JP5558923B2 - Magnetic shield body and method of adjusting relative permeability of magnetic shield body - Google Patents

Description

The present invention relates to a magnetic shield body for shielding a magnetic field and a method for adjusting the relative permeability of the magnetic shield body.

  Conventionally, in order to shield a magnetic field, a magnetic shield room has been proposed in which a magnetic field generated by the magnetic field generation source is prevented from leaking outside by covering the magnetic field generation source. This magnetic shield room is put into practical use as a room (hereinafter referred to as “MRI room”) for installing an MRI (Magnetic Resonance Imaging) device used in a medical facility, for example. This magnetic shield room is generally configured by embedding magnetic materials in all or part of walls, ceilings, and floors. Magnetic flux that reaches these walls, ceilings, and floors is made of magnetic materials. By detouring through, the magnetic field is prevented from leaking outside.

  In such a magnetic shield room, the magnetic field generation source is surrounded by a wall, a ceiling, and a floor, so that the internal space of the magnetic shield room is sealed, and there is a possibility of giving a sense of pressure to the occupants. In order to eliminate this point, it has also been proposed to configure a magnetic shield room using an open type magnetic shield (see, for example, Patent Document 1). This open-type magnetic shield body is configured by supporting a plurality of cylinders with a frame body. According to this structure, since the inside and the outside of the magnetic shield room are visually opened through the internal space of the cylindrical body, it is possible to reduce the feeling of pressure on the person entering the room.

  However, since the magnetic shield body of Patent Document 1 has a plurality of cylinders in linear contact with each other, there is a problem that stress concentration occurs in the contact portion. In order to solve this problem, the inventors of the present application proposed a magnetic shield body configured by arranging a plurality of cylinders in a non-contact manner with a space between each other (see Patent Document 2). FIG. 22 is a plan view of a conventional magnetic shield room, and FIG. 23 is a perspective view of a conventional magnetic shield body (a part of the magnetic square tube body is shown as an exploded perspective view). 22 and 23, a magnetic shield body 100 is for shielding magnetism leaking from the MRI chamber, and a plurality of square tubes having magnetic permeability in a plurality of through holes 102 formed in the frame 101. A cylindrical body (magnetic body rectangular cylinder) 103 is mounted. According to this structure, the stress load on the magnetic body rectangular tube 103 can be reduced, and the magnetic shield body 100 can be easily assembled and disassembled.

JP-A-6-13781 JP 2008-160027 A

  In order to improve the magnetic shield performance of the magnetic shield body configured as described above, it may be desired to induce the magnetism incident on the magnetic shield body in a specific direction inside the magnetic shield body.

  For example, in order to further reduce the feeling of pressure of the room occupant, if the magnetism directed in the direction orthogonal to the magnetic shield body can be reduced by inducing more magnetism along the wall surface direction of the magnetic shield body, that much The depth of the magnetic rectangular tube can be shortened, and the pressure on the occupant can be further reduced.

  However, in the magnetic shield body as described in Patent Document 2, the magnitude of the magnetism leaking to the outside is determined by the ratio of the opening width to the depth of each magnetic body rectangular tube, and the opening width must be narrowed. The depth could not be shortened, and only the depth could not be shortened without changing the opening width.

  Alternatively, in order to further reduce the feeling of pressure on the occupant, there is a need to make some openings of the plurality of magnetic body rectangular tubes constituting the magnetic shield body larger than the openings of other magnetic body rectangular tubes. .

  However, in the magnetic shield body described in Patent Document 2, as described above, the magnitude of the magnetism leaking to the outside is determined by the ratio of the opening width and the depth of each magnetic body rectangular tube. The magnetic rectangular tube could not be made large without changing the angle.

  In order to solve such a problem, the relative permeability in a plurality of magnetic body rectangular tubes constituting the magnetic shield body is adjusted for each direction, like a region including a magnetic body rectangular tube having a large opening, It is necessary to reduce the magnetism induced in the region where magnetic leakage is desired to be prevented. And in order to adjust the relative permeability in the magnetic body square tube for each direction in this way, a plurality of magnetic body square tubes are arranged at different intervals from each other, or a number of magnetic body square tubes are arranged with different dimensions. It is conceivable to form or change the thicknesses of a plurality of magnetic body rectangular tubes. However, when the plurality of magnetic rectangular tubes are made to have different dimensions, the labor for manufacturing and managing the magnetic rectangular tubes is increased, the assembly of the magnetic shield body is difficult, and the magnetic There exists a problem that the designability of a shield body falls. In a general magnetic shield body, it is conceivable to induce a magnetic field by using a magnetic body (for example, a directional electrical steel sheet) having a high relative permeability in the horizontal and vertical directions. Unlike the structure, the only way to control the direction of the magnetic field in the depth direction is to change the wall thickness, and it was still difficult to control the direction of the magnetic field.

The present invention has been made in view of such a problem, it can be adjusted without changing the dimensions of the magnetic angular tube constituting the magnetic shield body or the like, the relative permeability for each direction, the magnetic shield, and an object thereof to provide a relative permeability adjustment method of the magnetic shield member.

In order to solve the above-described problems and achieve the object, the magnetic shield body according to claim 1 is configured such that a plurality of hollow magnetic rectangular cylinders formed of a magnetic material are spaced apart from each other via support means. A plurality of magnetic square cylinders, wherein at least two magnetic square cylinders are cut out of only a part of the outer peripheral portion of the magnetic cylinders. It is a notch formed, and is a notch formed at least on the side , and the relative magnetic permeability along the direction perpendicular to the notch is expressed as a magnetic angle of the same shape without the notch. a notch portion for reducing than the relative permeability in the same direction in the cylindrical body, e Bei notches formed in length and width corresponding to the required reduction amount of the relative magnetic permeability, at least 2 Of one of the two magnetic square cylinders And forming position of the notch to definitive, the formation position of the notch in the other part of the magnetic angle cylindrical body, and a mutually different position.

Magnetic shield body according to claim 2 is the magnetic shield body according to claim 1, wherein the plurality of magnetic rectangular cylindrical body including magnetic angle cylindrical body not provided with the cutout portion.

Magnetic shield body according to claim 3 is the magnetic shield body according to claim 1 or 2, wherein the notch is at the sides and corners, z direction, which is the tube axis direction of the magnetic angle cylindrical body It is one that is formed along in the direction orthogonal to the relative magnetic permeability along the z-direction, to reduce than the relative permeability in the same direction in the magnetic angle cylindrical body having the same shape there is no such cutout portion It is a notch part for.

Magnetic shield body according to claim 4 is the magnetic shield body according to any one of claims 1 to 3, wherein the notch is perpendicular to the z-direction is a cylinder axis direction of the magnetic angle cylindrical body in the side along the x direction, the be one that is formed along a direction perpendicular to the x direction, the relative magnetic permeability along the x direction, the magnetism of the same shape is not the cut-out portion It is a notch part for reducing from the relative magnetic permeability of the same direction in a square cylinder.

The magnetic shield body according to claim 5 is the magnetic shield body according to any one of claims 1 to 4, wherein the notch portion includes a z-direction that is a cylinder axis direction of the magnetic rectangular tubular body and the magnetic shield body. The side portion along the y direction perpendicular to the x direction perpendicular to the z direction is formed along the direction perpendicular to the y direction, and the relative permeability along the y direction is It is a notch part for reducing from the relative magnetic permeability of the same direction in the magnetic square cylinder of the same shape without the said notch part.

According to a sixth aspect of the present invention, there is provided a method for adjusting the relative permeability of a magnetic shield body , comprising a plurality of hollow magnetic rectangular cylinders formed of a magnetic material and arranged in parallel with a space therebetween through support means. In the magnetic shield body, a method for adjusting the relative magnetic permeability of the plurality of magnetic square cylinders, comprising a preparation step of preparing the magnetic square cylinder body, and the magnetic square tube prepared in the preparation step A step of forming notches on at least side portions of at least two magnetic square cylinders, the notches being formed by notching only a part of the outer periphery of the magnetic cylinder. And a notch portion for reducing a relative permeability along a direction orthogonal to the notch portion from a relative permeability in the same direction in a magnetic rectangular tube having the same shape without the notch portion. Corresponding to the required reduction of the relative permeability A step of forming notches in length and width, said one of the at least two magnetic angular tube member, a forming position of the notch in a portion of the magnetic angle cylindrical body, a portion of the other magnetic angle A notch portion forming step in which the notch portions are formed at different positions in the cylindrical body .

Relative permeability adjustment method of the magnetic shield body according to claim 7, in relative permeability adjustment method of the magnetic shield body according to claim 6, in the preparation step, bending the plate-like body which is formed of a magnetic material By forming the magnetic rectangular tube, and in the notch portion forming step, the slit or the corner of the magnetic rectangular tube formed by bending the plate-like body is slit with a cutter. A notch is formed.

According to the magnetic shield body of the first aspect, the magnetic shield body is formed by cutting out only a part of the outer peripheral portion of the magnetic cylinder body in at least two of the plurality of magnetic square cylinder bodies. Since at least a cutout portion formed on a side portion is provided , one or more arbitrarily selected from the required directions (vertical direction, horizontal direction, and depth direction) Direction) relative permeability can be reduced by a required reduction amount, and the relative permeability in each direction for each magnetic rectangular tube can be easily adjusted. In particular, since the relative permeability can be adjusted by forming a notch, the mutual spacing of the magnetic square cylinders, the shape and thickness other than the notch can be made constant, and the manufacture and management of the magnetic square cylinder No increase in labor is required, the assembly of the magnetic shield body is easy, and the design of the magnetic shield body is not lowered. For example, in the magnetic shield body of the MRI room, even if the direction and angle of the magnetic field change with the replacement of the MRI, the height, width, and depth of each magnetic square tube body are the same. The support means can be dealt with by replacing the magnetic rectangular cylinders that differ only in the notch portions.
In addition, as a part of the plurality of magnetic square cylinders, there is a magnetic square cylinder whose relative permeability is adjusted by the notch, so that a direction in which the magnetism is to be induced (for example, a magnetic square cylinder with a large opening is avoided) By using a magnetic rectangular cylinder having a relative permeability corresponding to the direction of the magnetic shield, it is possible to reduce the magnetism induced to the specific region of the magnetic shield body and to reduce the magnetism leaking from the specific region of the magnetic shield body. . In particular, since the relative permeability in each direction for each magnetic rectangular tube can be adjusted by forming the notch, the mutual spacing of the magnetic rectangular tube, the shape other than the notch, the thickness, etc. can be made constant. In addition, there is no increase in the manufacturing and management effort of the magnetic rectangular cylinder, the assembly of the magnetic shield body is easy, and the design of the magnetic shield body is not lowered.

According to the magnetic shield body of the third aspect , since the notch portion for reducing the relative permeability along the z direction is provided, the relative permeability in the z direction can be reduced by a required reduction amount. The relative permeability in the z direction of the magnetic rectangular tube can be easily adjusted. In particular, since the relative permeability in the z direction can be adjusted in this way, it is possible to form a magnetic rectangular tube whose depth dimension is narrower (smaller) than the opening width dimension, and conversely, the depth dimension is the same. In some cases, it is possible to use a large-diameter magnetic square tube with a widened (enlarged) opening width, thus improving the transparency of the magnetic shield body and enhancing the feeling of release of the magnetic shield body. Is possible.

According to the magnetic shield body of the fourth aspect , since the notch portion for reducing the relative magnetic permeability along the x direction is provided, the relative magnetic permeability in the x direction can be reduced by a required reduction amount. And the relative permeability in the x direction of the magnetic rectangular tube can be easily adjusted.

According to the magnetic shield body of the fifth aspect , since the notch portion for reducing the relative permeability along the y direction is provided, the relative permeability in the y direction can be reduced by a required reduction amount. The relative permeability in the y direction of the magnetic rectangular tube can be easily adjusted.

According to the method for adjusting the relative permeability of the magnetic shield body according to claim 6, a plurality of hollow magnetic rectangular cylinders formed of a magnetic material are arranged in parallel with a space therebetween through the support means. in the produced magnetic shield, a method for adjusting the relative magnetic permeability of said plurality of magnetic angle cylindrical body, a preparation step of preparing the magnetic angle cylindrical body, the magnetic properties were prepared in the preparation step Of the square cylinders , at least two magnetic square cylinders are cutouts formed by cutting out only a part of the outer peripheral part of the magnetic cylinders, and at least the cutouts are formed on the sides. Reducing the relative permeability in a required direction (one or more directions arbitrarily selected from the three directions of the vertical direction, the horizontal direction, and the depth direction) by a required reduction amount. The relative permeability in each direction for each magnetic square tube It can be adjusted to ease. In particular, since the relative permeability can be adjusted by forming a notch, the mutual spacing of the magnetic square cylinders, the shape and thickness other than the notch can be made constant, and the manufacture and management of the magnetic square cylinder No increase in labor is required, the assembly of the magnetic shield body is easy, and the design of the magnetic shield body is not lowered. For example, in the magnetic shield body of the MRI room, even if the direction and angle of the magnetic field change with the replacement of the MRI, the height, width, and depth of each magnetic square tube body are the same. The support means can be dealt with by replacing the magnetic rectangular cylinders that differ only in the notch portions.
In addition, by using a magnetic rectangular cylinder having a relative permeability corresponding to a direction in which magnetism is to be induced (for example, a direction to avoid a magnetic rectangular cylinder having a large opening), magnetism to be induced in a specific region of the magnetic shield body And the magnetism leaking from the specific region of the magnetic shield body can be reduced. In particular, since the relative permeability in each direction for each magnetic rectangular tube can be adjusted by forming the notch, the mutual spacing of the magnetic rectangular tube, the shape other than the notch, the thickness, etc. can be made constant. In addition, there is no increase in the manufacturing and management effort of the magnetic rectangular cylinder, the assembly of the magnetic shield body is easy, and the design of the magnetic shield body is not lowered.

According to the method of adjusting the relative permeability of the magnetic shield body according to claim 7, the cutout portion is only formed by performing partial processing with a cutter while keeping the shape and size of the magnetic rectangular tube body constant. Thus, since the relative permeability in each direction can be adjusted, the relative permeability can be easily adjusted.

It is a perspective view of the magnetic shield body concerning an embodiment of the invention. It is a perspective view of the magnetic square cylinder of FIG. It is a perspective view of an actual magnetic square cylinder. It is a perspective view of a homogenization model. It is a perspective view of the magnetic square cylinder in which the relative magnetic permeability μx was adjusted. It is a figure which shows the calculation result of the relative magnetic permeability of the homogenization model corresponding to FIG. It is a perspective view of the magnetic square cylinder in which the relative magnetic permeability μy was adjusted. It is a figure which shows the calculation result of the relative permeability of the homogenization model corresponding to FIG. It is a perspective view of the magnetic square cylinder in which the relative magnetic permeability μz was adjusted. It is a figure which shows the calculation result of the relative permeability of the homogenization model corresponding to FIG. FIG. 5 is a perspective view of a magnetic rectangular tube whose relative magnetic permeability μy and μz are adjusted. It is a figure which shows the calculation result of the relative permeability of the homogenization model corresponding to FIG. It is the figure which showed typically the flow of the magnetic flux in the inside of this magnetic square cylinder and the magnetic square cylinder in which the notch is not formed. It is the figure which showed typically the magnetic square tube in which the notch part was formed, and the flow of the magnetic flux in the inside of this magnetic square tube. It is the figure which showed typically the flow of the magnetic flux inside a magnetic square cylinder at the time of cutting all without leaving a connection length, and this magnetic square cylinder. It is a longitudinal cross-sectional view of a magnetic shield body. It is an elevation view of a magnetic shield body. It is a figure which shows the leakage magnetic flux density when not adjusting a relative magnetic permeability. It is a figure which shows the leakage magnetic flux density at the time of adjusting a relative magnetic permeability. It is a figure which shows the magnitude | size and direction of magnetic flux distribution when not adjusting a relative permeability. It is a figure which shows the magnitude | size and direction of magnetic flux distribution at the time of adjusting a relative magnetic permeability. It is a top view of the conventional magnetic shield room. It is a perspective view of the conventional magnetic shield body.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings. However, the present invention is not limited by this embodiment.

(Constitution)
First, the basic configuration of the magnetic shield body will be described. FIG. 1 is a perspective view of a magnetic shield body according to the present embodiment (a part of the magnetic square cylinder is shown as an exploded perspective view), and FIG. 2 is a perspective view of the magnetic square cylinder of FIG. In the following, the distance in the Z direction in FIG. 1 is referred to as “depth”, the distance in the X direction is referred to as “width”, and the distance in the Y direction is referred to as “height”. As shown in FIG. 1, the magnetic shield body 1 is configured by a frame 10 that supports a plurality of magnetic rectangular cylinders 20 so as to be spaced from each other.

  The magnetic shield body 1 is arranged around a magnetic field generation source (not shown), so that all or a part of the magnetic field generated by the magnetic field generation source is exposed to the outside via the magnetic shield body 1. This is to prevent leakage. The magnetic field generation source is arbitrary and includes an MRI apparatus, a permanent magnet, an electromagnetic coil, and a superconducting magnet. The magnetic shield room is configured by arranging the magnetic shield body 1 on its wall, ceiling, or floor, but in addition to the structure in which the magnetic shield body 1 is arranged on the entire surface of these walls, etc., part of these walls and the like. The structure which arrange | positions the magnetic shield body 1 only in this is included. However, parts that are not particularly described can be configured in the same manner as in Patent Document 2.

  The frame 10 is a support means for supporting the magnetic rectangular tube body 20 and is formed in a hollow rectangular tube shape. The plurality of frames 10 may be formed side by side after being formed separately, or may be formed integrally. For example, the frame 10 can be formed between the flat plates by arranging a plurality of flat plates in the horizontal direction and the vertical direction and combining them in a cross-beam shape. A through hole 11 is formed inside the frame 10, and the magnetic rectangular tube 20 can be accommodated in the through hole 11.

  The material of the frame 10 is arbitrary as long as the magnetic resistance is sufficiently larger than that of the magnetic body 12 and has a desired strength for supporting the magnetic rectangular cylinder 20. For example, wood or resin is used. it can. In particular, by using a conductive material as the material of the frame 10, it is possible to obtain an electromagnetic wave shielding effect, and even when the magnetism from the magnetism source varies due to movement of the magnetism source, etc. Magnetism can be reduced by the effect of eddy currents. The vertical cross-sectional shape of the frame 10 in the vertical cross section perpendicular to the central axis of the frame 10 (ZY plane in FIG. 1; hereinafter the same in the case of simply referred to as “longitudinal cross section”) is arbitrary. It has a square shape with the same width and width.

  The magnetic rectangular cylinder 20 is disposed in a through hole 11 formed inside the frame 10 and is formed in a hollow rectangular cylinder shape having an outer dimension substantially matching the inner dimension of the frame 10. The magnetic rectangular tube 20 is disposed between adjacent magnetic rectangular tubes 20 with a space corresponding to the thickness of the frame 10. The magnetic rectangular cylinder 20 is made of a magnetic material. Although the specific kind of this magnetic material is arbitrary, a silicon steel plate (directional silicon steel plate, non-oriented silicon steel plate), a permalloy, an electromagnetic steel plate, or an amorphous plate can be used, for example. In particular, when the magnetic rectangular tube 20 is formed from a silicon steel plate, the material cost is lower than when the magnetic rectangular tube 20 is formed from permalloy or the like, so that the manufacturing cost of the magnetic rectangular tube 20 can be reduced. For example, the magnetic rectangular tube 20 is manufactured by bending one silicon steel plate or joining two silicon steel plates to each other by welding or bonding. When the magnetic rectangular tube 20 is formed by bending one silicon steel plate, it is preferable to initialize the magnetization characteristics by annealing the bent portion. In addition, you may perform the coating for rust prevention etc. on each side surface of the magnetic square cylinder 20. FIG.

  Here, the magnetic rectangular tube 20 is formed with notches 30 to 32. The notches 30 to 32 are formed to adjust the relative magnetic permeability of the magnetic rectangular tube 20, and the side portion 21 along the x direction and the side along the y direction of the magnetic rectangular tube 20. In at least one (all in FIG. 2) of the right-angled corners 23 formed by the part 22 or the side part 21 along the x direction and the side part 22 along the y direction, It is formed as a notch. However, the shape of the notches 30 to 32 is not limited to the slit shape, and may be a hole shape such as a round hole shape or an elliptic hole shape. In addition, as long as a magnetic discontinuous space can be formed by excluding a part of the side portions 21 and 22 and the corner portion 23 of the magnetic rectangular tube body 20, the notch portions 30 to 32 having an arbitrary shape are formed. can do.

  Thus, by forming the notches 30 to 32 in a part of the plurality of magnetic rectangular cylinders 20 constituting the magnetic shield body 1 and adjusting the relative permeability thereof, By forming a region in which the relative permeability is reduced inside the magnetic shield body 1 and guiding the magnetism to flow in a region other than the region, it is possible to reduce magnetism leaking from the predetermined region. . Thus, the area | region which reduces leakage magnetism, the intensity | strength of leakage magnetism, the area | region which forms the notch parts 30-32, the part which forms the notch parts 30-32, and the width | variety of the notch parts 30-32 ( When the notches 30 to 32 are slit-shaped, the length of the notches 30 to 32 (the dimension in the direction perpendicular to the forming direction) (when the notches 30 to 32 are slit-shaped). Can adjust the relative permeability by adjusting the dimension of the cutout portions 30 to 32 in the direction along the direction in which the cutout portions 30 to 32 are formed. Become. Hereinafter, the significance of forming the notches 30 to 32 in this way will be described in more detail. In addition, since the relative permeability is decomposed in three directions of the x direction, the y direction, and the z direction, in the following, the relative permeability in the x direction is μx, the relative permeability in the y direction is μy, and the relative permeability in the z direction. The magnetic susceptibility is referred to as μz.

(Homogenization model)
First, a method for efficiently deriving the relative permeability of the magnetic rectangular tube 20 will be described. In the present embodiment, an actual model (hereinafter referred to as an actual model) of the magnetic rectangular tube 20 is replaced with an equivalent model (hereinafter referred to as a homogenization model) created by homogenizing using a homogenization method. By calculating the relative permeability of the homogenization model, the actual relative permeability of the magnetic rectangular tube 20 is derived. FIG. 3 is a perspective view of an actual magnetic rectangular cylinder 20, and FIG. 4 is a perspective view of a homogenization model. Here, roughly speaking, when a uniform magnetic field is applied to each of the real model and the homogenization model, the magnetic energy of each of the real model and the homogenization model is calculated, and the magnetic energy is mutually calculated. The calculation formula for the relative permeability of the homogenization model is derived on the condition that

  As shown in FIG. 3, the actual magnetic rectangular tube 20 has the following dimensions: width = height = 296 mm, depth = 300 mm, thickness = 3.5 mm, and a gap between other adjacent actual magnetic rectangular tubes 20. = 2 mm, magnetic field magnitude = H, magnetic flux density = B, relative permeability = μ, and magnetic energy per unit volume of the actual magnetic rectangular cylinder 20 = X, this magnetic energy X is expressed by the equation (1 ).

  Here, when the relative permeability in the x direction = μx is derived, the total magnetic energy X (real) of the real model is subjected to a magnetic field analysis in which a uniform magnetic field Bx is applied in the x direction. It is expressed as (2). Here, ne = number of elements of the actual model, ie = value of the element ie, and V = volume of the actual model.

  On the other hand, the magnetic energy X (homo) in the homogenization model of the volume Vh shown in FIG. 4 is expressed as in Equation (3).

  Here, since the total magnetic energy X (real) of the real model and the magnetic energy X (homo) of the homogenization model are equal to each other, the relative permeability in the x direction of the homogenization model = μx is as follows. Equation (4) holds. The relative permeability in the y direction of the homogenization model = μy and the relative permeability in the z direction of the homogenization model = μz can be similarly derived.

(Adjustment method of relative permeability in x direction = μx)
Next, a method for adjusting the relative permeability in the x direction = μx will be described. FIG. 5 is a perspective view of the magnetic rectangular tube 20 (actual model) in which the relative permeability μx is adjusted. The magnetic rectangular cylinder 20 is configured to include a notch 30. This notch 30 is formed in each of the two side parts 21 along the x direction among the side parts 21 and 22 of the magnetic rectangular tube 20, and along the direction orthogonal to the x direction. Is formed.

  Thus, the change of the relative magnetic permeability at the time of forming the notch 30 was calculated using the above-mentioned homogenization model. The dimensions of the actual model shown in FIG. 5 are as follows: width = height = depth = 300 mm, thickness = 7 mm, gap with another adjacent actual magnetic rectangular cylinder 20 = 2 mm, and width of the notch 30 = 5 mm. It was. Further, the relative magnetic permeability of the magnetic rectangular tube 20 before forming the notch 30 was set to μx = μy = 10000 and μz = 1000. And relative permeability (mu) x, (mu) y, (mu) z was computed about the homogenization model (same as FIG. 4) which homogenized this real model. Here, in the side part 21 in which the notch part 30 is formed, the width in the direction along the notch part 30 and the part that remains without being formed on the extension line of the notch part 30 The width (the distance obtained by subtracting the length of the cutout portion 30 from the total length of the side portion 21; hereinafter referred to as the connecting length) is Wx, and the relative permeability μx, μy, when the connecting length Wx is changed. μz was calculated.

The calculation results are shown in FIG. As can be seen from this result, it has been confirmed that the relative permeability μx decreases as the connecting length Wx decreases (the length of the notch 30 increases). Further, it was confirmed that the relative magnetic permeability μy and μz did not change regardless of the connection length Wx. From these, by forming the notch portion 30 along the direction orthogonal to the x direction in the side portion 21 along the x direction among the side portions 21 and 22 of the magnetic rectangular tube body 20, x Only the relative permeability in the direction = μx can be adjusted, and μx can be adjusted to a desired value by changing the length of the notch 30. Further, as can be seen from the result of FIG. 6, the connecting length Wx and the relative permeability μx are not simply proportional, and as the connecting length Wx becomes shorter (as the notch 30 becomes longer). The relative magnetic permeability μx decreases to a quadratic curve. Such a relationship also applies to, for example, the relationship between the number of locations and widths that form the notch 30 and the relative permeability μx. That is, with respect to the number of points, in FIG. 5, the notch 30 is formed on each of the two side portions 21 along the x direction, but in the case of being formed on each of the two side portions 21 in this way. The relative permeability μx is
Compared to the relative permeability μx formed only on one side portion 21, it is not simply halved, but is reduced by 20-30%. Further, regarding the width, in FIG. 5, the width of the notch 30 is set to 5 mm, but even if this width is doubled, the relative magnetic permeability μx is not simply halved but is reduced to a quadratic curve. However, if the total volume of the cutout portion 30 (length × width × thickness of the cutout portion 30) is constant, the cutout portion 30 is cut out as compared with the case where the length of the cutout portion 30 is increased. It has been confirmed that the relative permeability μx is reduced smoothly (with a small change) when the width of the portion 30 is increased so that the relative permeability μx changes slightly. It is preferable at the point which can be made. The tendency regarding the number of points and the width is the same for the y direction and the z direction.

(Adjustment method of relative permeability in y direction = μy)
Next, a method for adjusting the relative permeability in the y direction = μy will be described. FIG. 7 is a perspective view of the magnetic rectangular tube 20 (actual model) in which the relative permeability μy is adjusted. The magnetic rectangular cylinder 20 is configured to include a notch 31. This notch portion 31 is formed in each of the two side portions 22 along the y direction among the side portions 21 and 22 of the magnetic rectangular tube 20, and along the direction perpendicular to the y direction. Is formed.

  Thus, the change of the relative magnetic permeability when the notch 31 was formed was calculated using the homogenization model described above. The dimensions of the actual model shown in FIG. 7, the relative permeability of the magnetic rectangular tube 20 before forming the notch 31, and the calculation conditions for the relative permeability μx, μy, μz are the same as those of the actual model shown in FIG. The relative permeability μx, μy, μz was calculated for a homogenized model obtained by homogenizing this real model (similar to FIG. 4). Here, the relative magnetic permeability μx, μy, μz was calculated when the connecting length Wy was changed.

  The calculation results are shown in FIG. As can be seen from this result, it has been confirmed that the relative permeability μy decreases as the connecting length Wy decreases (the length of the notch 31 increases). It was also confirmed that the relative magnetic permeability μx and μz did not change regardless of the connection length Wy. From these, by forming the notch 31 along the direction orthogonal to the y direction in the side part 22 along the y direction among the side parts 21 and 22 of the magnetic rectangular tube 20, y Only the relative permeability of the direction = μy can be adjusted, and μy can be adjusted to a desired value by changing the length of the notch 31.

(Adjustment method of z-direction relative permeability = μz)
Next, a method for adjusting the relative permeability in the z direction = μz will be described. FIG. 9 is a perspective view of the magnetic rectangular tube 20 (actual model) in which the relative permeability μz is adjusted. The magnetic rectangular cylinder 20 is configured to include a notch 32. The notch 32 is formed at each of the four corners of the magnetic rectangular tube 20 and is formed along a direction orthogonal to the z direction.

  Thus, the change of the relative magnetic permeability when the notch 32 was formed was calculated using the above-mentioned homogenization model. The dimensions of the actual model shown in FIG. 9, the relative permeability of the magnetic rectangular tube 20 before forming the notch 32, and the calculation conditions for the relative permeability μx, μy, μz are the same as those of the actual model shown in FIG. The relative permeability μx, μy, μz was calculated for a homogenized model obtained by homogenizing this real model (similar to FIG. 4). Here, the relative magnetic permeability μx, μy, and μz were calculated when the connection length Wz was changed.

  The calculation results are shown in FIG. As can be seen from this result, it has been confirmed that the relative permeability μz decreases as the connecting length Wz decreases (the length of the notch 32 increases). Further, it was confirmed that the relative magnetic permeability μx and μy did not change regardless of the connection length Wz. From these, by forming the notch 32 along the direction orthogonal to the z direction at the corner of the magnetic rectangular tube 20, only the relative permeability in the z direction = μz can be adjusted, By changing the length of the notch 32, μz can be adjusted to a desired value.

(Adjustment method of relative permeability in multiple directions)
Next, a method for simultaneously adjusting the relative permeability in a plurality of directions will be described. FIG. 11 is a perspective view of the magnetic rectangular tube 20 (actual model) in which the relative magnetic permeability μy and μz are adjusted. The magnetic rectangular cylinder 20 is configured to have the same notches 31 and 32 as those shown in FIGS.

  The change in the relative permeability when the notches 31 and 32 are formed in this way is the case where the relative permeability μy and μz are individually adjusted using a homogenization model (similar to FIG. 4). The same method was used.

  The calculation results are shown in FIG. As can be seen from this result, even when the notch 31 and the notch 32 are formed at the same time, the characteristic of the relative permeability μy is the same as that when only the notch 31 is formed, and the relative permeability is the same. The characteristics of μz are the same as when only the notch 32 is formed, and the connecting length Wy does not affect the relative magnetic permeability μx and μz, and the connecting length Wz is the relative magnetic permeability μx and μy. It was confirmed that it does not affect For these reasons, when the notch 31 and the notch 32 are simultaneously formed in the magnetic rectangular cylinder 20, only the relative permeability in the y direction = μy and the relative permeability in the z direction = μz should be adjusted. The relative permeability μy and μz can be adjusted to desired values by changing the lengths of the notches 31 and 32.

  Although the illustration of the results is omitted, the same results were confirmed when the same cutout portions 30 to 32 as those shown in FIGS. That is, also in this case, the characteristic of the relative permeability μx is the same as that when only the notch 30 is formed, and the characteristic of the relative permeability μy is the same as when only the notch 31 is formed. The characteristics of the relative permeability μz are the same as when only the notch 32 is formed, and the connection length Wx does not affect the relative permeability μy and μz, and the connection length Wy is It was confirmed that the relative permeability μx, μz was not affected, and the connecting length Wz did not affect the relative permeability μx, μy. For these reasons, when the notches 30 to 32 are simultaneously formed in the magnetic rectangular cylinder 20, the relative permeability in the x direction = μx, the relative permeability in the y direction = μy, and the relative permeability in the z direction. = Μz can be adjusted, and the relative magnetic permeability μx, μy, μz can be adjusted to desired values by changing the lengths of the notches 30 to 32.

(Principle of adjusting relative permeability)
The principle that the relative permeability can be adjusted by forming the notches 30 to 32 as described above will be described. As an example, the flow of magnetic flux inside the magnetic rectangular cylinder 20 in which the notch 31 formed along the direction orthogonal to the y direction is formed in each of the two side portions 22 along the y direction will be described. To do. FIGS. 13 to 15 are diagrams schematically showing a plurality of magnetic rectangular cylinders 20 having different formation states of the notches 31 and the flow of magnetic flux in each of the plurality of magnetic rectangular cylinders 20. 13 is a diagram related to the magnetic rectangular tube 20 in which the notch portion 31 is not formed, FIG. 14 is a diagram related to the magnetic square tube 20 in which the notch portion 31 is formed, and FIG. 15 is left with the connecting length Wy. It is a figure regarding the magnetic square cylinder 20 at the time of cutting all. Here, it is assumed that a magnetic flux entering from the lower side to the upper side in the figure is incident.

  As shown in FIG. 13A, in the magnetic rectangular tube 20 in which the notch 31 is not formed, as shown in FIG. 13B, the magnetic flux is the entire area of the side portion 22 along the y direction. It flows through. On the other hand, as shown in FIG. 14A, in the magnetic rectangular tube 20 in which the notch 31 is formed, the magnetic flux is on the side along the y direction as shown in FIG. 14B. Of the portion 22, air does not flow through the notched portion 31 having a high magnetic resistance but flows only through a magnetic body portion (a portion other than the notched portion) having a low magnetic resistance. Further, as shown in FIG. 15 (a), in the magnetic square cylinder 20 that has been completely cut, as shown in FIG. 15 (b), the magnetic flux of the side portion 22 along the y-direction is magnetoresistive. Since there is no low magnetic part (a part other than the notch part), air flows and attenuates through the notch part having air and high magnetic resistance. From these facts, the wider the notch portions 30 to 32 and the longer the notch portions 30 to 32, the less the magnetic flux flows and the higher the magnetic resistance, thereby reducing the relative permeability. I understand that I can do it. In other words, the relative permeability in the desired direction can be reduced by forming the notches 30 to 32 in the specific direction and the specific location with the width and length that match the desired reduction amount of the relative permeability. It can be seen that the amount can be reduced.

(Method of adjusting the relative permeability of the magnetic rectangular tube 20)
Next, a method for adjusting the relative permeability of such a magnetic rectangular tube 20 will be described. The magnetic rectangular cylinder 20 is formed, for example, by bending a plate-like body of magnetic material by a method similar to the conventional method (preparation step). Then, in the stage before or after the folding, the slit-shaped notch is formed by pressing the cutter against the side portions 21 and 22 and the corner 23 of the plate-like body or the magnetic rectangular tube 20. (Cut part) 30-32 is put (notch part formation process). However, the notches 30 to 32 can be formed by other methods. For example, when the magnetic rectangular tube 20 is formed by casting, the notches 30 to 32 are also formed at the time of casting. Can do. Alternatively, the notches 30 to 32 may be formed by punching at a stage before the plate-like body of the magnetic material is bent or at a stage after the magnetic rectangular tube 20 is formed. Further, it is preferable that annealing is performed after the formation of the cutout portions 30 to 32 to improve the deterioration of the magnetic characteristics due to the distortion generated at the time of the cutout, and the relative permeability of each portion of the magnetic rectangular tube 20 is made uniform. .

(Application example of magnetic rectangular tube to magnetic shield)
Next, an example in which the magnetic rectangular cylinder 20 whose relative permeability is adjusted by the above method is applied to the magnetic shield body 1 will be described. Here, a magnetic shield body 1 for reducing magnetic leakage from the MRI room is assumed, and unlike FIG. 1, a magnetic shield body 1 provided with a large opening to reduce the feeling of pressure on the occupant is assumed. The effect of using the magnetic rectangular tube 20 with the adjusted relative permeability was confirmed by three-dimensional magnetic field analysis.

  FIG. 16 is a longitudinal sectional view of an analysis model of the magnetic shield body 1, and FIG. 17 is an elevation view of the analysis model of the magnetic shield body 1. Here, in consideration of the symmetry of the magnetic shield 1, only a ¼ region (upper right region when divided into four by the center line in the x direction and the y direction; the same applies hereinafter) is shown. As a magnetic field generation source, an MRI electromagnet coil (width = depth = 200 mm × 200 mm, height = 1200 mm) magnetomotive force = 40000 AT) is assumed, and the magnetic shield body 1 is installed at a location 2000 mm away from the electromagnet coil. I assumed that. In this model, the magnetic shield body 1 is configured by arranging a magnetic square cylinder 20B having a large opening at the center of a plurality of magnetic square cylinders 20A arranged side by side, and height = width = 7200 mm, depth. = 300 mm. The large opening magnetic square cylinder 20B is formed with height = width = 2400 mm and depth = 300 mm, and the other magnetic square cylinder 20A is formed with height = width = depth = 300 mm.

  The leakage magnetic flux density and magnetic flux distribution when a magnetic field generated from a magnetic source (magnetic coil) is applied to the magnetic shield body 1, the case where the relative magnetic permeability of the magnetic rectangular cylinder 20 is not adjusted, and the magnetic rectangular cylinder Each of the bodies 20A and 20B was adjusted by the relative magnetic permeability in the x, y, and z directions, and was determined by three-dimensional magnetic field analysis and compared.

  18 shows the leakage magnetic flux density when the relative permeability is not adjusted, and FIG. 19 shows the leakage magnetic flux density when the relative permeability is adjusted. In these FIGS. 18 and 19, it is displayed that the color becomes darker as the leakage magnetic flux density in each region of the magnetic shield body 1 increases. As can be seen from FIGS. 18 and 19, the color density included in the region corresponding to the large-opening magnetic rectangular cylinder 20 </ b> B is greater when the relative permeability is adjusted than when the relative permeability is adjusted. Is reduced (that is, the leakage magnetic flux density is reduced). Further, the maximum leakage magnetic flux density from the large opening magnetic rectangular cylinder 20B was about 13T in FIG. 18 and about 7T in FIG.

  Further, FIG. 20 shows the magnitude and direction of the magnetic flux distribution when the relative permeability is not adjusted, and FIG. 21 shows the magnitude and direction of the magnetic flux distribution when the relative permeability is adjusted. 20 and 21, the magnitude of the magnetic flux distribution is indicated by the length of the arrow, and the direction of the magnetic flux distribution is indicated by the direction of the arrow. As can be seen from FIGS. 20 and 21, when the relative permeability is adjusted, the magnetic flux generated from the magnetic coil and incident on the magnetic shield body 1 is larger than that when the relative permeability is not adjusted. It can be seen that it flows so as to avoid the magnetic rectangular tube 20B. From these facts, it was confirmed that the maximum leakage magnetic flux density in the large-diameter magnetic square cylinder 20B can be reduced by adjusting the magnetic resistance of the magnetic square cylinder 20.

(Effect of embodiment)
As described above, according to the present embodiment, the relative permeability along the direction orthogonal to the notch portions 30 to 32, which are the notch portions 30 to 32 formed on the side surfaces or the corner portions, is obtained. The cutout portions 30 to 32 for reducing the relative magnetic permeability in the same direction in the magnetic rectangular cylinder 20 having the same shape without the cutout portions 30 to 32, and the length corresponding to the required reduction amount of the relative permeability. And the notch portions 30 to 32 formed with a width, the relative permeability in a required direction (one or more directions arbitrarily selected from the three directions of the vertical direction, the horizontal direction, and the depth direction). The required reduction amount can be reduced, and the relative magnetic permeability in each direction for each magnetic rectangular tube 20 can be easily adjusted. In particular, since the relative permeability can be adjusted by forming the notches 30 to 32, the mutual spacing of the magnetic rectangular cylinders 20, the shape other than the notches 30 to 32, the thickness, etc. can be made constant. There is no increase in manufacturing and management effort of the rectangular tube body 20, the assembly of the magnetic shield body is easy, and the design of the magnetic shield body 1 is not lowered.

  In addition, since the notch 32 for reducing the relative permeability along the z direction is provided, the relative permeability in the z direction can be reduced by a required reduction amount, and the z direction of the magnetic rectangular tube 20 can be reduced. The relative permeability can be easily adjusted. In particular, since the relative permeability in the z direction can be adjusted in this way, the magnetic rectangular cylinder 20 with the depth dimension narrowed (reduced) with respect to the opening width dimension can be formed, and conversely, the depth dimension is the same. In this case, it is possible to use the magnetic rectangular cylinder 20 having a large opening whose opening width is widened (enlarged), thereby improving the transparency of the magnetic shield 1 and releasing the magnetic shield 1. It is possible to enhance the feeling.

  Further, since the notch 30 for reducing the relative permeability along the x direction is provided, the relative permeability in the x direction can be reduced by a required reduction amount, and the x direction of the magnetic rectangular tube 20 can be reduced. The relative permeability can be easily adjusted.

  In addition, since the notch 31 for reducing the relative permeability along the y direction is provided, the relative permeability in the y direction can be reduced by a required reduction amount, and the y direction of the magnetic rectangular tube 20 can be reduced. The relative permeability can be easily adjusted.

  Moreover, since it has the magnetic square cylinder 20 by which the relative permeability was adjusted by the notch parts 30-32 as some magnetic square cylinders 20, it has the relative permeability according to the direction which wants to induce magnetism. By using the magnetic rectangular tube 20, magnetism to be guided to a specific region of the magnetic shield body 1 can be reduced, and magnetism leaking from the specific region of the magnetic shield body 1 can be reduced.

  Moreover, it is a preparatory process which prepares the magnetic square cylinder 20, and the process of forming the notch parts 30-32 in the side parts 21 and 22 or the corner | angular part 23 of the magnetic square cylinder 20 prepared in this preparatory process, In order to reduce the relative magnetic permeability along the direction orthogonal to the notch portions 30 to 32 from the relative permeability in the same direction in the magnetic rectangular cylinder 20 having the same shape without the notch portions 30 to 32. A notch portion forming step for forming the notch portions 30 to 32 with a length and a width corresponding to a required reduction amount of the relative permeability. The magnetic permeability can be reduced by a required reduction amount, and the relative magnetic permeability in each direction of the magnetic rectangular tube 20 can be easily adjusted. In particular, since the relative permeability can be adjusted by forming the notches 30 to 32, the mutual spacing of the magnetic rectangular cylinders 20, the shape other than the notches 30 to 32, the thickness, etc. can be made constant. The labor for manufacturing and managing the rectangular tube body 20 is not increased, and the design of the magnetic shield body 1 is not lowered.

  In addition, the relative permeability in each direction can be adjusted simply by forming the notches 30 to 32 by performing partial processing with a cutter while keeping the shape and size of the magnetic rectangular cylinder 20 constant. The relative permeability can be easily adjusted.

  In addition, since the relative permeability is calculated by the homogenization method, the relative permeability can be easily calculated as compared with the case where the relative permeability is calculated using only the actual model, and the magnetic shield 1 and the magnetic angle are calculated. The design of the cylindrical body 20 becomes easy.

(Modification to the embodiment)
Although the embodiments of the present invention have been described above, the specific configuration and means of the present invention can be arbitrarily modified and improved within the scope of the technical idea of each invention described in the claims. it can. Hereinafter, such a modification will be described.

  The problems to be solved by the invention and the effects of the invention are not limited to the above-described contents, and the present invention solves the problems not described above or produces the effects not described above. In addition, only a part of the described problems may be solved or only a part of the described effects may be achieved.

  The shapes and numerical values shown in the above embodiment are examples, and each dimension value can be arbitrarily changed.

The overall configuration of the magnetic shield body 1 may be different from the configuration described above. For example, in the above-described embodiment, the magnetic shield body 1 configured by arranging a plurality of magnetic rectangular cylinders 20 on the frame 10 is shown. For example, the magnetic shielding cylinder 1 is configured by a plurality of magnetic rectangular cylinders 20 in this way. The magnetic shield 1 may be configured by arranging a cylindrical shield and a plate-like shield made of a magnetic plate so as to contact each other.
(Appendix)
In order to solve the above-described problems and achieve the object, the magnetic rectangular tube described in appendix 1 is a hollow magnetic rectangular tube formed of a magnetic material, and a magnetic angle for forming a magnetic shield body. In a cylindrical body, a notch portion formed on a side surface or a corner, and the relative magnetic permeability along a direction orthogonal to the notch is the same in a magnetic square cylinder of the same shape without the notch. It is a notch part for reducing the relative permeability in the direction, and has a notch part formed with a length and a width corresponding to a required reduction amount of the relative permeability.
The magnetic square tube described in appendix 2 is the magnetic square tube described in appendix 1, wherein the cut-out portion is a direction perpendicular to the z direction that is the tube axial direction of the magnetic square tube. The notch portion for reducing the relative permeability along the z direction from the relative permeability in the same direction in a magnetic rectangular tube having the same shape without the notch portion. It is.
The magnetic square tube described in appendix 3 is the magnetic square tube described in appendix 1 or 2, wherein the notch is along the x direction orthogonal to the z direction which is the tube axis direction of the magnetic square tube. In addition, the side portion is formed along a direction orthogonal to the x direction, and the relative magnetic permeability along the x direction is the same in the magnetic rectangular cylinder having the same shape without the notch. It is a notch for reducing the relative permeability in the direction.
The magnetic square tube described in appendix 4 is the magnetic square tube according to any one of appendices 1 to 3, wherein the notch includes a z direction that is a tube axial direction of the magnetic square tube and the magnetic square tube. The side portion along the y direction perpendicular to the x direction perpendicular to the z direction is formed along the direction perpendicular to the y direction, and the relative permeability along the y direction is It is a notch part for reducing from the relative magnetic permeability of the same direction in the magnetic square cylinder of the same shape without the said notch part.
The magnetic shield body according to appendix 5 is a magnetic shield body including a plurality of magnetic square cylinders arranged in parallel with each other through a supporting means, and a part of the plurality of magnetic square cylinders As, it has a magnetic square cylinder as described in any one of the above-mentioned supplementary notes 1 to 4.
The method for adjusting the relative permeability of the magnetic rectangular tube according to appendix 6 is a hollow magnetic rectangular tube formed of a magnetic material, and the relative magnetic permeability of the magnetic rectangular tube for constituting the magnetic shield body is adjusted. A method for adjusting, a preparation step of preparing the magnetic rectangular tube, and a step of forming a notch in a side or corner of the magnetic rectangular tube prepared in the preparation step. , A notch portion for reducing the relative permeability along the direction orthogonal to the notch portion than the relative permeability in the same direction in the same shape of the rectangular magnetic cylinder without the notch portion, the ratio A notch portion forming step of forming the notch portion with a length and a width corresponding to a required reduction amount of the magnetic permeability.
The method for adjusting the relative permeability of the magnetic rectangular tube according to appendix 7 is the method for adjusting the relative permeability of the magnetic rectangular tube according to appendix 6, wherein the plate-like body formed of the magnetic material is bent in the preparation step. By forming the magnetic rectangular tube, and in the notch portion forming step, the slit or the corner of the magnetic rectangular tube formed by bending the plate-like body is slit with a cutter. A notch is formed.
(Additional effects)
According to the magnetic square tube described in Appendix 1, the magnetic permeability is a notch formed in the side surface or the corner, and the relative permeability along the direction orthogonal to the notch is not present in the notch. It is a notch part for reducing the relative magnetic permeability in the same direction in the same-shaped magnetic rectangular tube, and has a notch part formed with a length and a width corresponding to a required reduction amount of the relative permeability. Therefore, the relative magnetic permeability in the required direction (one or more directions arbitrarily selected from the three directions of the vertical direction, the horizontal direction, and the depth direction) can be reduced by the required reduction amount. The relative magnetic permeability in each direction for each body can be easily adjusted. In particular, since the relative permeability can be adjusted by forming a notch, the mutual spacing of the magnetic square cylinders, the shape and thickness other than the notch can be made constant, and the manufacture and management of the magnetic square cylinder No increase in labor is required, the assembly of the magnetic shield body is easy, and the design of the magnetic shield body is not lowered. For example, in the magnetic shield body of the MRI room, even if the direction and angle of the magnetic field change with the replacement of the MRI, the height, width, and depth of each magnetic square tube body are the same. The support means can be dealt with by replacing the magnetic rectangular cylinders that differ only in the notch portions.
According to the magnetic rectangular tube described in appendix 2, since the notch for reducing the relative permeability along the z direction is provided, the relative permeability in the z direction can be reduced by a required reduction amount. The relative permeability in the z direction of the magnetic rectangular tube can be easily adjusted. In particular, since the relative permeability in the z direction can be adjusted in this way, it is possible to form a magnetic rectangular tube whose depth dimension is narrower (smaller) than the opening width dimension, and conversely, the depth dimension is the same. In some cases, it is possible to use a large-diameter magnetic square tube with a widened (enlarged) opening width, thus improving the transparency of the magnetic shield body and enhancing the feeling of release of the magnetic shield body. Is possible.
According to the magnetic rectangular tube described in Supplementary Note 3, since the notch portion for reducing the relative permeability along the x direction is provided, the relative permeability in the x direction can be reduced by a required reduction amount. And the relative permeability in the x direction of the magnetic rectangular tube can be easily adjusted.
According to the magnetic rectangular tube described in appendix 4, since the notch portion for reducing the relative permeability along the y direction is provided, the relative permeability in the y direction can be reduced by a required reduction amount. The relative permeability in the y direction of the magnetic rectangular tube can be easily adjusted.
According to the magnetic shield body described in appendix 5, as a part of the plurality of magnetic square cylinders, the magnetic square cylinder whose relative permeability is adjusted by the notch portion is provided, so that the direction in which magnetism is to be induced (for example, By using a magnetic square cylinder having a relative permeability according to a direction that avoids a magnetic square cylinder having a large opening), the magnetism induced to a specific area of the magnetic shield body is reduced, and the specific area of the magnetic shield body is reduced. It is possible to reduce the magnetism that leaks out. In particular, since the relative permeability in each direction for each magnetic rectangular tube can be adjusted by forming the notch, the mutual spacing of the magnetic rectangular tube, the shape other than the notch, the thickness, etc. can be made constant. In addition, there is no increase in the manufacturing and management effort of the magnetic rectangular cylinder, the assembly of the magnetic shield body is easy, and the design of the magnetic shield body is not lowered.
According to the method for adjusting the relative permeability of the magnetic rectangular tube described in appendix 6, a preparatory step for preparing the magnetic rectangular tube, and a notch in the side or corner of the magnetic rectangular tube prepared in the preparatory step. A step of forming a portion for reducing a relative permeability along a direction orthogonal to the notch portion from a relative permeability in the same direction in a magnetic rectangular tube having the same shape without the notch portion. A notch portion and a notch portion forming step for forming the notch portion with a length and a width corresponding to the required reduction amount of the relative permeability, so that the required direction (vertical direction, horizontal direction, and The relative permeability in one or more directions selected from the three directions in the depth direction) can be reduced by the required reduction amount, and the relative permeability in each direction for each magnetic rectangular tube can be easily adjusted. can do. In particular, since the relative permeability can be adjusted by forming a notch, the mutual spacing of the magnetic square cylinders, the shape and thickness other than the notch can be made constant, and the manufacture and management of the magnetic square cylinder No increase in labor is required, the assembly of the magnetic shield body is easy, and the design of the magnetic shield body is not lowered. For example, in the magnetic shield body of the MRI room, even if the direction and angle of the magnetic field change with the replacement of the MRI, the height, width, and depth of each magnetic square tube body are the same. The support means can be dealt with by replacing the magnetic rectangular cylinders that differ only in the notch portions.
According to the method of adjusting the relative permeability of the magnetic rectangular tube according to appendix 7, the notch is formed by performing partial processing with a cutter while keeping the shape and size of the magnetic rectangular tube constant. Thus, since the relative permeability in each direction can be adjusted, the relative permeability can be easily adjusted.

DESCRIPTION OF SYMBOLS 1 Magnetic shield body 10 Frame 11 Through-hole 20, 20A, 20B Magnetic square cylinder 21, 22 Side part 23 Corner part 30-32 Notch part

Claims (7)

A magnetic shield body configured by arranging a plurality of hollow magnetic square cylinders formed of a magnetic material at intervals from each other via a support means ,
Of the plurality of magnetic rectangular cylinders, at least two magnetic rectangular cylinders are notched portions formed by cutting out only a part of the outer peripheral portion of the magnetic cylindrical body, and are formed at least on the side portions. This is a cutout portion, and is used to reduce the relative permeability along the direction perpendicular to the cutout portion, compared to the relative permeability in the same direction in the same shape of the rectangular magnetic cylinder without the cutout portion. a notch portion, e Bei notches formed in length and width corresponding to the required reduction amount of the relative permeability,
Of the at least two magnetic square cylinders, the formation position of the notch in a part of the magnetic square cylinder and the formation position of the notch in another part of the magnetic square cylinder are mutually Different positions,
Magnetic shield body . The plurality of magnetic square cylinders include a magnetic square cylinder that does not include the notch.
The magnetic shield body according to claim 1. The notch, in the sides and corners, there is formed along the direction perpendicular to the z-direction is a cylinder axis direction of the magnetic angle tubular body, relative permeability along the z-direction Is a notch portion for reducing the relative magnetic permeability in the same direction in a magnetic rectangular tube of the same shape without the notch portion,
The magnetic shield body according to claim 1 or 2. The notch is the in the side along the x direction orthogonal to the z-direction is a cylinder axis direction of the magnetic angle cylindrical body, which has been formed along the direction perpendicular to the x-direction, A notch portion for reducing the relative permeability along the x direction from the relative permeability in the same direction in the same shape of the rectangular magnetic cylinder without the notch portion,
The magnetic shield body as described in any one of Claim 1 to 3. The notch is in a direction orthogonal to the y direction at the side portion along the y direction orthogonal to the z direction that is the cylinder axis direction of the magnetic rectangular tube and the x direction orthogonal to the z direction. A notch for reducing the relative permeability along the y-direction from the relative permeability in the same direction in a magnetic rectangular tube having the same shape without the notch. is there,
The magnetic shield body as described in any one of Claim 1 to 4 . In a magnetic shield body configured by arranging a plurality of hollow magnetic square cylinders formed of a magnetic material with a space between each other via a support means, the relative permeability of the plurality of magnetic square cylinders A method for adjusting
A preparation step of preparing the magnetic rectangular tube;
Of the magnetic rectangular cylinders prepared in the preparation step, at least two magnetic rectangular cylinders are cutout portions formed by cutting out only a part of the outer peripheral portion of the magnetic cylindrical bodies, A step of forming a notch portion at least on a side portion , wherein a relative permeability along a direction orthogonal to the notch portion is expressed by a relative permeability in the same direction in a magnetic rectangular tube having the same shape without the notch portion. It is a notch for reducing the magnetic permeability , and is a step of forming a notch with a length and width corresponding to a required reduction amount of the relative permeability, and among the at least two magnetic square cylinders, A notch portion forming step in which a formation position of the notch portion in some magnetic square cylinders and a formation position of the notch portions in another part of the magnetic square cylinder are different from each other ; ,
A method for adjusting the relative permeability of a magnetic shield body including: In the preparation step, the magnetic rectangular tube body is formed by bending a plate-like body formed of a magnetic material,
In the notch forming step, the slit-shaped notch is formed with a cutter on the side or corner of the magnetic rectangular tube formed by bending the plate-like body.
The method of adjusting the relative permeability of the magnetic shield body according to claim 6.

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