JP6472049B2 - Electronic device storage case - Google Patents

Description

  The present invention relates to a case for storing an electronic device that generates an alternating magnetic field, and relates to an electronic device storage case in which leakage of a magnetic field to the outside is reduced.

  The electronic device storage case needs a power cord for supplying power to the electronic device from the outside, a signal line, and an opening for wiring and piping a cooling pipe or the like when the electronic device is a power device. In addition, a CD / DVD player or the like has an inlet for inserting a media medium. As described above, the electronic device storage case necessarily has an opening, but there is a problem that an alternating magnetic field generated in the electronic device leaks to the outside. In order to solve this problem, Patent Documents 1 to 3 below are known.

  Further, in Patent Documents 1 and 2 below, the electromagnetic shielding effect in the opening is improved by connecting the upper side and the lower side of the opening with a metal body while the medium is stored. Further, in Patent Document 3, a copper wire formed by bending a current that bypasses the opening in a U-shape is bridged to the opening to short-circuit the upper and lower sides of the opening. That is, when a rectangular opening is formed on one metal surface of the metal case, the current induced on the metal surface flows away from the opening, so the current density is the short side of the opening and this The edge region between the edge line of the metal surface parallel to the short side is the highest. For this reason, electromagnetic noise is radiated from a region having a high current density. In order to prevent current from concentrating on the edge region, the upper side and the lower side, which are a pair of long sides of the opening, are connected by a copper wire bent toward the inside of the case.

JP-A-2005-327412 JP-A-5-275877 Japanese Patent No. 4667292

However, in any of the above cases, when the electronic device has a switching element such as a DC-DC converter having a large current and a high-frequency component, suppression of electromagnetic noise to the outside is not sufficient. In particular, if there is an opening in one conductive surface of the conductive case, the magnetic field generated inside the case will be exposed to the outside from the edge of the opening due to the eddy current induced in the conductive surface, and from the opposite edge to the inside. It becomes the flow toward. For this reason, electromagnetic noise is radiated to the outside from the opening. In the conventional example, it has not been effective to reduce electromagnetic noise generated from the opening due to such eddy current.
Accordingly, an object of the present invention is to improve the electromagnetic shielding effect in a state in which wiring and piping are enabled between the inside and outside of the case by further reducing electromagnetic noise radiation in the electronic device storage case. .

The basic configuration of the invention for solving the above problems is a conductive case for housing an electronic device that generates an alternating magnetic field, and an eddy current is induced by the alternating magnetic field, which is a structural surface of the case. In an electronic device storage case having an opening on the current induction surface, a current path width component is formed in the width direction of the flow path of the eddy current induced on the current induction surface at the opening. A strip-shaped conductor plate is provided, and both ends of the conductor plate are pushed out to the inside or outside of the conductive case with respect to the current induction surface, and a predetermined gap is provided with respect to the opening surface of the opening. The electronic device storage case is characterized in that it is bridge-connected to the current induction surface.

  The electronic device housed in the case is arbitrary, but is a device that generates a large eddy current in a conductor constituting the case, such as a device that handles an alternating current and a device that has a high-frequency current component. The shape of the opening is arbitrary. A rectangle, a square, a parallelogram, a diamond, a circle, an ellipse, and the like. The current induction surface is used in the sense of a conductor constituting the case and through which an eddy current flows, and is also a thick concept. The conductor plate is typically a metal plate. In addition, carbon or any other conductive material is optional. The conductor plate may be formed convex toward the inside of the case or convex toward the outside of the case with respect to the opening surface of the opening. The side perpendicular to the width of the conductor plate forms a curved or bent line, and a pair of openings having the line as an outline is formed. Through this opening and the opening on the current induction surface, a power cord, a signal line, a cooling pipe, and the like are wired and piped inside and outside the electronic device storage case.

  In the present invention, the strip-shaped conductor plate having a current path width component in the width direction of the flow path of the eddy current induced on the current induction surface and forming the flow path is the width direction of the conductor plate. It means that the flow width direction of the eddy current is not orthogonal. That is, the most desirable case is when both are parallel. The crossing angle between the two is preferably a range of 0 ° (parallel) to 60 °, a range of 0 ° to 45 °, and a range of 0 ° to 30 ° in order.

In the present invention, the opening has a rectangular shape, and includes a first side having a component in the width direction of the flow path of the eddy current induced on the current induction surface, and a second side parallel to the first side. has, opposite ends edges of the conductor plate is parallel to the first side and a second side, the area adjacent to the first side and a second side on the current-induced surface, have a structure of connecting the two ends of the conductive plates good. This configuration defines the relationship between the eddy current flow path and the sides of the rectangular opening. That is, it means that the flow path width direction of the eddy current is not orthogonal to the first side and the second side. Most preferably, both are parallel. The crossing angle between the two is preferably a range of 0 ° (parallel) to 60 °, a range of 0 ° to 45 °, and a range of 0 ° to 30 ° in order. The relationship between the first side and the second side and the width direction of the conductor plate is parallel. In this case, the sides of the conductor plate are connected to the first side and the second side, or current induction surfaces in the vicinity thereof.

  In the present invention, it is desirable that the first side and the second side of the opening be perpendicular to the flow path of the eddy current. Highest electromagnetic shielding effect.

  In the present invention, it is desirable that both end sides of the conductor plate are longer than the widths of the first side and the second side. The conductor plate is parallel to the current induction surface and faces the opening surface, two side surfaces located on both sides of the bottom surface and intersecting the current induction surface, continuous to each side surface and parallel to the current induction surface. It is desirable to have two connection surfaces connected to the current induction surface. Here, the connection surface means the both end surfaces (surface where the thickness appears) of the conductor plate, or a plane formed by bending from both ends in parallel to the current induction surface. The angle formed by the current induction surface and the side surface of the conductor plate may be 90 °, or may intersect at an angle smaller than 90 °. That is, in the cross-sectional view perpendicular to the width direction of the side surface, a trapezoid whose opening is wider than the bottom surface, or conversely, a trapezoid whose bottom surface is wider than the opening may be used. Further, the side surface may be curved. That is, the conductor plate can have a U shape, a U-shaped groove shape, a trapezoidal groove shape whose upper side is shorter than the bottom side, a trapezoidal groove shape whose upper side is longer than the bottom side, an Ω shape whose bottom surface is flat, and whose side surface is curved. . Furthermore, it is desirable that the both ends be bent in parallel to the current induction surface. Further, the bottom surface means a plane parallel to the current induction surface regardless of whether the conductor plate protrudes toward the inside of the case or protrudes toward the outside.

Further, the conductor plate may be curved in an arc shape and both ends thereof may be bridge-connected to the current induction surface. The arc shape may be a flat side surface and a circular bottom surface, or a flat bottom surface and a circular arc side surface. In these cases, the part connected to the current induction surface on both sides is perpendicular to the current induction surface, and even if only the area hitting the bottom surface is curved in an arc shape, an arc shape including a semicircle over the entire length from both ends It may be curved.

  According to the present invention, an opening formed in a current induction surface that induces eddy current is projected toward the inside or outside of a conductive case with a strip-shaped conductor plate, with a predetermined gap from the opening surface of the opening surface. The conductive plate is arranged so that the width direction of the conductor plate has a component in the width direction of the current path of the eddy current. As a result, a large eddy current can be efficiently bypassed across the opening, and the magnetic field generated by this current prevents the magnetic field generated inside the case from going out of the opening. As a result, electromagnetic noise is prevented from being radiated from the opening.

The block diagram of the electronic device storage case which concerns on one specific Example of this invention, and the conductor board used for it. Explanatory drawing which showed the conditions at the time of calculating | requiring the magnetic field leakage characteristic of an electronic device storage case by simulation. The characteristic view which showed the magnetic field distribution inside and outside an electronic device storage case when the conductor board which concerns on this invention does not exist in an opening part. The characteristic view which shows the result of having calculated | required distribution of the eddy current density of the electric current induction surface of an electronic device storage case by simulation. Explanatory drawing explaining the structure and effect | action of a conductor plate used by a present Example. Explanatory drawing which showed the various structures of the conductor board which concerns on an Example and a comparative example. The characteristic view which calculated | required the magnetic field intensity with respect to x coordinate in the position spaced apart from the electric current induction surface at the time of using the conductor board of various structures by simulation. Explanatory drawing which showed the relationship between the width direction of the electric current path of an eddy current, and the width direction of the connection surface of a conductor board.

Hereinafter, the present invention will be described based on specific examples.
However, the embodiments of the present invention are not limited to the following examples.

  As shown in FIG. 1, the electronic device storage case 1 is a rectangular parallelepiped made of metal, and an opening 20 is formed on one of the six surfaces. The metal surface on which the opening 20 is formed is a current induction surface 10 on which eddy current is induced by an alternating magnetic field generated by an electronic device inside the case. The opening 20 is a square having a side of 50 mm. The shape of the electronic device storage case 1 is arbitrary such as a rectangular parallelepiped, and the dimensions are also arbitrary. The shape and size of the opening 20 are arbitrary.

The eddy current induced on the current induction surface 10 will be described. The distribution of the magnetic field distribution and the current density (dBA / m ² ) of the eddy current in the current induction surface 10 was obtained by simulation by electromagnetic field analysis. As shown in FIG. 2A, the electronic device storage case 1 was a cube made of an aluminum plate having a thickness of 0.5 mm and having a side of 300 mm. With the center of the cube as the origin, an o-xyz coordinate system is taken as shown. As shown in FIG. 1, the opening 20 is a square having a side of 50 mm, and each side is parallel to each ridge line of the square current induction surface 10, that is, parallel to the x-axis and the y-axis. As shown in FIG. 2, the center position of the opening 20 is the center (y = 0) in the y-axis direction and 75 mm from the center in the x-axis direction. A coil having a winding number of 10 and a diameter of 100 mm was placed at the center of the cube, and an alternating current with a frequency of 100 kHz and a current of 400 mA was applied. The distribution of the internal space and the external magnetic field (dBA / m) of the electronic device storage case 1 at this time was obtained. The magnetic field distribution on the xz plane passing through the center of the case 1 and the center of the opening 20 is shown in FIG. Obviously, it is understood that the magnetic field leaks to the front region (+ z-axis direction) centering on the opening 20.

Further, the distribution of eddy current density (dBA / m ² ) on the inner surface of the current induction surface 10 was obtained. FIG. 4A shows an eddy current density distribution when the opening 20 is not present, and FIG. 4C shows an eddy current density distribution when the opening 20 is present. The eddy current density is rotationally symmetric with respect to the center of the current induction surface 10 and has a distribution in which x, which is the center of one half of a square, is maximum at a position of 75 mm when viewed in the x-axis direction. Yes. Further, it can be seen that the eddy current flows perpendicular to the x-axis projected on the current induction surface 10 (hereinafter referred to as “projected x-axis”) in the region where the x coordinate is centered at 75 mm and the width is 50 mm. That is, the flow path width direction of the eddy current is the projected x-axis direction.

  Eddy currents induced in the current induction surface 10 generate a magnetic field. This induced magnetic field is generated in a direction to demagnetize the magnetic field generated by the coil, the direction of the eddy current in the cross section (xz plane) of the current induction plane 10, and the magnetic field distribution on the xz plane in the vicinity of the back surface of the current induction plane 10. Is as shown in FIGS. 4B and 4D. When the opening 20 is not present, each eddy current generates a magnetic field in the counterclockwise rotation direction on the xz plane in the projected x-axis positive region, and each eddy current is clocked on the xz plane in the negative region of the projected x-axis. A rotating magnetic field is generated. As a result, the magnetic field flows along the back surface of the current induction surface 10 in the positive and negative directions of the projected x axis. When the opening 20 exists, the edge portion on the negative side of the projection x-axis of the opening 20 has no eddy current at a position adjacent to the projection x-axis in the positive direction, and the projection x-axis In the edge part on the positive side, there is no eddy current at a position adjacent to the negative direction of the projected x-axis. Therefore, the magnetic field going outward from the negative edge portion of the projected x-axis of the opening 20 cannot be canceled, and the magnetic field going from the outside to the inside is generated at the positive edge portion of the projected x-axis. Let As a result, the magnetic field leaks from the opening 20 to the outside.

  A configuration in which leakage of a magnetic field to the front of the opening 20 shown in FIG. 3 is reduced while realizing the spatial communication between the inside and the outside of the electronic device storage case 1 is the present invention. As shown in FIG. 1, a conductor plate 30 that is bent and formed in a U-shape protruding toward the inside of the electronic device storage case 1 is provided in the opening 20 so as to cover the opening surface 21. . The conductor plate 30 is a metal plate made of strip-shaped aluminum having a thickness of 0.5 mm, a width of 50 mm, and a length of 100 mm. The conductor plate 30 includes a bottom surface 31 parallel to the opening surface 21 of the opening 20 and the current induction surface 10, side surfaces 32a and 32b continuous to the bottom surface 31 and orthogonal to the bottom surface 31 and the current induction surface 10, and side surfaces 32a thereof. , 32b have connection surfaces 33a and 33b which are surfaces connected to the back surface of the current induction surface 10 at both end surfaces (surfaces where the thickness appears).

  As shown in FIG. 1, the opening 20 has a first side 22 a and a second side 22 b that are parallel to the width direction of the eddy current flow path (projection x-axis direction). The connection surfaces 33a and 33b are the back surfaces of the current induction surface 10 so that the width direction of the connection surface 33a of the conductor plate 30 is parallel to the first side 22a and the width direction of the connection surface 33b is parallel to the second side 22b. It is connected to the. As a result, as shown in FIG. 5, eddy currents flowing through the current induction surface 10 are connected from the current induction surface 10 on the first side 22a of the opening 20 to the connection surface 33a, the side surface 32a, the bottom surface 31, and the side surface 32b of the conductor plate 30. The current flows to the current induction surface 10 of the connection surface 33b and the second side 22b. As shown in FIG. 5, the magnetic field generated by the eddy current flowing through the conductor plate 30 cancels the magnetic field generated in the positive direction of the projected x-axis of the magnetic field generated in FIG. 4D. As a result, the magnetic field is prevented from leaking outside from the opening 20.

  Next, as shown in FIG. 6, the shape of the conductor plate 30 and the arrangement relationship with respect to the opening 20 were variously changed. As shown in FIG. 2B, the distribution in the x-axis direction of the magnetic field strength at a position 50 mm (z coordinate 200 mm) above the current induction surface 10 where the opening 20 was formed was obtained. The result is shown in FIG. In the structure of FIG. 6A, the side surface of the conductor plate is provided parallel to the width direction of the eddy current flow path, that is, parallel to the x-axis. In the structure of FIG. 6B, the side surface of the conductor plate is provided perpendicular to the width direction of the eddy current flow path, that is, parallel to the y-axis, and the conductor plate having the structure of FIG. It is the structure made to do. The structure of FIG. 6C is a structure in which the conductor plate is formed of four rods in place of the bottom surface and the side surface. The structure shown in FIG. 6D is a structure in which a plurality of band-shaped bent conductor plates shown in FIG. 6A are formed into U-shaped rods arranged in the x-axis direction. The structure of FIG. 6E is a structure in which the strip-shaped conductor plate of FIG. 6A is curved in an arc shape. The width direction of the strip-shaped conductor plate curved in the arc shape is parallel to the flow width direction of the eddy current, that is, the x-axis direction. The structure of FIG. 6F is a structure in which a conductor plate bent into a U-shape in FIG. 6A is protruded toward the outside of the electronic device storage case 1. The width direction of the conductor plate is parallel to the eddy current channel width direction, that is, the x-axis direction.

  Symbols (a) to (f) for distinguishing the characteristics of the magnetic field strength with respect to the x coordinate shown in FIG. 7 correspond to the symbols (a) to (f) in FIG. 6 showing the structure of the conductor plate. The characteristic (g) of FIG. 7 shows the characteristic in the case where the conductor plate is not present and the opening is present. As understood from the characteristics of FIG. 7, the magnetic field above the center point of the opening (x coordinate 75 mm, z coordinate 200 mm) is −32 dBA / m when the conductor plate is not present (g). On the other hand, when the conductor plate is strip-shaped and the flow width direction of the eddy current is the width direction of the conductor plate, (a), (e), and (f) show −50 dBA / m and −52 dBA, respectively. / M, -49 dBA / m. On the other hand, in the case (d) in which the conductor plate is not a strip but is a rod arranged in a plurality in the eddy current flow path width direction, the leakage of the magnetic field is -43 dBA / m. Even if the conductor plate is formed in a strip shape, the width direction is perpendicular to the flow width direction of the eddy current (b), or the conductor plate is four rods that support the bottom and four corners (c). In both cases, the leakage of the magnetic field is -38 dBA / m. In addition, except for the case where the conductor plate is provided so as to protrude above the opening (outside of the case) (f), the magnetic field is greatest at the position above the center of the opening, and as the distance from the center increases. It can be seen that the magnetic field is attenuated.

  From the above examination, it is found that the effect of shielding the magnetic field on the opening 20 is high when the conductor plate 30 is formed in a strip shape and the width direction thereof is parallel to the flow width direction of the eddy current induced on the current induction surface 10. It was. In these cases (a), (e), and (f), the shielding effect is improved by 17 to 20 dBA / m at a position above the center of the opening 20 as compared with the case where no conductor plate is provided. Other than the upper portion of the opening, there is a further effect. When the conductor plate is provided outside (upper side) of the opening (f), the shielding effect is lower than when the conductor plate is provided inside (lower side) (a). This is probably because the magnetic field generated by is generated outside the opening (outside the case), so that the effect of canceling the magnetic field flowing along the inner surface of the current induction surface is low. Also, when the conductor plate is curved in an arc shape (e), the highest shielding effect is that the area of the opening side surface perpendicular to the x-axis of the conductor plate formed by bending or bending is U-shaped. This is probably because it is smaller than the case (a). The power line, the signal line, or the cooling pipe is drawn into the electronic device storage case 1 through the opening side surface (corresponding to 35 and 36 in FIG. 1) and the opening 20.

  Next, the relationship between the width direction of the strip-shaped conductor plate and the direction of the eddy current flow path width will be described. FIG. 8 corresponds to the eddy current distribution on the current induction surface of FIG. It is assumed that the eddy current A flows parallel to the y axis. The flow width direction of the eddy current is parallel to the x axis. The angle formed by the width direction of the connection surface 33a of the conductor plate 30 and the eddy current width direction (x axis) is defined as θ. The eddy current flowing from the connection surface 33a into the conductor plate 30 is the largest when θ = 0 ° and takes the maximum value M, and theoretically becomes 0 when θ = 90 °. Therefore, when the width direction of the conductor plate and the width direction of the eddy current intersect at θ, the eddy current flowing into the conductor plate is Mcos (θ). Therefore, when θ = 60 °, the eddy current flowing into the conductor plate is ½ of the maximum value M. Therefore, the angle θ formed between the width direction of the conductor plate and the eddy current width direction is 0 ° or more and 60 ° or less. desirable. When θ = 30 °, the eddy current flowing into the conductor plate is 0.87 M, which is almost the same as when the width direction of the conductor plate is parallel to the eddy current width direction. Therefore, the angle formed between the width direction of the conductor plate and the eddy current width direction is more preferably 0 ° or more and 30 ° or less.

  The present invention can be used in a case that houses an electronic device that generates an alternating magnetic field. In particular, the present invention can be used for a case that houses a power control device having a DC-DC converter that carries a high-frequency high-current that is mounted on a hybrid vehicle.

DESCRIPTION OF SYMBOLS 1 ... Electronic device storage case 10 ... Current induction surface 20 ... Opening part 30 ... Conductor plate 31 ... Bottom surface 32a, b ... Side surface 33a, b ... Connection surface

Claims (5)

An electrically conductive case for housing an electronic device that generates an alternating magnetic field, the electronic device housing having an opening in a current induction surface that induces eddy current by the alternating magnetic field, which is a constituent surface of the case In case
In the opening, a band-shaped conductor plate is provided for forming the flow path having a current path width component in the width direction of the flow path of the eddy current induced on the current induction surface;
Both ends of the conductor plate are pushed out to the inside or outside of the conductive case with respect to the current induction surface, and a predetermined gap is provided with respect to the opening surface of the opening to cover the opening, Bridged to the current induction surface ,
The conductor plate is parallel to the current induction surface and is opposed to the opening surface, two side surfaces located on both sides of the bottom surface and intersecting the current induction surface, and continuous to the side surfaces, the current induction surface. And an electronic device storage case having two connection surfaces connected to the current induction surface. An electrically conductive case for housing an electronic device that generates an alternating magnetic field, the electronic device housing having an opening in a current induction surface that induces eddy current by the alternating magnetic field, which is a constituent surface of the case In case
In the opening, a band-shaped conductor plate is provided for forming the flow path having a current path width component in the width direction of the flow path of the eddy current induced on the current induction surface;
Both ends of the conductor plate are pushed out to the inside or outside of the conductive case with respect to the current induction surface, and a predetermined gap is provided with respect to the opening surface of the opening to cover the opening, Bridged to the current induction surface,
The electronic device storage case, wherein the conductor plate is curved in an arc shape and both ends thereof are bridge-connected to the current induction surface. The opening has a rectangular shape, and has a first side having a component in the width direction of the flow path of the eddy current induced on the current induction surface, and a second side parallel to the first side. And
Opposite ends sides of the conductor plate is parallel to the first side and the second side, the area adjacent to the first side and the second side on the current-induced surface, connecting both ends of the conductor plate The electronic device storage case according to claim 1 , wherein the electronic device storage case is provided. The electronic device storage case according to claim 3 , wherein the first side and the second side are perpendicular to the flow path of the eddy current. 5. The electronic device storage case according to claim 3 , wherein the both end sides of the conductor plate are longer than widths of the first side and the second side.