JPH0377173A - Magnetic shielding method - Google Patents

Abstract

PURPOSE:To confirm the shielding effect and to select an optimum execution process before execution of the work by turning a shielding matter into a model and producing a primary shielding matter plan so as to satisfy the requested shielding conditions to correct the shielding matter plan via a computer. CONSTITUTION:A primary shielding matter plan which satisfies the required shielding characteristic is studied based on the data given from the users. Then a magnetic field is calculated by means of a finite element method applying a computer. The decided primary shielding matter plan is defined as a finite element model in consideration of the magnetic symmetricalness. Then the magnetic environment conditions are grasped for the site where a shielding matter is installed. Thus a shielding environment is set. These data are inputted to the computer and the inside/outside magnetic field distributions of the pri mary shielding matter plan are calculated by the computer via the finite element method. These calculation results are evaluated and studied for production of the secondary and tertiary shielding matter plans, etc. Thus it is possible to decide an optimum shielding structure and to attain the reduction of cost.

Description

[Detailed Description of the Invention] (Purpose) The present invention has recently been developed regarding magnetic shielding methods, and it is important to prevent malfunctions and measurement problems caused by electromagnetic waves and magnetism in precision electronic and electrical equipment such as medical equipment and OA equipment. As a result, construction of shield rooms is increasing.

When applying electromagnetic shielding, the magnetic field is mainly in the high frequency range, so highly conductive materials such as aluminum or copper are used, but in the case of magnetic field shielding, the magnetic field is mainly in the low frequency range, so amorphous metals are used. Highly permeable materials such as permalloy were used and were treated separately from electromagnetic shielding.

In particular, in MRI and computer rooms, consideration should be given to base manufacturer owners (5G or less), magnetic field shielding to the limit (0.5G or less) that does not cause computer malfunction, and the influence of electromagnetic waves (e.g. MRI 1 to 100 Mllz), it is necessary to provide a shield to prevent misdiagnosis. However, until now, shield construction has mainly been based on experience, making it impossible to optimally determine material selection, amount used, and shield structure, and designs have been carried out with considerable safety in mind, leading to increased costs.

Therefore, it is an object of the present invention to solve the above-mentioned problems of the prior art.

(Structure) In order to achieve the above-mentioned object, the present invention is directed to the creation of a primary shielding scheme that can satisfy the required shielding characteristics,
Finite element modeling of the next shield plan, determination of the magnetic environment conditions at the site where the first shield plan is installed, calculation of the magnetic field distribution outside the guide of the first shield body using the finite element method, We provide a magnetic shielding method that determines the optimal shielding structure by modifying the primary shielding structure based on calculations, and designs and manufactures it.

That is, based on data from the user, a primary shielding scheme that satisfies the required shielding characteristics is examined. Items to consider include the shape, dimensions, material, and amount of the shield body used. Next, the magnetic field is calculated using the finite element method using a computer.

The determined primary shield structure is made into a 1/8.1/4.1/2 or 1/1 finite element model in consideration of its magnetic symmetry. Understand the magnetic environmental conditions at the site where the shield is installed, that is, convert the generated magnetic field, external magnetic field, and magnetic field distribution into data, and add it to the analysis conditions along with the characteristic data of the shield material.

In other words, configure the shield environment.

Input this data into the computer. Using the finite element method, the magnetic field distribution inside and outside the primary shield structure is calculated by computer.

Evaluate and discuss the obtained magnetic field calculation results. When a better shield is desired by changing the shield structure, or when the required shield characteristics are not sufficient, try again.
Created the second shield plan, third shield plan, etc.
Repeat the above procedure.

This can be displayed as a chart as shown below. This makes it possible to determine the optimal shield structure and also consider cost reduction.

(Experiment Example 1) A conventional shield chamber is shown in FIGS. 1 and 2. shield t
rJi1 is 0.35 along both walls of the MRI room and imaging room.
The shield plate 2 is made of 24 stacked silicon steel plates with a thickness of 5 mm thick, and the shield plate 2 is made of 5 stacked sheets of the same material. It was said that by creating such a shielded room, it would be possible to make the imaging room less than 0.5G and the MRI operating room less than 5G.

The shield chamber obtained according to the method of the present invention is shown in FIGS. 3 and 4. Five 0.35 mm silicon steel plates are stacked on top of each other, and the shield plate 3 on the photography room side and the other shield plate 4 are connected to each other. A distance of 1200 mm is provided between the two, and a shield plate is not required on the photographing room side.

The magnetic field distribution is as shown, and chamber 5 can be used as an MRI operating room. By changing the shape, we were able to reduce the amount used and reduce costs.

(Experimental Example 2) Next, an example of a shield using an iron plate is shown in FIGS. 5 and 6. In order to reduce the number of shield plates used, this example was further improved by the magnetic shielding method of the present invention, resulting in the selection of silicon steel plates and the shield structure shown in FIGS. 7 and 8. This eliminated the need for floor and ceiling construction, resulting in significant cost reductions. “Type E・
T31 F9 E (Experimental Example 3) Fig. 9 is an example in which a shield structure was determined in a place where continuous application of magnetic material was not possible. As a result of considering a shield structure to prevent 5G magnetic field from leaking into the conference room on the second floor, 30
When the rise was 0 mm and the rise was 200 mm or less or 300 m or more, the characteristic evaluation of magnetic force leakage of 5 G or more could be predicted by the computer.

(Effects) In the present invention, the shield body can be modeled and the primary shield body plan can be modified by computer so as to satisfy the required shielding conditions, so that the shielding effect can be confirmed before construction and the optimal construction can be selected.

[Brief explanation of drawings]

FIG. 1 is a vertical cross-sectional view of a conventional shield chamber, FIG. 2 is a cross-sectional view thereof, and FIG. 3.5-9 is a vertical cross-sectional view and a cross-sectional view showing each side of the present invention. Figure 48 is among those figures: 4... Sea 111 move.

Claims (1)

[Claims] Creation of a first shield plan that can satisfy the required shielding characteristics, finite element modeling of the first shield plan, first
Determining the magnetic environment conditions at the site where the next shield plan will be installed, calculating the magnetic field distribution outside the guide of the first shield using the finite element method, and modifying the first shield plan based on the calculations. A magnetic shielding method that determines the optimal shielding structure, designs and manufactures it.