JPH05291779A - Shield box for measuring fluctuation magnetic field shield performance - Google Patents

Abstract

PURPOSE:To obtain a shield box for measuring fluctuation magnetic field shield which can perform various kinds of shield experiments with one device. CONSTITUTION:An opening 2 for mounting a material to be tested and a hole 3 for mounting the material to be tested are provided on one surface of a hexahedron consisting of ferromagnetic material plate materials such as permaloy, amorphous, and silicon steel and then an opening 4 for installing sensor, a door 5 for covering the opening, and an opening 6 for taking out cable are provided on the other surface of the hexahedron.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable magnetic field shield performance measuring shield box capable of evaluating the shielding performance of various magnetic materials against varying magnetic fields from various angles.

[0002]

2. Description of the Related Art Recently, many devices installed in intelligent buildings and precision factories are sensitive to magnetism. For example, the electron microscope is designed to suppress the magnetic fluctuation component to 2 mG (milligauss) or less in order to increase the sensitivity. On the other hand, in the present everyday environment, various magnetic sources are present nearby.
For example, when a large magnetism is generated around trains, cars, power lines, etc., when building a building near them,
There is a fluctuating magnetic field of about several tens of mG. The precision equipment installed therein will be exposed to a magnetically adverse environment, and it will not be possible to exhibit the performance of the equipment satisfactorily.

As a method of coping with this, the perimeter of the equipment or the entire room in which the equipment is installed is made of permalloy amorphous.
A method of installing a magnetically shielded room (box) that is surrounded by a ferromagnetic material such as a silicon steel plate to prevent invasion of magnetism by absorbing an intruding magnetic field from the outside is adopted. The above-mentioned ferromagnetic material has excellent magnetic characteristics of 1 G (Gauss) or less, exhibits high magnetic permeability, and can efficiently shield magnetism even in a small magnetic field such as a fluctuating magnetic field.

However, although such a ferromagnetic material has a high magnetic shield performance inherent to the material, many problems arise when it is formed into a magnetic shield room shape. For example, a large area requires a joint, and an opening such as a door or a window is also required. A large leakage magnetic field is generated from such a place. In addition, the magnetic shield performance greatly changes depending on the type and thickness of the material and the type of the target magnetic field (size, frequency, direction, etc.).

Therefore, in designing a magnetic shield room for a varying magnetic field, various data regarding the magnetic shield are required. Computer simulation by magnetic field analysis is also used to collect data, but it is often obtained by experiment. Shielding experiments against fluctuating magnetic fields include those that require the original shielding performance of the material and those that require shielding performance in various shapes.

The original shielding performance of the material is obtained by a method in which a ring-shaped sample is prepared, a current is applied to a coil wound around the circumference to give a magnetic field in the circumferential direction, and the magnetic flux density is measured by a search coil. The sample is about Φ45mm, so the experiment can be done relatively easily. On the other hand, the shield performance in various shapes is performed by making a model of each shape and placing it in a magnetic field created by a coil to measure the performance. However, this method requires a lot of cost and labor to create a model, so a cylinder (for example, Φ10 cm × length 3
A simple method is often used in which the internal magnetic field is measured by placing (about 0 cm) in the magnetic field. If a joint is provided on the cylinder, magnetic leakage from the joint can be confirmed.

[0007]

The above-mentioned prior art has the following problems. Generating models of various shapes requires a lot of cost and labor. Therefore, it is not possible to easily change the position of the opening and the position of the joint,
Many kinds of data cannot be collected. The smaller the model, the less material costs, but the same effort, and the less accurate the measurement.

On the other hand, the simple method using a cylinder has a shape greatly different from an actual magnetically shielded room, it is not possible to incorporate a shape element, and it is not possible to grasp the magnetic field distribution. In addition, there is a problem in terms of accuracy due to magnetic wraparound. As described above, in the conventional model for measuring the fluctuating magnetic field shield performance, it is difficult to evaluate the shielding performance with respect to the fluctuating magnetic field in a large number and accurately, and it has been desired that the shield performance can be easily and accurately measured.

An object of the present invention is to solve the above-mentioned problems in the prior art and to provide a shield box for measuring a varying magnetic field shield, which enables various shield experiments to be conducted with one apparatus.

[0010]

[Means for Solving the Problems] (1) A hexahedral box in which plate materials made of a ferromagnetic material such as permalloy, amorphous silicon steel, etc. are firmly joined without magnetic resistance so that there is no magnetic field leakage from the joints. Make an opening and a mounting (screw) hole for mounting test materials of various shapes on one surface of the box. (2) On the other side of the box, a sensor installation opening that allows various operations inside the box is provided, and it can be easily opened and closed, and when it is closed, it is mechanically pressed, Install a door that can prevent magnetic field leakage. (3) A cable connecting the inside and the outside of the box is penetrated, and an opening for taking out the cable is provided so that the leakage of the magnetic field can be suppressed as much as possible.

[0011]

The plate material made of a ferromagnetic material such as permalloy, amorphous, silicon steel or the like, which constitutes the shield box, prevents an external fluctuating magnetic field from entering the inside of the box. By attaching and replacing test materials of various materials and shapes in the test material mounting openings provided on one surface of the shield box, various shield performances against a fluctuating magnetic field can be measured.

This shield box is installed in the magnetic field space created by the coil, and the shield performance is evaluated by measuring the internal magnetic field. The difference in the measured values for each test material is the shield performance for that test material.
As the test material, materials having various shapes are attached, but, for example, materials having gaps or openings, and materials having different thicknesses or kinds of materials can be used. By changing the magnitude, frequency, and distribution of the magnetic field generated from the coil, and changing the angle of the shield box with respect to the magnetic field, it is possible to deal with any fluctuating magnetic field.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS. In the figure, 1 is permalloy, amorphous,
A plate material of a ferromagnetic material such as silicon steel (hereinafter referred to as a permalloy plate), 2 is an opening for mounting a test material, 3 is a mounting hole for a test material, 4 is a sensor installation opening, 5 is a door of a sensor installation opening 4, 6 is an opening for taking out a cable, 7 is a test material, 8
Is a test material mounting hole provided on the outer periphery of the test material 7, 9 is a second test material mounting opening provided in the test material 7, 11 is a test material mounting hole provided around the opening 9, and 12 is a second test Material, 13 is a test material mounting hole provided on the outer peripheral portion of the second test material 12, and 10 is a shield box (whole). 14
Is a patch plate made of the same material as the plate material 1, 15 is a non-magnetic plate material, 16 is a half-divided permalloy plate, 17 is a cable hole provided in the half-divided permalloy plate 16, 18 is a cable, and 20 is 1
A pair of Helmholtz coils, 21 is a computer, 22
Is an information line, 23 is a gauss meter, 24 is a mount of the Helmholtz coil 20, 25 is a rotary table of the shield box 10, 26 is a mount 24, an installation base for mounting the rotary table and the like, and 27 is a sensor.

FIG. 1 is an overall view of a shield box according to the present invention. The shape is a hexahedron, and has an opening 2 for mounting a test material on the front surface. Further, the sensor installation opening 4, the door 5 and the cable extraction opening 6 are provided on the adjacent surface thereof. A test material mounting hole 3 is provided on the four circumferences of the test material mounting opening 2, and the test material 7 and the shield box 10 are mounted in close contact with each other by screwing without a gap between the contact surfaces.
It is effective that the pitch of screwing, that is, the interval between the test material mounting holes 3 is 50 mm or less, and the zigzag patterns are arranged. The position of each opening is good for various work,
When arranged as shown in the figure, it is desirable to be able to grasp the degree of magnetic field leakage from the contact surface in comparison with the flat plate on the opposite surface.

The material of the plate material 1 constituting the shield box 10 may be any material having a high magnetic permeability, such as permalloy, amorphous, silicon steel, etc., but in this embodiment, PC permalloy having the best magnetic shielding property is used. It will be explained on the assumption. PC permalloy is an alloy containing about 78% nickel, has a very high magnetic permeability in a low magnetic field, and is optimal for shielding a fluctuating magnetic field.

Usually, the test material 7 is mounted in a size that covers the test material mounting opening 2, but depending on the material, a large size cannot be manufactured. In that case, after the small second test material 12 is firmly attached to the test material 7 with screws by the test material mounting holes 11 and 13, the test material mounting hole 3 is provided together with the test material 7.
Attach it to the shield box with screws with 8. FIG. 3 shows this state.

The permalloy has a width of about 330 mm on the market because of its manufacturing equipment. Therefore, to make a 1m square plate, several plates had to be joined together. In this case, it is necessary to devise a method for suppressing the leakage of the magnetic field from the seam. 4 to 6 show an example of a method of joining permalloy plates. In FIG. 4, a permalloy pad plate 14 extending over two permalloy plates 1 is fixed with screws. The width of the contact plate 14 and the pitch of the screws vary depending on the thickness of the permalloy plate 1, but if the thickness is 1.5 mm, the width is 100 mm and the pitch of the screws is about 50 mm.

FIG. 5 shows a permalloy pad plate 14 fixed by spot welding. In this case, it is necessary to perform the magnetic annealing again in order to recover the deterioration of the magnetic properties due to the welding. The width of the patch plate 14 and the pitch of spot welding vary depending on the thickness of the permalloy plate 1, but the thickness is 1.5
If it is mm, a width of 100 mm and a pitch of 30 to 50 mm are required.

FIG. 6 shows a structure obtained by butt fusion welding. In this case, it is necessary to remove the strain by a leveler together with the magnetic annealing. Therefore, it is difficult with a large size. As shown in FIG. 7, the test material 7 is attached with a screw to a non-magnetic pad plate 15 having a tap attached around the opening 2 of the permalloy plate 1 by argon welding. In order to suppress the leakage of the magnetic field from the contact surface, the contact width is about 50 mm, and the screwing pitch is 50 mm.

As shown in FIG. 8, the contact surfaces of the permalloy plate forming the door 5 of the sensor installation opening 4 and the permalloy plate forming the main body of the shield box 10 are superposed in order to suppress magnetic field leakage from the contact surfaces. Take a width of about 50 mm,
When the door 5 is closed, it is mechanically pressed to bring them into close contact. For mechanical pressing, a method using several fasteners provided in the periphery can be considered.

The construction in the vicinity of the cable extraction opening 6 will be described with reference to FIGS. The end of the cable is a connector (not shown) and is sized larger than the diameter of the cable 18. Therefore, the opening 6 for taking out the cable that allows the connector to pass through is provided in the shield box 10.
The hole 17 for a cable having a diameter of the cable 18 is made of the half-permalloy plate 16 in advance. The half-divided permalloy plate 16 is a non-magnetic pad plate 15 having a tap attached around the opening 6 by argon welding,
It can be attached with screws.

The shield box 10 described above is
The flat plate portion of permalloy, which is expected to have a direct shield effect, and the portion other than the backing plate which prevents the leakage of the magnetic field from the gap, must be made of a non-magnetic material such as stainless steel in order to eliminate the influence of magnetism. Further, in consideration of the eddy current effect due to the fluctuating magnetic field, a non-conductive material such as bakelite or FRP is desirable. As a result, it is possible to understand the pure shield effect.

Next, the shield box 10 according to the present invention.
The method of using will be described with reference to FIG. The shield box 10 is installed in the magnetic field space created by the Helmholtz coil 20 via the rotary table 25 and the installation table 26. The installation table 26 prevents the magnetic field from being disturbed by the reinforcing bars on the floor, and lifts the entire apparatus to the upper part. The rotary table 25 adjusts the direction and height of the shield box with respect to the Helmholtz coil 20.

The size of the shield box 10 is 1 / outer diameter of the Helmholtz coil 20 because of the homogeneity of the magnetic field.
If the outer diameter of the Helmholtz coil is 2 m, the size is 1 m or less. Further, the magnetic field inside is measured by the sensor 27 of the Gauss meter 23 installed in the shield box 10, and the data is sent to the computer 21 through the information line 22.

[0025]

The shield box for measuring the fluctuating magnetic field shield performance according to the present invention comprises a hexahedron made of a plate material made of a ferromagnetic material such as permalloy, amorphous, silicon steel, etc., on one surface of which a test material mounting opening and the periphery of the same are attached. The following effects are obtained by providing the test material attachment hole arranged in the above, and providing the sensor installation opening, the door covering the opening, and the cable extraction opening on the other surface of the hexahedron.

As a basic model, only one hexahedron shield box needs to be made, and the cost and labor required for the experiment can be greatly reduced. In addition, by changing the size of the gap, the shape of various joints, the size and position of the opening, etc. in the shape of the test material attached to one surface, it is possible to grasp the varying magnetic field shield characteristics for various elements of the shield room from all angles. Differences due to differences in materials and thickness can be easily obtained.

Further, since it is possible to measure the internal magnetic field distribution with a size of about 1/10 of the actual size, it is possible to obtain highly accurate information as compared with the conventional device. By feeding back this result to the computer simulation, it becomes possible to accurately simulate the shield characteristics in the entire shape of the magnetic shield room.

[Brief description of drawings]

FIG. 1 is a perspective view of an embodiment of a shield box of the present invention.

FIG. 2 is a configuration diagram showing a method of measuring a varying magnetic field shield performance using a shield box according to the present invention.

FIG. 3 is a front view of a test material to which a second test material is attached.

FIG. 4 is a cross-sectional view showing a joined state of permalloy plates by screwing.

FIG. 5 is a cross-sectional view showing a joined state of permalloy plates by spot welding.

FIG. 6 is a cross-sectional view showing a joined state of permalloy plates by butt fusion welding.

FIG. 7 is a cross-sectional view of a test material attachment portion.

FIG. 8 is a cross-sectional view showing a contact state between a door of the sensor installation opening and a peripheral portion thereof.

FIG. 9 is a front view of a half-permalloy plate that covers a cable extraction opening.

10 is a cross-sectional view taken along the line AA of FIG.

[Explanation of symbols]

 1 Permalloy plate 2 Test material mounting opening 3 Test material mounting hole 4 Sensor installation opening 5 Door 6 Cable extraction opening 10 Shield box

Claims (1)

[Claims] 1. An opening for mounting a test material and a test material mounting hole arranged around the same are provided on one surface of a hexahedron made of a plate material made of a ferromagnetic material such as permalloy, amorphous, silicon steel, and the like. A shield box for measuring the varying magnetic field shield performance, characterized in that a sensor installation opening, a door covering the opening and a cable extraction opening are provided on the other surface of the hexahedron.