JPH0314011Y2 - - Google Patents
Info
- Publication number
- JPH0314011Y2 JPH0314011Y2 JP14797886U JP14797886U JPH0314011Y2 JP H0314011 Y2 JPH0314011 Y2 JP H0314011Y2 JP 14797886 U JP14797886 U JP 14797886U JP 14797886 U JP14797886 U JP 14797886U JP H0314011 Y2 JPH0314011 Y2 JP H0314011Y2
- Authority
- JP
- Japan
- Prior art keywords
- magnetic field
- magnet
- magnets
- rare earth
- ferrite
- 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.)
- Expired
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- 229910052761 rare earth metal Inorganic materials 0.000 claims description 29
- 150000002910 rare earth metals Chemical class 0.000 claims description 29
- 229910000859 α-Fe Inorganic materials 0.000 claims description 28
- 229910017052 cobalt Inorganic materials 0.000 description 3
- 239000010941 cobalt Substances 0.000 description 3
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 description 3
- 230000002093 peripheral effect Effects 0.000 description 2
- 230000003068 static effect Effects 0.000 description 2
- 229910052712 strontium Inorganic materials 0.000 description 2
- CIOAGBVUUVVLOB-UHFFFAOYSA-N strontium atom Chemical compound [Sr] CIOAGBVUUVVLOB-UHFFFAOYSA-N 0.000 description 2
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- 238000005481 NMR spectroscopy Methods 0.000 description 1
- 229910052779 Neodymium Inorganic materials 0.000 description 1
- 229910052777 Praseodymium Inorganic materials 0.000 description 1
- 229910000828 alnico Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- 239000002826 coolant Substances 0.000 description 1
- 239000000498 cooling water Substances 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
- 239000010949 copper Substances 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000005611 electricity 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
- 235000000396 iron Nutrition 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 230000005415 magnetization Effects 0.000 description 1
- AJCDFVKYMIUXCR-UHFFFAOYSA-N oxobarium;oxo(oxoferriooxy)iron Chemical compound [Ba]=O.O=[Fe]O[Fe]=O.O=[Fe]O[Fe]=O.O=[Fe]O[Fe]=O.O=[Fe]O[Fe]=O.O=[Fe]O[Fe]=O.O=[Fe]O[Fe]=O AJCDFVKYMIUXCR-UHFFFAOYSA-N 0.000 description 1
- 230000003014 reinforcing effect Effects 0.000 description 1
- 238000003325 tomography Methods 0.000 description 1
Landscapes
- Magnetic Resonance Imaging Apparatus (AREA)
Description
利用産業分野
この考案は、対象物の断面イメージを得て組織
の性質まで描き出すことのできる医療用核磁気共
鳴断層撮影装置（以下、NMR−CTという）に
用いられる永久磁石を使用した磁界発生装置に係
り、大きな空隙内に強力かつ高精度で均一な静磁
界を発生する磁界発生装置に関する。
背景技術
NMR−CTは、人体の一部または全部を１〜
10kGの強力な磁界を形成する空隙内に挿入して
所要の断層イメージを得るため、この磁界が強力
かつ10-4以下の精度で均一に安定していることが
要求され、NMR−CT用の磁界発生装置として
は、銅またはアルミニウムからなり導線を円筒状
に巻着した常伝導磁石あるいは、特殊な導線を用
い、絶対零度付近の温度に冷却して使用する超伝
導磁石が知られている。
前者は構造上安価であるが十分な強力磁界を発
生させるためには、膨大な電力と冷却水が必要で
あり、ランニングコストが高い等の問題があり、
一方、後者の超伝導磁石は、電力の消費が少なく
小型で強力な磁界を発生し得る利点があるが、冷
媒として高価な液体ヘリウム等の使用が不可欠で
あり、いわゆるイニシヤルコストとともにランニ
ングコストも著しく高い問題がある。
本出願人は、先に、磁界強度が上記の常伝導磁
石と同等以上で、ランニングコストが安く、超電
導磁石、常電導磁石に比べて、漏洩磁界の少ない
永久磁石を使用した磁界発生装置を提案（実願昭
59−53575号）した。
上記磁界発生装置は、第２図に示す如く、一対
の永久磁石構成体１，１の各々の一方端に磁極片
２，２を固着して対向させ、他方端を継鉄３で結
合し、磁極片２，２間の空隙内４に、静磁界を発
生させる構成であり、一対の磁極片２，２には、
その対向面の周縁に、所定の内径、高さからなる
断面略台形の環状突起５を突設し、さらに、磁極
片２，２の中央部に、所定径、高さからなる断面
略台形の凸状突起６を設けた構成からなり、空隙
４内に、強力かつ均一精度の高い磁界を発生す
る。
また、本出願人は上記磁界発生装置に用いる永
久磁石は、フエライト磁石、アルニコ系磁石、希
土類コバルト系磁石が使用できるが、先に出願人
が提案（特願昭57−145072号）した、Ｒとして
NdやPrを中心とする資源的に豊富な軽希土類を
用い、Ｂ，Feを主成分として25MGOe以上の極
めて高いエネルギー積を示す、Fe−Ｂ−Ｒ系永
久磁石を使用することにより、著しく小型化する
ことができることを提案した。
上記磁界発生装置によれば空隙内に強力かつ均
一精度の高い磁界を形成することが可能になる
が、通常、一対の永久磁石構成体は、前記各種の
永久磁石のみにて構成するため、例えば、フエラ
イト磁石のみにては安価にできるが、装置の小型
化及び磁界強度にも限度があり、一方希土類コバ
ルト系磁石、Fe−Ｂ−Ｒ系永久磁石等の希土類
磁石のみでは装置の小型化及び磁界強度の向上に
は有効であるが高価であり、しかも、磁力が非常
に強いため、組立時の作業性の点で問題があつ
た。また、近年、磁界発生装置の改善のみならず
周辺機器の改善により、空隙内の磁界強度が１〜
1.5KG程度でも鮮明な画像を得ることが可能とな
り、これらの進歩に応じた実用性にすぐれ、かつ
経済的にも有利な磁界発生装置の提案が望まれ、
特に磁界発生源となる永久磁石の効率的な配置構
成が必要とされている。
考案の目的
この考案は、かかる現状に鑑み、所要空隙に高
精度で均一かつ安定な磁界を発生する磁界発生装
置において、小型でかつ経済的に有利な磁界発生
装置を目的とし、特に材質の異なる永久磁石を適
正配置した永久磁石構成体を用い、磁気的に効率
の良い構成からなる磁界発生装置を目的としてい
る。
考案の構成と効果
この考案は、高精度で均一かつ安定な磁界が得
られ、かつ小型で経済的に有利な磁界発生装置を
目的とし、種々検討した結果、一対の永久磁石構
成体を、フエライト磁石と希土類磁石にて構成す
ることにより、各々永久磁石の長所を有効に活用
できることを知見し、提案するものである。
詳述すれば、磁界発生装置において、被診断対
象物の挿入される空隙の大きさ及び均一磁界空間
の大きさが決定されると、それに必要な磁極片の
大きさ（直径）も一義的に決定されるため、特に
空隙内の磁界強度が1kG程度となると、希土類永
久磁石のみの構成では磁気的に効率の良い、すな
わち最適動作点での使用は困難となるが、後述す
る如く、フエライト磁石を併用して適正配置する
ことにより、これら永久磁石の動作点の最適化が
可能となることを知見した。
この考案は、
空隙を形成して対向する一対の永久磁石構成体
を継鉄で磁気的強合し、各永久磁石構成体の空隙
対向面に磁極片を固着し、該空隙に磁界を発生さ
せる磁界発生装置において、
前記永久磁石構成体が、中央部に配設されるフ
エライト磁石と、
該フエライト磁石の周囲に配設される希土類磁
石とからなり、
かつフエライト磁石の継鉄への着設方向厚さ
が、希土類磁石の継鉄への着設方向厚さより大で
あることを特徴とする磁界発生装置である。
考案の好ましい実施態様
この考案の磁界発生装置において、磁石構成体
を構成するフエライト磁石は、ストロンチウムフ
エライト磁石、バリウムフエライト磁石等の異方
性フエライト磁石が好ましく、また、希土類磁石
としては、希土類コバルト磁石、Fe−Ｂ−Ｒ系
磁石等の異方性希土類磁石が望ましい。
フエライト磁石の周囲に配設する希土類磁石
は、必ずしもフエライト磁石の全周に周設する必
要はなく、要求される磁界強度等に応じて適宜所
用箇所に配置すれば良いが、このとき、フエライ
ト磁石の厚さが希土類磁石の厚さより薄くなる
と、希土類磁石の反磁界によつて減磁され、所要
の磁界強度を得ることが困難となるため、フエラ
イト磁石の継鉄への着設方向厚さは、希土類磁石
の継鉄への着設方向厚さより大とする必要があ
る。また、各々永久磁石の外径も要求される磁界
強度等に応じて適宜選定することが望ましい。
また、磁石構成体におけるフエライト磁石と希
土類磁石の厚みの比率は、小型化と両磁石の最適
動作点の観点より、希土類磁石厚みはフエライト
磁石厚みの1/2以下が好ましい。
磁界発生装置を構成する継鉄には、種々の構
成、形状のものが利用でき、例えば、一対の板状
継鉄を対向配置し、複数の柱状継鉄にて連結した
構成、円板状継鉄を対向配置し、両者を円筒状継
鉄にて接続した構成、開口方向を水平にした四角
筒状継鉄等が用いられる。
また、永久磁石構成体の空隙対向面に固着する
磁極片も、その対向面の周縁に、所定の内径、高
さからなる環状突起を突設させたり、さらに磁極
片中央部に所定の外径、高さからなる凸状突起を
設けた構成等、前記永久磁石や、継鉄と同様に要
求される磁界強度、磁界均一度等に応じて適宜選
定することが望ましい。
図面に基づく考案の開示
第１図Ａ，Ｂはこの考案による磁界発生装置に
用いる磁気回路のＡ−Ａ横断上面図と縦断面図で
ある。
磁気回路は、その継鉄１０が、正方形からなる
一対の板状継鉄１１，１２を対向配置して４本の
円柱状継鉄１３にて連結した構成からなり、前記
板状継鉄１１，１２の対向する内面に、この考案
による永久磁石構成体２０，３０を着設して、所
要の空隙１６を形成してある。
永久磁石構成体２０，３０は、中央部に外径
D1、厚みT1なる円板状のフエライト磁石２１，
３１を配し、その外周部に、外径D2、内径D1、
厚みT2なるリング状の希土類磁石２２，３２が
嵌着されている。
この希土類磁石２２，３２は、その厚みT2が
前記フエライト磁石２１，３１より薄いものであ
る。
また、フエライト磁石２１，３１及び希土類磁
石２２，３２の両磁石が、空隙１６側の磁極面に
て同一平面を形成するように、板状継鉄１１，１
２に着設したフエライト磁石２１，３１の外周部
に継鉄の環状突起座１３，１４を設け、希土類磁
石２２，３２をこの環状突起座１３，１４上に着
設する構成である。
また、永久磁石構成体２０，３０を構成するフ
エライト磁石２１，３１及び希土類磁石２２，３
２は、それぞれブロツク状の永久磁石を多数個用
いて、着磁組立にて前記形状に構成し、磁極面に
対して垂直方向に磁化方向を有している。
永久磁石構成体２０，３０の空隙１６側磁極面
には、それぞれ磁極片１７，１８が着設され、磁
極片１７，１８には、外周縁部に断面台形の環状
突起１７ａ，１８ａが、中央部には断面扁平台形
状の凸状突起１７ｂ，１８ｂが設けられている。
上記構成により、安価なフエライト磁石と磁気
特性のすぐれた希土類磁石との併用において、磁
気的に有効かつ安定利用でき、小型かつ安価な磁
界発生装置が得られる。
実施例
前述した第１図の構成からなる磁界発生装置
に、中央部のフエライト磁石として（BH）
max4MGOeを有する異方性ストロンチウムフエ
ライト磁石を用い、また、希土類磁石として、
（BH）max35MGOeを有する異方性Fe−Ｂ−Ｒ
系磁石を用い、磁極片直径を一定にかつ磁極片間
距離を450mmに設定し、同一磁界範囲（300mm、
DSV）で同一の均一度（60ppm以下）を得るに
際し、空隙中央部の磁界強度（Bg）を、800G，
1000G，1200Gとしたときのフエライト磁石と希
土類磁石の寸法比を検討したところ、第１表の結
果を得た。
また、比較のため、永久磁石構成体に（BH）
max35MGOeを有する異方性Fe−Ｂ−Ｒ系磁石
（外径D0、厚みT0）のみを用いた第２図に示す構
成の磁界発生装置にて、磁極片直径を一定にかつ
磁極片間距離を450mmに設定し、
同一磁界範囲（300mm、DSV）で、同一の均一
度（60ppm以下）を得るに際し、空隙中央部の磁
界強度（Bg）を、800G，1000G，1200Gとした
ときにおける本考案装置の永久磁石構成体との寸
法比を検討したところ、第１表の結果を得た。
Application Industry Field This idea is a magnetic field generator using a permanent magnet used in medical nuclear magnetic resonance tomography (hereinafter referred to as NMR-CT), which can obtain cross-sectional images of objects and depict the properties of tissues. The present invention relates to a magnetic field generating device that generates a strong, highly accurate, and uniform static magnetic field within a large air gap. BACKGROUND ART
In order to obtain the desired tomographic image by inserting the device into an air gap that generates a strong magnetic field of 10 kG, this magnetic field must be strong and uniformly stable with an accuracy of 10 -4 or less. Known magnetic field generators include normal conducting magnets made of copper or aluminum and made of conductive wire wrapped around them in a cylindrical shape, and superconducting magnets that use special conducting wire and are cooled to a temperature close to absolute zero. The former is structurally inexpensive, but it requires a huge amount of electricity and cooling water to generate a sufficiently strong magnetic field, and has problems such as high running costs.
On the other hand, the latter type of superconducting magnet has the advantage of consuming less power and being able to generate a strong magnetic field in a small size, but it is essential to use expensive liquid helium as a coolant, which increases the running cost as well as the so-called initial cost. There are significant problems. The applicant previously proposed a magnetic field generator using a permanent magnet, which has a magnetic field strength equal to or higher than that of the above-mentioned normal conducting magnet, has low running costs, and has less magnetic field leakage than superconducting magnets and normal conducting magnets. (Akira Jigan
No. 59-53575). As shown in FIG. 2, the magnetic field generating device described above includes a pair of permanent magnet structures 1, 1, with magnetic pole pieces 2, 2 fixed to one end of each of them facing each other, and the other ends being connected by a yoke 3. It is configured to generate a static magnetic field in the air gap 4 between the magnetic pole pieces 2, 2, and the pair of magnetic pole pieces 2, 2 include:
An annular protrusion 5 having a substantially trapezoidal cross section with a predetermined inner diameter and height is protruded from the periphery of the opposing surface, and an annular protrusion 5 having a substantially trapezoidal cross section with a predetermined inner diameter and height is provided at the center of the pole pieces 2, 2. It has a configuration in which convex projections 6 are provided, and generates a strong, uniform and highly accurate magnetic field within the air gap 4. In addition, the present applicant has previously proposed (Japanese Patent Application No. 57-145072) that although ferrite magnets, alnico magnets, and rare earth cobalt magnets can be used as the permanent magnets used in the magnetic field generating device, R as
By using light rare earths, which are abundant in resources such as Nd and Pr, and Fe-B-R permanent magnets, which are mainly composed of B and Fe and exhibit an extremely high energy product of 25 MGOe or more, they are extremely compact. proposed that it could be made into According to the magnetic field generating device described above, it is possible to form a strong and uniform magnetic field with high accuracy in the air gap, but since the pair of permanent magnet members is usually composed of only the above-mentioned types of permanent magnets, for example, Although ferrite magnets alone can be used at low cost, there are limits to device miniaturization and magnetic field strength.On the other hand, rare earth magnets such as rare earth cobalt magnets and Fe-B-R permanent magnets have limitations in device miniaturization and magnetic field strength. Although it is effective in improving the magnetic field strength, it is expensive, and the magnetic force is very strong, which poses problems in terms of workability during assembly. In addition, in recent years, improvements in not only magnetic field generators but also peripheral equipment have increased the magnetic field strength within the air gap from 1 to 1.
It is now possible to obtain clear images even with a force of around 1.5 kg, and it is desired to propose a magnetic field generating device that is highly practical and economically advantageous in accordance with these advances.
In particular, there is a need for an efficient arrangement of permanent magnets that serve as magnetic field generation sources. Purpose of the invention In view of the current situation, the purpose of this invention is to create a small and economically advantageous magnetic field generator that generates a highly accurate, uniform, and stable magnetic field in a required air gap. The purpose of the present invention is to provide a magnetic field generating device that uses a permanent magnet structure in which permanent magnets are appropriately arranged and has a magnetically efficient structure. Structure and effects of the invention The aim of this invention was to create a compact and economically advantageous magnetic field generator that can generate a highly accurate, uniform, and stable magnetic field.As a result of various studies, a pair of permanent magnet components were made of ferrite. We have found that by constructing a magnet and a rare earth magnet, the advantages of each permanent magnet can be effectively utilized, and we propose this. Specifically, in a magnetic field generation device, once the size of the air gap into which the object to be diagnosed is inserted and the size of the uniform magnetic field space are determined, the size (diameter) of the magnetic pole piece required for it is also uniquely determined. Therefore, especially when the magnetic field strength in the air gap is about 1 kG, it is difficult to use a configuration with only rare earth permanent magnets that is magnetically efficient, that is, at the optimum operating point. However, as described later, ferrite magnets We have discovered that by using these permanent magnets in combination and arranging them appropriately, it is possible to optimize the operating points of these permanent magnets. This idea involves forming a gap and magnetically reinforcing a pair of opposing permanent magnet structures using a yoke, fixing a magnetic pole piece to the surface of each permanent magnet structure facing the gap, and generating a magnetic field in the gap. In the magnetic field generating device, the permanent magnet structure includes a ferrite magnet disposed in the center and a rare earth magnet disposed around the ferrite magnet, and the direction in which the ferrite magnet is attached to the yoke is This magnetic field generating device is characterized in that the thickness is greater than the thickness of the rare earth magnet in the direction in which it is attached to the yoke. Preferred Embodiment of the Invention In the magnetic field generating device of this invention, the ferrite magnet constituting the magnet structure is preferably an anisotropic ferrite magnet such as a strontium ferrite magnet or a barium ferrite magnet, and the rare earth magnet is a rare earth cobalt magnet. , anisotropic rare earth magnets such as Fe-BR magnets are desirable. The rare earth magnets placed around the ferrite magnets do not necessarily need to be placed around the entire circumference of the ferrite magnets, but may be placed at appropriate locations depending on the required magnetic field strength, etc. If the thickness of the ferrite magnet becomes thinner than that of the rare earth magnet, it will be demagnetized by the demagnetizing field of the rare earth magnet, making it difficult to obtain the required magnetic field strength. , must be larger than the thickness of the rare earth magnet in the direction in which it is attached to the yoke. Further, it is desirable to appropriately select the outer diameter of each permanent magnet depending on the required magnetic field strength, etc. Further, as for the ratio of the thickness of the ferrite magnet and the rare earth magnet in the magnet structure, from the viewpoint of miniaturization and optimum operating points of both magnets, it is preferable that the thickness of the rare earth magnet is 1/2 or less of the thickness of the ferrite magnet. Various configurations and shapes can be used for the yoke constituting the magnetic field generation device. A structure in which irons are arranged facing each other and the two are connected by a cylindrical yoke, a square cylindrical yoke with the opening direction horizontal, etc. are used. In addition, the magnetic pole piece that is fixed to the air gap facing surface of the permanent magnet structure has an annular protrusion with a predetermined inner diameter and height protruding from the periphery of the opposing surface, and a predetermined outer diameter in the center of the magnetic pole piece. It is desirable to appropriately select a configuration in which a convex projection having a height is provided, etc., depending on the required magnetic field strength, magnetic field uniformity, etc., as in the case of the permanent magnet and the yoke. Disclosure of the invention based on the drawings FIGS. 1A and 1B are a cross-sectional top view and a vertical cross-sectional view taken along line A-A of a magnetic circuit used in a magnetic field generating device according to this invention. In the magnetic circuit, the yoke 10 has a configuration in which a pair of square plate-shaped yokes 11 and 12 are arranged facing each other and connected by four cylindrical yokes 13, and the plate-shaped yokes 11, Permanent magnet structures 20 and 30 according to this invention are attached to the opposing inner surfaces of the magnet 12 to form the required air gap 16. The permanent magnet structures 20 and 30 have an outer diameter in the center.
A disk-shaped ferrite magnet 21 with D 1 and thickness T 1 ,
31, and its outer circumference has an outer diameter D 2 , an inner diameter D 1 ,
Ring-shaped rare earth magnets 22 and 32 with a thickness T 2 are fitted. The rare earth magnets 22 and 32 have a thickness T 2 smaller than that of the ferrite magnets 21 and 31. Further, the plate yokes 11 and 1 are arranged so that both the ferrite magnets 21 and 31 and the rare earth magnets 22 and 32 form the same plane at the magnetic pole faces on the air gap 16 side.
The structure is such that annular projection seats 13 and 14 of the yoke are provided on the outer periphery of the ferrite magnets 21 and 31 attached to the magnets 2, and rare earth magnets 22 and 32 are mounted on the annular projection seats 13 and 14. Further, ferrite magnets 21, 31 and rare earth magnets 22, 3 constituting the permanent magnet structures 20, 30
No. 2 is formed into the above shape by magnetizing and assembling a large number of block-shaped permanent magnets, and has a magnetization direction perpendicular to the magnetic pole surface. Magnetic pole pieces 17 and 18 are attached to the magnetic pole faces of the permanent magnet structures 20 and 30 on the air gap 16 side, respectively, and the magnetic pole pieces 17 and 18 have annular protrusions 17a and 18a having a trapezoidal cross section on their outer peripheral edges, and annular protrusions 17a and 18a having a trapezoidal cross section in the center. Convex protrusions 17b and 18b each having a flat trapezoidal cross section are provided in the portion. With the above configuration, a compact and inexpensive magnetic field generating device that can be magnetically effectively and stably used in combination with an inexpensive ferrite magnet and a rare earth magnet with excellent magnetic properties can be obtained. Example In the magnetic field generator having the configuration shown in FIG.
Using an anisotropic strontium ferrite magnet with max4MGOe, and as a rare earth magnet,
(BH) Anisotropic Fe-B-R with max35MGOe
Using a system magnet, the diameter of the magnetic pole piece is constant and the distance between the magnetic pole pieces is set to 450 mm, and the same magnetic field range (300 mm,
DSV) to obtain the same uniformity (60 ppm or less), the magnetic field strength (Bg) at the center of the air gap is set to 800G,
When we examined the dimensional ratio of ferrite magnets and rare earth magnets at 1000G and 1200G, we obtained the results shown in Table 1. Also, for comparison, the permanent magnet structure (BH)
In a magnetic field generator configured as shown in Fig. 2 using only anisotropic Fe-B-R magnets (outer diameter D 0 , thickness T 0 ) with max35MGOe, the diameter of the magnetic pole piece is kept constant and the distance between the magnetic pole pieces is kept constant. When the distance is set to 450 mm and the magnetic field strength (Bg) at the center of the air gap is set to 800 G, 1000 G, and 1200 G to obtain the same uniformity (60 ppm or less) in the same magnetic field range (300 mm, DSV), When the dimensional ratio of the invented device to the permanent magnet structure was examined, the results shown in Table 1 were obtained.
【表】
第１表から明らかな如く、この考案の磁界発生
装置は、所望の空隙内磁界強度に応じて、フエラ
イト磁石と希土類磁石との最適寸法比を設定する
ことにより、空隙内での高い均一度が得られ、ま
た、同等磁界強度を有する従来装置と比較して、
永久磁石構成体の高さを実用上問題のない高さ
で、かつ高価な希土類磁石の使用量が1/2程度に
削減でき、小型でかつ経済的な磁界発生装置であ
ることが分る。[Table] As is clear from Table 1, the magnetic field generating device of this invention can generate a high level of energy within the air gap by setting the optimum size ratio between the ferrite magnet and the rare earth magnet according to the desired magnetic field strength within the air gap. Uniformity is obtained, and compared to conventional equipment with equivalent magnetic field strength,
It can be seen that the height of the permanent magnet structure is set to a height that does not cause any practical problems, and the amount of expensive rare earth magnets used can be reduced to about half, making it a small and economical magnetic field generating device.
第１図Ａ，Ｂはこの考案による磁界発生装置に
用いる磁気回路のＡ−Ａ横断上面図と縦断面図で
ある。第２図は従来の磁気回路を示す縦断説明図
である。
１０……継鉄、１１，１２……板状継鉄、１３
……円柱状継鉄、１４，１５……環状突起座、１
６……空隙、１７，１８……磁極片、２０，３０
……永久磁石構成体、２１，３１……フエライト
磁石、２２，３２……希土類永久磁石。
FIGS. 1A and 1B are a cross-sectional top view and a vertical cross-sectional view taken along the line A-A of a magnetic circuit used in a magnetic field generating device according to this invention. FIG. 2 is a longitudinal sectional view showing a conventional magnetic circuit. 10... Yoke, 11, 12... Plate yoke, 13
... Cylindrical yoke, 14, 15 ... Annular protrusion seat, 1
6... air gap, 17, 18... magnetic pole piece, 20, 30
... Permanent magnet structure, 21, 31 ... Ferrite magnet, 22, 32 ... Rare earth permanent magnet.
Claims (1)
を継鉄で磁気的結合し、各永久磁石構成体の空隙
対向面に磁極片を固着し、該空隙に磁界を発生さ
せる磁界発生装置において、前記永久磁石構成体
が、中央部に配設されるフエライト磁石と、該フ
エライト磁石の周囲に配設される希土類磁石とか
らなり、かつフエライト磁石の継鉄への着設方向
厚さが、希土類磁石の継鉄への着設方向厚さより
大であることを特徴とする磁界発生装置。 A magnetic field generating device that magnetically couples a pair of permanent magnet structures facing each other with a gap formed therebetween using a yoke, fixes a magnetic pole piece to a surface of each permanent magnet structure facing the gap, and generates a magnetic field in the gap, The permanent magnet structure includes a ferrite magnet disposed in the center and a rare earth magnet disposed around the ferrite magnet, and the thickness of the ferrite magnet in the direction in which it is attached to the yoke is made of rare earth magnets. A magnetic field generating device characterized in that the thickness is greater than the thickness of the magnet in the direction in which it is attached to the yoke.
Priority Applications (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP14797886U JPH0314011Y2 (en) | 1986-09-27 | 1986-09-27 | |
| US07/101,365 US4777464A (en) | 1986-09-27 | 1987-09-25 | Magnetic field generating device for NMR-CT |
| EP87308518A EP0262880B1 (en) | 1986-09-27 | 1987-09-25 | Magnetic field generating device for nmr-ct |
| DE8787308518T DE3779715T2 (en) | 1986-09-27 | 1987-09-25 | DEVICE FOR GENERATING A MAGNETIC FIELD FOR COMPUTER-CONTROLLED TOMOGRAPHY BY MEANS OF A MAGNETIC CORE RESONANCE. |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP14797886U JPH0314011Y2 (en) | 1986-09-27 | 1986-09-27 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS6355405U JPS6355405U (en) | 1988-04-13 |
| JPH0314011Y2 true JPH0314011Y2 (en) | 1991-03-28 |
Family
ID=31061829
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP14797886U Expired JPH0314011Y2 (en) | 1986-09-27 | 1986-09-27 |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH0314011Y2 (en) |
-
1986
- 1986-09-27 JP JP14797886U patent/JPH0314011Y2/ja not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| JPS6355405U (en) | 1988-04-13 |
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