JPS60183706A - Equipment for generating magnetic field - Google Patents

Abstract

PURPOSE:To obtain an equipment which has a magnetic circuit of enabling high accuracy, uniform and stable magnetic field by making each face of a magnetic pole piece a recessed and curved surface and making adjacent to the center of a permanent magnet having specific (BH) max. CONSTITUTION:Magnetic pole pieces 2 facing each other are each made a recessed and curved surface 5 and adjacent to the center of a permanent magnet 1 is made a permanent magnet 1b having 10MGOe or more less (BH) max. than the (BH) max. of the surrounding permanent magnet 1a. For example, in the case of a magnetic circuit used in an NMR-CT equipment, in the bore of a ring Fe-B-R permanent magnet 1a of external diameter D and internal diameter (d), a disk type Sr ferrite magnet 1b of external diameter (d) is inserted and fixed. At one end of the permanent magnet 1 integrated with 1a and 1b, magnetic pole pieces 2 is fixed facing each other and the other ends are connected with a yoke 3. In a void 4 between the pole pieces 2, strong magnetic field of 1-10kg is generated to diagnose part or the whole of a human body placed in the void.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is a method to obtain a cross-sectional image of an object based on the properties of the tissue. This invention relates to a magnetic field generating device that generates a strong, highly accurate, and uniform magnetic field in a narrow air gap, which is used in medical nuclear magnetic j4 sound tomography devices (hereinafter referred to as NMR-CI-) that can be exposed to the outside. .

NMR-CT examines part or all of the human body in 1 to 1.
In order to obtain the required tomographic image by inserting it into the air gap that forms a strong magnetic field of 5 KG, this magnetic field has a strong horn and a
It is required to be uniform and stable with an accuracy of -4 or less,
The magnetic field generator for 10 NMI's uses a normal conducting magnet with a core wire made of copper or aluminum wound into a cylindrical shape, or a special conducting wire cooled to a temperature close to absolute zero. Superconducting magnets are known for use in

The former is structurally inexpensive, but in order to generate a sufficiently strong horn magnetic field, it requires a huge amount of electricity and cooling water, and the running stress is high, and the leakage magnetic field created by the horn may be harmful depending on the application. 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 requires the use of expensive liquid helium etc. as a coolant. However, there is a problem that the initial cost and running cost are extremely high, so it has not been widely used.

The present applicant has previously developed a permanent magnet circuit with a magnetic field intensity equal to or higher than the above-mentioned regular electric current 711 magnets, no power consumption, and a small leakage magnetic field, with magnetic pole pieces facing each other with an air gap formed therein, and at least one The magnetic field generator J3 magnetically couples the permanent magnets 6 and the like with a yoke to generate a magnetic field in the air gap.
) proposed a magnetic field generating device in which each of the opposing surfaces of + and - was a concave curved surface. However, the magnetic field generated in the air gap has its highest value near the center, but as it moves away from the center, the strength of the magnetic field decreases in the peripheral air gap, making it uniform and stable with extremely high precision. It was not possible to withstand strong magnetic fields.

In view of the current situation, the present invention proposes a magnetic circuit that can generate a highly accurate, uniform, and stable magnetic field by placing it in the air gap of a magnetic field generator using permanent magnets that can generate a strong horned magnetic field. It is intended as a magnetic field generator.

In other words, the present invention provides a magnetic field generating device that magnetically couples magnetic pole pieces facing each other with an air gap and at least one permanent magnet using coarse ore to avoid generating a magnetic field in the air gap. Each of the opposing surfaces is a concave curved surface, and the permanent magnet in the peripheral part is right in the vicinity of the center of the permanent magnet (B)
-1) IOMGOQ smaller than max (BH n m
It is a magnetic field generating device that has 14 characteristics, with the ax being a permanent +41 stone.

In the magnetic field generator of this invention, the degree of C is extremely high.
(In order to create a uniform and stable air-gap magnetic field, (B H) max near the center of the permanent magnet J is smaller than ([3H> la
((B l-1) max at the center of 4j piece is 10M G
Beyond Oe, the peripheral part A' (1311) max is 2
If the difference between the two is less than 10 MGO θ, a uniform air gap magnetic field cannot be obtained over a wide range.
It is preferable that the max difference is 10MGOe or more, and the ([3+-1)max of the permanent magnet near the center E' is 10
~+GOθ or less, the permanent magnet around the center (F31
1) It is desirable that max is 20 MGOe or more.

The permanent magnets used in the magnetic field generating device of the present invention include Ferrai 1 ~ magnetic Tjs nofurnico type magnets, rare earth Kobal 1~ type magnets
Fe-B-R system (R is at least one rare earth element including Y) permanent magnet as a new high-performance permanent magnet that does not contain Sm or G (Japanese Patent Application No. 57-1450728)
) has a large maximum energy product, but the temperature coefficient of residual magnetic flux density (Br) is 0.07%/"C~
In order to obtain a temperature characteristic of 0.15%/℃, by applying this permanent magnet to the above-mentioned NMR-C1-, the device can be made smaller, the performance improved by 4J, and furthermore, The magnetic properties of this permanent magnet are particularly low at 2J below 0℃]
By using L/, the property that ab<high maximum energy product 1', I can be effectively utilized.

The above Fe-B-R permanent magnet contains 1 (where R is at least one kind of rare earth elements including Y) 8 atomic % to 3
0 atomic %, B 21 i child%...28+几）了%, F
e42 atomic% - 90 atomic% is the main component, and there is a permanent magnetic 6'c゛ whose main phase is a tetragonal phase, and resource-rich light rare earths, mainly M and Pr, are used as R (X, B, Fe
It is an excellent permanent magnet that has an extremely high energy product of -C of 25MGOθ or more with its main component.

Hereinafter, this invention will be explained in detail based on the drawings.

FIG. 1 is an explanatory diagram of a magnetic circuit used in the NMR-CT apparatus according to the present invention. Insert a circle Ii (type Sr ferrite magnet (11)) with an outer diameter of d into and harden it, and with a permanent magnet made of an integral piece of outer diameter, insert a magnetic pole piece (2) into one 9M of each of The opposite ends are connected by a yoke (3), and a strong magnetic field of 1 to 10 KG is generated in the gap (4) between the magnetic poles)'i and (2). It is configured to insert part or all of the human body into the body for diagnosis. A pair of magnetic pole pieces (2) have an outer diameter of D, and the entire surface of their opposing surfaces has a concave curved surface (5) (UJ5), in other words, one surface is a flat concave lens shape.
By making a pair of concave curved surfaces (5) face each other with a gap (4), a highly viscous, uniform and stable magnetic field is created.
I will be beaten.

J3, the concave curved surface (5) is formed with a radius of curvature R" The center point -C, 01, is on the vertical line of the 0 point.

In addition, as another example, the magnetic circuit for NMR-C shown in FIG.
(31(1)-%J)
l) and the other end of the buttock ai (3) with a permanent magnet (1)
In other words, the center part of the pair of yokes (3) is composed of Sr ferrite magnets (ill>), and the outer periphery is composed of Fe-El-R permanent magnets (li), making it an integrated permanent magnet. (1), a concave curved surface (5) curved at a constant curvature is formed on the entire opposing surface of the magnetic pole piece (2).
+/7 I 戊 (゛There is..

In this invention, a3-C, the magnetic circuit includes the following examples (3), including but not limited to, a gently curved concave curved surface having a single radius of curvature or multiple radii of curvature, Setting (
The permanent magnet of the magnetic circuit is the permanent VG of the central part fJ 3Ji.
L'' (D (I3 N) max is IOM (20e or more, permanent magnet near the peripheral part) ((311) max
It is preferable that r, +t20M GOe 2,
Mouth ([3t-1) may,'s ite is tOM G O
As for the combination materials of 2 types of permanent) 41 stones that are more than e, there is J/Luni' J magnet near the center A1, a rare earth Kobal 1 near the center, and a rare earth Kobal 1-41 stone around the center. system magnet.

FQ-BR-based magnets are most preferable, and the magnet\” method also uses
I4 is effective when 0.6D≦d≦0.9D.7 Also, for the curvature and shape of concave curved surfaces? People and permanent magnets
If you choose law, magnetism, and the size of the gap, it is important to note that the above range is valid.
・l-'), "F= R:" 4.4/ b・D, t1
≦3/1G・1! Here, []: 罎极J) Outer diameter, <; Curvature rF diameter, Support: Center yj of void 1-9, pressure end in one vertical direction from ζ0 to center point ○l.

Examples are described below.

2') Figure 1 [Small 41. In the magnetic circuit of S configuration, Wl is always
a I! ;'i's (1,3l 1 > IIIaX is 3
0MGOe available, outer diameter 1000 m:n, inner diameter 80
01i, lll ring-shaped Fe-5-R permanent magnet (
1a) inner diameter 81X and outer diameter 800mm T' (131
! ) 1llaX = /IM GOe's circle 9a
'! An integrated permanent magnet (using a magnet (ko), l) with a Sr metal magnet (1b) inserted = 1000nun
, R = 720 mm, 'l = 1! The case of the present invention in which the magnetic pole) 1 is placed on the right side of the concave curved surface of
4% magnet of the same composition using Oe's Sr magnet
Regarding the case of the comparative example in which J'i is placed,
When we measured the magnetic field distribution in the gap while keeping Lg at 700 mm, the magnetic field distribution result shown in Figure 3 was 49.

In addition, the A line in FIG. 3 indicates the case of the present defense, and the open line indicates the case of the comparative example.

As is clear from the results shown in Figure 3, in a spherical space with a radius (r) of 180 mm from the gap center point O, (B I
-1) In the case of the present invention in which two types of permanent magnets responsible for max are arranged, the uniformity is extremely high at 0.03%, compared to 0.2% in the comparative example. It can be seen that the magnetic field is extremely precise, uniform, and stable.

[Brief explanation of the drawing]

FIGS. 1 and 2 are longitudinal sectional views N of the magnetic field generating device according to the present invention. Figure 3 shows the magnetic circuit gap () of the example.
There is a magnetic field distribution map. DESCRIPTION OF SYMBOLS 1... Permanent magnet, 1a... Fe-El-It system permanent magnet, 111... Sr ferrite magnet, 2... Magnetic pole piece, 3... Yoke, 4... Air gap, 5... ...Concave curvature. Figure 1 Figure 2 Figure 3 Figure 1 (a) 6, 'j+': I ('+n-, 3, QQ'#I G Patent Office Commissioner Nasugi (1' Odono 1, Incident Display IIu W59 I ■Special 6'F Ifl+'i No. 399
625''i2, Name of the invention Magnetic field generator 3, Correction of JJI'1 Which relation: Address 22, Kitahama, Higashi-ku, Osaka-shi, J-[-] 22, SumiF~shi1-Kush1unk Name Sumitomo Special Metals Co., Ltd. 4, Agent) 5, Ne11j Positive λ・j Elephant 1, Mei III Zhan, page 1, lines 19 to 20, 1-1-4.
! Correct 1KGJ to 11-15KGJ. 2. Apply (t) apply to any subject in a circuit from line 11 to line 12 on page 7 of the specification.
If there is a combination U of 2+++ permanent magnets with different products, and the permanent magnets are not equipped with a Japanese-French piece, there is a 1,” is correct.

Claims (1)

[Claims] 1. In a magnetic field generating device that magnetically couples magnetic pole pieces facing each other with an air gap and at least one permanent magnet using a yoke to avoid generating a magnetic field in the air gap, each of the opposing surfaces of the magnetic pole pieces is formed into a concave curved surface. And the center of the permanent magnet (= near J is the permanent magnet at its periphery (8H) maxJ: 10
MGOeJ, small on u (B1-1) An amazing magnetic field generator hjl characterized by a permanent 46 stones with the max on the right.
a