JP4123649B2 - Magnetic field generator and method of assembling the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a magnetic field generator and an assembling method thereof, and more particularly, to an MRI magnetic field generating apparatus in which a pole piece is disposed on a main surface of a permanent magnet and an assembling method thereof.
[Prior art]
An example of a method for holding a pole piece in this type of magnetic field generator is disclosed in Japanese Patent No. 2796929. Here, the pole piece (magnetization plate) arranged on the permanent magnet on the plate-shaped yoke is held by the separation preventing means extending from the plate-shaped yoke, thereby preventing the pole piece from being separated from the permanent magnet. It has also been proposed to simultaneously adjust the position of the pole pieces.
[0002]
[Problems to be solved by the invention]
However, in this prior art, it is necessary to dispose the separation preventing means around the permanent magnet, and when the MRI apparatus is assembled, a cover is further attached to this part, so that the apparatus becomes large.
Further, since the pole piece is held from the periphery of the permanent magnet, the size of the separation preventing means is increased, and the component cost is increased.
[0003]
Further, when the MRI apparatus obtained by using this magnetic field generating apparatus is used for interventional (what a doctor performs an operation while viewing a patient's captured image obtained by the MRI apparatus), there is a separation preventing means. Therefore, there is a problem that the doctor is separated from the patient and the work becomes difficult.
Therefore, a main object of the present invention is to provide a magnetic field generator and an assembling method thereof that can obtain an MRI apparatus that is small in size, low in cost, and good in workability.
[0004]
[Means for Solving the Problems]
In order to achieve the above object, the magnetic field generator according to claim 1 has a plate-like yoke having a first through hole, a second through hole formed at a position corresponding to the first through hole, and A permanent magnet provided on the main surface of the plate yoke, a pole piece provided on the main surface of the permanent magnet, and a first through hole and a second through hole for fixing the pole piece to the main surface of the permanent magnet. A fixing member connected to the pole piece without protruding from the surface opposite to the main surface of the plate yoke , the first through hole has a small diameter portion having a smaller diameter than the second through hole, and has a small diameter The diameter of the portion is larger than the diameter of the portion of the fixed member inserted through the small diameter portion and the second through hole, and the fixed member and the pole piece are connected so as to be able to interlock in parallel with the main surface of the permanent magnet. Is.
[0005]
A magnetic field generator according to a second aspect is the magnetic field generator according to the first aspect, wherein the permanent magnet includes a plurality of magnet blocks.
A magnetic field generator according to a third aspect is the magnetic field generator according to the second aspect, wherein adjacent magnet blocks are bonded to each other on the side surfaces.
The magnetic field generator according to claim 4 is the magnetic field generator according to claim 2 or 3 , wherein the magnet block is formed by combining a single magnet having a cubic shape or a rectangular parallelepiped shape.
[0006]
Method of assembling a magnetic field generator according to 請 Motomeko 5, the magnetic field generation comprising a plate yoke, a permanent magnet is provided on the main surface of the plate yoke, and a pole piece provided on a main surface of the permanent magnet A method for assembling an apparatus, wherein a fixing member penetrating a plate yoke and a permanent magnet and a pole piece are connected so as to be interlocked in parallel with the main surface of the permanent magnet, and the fixing member is connected to the plate yoke. It arrange | positions so that it may not protrude from the surface opposite to a main surface, and it fixes a magnetic pole piece to the main surface of a permanent magnet with a fixing member .
[0007]
Method of assembling a magnetic field generator according to 請 Motomeko 6 is the method of assembling a magnetic field generator according to claim 5, the permanent magnets are those containing a plurality of magnet blocks.
Method of assembling a magnetic field generator according to claim 7, method of assembling a magnetic field generator according to claim 6, in which bonding the adjacent magnet blocks each other in each other's side.
The method for assembling the magnetic field generator according to claim 8 is the method for assembling the magnetic field generator according to claim 6 or 7 , wherein the magnet block is formed by combining a single magnet having a cubic or rectangular parallelepiped shape. .
[0008]
In the magnetic field generator according to claim 1, since the pole piece is fixed to the main surface of the permanent magnet by the fixing member that penetrates the plate yoke and the permanent magnet, unlike the conventional case, there is no need to attach a cover, The MRI apparatus can be reduced in size. Further, since the pole piece is not held from the periphery of the permanent magnet, the size of the fixing member is not increased, and the component cost can be suppressed. Furthermore, when the MRI apparatus obtained by using this magnetic field generator is used, for example, in an interventional manner, the fixing member does not get in the way and the doctor can approach the patient, and the workability is improved. Further, by moving the magnetic pole piece together with the fixing member and adjusting the position of the magnetic pole piece on the main surface of the permanent magnet, the magnetic field in the magnetic field generator can be adjusted, and the uniformity of the magnetic field can be ensured. The same applies to the case of using the magnetic field generator assembling method of the magnetic field generator according to claim 5 .
[0009]
In the magnetic field generator according to 請 Motomeko 2, since the permanent magnet is composed of a plurality of magnet blocks, if at a portion to be inserted into the fixing member of the permanent magnet and disposing a plurality of magnet blocks connections, processing By doing so, the through hole for the fixing member can be easily formed at a desired position without scraping the sintered permanent magnet that is likely to be cracked or chipped. The same applies to the case of using the method for assembling the magnetic field generator according to claim 6 .
[0010]
The magnetic field generator according to claim 3, since bonding the adjacent magnet blocks each other in each other's side, can reduce the unevenness of the pole piece side of the permanent magnets, thereby improving the mounting accuracy of the pole pieces. The same applies when the magnetic field generator assembling method according to claim 7 is used.
In the magnetic field generation apparatus according to the fourth aspect , a magnet block having various shapes can be obtained by combining magnets alone, and for example, a magnet block having a recess can be formed. Therefore, if a single magnet is used, a through hole for inserting the fixing member can be easily formed at a desired position of the permanent magnet. The same applies when the magnetic field generator assembling method according to claim 8 is used.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
Referring to FIGS. 1 and 2, an MRI magnetic field generator 10 according to an embodiment of the present invention includes a pair of plate yokes 12 a and 12 b that are opposed to each other so as to form a gap. Permanent magnets 14a and 14b are disposed on the surfaces of the plate yokes 12a and 12b facing each other, and pole pieces 16a and 16b are disposed on the surfaces.
[0012]
As shown in FIG. 2, through-holes 18a and 18b are formed in the plate yokes 12a and 12b. The through holes 18a and 18b are larger than the thicknesses of screws 24a and 24b (described later). Further, through holes 20a and 20b are formed in the permanent magnets 14a and 14b at positions corresponding to the through holes 18a and 18b, respectively. Further, screw holes 22a and 22b are formed in the magnetic pole pieces 16a and 16b at positions corresponding to the through holes 20a and 20b, respectively.
The pole piece fixing screw 24a is inserted into the through holes 18a and 20a, that is, penetrates the plate yoke 12a and the permanent magnet 14a, and is screwed into the screw hole 22a. It is fixed to the main surface of the permanent magnet 14a. Similarly, the pole piece fixing screw 24b is inserted into the through holes 18b and 22b, that is, penetrates the plate yoke 12b and the permanent magnet 14b and is screwed into the screw hole 22b. Is fixed to the main surface of the permanent magnet 14b.
[0013]
As shown in FIG. 3, the permanent magnet 14 a includes a plurality of magnet blocks 26 having, for example, a rectangular parallelepiped shape, a cubic shape, a substantially L-shaped cross section, or a substantially U-shaped cross section. The magnet block 26 is disposed around a projection 28 made of, for example, a nonmagnetic material, and adjacent magnet blocks 26 are bonded to each other with an adhesive. At this time, each magnet block 26 of the permanent magnet 14a is disposed in close contact with the same magnetic pole facing the upper surface. The permanent magnet 14b is configured similarly to the permanent magnet 14a. Such permanent magnet 14a and permanent magnet 14b oppose different magnetic pole faces.
[0014]
The magnet block 26 is formed in a desired shape by fixing a plurality of magnets 30 (see FIG. 4) having a rectangular parallelepiped shape, for example. The magnet 30 is composed of, for example, an R—Fe—B based sintered magnet as disclosed in Japanese Patent Publication No. 62-34242.
Here, what should be noted is the magnet block 26 shown by hatching in FIG. As shown in FIG. 4, the magnet block 26 is a unit in which two types of magnets 30 having different sizes are combined and fixed so that a recess 32 can be formed in part. By using such a magnet block 26, a through hole 20a having a square cross section for the screw 24a can be formed in the permanent magnet 14a. In this embodiment, four through-holes 20a are formed in the permanent magnet 14a bonded on one surface on the plate yoke 12a. The recess 32, that is, one side of the through hole 20a is set larger than the diameter of the screw 24a. As an example, as shown in FIG. 4, when the cross-sectional dimension of the recess 32 is 50 mm × 32 mm, the diameter of the screw 24a is set to 20 mm.
Since the through hole 20b for the screw 24b is formed on the permanent magnet 14b in the same manner as the permanent magnet 14a, a duplicate description is omitted.
[0015]
As described above, the through holes 18a and 18b are formed larger than the thickness of the screws 24a and 24b, and one side of the through holes 20a and 20b is set larger than the diameter of the screws 24a and 24b. As indicated by A, the screw 24a can be moved horizontally in the through holes 18a and 20a, and the screw 24b can be moved in the horizontal direction in the through holes 18b and 20b, respectively. Therefore, as shown in FIG. 5, the magnetic pole piece 16a interlocked with the screw 24a and the magnetic pole piece 16b interlocked with the screw 24b can be moved, respectively, and the position of the magnetic pole piece 16a on the main surface of the permanent magnet 14a, the permanent magnet 14b. The position of the pole piece 16b on the main surface can be adjusted.
[0016]
Next, the pole piece 16a will be described with reference to FIGS. 6 (a) and 6 (b).
The pole piece 16a includes a disk-shaped base plate 34 made of, for example, iron. An annular projection 36 made of, for example, iron and for increasing the magnetic field strength of the periphery is connected to the periphery of the base plate 34 by, for example, a screw 38. A silicon steel plate portion 40 for preventing the generation of eddy current is formed on the base plate 34, and an adjustment piece 42 for adjusting the magnetic field is provided thereon. Silicon steel plate portion 40 is configured by laminating silicon steel plates, and adjustment piece 42 is configured by, for example, an iron piece or a magnet piece.
Since the magnetic pole piece 16b is also configured in the same manner as the magnetic pole piece 16a, its overlapping description is omitted.
Referring back to FIGS. 1 and 2, the pair of plate yokes 12a and 12b are supported and magnetically connected to each other by four columnar yokes 44 having a circular cross section so as to face each other at a predetermined interval.
[0017]
According to the magnetic field generator 10, the magnetic pole piece 16a is fixed to the main surface of the permanent magnet 14a by the screw 24a penetrating the plate yoke 12a and the permanent magnet 14a, and penetrates the plate yoke 12b and the permanent magnet 14b. The pole piece 16b is fixed to the main surface of the permanent magnet 14b by the screw 24b. Therefore, unlike the conventional case, it is not necessary to attach a cover, and the MRI apparatus obtained by using the magnetic field generator 10 can be downsized.
Further, since the magnetic pole pieces 16a and 16b are not held from the periphery of the permanent magnets 14a and 14b, respectively, a large fixing member is not required, and the component cost can be suppressed.
[0018]
Further, when the MRI apparatus obtained using the magnetic field generator 10 is used, for example, in an interventional manner, the screws 24a and 24b, which are fixing members, do not get in the way and the doctor can approach the patient, improving workability. To do.
Further, if necessary, the magnetic field in the magnetic field generator 10 can be adjusted by changing the position of the magnetic pole piece 16a on the main surface of the permanent magnet 14a or the position of the magnetic pole piece 16b on the main surface of the permanent magnet 14b. A uniform magnetic field can be formed in the space between the magnetic pole pieces 16a and 16b.
[0019]
Further, since the permanent magnet 14a is composed of a plurality of magnet blocks 26, a hole is made in the permanent magnet 14a if the plurality of magnet blocks 26 are arranged and connected with a portion through which the screw 24a of the permanent magnet 14a is to be inserted. Without this, the through hole 20a for the screw 24a can be easily formed at a desired position. Since the permanent magnet 14a is usually made of a sintered body that is difficult to process and difficult to open a hole, the advantage that the through hole 22a can be formed without cutting the permanent magnet 14a is great. By forming the magnet block 26 using the single magnet 30, the through hole 20a can be formed more easily. The same effect can be obtained for the permanent magnet 14b.
[0020]
Further, since the adjacent magnet blocks 26 are bonded to each other on the side surfaces, the unevenness on the side of the magnetic pole piece 16a of the permanent magnet 14a can be reduced, and the mounting accuracy of the magnetic pole piece 16a is improved. The same effect is obtained for the permanent magnet 14b, and the mounting accuracy of the pole piece 16b is improved.
[0021]
In the above-described embodiment, the case where the through holes 20a and 20b are formed in the permanent magnets 14a and 14b, respectively, has been described. However, the present invention is not limited to this, and the base plate 34 extends to a position 46 indicated by a broken line in FIG. Then, a screw that passes through the plate yoke 12a but does not pass through the permanent magnet 14a is provided at this position 46 and screwed into the bottom surface of the pole piece 16a, that is, the base plate 34, and the pole piece 16a is fixed on the permanent magnet 14a. It is also possible. The same applies to the pole piece 16b side.
In this case, since the screw does not protrude outside the magnetic pole pieces 16a and 16b, the MRI apparatus can be miniaturized. Moreover, since a screw is used as a member for fixing the magnetic pole pieces 16a and 16b, component costs can be reduced. Further, when the MRI apparatus is used in an interventional manner, the screws do not get in the way and workability is improved.
[0022]
【The invention's effect】
According to the present invention, since the pole piece can be strongly fixed on the permanent magnet with a simple configuration, the cost required for fixing the pole piece can be suppressed.
In addition, when an MRI apparatus obtained using a magnetic field generation apparatus is used in an interventional manner, a doctor can approach the patient, so that the operation is facilitated.
Furthermore, since it is not necessary to cover the fixing member, the MRI apparatus can be reduced in size.
[Brief description of the drawings]
FIG. 1 is a partially omitted perspective view showing an embodiment of the present invention.
FIG. 2 is an illustrative view showing the embodiment of FIG. 1;
FIG. 3 is a plan view showing a permanent magnet and the like.
FIG. 4 is a perspective view showing an example of a magnet block.
FIG. 5 is an illustrative view showing a state in which a screw and a pole piece are moved.
6A is a plan view showing a magnetic pole piece, and FIG. 6B is a cross-sectional view taken along line BB showing the magnetic pole piece.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Magnetic field generator 12a, 12b Plate-shaped yoke 14a, 14b Permanent magnet 16a, 16b Magnetic pole piece 18a, 18b, 20a, 20b Through-hole 24a, 24b, 38 Screw 26 Magnet block 30 Magnet unit 44 Column-shaped yoke

Claims (8)

A plate-shaped yoke having a first through hole;
A permanent magnet having a second through hole formed at a position corresponding to the first through hole and provided on the main surface of the plate yoke;
A pole piece provided on the main surface of the permanent magnet, and a main piece of the plate-like yoke inserted through the first through hole and the second through hole to fix the pole piece to the main surface of the permanent magnet. A fixing member connected to the pole piece without protruding from a surface opposite to the surface ;
The first through-hole has a small-diameter portion having a smaller diameter than the second through-hole, and the diameter of the small-diameter portion is larger than the diameter of the portion inserted into the small-diameter portion and the second through-hole in the fixing member. And the fixing member and the pole piece are connected so as to be able to interlock in parallel with the main surface of the permanent magnet . The magnetic field generator according to claim 1, wherein the permanent magnet includes a plurality of magnet blocks. The magnetic field generator according to claim 2 , wherein the adjacent magnet blocks are bonded to each other on the side surfaces. The magnet block is formed by combining a magnet single cubical or rectangular parallelepiped shape, the magnetic field generator according to claim 2 or 3. A method of assembling a magnetic field generator, comprising a plate yoke, a permanent magnet provided on the main surface of the plate yoke, and a pole piece provided on the main surface of the permanent magnet,
The fixing member penetrating the plate yoke and the permanent magnet and the magnetic pole piece are connected so as to be interlocked in parallel with the main surface of the permanent magnet, and the fixing member is connected to the main surface of the plate yoke. An assembly method for a magnetic field generator, wherein the magnetic pole piece is arranged so as not to protrude from the opposite surface to the main surface of the permanent magnet by the fixing member . The method for assembling the magnetic field generator according to claim 5 , wherein the permanent magnet includes a plurality of magnet blocks. The method of assembling a magnetic field generator according to claim 6 , wherein the adjacent magnet blocks are bonded to each other on their side surfaces. The method of assembling a magnetic field generator according to claim 6 or 7 , wherein the magnet block is formed by combining cubic or rectangular parallelepiped magnets.

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