JP7141996B2 - Magnetic field shielding structure for railway vehicles - Google Patents

Description

The present invention relates to a magnetic field shielding structure for railway vehicles, and provides a structure capable of reducing the weight and effectively shielding the magnetic field.

Railway vehicles are required to have a certain level of safety in terms of various items such as fire resistance and impact resistance. Since railway vehicles use a large electric current to run in the first place, the safety of electromagnetic waves caused by the electric current is also required. However, there are many unclear points about the effects of magnetic lines of force on the human body, and the level of serious effects on human life, like radiation, has not been clarified.

As one guideline, there is a concept that the limit value of exposure guideline for the general public set by the International Commission on Non-Ionizing Radiation Protection (ICNIRP) in 1998 is used as the reference value. A specific numerical value is 200 μT (microtesla) at a commercial frequency (50 Hz or 60 Hz). This value is about 0.5 mT when converted to a static magnetic field. In this industry, the static magnetic field is often expressed as magnetic flux density, so in this specification as well, the term "magnetic field" may be expressed in units of "magnetic flux density".

On the other hand, there is a pacemaker as a typical device to be implanted in the body. The instrument operates at a fixed rate for testing when an external static magnetic field of 2 mT or greater is applied. Therefore, in a railway vehicle, a static magnetic field of 1 mT or less is required.

In a railroad vehicle, a current of about 1000 A is supplied from an overhead wire to an inverter that drives a motor through a power line arranged under the floor of the railroad vehicle via a pantograph. A current of 1000 A is strong enough to generate a magnetic field of about 200 μT at a distance of 1 m. A power line through which such a current flows is arranged at a point about 10 cm below the floor of the vehicle. Therefore, the target value of the industry is to set the leakage magnetic field (in terms of magnetic flux density) to 1 mT or less at a point (floor surface of a railway vehicle) 10 cm away from the power line.

Patent Document 1 is cited as a technique for shielding leakage magnetic fields on the floor surface of a railway vehicle. Referring to FIG. 8, in Patent Document 1, in a floor structure 110, a power line 120 extending in a rail direction is arranged at a center portion in a direction of a sleeper below a floor surface 107a of a passenger room, and a floor plate 102 and a floor surface 107a of the passenger room are arranged. A shield plate 130 for suppressing the magnetic field generated on the passenger compartment floor 107a is arranged between them. The shield plate 130 has a first shield plate 131, a second shield plate 132, and a third shield plate 133, which are formed in a thin plate shape. The first shield plate 131 covers the upper surface 102 a of the floor plate 102 above the power line 120 .

The second shield plate 132 covers the upper and end surfaces of the first shield plate 131 on one side in the sleeper direction and the upper surface 102a of the floor plate 102 on one side in the sleeper direction. A structure is disclosed in which the third shield plate 133 covers the upper surface and end surface of the first shield plate 131 on the other side in the sleeper direction and the upper surface 102a of the floor plate 102 on the other side in the sleeper direction.

With this structure, it is possible to provide a railway vehicle floor structure capable of suppressing an increase in weight and making it difficult for a locally strong magnetic field to occur on the passenger compartment floor surface.

JP 2015-150969 A

Specifically, Patent Literature 1 describes laying a plate of hot-rolled steel (SPHC) with a thickness of 6 mm under the floor. It is true that the leakage magnetic field on the floor surface can be reduced, but the weight is not reduced.

The present invention has been conceived in view of the above problems, and provides a magnetic field shielding structure that reduces the leakage magnetic field on the floor surface by providing the magnetic field shielding structure in the vicinity of the power line through which a large current flows.

More specifically, the magnetic shielding structure according to the present invention includes:
A magnetic field shielding structure for shielding a magnetic field from a power line arranged under the floor of a railway vehicle,
a power line duct that covers the power line without gaps ;
a magnetic field shielding plate in contact with the power line duct and disposed between the floor and the power line;
Both ends of the magnetic field shielding plate are inclined in a direction opposite to the floor when viewed in cross section in a direction perpendicular to the longitudinal direction of the power line, and the inclination is from 30 degrees to 60 degrees .

The magnetic field shielding structure according to the present invention biases the distribution of the magnetic field generated by the current flowing through the power line by tilting both ends of the power line duct when viewed cross-sectionally covering the power line, thereby reducing the leakage magnetic field on the floor surface. can be made Moreover, such a structure is effective even if the thickness of the magnetic field shielding plate is 2.3 mm, and can produce a very large light weight effect.

It is a figure which shows the structure of a magnetic field shielding structure. FIG. 10 is a diagram showing the structure of the magnetic shielding structure when the angle θ formed by the shielding plate main body and the vertical wall is changed from 0° to 90°; FIG. 4 is a diagram showing magnetic properties of a magnetic material portion; It is a figure which shows the simulation result when the thickness of a magnetic material part is 2.3 mm. It is a figure which shows the simulation result when the thickness of a magnetic material part is 3.2 mm. It is a figure which shows the simulation result when the thickness of a magnetic material part is 4.5 mm. It is a figure which shows the simulation result when thickness of a magnetic material part is 9.0 mm. 1 is a diagram illustrating a conventional magnetic shielding structure; FIG.

A magnetic shielding structure according to the present invention will be described below with reference to the drawings. In addition, the following description illustrates one embodiment of the present invention, and the present invention is not limited to the following description. The following description can be modified without departing from the spirit of the invention.

FIG. 1(a) shows the overall configuration of the simulation performed for the present invention. FIG. 1(a) shows a part of the underfloor portion in a cross section taken perpendicularly to the longitudinal direction of the railway vehicle. Here, the longitudinal direction is the traveling direction of the railway vehicle. x is the sleeper direction. The current from the pantograph passes from the roof of the railroad car through the end, through the power line 9 arranged under the floor surface 20 of the railroad car, and flows to the main circuit power supply VVVF inverter, where it is converted into a pseudo three-phase alternating current. The converted current flows to the truck motor. In the following description, the floor surface 20 refers to the floor surface in contact with passengers in the railway vehicle.

FIG. 1(a) can be said to be a cross section of the power line 9 cut in a direction perpendicular to the longitudinal direction. The assumed magnetic field shielding structure 1 has a power line 9 arranged under the floor 20 of a railway vehicle, covered with a power line duct 12 , and a magnetic field shielding plate 10 arranged between the floor 20 and the power line duct 12 .

FIG. 1(b) shows an enlarged view of the power line 9 portion. The power line 9 has an outer diameter of 23.6 mm. The current flows evenly through this cross section. The power line 9 is covered with a power line duct 12 . It is assumed that the power line duct 12 has a substantially rounded rectangular cross section with a width of 110 mm and a height of 50 mm. A magnetic field shielding plate 10 is arranged between the power line duct 12 and the floor 20 surface. The magnetic field shielding plate 10 has a width of 130 mm when viewed in a cross section perpendicular to the longitudinal direction, and has vertical walls 10b of 50 mm in length at both ends.

A horizontal portion (flat plate portion) of the magnetic field shielding plate 10 is called a shielding plate main body 10a. The shielding plate main body 10a and the vertical wall 10b are collectively called a magnetic body portion, and the angle formed by them is θ. Also, the magnetic field shielding plate 10 is assumed to have the same thickness ts between the shielding plate main body 10a and the vertical wall 10b. The thickness td of the power line duct 12 is constant at 2.3 mm. Also, the tip of the vertical wall 10b is referred to as a tip 10p. The vertical walls 10 correspond to both ends of the magnetic shielding plate 10 .

In the simulation, the angle θ between the thickness ts of the magnetic shielding plate 10 and the vertical wall 10b was varied. FIG. 2 shows cross sections of the magnetic shielding structure 1 when the angle .theta. with respect to the vertical wall 10b is changed. From FIG. 2(a) to FIG. 2(e), the cases of θ=90°, 60°, 45°, 30° and 0° are shown. θ=0° is the case where the magnetic shielding plate 10 is parallel to the floor surface 20 . As the angle θ increases, the vertical wall 10 inclines in the direction opposite to the floor surface 20 (track side).

Referring again to FIG. 1(a), the total number of meshes was 31880, and the number of meshes was increased in the magnetic portion (magnetic field shielding plate 10 and power line duct 12) and its surroundings. The simulator used was "Finite Element Method Magnetics". A coordinate origin 25 is a point 10 cm above the center of the power line 9 . This point is assumed to be the floor surface 20 . The arrow in FIG. 1(a) is the x direction. The results that follow display the magnetic flux density at points from the origin 25 in the x-direction. Hot-rolled steel was used for the magnetic material portion, and the magnetostatic properties were as shown in FIG.

Referring to FIG. 3, the horizontal axis is the externally applied magnetic field (A/m), and the vertical axis is the magnetic flux density (corresponding to "magnetization" in this case) (T). It has a magnetic flux density of about 1.7 T (17 kGauss) when an externally applied magnetic field of 5000 A/m (62.7 Oe) is applied. The rise from the demagnetized state to 1 T (10 kGauss) is 500 (A/m) (6.27 Oe), which is almost straight.

For convenience of calculation, the magnetomotive current was set to 1/5 of 1000A. Therefore, the calculated 0.2mT is the 1mT line for a real current of 1000A.

FIG. 4 shows simulation results. The horizontal axis is the horizontal position (mm), and the vertical axis is the magnetic flux density (mT). This magnetic flux density represents the leakage magnetic field at the floor surface 20 . The horizontal axis is the x direction in FIG. 1(a). The zero point on the horizontal axis in FIG. 4 corresponds to the origin 25 in FIG. 1(a). FIG. 4 shows the results when the thickness ts of the magnetic portion is set to 2.3 mm. In addition, five types of results with θ of 0°, 30°, 45°, 60°, and 90° are displayed in an overlapping manner.

Up to a horizontal distance of about 100 mm, the magnetic flux density was lowest when θ was 0°, but the magnetic flux density increased outside of that. On the other hand, when θ was 90°, the magnetic flux density was the highest in the range of 100 mm in the horizontal direction. Furthermore, the maximum value when θ was 90° exceeded 0.2 mT (equivalent to 1 mT at a magnetomotive force of 1000 A). When θ was 30° to 60°, θ was lower than 0° and 90° even outside 125 mm in the horizontal direction.

FIG. 5 shows the results when the thickness of the magnetic material portion is 3.2 mm. As the thickness increased, the overall magnetic flux density decreased in the range from the origin 25 to 75 mm. That is, it can be said that the magnetic field shielding ability is improved. The magnetic flux density distribution with respect to both end angles (θ) of the magnetic shielding plate 10 had the same tendency as in FIG.

FIG. 6 shows the results when the thickness of the magnetic material portion is 4.5 mm. Although the magnetic flux density is slightly decreased in the section up to 75 mm, the magnetic flux density is rather increased after 100 mm when θ is 90°.

FIG. 7 shows the results when the thickness of the magnetic material portion is 9.0 mm. The trend was the same. When θ was 90°, the magnetic flux density hardly decreased even at 75 mm or less, and the magnetic flux density at the point of 100 mm became clearly high. Also, in the case of 0°, although the magnetic field shielding ability was high in the region of 75 mm or less, the magnetic flux density became larger than that of other angles after exceeding 100 mm.

The reason why the magnetic flux density at the 100 mm portion is large even though the thickness ts of the magnetic portion is large is that, in the case of the vertical wall 10b, which rises at an angle of 90° to the shield plate main body 10a, the magnetic field is generated by the magnetomotive force. It is believed that the shielding plate 10 itself was magnetized and a large magnetic pole was generated at the tip 10p of the vertical wall 10b, thereby creating a large leakage magnetic field in the direction of the floor surface 20 as well.

Moreover, as the thickness of the magnetic field shielding plate 10 increases, the cross-sectional area of the magnetic portion increases, so the total amount of magnetic flux increases, and it is considered that a large magnetic flux density is generated near 100 mm. In the vertical wall 10b when θ is 90°, the tips 10p are close to each other, so the demagnetizing field between the magnetic poles is small, and the magnetic flux density is further increased.

On the other hand, if the thickness of the magnetic shielding plate 10 is reduced to 2.3 mm, the magnetic shielding ability is lowered, but a large magnetic pole is not generated at the tip 10p of the vertical wall 10b. It becomes smaller than when it is thick (for example, 9 mm: FIG. 6).

When the angle of the vertical wall 10b is tilted from 30° to 60°, the leakage magnetic field on the floor surface 20 does not change greatly depending on the location, and is 0.15mT to 0.2mT (0.75mT to 1mT in terms of 1000A). ) is well within the range of

By slanting the vertical wall 10b, the magnetic poles generated at the tips 10p of the vertical walls 10b are separated from the floor surface 20, and the magnetic poles are also separated from each other. Therefore, it is considered that substantially the same magnetic flux density is generated at any position in the horizontal direction.

In this way, the vertical walls 10b at both ends of the magnetic shielding plate 10 when viewed in cross section are inclined in the direction away from the floor surface 20, so that the magnetic poles formed at the tips 10p of the vertical walls 10b can also be seen from the floor surface 20. The magnetic poles can also be kept away from each other, and the leakage magnetic field of the floor surface 20 can be suppressed.

In the conventional magnetic field shielding structure 1 having such a configuration, the thickness ts of the magnetic shielding plate 10 was 9 mm, and the angle θ with respect to the vertical wall 10b was 90°. However, by inclining the vertical wall 10b in the direction away from the floor surface 20 to an angle smaller than 90°, the leakage magnetic field on the floor surface 20 can be suppressed.

In addition, by adopting such a configuration, even if the thickness ts of the magnetic field shielding plate 10 is thinner than 9 mm, which has been conventionally adopted, the leakage magnetic field on the floor surface 20 can be reduced to the specified value or less, and the magnetic field shielding structure 1 can be made lighter.

Further, although no simulation was performed, the above results show that the ends 10p of the vertical walls 10b move away from each other as the length of the shielding plate main body 10a increases, resulting in a higher magnetic field shielding capability. Also, the longer the vertical wall 10b, the higher the magnetic field shielding ability. Furthermore, if the thickness of the power line duct 12 is 2.3 mm or more, it goes without saying that the magnetic field shielding ability is further improved.

Therefore, the thickness of the power line duct 12 should be 2.3 mm or more, the length of the shield plate main body 10a should be 130 mm or more, and the length of the vertical wall 10b should be 50 mm or more.

INDUSTRIAL APPLICABILITY The magnetic field shielding structure according to the present invention can be suitably used to shield a magnetic field from a large-current power line arranged under the floor of a railway vehicle.

1 Magnetic field shielding structure 9 Power line 10 Magnetic field shielding plate 10a Shielding plate body 10b Vertical wall 10p Tip 12 Power line duct 20 Floor surface 25 Origin td Thickness θ of power line duct 12 Angle ts between shielding plate body 10a and vertical wall 10b Magnetic field shielding plate 10 the thickness of

Claims (3)

A magnetic field shielding structure for shielding a magnetic field from a power line arranged under the floor of a railway vehicle,
a power line duct that covers the power line without gaps ;
a magnetic field shielding plate in contact with the power line duct and disposed between the floor and the power line;
A magnetic field of a railway vehicle, wherein both ends of the magnetic field shielding plate are inclined in a direction opposite to the floor when viewed in cross section in a direction perpendicular to the longitudinal direction of the power line, and the inclination is from 30 degrees to 60 degrees. Shielding structure. 2. A magnetic field shielding structure for a railway vehicle according to claim 1, wherein said magnetic field shielding plate is made of hot rolled steel and has a thickness of 2 to 6 mm. The power line duct is a hot-rolled steel material having a thickness of 2.3 mm or more,
a shielding plate main body in which the magnetic field shielding plate is a flat plate portion having a length of 130 mm or more in a cross-sectional view in a plane perpendicular to the length direction;
3. The magnetic field shielding structure for a railway vehicle according to claim 1 or 2 , characterized in that the magnetic field shielding structure for a railway vehicle is composed of inclined vertical walls having a length of 50 mm or more provided on both sides of the shielding plate main body. .

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