JP4816690B2 - Magnetic field generator for MRI - Google Patents

Magnetic field generator for MRI Download PDF

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JP4816690B2
JP4816690B2 JP2008176684A JP2008176684A JP4816690B2 JP 4816690 B2 JP4816690 B2 JP 4816690B2 JP 2008176684 A JP2008176684 A JP 2008176684A JP 2008176684 A JP2008176684 A JP 2008176684A JP 4816690 B2 JP4816690 B2 JP 4816690B2
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permanent magnet
magnetic field
field generator
mri
plate
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JP2008279265A (en
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重生 橋本
雅昭 青木
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Proterial Ltd
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Hitachi Metals Ltd
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Description

この発明はMRI用磁界発生装置に関し、より特定的には、永久磁石群が磁極片との接触部よりも外方に突出した突出部を有するMRI用磁界発生装置に関する。   The present invention relates to a magnetic field generator for MRI, and more particularly to a magnetic field generator for MRI in which a permanent magnet group has a protruding portion protruding outward from a contact portion with a pole piece.

従来より、永久磁石型のMRI用磁界発生装置においては、永久磁石群を構成する各永久磁石は、隣接する永久磁石、板状継鉄あるいはそれらの両方に接着剤を用いて接着される。   Conventionally, in a permanent magnet type MRI magnetic field generator, each permanent magnet constituting a group of permanent magnets is bonded to an adjacent permanent magnet, a plate yoke, or both using an adhesive.

しかし、このような構成によれば、磁界発生装置の輸送中の振動や衝撃等によって通常の設計値を超える機械的な負荷が永久磁石群にかかった場合、永久磁石群を構成する永久磁石を十分に保持することができず、当該永久磁石が、隣接する永久磁石や板状継鉄から分離しひいては永久磁石群から離脱してしまう場合がある。この場合には、MRI用磁界発生装置の磁界均一度が保てなくなり、磁界強度が低下する。   However, according to such a configuration, when a mechanical load exceeding a normal design value is applied to the permanent magnet group due to vibration or impact during transportation of the magnetic field generator, the permanent magnets constituting the permanent magnet group are In some cases, the permanent magnets cannot be sufficiently held, and the permanent magnets are separated from the adjacent permanent magnets or plate yokes, and thus separated from the group of permanent magnets. In this case, the magnetic field uniformity of the MRI magnetic field generator cannot be maintained, and the magnetic field strength decreases.

そこで、永久磁石群の側面に成形材を設ける技術が提案されている(たとえば、特許文献1参照)。
また、永久磁石群を保護する磁石カバーを用いる技術が提案されている(たとえば、特許文献2参照)。
特許第2699250号公報 特開平11−178808号公報
Therefore, a technique of providing a molding material on the side surface of the permanent magnet group has been proposed (see, for example, Patent Document 1).
Moreover, the technique using the magnet cover which protects a permanent magnet group is proposed (for example, refer patent document 2).
Japanese Patent No. 2699250 JP-A-11-178808

特許第2699250号公報の技術は、成形材が永久磁石を直接保持するので、当該永久磁石が隣接する永久磁石や板状継鉄から分離することを防止する上で有効である。   The technique of Japanese Patent No. 2699250 is effective in preventing the permanent magnet from being separated from the adjacent permanent magnet or plate yoke because the molding material directly holds the permanent magnet.

しかし、このような成形材を設けるためには、複数の部材からなる型枠を板状継鉄の所定の位置に設けて密封空間を形成し、当該空間内に成形材を充填しその後型枠を取り除く必要があり、多くの工程数を要する。   However, in order to provide such a molding material, a mold frame composed of a plurality of members is provided at a predetermined position of the plate yoke to form a sealed space, and the molding material is filled in the space, and then the mold frame is formed. Need to be removed, which requires many steps.

また、この技術は、永久磁石群の周囲に型枠を配置するスペースがある磁界発生装置には適用できるが、そのようなスペースを有さない磁界発生装置には適用できず、様々な磁界発生装置に用いることができる汎用的な技術ではなかった。   In addition, this technique can be applied to a magnetic field generator having a space for placing a mold around a group of permanent magnets, but cannot be applied to a magnetic field generator that does not have such a space. It was not a general-purpose technology that could be used for the device.

特開平11−178808号公報の技術では、永久磁石群の外周面を覆うように配置された磁石カバーによって永久磁石群を外部から保護することはできるが、磁石カバーと永久磁石群との間には隙間があり、磁石カバーによって永久磁石群を直接保持する構造ではないので、磁石カバー内において、永久磁石が他の永久磁石や板状継鉄から分離することを防ぐことはできない。   In the technique of JP-A-11-178808, the permanent magnet group can be protected from the outside by a magnet cover arranged so as to cover the outer peripheral surface of the permanent magnet group, but between the magnet cover and the permanent magnet group. Since there is a gap and the permanent magnet group is not directly held by the magnet cover, it is impossible to prevent the permanent magnet from being separated from other permanent magnets and plate yokes in the magnet cover.

それゆえにこの発明の主たる目的は、様々な磁界発生装置に適用でき、永久磁石群を構成する永久磁石の分離を防ぐことができる、MRI用磁界発生装置を提供することである。   Therefore, a main object of the present invention is to provide an MRI magnetic field generator that can be applied to various magnetic field generators and can prevent separation of permanent magnets constituting a permanent magnet group.

上述の目的を達成するために、請求項1に記載のMRI用磁界発生装置は、それぞれ相互に接着される複数の永久磁石を含みかつ空隙を形成して対向配置される一対の永久磁石群と、一対の永久磁石群を磁気的に結合するための継鉄と、一対の永久磁石群のそれぞれの空隙側主面に設けられる一対の磁極片とを有し、永久磁石群が磁極片との接触部よりも外方に突出した突出部を有するように構成され、一対の磁極片間の空隙に磁界を発生させるMRI用磁界発生装置において、突出部に配置される永久磁石が永久磁石群から離脱することを防止する永久磁石固定用部材を備え、永久磁石固用定部材が、突出部を構成する複数の永久磁石のうち一部の隣接する永久磁石同士を接続するために突出部のうち対向配置される一対の永久磁石群の間に形成される空隙に臨む表面の一部または突出部の外周面の一部に取り付けられる非磁性金属からなるプレート状部材であることを特徴とする。 In order to achieve the above-mentioned object, an MRI magnetic field generator according to claim 1 includes a pair of permanent magnet groups each including a plurality of permanent magnets bonded to each other and arranged to face each other in a gap. , A yoke for magnetically coupling the pair of permanent magnet groups, and a pair of magnetic pole pieces provided on the respective gap side main surfaces of the pair of permanent magnet groups, In the MRI magnetic field generator configured to have a protruding portion that protrudes outward from the contact portion and generates a magnetic field in the gap between the pair of magnetic pole pieces, the permanent magnets arranged in the protruding portion are from the permanent magnet group. comprises a permanent magnet fixing member for preventing the disengagement, the permanent magnets solid constant-member, of the protrusions to connect between the permanent magnets part of an adjacent one of the plurality of permanent magnets which constitute the projecting portions Between a pair of permanent magnet groups arranged opposite to each other Wherein the part of the outer peripheral surface of a portion or the protruding portion of the surface facing the gap formed a plate-like member made of a nonmagnetic metal attached.

請求項2に記載のMRI用磁界発生装置は、請求項1に記載のMRI用磁界発生装置において、プレート状部材が継鉄にまで延びて固定されることを特徴とする。   The magnetic field generator for MRI according to claim 2 is the magnetic field generator for MRI according to claim 1, wherein the plate-like member extends to the yoke and is fixed.

請求項3に記載のMRI用磁界発生装置は、請求項1または2に記載のMRI用磁界発生装置において、永久磁石固定用部材が設けられた突出部を包囲するリング部材をさらに含むことを特徴とする。   A magnetic field generator for MRI according to claim 3 is the magnetic field generator for MRI according to claim 1 or 2, further comprising a ring member surrounding a protrusion provided with a permanent magnet fixing member. And

請求項4に記載のMRI用磁界発生装置は、請求項3に記載のMRI用磁界発生装置において、リング部材と突出部との間の空間に充填される成形材をさらに含むことを特徴とする。   The magnetic field generator for MRI according to claim 4 is the magnetic field generator for MRI according to claim 3, further comprising a molding material filled in a space between the ring member and the protrusion. .

請求項1に記載のMRI用磁界発生装置では、永久磁石固定用部材を設けることによって、たとえばMRI用磁界発生装置の輸送中に振動や衝撃等が生じても、永久磁石群を構成する永久磁石が隣接する永久磁石や板状継鉄から分離することを防止でき、すなわち永久磁石が永久磁石群から離脱することを防止でき、MRI用磁界発生装置を長期間安定して動作させることができる。また、当該永久磁石固定用部材は、今後提供される磁界発生装置だけではなく既存の磁界発生装置にも用いることができ、磁界発生装置の補強にも好適となる。   In the magnetic field generator for MRI according to claim 1, by providing the permanent magnet fixing member, for example, even if vibration or impact occurs during transportation of the magnetic field generator for MRI, the permanent magnets constituting the permanent magnet group Can be prevented from separating from adjacent permanent magnets and plate yokes, that is, the permanent magnets can be prevented from separating from the permanent magnet group, and the magnetic field generator for MRI can be operated stably for a long period of time. Further, the permanent magnet fixing member can be used not only for a magnetic field generator to be provided in the future, but also for an existing magnetic field generator, and is suitable for reinforcing the magnetic field generator.

また、請求項1に記載のMRI用磁界発生装置では、永久磁石固定用部材として、突出部を構成する複数の永久磁石同士を接続するプレート状部材を用いることによって、突出部の必要な箇所に容易にプレート状部材を設け永久磁石の固定を補強することができる。   Moreover, in the magnetic field generator for MRI according to claim 1, by using a plate-like member that connects a plurality of permanent magnets constituting the protruding portion as a member for fixing the permanent magnet, the MRI magnetic field generating device is provided at a place where the protruding portion is required. A plate-like member can be easily provided to reinforce the fixing of the permanent magnet.

請求項2に記載のMRI用磁界発生装置では、プレート状部材が継鉄にまで延びて固定されることによって、永久磁石と継鉄との接続を強くでき永久磁石をより強く固定できる。   In the magnetic field generator for MRI according to the second aspect, the plate-like member extends to the yoke and is fixed, whereby the connection between the permanent magnet and the yoke can be strengthened and the permanent magnet can be more strongly fixed.

請求項3に記載のMRI用磁界発生装置では、突出部を包囲するリング部材をさらに設けることによって、永久磁石が磁界発生装置から脱落するのを防止でき、かつ永久磁石群を外部から保護することができる。   In the magnetic field generator for MRI according to claim 3, by further providing a ring member surrounding the protruding portion, the permanent magnet can be prevented from falling off the magnetic field generator, and the permanent magnet group can be protected from the outside. Can do.

請求項4に記載のMRI用磁界発生装置では、リング部材と突出部との間に成形体を充填することによって、永久磁石群の突出部を構成する永久磁石をさらに強固に保持することができる。   In the magnetic field generator for MRI according to claim 4, the permanent magnets constituting the projecting portions of the permanent magnet group can be more firmly held by filling the molded body between the ring member and the projecting portions. .

この発明によれば、永久磁石が永久磁石群から離脱することを防止できる。
また、この発明は、今後提供される磁界発生装置だけではなく既存の磁界発生装置に適用できる。
According to the present invention, it is possible to prevent the permanent magnets from leaving the permanent magnet group.
The present invention can be applied not only to a magnetic field generator to be provided in the future, but also to an existing magnetic field generator.

以下、図面を参照してこの発明の実施形態について説明する。
図1を参照して、この発明の一実施形態のMRI用磁界発生装置10は、オープンタイプのMRI用磁界発生装置であり、空隙を形成して対向配置される一対の磁極ユニット11aおよび11bを含む。
Embodiments of the present invention will be described below with reference to the drawings.
Referring to FIG. 1, an MRI magnetic field generation apparatus 10 according to an embodiment of the present invention is an open type MRI magnetic field generation apparatus, and includes a pair of magnetic pole units 11a and 11b that are arranged to face each other while forming a gap. Including.

磁極ユニット11aおよび11bは、それぞれ板状継鉄12aおよび12bを含む。一対の板状継鉄12aおよび12bのそれぞれの対向面側には永久磁石群14aおよび14bが配置され、永久磁石群14aおよび14bのそれぞれの対向面側には磁極片16aおよび16bが固着される。   The magnetic pole units 11a and 11b include plate yokes 12a and 12b, respectively. Permanent magnet groups 14a and 14b are arranged on the opposing surface sides of the pair of plate yokes 12a and 12b, and magnetic pole pieces 16a and 16b are fixed to the opposing surface sides of the permanent magnet groups 14a and 14b. .

このとき、永久磁石群14aの外周部が磁極片16aとの接触部より外方に突出して突出部18が形成され、永久磁石群14bの外周部が磁極片16bとの接触部より外方に突出して突出部18が形成される。   At this time, the outer peripheral portion of the permanent magnet group 14a protrudes outward from the contact portion with the magnetic pole piece 16a to form a protruding portion 18, and the outer peripheral portion of the permanent magnet group 14b is outward from the contact portion with the magnetic pole piece 16b. Protrusions 18 are formed to project.

永久磁石群14aおよび14bの高さはたとえば100mmである。永久磁石群14aおよび14bは、図2に示すように直方体状あるいは立方体状の複数の永久磁石20を接着によって一体化したものである。また、永久磁石群14aを構成する各永久磁石20は磁化方向が同方向になるように配置され、永久磁石群14bを構成する各永久磁石20は磁化方向が同方向になるように配置される。この実施形態では、永久磁石群14aの永久磁石20は空隙側がN極になるように、永久磁石群14bの永久磁石20は空隙側がS極になるように、配置される。   The height of the permanent magnet groups 14a and 14b is, for example, 100 mm. As shown in FIG. 2, the permanent magnet groups 14 a and 14 b are obtained by integrating a plurality of rectangular or cubic permanent magnets 20 by bonding. Further, the permanent magnets 20 constituting the permanent magnet group 14a are arranged so that the magnetization directions are the same direction, and the permanent magnets 20 constituting the permanent magnet group 14b are arranged so that the magnetization directions are the same direction. . In this embodiment, the permanent magnet 20 of the permanent magnet group 14a is arranged so that the air gap side is an N pole, and the permanent magnet 20 of the permanent magnet group 14b is arranged so that the air gap side is an S pole.

永久磁石20には、たとえばNEOMAX−47(住友特殊金属株式会社製)等の高磁束密度タイプのR−Fe−B系磁石が用いられ、永久磁石20は図示しない磁石単体を組み立てることによって得られる。   For the permanent magnet 20, for example, a high magnetic flux density type R—Fe—B type magnet such as NEOMAX-47 (manufactured by Sumitomo Special Metal Co., Ltd.) is used, and the permanent magnet 20 is obtained by assembling a single magnet (not shown). .

磁極片16aは、永久磁石群14a上に配置されるたとえば鉄からなる円板状のベースプレート22を含む。ベースプレート22上には、うず電流の発生を防止するための珪素鋼板24が形成される。珪素鋼板24は、ベースプレート22上に接着剤で固定される。ベースプレート22の周縁部には、たとえば鉄からなり周縁部の磁界強度を上げ均一磁界を得るための環状突起26が形成される。環状突起26は、たとえば複数の環状突起片を含み、各環状突起片を珪素鋼板24の周縁部に固定することによって環状突起26が形成される。   The pole piece 16a includes a disk-shaped base plate 22 made of, for example, iron and disposed on the permanent magnet group 14a. On the base plate 22, a silicon steel plate 24 for preventing the generation of eddy current is formed. The silicon steel plate 24 is fixed on the base plate 22 with an adhesive. An annular projection 26 made of, for example, iron and increasing the magnetic field strength of the peripheral portion to obtain a uniform magnetic field is formed on the peripheral portion of the base plate 22. The annular projection 26 includes, for example, a plurality of annular projection pieces, and the annular projection 26 is formed by fixing each annular projection piece to the peripheral edge portion of the silicon steel plate 24.

板状継鉄12aおよび12bは一枚の板状の支持継鉄28によって磁気的に結合される。すなわち、支持継鉄28の下端面に板状継鉄12aの一端縁側上面が、支持継鉄28の上端面が板状継鉄12bの一端縁側下面にそれぞれ位置するように、支持継鉄28が板状継鉄12aおよび12bに接続される。したがって、板状継鉄12aおよび12bと支持継鉄28とは、その接続部が略90度の角度を有し側面視コ字状になるように接続される。   The plate yokes 12 a and 12 b are magnetically coupled by a single plate-like support yoke 28. That is, the support yoke 28 is positioned such that the upper surface on one end edge side of the plate-like yoke 12a is located on the lower end surface of the support yoke 28, and the upper end surface of the support yoke 28 is located on the lower surface on one end edge side of the plate-like yoke 12b. Connected to the plate yokes 12a and 12b. Accordingly, the plate yokes 12a and 12b and the support yoke 28 are connected so that the connecting portion has an angle of approximately 90 degrees and is U-shaped in a side view.

図3をも参照して、板状継鉄12aと支持継鉄28との接続部内面側のうち永久磁石群14aから最も遠い位置(この実施の形態では板状継鉄12aと支持継鉄28との接続部内面側の両端)に、それぞれ補強部材30が形成される。同様に、板状継鉄12bと支持継鉄28との接続部内面側のうち永久磁石群14bから最も遠い位置(この実施の形態では板状継鉄12bと支持継鉄28との接続部内面側の両端)に、それぞれ補強部材30が形成される。したがって、補強部材30によって、板状継鉄12aと支持継鉄28とが、板状継鉄12bと支持継鉄28とがそれぞれより強く固定される。
また、板状継鉄12aの下面には4つの脚部32が取り付けられる。
Referring also to FIG. 3, the farthest position from the permanent magnet group 14 a on the inner surface side of the connecting portion between the plate-like yoke 12 a and the supporting yoke 28 (in this embodiment, the plate-like yoke 12 a and the supporting yoke 28. Reinforcing members 30 are respectively formed on both ends of the connecting portion on the inner surface side. Similarly, the position farthest from the permanent magnet group 14b on the inner surface side of the connecting portion between the plate yoke 12b and the supporting yoke 28 (in this embodiment, the inner surface of the connecting portion between the plate yoke 12b and the supporting yoke 28). Reinforcing members 30 are respectively formed at both ends of the side. Accordingly, the reinforcing member 30 fixes the plate yoke 12a and the support yoke 28, and the plate yoke 12b and the support yoke 28 more firmly.
Four leg portions 32 are attached to the lower surface of the plate yoke 12a.

このような磁界発生装置10では、磁極片16aおよび16b間の空隙に磁界が発生し、均一磁界空間F(図1参照)においてたとえば0.2T以上の磁界強度が要求される。
このような磁界発生装置10は、永久磁石固定用部材として図3に示すような鍔状部材34を備える。
In such a magnetic field generator 10, a magnetic field is generated in the gap between the magnetic pole pieces 16a and 16b, and a magnetic field strength of, for example, 0.2 T or more is required in the uniform magnetic field space F (see FIG. 1).
Such a magnetic field generator 10 includes a hook-shaped member 34 as shown in FIG. 3 as a permanent magnet fixing member.

なお、図3,図5,図7,図8および図10では、磁極ユニット11b側が省略されているが、図1に示す磁界発生装置10と同様、空隙を挟んで上下対称の構造を有していることはいうまでもない。但し、永久磁石群14aを構成する永久磁石20はA1の磁化方向を有するように、永久磁石群14bを構成する永久磁石20はA2の磁化方向を有するように、それぞれ配置される。   3, 5, 7, 8, and 10, the magnetic pole unit 11 b side is omitted. However, like the magnetic field generator 10 shown in FIG. 1, it has a vertically symmetrical structure with a gap in between. Needless to say. However, the permanent magnets 20 constituting the permanent magnet group 14a are arranged so as to have the magnetization direction A1, and the permanent magnets 20 constituting the permanent magnet group 14b are arranged so as to have the magnetization direction A2.

図3に示すように、鍔状部材34は、磁極片16aの外周面に鍔状に取り付けられており、突出部18の空隙側表面18a(図1参照)が鍔状部材34によって覆われる。組み立て時には、まず、磁極片16aを永久磁石群14a上に組み立てておき、その後鍔状部材34を磁極片16aの外周面に溶接等により取り付けるようにしてもよい。磁極ユニット11b側においても同様である。   As shown in FIG. 3, the hook-shaped member 34 is attached to the outer peripheral surface of the pole piece 16 a in a hook shape, and the gap-side surface 18 a (see FIG. 1) of the protrusion 18 is covered with the hook-shaped member 34. At the time of assembly, first, the pole piece 16a may be assembled on the permanent magnet group 14a, and then the flange member 34 may be attached to the outer peripheral surface of the pole piece 16a by welding or the like. The same applies to the magnetic pole unit 11b side.

鍔状部材34としては、4mm〜10mm程度の厚みで構成され、アルミニウム、ステンレススチール等の非磁性金属が好ましい。このような非磁性金属は、優れた強度を有しかつ磁界発生装置10に発生する磁界に影響を与えない。また、うず電流の抑制を重視する場合には、非磁性金属からなる鍔状部材34を複数に分割し、各鍔状部材片と、隣接する鍔状部材片ならびに磁極片16aとの間に電気抵抗の大きい材料を配置するか、あるいはそれぞれに空隙を形成するかして絶縁を図ってもよい。あるいは、鍔状部材34として、樹脂、セラミックス等の電気抵抗の大きい材料を用いることが好ましい。後述する、補強材38、カバー部材40、プレート状部材42,44およびリング部材46についても同様に、このような厚み、材料で構成される。   The bowl-shaped member 34 has a thickness of about 4 mm to 10 mm, and is preferably a nonmagnetic metal such as aluminum or stainless steel. Such a nonmagnetic metal has excellent strength and does not affect the magnetic field generated in the magnetic field generator 10. Further, when emphasizing suppression of the eddy current, the hook-shaped member 34 made of nonmagnetic metal is divided into a plurality of pieces, and an electric wire is provided between each hook-shaped member piece and the adjacent hook-shaped member piece and the pole piece 16a. Insulation may be achieved by disposing a material having high resistance or by forming a gap in each. Alternatively, it is preferable to use a material having a large electrical resistance, such as resin or ceramic, as the bowl-shaped member 34. The reinforcing material 38, the cover member 40, the plate-like members 42 and 44, and the ring member 46, which will be described later, are similarly configured with such thickness and material.

このような磁界発生装置10によれば、外的衝撃等によって永久磁石20の接着部分に設計値を超える負荷がかかった場合においても、鍔状部材34が永久磁石20を空隙側表面18aから保持し、永久磁石20が隣接する永久磁石20や板状継鉄12a,12bから分離することを防ぐことができる。このように永久磁石20を、接着剤による固定に加えて鍔状部材34で固定することによって、磁界発生装置10を長期間安定使用できる。   According to such a magnetic field generator 10, even when a load exceeding the design value is applied to the bonded portion of the permanent magnet 20 due to an external impact or the like, the bowl-shaped member 34 holds the permanent magnet 20 from the air gap side surface 18a. In addition, it is possible to prevent the permanent magnet 20 from being separated from the adjacent permanent magnet 20 and the plate yokes 12a and 12b. Thus, by fixing the permanent magnet 20 with the hook-shaped member 34 in addition to fixing with the adhesive, the magnetic field generator 10 can be used stably for a long period of time.

また、鍔状部材34を磁極片16a,16bの外周面に取り付けることによって、永久磁石群14a,14bが配置される板状継鉄12a,12b表面にスペースがなくても、永久磁石固定用部材を用いることが可能となる。   Further, by attaching the flange-shaped member 34 to the outer peripheral surfaces of the magnetic pole pieces 16a and 16b, the permanent magnet fixing member can be used even if there is no space on the surface of the plate yokes 12a and 12b on which the permanent magnet groups 14a and 14b are arranged. Can be used.

さらに、鍔状部材34を用いれば、従来と比較して磁界発生装置に永久磁石固定用部材を簡単に(少ない工程で)取り付けることができる。鍔状部材34を磁極片16a,16bに予め取り付けておくことによって、組立の工程数を一層少なくできる。   Furthermore, if the hook-shaped member 34 is used, the permanent magnet fixing member can be attached to the magnetic field generator more easily (with fewer steps) than in the past. By attaching the hook-shaped member 34 to the magnetic pole pieces 16a and 16b in advance, the number of assembly steps can be further reduced.

なお、鍔状部材34の取り付け作業を次のように行ってもよい。
磁極片16a,16bの環状突起26が複数の環状突起片から構成されるときは、鍔状部材34も各環状突起片に対応して分割構造にしておき、各環状突起片に当該鍔状部材片を取り付けた後、鍔状部材片が取り付けられた環状突起片をベースプレート22上に配置し環状に組み立てていく。
In addition, you may perform the attachment operation | work of the collar-shaped member 34 as follows.
When the annular protrusions 26 of the magnetic pole pieces 16a and 16b are composed of a plurality of annular protrusion pieces, the hook-shaped member 34 is also divided in correspondence with each of the annular protrusion pieces, and the hook-shaped member is attached to each annular protrusion piece. After the pieces are attached, the annular protrusion pieces with the hook-like member pieces attached are arranged on the base plate 22 and assembled into an annular shape.

また、図4に示すように、鍔状部材34は、永久磁石群14aの突出部18における空隙側表面18aだけではなく外周面18b、さらには板状継鉄12aの上面にまで延びるように形成されてもよい。永久磁石群14b側についても同様である。   Further, as shown in FIG. 4, the flange-shaped member 34 is formed so as to extend not only to the air gap side surface 18a in the protrusion 18 of the permanent magnet group 14a but also to the outer peripheral surface 18b and further to the upper surface of the plate yoke 12a. May be. The same applies to the permanent magnet group 14b side.

ついで図5に示すように、永久磁石固定用部材として帯状部材36を用いてもよい。
帯状部材36としては、たとえば可撓性を有する金属性のベルトが用いられ、ステンレススチール等の非磁性金属が好ましい。このような非磁性金属は、優れた強度を有しかつ磁界発生装置10に発生する磁界に影響を与えない。また、うず電流の抑制を重視する場合には、ポリエステル繊維等の非金属が用いられることが望ましい。当該非金属にガラス繊維や炭素繊維を加えることによって強度をさらに向上させることができる。また、たとえば、帯状部材36の厚みは0.1mm〜1.0mm、幅は90mmとされ、突出部18の外周面18bに多層に巻回することが望ましい。さらに、帯状部材36は1本でも複数本でもよい。
Then, as shown in FIG. 5, a belt-like member 36 may be used as a permanent magnet fixing member.
As the belt-like member 36, for example, a flexible metal belt is used, and a nonmagnetic metal such as stainless steel is preferable. Such a nonmagnetic metal has excellent strength and does not affect the magnetic field generated in the magnetic field generator 10. Moreover, when importance is attached to suppression of eddy current, it is desirable to use a nonmetal such as polyester fiber. The strength can be further improved by adding glass fiber or carbon fiber to the nonmetal. Further, for example, it is desirable that the band-shaped member 36 has a thickness of 0.1 mm to 1.0 mm and a width of 90 mm, and is wound around the outer peripheral surface 18b of the protrusion 18 in multiple layers. Further, the belt-like member 36 may be one or plural.

このような帯状部材36を突出部18の外周面18bに巻回することによって、永久磁石20の固定を補強できる。
また、突出部18の外周面18bが露出しているいかなる磁界発生装置においても、突出部18の外周面18bに帯状部材36を容易に取り付けることができる。
By winding such a belt-shaped member 36 around the outer peripheral surface 18b of the protrusion 18, the fixation of the permanent magnet 20 can be reinforced.
Moreover, in any magnetic field generator in which the outer peripheral surface 18b of the protruding portion 18 is exposed, the belt-like member 36 can be easily attached to the outer peripheral surface 18b of the protruding portion 18.

なお、突出部18の外周面18bが凹凸形状の場合には、帯状部材36の固定力が及ばない永久磁石20が生じうる。したがって、図6に示すように、帯状部材36と永久磁石20(永久磁石群14a)との間に補強材38を介挿することによって、突出部18の外周部18bを構成するすべての永久磁石20を強く固定することができる。   In addition, when the outer peripheral surface 18b of the protrusion part 18 is uneven | corrugated shape, the permanent magnet 20 which the fixing force of the strip | belt-shaped member 36 does not reach can arise. Therefore, as shown in FIG. 6, all the permanent magnets constituting the outer peripheral portion 18 b of the protruding portion 18 by inserting the reinforcing member 38 between the belt-like member 36 and the permanent magnet 20 (permanent magnet group 14 a). 20 can be firmly fixed.

補強材38の形状は、帯状部材36と突出部18を構成する永久磁石20との間の隙間を埋めるような形状が好ましいが、帯状部材36が永久磁石群14aの突出部18を構成する永久磁石20を保持する力を高めることができるならば、任意の形状でよい。   The shape of the reinforcing member 38 is preferably a shape that fills the gap between the belt-like member 36 and the permanent magnet 20 that constitutes the protrusion 18, but the belt-like member 36 is a permanent that constitutes the protrusion 18 of the permanent magnet group 14 a. Any shape can be used as long as the force for holding the magnet 20 can be increased.

さらに、図7に示すように、永久磁石固定用部材としてカバー部材40が用いられてもよい。カバー部材40は、突出部18に沿った形状とされる。カバー部材40は、板状継鉄12aにねじ等で固定されることが望ましく、組立効率を考慮して、円周方向に複数分割されてもよい。   Further, as shown in FIG. 7, a cover member 40 may be used as a permanent magnet fixing member. The cover member 40 is shaped along the protrusion 18. The cover member 40 is preferably fixed to the plate yoke 12a with a screw or the like, and may be divided into a plurality of parts in the circumferential direction in consideration of assembly efficiency.

カバー部材40を用いることによって、突出部18を構成する永久磁石20のすべての面(空隙側表面18a、外周面18b)を固定することができる。カバー部材40は、突出部18の形状が単純な場合ほど容易に製造でき効果的である。   By using the cover member 40, it is possible to fix all the surfaces (the gap side surface 18 a and the outer peripheral surface 18 b) of the permanent magnet 20 that constitutes the protruding portion 18. The cover member 40 is more easily manufactured and effective as the protrusion 18 has a simple shape.

また、図8および図9(a)に示すように、永久磁石固定用部材として、突出部18の空隙側表面18aや外周面18bに、複数の永久磁石20同士を接続するプレート状部材42が取り付けられてもよい。複数の永久磁石20をプレート状部材42で接着することによって、その中の1つの永久磁石20が隣接する永久磁石20から分離するのを防止することができる。なお、プレート状部材の大きさは任意でよく、たとえば、突出部18の空隙側表面18aを一周するように当該空隙側表面18aに環状に形成されてもよい。   As shown in FIGS. 8 and 9A, a plate-like member 42 that connects the plurality of permanent magnets 20 to the air gap side surface 18a and the outer peripheral surface 18b of the protrusion 18 is provided as a permanent magnet fixing member. It may be attached. By bonding the plurality of permanent magnets 20 with the plate-like member 42, it is possible to prevent one of the permanent magnets 20 from separating from the adjacent permanent magnets 20. In addition, the magnitude | size of a plate-shaped member may be arbitrary, for example, it may be cyclically | annularly formed in the said space | gap side surface 18a so that the space | gap side surface 18a of the protrusion part 18 may wrap around.

また、図8および図9(b)に示すように、永久磁石20から板状継鉄12aの上面へと延びるたとえばL字状形状のプレート状部材44が用いられてもよい。この場合には、永久磁石20を板状継鉄12aに接続することによって永久磁石20をより強く固定でき、永久磁石20が板状継鉄12aから分離することを防ぐことができる。   Further, as shown in FIGS. 8 and 9B, for example, an L-shaped plate-like member 44 extending from the permanent magnet 20 to the upper surface of the plate yoke 12a may be used. In this case, the permanent magnet 20 can be more strongly fixed by connecting the permanent magnet 20 to the plate yoke 12a, and the permanent magnet 20 can be prevented from being separated from the plate yoke 12a.

さらに、このようなプレート状部材42,44は、突出部18の必要な箇所に容易に取り付けることができるので、永久磁石20の固定を容易に補強することができる。
磁極ユニット11b側においても同様である。
Furthermore, since such plate-like members 42 and 44 can be easily attached to a necessary portion of the protrusion 18, the fixation of the permanent magnet 20 can be easily reinforced.
The same applies to the magnetic pole unit 11b side.

上述した鍔状部材34、帯状部材36、補強材38、カバー部材40、プレート状部材42,44は、永久磁石20を、隣接する永久磁石20、板状継鉄12a,12b、あるいはそれらの両方から分離するための対策が施されていない磁界発生装置を補強する手段としても有効であり、汎用的に用いることができる。   The saddle-shaped member 34, the band-shaped member 36, the reinforcing member 38, the cover member 40, and the plate-shaped members 42 and 44 are the same as the permanent magnet 20, the adjacent permanent magnet 20, the plate yokes 12a and 12b, or both of them. It is also effective as a means for reinforcing a magnetic field generator that is not provided with a measure for separation from the device, and can be used for general purposes.

さらに、図10および図11(a)に示すように、鍔状部材34が取り付けられた突出部18を覆うようにリング部材46が配置されてもよい。
このようなリング部材46を用いることによって、永久磁石20が磁界発生装置10から脱落することを防止でき、また、永久磁石群14aを外部から保護することができる。なお、組立効率等を考慮してリング部材46は円周方向に複数分割されてもよい。
Furthermore, as shown in FIG. 10 and FIG. 11A, a ring member 46 may be disposed so as to cover the protruding portion 18 to which the flange-shaped member 34 is attached.
By using such a ring member 46, it is possible to prevent the permanent magnet 20 from falling off the magnetic field generator 10, and it is possible to protect the permanent magnet group 14a from the outside. In consideration of assembly efficiency and the like, the ring member 46 may be divided into a plurality of parts in the circumferential direction.

また、図11(b)に示すように、リング部材46の中に成形材48を充填すれば、永久磁石群14aの突出部18を構成する永久磁石20を保持する力をより一層強くすることができる。
磁極ユニット11b側についても同様である。
Moreover, as shown in FIG.11 (b), if the molding material 48 is filled in the ring member 46, the force which hold | maintains the permanent magnet 20 which comprises the protrusion part 18 of the permanent magnet group 14a will be made still stronger. Can do.
The same applies to the magnetic pole unit 11b side.

なお、成形材48は、永久磁石20の熱減磁を考慮して、硬化反応時の温度が100℃以下である必要があり、60℃以下であればより望ましく、具体的には発泡ウレタンが好ましい。発泡ウレタンは常温で硬化し、作業性、経済性という点で優れており、既存の磁界発生装置の補強等にも有効となる。   In consideration of thermal demagnetization of the permanent magnet 20, the molding material 48 needs to have a temperature during the curing reaction of 100 ° C. or lower, more preferably 60 ° C. or lower. Specifically, urethane foam is used. preferable. Urethane foam is cured at room temperature and is excellent in terms of workability and economy, and is effective for reinforcing existing magnetic field generators.

図10および図11に示すリング部材46および成形材48は、帯状部材36、補強材38、あるいはプレート状部材42,44を用いる実施形態にも適用できることはいうまでもない。   Needless to say, the ring member 46 and the molding material 48 shown in FIGS. 10 and 11 can also be applied to the embodiment using the belt-like member 36, the reinforcing material 38, or the plate-like members 42 and 44.

また、上述の実施形態では、一対の板状継鉄12a,12bおよび一つの支持継鉄28によって継鉄を形成する場合について述べたが、これに限定されず、一対の永久磁石群14a,14bを磁気的に結合するたとえばC字状の一体化された継鉄が用いられてもよい。   Moreover, although the above-mentioned embodiment described the case where a yoke is formed by a pair of plate-like yokes 12a and 12b and one supporting yoke 28, it is not limited to this, and a pair of permanent magnet groups 14a and 14b. For example, a C-shaped integrated yoke may be used.

この発明が適用されるMRI用磁界発生装置を示す概略側面図である。It is a schematic side view which shows the magnetic field generator for MRI to which this invention is applied. 永久磁石群の一例を示す斜視図である。It is a perspective view which shows an example of a permanent magnet group. 鍔状部材を取り付けた実施形態の一例を示す部分斜視図である。It is a fragmentary perspective view which shows an example of embodiment which attached the bowl-shaped member. 鍔状部材の変形例を示す図解図である。It is an illustration figure which shows the modification of a bowl-shaped member. 帯状部材を取り付けた実施形態の一例を示す部分斜視図である。It is a fragmentary perspective view which shows an example of embodiment which attached the strip | belt-shaped member. 帯状部材と突出部との間の隙間に補強材を介挿した状態を示す図解図である。It is an illustration figure which shows the state which inserted the reinforcing material in the clearance gap between a strip | belt-shaped member and a protrusion part. カバー部材を取り付けた実施形態の一例を示す部分斜視図である。It is a fragmentary perspective view which shows an example of embodiment which attached the cover member. プレート状部材を取り付けた実施形態の一例を示す部分斜視図である。It is a fragmentary perspective view which shows an example of embodiment which attached the plate-shaped member. プレート状部材を説明するための図解図である。It is an illustration figure for demonstrating a plate-shaped member. リング部材を取り付けた実施形態の一例を示す部分斜視図である。It is a fragmentary perspective view which shows an example of embodiment which attached the ring member. (a)はリング部材を取り付けた実施形態の一例を示す図解図であり、(b)はリング部材内に成形材を充填した実施形態の一例を示す図解図である。(A) is an illustration figure which shows an example of embodiment which attached the ring member, (b) is an illustration figure which shows an example of embodiment which filled the molding material in the ring member.

符号の説明Explanation of symbols

10 MRI用磁界発生装置
11a,11b 磁極ユニット
12a,12b 板状継鉄
14a,14b 永久磁石群
16a,16b 磁極片
18 突出部
18a 突出部の空隙側表面
18b 突出部の外周面
20 永久磁石
28 支持継鉄
34 鍔状部材
36 帯状部材
38 補強材
40 カバー部材
42,44 プレート状部材
46 リング部材
48 成形材
DESCRIPTION OF SYMBOLS 10 MRI magnetic field generator 11a, 11b Magnetic pole unit 12a, 12b Plate-like yoke 14a, 14b Permanent magnet group 16a, 16b Magnetic pole piece 18 Protruding part 18a Air gap side surface of protruding part 18b Outer peripheral surface of protruding part 20 Permanent magnet 28 Support Yoke 34 bowl-shaped member 36 band-shaped member 38 reinforcing material 40 cover member 42, 44 plate-shaped member 46 ring member 48 molding material

Claims (4)

それぞれ相互に接着される複数の永久磁石を含みかつ空隙を形成して対向配置される一対の永久磁石群と、前記一対の永久磁石群を磁気的に結合するための継鉄と、前記一対の永久磁石群のそれぞれの空隙側主面に設けられる一対の磁極片とを有し、前記永久磁石群が前記磁極片との接触部よりも外方に突出した突出部を有するように構成され、前記一対の磁極片間の空隙に磁界を発生させるMRI用磁界発生装置において、
前記突出部に配置される前記永久磁石が前記永久磁石群から離脱することを防止する永久磁石固定用部材を備え、
前記永久磁石固定用部材が、前記突出部を構成する複数の永久磁石のうち一部の隣接する前記永久磁石同士を接続するために前記突出部のうち前記対向配置される一対の永久磁石群の間に形成される前記空隙に臨む表面の一部または前記突出部の外周面の一部に取り付けられる非磁性金属からなるプレート状部材である、MRI用磁界発生装置。
A pair of permanent magnet groups each including a plurality of permanent magnets bonded to each other and forming an air gap; a yoke for magnetically coupling the pair of permanent magnet groups; A pair of magnetic pole pieces provided on the respective gap side principal surfaces of the permanent magnet group, and the permanent magnet group is configured to have a protruding portion protruding outward from a contact portion with the magnetic pole piece, In the magnetic field generator for MRI that generates a magnetic field in the gap between the pair of magnetic pole pieces,
A permanent magnet fixing member for preventing the permanent magnet disposed in the protruding portion from being detached from the permanent magnet group;
The permanent magnet fixing member is a pair of permanent magnets that are arranged opposite to each other in the projecting portion in order to connect a part of the permanent magnets among the plurality of permanent magnets constituting the projecting portion . A magnetic field generator for MRI, which is a plate-like member made of a non-magnetic metal that is attached to a part of a surface facing the gap formed therebetween or a part of an outer peripheral surface of the protrusion.
前記プレート状部材が前記継鉄にまで延びて固定される、請求項1に記載のMRI用磁界発生装置。   The magnetic field generator for MRI according to claim 1, wherein the plate-like member extends and is fixed to the yoke. 前記永久磁石固定用部材が設けられた前記突出部を包囲するリング部材をさらに含む、請求項1または2に記載のMRI用磁界発生装置。   The magnetic field generator for MRI according to claim 1, further comprising a ring member surrounding the protruding portion provided with the permanent magnet fixing member. 前記リング部材と前記突出部との間の空間に充填される成形材をさらに含む、請求項3に記載のMRI用磁界発生装置。   The magnetic field generator for MRI according to claim 3, further comprising a molding material filled in a space between the ring member and the protrusion.
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