JP3471065B2 - Magnetic shield device for cabtire cable - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention prevents a ferromagnetic material such as a steel frame from being magnetized when a stud bolt is welded to a steel frame in a building or the like by a large current flowing through the cab bolt cable for welding the stud bolt. The present invention relates to a magnetic shield device for a cabtire cable used to do so.

[0002]

2. Description of the Related Art In recent years, equipment installed in office buildings typified by intelligent buildings and precision factories in which clean rooms have been installed are increasingly sensitive to magnetism. For example, CRT for computer
Causes the screen to be distorted or the color to shift due to a DC magnetic field of about 1 G (Gauss). In an unmanned guided vehicle of which traveling is controlled by magnetic information, magnetism of about 1 to 2 G may cause malfunction.

Next, as an example of actual magnetic interference, malfunction of an automatic guided vehicle will be described. This is an unmanned guided vehicle of an optical guidance system installed in a clean room of a precision factory.
It is an abnormal stop at a certain place. This carrier runs along a guide of reflective tape that is continuously pasted on the floor surface, and turns right, left, and stops according to the magnetic address information of the magnet sheet that is pasted on the floor surface at each point. Is controlled. The cause of the malfunction was that the magnetism generated from the floor was mistakenly recognized as the stop information from the magnet sheet.

FIG. 1 is 25 mm from the floor measured by the site.
It is a plane distribution map of magnetism at the height of. The magnetism is distributed irregularly on the floor, but the points above 3G on the line where the magnetic sensor on the transport vehicle passes and the abnormal stop point were the same. In addition to this, a large magnetism was observed on the floor surface, although it did not cause a direct problem outside the traveling line of the carrier.

In general, the following five items can be considered as sources of magnetism existing on the floor of a building. (A) Remanent magnetism of ferromagnetic materials such as steel frames, reinforcing bars, and bolts, which are building structural materials (b) Magnetism generated from power equipment such as power lines (c) Magnetic leakage from substations and machine rooms below ( ) Magnetism generated by permanent magnets accidentally embedded in concrete (e) Magnetism generated by permanent magnets and coils in equipment. Of these, (b) to (e) are clearly limited in the existence of the source. It is a special case that causes permanent magnetism, so in order to deal with this, remove the source or
There is only a way to keep away from the source or to apply a magnetic shield.

However, on a general floor surface, (a)
The remanent magnetism of the ferromagnetic material in
It is thought that countermeasures will become important in the future as a familiar problem that can occur anywhere. This was also the case in the precision factory mentioned earlier. Here, the results of investigation on the problem of residual magnetism of ferromagnetic materials that are easily magnetized, such as iron, cobalt, and nickel, will be given.

FIG. 2 is a cross-sectional layout view of a ferromagnetic material existing inside the floor of the present factory. Remaining of four kinds of materials, steel frame a, rebar b, stud bolt c and high tension bolt d shown in FIG. The possibilities of magnetism are summarized below. In addition,
In the figure, e is a slab and f is a pillar. (A ') The steel frame a has a residual magnetism in the manufacturing plant. (B ') The reinforcing bar b has a residual magnetism due to an electromagnet for handling.

Although magnetized during cutting, its level is small. (C) The stud bolt c is magnetized by a large current during welding. A large current flowing through the cabtire cable during welding magnetizes the surrounding ferromagnetic material. (D ') The high tension bolt d has no problem because it is heat-treated in the final step.

FIG. 3 is a distribution diagram of magnetism on the surface of a ferromagnetic material around a steel beam before concrete placement in an office building of a steel reinforced concrete structure (SRC structure) under construction. Although there are variations in the top of the steel frame, the top of the stud bolt, and the top of the rebar, it can be seen that a large residual magnetism is present. Also, in the figure, the value of the steel frame top end before welding the stud bolt is also shown, but it can be seen that there is a large difference before and after welding.

Table 1 below shows measured values of magnetism generated during stud bolt welding. Current value is 1,700A
Is the peak value during the energization time of 0.6 seconds. from now on,
It can be seen that a large magnetism is generated beside the cabtire cable and that the surrounding ferromagnetic material is magnetized due to the influence. Thus, the problem of residual magnetism of ferromagnetic materials, especially the magnetization of peripheral ferromagnetic materials due to the large current flowing through the cabtire cable when welding stud bolts, is a problem in advanced information-oriented society where a clean magnetic environment is required. This is an important issue to be solved.

[0011]

[Table 1]

If this problem is known in advance and a countermeasure is considered at the time of designing, there is means such as applying a magnetic shield to the floor. The magnetic shield covers the floor with a ferromagnetic material such as permalloy, amorphous, silicon steel plate, pure iron,
It absorbs the invading magnetic field and prevents the invasion of magnetism.
Further, the present inventor has found that as a solution to the above-mentioned problem
In Japanese Patent No. 35948, a magnetic sensor, a degaussing coil, an AC power supply for supplying an alternating current to the coil, and a magnetic detection signal from the floor by the magnetic sensor are input to the unmanned guided vehicle traveling on the floor. We proposed an "automatic degaussing device for the floor surface" equipped with a control device that controls the machine.

[0013]

However, the former method requires a great deal of labor, is costly, and is not necessarily the best solution. The latter method attempts to demagnetize the entire floor surface after the building is completed, but materials with high coercive force such as iron cannot always be completely demagnetized, and some residual magnetism may occur. is there.

In order to completely eliminate the residual magnetism, it is important to take measures to prevent the residual magnetism from remaining in the ferromagnetic material at the time of the manufacturing plant and the construction process, dating from the completion of the building. If measures are taken to deal with the above-mentioned possibility of residual magnetism, steel frame a and rebar b
With regard to the above, it is possible to solve the problem by not using the electromagnet during handling and performing demagnetization work at the factory at the time of shipment. This is a manufacturing issue. On the other hand, welding of the stud bolt c is a problem at the time of construction, and if this problem is solved, the possibility that magnetism will be generated from the floor when the building is completed is greatly reduced.

In consideration of the above, the present inventors have proposed a solution to the problem that the surrounding ferromagnetic material is magnetized by a large current flowing through the cabtire cable during stud bolt welding.
Japanese Patent Application No. Hei 6-31238 "Magnetic Shield Cable Pit" was proposed. This is composed of a plurality of magnetic shield cable units containing cabtire cables for welding stud bolts and joints of the cable units that can rotate at arbitrary angles on a two-dimensional plane. Is composed of a magnetic shield layer made of a ferromagnetic material, a device for fixing a cab bolt cable for welding stud bolts to approximately the center of the magnetic shield layer, and a free caster for moving the cable unit to an arbitrary position. ing.

This is to pass a cabtire cable through a cable pit provided with a magnetic shield to reduce the leakage magnetic field and suppress the magnetization to a ferromagnetic material, and to immediately respond to the movement of the stud bolt welding point. It was made possible. However, since the above-mentioned device is horizontally moved by a universal caster mounted on the bottom of the device, if the deck plate stretched on the floor with the SRC structure has a large unevenness, the caster will be caught and cannot be moved. The problem remains.

In such a situation, it is desired to realize means for solving the problem of magnetization of the ferromagnetic material that accompanies stud bolt welding. The present invention has been proposed in view of such circumstances, and the purpose thereof is to solve the problem that the peripheral ferromagnetic material is magnetized by a large current flowing through the cabtire cable during stud bolt welding, The point is to provide a magnetic shield device for a cabtire cable that can be used even on a deck plate with large irregularities.

[0018]

In order to achieve the above object, a magnetic shield device for a cabtire cable according to the present invention is a non-magnetic, insulative and flexible cab bolt cable for stud bolt welding. Conductive material is spirally wound around a conductive core material, and the currents flowing through the conductive material cancel each other's external magnetic fields, making it possible to suppress the leakage magnetic field as a whole as small as possible. It is characterized by having done.

[0019]

[Operation] The stud bolt is welded to the top of the steel frame in order to integrate the steel frame and concrete.
A plus electrode is provided on the beam steel frame, and a minus electrode is provided between the stud bolt and the base material to generate an arc and weld the bolt. A large DC current flows through the welder of the fixed part that generates the negative electrode, the cabtire cable that connects the gun of the moving part that welds the stud bolt to the predetermined place, and the stud bolt, and its size is 1,500A. ~ 1,60
0 A, energization time is about 1 second. When a DC current flows, a DC magnetic field is generated around the DC current in a concentric circle in the right-hand screw direction with respect to the direction of the current. Assuming that the current is a straight line of infinite length, its magnitude is expressed by H (magnetic field strength) = I / (2 · π · d) I: current (A) d: distance (m). That is, it is proportional to the magnitude of the current and inversely proportional to the distance.

If this is in contact with the ferromagnetic material before it is sufficiently attenuated or if the ferromagnetic material exists in the periphery, the ferromagnetic material is magnetized by magnetic induction, and the residual magnetism remains even if the magnetic field is removed. Become. This is the phenomenon of magnetization of a ferromagnetic material such as a steel frame by the stud bolt welded cabtyre cable targeted by the present invention. The present invention adds a magnetic shield function to the cabtire cable, suppresses the leakage magnetic field to be small, and makes it possible to eliminate the influence of magnetization on the ferromagnetic material.

First, the shape of the cabtire cable will be described as a means for suppressing the leakage magnetic field. As described above, when a DC current flows, a DC magnetic field is generated around the DC current in a right-handed screw direction concentric circle with respect to the direction of the current. When this direct current path is made spiral, a current flows in a direction substantially opposite to the reference point at a point where the current turns 180 ° with respect to an arbitrary point. The magnetic field generated from the electric current on the opposite side acts in a direction to cancel the external magnetic field generated from the reference point, and suppresses the magnetic field leaking to the outside of the spiral as a whole. The effect is higher as the winding pitch and diameter are smaller. To make the current path spiral, the cable may be wound around the core material.

On the other hand, inside the spiral, the directions of the axial magnetic fields from the reference point and the opposite side coincide with each other, and a large magnetic field is generated. This is contained in the inside of the spiral, and there is no problem, but if the core material around which the cable is wound is made of a ferromagnetic material, even the canceling magnetic field is absorbed, and as a result, the external leakage magnetic field is increased. Therefore, the core material needs to be non-magnetic. Further, it is necessary that the material has an insulating property so that electricity is not short-circuited, and has a flexibility capable of being deformed flexibly when the cabtire cable is moved. The cable wound around the core material in a spiral shape is not limited to a cable having an insulating material such as rubber in the outer shell, and may be a conductive material that is a general good conductor of electricity.
However, in this case, a protective layer for maintaining the electrical insulation is required outside the device.

As a result of the above, the magnetic field, which has conventionally been generated concentrically around the current in the right-hand screw direction, is confined in the spiral cable, and the leakage magnetic field to the outside can be suppressed to a small level. Become. However, the residual magnetic field of the ferromagnetic material is 1
When it is assumed that a clean magnetic environment of G or less is suppressed, the above method may not be sufficient. Therefore, as a means for further suppressing the leakage magnetic field, a magnetic shield layer is provided outside the spirally wound cable. Considering that the cabtire cable is freely deformable, a ferromagnetic plate material such as pure iron or permalloy cannot be used as the magnetic shield layer. A thin film material such as an amorphous ribbon, a bulk material such as amorphous flakes and amorphous powder, and a liquid material such as a magnetic fluid are suitable. All of these are materials having a high magnetic permeability, and the thickness is determined according to the required performance.

In order for these materials to fully exhibit the magnetic shield performance, the magnetic saturation phenomenon must be prevented. Magnetic saturation is a phenomenon in which when the magnetic flux density in a material exceeds the saturation magnetic flux density peculiar to the material, magnetism cannot be stored inside and leaks. To prevent this,
There is a method in which the magnetic field strength is reduced by a certain distance from the cable to attenuate the distance, or the thickness is increased. For this reason, the magnetic cable is directly attached to the straight cabtire cable without spirally winding the cable.
It is unrealistic to provide a field layer, and it is a means to be effective only when it is provided on the spiral cable.

[0025]

The present invention will be described below with reference to the illustrated embodiments. FIG. 4 is a front view of a spiral cabtire cable,
A cable 2 is spirally wound around a non-magnetic, insulating and flexible core material 1, for example, neoprene rubber having a circular cross section. As a result, the currents flowing through the cable 2 flow in a spiral shape, and the currents before and after cancel each other's external magnetic fields, so that it is possible to suppress the leakage magnetic field as a whole to be small. Further, a large internal magnetic field is generated in the core material 1 inside the spiral in the axial direction, but there is no problem because it is contained inside the spiral.

FIG. 5 shows a spiral cabtire cable 2
FIG. 6 is a cross-sectional view of a case where the magnetic shield layer 3 is overlaid. A cabtire cable 2 is spirally wound around the core material 1, and an insulating protective layer 4 such as neoprene rubber is provided outside the cabtire cable 2. The protective layer 4 has the meaning of maintaining the electrical insulation between the cables and reducing the leakage magnetic field by distance attenuation to make it close to a parallel magnetic field to enhance the magnetic shield effect. Then, the magnetic shield layer 3 is provided on the outer side thereof. Considering that the cabtire cable 2 can be freely deformed, the magnetic shield layer 3 cannot use a ferromagnetic plate material such as pure iron or permalloy, but a thin film material such as an amorphous ribbon, an amorphous flake, or an amorphous material. A bulk material such as powder and a liquid material such as magnetic fluid are suitable. Both are materials having high magnetic permeability, and the thickness is determined according to the required performance. The outermost shell is provided with an insulating protective layer such as neoprene rubber.

FIG. 6 shows a case where the spiral diameter is 50 mm, the pitch is 50 mm, and five amorphous ribbons each having a thickness of 0.025 mm as a magnetic shield material are laminated in the above embodiment and the current is 1,500 A. The effect of the present invention by the numerical analysis result is shown. The horizontal axis indicates the distance from the outside of the cabtire cable, and the vertical axis indicates the magnetic field strength. It can be seen that, compared with the straight cable, the spiral cable further having the magnetic shield layer has a smaller leakage magnetic field, and the fear of magnetization of the ferromagnetic material is reduced.

[0028]

INDUSTRIAL APPLICABILITY According to the present invention, in a cabtire cable for stud bolt welding, a conductive material is spirally wound around a non-magnetic, insulating, and flexible core material so that the conductive material flows. By applying a magnetic shield to the floor surface by making the currents cancel each other's external magnetic field and eliminating the existence of the generation source itself at the time of construction. As compared with the conventional technique, unnecessary magnetism generated from the floor surface can be efficiently eliminated and cost can be reduced.

Further, since the magnetization itself of the ferromagnetic material is suppressed to be small as compared with the "automatic degaussing device for floor surface" disclosed in the above-mentioned Japanese Patent Laid-Open No. 5-135948, the coercive force such as iron is large and the degaussing is performed. Even with difficult materials, there is no fear that residual magnetism will occur.
Further, in the apparatus of the present invention, the cabtire cable is configured by spirally winding a conductive material on a flexible core material, and a movable caster is not used, so that a deck plate with large irregularities is formed. It can also be used above.

According to the second aspect of the present invention, the magnetic shield effect is further enhanced by providing the flexible magnetic shield layer made of a high magnetic permeability material on the outer shell of the cabtire cable.

[Brief description of drawings]

FIG. 1 is a plane distribution diagram of magnetism at a height of 25 mm from a floor surface measured on site.

FIG. 2 is a cross-sectional view showing an arrangement of ferromagnetic bodies existing inside the floor of a factory.

FIG. 3 is a distribution map of magnetism around a steel beam before concrete placement in a steel reinforced concrete office building under construction.

FIG. 4 is a magnetic sheet of a cabtire cable according to the present invention.
FIG. 3 is a plan view showing an example of a field device.

5 is an enlarged vertical sectional view of FIG.

FIG. 6 is a diagram showing a relationship between magnetic field strength and distance.

[Explanation of symbols] 1 core material 2 cables 3 Magnetic shield layer 4 Insulation protection layer

Front page continuation (58) Fields surveyed (Int.Cl. ⁷ , DB name) B23K 9/32 H05K 9/00

Claims (2)

(57) [Claims] 1. A cabtire cable for welding stud bolts, wherein a conductive material is spirally wound around a non-magnetic, insulating, and flexible core material, and currents flowing through the conductive material are mutually connected. A magnetic shield device for a cabtire cable, which is configured to cancel out the external magnetic field of each other and to suppress the leakage magnetic field as a whole as small as possible. 2. The magnetic shield device for a cabtire cable according to claim 1, wherein a flexible magnetic shield layer made of a high magnetic permeability material is provided on an outer shell of the cabtire cable.