JP2002325745A - Magnetic field generator - Google Patents
Magnetic field generatorInfo
- Publication number
- JP2002325745A JP2002325745A JP2002057766A JP2002057766A JP2002325745A JP 2002325745 A JP2002325745 A JP 2002325745A JP 2002057766 A JP2002057766 A JP 2002057766A JP 2002057766 A JP2002057766 A JP 2002057766A JP 2002325745 A JP2002325745 A JP 2002325745A
- Authority
- JP
- Japan
- Prior art keywords
- plate
- yoke
- magnetic field
- magnet
- field generator
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Links
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- Magnetic Resonance Imaging Apparatus (AREA)
Abstract
Description
【発明の詳細な説明】DETAILED DESCRIPTION OF THE INVENTION
【０００１】[0001]
【発明の属する技術分野】この発明は磁界発生装置に関
し、より特定的には、ＭＲＩ用の磁界発生装置に関す
る。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic field generator, and more particularly, to a magnetic field generator for MRI.
【０００２】[0002]
【従来の技術】ＭＲＩ用磁界発生装置において漏れ磁束
を低減する技術の一例が実公平５−４１５３０号に開示
されている。ここでは、板状継鉄の主面において、その
裏面側に着設してある永久磁石構成体の外周相当位置に
環状に８個のフェライト磁石からなるシールド用磁石を
配置することによって、漏れ磁束の発生が抑制される。2. Description of the Related Art An example of a technique for reducing a leakage magnetic flux in an MRI magnetic field generator is disclosed in Japanese Utility Model Publication No. Hei 5-41530. Here, on the main surface of the plate-shaped yoke, a shielding magnet consisting of eight ferrite magnets is annularly arranged at a position corresponding to the outer periphery of the permanent magnet structure attached to the back surface side, so that the leakage flux is reduced. Is suppressed.
【０００３】[0003]
【発明が解決しようとする課題】しかし、この関連技術
では、０．３Ｔ以上という高磁界を発生するＭＲＩ用磁
界発生装置において、漏れ磁束を効果的に抑制すること
は難しい。このような高磁界を発生させるＭＲＩ用磁界
発生装置を開放型に構成する場合も漏れ磁束を効果的に
抑制することは難しい。また、上述の関連技術では、シ
ールド用磁石は磁界発生装置の外側に露出しているの
で、組立中および輸送中に工具・チェーン等の磁性体を
引きつける可能性がある。このようなことが発生する
と、シールド用磁石自体が焼結体であるので吸引時にシ
ールド用磁石が破損する可能性がある。また、吸引され
てシールド用磁石に貼り付いた磁性体が大きい場合には
人力では取り外せないという問題も生じる。However, in this related technique, it is difficult to effectively suppress the leakage magnetic flux in a magnetic field generator for MRI that generates a high magnetic field of 0.3 T or more. Even when an MRI magnetic field generator that generates such a high magnetic field is configured as an open type, it is difficult to effectively suppress the leakage magnetic flux. In the related art described above, since the shielding magnet is exposed outside the magnetic field generator, there is a possibility that a magnetic body such as a tool or a chain is attracted during assembly and transportation. When such a situation occurs, the shielding magnet itself is a sintered body, so that the shielding magnet may be damaged at the time of suction. In addition, when the magnetic material that is attracted and adhered to the shielding magnet is large, there is a problem that it cannot be removed manually.
【０００４】さらに、最近のＭＲＩ用磁界発生装置は脚
部を有している。この脚部は磁性体からなり、板状継鉄
の主面にシールド用磁石を接着した後に取り付けられる
が、脚部がシールド用磁石に吸引されて作業者が危険に
さらされる場合がある。上述の弊害は、磁石重量を軽く
するため磁力の強い希土類焼結磁石をシールド用磁石に
使用した場合に顕著である。Further, recent magnetic field generators for MRI have legs. The leg is made of a magnetic material and is attached after the shield magnet is adhered to the main surface of the plate-shaped yoke. However, the leg may be attracted to the shield magnet and endanger the worker. The above-mentioned adverse effects are remarkable when a rare earth sintered magnet having a strong magnetic force is used as a shielding magnet in order to reduce the magnet weight.
【０００５】また近年、装置前方に磁界発生空間の中心
からみて連続して１５０度以上の開放部を有する磁界発
生装置が提案され普及しつつある。このような装置で
は、開放部において磁束の漏れが大きくなる。装置の軽
量化を図るために装置前方を斜面状に構成する場合や、
０．３Ｔ以上の強磁界を発生させる磁界発生装置では、
この問題はより顕著となる。装置前方の板状継鉄を厚く
すればある程度漏れ磁束は少なくなるが、連続して１５
０度以上の開放部を有する磁界発生装置では、支持構造
が不安定であり板状継鉄を厚くすることはできない。In recent years, a magnetic field generating device having an opening of 150 ° or more continuously in front of the device as viewed from the center of a magnetic field generating space has been proposed and becoming popular. In such a device, the leakage of magnetic flux increases in the open portion. When the front of the device is configured as a slope to reduce the weight of the device,
In a magnetic field generator that generates a strong magnetic field of 0.3T or more,
This problem becomes more pronounced. If the plate yoke in front of the device is made thicker, the leakage magnetic flux will be reduced to some extent.
In a magnetic field generator having an opening of 0 ° or more, the support structure is unstable, and the plate yoke cannot be thickened.
【０００６】それゆえに、この発明の主たる目的は、漏
れ磁束換言すれば磁界発生装置の外側に発生する不要な
磁界をより効果的に抑制できる、磁界発生装置を提供す
ることである。この発明の他の目的は、シールド用磁石
の破損を防止できる、磁界発生装置を提供することであ
る。この発明のその他の目的は、安全に組み立て作業を
行える、磁界発生装置を提供することである。[0006] Therefore, a main object of the present invention is to provide a magnetic field generator capable of more effectively suppressing an unnecessary magnetic field generated outside the magnetic field generator, that is, a leakage magnetic flux. It is another object of the present invention to provide a magnetic field generator capable of preventing breakage of a shielding magnet. Another object of the present invention is to provide a magnetic field generator capable of safely performing an assembling operation.
【０００７】[0007]
【課題を解決するための手段】上述の目的を達成するた
めに、請求項１に記載の磁界発生装置は、空隙を形成し
て対向配置される一対の板状継鉄、一対の板状継鉄を磁
気的に結合する２本以下の支持継鉄、一対の板状継鉄の
それぞれの対向する一方主面に配置される永久磁石、お
よび少なくとも一方の板状継鉄の他方主面の開放側前方
と後方とにそれぞれ設けられる第１のシールド用磁石と
第２のシールド用磁石とを備える。請求項２に記載の磁
界発生装置は、空隙を形成して対向配置される一対の板
状継鉄、一対の板状継鉄のそれぞれの対向する一方主面
に配置される永久磁石、少なくとも一方の板状継鉄の他
方主面に設けられるシールド用磁石、およびシールド用
磁石に設けられるカバー部材を備える。In order to achieve the above-mentioned object, a magnetic field generator according to the present invention comprises a pair of plate-like yoke and a pair of plate-like yoke which are arranged to face each other with a gap. Two or less supporting yokes that magnetically couple iron, permanent magnets disposed on one opposing main surface of each of a pair of plate yoke, and opening of the other main surface of at least one plate yoke A first shielding magnet and a second shielding magnet are provided at the front and rear sides, respectively. The magnetic field generating device according to claim 2, wherein at least one of a pair of plate-shaped yoke and a pair of plate-shaped yoke that are arranged to face each other and that is disposed on one main surface of each of the pair of plate-like yoke opposed to each other. And a cover member provided on the shield magnet provided on the other main surface of the plate-shaped yoke.
【０００８】請求項３に記載の磁界発生装置は、請求項
２に記載の磁界発生装置において、カバー部材は非磁性
部材であることを特徴とする。請求項４に記載の磁界発
生装置は、請求項３に記載の磁界発生装置において、カ
バー部材の外側表面とシールド用磁石の表面との間の距
離が２ｍｍ以上に設定されることを特徴とする。According to a third aspect of the present invention, there is provided a magnetic field generator according to the second aspect, wherein the cover member is a non-magnetic member. According to a fourth aspect of the present invention, in the magnetic field generator of the third aspect, a distance between an outer surface of the cover member and a surface of the shield magnet is set to 2 mm or more. .
【０００９】請求項５に記載の磁界発生装置は、空隙を
形成して対向配置される一対の板状継鉄、一対の板状継
鉄のそれぞれの対向する一方主面に配置される永久磁
石、少なくとも一方の板状継鉄の他方主面に設けられる
シールド用磁石、およびシールド用磁石が設けられる板
状継鉄の他方主面に形成される非磁性の脚部を備える。
請求項６に記載の磁界発生装置は、空隙を形成して対向
配置される一対の板状継鉄、一対の板状継鉄のそれぞれ
の対向する一方主面に配置される永久磁石、一対の板状
継鉄を磁気的に結合し、永久磁石間の均一磁界空間の中
心からみて連続して１５０度以上の開放角度を有する開
放部を形成するように設けられる支持継鉄、および少な
くとも一方の板状継鉄の開放部に対応する他方主面に設
けられるシールド用磁石を備える。According to a fifth aspect of the present invention, there is provided a magnetic field generator, wherein a pair of plate-like yoke and a pair of plate-like yoke are disposed to face each other with a gap therebetween, and permanent magnets are disposed on one of the opposite main surfaces of the pair of plate-like yoke. A shield magnet provided on the other main surface of at least one plate yoke, and a nonmagnetic leg formed on the other main surface of the plate yoke provided with the shield magnet.
The magnetic field generating device according to claim 6, wherein a pair of plate-shaped yoke and a pair of plate-shaped yoke that are opposed to each other by forming an air gap, a pair of permanent magnets that are arranged on one opposing main surface of each of the plate-shaped yoke, A support yoke provided to magnetically couple the plate yoke and to form an opening having an opening angle of 150 degrees or more continuously from the center of the uniform magnetic field space between the permanent magnets, and at least one of the yoke; A shield magnet is provided on the other main surface corresponding to the open portion of the plate yoke.
【００１０】請求項７に記載の磁界発生装置は、請求項
６に記載の磁界発生装置において、板状継鉄が薄くなる
ように板状継鉄の他方主面は斜面を有し、斜面にシール
ド用磁石が設けられることを特徴とする。請求項８に記
載の磁界発生装置は、請求項６または７に記載の磁界発
生装置において、均一磁界空間に０．３Ｔ以上の磁界が
発生されることを特徴とする。請求項９に記載の磁界発
生装置は、請求項１から８のいずれかに記載の磁界発生
装置において、シールド用磁石は希土類焼結磁石である
ことを特徴とする。According to a seventh aspect of the present invention, in the magnetic field generator according to the sixth aspect, the other main surface of the plate-like yoke has a slope so that the plate-like yoke becomes thinner. It is characterized in that a shielding magnet is provided. The magnetic field generator according to claim 8 is the magnetic field generator according to claim 6 or 7, wherein a magnetic field of 0.3 T or more is generated in a uniform magnetic field space. According to a ninth aspect of the present invention, in the magnetic field generator of any one of the first to eighth aspects, the shield magnet is a rare earth sintered magnet.
【００１１】請求項１に記載の磁界発生装置では、板状
継鉄の他方主面の開放側前方に第１のシールド用磁石を
設けることによって、不要な磁束が装置前方から漏れる
のを抑制できる。さらに、第２のシールド用磁石によっ
て、装置後方において発生する漏れ磁束を小さくでき
る。請求項２に記載の磁界発生装置では、カバー部材に
よってシールド用磁石が保護されるためシールド用磁石
の破損を防止できる。In the magnetic field generator according to the first aspect, the first shield magnet is provided in front of the other main surface of the plate yoke on the open side, so that unnecessary magnetic flux can be suppressed from leaking from the front of the device. . Further, the leakage magnetic flux generated behind the device can be reduced by the second shield magnet. In the magnetic field generating device according to the second aspect, since the shield magnet is protected by the cover member, damage to the shield magnet can be prevented.
【００１２】請求項３に記載の磁界発生装置では、カバ
ー部材は非磁性部材であるので、シールド用磁石によっ
て発生する磁束をショートさせることなく、漏れ磁束を
確実に低減することができる。請求項４に記載の磁界発
生装置では、カバー部材の外側表面とシールド用磁石の
表面との間の距離が２ｍｍ以上に設定されるので、磁性
部材に対するシールド用磁石の吸引力を弱めることがで
きる。したがって、磁性部材（たとえばツール）が吸着
されたときに、吸着された磁性部材をカバー部材から取
り外すことが容易となる。In the magnetic field generator according to the third aspect, since the cover member is a non-magnetic member, the leakage magnetic flux can be reliably reduced without short-circuiting the magnetic flux generated by the shielding magnet. In the magnetic field generator according to the fourth aspect, since the distance between the outer surface of the cover member and the surface of the shielding magnet is set to 2 mm or more, the attraction of the shielding magnet to the magnetic member can be reduced. . Therefore, when the magnetic member (for example, a tool) is attracted, it is easy to remove the attracted magnetic member from the cover member.
【００１３】請求項５に記載の磁界発生装置では、脚部
が非磁性体からなるので、組立作業時に脚部がシールド
用磁石に吸引されるのを防止でき、作業者が危険にさら
されることはない。開放型の磁界発生装置では開放部側
の漏れ磁束が大きいので、請求項６に記載の磁界発生装
置のように、板状継鉄のうち開放部に対応する位置にシ
ールド用磁石を設けることは効果が大きい。In the magnetic field generator according to the fifth aspect, since the legs are made of a non-magnetic material, it is possible to prevent the legs from being attracted to the shielding magnet during the assembling work, and the worker is exposed to danger. There is no. In an open-type magnetic field generating device, since the leakage magnetic flux on the open side is large, it is not possible to provide a shield magnet at a position corresponding to the open portion of the plate yoke as in the magnetic field generating device according to claim 6. Great effect.
【００１４】装置の軽量化のために板状継鉄の一部を削
った場合には漏れ磁束が大きくなるので、請求項７に記
載のように、板状継鉄の薄い部分にシールド用磁石を設
けることは効果的である。この発明は、請求項８に記載
のように、均一磁界空間に０．３Ｔ以上の磁界を発生す
る磁界発生装置に適する。このように強い磁界を発生さ
せる磁界発生装置ではより漏れ磁束が多くなるので、シ
ールド用磁石を設けることは効果的である。請求項９に
記載のように磁力が大きい希土類焼結磁石をシールド用
磁石として用い併せてスペーサーを使用することによっ
て、少量の磁石で磁気飽和を生じることなく漏れ磁束を
より有効に抑制できる。If a part of the plate yoke is cut off to reduce the weight of the device, the leakage magnetic flux becomes large. Is effective. The present invention is suitable for a magnetic field generator that generates a magnetic field of 0.3 T or more in a uniform magnetic field space. In such a magnetic field generator that generates a strong magnetic field, the amount of leakage magnetic flux increases, and thus it is effective to provide a shielding magnet. By using a rare earth sintered magnet having a large magnetic force as a shielding magnet and using a spacer as described in claim 9, a small amount of magnet can effectively suppress the leakage magnetic flux without causing magnetic saturation.
【００１５】[0015]
【発明の実施の形態】以下、この発明の実施形態につい
て図面を参照して説明する。図１ないし図４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、開放型装置であり、空隙１２を形成して対向配置さ
れる一対の板状継鉄１４ａおよび１４ｂを含む。板状継
鉄１４ａは開放側の前部１６ａと後部１８ａとを含む。
前部１６ａの上面は斜面２０ａとされ、板状継鉄１４ａ
は開放部の前方に向かって薄く形成されており、継鉄の
軽量化が図られている。同様に、板状継鉄１４ｂは開放
側の前部１６ｂと後部１８ｂとを含む。継鉄の軽量化の
ため前部１６ｂは後部１８ｂより薄く形成され、前部１
６ｂの下面は斜面２０ｂを介して後部１８ｂの下面に連
なる。Embodiments of the present invention will be described below with reference to the drawings. 1 to 4, an MRI magnetic field generator 10 according to an embodiment of the present invention will be described.
Is an open-type device, which includes a pair of plate-shaped yokes 14a and 14b that are opposed to each other while forming a gap 12. The plate-like yoke 14a includes an open front portion 16a and a rear portion 18a.
The upper surface of the front portion 16a is a slope 20a, and the plate-like yoke 14a
Is formed thinner toward the front of the opening to reduce the weight of the yoke. Similarly, the plate-like yoke 14b includes an open front portion 16b and a rear portion 18b. In order to reduce the weight of the yoke, the front part 16b is formed thinner than the rear part 18b.
The lower surface of 6b is continuous with the lower surface of the rear portion 18b via the slope 20b.
【００１６】板状継鉄１４ａおよび１４ｂのそれぞれの
対向面側には、永久磁石２２ａおよび２２ｂが配置さ
れ、永久磁石２２ａおよび２２ｂのそれぞれの対向面側
には、磁極片２４ａおよび２４ｂが固着される。そし
て、一対の板状継鉄１４ａと１４ｂとは、後部１８ａお
よび１８ｂのそれぞれの両端部間に配置される２本の柱
状の支持継鉄２６によって磁気的に結合される。板状継
鉄１４ａ、１４ｂおよび支持継鉄２６は軟鉄で構成され
る。このように開放型の磁界発生装置１０では、支持継
鉄２６は装置後方に配置される。このような構成によっ
て、図３に示すように、永久磁石２２ａおよび２２ｂ間
に均一磁界空間１２ａが形成され、矢印Ｙで示すような
磁束が発生する。このとき、図２に示すように、永久磁
石２２ａおよび２２ｂ間に形成される均一磁界空間１２
ａの中心Ｐからみて、開放部の開放角度αが連続して１
５０度以上となるように支持継鉄２６は配置される。開
放部とは、支持継鉄２６が存在しない空間をいう。Permanent magnets 22a and 22b are disposed on the opposing surfaces of the plate-shaped yokes 14a and 14b, respectively, and pole pieces 24a and 24b are fixed on the opposing surfaces of the permanent magnets 22a and 22b. You. The pair of plate yokes 14a and 14b are magnetically coupled by two columnar supporting yokes 26 disposed between both ends of the rear portions 18a and 18b. The plate yoke 14a, 14b and the support yoke 26 are made of soft iron. As described above, in the open type magnetic field generator 10, the support yoke 26 is disposed at the rear of the device. With such a configuration, as shown in FIG. 3, a uniform magnetic field space 12a is formed between the permanent magnets 22a and 22b, and a magnetic flux as indicated by an arrow Y is generated. At this time, as shown in FIG. 2, a uniform magnetic field space 12 formed between the permanent magnets 22a and 22b is formed.
When viewed from the center P of a, the open angle α of the open portion is continuously 1
The supporting yoke 26 is arranged so as to be 50 degrees or more. The open portion refers to a space where the supporting yoke 26 does not exist.
【００１７】また、板状継鉄１４ａの後部１８ａ上面に
は、対称的に２つの長方形角板状のスぺーサー２８が配
置され、スぺーサー２８上には略正方形角板状のシール
ド用磁石３０が配置される。換言すれば、２つのシール
ド用磁石３０が板状継鉄１４ａの上面の後方に設けられ
る。図２からわかるように、板状継鉄１４ａ上において
各シールド用磁石３０は、その一部３０ａが永久磁石２
２ａの外周縁Ａ１（裏面側に形成）からはみ出しかつ支
持継鉄２６に重ならずギャップＧを形成するように配置
される。図３に矢印Ｂで示すように支持継鉄２６は磁路
となり、板状継鉄１４ａと支持継鉄２６との結合部分に
磁束が集中するので、ギャップＧに位置する板状継鉄１
４ａの部分は磁気飽和しやすい。このように磁気飽和し
やすい領域を避けてシールド用磁石３０を配置すること
によって、磁気飽和を促進することなく漏れ磁束を抑制
でき、空隙１２中心部における磁界強度を確保できる。On the upper surface of the rear portion 18a of the plate-shaped yoke 14a, two rectangular square plate-like spacers 28 are symmetrically arranged. A magnet 30 is arranged. In other words, two shield magnets 30 are provided behind the upper surface of the plate yoke 14a. As can be seen from FIG. 2, each of the shielding magnets 30 on the plate-like yoke 14a has a portion 30a
It is arranged so as to protrude from the outer peripheral edge A1 (formed on the back side) of 2a and not to overlap with the supporting yoke 26 to form the gap G. As shown by an arrow B in FIG. 3, the support yoke 26 forms a magnetic path, and the magnetic flux concentrates on a joint portion between the plate yoke 14 a and the support yoke 26.
The portion 4a is easily magnetically saturated. By arranging the shield magnet 30 in such a manner as to avoid the region where magnetic saturation is likely to occur, the leakage magnetic flux can be suppressed without promoting magnetic saturation, and the magnetic field intensity at the center of the gap 12 can be secured.
【００１８】さらに、板状継鉄１４ａの前部１６ａ上面
の斜面２０ａには、長方形角板状のスぺーサー３２が配
置され、スぺーサー３２上には長方形角板状のシールド
用磁石３４が配置される。換言すれば、シールド用磁石
３４が板状継鉄１４ａの上面の開放側前方に設けられ
る。一般に、開放型の磁界発生装置１０では開放部側の
漏れ磁束が大きい。そこで、このように装置の前部１６
ａにシールド用磁石３４を配置することによって漏れ磁
束をさらに抑制できる。Further, a rectangular square plate-shaped spacer 32 is disposed on the slope 20a on the upper surface of the front portion 16a of the plate-shaped yoke 14a, and the rectangular square plate-shaped shielding magnet 34 is placed on the spacer 32. Is arranged. In other words, the shield magnet 34 is provided in front of the upper surface of the plate-shaped yoke 14a on the open side. Generally, in the open type magnetic field generator 10, the leakage magnetic flux on the open side is large. Therefore, as described above, the front part 16 of the device is used.
By arranging the shielding magnet 34 in a, the leakage magnetic flux can be further suppressed.
【００１９】スぺーサー２８および３２の厚みはたとえ
ば３０ｍｍであり電磁軟鉄で構成される。シールド用磁
石３０および３４は、たとえば略３５×５０×５０ｍｍ
の直方体状の磁石単体を組み立て、漏れ磁束の方向と逆
方向の磁化を有するように形成される。シールド用磁石
３０および３４に用いる磁石としては、ネオジム焼結磁
石（Ｒ−Ｆｅ−Ｂ系焼結磁石）、サマリウムコバルト磁
石、アルニコ磁石、フェライト磁石を使用できる。これ
らのうちフェライト磁石は重量がかさみかつ輸送中に−
２０℃程度の低温で減磁が発生する可能性がある。高い
エネルギー積を有する磁石を使用すれば高いシールド効
果を得ることができ、また、磁石を薄くし装置を小型化
することも必要であるため、希土類焼結磁石を使用する
ことが望ましい。保磁力としては通常１０００ｋＡ／ｍ
以上あればよいが、輸送時に高温になる場合、さらに高
い保磁力の材料が望ましい。永久磁石２２ａ、２２ｂと
してはたとえば住友特殊金属社製のＮＥＯＭＡＸ−４
７、シールド用磁石３０、３４としては同じくたとえば
住友特殊金属社製のＮＥＯＭＡＸ−３９ＳＨ等が使用さ
れる。Ｒ−Ｆｅ−Ｂ系焼結磁石については米国特許第
４，７７０，７２３号や第４，７９２，３６８号に開示
されている。The spacers 28 and 32 have a thickness of, for example, 30 mm and are made of soft magnetic iron. The shielding magnets 30 and 34 are, for example, approximately 35 × 50 × 50 mm
Are assembled so as to have a magnetization in the direction opposite to the direction of the leakage magnetic flux. Neodymium sintered magnets (R-Fe-B based sintered magnets), samarium cobalt magnets, alnico magnets, and ferrite magnets can be used as the magnets used for the shielding magnets 30 and 34. Of these, ferrite magnets are heavy and
Demagnetization may occur at a low temperature of about 20 ° C. If a magnet having a high energy product is used, a high shielding effect can be obtained, and it is necessary to reduce the thickness of the magnet and the size of the device, so that it is desirable to use a rare earth sintered magnet. The coercive force is usually 1000 kA / m
If the temperature becomes high during transportation, a material having a higher coercive force is desirable. As the permanent magnets 22a and 22b, for example, NEOMAX-4 manufactured by Sumitomo Special Metals Co., Ltd.
7, For example, NEOMAX-39SH manufactured by Sumitomo Special Metals Co., Ltd. is used as the shielding magnets 30 and 34. R-Fe-B based sintered magnets are disclosed in U.S. Pat. Nos. 4,770,723 and 4,792,368.
【００２０】なお、図４に示すように、スペーサー２８
はスペーサー取付ねじ３６によって板状継鉄１４ａに固
定され、スペーサー２８およびシールド用磁石３０はカ
バー部材３８によって覆われる。カバー部材３８はたと
えばＳＵＳ３０４などからなる非磁性部材からなり、カ
バー取付ねじ４０によって板状継鉄１４ａの後部１８ａ
上面に取り付けられる。また、スペーサー３２はスペー
サー取付ねじ４２によって固定され、スペーサー３２お
よびシールド用磁石３４はカバー部材４４によって覆わ
れる。カバー部材４４もたとえばＳＵＳ３０４（ステン
レス鋼）などからなる非磁性部材からなり、カバー取付
ねじ４６によって板状継鉄１４ａの前部１６ａの斜面２
０ａ上に取り付けられる。シールド用磁石３０、３４は
複数の磁石単体からなり、各磁石単体は、スペーサー２
８、３２上に同極を隣接させて接着されている。したが
って、接着が外れたときには磁石単体が反発力で飛び出
すおそれがあるが、カバー部材３８、４４はこれを防止
している。このとき、カバー部材３８の外側表面とシー
ルド用磁石３０の表面との間の距離Ｔ１、およびカバー
部材４４の外側表面とシールド用磁石３４の表面との間
の距離Ｔ２は、それぞれ２ｍｍ以上に設定される。Incidentally, as shown in FIG.
Is fixed to the plate-like yoke 14 a by a spacer mounting screw 36, and the spacer 28 and the shielding magnet 30 are covered by a cover member 38. The cover member 38 is made of a non-magnetic member made of, for example, SUS304 or the like.
Mounted on top. The spacer 32 is fixed by spacer mounting screws 42, and the spacer 32 and the shielding magnet 34 are covered by a cover member 44. The cover member 44 is also made of a non-magnetic member made of, for example, SUS304 (stainless steel) or the like.
0a. Each of the shielding magnets 30 and 34 is composed of a plurality of magnets, and each of the magnets is a spacer 2.
The same poles are adhered on 8 and 32 with the same poles adjacent to each other. Therefore, when the adhesion is released, there is a possibility that the magnet alone may fly out due to the repulsive force, but the cover members 38 and 44 prevent this. At this time, the distance T1 between the outer surface of the cover member 38 and the surface of the shielding magnet 30 and the distance T2 between the outer surface of the cover member 44 and the surface of the shielding magnet 34 are each set to 2 mm or more. Is done.
【００２１】図５に示すように、板状継鉄１４ｂ側につ
いても同様、板状継鉄１４ｂの後部１８ｂの下面に、対
称的に２つのスぺーサー２８が配置され、スぺーサー２
８上にシールド用磁石３０が配置される。換言すれば、
２つのシールド用磁石３０が板状継鉄１４ｂの下面の後
方に設けられる。図５からわかるように、板状継鉄１４
ｂ上において各シールド用磁石３０は、その一部３０ａ
が永久磁石２２ｂの外周縁Ａ２からはみ出しかつ支持継
鉄２６に重ならずギャップＧを形成するように配置され
る。また、板状継鉄１４ｂの前部１６ｂ下面のうちの平
坦面には、スぺーサー３２が配置され、スぺーサー３２
上にシールド用磁石３４が配置される。換言すれば、シ
ールド用磁石３４が板状継鉄１４ｂの下面の開放側前方
に設けられる。なお、板状継鉄１４ｂ側においても、図
４に示す板状継鉄１４ａの場合と同様に、カバー部材に
よって、スぺーサー２８およびシールド用磁石３０、ス
ぺーサー３２およびシールド用磁石３４が覆われ、各部
材が固定される。As shown in FIG. 5, similarly, on the plate yoke 14b side, two spacers 28 are symmetrically arranged on the lower surface of the rear portion 18b of the plate yoke 14b.
The shielding magnet 30 is arranged on the upper surface 8. In other words,
Two shield magnets 30 are provided behind the lower surface of the plate yoke 14b. As can be seen from FIG.
b, each shielding magnet 30 has a portion 30a
Are arranged so as to protrude from the outer peripheral edge A2 of the permanent magnet 22b and not to overlap the supporting yoke 26 to form the gap G. A spacer 32 is arranged on a flat surface of the lower surface of the front portion 16b of the plate-like yoke 14b.
The shielding magnet 34 is disposed on the upper side. In other words, the shielding magnet 34 is provided in front of the lower surface of the plate-like yoke 14b on the open side. In addition, also on the plate-like yoke 14b side, similarly to the case of the plate-like yoke 14a shown in FIG. 4, the spacer 28 and the shield magnet 30, the spacer 32 and the shield magnet 34 are formed by the cover member. It is covered and each member is fixed.
【００２２】上述のように、シールド用磁石３０および
３４がそれぞれカバー部材３８および４４によって保護
されるため、シールド用磁石３０および３４の破損を防
止できる。また、カバー部材３８および４４は非磁性部
材であるので、シールド用磁石３０および３４によって
発生する磁束をショートさせることも遮蔽することもな
く、漏れ磁束を確実に低減することができる。さらに、
距離Ｔ１およびＴ２が２ｍｍ以上に設定されるので、た
とえ磁性部材がシールド用磁石３０、３４に吸引されて
もその吸引力を弱めることができ、吸着された磁性部材
をカバー部材３８、４４から取り外すことが容易とな
る。As described above, since the shielding magnets 30 and 34 are protected by the cover members 38 and 44, respectively, damage to the shielding magnets 30 and 34 can be prevented. Further, since the cover members 38 and 44 are non-magnetic members, the magnetic flux generated by the shielding magnets 30 and 34 is not short-circuited or shielded, so that the leakage magnetic flux can be surely reduced. further,
Since the distances T1 and T2 are set to 2 mm or more, even if the magnetic member is attracted by the shielding magnets 30, 34, the attractive force can be weakened, and the attracted magnetic member is removed from the cover members 38, 44. It becomes easier.
【００２３】板状継鉄１４ｂの下面には、２本の支持継
鉄２６に対応する位置にそれぞれ脚部４８が取り付けら
れ、板状継鉄１４ｂの前部１６ｂ下面のうちの平坦部に
は２本の脚部５０が取り付けられる。脚部４８および５
０は非磁性体からなる。これによって、組立作業時に脚
部４８および５０がシールド用磁石３０や３４に吸引さ
れるのを防止でき、作業者が危険にさらされることはな
い。磁界発生装置１０において、スぺーサー２８、シー
ルド用磁石３０およびカバー部材３８は次のようにして
板状継鉄１４ａに取り付けられる。Legs 48 are attached to the lower surface of the plate yoke 14b at positions corresponding to the two support yokes 26, respectively. Two legs 50 are attached. Legs 48 and 5
0 is made of a non-magnetic material. As a result, the legs 48 and 50 can be prevented from being attracted to the shielding magnets 30 and 34 during the assembling operation, and the operator is not put at risk. In the magnetic field generator 10, the spacer 28, the shielding magnet 30, and the cover member 38 are attached to the plate yoke 14a as follows.
【００２４】図６を参照して、まず、板状継鉄１４ａの
両端部が支持台５２によって支持され、板状継鉄１４ａ
上の所定箇所に４本の案内棒５４が立設される。そし
て、スぺーサー２８上の所定の位置にシールド用磁石３
０が接着剤等で固定され、この状態のスぺーサー２８が
クレーン等によってつり上げられて板状継鉄１４ａ上に
運ばれ、スぺーサー２８の各孔５６に案内棒５４が挿入
されてスぺーサー２８が降下される。これによってスぺ
ーサー２８およびシールド用磁石３０が板状継鉄１４ａ
上の所定の位置に配置される。その後、案内棒５４が取
り外され、その代わりにスペーサー取付ねじ３６が螺入
されてスぺーサー２８が板状継鉄１４ａ上に固定され
る。そして、固定されたスぺーサー２８およびシールド
用磁石３０上にカバー部材３８が被せられ、カバー部材
３８がカバー取付ねじ４０によって板状継鉄１４ａに取
り付けられる。スぺーサー３４、シールド用磁石３６お
よびカバー部材４４についても同様である。また、板状
継鉄１４ｂの下面についても同様にスぺーサー３０およ
び３４、シールド用磁石３２および３６、カバー部材３
８および４４が取り付けられる。Referring to FIG. 6, first, both ends of plate yoke 14a are supported by support base 52, and plate yoke 14a
Four guide bars 54 are erected at predetermined upper positions. The shield magnet 3 is placed at a predetermined position on the spacer 28.
The spacer 28 is fixed by an adhesive or the like, and the spacer 28 in this state is lifted by a crane or the like and carried on the plate-like yoke 14a. The spacer 28 is lowered. As a result, the spacer 28 and the shielding magnet 30 are connected to the plate yoke 14a.
It is arranged at a predetermined position above. Thereafter, the guide rod 54 is removed, and instead, the spacer mounting screw 36 is screwed in, and the spacer 28 is fixed on the plate-like yoke 14a. Then, the cover member 38 is put on the fixed spacer 28 and the shield magnet 30, and the cover member 38 is attached to the plate yoke 14 a by the cover attaching screw 40. The same applies to the spacer 34, the shielding magnet 36, and the cover member 44. Similarly, the lower surface of the plate-like yoke 14b is also provided with spacers 30 and 34, shielding magnets 32 and 36,
8 and 44 are attached.
【００２５】このような磁界発生装置１０の一実験例に
ついて説明する。図７に示すからの各場合につい
て、均一磁界空間１２ａの中心Ｐにおける磁界強度と、
均一磁界空間１２ａの中心Ｐから板状継鉄１４ａの中心
上方で磁界が１ｍＴとなる位置までの距離（磁界１ｍＴ
ライン）とを測定した。磁界１ｍＴラインまでの距離が
小さければ漏れ磁束が少ないことを意味する。ここで
は、図１〜図３、図５に示す板状継鉄１４ａおよび１４
ｂの各３箇所に、からの各場合に応じてスぺーサー
やシールド用磁石を取り付けて実験した。An experimental example of such a magnetic field generator 10 will be described. For each case shown in FIG. 7, the magnetic field strength at the center P of the uniform magnetic field space 12a is:
Distance from the center P of the uniform magnetic field space 12a to a position above the center of the plate yoke 14a where the magnetic field is 1 mT (magnetic field 1 mT
Line). If the distance to the magnetic field 1 mT line is small, it means that the leakage magnetic flux is small. Here, the plate yokes 14a and 14 shown in FIGS.
The experiment was conducted by attaching a spacer or a magnet for shielding to each of the three places b.
【００２６】取り付け部材すなわちスぺーサーおよび
シールド用磁石を取り付けない場合には、図８（ａ）に
示すように板状継鉄１４ａ中を磁束が流れ、図７に示す
ような結果が得られた。When the mounting member, that is, the spacer and the shielding magnet are not mounted, the magnetic flux flows in the plate yoke 14a as shown in FIG. 8A, and the result shown in FIG. 7 is obtained. Was.
【００２７】板状継鉄１４ａおよび１４ｂに鉄からな
るスぺーサー２８および３２のみを取り付けた場合に
は、図８（ｂ）に示すように実質的に板状継鉄１４ａお
よび１４ｂの厚みが増すため磁界強度が向上するもの
の、漏れ磁束はわずかしか少なくならなかった。When only spacers 28 and 32 made of iron are attached to plate-like yokes 14a and 14b, the thickness of plate-like yokes 14a and 14b is substantially reduced as shown in FIG. Although the magnetic field strength was improved due to the increase, the leakage magnetic flux was only slightly reduced.
【００２８】板状継鉄１４ａおよび１４ｂにシールド
用磁石３０および３４を直接貼り付けた場合には、漏れ
磁束は少なくなるものの、図８（ｃ）に示すようにシー
ルド用磁石３０および３４自身が発生する磁束により板
状継鉄１４ａおよび１４ｂが部分的に磁気飽和すること
によって、部分的に透磁率が低くなり、均一磁界空間１
２ａの中心Ｐにおける磁界強度が低下した。When the shielding magnets 30 and 34 are directly adhered to the plate yokes 14a and 14b, the leakage magnetic flux is reduced, but as shown in FIG. Due to the magnetic flux generated, the plate-shaped yokes 14a and 14b are partially magnetically saturated, so that the magnetic permeability is partially reduced and the uniform magnetic field space 1 is reduced.
The magnetic field strength at the center P of 2a decreased.
【００２９】シールド用磁石３０および３４を非磁性
部材（ＳＵＳ３０４）からなるスぺーサー２８および３
２に装着して、板状継鉄１４ａおよび１４ｂに取り付け
る場合には、シールド用磁石３０および３４は板状継鉄
１４ａおよび１４ｂから遠ざけられる。したがって、
の場合より、漏れ磁束は若干増えるものの、図８（ｄ）
に示すようにシールド用磁石３０および３４自身が発生
する磁束が板状継鉄１４ａおよび１４ｂの磁気抵抗に影
響を与えないので、板状継鉄１４ａおよび１４ｂにおけ
る磁気飽和を抑制して、その分だけ均一磁界空間１２ａ
の中心Ｐにおける磁界強度が向上した。ただし、シール
ド用磁石３０および３４によって発生する磁束の一部は
板状継鉄１４ａおよび１４ｂに流れてしまう。The shield magnets 30 and 34 are made of spacers 28 and 3 made of a non-magnetic member (SUS304).
2 and attached to the plate yokes 14a and 14b, the shielding magnets 30 and 34 are kept away from the plate yokes 14a and 14b. Therefore,
Although the leakage magnetic flux slightly increases as compared with the case of FIG.
Since the magnetic fluxes generated by the shielding magnets 30 and 34 themselves do not affect the magnetic resistance of the plate yoke 14a and 14b, as shown in FIG. Only uniform magnetic field space 12a
, The magnetic field strength at the center P was improved. However, a part of the magnetic flux generated by the shielding magnets 30 and 34 flows to the plate yokes 14a and 14b.
【００３０】シールド用磁石３０および３４を鉄から
なるスぺーサー２８および３２に装着して、板状継鉄１
４ａおよび１４ｂに取り付ける場合には、図８（ｅ）に
示すようにシールド用磁石３０および３４が発生する磁
束が主にスペーサー２８および３２中を通り板状継鉄１
４ａおよび１４ｂの磁気抵抗に影響を与えず、さらにス
ぺーサー２８および３２が鉄からなるので実質的に板状
継鉄１４ａおよび１４ｂの厚みが増すため、磁気飽和を
抑制して磁界強度を向上でき、かつ漏れ磁束を少なくで
きた。The shield magnets 30 and 34 are mounted on spacers 28 and 32 made of iron, and
8a, the magnetic fluxes generated by the shielding magnets 30 and 34 pass mainly through the spacers 28 and 32, as shown in FIG.
Since the spacers 28 and 32 are made of iron, the thickness of the plate-shaped yokes 14a and 14b is substantially increased without affecting the magnetic resistance of the 4a and 14b, thereby suppressing magnetic saturation and improving the magnetic field strength. And reduced leakage flux.
【００３１】したがって、磁界発生装置１０によれば、
スぺーサー２８および３２を設けることによって板状継
鉄１４ａおよび１４ｂからそれぞれシールド用磁石３０
および３４を遠ざけることができるので、板状継鉄１４
ａおよび１４ｂの磁気飽和を緩和でき、空隙１２の磁界
強度を向上できる。さらに、スぺーサー２８および３２
が鉄などの磁性部材からなるときには漏れ磁束を少なく
することができる。特に、磁界発生装置１０のように開
放型の磁界発生装置では、磁束が継鉄の結合部分におい
て局所的に集中する傾向がありその部分で磁気飽和が発
生しやすくなるため、この発明は効果的である。また、
磁力が大きい希土類焼結磁石をシールド用磁石３０およ
び３４として用いあわせてスペーサ２８および３２を使
用することによって、少量の磁石で磁気飽和を生じるこ
となく漏れ磁束をより有効に抑制できる。Therefore, according to the magnetic field generator 10,
By providing the spacers 28 and 32, the shielding magnets 30
And 34 can be kept away from each other,
The magnetic saturation of a and 14b can be reduced, and the magnetic field strength of the air gap 12 can be improved. In addition, spacers 28 and 32
Is made of a magnetic material such as iron, the leakage magnetic flux can be reduced. In particular, in an open type magnetic field generating device such as the magnetic field generating device 10, the magnetic flux tends to be locally concentrated at a joint portion of the yoke, and magnetic saturation is easily generated at that portion. It is. Also,
By using the rare earth sintered magnet having a large magnetic force as the shielding magnets 30 and 34 and using the spacers 28 and 32, the leakage magnetic flux can be more effectively suppressed with a small amount of magnet without causing magnetic saturation.
【００３２】板状継鉄１４ａおよび１４ｂ上にそれぞれ
シールド用磁石３０および３４を直接取り付けようとす
れば、板状継鉄１４ａおよび１４ｂとシールド用磁石３
０および３４との間に強い吸引力が発生し、シールド用
磁石３０および３４を精度よくかつ安全に所定の位置に
配置するのが難しくなる。しかし、磁界発生装置１０で
は、スぺーサー２８および３２にシールド用磁石３０お
よび３４を予め取り付けておき、その状態でスぺーサー
２８および３２を板状継鉄１４ａおよび１４ｂの主面に
取り付けるので、スぺーサー２８および３２上の所定の
位置にシールド用磁石３０および３４を容易に配置で
き、磁界発生装置１０を安全に組み立てることができ
る。シールド用磁石３０および３４として希土類焼結磁
石を用いるとき、より効果的である。If the shield magnets 30 and 34 are to be directly mounted on the plate yoke 14a and 14b, respectively, the plate yoke 14a and 14b and the shield magnet 3
A strong attractive force is generated between the shield magnets 0 and 34, which makes it difficult to accurately and safely arrange the shielding magnets 30 and 34 at predetermined positions. However, in the magnetic field generator 10, the shield magnets 30 and 34 are attached to the spacers 28 and 32 in advance, and the spacers 28 and 32 are attached to the main surfaces of the plate yokes 14a and 14b in that state. The shield magnets 30 and 34 can be easily arranged at predetermined positions on the spacers 28 and 32, and the magnetic field generator 10 can be safely assembled. It is more effective when a rare earth sintered magnet is used as the shielding magnets 30 and 34.
【００３３】一般に、板状継鉄の厚みを大きくすれば漏
れ磁束は減少するが、たとえば０．３５Ｔの磁界を発生
させようとすれば板状継鉄の厚みは３０ｃｍにもなる。
このとき、磁界発生装置は略２０トンになり、床の強度
が要求されるので、設置場所が制約されるとともに、運
搬も大変になる。したがって、板状継鉄の厚みをこれ以
上増加させることはできない。そのため、板状継鉄の厚
みは磁束が飽和しない程度に薄く設定される。たとえ
ば、磁界発生装置１０のように、装置の軽量化のために
板状継鉄１４ａおよび１４ｂのそれぞれの前部１６ａお
よび１６ｂが薄く形成される。この場合、磁束が集中す
る領域ではどうしても継鉄が磁気飽和して磁束が漏れて
しまう。そこで、磁界発生装置１０では、板状継鉄１４
ａおよび１４ｂの薄い箇所等、必要な箇所にスぺーサ部
材２８および３２を介してそれぞれシールド用磁石３０
および３４を配置することによって、板状継鉄１４ａお
よび１４ｂ自体の厚みを大きくすることなく磁界発生装
置１０の軽量化を図りつつ、漏れ磁束を抑えることがで
きる。特に、この発明は、均一磁界空間１２ａに０．３
Ｔ以上の強い磁界を発生する磁界発生装置に適する。In general, the leakage magnetic flux is reduced by increasing the thickness of the plate yoke, but the thickness of the plate yoke becomes as large as 30 cm if a magnetic field of 0.35 T is to be generated.
At this time, the magnetic field generator is about 20 tons, and the floor strength is required, so that the installation place is restricted and the transportation becomes difficult. Therefore, the thickness of the plate yoke cannot be further increased. Therefore, the thickness of the plate-like yoke is set so thin that the magnetic flux is not saturated. For example, like the magnetic field generator 10, the front portions 16a and 16b of the plate yokes 14a and 14b are formed thinner to reduce the weight of the device. In this case, in the region where the magnetic flux is concentrated, the yoke is magnetically saturated and the magnetic flux leaks. Thus, in the magnetic field generator 10, the plate yoke 14
The shield magnets 30 are provided via spacer members 28 and 32 at necessary places such as the thin places of a and 14b.
By disposing the and 34, it is possible to reduce the magnetic flux leakage while reducing the weight of the magnetic field generator 10 without increasing the thickness of the plate yokes 14a and 14b themselves. In particular, the present invention provides a uniform magnetic field space 12a with 0.3
It is suitable for a magnetic field generator that generates a strong magnetic field of T or more.
【００３４】さらに、ＭＲＩ装置は病院内に設置される
ので、漏れ磁束が多いと病院内の電子機器が誤作動する
可能性がある。また、ペースメーカを装着している人が
強磁界領域に立ち入るとペースメーカが誤作動を起こす
可能性がある。したがって、０．５ｍＴ以上の磁界が発
生する領域を狭い領域に制限するには、大がかりな磁気
シールド工事が必要となり、あるいは広い設置スペース
が必要になる。しかし、この発明によれば漏れ磁束を少
なくできるので、上述の問題点を改善できる。Further, since the MRI apparatus is installed in a hospital, if there is a large amount of magnetic flux leakage, electronic equipment in the hospital may malfunction. Also, if a person wearing a pacemaker enters the strong magnetic field region, the pacemaker may malfunction. Therefore, in order to limit the region where a magnetic field of 0.5 mT or more is generated to a narrow region, a large-scale magnetic shield work is required or a large installation space is required. However, according to the present invention, since the leakage magnetic flux can be reduced, the above problem can be solved.
【００３５】なお、スペーサーおよびシールド用磁石
は、板状継鉄１４ａおよび１４ｂのいずれか一方にのみ
設けられてもよい。また、この発明は、１本の支持継鉄
や４本の支持継鉄を用いた磁界発生装置にも適用でき、
たとえば、特開２０００−１３９８７４号に示されるよ
うな磁界発生装置にも適用できる。The spacer and the shielding magnet may be provided only on one of the plate yokes 14a and 14b. Also, the present invention can be applied to a magnetic field generator using one support yoke or four support yoke,
For example, the present invention can be applied to a magnetic field generator as disclosed in JP-A-2000-139874.
【００３６】[0036]
【発明の効果】この発明によれば、板状継鉄の磁気飽和
を緩和でき、一対の板状継鉄間の空隙の磁界強度を低下
させることなく漏れ磁束を少なくすることができる。ま
た、カバー部材を用いることによってシールド用磁石の
破損を防止でき、脚部を非磁性体で構成することによっ
て、組立作業時に脚部がシールド用磁石に吸引されるの
を防止でき、磁界発生装置を安全に組み立てることがで
きる。According to the present invention, the magnetic saturation of the plate yoke can be reduced, and the leakage magnetic flux can be reduced without lowering the magnetic field strength of the gap between the pair of plate yoke. In addition, the use of the cover member can prevent breakage of the shield magnet, and the legs can be prevented from being attracted to the shield magnet during assembly work by forming the legs from a non-magnetic material. Can be assembled safely.
【図１】この発明の一実施形態を示す斜視図である。FIG. 1 is a perspective view showing an embodiment of the present invention.
【図２】この発明の一実施形態を示す平面図である。FIG. 2 is a plan view showing an embodiment of the present invention.
【図３】この発明の一実施形態を示す正面図である。FIG. 3 is a front view showing an embodiment of the present invention.
【図４】カバー部材を取り付けた状態を示す図解図であ
る。FIG. 4 is an illustrative view showing a state where a cover member is attached;
【図５】この発明の一実施形態を示す底面図である。FIG. 5 is a bottom view showing one embodiment of the present invention.
【図６】シールド用磁石およびスぺーサーの組立方法の
一例を示す図解図である。FIG. 6 is an illustrative view showing one example of a method for assembling a shield magnet and a spacer;
【図７】実験結果を示すテーブルである。FIG. 7 is a table showing experimental results.
【図８】実験結果を説明するための図解図である。FIG. 8 is an illustrative view for explaining an experimental result;
１０ 磁界発生装置 １２ 空隙 １２ａ 均一磁界空間 １４ａ、１４ｂ 板状継鉄 １６ａ、１６ｂ 板状継鉄の前部 １８ａ、１８ｂ 板状継鉄の後部 ２０ａ、２０ｂ 板状継鉄の斜面 ２２ａ、２２ｂ 永久磁石 ２４ａ、２４ｂ 磁極片 ２６ 支持継鉄 ２８、３２ スペーサー ３０、３４ シールド用磁石 ３８、４４ カバー部材 ４８、５０ 脚部 Ｐ 均一磁界空間の中心 α 開放角度 Ｔ１、Ｔ２ カバー部材の外側表面とシールド用磁
石の表面との間の距離DESCRIPTION OF SYMBOLS 10 Magnetic field generator 12 Air gap 12a Uniform magnetic field space 14a, 14b Plate yoke 16a, 16b Front part of plate yoke 18a, 18b Rear part of plate yoke 20a, 20b Slope of plate yoke 22a, 22b Permanent magnet 24a, 24b Pole piece 26 Support yoke 28, 32 Spacer 30, 34 Shield magnet 38, 44 Cover member 48, 50 Leg P Center of uniform magnetic field space α Open angle T1, T2 Outside surface of cover member and shield magnet Distance from the surface
Claims (9)
状継鉄、 前記一対の板状継鉄を磁気的に結合する２本以下の支持
継鉄、 前記一対の板状継鉄のそれぞれの対向する一方主面に配
置される永久磁石、および少なくとも一方の前記板状継
鉄の他方主面の開放側前方と後方とにそれぞれ設けられ
る第１のシールド用磁石と第２のシールド用磁石とを備
える、磁界発生装置。A pair of plate yoke which are opposed to each other by forming a gap; two or less support yoke which magnetically couples the pair of plate yoke; A permanent magnet disposed on one of the opposing main surfaces, and a first shield magnet and a second shield magnet provided on an open front side and a rear side of the other main surface of at least one of the plate yoke. A magnetic field generator comprising a magnet.
状継鉄、 前記一対の板状継鉄のそれぞれの対向する一方主面に配
置される永久磁石、 少なくとも一方の前記板状継鉄の他方主面に設けられる
シールド用磁石、および前記シールド用磁石に設けられ
るカバー部材を備える、磁界発生装置。2. A pair of plate-shaped yokes arranged to face each other with an air gap formed therebetween; a permanent magnet arranged on one of the opposing main surfaces of each of the pair of plate-shaped yokes; A magnetic field generator comprising: a shield magnet provided on the other main surface of iron; and a cover member provided on the shield magnet.
求項２に記載の磁界発生装置。3. The magnetic field generator according to claim 2, wherein the cover member is a non-magnetic member.
ド用磁石の表面との間の距離が２ｍｍ以上に設定され
る、請求項３に記載の磁界発生装置。4. The magnetic field generator according to claim 3, wherein a distance between an outer surface of the cover member and a surface of the shielding magnet is set to 2 mm or more.
状継鉄、 前記一対の板状継鉄のそれぞれの対向する一方主面に配
置される永久磁石、 少なくとも一方の前記板状継鉄の他方主面に設けられる
シールド用磁石、および前記シールド用磁石が設けられ
る前記板状継鉄の前記他方主面に形成される非磁性の脚
部を備える、磁界発生装置。5. A pair of plate-shaped yokes arranged to face each other with an air gap formed therebetween; a permanent magnet arranged on one of the main surfaces of each of the pair of plate-shaped yokes facing each other; A magnetic field generator comprising: a shielding magnet provided on the other main surface of iron; and a nonmagnetic leg formed on the other main surface of the plate-like yoke provided with the shielding magnet.
状継鉄、 前記一対の板状継鉄のそれぞれの対向する一方主面に配
置される永久磁石、 前記一対の板状継鉄を磁気的に結合し、前記永久磁石間
の均一磁界空間の中心からみて連続して１５０度以上の
開放角度を有する開放部を形成するように設けられる支
持継鉄、および少なくとも一方の前記板状継鉄の前記開
放部に対応する他方主面に設けられるシールド用磁石を
備える、磁界発生装置。6. A pair of plate-shaped yoke which are arranged to face each other with an air gap formed therebetween; a permanent magnet which is arranged on one of the main surfaces of each of said pair of plate-shaped yoke facing each other; And a support yoke provided to form an opening having an opening angle of 150 ° or more continuously as viewed from the center of the uniform magnetic field space between the permanent magnets, and at least one of the plate-like members. A magnetic field generator, comprising: a shielding magnet provided on the other main surface corresponding to the opening of the yoke.
継鉄の他方主面は斜面を有し、前記斜面に前記シールド
用磁石が設けられる、請求項６に記載の磁界発生装置。7. The magnetic field generator according to claim 6, wherein the other main surface of the plate-like yoke has a slope so that the plate-like yoke becomes thinner, and the shield magnet is provided on the slope. .
が発生される、請求項６または７に記載の磁界発生装
置。8. The magnetic field generator according to claim 6, wherein a magnetic field of 0.3 T or more is generated in the uniform magnetic field space.
ある、請求項１から８のいずれかに記載の磁界発生装
置。9. The magnetic field generator according to claim 1, wherein the shield magnet is a rare earth sintered magnet.
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|---|---|---|---|
| JP2002057766A JP3653253B2 (en) | 2000-08-09 | 2002-03-04 | Magnetic field generator |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2000241609 | 2000-08-09 | ||
| JP2000-241609 | 2000-08-09 | ||
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP2001230844A Division JP3304970B2 (en) | 2000-08-09 | 2001-07-31 | Magnetic field generator and method of assembling the same |
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| Publication Number | Publication Date |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP1455196A2 (en) * | 2003-03-07 | 2004-09-08 | GE Medical Systems Global Technology Company LLC | Magnetic resonance imaging system |
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2002
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP1455196A2 (en) * | 2003-03-07 | 2004-09-08 | GE Medical Systems Global Technology Company LLC | Magnetic resonance imaging system |
| KR20040078905A (en) * | 2003-03-07 | 2004-09-13 | 지이 메디컬 시스템즈 글로발 테크놀러지 캄파니 엘엘씨 | Magnetic resonance imaging system |
| EP1455196A3 (en) * | 2003-03-07 | 2005-04-20 | GE Medical Systems Global Technology Company LLC | Magnetic resonance imaging system |
| US7276907B2 (en) | 2003-03-07 | 2007-10-02 | Ge Medical Systems Global Technology Company, Llc | Magnetic resonance imaging system |
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