MAGNETIC CORE

A magnetic core that includes split magnetic cores provided with a plurality of gaps therebetween. The magnetic core is capable of suppressing the influence of a position shift of the split magnetic cores on magnetic characteristics. A first end face of a first split magnetic core faces a third end face of a second split magnetic core, with a first gap provided therebetween in a left-right direction. Further, a second end face of the first split magnetic core faces a fourth end face of a third split magnetic core, with a second gap provided therebetween in the left-right direction. The first to fourth end faces have a mutually parallel relationship.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority of the prior Japanese Patent Application No. 2015-091657, filed on Apr. 28, 2015, the entire contents of which are incorporated herein by reference.

FIELD

The technology disclosed in the present application relates to a core divided by a plurality of gaps.

BACKGROUND

A magnetic core used in devices such as a coil, a transformer, and a noise filter has gaps provided midway on the magnetic path to suppress the occurrence of magnetic saturation. Examples of this magnetic core include an annular magnetic core, a portion of which is cut out by a cutting process to form a gap that connects the inside space with the outside space of the magnetic core. Nevertheless, when an attempt is made to form such a gap by cutting out a portion of the magnetic core formed into an annular shape by a cutting process, a problem arises that the width of the gap that can be formed is restricted by machining limits, or the width of the gap become distorted, or the like.

In the meantime, it is conceivable to form one core using a plurality of individually separated split magnetic cores, and provide gaps between the split magnetic cores. The magnetic core disclosed in Japanese Laid-open Patent Publication No. 2002-373811A is one core formed by two split magnetic cores. This magnetic core includes spacers inserted into two gaps thereof, and the spacers have a permeability greater than the permeability of air. With such a configuration, the magnetic core suppresses the occurrence of magnetic saturation in each of the split magnetic cores as well as leakage magnetic flux generated from each of the gaps.

SUMMARY

A magnetic core according to an aspect of the technology disclosed in the embodiments of the present application is a magnetic core that is formed into an annular shape to form an insertion hole through which a conductor is inserted and forms an annular magnetic path. The magnetic core includes a first split magnetic core that forms a part of the annular magnetic path, and a second split magnetic core that sandwiches the first split magnetic core at both ends of the first split magnetic core and forms the other part of the annular magnetic path. The first split magnetic core includes a first end face and a second end face respectively provided to both the ends of the first split magnetic core, and the second split magnetic core includes a third end face facing the first end face, and a fourth end face facing the second end face. The first end face, the second end face, the third end face, and the fourth end face are parallel to each other, and a separation distance between the first end face and the second end face in a direction orthogonal to the first end face is short compared to an inner side distance of the insertion hole in the direction.

It is to be understood that both the forgoing general description and the following detailed description are exemplary and explanatory and are not restrictive of the invention.

DESCRIPTION OF EMBODIMENTS

Here, a magnetic core of a comparative example will be described with reference toFIG. 7. A magnetic core200illustrated inFIG. 7is formed into an annular shape with a first split magnetic core211and a second split magnetic core212facing each other in an up-down direction. An insertion hole218formed in a direction orthogonal to the paper surface inFIG. 7is provided in a center portion of the magnetic core200. A rectangular shaped conductive bar219is inserted into the insertion hole218.

The first split magnetic core211and the second split magnetic core212are formed into the same shape, and gaps215,216are provided therebetween in the up-down direction. The gaps215,216are sections facing each other in a left-right direction of the magnetic core200, and are disposed in the center portion in the up-down direction. The gaps215,216each connect the inside space of the magnetic core200with the outside space. The magnetic core200is separated into the first split magnetic core211on an upper side, and the second split magnetic core212on a lower side, with the two gaps215,216placed between the first split magnetic core211and the second split magnetic core212. Further, a spacer221for adjusting a gap width225of the gap215is inserted into the gap215on the left side inFIG. 7. Similarly, a spacer222for adjusting a gap width226of the gap216is inserted into the gap216on the right side inFIG. 7.

When current flows from the back to the front of the paper inFIG. 7through the conductive bar219, for example, a magnetic field is generated around the conductive bar219. This magnetic field is generated in the direction (direction around the annular shaped magnetic core200) indicated by an arrow223inFIG. 7, forming a magnetic path in the magnetic core200that surrounds the conductive bar219. The gaps215,216form non-continuous portions of the magnetic path indicated by the arrow223. Thus, a magnetic resistance of the magnetic core200is adjusted by adjusting the gap width225of the gap215and the gap width226of the gap216using the spacers221,222, making it possible to prevent the occurrence of magnetic saturation.

Further, when the first split magnetic core211and the second split magnetic core212need to be fixed in mutually relative positions, the first split magnetic core211and the second split magnetic core212are fixed, for example, by being adhered by the adhesive spacers221,222, by an insulating resin molded thereon, or by winding an insulating tape member around an outer peripheral surface of the magnetic core200. As illustrated inFIG. 7, for example, an insulating resin228molded on the magnetic core200fixes each member of the magnetic core200, including the first and second split magnetic cores211,212. This resin228is formed by injection molding, and integrated with the magnetic core200and the spacers221,222by insert molding. Nevertheless, the first split magnetic core211and the second split magnetic core212of the magnetic core200may be relatively shifted in position due to the injection pressure of the injection molding, which causes the gap widths225,226to fluctuate. As a result, desired magnetic characteristics may not be obtained, causing difficulties in effectively suppressing the occurrence of magnetic saturation.

The following describes an embodiment of the present invention while referring to the drawings.FIG. 1illustrates a ferrite clamp10according to the embodiment of the present invention in an open state.FIG. 2schematically illustrates a closed magnetic core13with a conductive bar33inserted therethrough and a holding case17(refer toFIG. 1) removed.

As illustrated inFIGS. 1 and 2, the ferrite clamp10includes the magnetic core13and the holding case17. The magnetic core13is, for example, made of a magnetic material such as ferrite, and includes a first magnetic core14and a second magnetic core15. The magnetic core13is formed into an annular shape and has an insertion hole31in the center portion thereof, through which the conductive bar33is inserted. When current flows through the conductive bar33inserted through the insertion hole31, the ferrite clamp10functions as a filter that reduces noise included in the current. It should be noted that, in the following description, as illustrated inFIG. 2, the first magnetic core14and the second magnetic core15of the closed magnetic core13are referred to as the upper side and the lower side, respectively, the left side and the right side of the page surface in the insertion direction of the insertion hole31is referred to as the frontward direction and the backward direction, respectively, and the left side and the right side of the page surface in the direction orthogonal to the up-down direction and the front-back direction are referred to as the leftward direction and the rightward direction, respectively.

The magnetic core13is formed into a substantially rectangular shape having a long outer periphery in the left-right direction as viewed in the front-back direction and a pillar shape whose axis extends in the front-back direction. The insertion hole31is formed in the center portion in the up-down direction and the left-right direction of the magnetic core13, and formed into a substantially rectangular shape that is long in the left-right direction as viewed in the front-back direction. The widths of the insertion hole31in the up-down direction and the left-right direction are large compared to those of the conductive bar33, allowing insertion of the conductive bar33through the insertion hole31. The magnetic core13is divided into the first magnetic core14and the second magnetic core15along planes extending in the front-back direction and the left-right direction that pass through center points of sides extending in the up-down direction. Thus, the first and second magnetic cores14,15are formed into substantially U-shapes that are linearly symmetrical with respect to a line extending in the left-right direction, as viewed in the front-back direction. In the first and second magnetic cores14,15, a planar part41of the first magnetic core14and a planar part51of the second magnetic core15face each other at the divided section of the magnetic core13described above.

The holding case17integrally holds the first and second magnetic cores14,15, and brings the planar parts41,51into contact with each other, allowing the first and second magnetic cores14,15to close together to form the substantially rectangular pillar shape illustrated inFIG. 2. In the holding case17, a first bottomed box-shaped case part21that houses the first magnetic core14, and a second bottomed box-shaped case part22that houses the second magnetic core15are connected in a freely openable and closable manner via a hinge19. The first case part21houses and holds the first magnetic core14so that the bottom portion of the U-shaped first magnetic core14is located on the bottom surface side of the first case part21. Similarly, the second case part22houses and holds the second magnetic core15so that the bottom portion of the second magnetic core15is located on the bottom surface side of the second case part22.

Two rectangular frame-shaped latch frames24are provided on a side wall of the second case part22. This side wall faces, in the left-right direction, a side wall on which the hinge19is formed, with a housing part22A placed therebetween. Latch tabs (not illustrated) that engage with the latch frames24of the second case part22described above and hold the holding case17in a closed state are provided on a side wall of the other first case part21. This side wall faces, in the left-right direction, a side wall on which the hinge19is formed, with a housing part21A of the first magnetic core14placed therebetween. With the latch tabs engaged with the latch frames24, the holding case17holds the magnetic core13in an annular shape.

Further, the first case part21is, for example, formed by injection molding using an insulating resin, and integrated with the first magnetic core14by insert molding. Similarly, the second case part22is formed by injection molding, and integrated with the second magnetic core15by insert molding. Examples of the materials of the first and second case parts21,22include a phenolic resin, an epoxy resin, an unsaturated polyester, and a nylon resin. Further, a portion of the holding case17, such as only the hinge19that requires pliability, may be formed of a material (a nylon resin or the like) different from that of the other sections.

On each of side walls21B facing each other in the front-back direction of the first case part21, a cutout portion21C for inserting the conductive bar33therethrough is formed in correspondence with the insertion hole31of the magnetic core31. The cutout portions21C are each formed into a substantially semi-circular shape as viewed in the front-back direction. Similarly, on each of side walls22B facing each other in the front-back direction of the second case part22, a cutout portion22C is formed into a substantially semi-circular shape.

Further, a flat plate-shaped fixing portion27that protrudes in the front-back direction along the bottom surface of the housing part21A is provided to each of the side walls21B of the first case part21. The pair of fixing portions27are disposed diagonally opposite to each other, with a center of the bottom surface of the housing part21A placed therebetween. A rivet hole27A is provided in each of the fixing portions27, allowing the ferrite clamp10to be fixed to a support body by inserting a rivet (not illustrated) into this rivet hole27A.

FIG. 3illustrates the magnetic core13in the state illustrated inFIG. 2, as viewed from the front. As illustrated inFIGS. 2 and 3, an inner peripheral surface43that forms the U-shape of the first magnetic core14and an inner peripheral surface53that forms the U-shape of the second magnetic core15are disposed facing each other in the up-down direction, thereby forming the insertion hole31of the magnetic core13into a substantially rectangular-shape that is long in the left-right direction.

Further, in the first magnetic core14, a first gap61and a second gap62are formed. The first and second gaps61,62divide the first magnetic core14into three split magnetic cores including a first split magnetic core46, a second split magnetic core47, and a third split magnetic core48. The first and second gaps61,62each connect the inner peripheral surface43and an outer peripheral surface49of the first magnetic core14, and connect the inside space of the annular shaped magnetic core13with the outside space. The first and second gaps61,62may, for example, be formed by cutting out portions of the annular shaped magnetic core13. Alternatively, the first and second gaps61,62may be provided by separately manufacturing the first to third split magnetic cores46to48and adjusting the positions of the first to third split magnetic cores46to48.

The first and second gaps61,62are formed in different positions in a section extending in the left-right direction of the first magnetic core14. In other words, the first and second gaps61,62are provided in different positions in a circumferential direction of the annular shaped magnetic core13. Of the first to third split circumferential cores46to48, the first split circumferential core46is disposed on the right side of the second split circumferential core47disposed on the leftmost side, with the first gap61placed therebetween in the left-right direction. In the first gap61, a first end face46A of the first split magnetic core46and a third end face47A of the second split magnetic core47face each other with a predetermined first gap width GW1therebetween. The first end face46A and the third end face47A are each formed by a rectangular flat surface that extends in the up-down direction and the front-back direction. A first spacer63is inserted and disposed in the first gap61.

Further, the third split magnetic core48is disposed on the right side of the first split magnetic core46, with the second gap62placed therebetween in the left-right direction. In the second gap62, a second end face46B of the first split magnetic core46and a fourth end face48B of the third split magnetic core48face each other with a predetermined second gap width GW2therebetween. A length of the second gap width GW2is, for example, the same as that of the first gap width GW1. The second end face46B and the fourth end face48B are each formed by a rectangular flat surface that extends in the up-down direction and the front-back direction. The respective surface areas of the second end face46B and the fourth end face48B are, for example, the same as those of the first end face46A and the third end face47A. A second spacer64is inserted and disposed in the second gap62.

Then, in the magnetic core13of the present embodiment, the direction orthogonal to both the first end face46A and the third end face47A of the first gap61, and the direction orthogonal to both the second end face46B and the fourth end face48B of the second gap62extend in the left-right direction (one example of the separation direction). In other words, the first to fourth end faces46A,46B,47A,48B have a mutually parallel relationship. Furthermore, the first to fourth end faces46A,46B,47A,48B are in the same position in the up-down direction and the front-back direction. Further, as illustrated inFIG. 3, in the direction (separation direction) orthogonal to the first end face46A, the separation distance between the first end face46A and the second end face46B, that is, a length L1of the first split magnetic core46in the left-right direction, is shorter compared to an inner diameter L2of the insertion hole31in the left-right direction. As a result, when the first split magnetic core46is moved in the up-down direction from the state illustrated inFIG. 3, the first split magnetic core46comes into contact with neither the second split magnetic core47nor the third split magnetic core48, allowing movement while keeping the first and second gap widths GW1, GW2constant.

The conductive bar33is, for example, made of a conductive material such as copper or aluminum and the like, and is formed into a rectangular plate shape that is long in the front-back direction. The conductive bar33connects terminals of various devices, and transmits signals or electric power. When current (noise current) flows through this conductive bar33in the direction indicated by the arrow E inFIG. 2, a magnetic field is generated around the conductive bar33. This magnetic field forms a magnetic path in the magnetic core13that surrounds the conductive bar33, as indicated by the arrow M inFIG. 3. At this time, as the current flowing through the conductive bar33increases, the magnetic core13becomes more susceptible to exceeding a magnetization capacity (saturation magnetic flux density) and becoming magnetically saturated. Then, when the magnetic core13is magnetically saturated, the effect of noise component removal is lost.

Here, the first and second gaps61,62described above are provided to the first magnetic core14of the magnetic core13. The first and second gaps61,62form non-continuous portions of the magnetic path extending in the circumferential direction of the magnetic core13. Further, the first and second spacers63,64are respectively provided to the first and second gaps61,62. Examples of the first and second spacers63,64include a metal piece (copper, silver, or the like) made of a non-magnetic material having the same or substantially the same permeability as air. The first and second spacers63,64have, for example, the same permeability. The first and second gaps61,62and the first and second spacers63,64are magnetic resistance in the magnetic path of the magnetic field generated in the magnetic core13. As a result, provision of the first and second gaps61,62and the like decreases the magnetic flux density of the magnetic field generated in the magnetic core13, suppresses the magnetic saturation of the magnetic core13, and improves the efficiency in removing noise component. Note that the first and second spacers63,64are not limited to the metal piece made of a non-magnetic material, and may be made of a non-magnetic resin material or a combination of these materials.

Incidentally, in the above-described embodiment, the conductive bar33is an example of a conductor. The second magnetic core15, the second split magnetic core47, and the third split magnetic core48are examples of the second split magnetic core. The length L1is an example of the separation distance.

As described in detail above, in the ferrite clamp10of the above-described embodiment disclosed in the present application, the first end face46A of the first split magnetic core46faces the third end face47A of the second split magnetic core47with the first gap61provided therebetween in the left-right direction. Further, the second end face46B of the first split magnetic core46faces the fourth end face48B of the third split magnetic core48with the second gap62provided therebetween in the left-right direction. The first to fourth end faces46A,46B,47A,48B have a mutually parallel relationship.

The following describes, for example, a magnetic core13A in which the first split magnetic core46is shifted leftward (toward the second split magnetic core47) in the left-right direction due to injection pressure when the first case part21is formed by insert molding with the first magnetic core14, as illustrated inFIG. 4. Note that, in the following description, the same components as those of the magnetic core13illustrated inFIG. 3are denoted using the same symbols, and descriptions thereof will be omitted as appropriate.

In the magnetic core13A illustrated inFIG. 4, a second gap width GW2A has increased to the extent that a first gap width GW1A has decreased as a result of the position shift of the first split magnetic core46.

The first spacer63of the first gap61is, for example, compressed by the first split magnetic core46moved by injection pressure to the extent that the width of the first gap61has decreased from the first gap width GW1illustrated inFIG. 3to the first gap width GW illustrated inFIG. 4. On the other hand, in the second gap62, a gap67is formed between the second end face46B and the second spacer64in the left-right direction to the extent that the width of the second gap62has increased from the second gap width GW2illustrated inFIG. 3to the second gap width GW2A illustrated inFIG. 4. A resin that constitutes the first case part21is molded on the magnetic core13. The gap67is formed in the second gap62. Nevertheless, because the first to fourth end faces46A,46B,47A,48B have a mutually parallel relationship as described above, the total value of the first and second gap widths GW1A, GW2A is the same as the total value of the first and second gap widths GW1, GW2of the magnetic core13, which has not shifted in position, illustrated inFIG. 3.

Further, the magnetic resistance of each of the first and second gaps61,62fluctuates in proportion to the first and second gap widths GW1, GW2. On the other hand, whether there is one gap or a plurality of gaps, the magnetic resistance of the gap(s) having the same total gap width will become constant if all other factors are conditionally the same. Then, in the first magnetic core14of the present embodiment, the first to fourth end faces46A,46B,47A,48B are mutually parallel and have the same surface area. Further, the first and second spacers63,64in the first and second gaps61,62have the same permeability, and are formed of a non-magnetic material having the same or substantially the same permeability as air. Preferably, if a relative permeability is one, the first spacer63has the same relative permeability before and after compression. As a result, the magnetic resistance of the first and second gaps61,62of the magnetic core13of the present embodiment is the same as the magnetic resistance (including that of an air layer of the gap67) of the first and second gaps61,62of the magnetic core13A (illustrated inFIG. 4) in which the first split magnetic core46shifts in position. That is, the magnetic characteristics, such as the filter characteristics, of the magnetic core13and the magnetic core13A are the same. Note that, for example, even when the second spacer64is fixed (e.g., affixed) to the second end face46B and the fourth end face48B that sandwich the second spacer64at both ends of the second spacer64and is stretched in accordance with the movement of the first split magnetic core46illustrated inFIG. 4. Even if the gap67is not formed, the magnetic resistance (magnetic characteristics) before and after the movement are the same.

Next, as an example, a case where a first split magnetic core211of the magnetic core200of the comparative example illustrated inFIG. 7moves downward will be described.FIG. 8illustrates, for example, the first split magnetic core211shifted downward in the up-down direction due to injection pressure during injection molding. In a magnetic core200A illustrated inFIG. 8, the end faces that constitute the other gap216are positioned in a direction along the end surfaces that constitute the gap215. As a result, in the magnetic core200A, the gaps215,216do not have a relationship of canceling between increases and decreases in gap widths225A,226A in response to a position shift of the first split magnetic core211. Then, in the magnetic core200A, the gap widths225A,226A of both of the gaps215,216are decreased by the same amount in response to a position shift of the first split magnetic core211. The total value of the gap widths225A,226A of the gaps215,216of the magnetic core200A decreases compared to the total value of the gap widths225,226of the magnetic core200(illustrated inFIG. 7) without the position shift. As a result, in the magnetic core200A illustrated inFIG. 8, the magnetic resistance of the two gaps215,216are both smaller compared to those of the gaps215,216of the magnetic core200inFIG. 7, making it difficult to maintain desired magnetic characteristics.

In contrast, in the magnetic core13of the present embodiment illustrated inFIG. 3, the magnetic resistance, that is, the magnetic characteristics such as filter characteristics, of the first and second gaps61,62are the same compared to those of the magnetic core13A (refer toFIG. 4) in which the first split magnetic core46has shifted in position. As a result, even if the first split magnetic core46has shifted in position, the magnetic characteristics are maintained, making it possible to effectively suppress the occurrence of magnetic saturation.

Further, the first and second gaps61,62of the present embodiment are formed in different positions in a section extending in the left-right direction of the first magnetic core14. The section in which the first and second gaps61,62of this first magnetic core14are formed constitutes one side extending in the left-right direction of a portion of the annular shaped magnetic core13. In such a configuration, when the first and second gaps61,62are formed by a cutting process, for example, it is possible to divide the magnetic core13into the first to third split magnetic cores46to48by cutting, in the up-down direction, the section that extends in the left-right direction. As a result, the mutually parallel first to fourth end faces46A,46B,47A,48B can be readily formed compared to the case, for example, where a curved section of the first magnetic core14is cut.

Note that the technology disclosed in the present application is not limited to the above-described embodiment and, needless to say, various modifications and changes may be made without departing from the spirit of the present application.

For example, while the first to fourth end faces46A,46B,47A,48B of the first magnetic core14of the magnetic core13are in the same position in the up-down direction and the front-back direction, and the outer peripheral surfaces49of the first to third split magnetic cores46to48are flush in the above-described embodiment, the present application is not limited thereto. For example, as illustrated inFIG. 5, the position of the first split magnetic core46may be shifted downward (to the inner diameter side of the magnetic core13) compared to the positions of the second split magnetic core47and the third split magnetic core48. Note that, in the following description, the same components as those of the above-described embodiment are denoted using the same symbols, and descriptions thereof will be omitted as appropriate.

The first split magnetic core46of a magnetic core13B illustrated inFIG. 5is shifted toward the conductive bar33where the inner peripheral surface46C comes into contact with the conductive bar33. When the first split magnetic core46is disposed in a position where the first split magnetic core46comes into contact with or comes close to the conductive bar33, the insulation properties between the first split magnetic core46and the conductive bar33are preferably maintained. For example, the first split magnetic core46may be made of a material having low conductivity or insulation properties. Alternatively, the conductive bar33may have an insulating resin or the like molded thereon. Further, the first magnetic core14may have an insulating resin or the like molded on the whole periphery thereof including the inner peripheral surface46C.

Further, positions of the first and second gaps61,62of the magnetic core13B differ from those of the magnetic core13of the above-described embodiment. Specifically, the third end face47A of the second split magnetic core47is formed in a section formed extending in the up-down direction on the left side of the inner peripheral surface of the insertion hole31. Similarly, the fourth end face48B of the third split magnetic core48is formed in a section formed extending in the up-down direction on the right side of the inner peripheral surface of the insertion hole31. Further, the section including the second magnetic core15, the second split magnetic core47, and the third split magnetic core48has a U-shaped cross section when cut on a plane orthogonal to the front-back direction. The third end face47A and the fourth end face48B of the magnetic core13B are each provided on the inner diameter side of the U-shaped core that includes the second magnetic core15and the like. Further, the first split magnetic core46is provided on the U-shaped inner diameter side, the first end face46A faces the third end face47A, and the second end face46B faces the fourth end face48B. In the magnetic core13B, the surface area of the third end face47A is larger compared to that of the first end face46A. Further, the surface area of the fourth end face48B is larger compared to that of the second end face46B. On the other hand, the first end face46A and the second end face46B have the same surface area, and the surface area of the section of the third end face47A that faces the first end face46A is the same as the surface area of the section of the fourth end face48B that faces the second end face46B.

In such a configuration, when the first split magnetic core46is moved downward from a position on an opening side (upper side inFIG. 5) of the U-shaped core (second magnetic core15, and the like), in other words, a position where the outer peripheral surface of the first split magnetic core46is flush with those of the second split magnetic core47and the third split magnetic core48, toward the conductive bar33, the first end face46A and the second end face46B always face the third end face47A and the fourth end face48B, respectively, while remaining parallel. Thus, in the magnetic core13B, even if the first split magnetic core46is shifted in either the left-right direction or the up-down direction by injection pressure or the like, it is possible to maintain constant magnetic resistance of the first and second gaps61,62. Then, in the magnetic core13B, similar to the magnetic core13of the above-described embodiment, it is possible to maintain desired magnetic characteristics with respect to a position shift of the first split magnetic core46.

Further, the magnetic field generated by the current that flows through the conductive bar33forms the magnetic path in the magnetic core13B as indicated by the arrow M1inFIG. 5. This magnetic path changes in position of formation and decreases in inner diameter by the movement of the first split magnetic core46, which has high permeability compared to air, toward the conductive bar33(downward side). As a result, the magnetic core13B has a shorter magnetic path length compared to that of the magnetic core13(refer toFIG. 3) of the above-described embodiment. Here, the magnetic path length of the magnetic core13B is inversely proportional to inductance. Thus, in the magnetic core13A, it is possible to improve magnetic characteristics such as filter characteristics by shortening the magnetic path length to increase inductance.

Further, a thickness in the up-down direction of the first split magnetic core46may be decreased compared to those of the second split magnetic core47and the third split magnetic core48, as in a magnetic core13C illustrated inFIG. 6, for example. The first split magnetic core46is provided in a position in which a midpoint thereof in the up-down direction matches midpoints of the third end face47A and the fourth end face48B in the up-down direction.

With such a configuration, when the first split magnetic core46is shifted upward or downward while being located between the second split magnetic core47and the third split magnetic core48, the first end face46A and the second end face46B always face the third end face47A and the fourth end face48B, respectively, while remaining parallel. As a result, with the magnetic core13C, similar to the magnetic core13B illustrated inFIG. 5, it is possible to maintain desired magnetic characteristics with respect to position shifts in the left-right direction and the up-down direction of the first split magnetic core46.

Further, while the magnetic core13is fixed by the holding case17molded on the magnetic core13in the above-described embodiment, the method of fixing the magnetic core13is not limited thereto. For example, the first and second magnetic cores14,15of the magnetic core13may be fixed by latches or the like provided to the holding case17. Further, the first and second magnetic cores14,15may be fixed by winding an insulating tape member around the outer peripheral surface49of the magnetic core13. Further, the first to third split magnetic cores46to48of the first magnetic core14may be fixed to each other by the first and second adhesive spacers63,64.

Further, for example, in the magnetic core13B illustrated inFIG. 5, the magnetic core13B and the conductive bar33may be fixed to each other by an elastic member or the like that biases the first split magnetic core46toward the conductive bar33located below the first split magnetic core46. Furthermore, the positions of the first and second magnetic cores14,15may be fixed by combining the methods, such as by molding and the tape member, described above.

Further, in the above-described embodiment, the holding case17may be molded on the insertion hole31side (inner peripheral surfaces43,53) of the magnetic core13(the first magnetic core14and the second magnetic core15).

Further, in the above-described embodiment, the holding case17may be omitted. For example, the magnetic core13may be fixed in an annular shape using a tape member. With such a configuration, even if the first split magnetic core46is shifted in position before and after being fixed by the tape member, it is possible to maintain the desired magnetic characteristics.

Further, in the above-described embodiment, the magnetic core13may be configured without the first and second spacers63,64.

Furthermore, while a non-magnetic material is used for the first and second spacers63,64in the above-described embodiment, a magnetic material (such as a ferrite sheet) may be used when the fluctuation in the magnetic resistance in response to the movement of the first split magnetic core46is permitted to a certain degree, for example.

Further, while the above embodiment has described the conductive bar33as an example of the conductor of the present application, the conductor is not limited thereto. The conductor of the present application may be a power cable or a signal line that transmits a signal between various devices.

Further, the shape and quantity of each member of the present embodiment are merely examples and may be changed as appropriate. For example, three or more gaps may be provided to the first magnetic core14. Further, gaps may be provided to both the first magnetic core14and the second magnetic core15. Further, the second magnetic core15, the second split magnetic core47, and the third split magnetic core48may be integrally formed. Furthermore, the magnetic core13is not limited to a substantially rectangular pillar shape, and may be another shape, such as a circular pillar shape, that allows insertion of a conductor such as the conductive bar33.

The following lists aspects of the embodiment of the present invention. The magnetic core forms the annular magnetic path by the first and second split magnetic cores. The first end face of the first split magnetic core faces the third end face of the second split magnetic core, and a gap can be formed therebetween. Further, the second end face of the first split magnetic core faces the fourth end face of the second split magnetic core, and a gap can be formed therebetween. Here, a magnetic resistance of each gap is proportional to the width of the gap. Further, whether there is one gap or a plurality of gaps, the magnetic resistance of gap(s) having the same total value gap width will become constant if all other factors are conditionally the same.

In the magnetic core of the present application, the first to fourth end faces have a mutually parallel relationship. Here, it is assumed that, for example, when the magnetic core is subject to injection molding, the first split magnetic core moves to one side in the separation direction due to the injection pressure so that the gap between the first end face and the third end face narrows, in other words, the gap between the second end face and the fourth end face widens. In this case, because the first to fourth end faces have a mutually parallel relationship, the total value of the widths of the two gaps is the same or substantially the same as the total value of the widths of the gaps before the first split magnetic core is moved by the injection pressure. Thus, when such a magnetic core provided with gaps is fixed by any of a variety of methods, such as by molding or a tape member, it is possible to maintain desired magnetic characteristics even if at least one of the first and second split magnetic cores moves and then the width of each of the gaps changes, by maintaining the total value of the widths of the gaps before the movement.

Further, the magnetic core of the present application may be configured so that the first split magnetic core extends in the direction orthogonal to the first end face, and the first end face and the second end face face each other in the direction orthogonal to the first end face.

In such a magnetic core, the first split magnetic core constitutes one side extending in the direction orthogonal to the first end face in a portion of the annular shaped magnetic core. With such a configuration, the mutually parallel first to fourth end faces can be readily formed. Specifically, when a portion of the annular shaped magnetic core is cut by a cutting process to form the first to fourth end faces, the first to fourth end faces may be formed by cutting a section (side), which is provided to the portion of the magnetic core and extends in one direction, in a direction orthogonal to the first end face. This cutting process is easy compared to a process of cutting a curved section of the magnetic core to form the first to fourth end faces.

Further, in the magnetic core of the present application, the second split magnetic core may be formed to have a U-shaped cross section, and the first split magnetic core may be disposed so that the first and second end faces face the third and fourth end faces, respectively, the third and fourth end faces being provided on an inner side of the U-shaped cross section of the second split magnetic core.

In such a magnetic core, the first split magnetic core is disposed in a space on the inner side of the second split magnetic core having a U-shaped cross section, and the first and second end faces face the third and fourth end faces, respectively. In such a configuration, when the first split magnetic core is moved from an opening side toward a bottom portion side of the U-shaped second split magnetic core, the first and second end faces always face the third and fourth end faces, respectively, making it possible to maintain a constant magnetic resistance in the gaps. Furthermore, the first split magnetic core is shifted to the inner side of the U-shaped second split magnetic core, thereby shortening a magnetic path length of the annular magnetic path. As a result, the magnetic path length of the magnetic field generated in the magnetic core by current flowing through the conductor inserted in the insertion hole is shortened and inductance is increased, making it possible to improve magnetic characteristics, such as filter characteristics.

According to the magnetic core of the technology disclosed in the present application, it is possible to suppress the effects of a position shift of a split magnetic core on magnetic characteristics.