JP5987342B2 - Magnetic shield device, demagnetizing method and program for magnetic shield device - Google Patents

Description

  The present invention relates to a multi-layer magnetic shield device that shields an external magnetic field, a demagnetizing method thereof, and a program.

  A magnetic shield is known as a means for shielding an external magnetic field such as geomagnetism when measuring a weak magnetic field emitted from a brain or a heart. For example, Patent Document 1 discloses a magnetic shield container having a plurality of outer walls formed of a ferromagnetic material. Patent Document 2 discloses a magnetic shield room having a three-layer wall surface formed of a high permeability alloy. Since these magnetic shield containers and magnetic shield rooms have a plurality of layers of walls, an external magnetic field can be further shielded.

Japanese Patent Laid-Open No. 5-114796 JP 2008-53499 A

  However, in the case of the magnetic shield container disclosed in Patent Document 1 and the magnetic shield room disclosed in Patent Document 2, the ferromagnetic material of each layer is magnetized, so that the shielding rate of the magnetic field is reduced in a static magnetic field. There's a problem.

  An object of the present invention is to suppress a decrease in shielding rate due to magnetization in a magnetic shield having a multilayer structure.

  The present invention provides a shield portion having at least a first cylindrical body made of a magnetic material and a second cylindrical body arranged in the hollow of the first cylindrical body and made of a magnetic material, There is provided a magnetic shield device characterized by having at least a first demagnetizing section for demagnetizing one cylinder and a second demagnetizing section for demagnetizing the second cylinder. According to this configuration, in a magnetic shield having a multilayer structure, it is possible to suppress a decrease in shielding rate due to magnetization.

  The magnetic shield device further includes a control unit that controls at least the first demagnetization unit and the second demagnetization unit, and the control unit starts demagnetization by the first demagnetization unit. The demagnetization by the second demagnetizing unit may be started. According to this configuration, the second cylinder can be demagnetized in a low magnetic field environment in the first cylinder by demagnetizing the second cylinder after the first cylinder is demagnetized. The body can be in a lower magnetic field environment.

  In addition, the present invention provides a shield part having at least a first cylindrical body made of a magnetic body and a second cylindrical body that is arranged in the hollow of the first cylindrical body and made of a magnetic body, Control at least a first demagnetizing section that demagnetizes the first cylinder, a second demagnetizing section that demagnetizes the second cylinder, and the first demagnetizing section and the second demagnetizing section. In the magnetic shield device having the control unit, the control unit starts the demagnetization by the first demagnetization unit, and the control unit performs the second demagnetization after the first step. A demagnetizing method for a magnetic shield device, comprising: a second step of starting degaussing by the unit. According to this configuration, in the magnetic shield having a multilayer structure, the second cylinder is demagnetized in the low magnetic field environment in the first cylinder by demagnetizing the second cylinder after the first cylinder is demagnetized. Since the demagnetization can be performed, the second cylindrical body can be set to a lower magnetic field environment.

  In addition, the present invention provides a shield part having at least a first cylindrical body made of a magnetic body and a second cylindrical body that is arranged in the hollow of the first cylindrical body and made of a magnetic body, Control at least a first demagnetizing section that demagnetizes the first cylinder, a second demagnetizing section that demagnetizes the second cylinder, and the first demagnetizing section and the second demagnetizing section. In a magnetic shield device having a computer, a first step for causing the computer to start degaussing by the first degaussing unit, and a first step for starting demagnetization by the second degaussing unit after the first step. A program for executing at least the two steps is provided. According to this configuration, in the magnetic shield having a multilayer structure, the second cylinder is demagnetized in the low magnetic field environment in the first cylinder by demagnetizing the second cylinder after the first cylinder is demagnetized. Since the demagnetization can be performed, the second cylindrical body can be set to a lower magnetic field environment.

It is a figure showing composition of magnetic shield device 10 concerning one embodiment of the present invention. 2 is a perspective view of a shield part 1. FIG. 2 is a front view of a shield part 1. FIG. 2 is a diagram illustrating a configuration of a control circuit 6. FIG. It is a flowchart which shows the degaussing process which concerns on one Embodiment. It is a modification of the shield part 1. FIG.

(1) Embodiment FIG. 1 is a diagram showing a configuration of a magnetic shield device 10 according to an embodiment of the present invention. As shown in the figure, the magnetic shield device 10 includes a shield unit 1, a first degaussing coil 2, a second degaussing coil 3, a first drive circuit 4, a second drive circuit 5, and a control circuit 6. (An example of a control unit). The shield unit 1 is a magnetic shield made of a ferromagnetic material and shields an external magnetic field.

  FIG. 2 is a perspective view of the shield part 1. FIG. 3 is a front view of the shield unit 1 (viewed in the + y direction). As shown in the figure, the shield part 1 has an outer cylinder 11 (an example of a first cylinder) and an inner cylinder 12 (an example of a second cylinder). The outer cylinder 11 is a cylindrical member made of a ferromagnetic material. The inner cylinder 12 is a cylindrical member that is installed in the hollow of the outer cylinder 11 and is made of a ferromagnetic material. The inner cylinder 12 is disposed so as to be concentric with the outer cylinder 11. In addition, the symbol which drawn the two line segments which cross | intersect in a white circle shown in FIG. 3 has shown the arrow which goes to a back | inner side from a paper surface front side.

  The outer cylinder 11 has a predetermined length L in the axial direction, the inner cylinder 12 has a predetermined length L in the axial direction or a shorter length, and the inner diameter of the outer cylinder 11 is the inner cylinder. It is larger than 12 outer diameters. A spacer (not shown) is arranged in the space between the outer cylinder 11 and the inner cylinder 12, and the inner cylinder 12 is supported by this spacer. This spacer is, for example, polystyrene foam. The material of the outer cylinder 11 and the inner cylinder 12 is, for example, permalloy, iron, chromium, cobalt-based amorphous, or a ferrite sintered body.

  The first degaussing coil 2 is wound around the outer cylinder 11 and demagnetizes the outer cylinder 11 by generating an alternating magnetic field. The second degaussing coil 3 is wound around the inner cylinder 12 and demagnetizes the inner cylinder 12 by generating an alternating magnetic field. The first drive circuit 4 is connected to the first degaussing coil 2 and allows an alternating current to flow from the power source (not shown) to the coil. The second drive circuit 5 is connected to the second degaussing coil 3 and causes an alternating current to flow from the power source (not shown) to the coil.

  The first demagnetizing coil 2 and the first drive circuit 4 are examples of the “first demagnetizing unit” according to the present invention. The second degaussing coil 3 and the second drive circuit 5 are examples of the “second demagnetizing unit” according to the present invention. The control circuit 6 is connected to the first drive circuit 4 and the second drive circuit 5 and controls them.

  FIG. 4 is a diagram showing a configuration of the control circuit 6. As shown in the figure, the control circuit 6 includes a CPU (Central Processing Unit) 61, a ROM (Read Only Memory) 62, a RAM (Random Access Memory) 63, a timer 64, an input unit 65, and an output. Part 66. Each component is connected to each other via a bus.

  The CPU 61 reads out and executes the control program 621 stored in the ROM 62, thereby realizing demagnetization processing described later. The RAM 63 provides a work area when the CPU 61 executes the control program 621. The timer 64 includes an oscillation circuit having a crystal resonator, and measures time based on an oscillation signal output from the oscillation circuit. The input unit 65 receives an operation signal instructing demagnetization of the shield unit 1 via an operation unit (not shown) (for example, a button). The output unit 66 outputs a drive signal or a drive stop signal to the first drive circuit 4 and the second drive circuit 5.

  FIG. 5 is a flowchart showing the degaussing process according to the present embodiment. When the operation signal is received by the input unit 65, the CPU 61 executes the control program 621 to realize the operation.

  In step S <b> 1 of the operation, the CPU 61 outputs a drive signal to the first drive circuit 4 via the output unit 66. When the first drive circuit 4 receives the drive signal, the first drive circuit 4 starts providing an alternating current to the first degaussing coil 2. The first degaussing coil 2 receives an alternating current to generate an alternating magnetic field and demagnetize the outer cylinder 11. Further, the CPU 61 starts measuring time by the timer 64.

  Next, the CPU 61 determines whether or not a predetermined degaussing time has elapsed (step S2). Specifically, the CPU 61 compares the degaussing time T1 that is predetermined for the outer cylinder 11 and stored in the ROM 62 with the elapsed time measured by the timer 64. As a result of this comparison, when the elapsed time is less than the demagnetization time T1 (step S2; NO), the CPU 61 determines that the predetermined demagnetization time has not elapsed and stands by. On the other hand, when the elapsed time has reached the demagnetizing time T1 (step S2; YES), the CPU 61 determines that the predetermined demagnetizing time has elapsed, and performs the process of step S3.

  In step S <b> 3, the CPU 61 outputs a drive stop signal to the first drive circuit 4 via the output unit 66. When receiving the drive stop signal, the first drive circuit 4 stops providing the alternating current to the first degaussing coil 2. As a result, the demagnetization with respect to the outer cylinder 11 is completed. In addition, the CPU 61 resets the timer 64.

  Next, the CPU 61 outputs a drive signal to the second drive circuit 5 via the output unit 66 (step S4). When receiving the drive signal, the second drive circuit 5 starts providing an alternating current to the second degaussing coil 3. When the second degaussing coil 3 is provided with an alternating current, it generates an alternating magnetic field and demagnetizes the inner cylinder 12. Further, the CPU 61 starts measuring time by the timer 64.

  Next, the CPU 61 determines whether or not a predetermined degaussing time has elapsed (step S5). Specifically, the CPU 61 compares the demagnetizing time T <b> 2 predetermined for the inner cylinder 12 and stored in the ROM 62 with the elapsed time measured by the timer 64. As a result of this comparison, when the elapsed time is less than the demagnetization time T2 (step S5; NO), the CPU 61 determines that the predetermined demagnetization time has not elapsed and stands by. On the other hand, when the elapsed time has reached the demagnetizing time T2 (step S5; YES), the CPU 61 determines that the predetermined demagnetizing time has elapsed, and performs the process of step S6.

In step S <b> 6, the CPU 61 outputs a drive stop signal to the second drive circuit 5 via the output unit 66. When receiving the drive stop signal, the second drive circuit 5 stops providing the alternating current to the second degaussing coil 3. As a result, the demagnetization with respect to the inner cylinder 12 is completed. In addition, the CPU 61 resets the timer 64.
The above is the description of the demagnetization process according to the present embodiment.

  According to the magnetic shield device 10 according to the present embodiment described above, demagnetization of the outer cylinder 11 exposed to an external magnetic field is first performed. As a result, the magnetic field in the space inside the outer cylinder 11 becomes smaller than the magnetic field in the external space. Next, the inner cylinder 12 is demagnetized. Since the inner cylinder 12 is installed in a space inside the outer cylinder 11, the demagnetization of the inner cylinder 12 is performed in a magnetic field space smaller than the external space. As a result, the magnetic field in the inner cylinder 12 is smaller than that in the case of not having the configuration of the actual form.

(2) Modifications The above embodiment may be modified as follows. The following modifications may be combined with each other.

(2-1) Modification 1
In the above embodiment, the radial cross section of each cylindrical body constituting the shield part 1 is circular, but this shape may be an ellipse or a polygon. Moreover, in said embodiment, the shield part 1 may have a structure of three or more layers. Specifically, for example, a cylinder may be further provided outside the outer cylinder 11.

  FIG. 6 is a cross-sectional view of the shield portion 1 </ b> A having the outermost cylinder 13 on the outer side of the outer cylinder 11. The cross-sectional view is a cross-sectional view taken along the center line of the shield portion 1A. As shown in FIG. 1, the shield portion 1 </ b> A includes an outer cylinder 11, an inner cylinder 12, and an outermost cylinder 13. The outermost cylinder 13 is a cylindrical member made of a ferromagnetic material. The outer cylinder 11 is installed in the hollow of the outermost cylinder 13. Further, the outer cylinder 11 is disposed so as to be concentric with the outermost cylinder 13.

  The axial length of the outermost cylinder 13 may be equal to or longer than the length of the outer cylinder 11. Further, the inner diameter of the outermost cylinder 13 is larger than the outer diameter of the outer cylinder 11. A spacer (not shown) is disposed in the space between the outermost cylinder 13 and the outer cylinder 11, and the outer cylinder 11 is supported by this spacer. This spacer is, for example, polystyrene foam. The material of the outermost cylinder 13 is, for example, permalloy, iron, chromium, or cobalt-based amorphous, or a ferrite sintered body.

  As described above, in the case of a configuration further including a cylinder on the outer side of the outer cylinder 11, a demagnetizing coil and a drive circuit may be provided on the cylinder as well as the outer cylinder 11 and the inner cylinder 12. When the degaussing process is performed, the demagnetization is performed in order from the outermost cylinder.

  In the example shown in FIG. 6, the relationship between the outermost cylinder 13 and the outer cylinder 11 is an example of the relationship between the “first cylinder” and the “second cylinder” according to the present invention. The relationship between the outer cylinder 11 and the inner cylinder 12 is an example of the relationship between the “first cylinder” and the “second cylinder” according to the present invention. In addition, in the example of FIG. 6, although it has shown about the structure which has a cylinder of 1 layer on the outer side of the outer cylinder 11, it is good also as a structure which has a cylinder of 2 layers or more.

  As shown in FIG. 6, when the shield part 1 has a structure of three or more layers, the demagnetizing coil and the drive circuit may not be provided for one or a plurality of layers (cylinders). For example, in the case of a three-layer structure as shown in FIG. 6, the demagnetizing coil and the drive circuit may not be provided only for the outer cylinder 11. In this case, the relationship between the outermost cylinder 13 and the inner cylinder 12 is an example of the relationship between the “first cylinder” and the “second cylinder” according to the present invention.

(2-2) Modification 2
In the above embodiment, the elapsed time is measured by the timer 64 and the second drive circuit 5 is activated when the demagnetization time T1 is reached. However, the waveform of the first drive circuit 4 is monitored, and the waveform voltage The second drive circuit 5 may be activated when becomes the minimum value.

(2-3) Modification 3
In the above embodiment, the two drive circuits, the first drive circuit 4 and the second drive circuit 5, are used, but one drive circuit may be used. For example, the control circuit 6 may switch a coil connected to the drive circuit among the first degaussing coil 2 and the second degaussing coil 3 using a switch.

(2-4) Modification 4
The control program 621 executed by the CPU 61 in the above embodiment is a recording readable by a computer device such as a magnetic recording medium such as a magnetic tape or a magnetic disk, an optical recording medium such as an optical disk, a magneto-optical recording medium, or a semiconductor memory. You may provide with the state memorize | stored in the medium. It may also be provided via a network such as the Internet.

DESCRIPTION OF SYMBOLS 1,1A ... Shield part, 11 ... Outer cylinder, 12 ... Inner cylinder, 13 ... Outermost cylinder, 2 ... 1st demagnetizing coil, 3 ... 2nd demagnetizing coil, 4 ... 1st drive circuit, 5 ... 2nd drive circuit , 6 ... control circuit, 61 ... CPU, 62 ... ROM, 621 ... control program, 63 ... RAM, 64 ... timer, 65 ... input unit, 66 ... output unit

Claims (3)

A shield portion having at least a first cylindrical body made of a magnetic material and a second cylindrical body arranged in the hollow of the first cylindrical body and made of a magnetic material;
A first demagnetizing section for demagnetizing the first cylinder;
A second degaussing unit for degaussing said second cylindrical body,
And said second degaussing unit and the first demagnetizing unit at least have a control unit for controlling at least,
The control unit starts demagnetization by the second demagnetization unit after starting demagnetization by the first demagnetization unit . A shield portion having at least a first cylindrical body made of a magnetic material and a second cylindrical body arranged in the hollow of the first cylindrical body and made of a magnetic material; and the first cylindrical body A first demagnetizing unit that demagnetizes, a second demagnetizing unit that demagnetizes the second cylinder, and a control unit that controls at least the first demagnetizing unit and the second demagnetizing unit. In the shield device,
A first step in which the control unit starts demagnetization by the first demagnetizing unit;
The control unit includes at least a second step of starting demagnetization by the second demagnetization unit after the first step. A shield portion having at least a first cylindrical body made of a magnetic material and a second cylindrical body arranged in the hollow of the first cylindrical body and made of a magnetic material; and the first cylindrical body A magnetic shield comprising: a first demagnetizing part that demagnetizes the second demagnetizing part; a second demagnetizing part that demagnetizes the second cylindrical body; and a computer that controls at least the first demagnetizing part and the second demagnetizing part. In the apparatus, the computer
A first step of starting demagnetization by the first demagnetizing unit;
A program for executing at least a second step of starting degaussing by the second degaussing section after the first step.

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