JPS609578B2 - Spring for magnetic shield - Google Patents

Description

[Detailed Description of the Invention] A shield room that shields noise from various high-frequency electrical devices and trains, geomagnetism, external interference radio waves, etc. is used for various experiments.

Even if the floor, walls, ceiling, etc. of such a shield room are completely magnetically shielded, magnetic intrusion or leakage occurs through the gap between the door and the frame for the entrance and exit of the person being measured. For this reason,
Conventionally, springs have been provided to fill the gap between the door and the frame. When the door is closed, this spring comes into close contact with the door and frame to prevent the passage of magnetism. The present invention relates to such a magnetic shielding spring, and particularly to its material.

Conventional magnetic shielding springs of this type use materials with good electrical conductivity and high elasticity, such as phosphorescent steel or beryllium alloy. And the structure is the first
Referring to the figure, there is shown a long band-shaped plate part 10.2 in which screw holes 101 are formed at intervals for attaching the spring 10 to a door or frame, and an elongated band-shaped plate part 10.2 integrally extending along one side of the plate part 10.2. It consists of a semi-cylindrical part 103 which is bent into a semi-circular shape in a direction perpendicular to its extending direction. A plurality of notches 104 are formed in this semi-cylindrical portion 103 at intervals in the length direction, extending from the side green toward the band-shaped plate portion 102 . By the way, the above-mentioned conventional magnetic shielding spring has a sufficient effect on shielding high frequency magnetic fields, but ``It can be said that it has no effect on DC magnetic fields at all.
It had no shielding ability.

As a result of experiments on various materials, the inventors found that Fe
, Co, Ni, Si and B are suitable as materials for this type of spring. That is, the present invention provides a magnetically shielded chamber spring that fills the gap between the door and frame of a magnetically shielded chamber such as a magnetically shielded case or a magnetically shielded room, using Fe, Co
, Nj, Si, and B as main components, and is characterized by being made of an amorphous metal that has high magnetic permeability and conductivity, is rich in elasticity and corrosion resistance, and is resistant to bending and mechanical distortion.

As the amorphous metal mentioned above, Samurai Sho 51-11
The amorphous alloy disclosed in No. 657 (Japanese Unexamined Patent Publication No. 53-43028) is most suitable.

That is, the atomic ratio is 3 to 12% Fe, 50% or less Ni,
Si20% or less, B5 to 25%, (However, Si + B20
~35%) with the remainder being Co. Although it was disclosed in the above application that this material has high magnetic permeability and low coercive force, the present inventors believe that this material has high electrical conductivity, high elasticity and corrosion resistance, and has high magnetic permeability and low coercive force. It was confirmed that the material is resistant to mechanical distortion and is suitable as a material for the above-mentioned magnetic shielding spring. An example is shown in Table 1. Table 1: This material has a saturation magnetic flux density (mother) of 710 eauss, a coercive force of 4 m○e, a magnetostriction (input s) of 0.2 x 10-6 or less, and a magnetic permeability (Akihi 2). Since O=30,000 is extremely large, it is possible to effectively magnetically shield external DC magnetism and high frequency magnetism.

In addition, this amorphous metal B has a Vickers hardness (Hv) of 90
0, it is hard, highly elastic, and has a strong trajectory, so it is hard to get scratched, and since the magnetostriction is close to zero, it is less susceptible to deterioration of the magnetic Simard effect due to bending and mechanical strain.
Furthermore, since the electrical resistance (p) is as small as 134 (circle/skin), it is suitable as a high-frequency magnetic shielding material. FIG. 2 shows a magnetic shielding spring made using the above-mentioned amorphous metal, and since the structure itself is the same as the conventional example shown in FIG. 104
They are shown as 20, 201 to 204, respectively, and detailed explanation will be omitted.

However, here, the difference is that the notch 104 in the conventional example shown in FIG. 1 is not a notch, but an elongated hole 204, but, of course, the notch may be used as in the conventional example. However, the advantage of using a slotted hole is that the tip of the spring does not break when the door is opened and closed, which eliminates the problem of the spring getting caught on an external object and breaking. FIG. 3 is a sectional view showing a state in which the magnetic shielding spring 20 of FIG. 2 is used for a door of a magnetically shielded room.

Referring to the figure, the door 31 is surrounded by a magnetic shielding frame 3.
11, and the frame pillar 32 to which the door is attached;
33 also has a magnetic shielding material 3 whose surface is continuous with the wall surface.
Covered with 4. 35 is a hinge that supports the door 31.

Magnetic shielding springs are attached to both end faces of the door to fill the gap between the door and the frame. This attachment is accomplished by threading a screw through the screw hole 201 and into the door. A magnetically shielded room that uses the magnetic shielding spring of the present invention in the door frame has a higher
It was confirmed that the material had a high magnetic shielding effect without degrading the high frequency magnetic shielding effect (Table 2). Also, no damage to the magnetic shielding spring was observed when the door was operated (Table 3). The present invention has been described above, and according to the present invention, an amorphous metal material with high magnetic permeability and extremely low electrical resistance, rich in elasticity and corrosion resistance, and resistant to bending and mechanical distortion is used. Thus, a magnetic shielding spring can be obtained which has not only high-frequency magnetic shielding as in the prior art, but also DC magnetic shielding, and can completely prevent mechanical failures such as breakage of parts.

Table 2 Magnetic shielding degree Shielding degree = Ho/day i Ho: External magnetic field Day i: Internal magnetic field Table-3 Defective state of shielding sprink

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a conventional high-frequency magnetic shielding spring, FIG. 2 is a perspective view of a magnetic shielding spring as an embodiment of the present invention, and FIG. 3 is a magnetic shielding spring. FIG. 3 is a cross-sectional view of the door of the shield room. 10, 20...Magnetic shielding spring, 1
01,201...Screw hole, 102,202...Band-shaped plate part, 103,203...Semi-cylindrical part, 104...
...Notch, 204...Elongated hole. Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] 1 In the magnetic shielding spring that fills the gap between the door and frame of the magnetic shielding room, the atomic ratio is Fe3-12.
%, Ni 50% or less, Si 20% or less, B5-25% (
However, for shielding, it is made of an amorphous metal that consists of Si + B (20 to 35%) and residual Co, has high magnetic permeability and conductivity, is rich in elasticity and corrosion resistance, and is resistant to bending and mechanical distortion. spring.