent No. 4,580
, 098 discloses a magnetic field generating device comprising a plurality of rings in which a plurality of anisotropic permanent magnet blocks are arranged annularly.

As shown in FIG. 15, this US patent has five ring magnets 101 to 105, one ring magnet 101 in the center has a positive Br (residual magnetic flux density), and a negative Two ring magnets 102 and 1 with Br
It is described that the most preferable structure is one in which 03 is consecutively provided, and two ring magnets 104 and 105 having positive Br are further provided outside the ring magnets 104 and 105. However, for practical reasons, as shown in FIG.
, 112, 113, and 114 are preferably arranged at certain intervals for a practical device. Furthermore, as shown in FIG. 17, a structure is also described in which three ring magnets 121, 122 and 123 are arranged in series, and the center ring magnet has a smaller outer radius than the outer ring magnets. .

[Problems to be solved by the invention] Conventionally, in a magnetic field generating device using a ring-shaped magnet consisting of a plurality of permanent magnet blocks, a ring-shaped magnet is used to obtain a wide uniform magnetic field space using a relatively light magnetic material. 2 or more were required. Generally, when the number of rings is increased, means for adjusting the distance between the rings can be used for magnetic field adjustment, and it becomes easier to obtain a uniform magnetic field. Furthermore, since the number of blocks increases, the number of post-assembly adjustment means can be increased accordingly.

By the way, a magnetic field generator for NMR-CT is required to have extremely high magnetic field uniformity. For example, if the central magnetic field is 1000 Gauss, the uniformity within the required uniform magnetic field space is required to be 1100 pp or less, and 3000 Gauss or less is required.
Gauss requires a height of 3099m or less.

To achieve this, high precision assembly is required.
At the same time, the assembled structure must be equipped with highly precise magnetic field adjustment means for uniformizing the magnetic field.

However, as the number of rings increases, the number of parts where errors may occur during assembly increases, making it difficult to maintain high assembly accuracy. Moreover, it also has a major disadvantage in that it requires many assembly steps and is complicated.

Furthermore, although increasing the number of rings has the advantage of having more means for adjusting the magnetic field after assembly, highly precise adjustment mechanisms are extremely expensive, and having a large number of them means increasing the cost of the device. This is undesirable because it causes a significant increase in Moreover, since many adjustment mechanisms must be operated, the adjustment work becomes complicated.

Furthermore, when considering use in small NRIs such as those used for animal experiments, it is difficult to install a large number of adjustment mechanisms, and it is also difficult to secure space to operate the adjustment mechanisms, so a large number of rings is required. , it is not realistic to have a structure with many adjustment means.

For the above reasons, there has been a desire for a magnetic field generating device that can obtain a uniform and wide magnetic field space using as few rings as possible and a relatively small amount of magnetic material.

On the other hand, in the above-mentioned conventional magnetic field generator using a ring-shaped magnet, in order to obtain a uniform magnetic field with one ring, an extremely long ring is required in the axial direction of the ring, which increases the weight. It is also huge and unrealistic.

The conventional example of the aforementioned US Pat. No. 4,580,098, namely the five ring magnets 101-1 shown in FIG.
05 are connected in a row, and one ring magnet 101 in the center is positive B.
17th The device shown in the figure in which the three ring magnets 121 to 123 are arranged in series, and the center ring magnet 122 has a smaller outer radius than the outer ring magnets 121 and 123, can be constructed by arranging a plurality of rings in series. This is an interesting structure because it has the possibility of being made to behave as a single ring. However, as a result of studies conducted by the present inventors, it was found that a magnetic field with sufficient uniformity could not be obtained in either case.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a wide uniform magnetic field space using a relatively small amount of magnetic material, which enables highly accurate assembly, has a simple assembly process, and is equipped with sufficient 6H field adjustment means. The object of the present invention is to provide a magnetic field generating device that can.

[Means for Solving the Problems] The present inventors have conducted various studies on the shape, size, arrangement, etc. of the magnets for a magnetic field generation device using a ring magnet consisting of a plurality of permanent magnet blocks, and have earnestly solved the problem. I have continued my research.

As a result, it has been found that the uniformity of the magnetic field is significantly increased when the shape of the permanent magnet block constituting the ring has different cross-sectional areas in at least two places when the block is cut perpendicular to the ring axis.

That is, the present invention includes one ring configured by annularly arranging a plurality of permanent magnet blocks, and the permanent magnet blocks are continuous, and within the same block, there are In cross section, at least 2
It is characterized by having the above different cross-sectional areas.

The shape of such a permanent magnet block will be explained in detail. The permanent magnet block has a plane-symmetrical shape, and within the block, which is a continuous body, the area of the cross section cut perpendicular to the axis of the ring is larger at the left and right image tips than at the main part in the center. A narrow portion having a smaller cross-sectional area than either of the central main portions and the tip portion is provided. A permanent magnet block having such a shape is preferable in order to obtain a wide and uniform magnetic field. It has been found that when a plurality of such permanent magnet blocks are arranged annularly to form one ring, the uniformity of the magnetic field is significantly increased.

Additionally, permanent magnet blocks are usually magnetized and assembled in the form of smaller semi-blocks, but positioning during assembly is easier if there are no irregularities on the inner and/or outer surfaces. , which is preferable because it allows for highly accurate assembly.

Furthermore, in another embodiment of the present invention, a plurality of permanent magnet blocks are arranged in a ring to form one ring, and the uniform magnetic field is adjusted so that the magnetic field generated by the ring is uniform. In the generator, the ring is loosely fitted to a plurality of back plates made of a non-magnetic material fixed to the surface of each of the plurality of permanent magnet blocks corresponding to the outer surface of the ring when forming the ring. a ring-shaped pedestal made of a non-magnetic material, and a plurality of adjustment jigs made of a non-magnetic material, which are fixed to the pedestal and adjustably coupled to a back plate to movably support each of the plurality of permanent magnet blocks. The present invention is characterized in that the plurality of permanent magnet blocks are individually adjusted using an adjustment jig to generate a more uniform magnetic field than the ring.

[Function] According to the present invention, a wide uniform magnetic field space can be obtained even with only one ring. The situation will be explained by comparing FIG. 13 and FIG. 14.

Figure 13 corresponds to a side cross section of a unit when the number of rings is one in a conventional ring-shaped magnet, and the ring axis (
FIG. 3 is a diagram showing magnetic field changes along the Z-axis direction. This figure shows that in conventional ring magnets, the magnetic field near the center is strong, and a wide uniform magnetic field space cannot be obtained.

On the other hand, FIG. 14 corresponds to a side cross section of the ring-shaped magnet unit according to the present invention, and is a diagram showing changes in the magnetic field along the ring axis direction. Here, the cross-sectional area taken perpendicular to the axis of the ring is smaller at the center than at the tip, which solves the drawback of the conventional ring-shaped magnet shown in Figure 13, which is that the magnetic field is stronger near the center. Furthermore, it can be seen that uniformity is improved by providing a portion with a smaller cross-sectional area between the center portion and the tip portion than either.

[Example] The present invention will be described in further detail below with reference to the drawings.

First, the shape of the permanent magnet block used in the magnetic field generator of the present invention will be explained in detail.

FIG. 1 is a side view showing an example of the permanent magnet block 2 in the magnetic field generating device of the present invention.

FIG. 2a is a cross-sectional view of the permanent magnet block 2 taken along the line AA' perpendicular to the ring axis in FIG.

2b is a cross-sectional view of the permanent magnet block 2 taken along the 18° line perpendicular to the ring axis of FIG. 1. FIG.

FIG. 2c is a sectional view of the permanent magnet block 2 taken along line c-c' perpendicular to the ring axis in FIG.

Here, the permanent magnet block 2 includes a main part 6 having a cross-sectional area corresponding to the required magnetic field strength, a narrow part 7 with a small cross-sectional area continuous to both ends of the main part 6, and both ends of these narrow parts 7. The tip portion 8 is connected to the main portion 6 and has a larger cross-sectional area than the main portion 6. In this permanent magnet block 2, the thickness h3 and length 13 of the central main portion 6 are defined by the following equation in accordance with the required magnetic field strength Ha.

Here, R is the required bore diameter, and Br is the residual magnetic flux density of the permanent magnet used. C0 to C8 are coefficients, and in order to obtain the required magnetic field strength, C, = 0.57 to 0.62.
C2=0.81-1.10. C3=0.029
It is preferable to set it to 0.043.

The thickness hl and length C1 of the tip portions 8 at both ends of the permanent magnet block 2 are defined by the following equation in relation to the thickness h3 and length 13 of the main portion 6.

h + = C4h3(R+h3)
(3) Here, B is the required visual field diameter. C4 and CS are coefficients, and in order to obtain the required magnetic field uniformity, fl:
4-1.3X 10-3~1.8x 10-3mm-'
, C, -2.4X 10-' to 3.4X 10-3.

The length fl2 of the narrow portions 7 connected to both ends of the main portion 6 is equal to the length 1. is defined by the following equation in relation to the thickness h3 and the thickness hl of the tip portion 8.

Here, C6 is a coefficient, which is preferably CB-0.9 to 2.0 in order to obtain the required magnetic field uniformity.

Further, the thickness h2 of the narrow portion 7 is defined by the following formula in relation to the thickness h3 of the main portion 6, the thickness hl of the tip portion 8, and the length I12 of the narrow portion 7.

Here, C7 is a coefficient, C7=54~72 (m
m) is preferred in order to obtain the required magnetic field uniformity.

Although the permanent magnet block 2 shown in the first figure has a shape without unevenness on the inner side, the present invention is not limited to this. However, permanent magnet blocks are usually assembled in the form of smaller semi-blocks, but it is easier to position them during assembly if there are no irregularities on the inner and/or outer surfaces. This is preferable because it allows for highly accurate assembly.

Further, although the permanent magnet block 2 in FIG. 1 has a bilaterally symmetrical shape, the shape is not limited to this as long as the above-mentioned conditions are satisfied.

Permanent magnet materials that can be used as the anisotropic permanent magnet block 2 are oriented anisotropic permanent magnets, in particular ar(
A material having a large residual magnetic flux density and a large coercive force is preferable.

For example, rare earth cobalt magnets such as SmCo5, Sm, Co, etc., rare earth magnets such as Nd-Fe-8, etc.
It is possible to use iron magnets, and ferrite magnets or their analogs. Among them, magnets with a high maximum energy product OH,,X and low specific gravity are more preferable.
As such a magnet, Ln (Ln is at least one kind of rare earth elements including Y) 8 to 3 at %, 82 to 2
Examples include permanent magnets whose main phase is tetragonal and whose main components are 8 atomic % and 42 to 9 atomic % Fe.

FIG. 3 is a perspective view of the ring magnet 1 made up of the permanent magnet block 2 shown in the first diagram. This ring magnet 1 is formed by permanent magnet blocks 2 arranged in an annular shape.

In FIG. 3, the permanent magnet unit consisting of one ring magnet 1 is made up of eight anisotropic permanent magnet blocks 2, but the ring magnet 1 may be formed with a larger or smaller number of blocks 2. can.

According to the results of studies conducted by the present inventors, the larger the number of permanent magnet blocks 2 forming the ring magnet 1, the smaller the amount of magnets required to obtain the same central magnetic field. Further, when the number of blocks 2 forming the ring magnet 1 is an even number, it is easy to obtain a uniform magnetic field because the ring magnet 1 has high symmetry.

Furthermore, although the ring magnet 1 has a regular octagonal shape in FIG. It can be long.

FIG. 4 is a diagram showing the magnetization direction 9 of the permanent magnet block 2. FIG. If the axial direction of the ring magnet 1 perpendicular to the plane of the paper is Z, and the plane perpendicular to the axis of the ring magnet 1 is the XY plane, then the ring magnet 1
It is preferable that the permanent magnet blocks 2 forming the .

α=20+π/2 In the above formula, θ is the radial symmetry line 10 of the permanent magnet block 2 and
α is the angle between the easy axis 9 of block 2 and X
This is the angle formed with a line 11 parallel to the axis.

By the way, in a magnetic field generating device using a permanent magnet, several factors can be considered to cause non-uniformity of the magnetic field after assembly. Among these, non-uniformity of magnetic properties among the magnet blocks is an unavoidable problem. Therefore, it is preferable to provide a magnetic field adjustment mechanism that moves the permanent magnet block eight times after assembly. The magnetic field adjusting means will be explained below.

FIG. 5 is a front view of the permanent magnet unit 1 in one embodiment of the uniform magnetic field generator according to the present invention. ring magnet 1
x-y-z of each permanent magnet block 2 constituting
The coordinate axes are defined as shown in FIG. That is, the radial direction of the ring facing outward from the center of the ring magnet 1 is defined as X@, the axial direction of the ring perpendicular to the plane of the paper is defined as the Z axis, and the connecting direction of the rings perpendicular to the X and Z axes is defined as the y axis. .

FIG. 6 is a diagram showing eight movements of the permanent magnet block 2 in the X direction. In other words, permanent magnet block 2 at position 12
Moving 8 to position 13 is called 8 movement in the X direction.

FIG. 7 is a diagram showing eight movements of the permanent magnet block 2 in the X direction. In other words, permanent magnet block 2 at position i14
Moving B to position 15 is called 8 movement in the X direction.

FIG. 8 is a diagram showing the X-axis rotation of the permanent magnet block 2. In other words, rotating the permanent magnet block 2 from position 16 to position 17 is called X-axis rotation.

FIG. 9 is a diagram showing the X-axis rotation of the permanent magnet block 2. In other words, rotating the permanent magnet block 2 from position 18 to position 19 is called X-axis rotation.

In the magnetic field generating device of the present invention, the magnetic field adjusting means preferably includes the above-mentioned means for moving the permanent magnet block 2 in the X direction and the X direction and rotating the X axis. More preferably, the magnetic field adjustment means includes, in addition to these three movable means, a means for moving the permanent magnet block 2 in the X-axis rotation, thereby further improving the magnetic field uniformity.

Furthermore, in addition to the mechanical positional movement of the permanent magnet block 2 as described above, the uniformity of the magnetic field can also be improved by arranging a magnetic field generating coil in relation to the permanent magnet block 2.

Below, an experimental example of the uniformity of the design example of the permanent magnet unit according to the present invention is shown in Table 1 together with the results of examining the conventional example shown in FIGS. 15 and 17.

Here, for comparison, the central magnetic field, the axial length of the ring, and the bore diameter were kept the same. Here, the magnet material is Nd-F
e-B and Br=12300G.

Table 1 and FIG. 10 are perspective views showing an example of a permanent magnet unit of the uniform magnetic field generator according to the present invention.

Here, the permanent magnet unit consists of one ring magnet 1, and this ring magnet 1 is composed of eight permanent magnet blocks 2 arranged in an annular shape, as shown in FIG. A back plate 5 made of a non-magnetic material is adhered to a surface of each of these permanent magnet blocks 2 that corresponds to the outer surface of the ring when the block 2 forms the forceless ring magnet 1. On the other hand, adjustment jigs 4 and 4° for adjusting the magnetic field by moving the permanent magnet block 2 are mounted on a ring-shaped mount 3 into which the ring magnet 1 can be loosely fitted.
These adjustment jigs 4 and 4° are attached to the back plate 5, and each of the permanent magnet blocks 2 is supported in a manner that allows eight rotations. The adjustment jigs 4 and 4° are used to move the position of each permanent magnet block 2 after the permanent magnet unit is assembled, thereby improving the uniformity of the magnetic field. These adjustment jigs 4 and 4° and the pedestal 3 are made of non-magnetic material.

Next, details of preferred examples of such adjustment jigs 4 and 4'' are shown in FIGS. 11 and 12.

FIG. 11 is a plan view showing an example of how one of the permanent magnet blocks 2 is attached to the pedestal 3, when the permanent magnet unit shown in FIG. 10 is viewed from directly above.

In addition, FIG. 12 shows the permanent magnet block shown in FIG.
FIG. 2 is a side view seen from the direction of the arrow in FIG. 1;

As mentioned above, the back plate 5 is adhered to the permanent magnet block 2, and the permanent magnet block 2 is fixed to the mount 3 at two points on the left and right in the longitudinal direction by adjustment jigs 4 and 4 degrees. . The adjustment jigs 4 and 4° are used to adjust the position and orientation of the permanent magnet block 2, and are capable of moving in the X and Y directions, rotating around the X axis, and rotating around the Y axis. Configure the system so that the movement can be adjusted.

That is, in FIGS. 11 and 12, reference numeral 30 denotes a guide member that holds the slide shaft 28 so as to be able to rotate up and down, and these are fixed to the permanent magnet block back plate 5 at approximately symmetrical positions with respect to the center plane of the pedestal 3. has been done. On the other hand, 2
Bearing members 6 and 27 are fixed to the side of the pedestal 3, and rotating shafts 25 and 24 are supported by these bearing members 26 and 27, respectively. In addition, in these figures, a swing arm 22 is rotatably supported on a rotating shaft 24 of a jig 4° on the left, and the tip of the arm 22 is connected to a pin 23.
It is connected to the slide shaft 28 via. Note that here, it is assumed that there is some play between the swing arm 22 and the pin 23.

On the other hand, the rotating shaft 25 of the jig 4 on the right side of the figure is a sliding shaft 28.
directly connected to. Reference numeral 21 denotes a push bolt screwed into a screw hole provided in each of the arms 26A and 27A of the bearing members 26 and 27. The left jig 4° directly holds the swing arm 22, and the right jig 4 directly holds the slide shaft 28. Reference numeral 20 denotes a push/pull bolt that is fitted onto the slide shaft 28 and can move the slide shaft 28 itself up and down by screwing it in or unscrewing it.

For example, in order to move the adjustment jigs 4 and 4° configured in this way in the X direction, the two push/pull bolts 20 are rotated in the same direction by the same amount on the left and right sides. Also, Y
In order to move in the direction, the left and right bearing members 2 in FIG.
Of the four push bolts 21 provided at 6 and 27, loosen the two push bolts 21 on the side you want to move (in the figure, either the top or bottom) according to the amount of movement, and then loosen the push bolts 21 on the opposite side. All you have to do is press it in the same way.

Further, in order to rotate around the X-axis, it is sufficient to use the four push bolts 21 described above and move the left and right in opposite directions, and by this operation, the guide member 3
The slide shaft 28 can be rotated within 0.

Further, rotation around the Y-axis can be performed by moving the push-pull bolt 20 used for movement in the X direction in the opposite left-right direction. The rotation at this time involves the rotating shafts 24 and 25 and the pin 23. Further, the change in distance between the left and right adjusting jigs 4° and 4 caused by the Y-axis rotation is absorbed by the swing arm 22.

Next, the procedure for processing and assembling each part of the magnetic field generating device of the present invention will be explained.

(1) The piece permanent magnet block 2 is small, for example 20mm x 30mm.
It is assembled from anisotropic permanent magnet pieces of approximately 50 mm in diameter.

(2) Semi-block Semi-block is a permanent magnet block divided into several parts, and its size is limited by the ability of the magnetizing machine, handling properties, etc., for example, 200 mm x 20
The size should fit within 0mm x 200mm. The unmagnetized anisotropic permanent magnet pieces described above may be glued together with their easy magnetization axes aligned, or they may be cut into a desired shape in advance and then glued together. Thereafter, cutting and gluing are repeated to obtain a semi-block with the desired shape and magnetization direction. Furthermore, this semi-block is fully ground to achieve the required dimensional accuracy.

(3) Magnetization The semi-block constructed as described above is magnetized in a required magnetic field according to the magnetization direction.

(4) Block-forming The magnetized semi-blocks are adhered one after another with high precision using a jig to obtain a permanent magnet block 2 as shown in FIG.

(5) Unitization (ring formation) A plurality of permanent magnet blocks 2 constructed in this manner are attached to the pedestal 3 using the jig 4 and a 4° angle to form a permanent magnet unit.

(6) Adjust the position of the permanent magnet block using the initial setting adjustment jigs 4 and 4'' to match the design value.

Next, the magnetic field adjustment procedure will be explained.

(1) Magnetic field measurement Measure the magnetic field at a large number of points (for example, 91 points) on the surface of the viewing space (sphere) of the required size at the center of the permanent magnet unit.
Measure using an MR probe.

(2) Evaluation of uniformity The uniformity of the magnetic field is expressed in ppm by dividing the difference between the largest value and the smallest value by the absolute magnetic field (average value) based on the results of the above magnetic field measurement.

For example, in a unit with a central magnetic field of 3000 Gauss, 30
ppm or less is required.

(3) Adjustment First, the pattern of non-uniformity is determined by the magnetic field measurement in (1). Next, the amount of movement of each permanent magnet block 2 (X direction,
The position where the uniformity is best is determined by computer simulation using parameters (Y direction, X axis rotation, Y axis rotation). Using the adjustment jigs 4 and 4°, each permanent magnet block 2 is moved to the position determined as described above.

Repeat steps (1), (2), and (3) below until the desired uniformity is obtained.

[Effects of the Invention] As is clear from the above explanation, according to the uniform magnetic field generator of the present invention, even when the number of rings in the ring magnet is one, a wide and uniform magnetic field space can be obtained. The number of magnetic field adjustment mechanisms that must be provided can be extremely small. As a result, the work of adjusting the magnetic field becomes easy, and the device can be constructed at low cost.

In addition, in the present invention, since the number of rings is reduced, the assembly process can be reduced, and the structure of the pedestal that holds the permanent magnet block can be simplified, which also contributes to the construction of the device at low cost. do.

Therefore, the present invention provides, for example, each magnetic resonance imaging apparatus (
It is most suitable for equipment such as NMR-(:T) which requires an extremely uniform and relatively wide uniform magnetic field space.

[Brief explanation of the drawing]

Fig. 1 is a side view showing an example of a permanent magnet block constituting a permanent magnet unit used in the present invention, Fig. 2a, Fig. 2b
Figures 2c and 2c are cross-sectional views taken along line AA', line B-8' and line c-c', respectively, of the permanent magnet block shown in figure 1. Figure 3 is a ring magnet according to an embodiment of the present invention. FIG. 4 is a perspective view showing an example; FIG. 4 is a diagram showing the magnetization direction of the permanent magnet blocks; FIG. 6, 7, 8 and 9 are explanatory diagrams of the magnetic field adjustment means, FIG. 1O is a perspective view showing an embodiment of the uniform magnetic field generator according to the present invention, and FIGS. 11 and 12. 10 shows an example of the installation of the permanent magnet block shown in FIG. 10, respectively, a plan view and a side view, FIG. 13 is a magnetic field distribution diagram of the conventional example, FIG. 14 is a magnetic field distribution diagram according to the present invention, FIG. 15, FIGS. 16 and 17 are cross-sectional views showing three examples of conventional ring magnets. DESCRIPTION OF SYMBOLS 1... Permanent magnet unit (ring), 2... Anisotropic permanent magnet block, 3... Frame, 4.4'... Adjustment jig, 5... Back plate, 6... Main part, 7...□Narrow part, 8... Tip part. Ki Eki Eki Ekimaegumi Former 70 Tsuku's direction of becoming an E company Figure 4 Eichichi Katoriishi 7 Palo Fu's coordinates Vehicle weight 1 including day and month Figure 5 Permanent 1 Magnetic direction in 1 direction The 4th row rib 'l' is shown as 2, 6th drawing 1, the 9-direction edge of the permanent TQ hae opening 7 is shown as 1 tjJ, 7th figure 7th figure 8th figure 8 permanent magnet a07 mill shaft rotation hill ho Fig. 9'' S age (Hisong I row 0) B view Fig. 15 Concave view of Dansong 11 Fig. 16-C', A- Cross-sectional view of Sasaichi Sousuke 11 Fig. 17

Claims (1)

[Scope of Claims] 1) A ring configured by arranging a plurality of permanent magnet blocks in an annular shape, the permanent magnet block being a continuous body, and within the same block, the axis of the ring 1. A uniform magnetic field generator characterized by having at least two or more different cross-sectional areas in a cross section perpendicular to a direction. 2) The uniform magnetic field generating device according to claim 1, wherein the permanent magnet block has a plane-symmetrical shape. 3) The cross-sectional area of the permanent magnet block cut perpendicularly to the axis of the ring is larger at both left and right tips than at the center main portion, and the area between the center main portion and both tips is larger. 3. The uniform magnetic field generating device according to claim 2, further comprising a narrow portion in the middle having a smaller cross-sectional area than each of the central main portion and both tip portions. 4) A uniform magnetic field generator in which a plurality of permanent magnet blocks are arranged in a ring to form one ring, and the magnetic field generated by the ring is adjusted to be uniform, wherein the plurality of a plurality of back plates made of non-magnetic material fixed to a surface of each permanent magnet block corresponding to the outer surface of the ring when forming the ring; and a ring made of non-magnetic material into which the ring can be fitted loosely. a pedestal, and a plurality of adjusting jigs made of a non-magnetic material fixed to the pedestal and adjustably coupled to the back plate to movably support each of the plurality of permanent magnet blocks. . A uniform magnetic field generating device, characterized in that the plurality of permanent magnet blocks are individually adjusted by the adjustment jig to generate a more uniform magnetic field than the ring. 5) The adjustment jig is capable of moving the permanent magnet block in two axial directions perpendicular to the axial direction of the ring, and is also capable of rotating the permanent magnet block around the two axial directions. A uniform magnetic field generating device according to claim 4, characterized in that: