JP4822722B2 - Magnetic shield wall and magnetic shield room - Google Patents

Description

  The present invention relates to a magnetic shield technique using a ferromagnetic material for the purpose of blocking magnetic noise and keeping a certain space magnetically clean.

  A magnetic shield technique using a magnetic material having a high magnetic permeability is a general technique. For example, as described in Patent Document 1 and Patent Document 2, the configuration basically encloses a target space with a plate-like magnetic body, and can be combined with a magnetic body or a plate. The shield performance is improved by preventing leakage from the joint portion of the cover with a cover or the like.

  At that time, the surface of the plate-like magnetic body is parallel to the wall surface of the magnetic shield room. According to the methods disclosed in Patent Document 1 and Patent Document 2 described above, it is difficult to obtain shielding performance as expected from the material characteristics, and the space is sealed with a magnetic material. There was a problem of lack of transparency.

  Patent Document 3 discloses a shield body in which plate-like magnetic bodies are installed at intervals in the plate thickness direction and can transmit air and light. Similarly, Patent Document 4 discloses a shield structure that transmits air and light. In Patent Document 3 and Patent Document 4, there is a description of a shield body that transmits air and light as described above, but there is no idea of joining magnetic body end portions or forming a closed magnetic circuit. And only the technique disclosed in Patent Document 4 is insufficient to obtain excellent shielding performance.

  Patent Document 5 discloses that a structure in which a closed magnetic path is formed of an electromagnetic steel plate is installed at the opening of a magnetic shield device. However, the shield wall surface and the surface of the plate-like magnetic body are parallel, and air or It does not lead to a structure that can transmit light.

JP-A-5-327263 JP-A-7-273484 JP-A-8-288688 JP 2002-164686 A JP-A-8-264350

  In order to provide a magnetic shield technology having excellent magnetic shielding performance while having air and light permeability, the present inventors have provided a plurality of magnetic elements made of one or more plate-like magnetic bodies. Have already proposed a method of forming a closed magnetic frame as a magnetic circuit by bringing the ends in the longitudinal direction close to each other and arranging a plurality of the magnetic frames at intervals in the plate-shaped magnetic plate thickness direction. (Japanese Patent Application 2003-72119).

  As for the technique proposed by the present inventors as described above, there is a point that is not sufficient for a completed technique when an actual shield structure is considered. This is because an actual shield room or shield structure has openings such as doors, windows, and wiring openings, and magnetic flux leakage from the openings deteriorates the overall magnetic shield performance. Even if these openings are present, it is necessary to provide excellent magnetic shielding performance.

  An object of the present invention is to provide a magnetic shielding technique having excellent magnetic shielding performance while having air and light permeability even in the state where the opening as described above exists.

  The present inventors have found that a magnetic frame made of a plate-like magnetic body has excellent magnetic shielding performance as long as a closed magnetic circuit is formed while bypassing the opening, and this is effectively utilized. By doing so, it was possible to achieve excellent magnetic shielding performance even in a magnetic shielding structure having an opening.

  It has been found from the following experiment that the magnetic material frame has excellent magnetic shielding performance as long as a closed magnetic circuit is formed while bypassing the opening. FIG. 1 shows the configuration of the shield body used for the test. A frame as shown in the plan view of Fig. 1 (a) is made of four directional magnetic steel sheets with a width of 25 mm and a length of 300 mm, with the rolling direction aligned in the length direction. The basic magnetic shield was stacked at 30 mm intervals. Further, to simulate the opening, a shield body having a gap of 80 mm on one side of the frame was produced as shown in FIG. A magnetic field was applied from the outside of the shield body using a Helmholtz coil in the direction of the arrow in the figure, and the magnetic field was measured at the central portion inside the shield body. As shown in FIG.1 (b), it turns out that the magnetic field in a center part becomes large by having an opening part, and shield performance deteriorates. By applying a magnetic field of 200 μT, the magnetic field in the basic shield body in FIG. 1A is attenuated to about 30 μT, but in FIG. 1B having an opening, it is about 40 μT. Next, in order to obtain excellent magnetic shielding performance with an opening, the shield body shown in FIG. 1 (c) is used for the test under the assumption that the magnetic circuit of the frame is closed. did. That is, a frame having a closed magnetic circuit formed by bending a strip-shaped grain-oriented electrical steel sheet 90 ° at four locations in the longitudinal direction to produce a pan-lid member and bypassing the opening. A four-stage shield was used. The shielding performance at this time is shown in FIG. 2, and the magnetic field at the center was almost the same as that in the reference FIG. It is about 30μT when 200μT magnetic field is applied.

  From the above, it was found that the magnetic material frame has excellent magnetic shielding performance as long as it forms a closed magnetic circuit while bypassing the opening. The present invention is a magnetic shield wall for realizing such a structure, and is a magnetic shield structure including the wall.

The present invention is summarized as follows.
(1) When an opening is provided in a magnetic shield wall constituting a magnetic shield structure in which a plurality of soft magnetic frames constituting a closed magnetic circuit surround a target space, the soft magnetic frame forms a wall on the opening. A magnetic circuit that is detoured and closed inside is configured, and the normal direction of the plate-like magnetic body constituting the soft magnetic frame included in the magnetic shield wall is perpendicular to the normal direction of the magnetic shield wall surface. The end of the plate-like magnetic body in the length direction is joined to another plate-like magnetic body adjacent in the length direction, and the joining is made by overlapping the plate-like magnetic bodies in the plate thickness direction. Magnetic shield wall characterized by that .
(2 ) When an opening is provided in a magnetic shield wall constituting a magnetic shield structure in which a plurality of soft magnetic frames constituting a closed magnetic circuit surround a target space, the soft magnetic frame forms an opening on a wall surface. A magnetic circuit that is detoured and closed inside is configured, and the normal direction of the plate-like magnetic body constituting the soft magnetic frame included in the magnetic shield wall is perpendicular to the normal direction of the magnetic shield wall surface. The end of the plate-like magnetic body in the length direction is joined to another plate-like magnetic body adjacent in the length direction, and the joining is made by abutting the end face of the plate-like magnetic body. Characteristic magnetic shield wall.
(3) in the opening, characterized in that said magnetic member not joined to the magnetic plate in the wall is installed (1) or (2) a magnetic shield wall according to.
(4) magnetic material in the opening is a magnetic shield wall according to (3) that the normal direction is the normal direction perpendicular to the installed magnetic plate of the magnetic shield wall .
( 5 ) A magnetic shield room including at least one shield wall according to any one of ( 1 ) to ( 4 ).

  According to the present invention, it is possible to provide a magnetic shield wall and a magnetic shield room that can block magnetic noise and maintain a space in a magnetically clean state.

  The present invention is described in detail below.

  The present invention is a magnetic shield wall forming a magnetic shield structure in which a magnetic circuit frame made of soft magnetic material constitutes a closed magnetic circuit and a plurality of magnetic material frames surround a target space. By installing the magnetic frame at intervals, air or light can pass through the gap. If there is an opening in the magnetic shield structure, the magnetic shield performance will not be impaired even if the magnetic circuit frame is configured so that the magnetic frame bypasses the opening and is closed. As described in the above. In the wall, all the plate-like magnetic bodies or the plate-like magnetic bodies that have undergone in-plane bending are installed with the normal direction perpendicular to the normal direction of the wall. By adopting such an arrangement, the single or aggregate of the plate-like magnetic bodies can be provided with a gap in the plate thickness direction in the wall. Air or light can pass through the voids formed in the walls.

Next, the end in the longitudinal direction of the plate-like magnetic body or the laminate of plate-like magnetic bodies is joined to another plate-like magnetic body or the plate-like magnetic body laminate except when it is at the end of the wall. It must be done. When the end of the magnetic body is at the end of the wall, it contributes to the formation of a closed magnetic circuit as a whole shield body having a joint with the magnetic body of the adjacent wall. On the other hand, if there is an end of a magnetic body inside the wall, it must be joined to another magnetic body or a collection of magnetic bodies and be a continuous collection of magnetic bodies inside the wall. FIG. 3 shows an example of a magnetic shield wall according to the present invention. (A) is an overall configuration diagram, and the bonding method is a plate-like magnetic body as shown in the enlarged view (b) in the thickness direction. A method of superimposing and a method of butting the end surfaces of the plate-like magnetic bodies as shown in the enlarged view (c) are possible. In any of the joining methods, the joining interval is preferably as narrow as possible. Moreover, although it is a reference example, the structure as shown to the enlarged view (d) which bent the plate-shaped magnetic body is also possible.

  When the continuous magnetic material assembly bypasses the opening, the opening is secured and can serve as a door, a window, or a wiring port. The fact that the shielding performance does not deteriorate even when the magnetic material bypasses the opening is as described above in the experimental results.

  When the opening is a door, better magnetic shielding performance can be obtained by disposing a magnetic body on the door. As shown in FIG. 4 (a), the magnetic material of the door part may have the surface of the magnetic material and the door surface parallel to each other, or air or light with the normal direction of each other as a right angle as shown in FIG. 4 (b). May be allowed to pass through.

  A magnetic shield room that contains a closed magnetic circuit by combining a shield wall as described above and a wall that does not have an opening but the basic magnetic arrangement is the same as that of the wall, combining three or more surfaces. can do. It is possible to provide a magnetic shield room having an opening while allowing air and light to pass therethrough and having excellent magnetic shielding performance.

  A soft magnetic material is used as the magnetic body of the magnetic shield wall and the magnetic shield room, and an electromagnetic steel sheet can be used as a suitable material. This is because the magnetic permeability is high and inexpensive. Further, by using a grain-oriented electrical steel sheet and making the rolling direction coincide with the longitudinal direction of the magnetic body, further excellent magnetic shielding performance can be obtained.

  A model imitating an MRI magnetic shield room as shown in FIG. 5 was prepared. The inside size of the model room was 2.8m wide x 3.5m long x 1.7m high, and an electromagnet was installed in the room. The shield performance of the room was evaluated by exciting the electromagnet under the condition that a magnetic field of 5mT was applied inside the wall D surface corresponding to the gantry surface, and measuring the magnetic flux density leaking outside the room. The basic configuration of the shield model room is as follows. A magnetic steel frame with an inner dimension of 2.8m x 3.5m was constructed from 50mm wide magnetic steel sheet, and 10 layers were stacked vertically at a pitch of 150mm. The magnetic steel sheets constituting the magnetic frame were laminated on the A, B, and D surfaces, and 12 laminated on the C surface. Furthermore, on the C and D planes, magnetic frames were also installed at a 150 mm pitch in the vertical direction. The magnetic steel sheets in the magnetic frame were laminated with 6 C faces and 12 D faces. On the ceiling and floor, 12 grain-oriented electrical steel sheets were pasted on the entire surface with the rolling direction aligned with the C plane. The electromagnetic steel sheets were joined at the corners in such a manner that the surfaces were joined in the thickness direction. For joining the electrical steel sheets on the ceiling and floor, both ends of the strip-shaped electrical steel sheets were bent by 90 ° to ensure surface joining.

  On the A side, an opening simulating a door as shown in FIG. 6 was installed. The situation around the opening (door) is shown in FIG. FIG. 7A shows an example of the present invention, in which a magnetic body frame bypasses the door portion. In the door, a collection of electrical steel sheets that have no joints with the walls is installed at a pitch of 150 mm. The distance between the magnetic body in the door and the magnetic body in the wall was 7 mm. FIG. 7B is a comparative example, and the end of the magnetic body frame in the wall is exposed at the door portion.

  FIG. 8 shows the distance dependence of the magnetic field from the surface of the door width center in each example. It is the value at 1m height. It can be seen that magnetic field leakage is small in the present invention.

It is a figure which shows the magnetic shield structure used for experiment, (a) is a basic shield body without an opening part, (b) is a shield body with an opening part, (c) is a figure which shows an opening part leakage countermeasure shield body, respectively. The figure which shows the magnetic shielding performance of each structure. It is a figure which shows the example of this invention magnetic-shield wall, (a) is a whole structure, (b), (c ) is a figure which shows the specific example of a joining system, respectively. In addition, (d) is a figure which shows the reference example of a joining system. (A), (b) is a figure which shows the example of this invention magnetic shield wall containing a door. The figure which shows the top view of a MRI magnetic shield model room. The side view of the A surface of an MRI magnetic shield model room. It is a figure which shows the enlarged view around a MRI magnetic shield model room door part, (a) is an example of this invention, (b) is a figure which shows a comparative example. (Part surrounded by a circle in Fig. 6) The figure which shows the leakage magnetic flux density of a MRI magnetic shield model room door part.

Claims (5)

When an opening is provided in a magnetic shield wall constituting a magnetic shield structure in which a plurality of soft magnetic frames constituting a closed magnetic circuit surround a target space, the soft magnetic frame bypasses the opening within the wall surface. The closed magnetic circuit is configured, and the normal direction of the plate-like magnetic body constituting the soft magnetic body frame included in the magnetic shield wall is set perpendicular to the normal direction of the magnetic shield wall surface, and longitudinal ends of the plate-shaped magnetic body is joined with the other plate-shaped magnetic bodies adjacent in the longitudinal direction, the Rukoto the bonding is not made by superposing the magnetic plate in the thickness direction Characteristic magnetic shield wall. When an opening is provided in a magnetic shield wall constituting a magnetic shield structure in which a plurality of soft magnetic frames constituting a closed magnetic circuit surround a target space, the soft magnetic frame bypasses the opening within the wall surface. The closed magnetic circuit is configured, and the normal direction of the plate-like magnetic body constituting the soft magnetic body frame included in the magnetic shield wall is set perpendicular to the normal direction of the magnetic shield wall surface, And the length direction edge part of the said plate-shaped magnetic body is joined with the other plate-shaped magnetic body adjacent to a length direction, and this joining is made | formed by abutting the end surface of a plate-shaped magnetic body, It is characterized by the above-mentioned. Magnetic shield wall. Said the opening, the magnetic plate and the magnetic shield wall according to claim 1 or 2 magnetic material not bonded is characterized in that it is installed in the wall. The magnetic body in the opening, a magnetic shield wall according to claim 3, the normal direction, characterized in that a normal line direction perpendicular to the installed magnetic plate of the magnetic shield wall. Magnetic shield room comprising at least one shield wall according to any one of claims 1 to 4.

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