JPH04196109A - magnetic field generator - Google Patents
magnetic field generatorInfo
- Publication number
- JPH04196109A JPH04196109A JP2321754A JP32175490A JPH04196109A JP H04196109 A JPH04196109 A JP H04196109A JP 2321754 A JP2321754 A JP 2321754A JP 32175490 A JP32175490 A JP 32175490A JP H04196109 A JPH04196109 A JP H04196109A
- Authority
- JP
- Japan
- Prior art keywords
- magnetic
- permanent magnet
- magnetic field
- magnetized
- pole piece
- 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.)
- Pending
Links
- 239000000696 magnetic material Substances 0.000 claims description 9
- 230000005415 magnetization Effects 0.000 claims description 4
- 230000004907 flux Effects 0.000 description 15
- 229910000976 Electrical steel Inorganic materials 0.000 description 4
- 238000010586 diagram Methods 0.000 description 4
- 230000008878 coupling Effects 0.000 description 3
- 238000010168 coupling process Methods 0.000 description 3
- 238000005859 coupling reaction Methods 0.000 description 3
- 229910052761 rare earth metal Inorganic materials 0.000 description 3
- 230000003068 static effect Effects 0.000 description 3
- 229910001209 Low-carbon steel Inorganic materials 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 238000010030 laminating Methods 0.000 description 2
- 230000035699 permeability Effects 0.000 description 2
- 150000002910 rare earth metals Chemical class 0.000 description 2
- 238000001514 detection method Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 229910052734 helium Inorganic materials 0.000 description 1
- 239000001307 helium Substances 0.000 description 1
- SWQJXJOGLNCZEY-UHFFFAOYSA-N helium atom Chemical compound [He] SWQJXJOGLNCZEY-UHFFFAOYSA-N 0.000 description 1
- 238000003384 imaging method Methods 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 229910001172 neodymium magnet Inorganic materials 0.000 description 1
- 238000005096 rolling process Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R33/00—Arrangements or instruments for measuring magnetic variables
- G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
- G01R33/28—Details of apparatus provided for in groups G01R33/44 - G01R33/64
- G01R33/38—Systems for generation, homogenisation or stabilisation of the main or gradient magnetic field
- G01R33/383—Systems for generation, homogenisation or stabilisation of the main or gradient magnetic field using permanent magnets
Landscapes
- Physics & Mathematics (AREA)
- Condensed Matter Physics & Semiconductors (AREA)
- General Physics & Mathematics (AREA)
- Magnetic Resonance Imaging Apparatus (AREA)
Abstract
(57)【要約】本公報は電子出願前の出願データであるた
め要約のデータは記録されません。(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.
Description
【発明の詳細な説明】
［産業上の利用分野コ
本発明は、被検体の断層像を撮影する核磁気共鳴撮像装
置（以下、ＭＨＩ装置と呼ぶ）などに用いられる広い空
隙内に高強度かつ高精度で均一な静磁場を発生させる磁
界発生装置に関する。[Detailed Description of the Invention] [Industrial Field of Application] The present invention is directed to a high-strength and This invention relates to a magnetic field generator that generates a highly accurate and uniform static magnetic field.
［従来の技術］
ＭＨＩ装置における磁界発生手段としては、永久磁石方
式、常電導磁石方式、超電導磁石方式の３方式がある。[Prior Art] There are three types of magnetic field generating means in an MHI device: a permanent magnet type, a normal conducting magnet type, and a superconducting magnet type.
この中で、永久磁石方式は電力やヘリウムの消費を伴わ
ないため最も経済的であり、また比較的漏洩磁束が少な
い、コンパクトであるため設置性に優れている等の長所
を有する。さらに近年、強い磁力を持つ希土類磁石の出
現と信号検出装置の性能およびイメージング技術の向上
によって、永久磁石方式ＭＨＩ装置は急速に普及してい
る。Among these, the permanent magnet method is the most economical because it does not involve the consumption of electric power or helium, and has the advantages of having relatively little leakage magnetic flux and being compact, making it easy to install. Furthermore, in recent years, with the advent of rare earth magnets with strong magnetic force and improvements in the performance of signal detection devices and imaging technology, permanent magnet MHI devices have rapidly become popular.
ＭＲ工装置では静磁場の強度と均一性が撮影画像の画質
に影響を及ぼすため、被検体が挿入される空隙中心付近
に高強度かっ１０−′以下の粘度で均一な磁界が要求さ
れる。In MR equipment, the strength and uniformity of the static magnetic field affect the quality of the photographed image, so a uniform magnetic field with high strength and a viscosity of 10-' or less is required near the center of the gap into which the subject is inserted.
従来の永久磁石方式の磁界発生装置は、第２図に示すよ
うに、空隙を形成して対向する一対のポールピースの各
々の側面部に複数個の永久磁石部を設け、上下に配した
前記永久磁石部の外側を磁気的に結合する磁性体材を設
けた構造を成しており、前記永久磁石部の結合部は同一
ポールピースに対して同極に磁化され、上下のポールピ
ースとの結合部においては異極に磁化されている＋１４
造を成していた。As shown in FIG. 2, a conventional permanent magnet type magnetic field generating device has a plurality of permanent magnet sections provided on each side surface of a pair of pole pieces facing each other with a gap formed between them. It has a structure in which a magnetic material is provided to magnetically couple the outside of the permanent magnet part, and the coupling part of the permanent magnet part is magnetized to the same polarity with respect to the same pole piece, and the connection part of the permanent magnet part is magnetized with the same polarity with respect to the upper and lower pole pieces. +14 magnetized to different polarities at the junction
It had a structure.
［発明が解決しようとする課題］
しかし前述の従来技術においては、空隙に高強度な均一
磁場を発生させることは十分可能であるが、磁気回路外
部への漏洩磁束量が大きいため磁気回路外部の磁性体に
よる影響を受は易く、空隙中心の静磁場の均一性を維持
することが困難であるという問題点を有していた。[Problems to be Solved by the Invention] However, in the above-mentioned conventional technology, although it is sufficiently possible to generate a high-intensity uniform magnetic field in the air gap, the amount of magnetic flux leaking to the outside of the magnetic circuit is large, so the amount of magnetic flux outside the magnetic circuit is The problem is that it is easily influenced by magnetic substances, and that it is difficult to maintain the uniformity of the static magnetic field at the center of the air gap.
そこで本発明の目的とするところは、磁気回路外部への
漏洩磁束を減少させ、より空隙中心へ磁束が流れるよう
な効率の良い磁界発生装置の＋１４造を提案することで
ある。Therefore, an object of the present invention is to propose an efficient magnetic field generating device with a +14 structure that reduces leakage magnetic flux to the outside of the magnetic circuit and allows the magnetic flux to flow more toward the center of the air gap.
［課題を解決するための手段］
本発明の磁界発生装置は、空隙を形成して対向する一対
のポールピースの各々の側面部に複数個の永久磁石部を
設け、上下に配した前記永久磁石部の外側を磁気的に結
合する磁性体材を設けて磁気回路を構成し、前記永久磁
石部の結合部は同一ポールピースに対して同極に磁化さ
れ、上下のポールピースとの結合部においては異極に磁
化されている磁界発生装置において、前記ポールピース
の一部または全体を前記永久磁石部の磁化方向に対して
水平方向に積層した軟質磁性材料から成る磁性板の積層
構造としたことを特徴とする。[Means for Solving the Problems] A magnetic field generating device of the present invention includes a plurality of permanent magnet portions provided on each side surface of a pair of pole pieces facing each other with a gap formed therebetween, and the permanent magnet portions arranged above and below. A magnetic circuit is constructed by providing a magnetic material that magnetically couples the outside of the permanent magnet part, and the coupling part of the permanent magnet part is magnetized to the same polarity with respect to the same pole piece, and the coupling part of the permanent magnet part is magnetized with the same polarity to the same pole piece, and In a magnetic field generating device magnetized with different polarities, a part or the whole of the pole piece has a laminated structure of magnetic plates made of a soft magnetic material laminated in a direction horizontal to the magnetization direction of the permanent magnet part. It is characterized by
［実施例コ
第１図（ａ）は本発明の実施例における磁界発生装置に
用いる磁気回路を示す説明図である。空隙４を形成して
対向する一対のポールピース２の各々の側面部にそれぞ
れ４個の永久磁石部１を設け、上下に配した前記永久磁
石部１の外側を磁気的に結合する磁性体材３を設けて磁
気回路を構成し、永久磁石部１の結合部は同一ポールピ
ースに対して同極に磁化され、上下のポールピース２と
の結合部においては異極に磁化されている。ここで使用
する永久磁石は、磁気回路の重量増加を避けるため最大
エネルギー積（ＢＨ）、、、が２５メカガウスエルステ
ツド（ＭＧＯｅ）以上であるＮｄ−Ｆｅ−Ｂ系、あるい
はＰｒ−Ｆｅ−Ｂ系などの希土類磁石が望ましい。Embodiment FIG. 1(a) is an explanatory diagram showing a magnetic circuit used in a magnetic field generating device in an embodiment of the present invention. Four permanent magnet sections 1 are provided on each side surface of a pair of pole pieces 2 facing each other with a gap 4 formed therebetween, and a magnetic material magnetically couples the outsides of the permanent magnet sections 1 arranged above and below. 3 are provided to constitute a magnetic circuit, and the connecting portion of the permanent magnet portion 1 is magnetized with the same polarity with respect to the same pole piece, and the connecting portion with the upper and lower pole pieces 2 is magnetized with different polarities. In order to avoid an increase in the weight of the magnetic circuit, the permanent magnets used here are Nd-Fe-B-based or Pr-Fe- Rare earth magnets such as B-based magnets are desirable.
第１図（ｂ）は第１図（ａ）に示す磁気回路に用いたポ
ールピース２の縦断面の部分拡大図である。一対のポー
ルピース２の各々の反空隙側２１は、珪素鋼板から成る
磁性板５を永久磁石部１の磁化方向に対して水平方向に
積層して構成し、空隙側２２は一枚の電磁軟鋼板を切削
加工して構成した。ここで使用した珪素鋼板の最大透磁
率は７０００、電磁軟鋼板の最大透磁率は５０００であ
る。FIG. 1(b) is a partially enlarged longitudinal cross-sectional view of the pole piece 2 used in the magnetic circuit shown in FIG. 1(a). The anti-gap side 21 of each of the pair of pole pieces 2 is formed by laminating magnetic plates 5 made of silicon steel plates in a direction horizontal to the magnetization direction of the permanent magnet part 1, and the air gap side 22 is made of a sheet of electromagnetic mild steel. It was constructed by cutting a plate. The maximum magnetic permeability of the silicon steel plate used here is 7,000, and the maximum magnetic permeability of the electromagnetic mild steel plate is 5,000.
このようにポールピースの反空隙側２１を珪素鋼板から
成る磁性板５の積層構造とすることによって、磁性板５
間に磁気抵抗の大きな非磁性部分すなわち空気層が形成
されるため、磁束は磁気抵抗の小さな磁性板５内を通り
易くなり、この結果ポールピース２から磁気回路外部へ
の漏洩磁束が減少し、空隙５内の磁界強度を向上させる
ことができ、効率の良い磁気回路となる。In this way, by forming the anti-gap side 21 of the pole piece into a laminated structure of the magnetic plates 5 made of silicon steel plates, the magnetic plates 5
Since a non-magnetic part with high magnetic resistance, that is, an air layer, is formed between the magnetic plates 5 and 5, magnetic flux can easily pass through the magnetic plate 5 with low magnetic resistance, and as a result, leakage magnetic flux from the pole piece 2 to the outside of the magnetic circuit is reduced. The magnetic field strength within the air gap 5 can be improved, resulting in an efficient magnetic circuit.
上述した磁気回路において、基本組成がＰｒ］７原子％
、Ｆｅ７６．５原子％、Ｂ５原子％、Ｃｕ１．５原子％
で、熱間／圧延加工によって製造された希土類磁石で、
最大エネルギー積が２６゜２ＭＧＯｅのものを１．、
４Ｌｏｎ使用し、有効ギャップ長さしを５００ ｍｍに
設定したところ、磁気回路の垂直軸上方２ｍの位置にお
ける漏洩磁束密度は１１Ｇであり、空隙中心の磁束密度
は２２０４．Ｇであった。In the magnetic circuit described above, the basic composition is Pr] 7 atomic %
, Fe76.5 at%, B5 at%, Cu1.5 at%
A rare earth magnet manufactured by hot/rolling process,
1. The maximum energy product is 26°2MGOe. ,
When 4Lon was used and the effective gap length was set to 500 mm, the leakage magnetic flux density at a position 2 m above the vertical axis of the magnetic circuit was 11G, and the magnetic flux density at the center of the air gap was 2204mm. It was G.
第２図は従来の磁気回路の構成を示す説明図である。空
隙４を形成して対向する一対のポールピース２の各々の
側面部にそれぞれ４個の永久磁石部１を設け、上下に配
した前記永久磁石部１の外側を磁気的に結合する磁性体
材３を設けた構造を成しており、永久磁石部１の結合部
は同一ポールピースに対して同極に磁化され、上下のポ
ールピース２との結合部においては異極に磁化されてい
る。ただしポールピース２は一体物を切削し表面加工し
て成形された軟質磁性材料から成る。この磁気回路に、
第１図に示した磁気回路に用いた磁石と同条件の磁石を
用い、有効ギャップ長さしを５００ｍｍとしたところ、
磁気回路の垂直軸」ニガ２ｍの位置における漏洩磁束密
度は２０Ｇであり、空隙中心の磁束密度は２０００Ｇで
あった。FIG. 2 is an explanatory diagram showing the configuration of a conventional magnetic circuit. Four permanent magnet sections 1 are provided on each side surface of a pair of pole pieces 2 facing each other with a gap 4 formed therebetween, and a magnetic material magnetically couples the outsides of the permanent magnet sections 1 arranged above and below. 3, the joint part of the permanent magnet part 1 is magnetized with the same polarity for the same pole piece, and the joint part with the upper and lower pole pieces 2 is magnetized with different polarities. However, the pole piece 2 is made of a soft magnetic material that is formed by cutting and surface processing a single piece. In this magnetic circuit,
Using a magnet with the same conditions as the magnet used in the magnetic circuit shown in Figure 1, and setting the effective gap length to 500 mm,
The leakage magnetic flux density at a position of 2 m on the vertical axis of the magnetic circuit was 20G, and the magnetic flux density at the center of the air gap was 2000G.
本実施例と従来例を比較すると漏洩磁束は約半分に減少
し、その結果空隙中心の磁束密度は２００Ｇ以上向上し
た。Comparing this example with the conventional example, the leakage magnetic flux was reduced by about half, and as a result, the magnetic flux density at the center of the air gap was improved by more than 200G.
［発明の効果］
以上述べたように本発明によれば、一対のポールピース
の各々の反空隙側を、珪素鋼板から成る磁性板を永久磁
石部の磁化方向と水平な方向に積層して構成することに
よって、磁性板間に磁気抵抗の大きな非磁性部分すなわ
ち空気層が形成され、磁束は磁気抵抗の小さな磁性板内
を通り易くなる。[Effects of the Invention] As described above, according to the present invention, the anti-gap side of each of the pair of pole pieces is constructed by laminating magnetic plates made of silicon steel plates in a direction parallel to the magnetization direction of the permanent magnet part. By doing so, a non-magnetic portion with high magnetic resistance, that is, an air layer is formed between the magnetic plates, and magnetic flux can easily pass through the magnetic plates with low magnetic resistance.
したがってポールピースから磁気回路外部への漏洩磁束
が減少し、空隙内の磁界強度を向上させることを可能と
した。Therefore, leakage magnetic flux from the pole piece to the outside of the magnetic circuit is reduced, making it possible to improve the magnetic field strength within the air gap.
第１図（ａ）は本発明の実施例における磁界発生装置の
磁気回路の基本構造を示す説明図。
第１図（ｂ）は本発明の実施例における磁界発生装置の
磁気回路に用いたポールピースの縦断面の部分拡大図。
第２図は従来の磁気回路の構造を示す説明図。
１・・永久磁石部、２・・ポールピース、２１・・・ポ
ールピース反空隙側、
２２・・・ポールピース空隙側、３・・・磁性体材、４
・・・空隙、５・・・磁性板FIG. 1(a) is an explanatory diagram showing the basic structure of a magnetic circuit of a magnetic field generating device in an embodiment of the present invention. FIG. 1(b) is a partially enlarged longitudinal cross-sectional view of a pole piece used in a magnetic circuit of a magnetic field generating device in an embodiment of the present invention. FIG. 2 is an explanatory diagram showing the structure of a conventional magnetic circuit. 1...Permanent magnet part, 2...Pole piece, 21...Pole piece anti-air gap side, 22...Pole piece air gap side, 3...Magnetic material, 4
...Gap, 5...Magnetic plate
Claims (1)
側面部に複数個の永久磁石部を設け、上下に配した前記
永久磁石部の外側を磁気的に結合する磁性体材を設けて
磁気回路を構成し、前記永久磁石部の結合部は同一ポー
ルピースに対して同極に磁化され、上下のポールピース
との結合部においては異極に磁化されている磁界発生装
置において、前記ポールピースの一部または全体を前記
永久磁石部の磁化方向に対して水平方向に積層した軟質
磁性材料から成る磁性板の積層構造としたことを特徴と
する磁界発生装置。A plurality of permanent magnet sections are provided on each side surface of a pair of pole pieces facing each other with a gap formed therebetween, and a magnetic material is provided to magnetically couple the outsides of the permanent magnet sections arranged above and below, thereby creating a magnetic circuit. In the magnetic field generating device, the connecting portion of the permanent magnet portion is magnetized with the same polarity with respect to the same pole piece, and the connecting portion with the upper and lower pole pieces is magnetized with different polarities. A magnetic field generating device characterized in that a part or the entirety thereof has a laminated structure of magnetic plates made of a soft magnetic material laminated in a direction horizontal to the magnetization direction of the permanent magnet part.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2321754A JPH04196109A (en) | 1990-11-26 | 1990-11-26 | magnetic field generator |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2321754A JPH04196109A (en) | 1990-11-26 | 1990-11-26 | magnetic field generator |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH04196109A true JPH04196109A (en) | 1992-07-15 |
Family
ID=18136075
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP2321754A Pending JPH04196109A (en) | 1990-11-26 | 1990-11-26 | magnetic field generator |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH04196109A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0645641A1 (en) * | 1993-09-29 | 1995-03-29 | Oxford Magnet Technology Limited | Improvements in or relating to MRI magnets |
-
1990
- 1990-11-26 JP JP2321754A patent/JPH04196109A/en active Pending
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0645641A1 (en) * | 1993-09-29 | 1995-03-29 | Oxford Magnet Technology Limited | Improvements in or relating to MRI magnets |
| US5680086A (en) * | 1993-09-29 | 1997-10-21 | Oxford Magnet Technology Limited | MRI magnets |
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