Magnetic element

The magnetic element includes a core (20) provided with a through hole (21) passing through a tubular portion, a linear conductor (30) having a plated surface, which is to be inserted through the through hole (21), and a mounting terminal with its one end side is electrically connected to the conductor and another end side positioning on a bottom surface (22a) of the core (20), the mounting terminal being mounted to an external mounting substrate facing the bottom surface (22a). Further, the conductor (30) is provided integrally with the mounting terminal composed of a downward extension (31) extending from the one end side of the conductor (30) to the bottom surface (22a) side and formed by bending itself and a mounting portion (32) positioning on the bottom surface (22a) and formed by bending itself. Furthermore, a certain number of bottom surface recessed portion(s) (23) is/are provided in the bottom surface (22a) to fit the mounting portion(s) (32) of the mounting terminal(s) therein corresponding to the number of the mounting terminal(s), in which the depth of the bottom surface recessed portion (23) is designed to be smaller than the thickness of the mounting portion (32).

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority of Japanese Patent Application Number JP2004-307693, filed on Oct. 22, 2004, the complete disclosure of which is hereby incorporated by reference.

FIELD OF THE INVENTION

The present invention relates to a magnetic element used for various electric products such as a power supply section of a computer.

DESCRIPTION OF THE RELATED ART

For instance, in a power supply section or the like of a computer, a switching element that operates at a high frequency (driven at a high frequency) is used in a switching circuit. When the operating frequency is high in the switching circuit as described above, a magnetic element used in the circuit is required to have a slight inductance value. As one kind of the magnetic element having such a slight inductance value, there is one disclosed in Japanese Patent Number 3366916 (refer to FIG. 2, paragraph No. 0011 and so on) (Patent document 1).

In the magnetic element disclosed in Patent document 1, a hollow portion passing longitudinally through a core of an almost rectangle shape is provided, and only a single band-shaped electric conductor (conductor) is provided inside the hollow portion along the longitudinal direction thereof. Further, the end portion of the conductor protrudes from the hollow portion and bent toward the bottom face side of the core.

By adopting such a configuration, the magnetic element with a small outside dimension and in the state of having a slight inductance value can be realized, the magnetic element further exhibiting a favorable direct current superposition characteristic and allowing a large current flow as well.

Meanwhile, in the magnetic element disclosed in the Patent document 1 described above, a surface-mount terminal, which is formed by the conductor bent after passing through the hollow portion, is mounted onto a substrate or so forth. In that case, the width of the hollow portion is substantially the same as of the conductor and when only a single conductor is inserted through the hollow portion, no positional displacement of the conductor is caused in the width direction of the hollow portion, arising no specific problem. However, for example, when two conductors are inserted through the hollow portion, a positional displacement between these two terminals causes a short or so forth, being undesirable. Further, even if it is a single conductor, when the conductor has a space between an internal wall surface of the hollow portion and itself, a positional displacement of the terminal may lead to a slight vibration, being a problem.

Further, the positional displacement caused in the hollow portion of the conductor frequently affects the characteristics of the magnetic element. Consequently, another problem with the respectively produced magnetic elements have different properties will arise as well.

SUMMARY OF THE INVENTION

The present invention has been made on the basis of the above-described circumstances, and an object thereof is to provide a magnetic element capable of positioning a conductor and reducing an outside dimension thereof.

In order to bring a solution to the above-mentioned problems, the magnetic element according to the present invention is a magnetic element comprising: a core formed by sintering a ferrite material to have a tubular shape and including a tubular portion and a through hole passing through the tubular portion; a conductor having a linear shape, electrical conductivity and a plating performed onto a surface thereof, the conductor being to be inserted through the through hole; and a mounting terminal with one end side of the mounting terminal being electrically connected to the conductor and another side of the mounting terminal positioning at a bottom surface of the core, the mounting terminal being to be mounted on an external mounting substrate facing the bottom surface, in which the conductor is formed integrally with the mounting terminal and the mounting terminal includes a downward extension extending from the one end side of the conductor to the bottom surface side of the core formed by bending and a mounting portion positioning on the bottom surface of the core formed by bending, and in which a number of piece(s) of bottom surface recessed portion(s) corresponding to a number of piece(s) of the mounting terminal(s) is/are provided in the bottom surface, the bottom surface recessed portion being to insert the mounting portion therein.

When it is thus configured, the conductor and the mounting terminal are formed integrally, so that the downward extension and mounting portion of the mounting terminal can be formed by bending the conductor. Further, the mounting portion is fitted into the bottom surface recessed portion provided on the bottom surface of the core. Therefore, the positioning of the conductor can be performed easily and surely by simply fitting the mounting portion in the bottom surface recessed portion. Furthermore, the mounting portion is fitted into the bottom surface recessed portion, so that the conductor can reduce its shake. Moreover, the positioning of the conductor is performed by fitting the mounting portion in the bottom surface recessed portion, so that the fluctuation in the characteristics of the magnetic elements can be reduced, facilitating the property designing. In addition, the thickness of the magnetic element can be reduced to the extent that the mounting portion is fitted in the bottom surface recessed portion, so that the height reduction and downsizing of the magnetic element are enabled.

Further, another invention is the magnetic element in which, in addition to the above, the number of piece(s) of end surface recessed portion(s) corresponding to the number of piece(s) of the mounting terminal(s) to fit the downward extension(s) of the mounting terminal(s) therein is/are provided on an end surface having an opening of the through hole of the core.

When it is thus configured, the downward extension is fitted in the end surface recessed portion provided on the end surface of the core in addition to the bottom surface recessed portion. Therefore, the positioning of the conductor can be performed more easily and surely. Further, by fitting the downward extension to the end surface recessed portion, the shaking of the conductor can be reduced. Furthermore, the positioning of the conductor is performed by fitting the downward extension in the end surface recessed portion, so that the fluctuation in the characteristics of the magnetic elements can be reduced, facilitating the property designing. In addition, the size in the longitudinal direction of the through hole of the magnetic element can be reduced to the extent that the downward extension is fitted in the end surface recessed portion, so that the downsizing of the magnetic element is enabled.

Furthermore, still another invention is the magnetic element in which, in addition to the above, the plurality of conductors are inserted through the through hole along a longitudinal direction of the through hole while the conductors are in the state of being distant from each other. When it is thus configured, the magnetic element can be used for various usage such as an inductor, noise filter, common choke coil, transformer, or the like used, for example, in a high-frequency-driven circuit, in accordance with the number of conductors thereof.

According to the present invention, it is possible to position a conductor easily in a magnetic element. Further, the magnetic element can reduce its outside dimension.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Hereinafter, a magnetic element10according to an embodiment of the present invention will be described based onFIGS. 1 to 3.FIG. 1is a perspective view showing an entire configuration of the magnetic element10in which a bottom surface22ais arranged to position upward.FIG. 2is a front view showing the configuration of the magnetic element10. Further,FIG. 3is a sectional side view showing the configuration of the magnetic element10.

Note that, in the description below, topside indicates an upper surface22cside being distant from the later-described bottom surface22a, and a bottom side indicates a side at which later-described bottom surface recessed portion23is provided. Further, a height direction indicates a vertical direction between the upper surface22cand the bottom surface22ain the magnetic element10.

The magnetic element10according to the embodiment of the present invention includes a core20and conductors30, as shown inFIG. 1and so forth. Of these, the core20is made of Mn—Zn ferrite in view of a material. However, the material of the core20is not limited to the Mn—Zn ferrite, and various kinds of magnetic materials such as Ni—Zn ferrite, sendust (Fe—Si—Al: iron-silicon-alminium), permalloy (Fe—Ni), Fe—Si—Cr, or the like are also acceptable.

Further, the core20has almost a rectangular solid shape in appearance. Specifically, among six outer surfaces22composing the core20of the almost rectangular solid shape, such an outer surface that directly faces a mounting substrate (not shown) (the outer surface positioning upside inFIG. 1, the surface will be referred to as the bottom surface22ain the description below) and the upper surface22cin parallel therewith are designed to have the largest surfaces out of the six outer surfaces22. Note that, in the description below, the six outer surfaces22include side surfaces22b,22dbeing in parallel with the longitudinal direction of a through hole21and end surfaces22e,22frespectively having an opening of the through hole21, in addition to the bottom surface22aand upper surface22c. In the description referring to these plural outer surfaces22, the bottom surface22a, upper surface22c, side surfaces22b,22d, and end surfaces22e,22fare also referred to as the outer surfaces22ato22f, respectively.

The core20is provided with the through hole21. The through hole21is provided along in the longitudinal direction of the core20to pass through the core20in the longitudinal direction. Further, an inside wall surfaces (not shown) composing the through hole21are distant from the outer surfaces22ato22dby a predetermined size, respectively. Notwithstanding the above, in order to ensure the moldability of the through hole21, the through hole21is designed to have a certain height or more. Incidentally, the height of the through hole21is set to 0.1 mm at minimum, as an example. Besides, the width of the through hole21is designed to be enough larger than the height.

Note that the core20finally has a tubular shape in appearance due to the through hole21thereof, and therefore, of the core20, the thick wall portion except the through hole21corresponds to a tubular portion. The tubular shape does not mean that the cross-sectional geometric shape is of any particular shape. While shown as a rectangular tube inFIG. 1, the core can be any shape (circular, elliptical, etc.)

Further, in the core20, the bottom surface recessed portions23are provided on the bottom surface22afacing the mounting substrate. The bottom surface recessed portions23are recessed by a predetermined size toward the upper surface22cside from the bottom surface22a. Corresponding to the number of the conductors30, two pieces of bottom surface recessed portions23are provided in the present embodiment. Here, inside the through hole21, the conductors30are disposed along the longitudinal direction of the core20. Accordingly, the bottom surface recessed portions23are also provided along the longitudinal direction of the core20even to go through the bottom surface22a. Consequently, the two bottom surface recessed portions23have a groove shape, respectively, in appearance.

Besides, the bottom surface recessed portions23are provided at substantially symmetric positions by sandwiching a center line in the longitudinal direction of the bottom surface22aof the core20therebetween. These two bottom surface recessed portions23are a certain size distant from each other. Therefore, it is configured that no short arises between the two conductors30even if they are fitted into the bottom surface recessed portions23by being bent.

Note that the depth of the bottom surface recessed portion23is designed to be smaller than the thickness of a later-described mounting portion32. Therefore, when the mounting portions32are fitted into the bottom surface recessed portions23, the mounting portions32are in a state of protruding from the bottom surface22a.

Further, the conductor30is an elongate member of a flat (zonate) shape, as shown inFIG. 1, and is made of a metal such as copper when it comes to a material. Note that the material of the conductors30is not limited to copper and any material is acceptable as long as the material exhibits a low electric resistance and flexibility. The thicknesses of the conductors30are designed to be smaller than the height of the previously-described through hole21, allowing to insert themselves easily into the through hole21.

The surfaces of the conductors30are plated. The plating has a two-layered structure, in which a first layer (at a host material side such as of copper) in the plating process is composed of a material having favorable adhesiveness to the host material. As an example material exhibiting such favorable adhesiveness, there is a Ni-plated layer with respect to copper. Also, the second layer in the plating process is composed of a material to ensure wettability with respect to a solder when mounting. As an example material to ensure such wettability, there is a Sn-plated layer.

Further, as shown inFIGS. 1 to 3, of the conductor30, a terminal portion (corresponding to a mounting terminal) protruding from the through hole21is bent downwardly along the end surfaces22e,22fof the core20. In the description below, this portion (part of the mounting terminal) is defined as a downward extension31. Further, the downward extension31extends to the bottom surface22a, and after reaching to the bottom surface22a, the downward extension31is bent along the bottom surface22athis time. In this case, the lower end of the downward extension31is bent to fit into the bottom surface recessed portion23. In the description below, of the downward extension31(conductor30), a portion (part of the mounting terminal) to be fitted into the bottom surface recessed portion23is defined as a mounting portion32. The mounting portion32is directed to a side leaving from the downward extension31, and only a predetermined length thereof is fitted into the bottom surface recessed portion23along therewith.

Hereinafter, the description will be given of a manufacturing method to manufacture the magnetic element10of the above-described configuration. First, a molded body being a base of the core20is formed by Mn—Zn Ferrite, and then the molded body is sintered. At this time, for example, another bushing for molding is inserted into such a portion of the molded body that corresponds to the through hole21. With the bushing, the through hole21is formed in the magnetic element10after the sintering. Note that the through hole21may be formed by a cutting work after the molded body is sintered. Further, the bottom surface recessed portions23are formed with respect to the molded body. The bottom surface recessed portion23is formed by cutting a predetermined depth the surface of the bottom surface22a.

After the core20is formed, subsequently, the two pieces of conductors30having a predetermined length are inserted into the inside of the through hole21. After the insertion, the portions of the conductors30protruding from the through hole21are bent at almost a right angle toward the bottom surface22a. After this bending, the conductors30are bent at almost a right angle along the bottom surface22a. In this bending, such portions of the conductors30that are to be bent are bent while positioning so that the portions are fitted into the bottom surface recessed portions23. With these bendings, the downward extensions31and mounting portions32are formed. Note that an unnecessary portion of the mounting portions32may be cut before or after the bendings of the conductors30. Further, such two bendings may be performed sequentially or concurrently using, for example, a pressing machine or the like. As described above, the magnetic element10is completed. Note that the bottom surface recessed portions23may be formed before or after the sintering step of the core20.

According to the magnetic element10of the above-described configuration, the bottom surface recessed portions23are provided on the bottom surface22a, and the mounting portions32formed by bending the conductors30are fitted into the bottom surface recessed portions23. Hence, the conductors30are positioned simply by fitting the mounting portions32into the bottom surface recessed portions23. In other words, with the provision of the bottom surface recessed portions23, the conductors30can be positioned easily and surely. Backed by this, it is possible to prevent a short between the two conductors30, and therefore, the problem that the magnetic element10is damaged by the short can be prevented.

Further, the mounting portions32are fitted into the bottom surface recessed portions23, so that shakings of the conductors30can be reduced. Furthermore, since the mounting portions32are fitted into the bottom surface recessed portions23, the conductors30are positioned, so that the fluctuation in the properties of the magnetic element10can be reduced and the properties/quality of the magnetic element10can be stabilized.

Moreover, since the mounting portions32are fitted into the bottom surface recessed portions23, the height of the magnetic element10can be reduced to the extent of the fitted length. With this, the size in the height direction of the magnetic element10can be reduced, allowing the magnetic element10to be downsized.

The description has been given of the one example configuration of the magnetic element10according to the embodiment of the present invention. However, the magnetic element according to the present invention is not limited to the above-described magnetic element10and a variety of modifications can be made thereto. Modification examples are shown inFIGS. 4 to 11.

A magnetic element11shown inFIG. 4has a bottom surface recessed portion of a shape differently from that of the magnetic element10shown inFIG. 1. Specifically, the bottom surface recessed portion231of the magnetic element11shown inFIG. 4is not provided for each conductor30. In other words, in the magnetic element11, plural (two in the present embodiment) conductors30are disposed in the same bottom surface recessed portion231.

In this case, for positioning the conductors30, the respective conductors30are disposed along the respective edge portions of the bottom surface recessed portion231. By doing this, the respective conductors30can be positioned. Also, in the magnetic element11, the conductors30position in the bottom surface recessed portion231, so that the height of the magnetic element11can be reduced, allowing the magnetic element11to be downsized.

Further, a magnetic element12shown inFIG. 5has a bottom surface recessed portion231similar to that of the magnetic element11shown inFIG. 4. However, the magnetic element12has end surface recessed portions232on the end surfaces22e,22fin addition to the bottom surface recessed portion231. The end surface recessed portions232are formed to retire by a predetermined length from the end surfaces22e,22fand provided to cross the end surfaces22e,22ffrom the bottom surface22ato the through hole21.

The downward extensions31are fitted into such end surface recessed portions232. Backed by this, the downward extensions31are prevented from protruding in the longitudinal direction of the magnetic element12, so that the longitudinal size of the magnetic element12can be reduced. In other words, the magnetic element12can be downsized further. Moreover, the downward extensions31are fitted into the end surface recessed portions232, so that the positioning of the conductors30can be performed more surely.

Here, in the magnetic element12shown inFIG. 5, the depth of the end surface recessed portion232is designed to be larger than the thickness of the downward extension31(conductor30). Backed by this, the downward extensions31are in the state of being recessed from the end surfaces22e,22finstead of protruding therefrom. Therefore, the longitudinal size of the magnetic element12can be reduced, so that the magnetic element12can be downsized.

Note that, inFIG. 5and later-describedFIGS. 6,10,11, the bottom surface recessed portions23,231are provided together with the end surface recessed portions232. However, in the configurations of these drawings, it is possible to adopt a configuration in which only the end surface recessed portions232are provided without providing the bottom surface recessed portions23,231.

Further, a magnetic element13shown inFIG. 6has the same two bottom surface recessed portions23as shown inFIG. 1and the same two end surface recessed portions232as shown inFIG. 5. Combination of these allows further downsizing of the magnetic element13. Moreover, the downward extensions31are fitted into the end surface recessed portions232, so that the positioning of the conductors30can be performed more surely.

Further, a magnetic element14, a magnetic element15, a magnetic element16and a magnetic element17shown inFIGS. 7 to 11, respectively, are configured to have a slit24in addition to the configurations of the magnetic element10, magnetic element11, magnetic element12and magnetic element13shown in the above-describedFIGS. 1 to 6, respectively. The slit24serves as a magnetic gap and is provided to go from the bottom surface22athrough the through hole21and to cross over the bottom surface22aalong the longitudinal center of the bottom surface22a. In other words, the bottom surface22ais designed to be divided into two by the slit24and the two bottom surfaces22aare in the state of not contacting to each other.

In the thus-configured magnetic element14, magnetic element15, magnetic element16and magnetic element17, an improvement in an inductance value (=no decrease) in direct current superposition can be secured in addition to the above-described merits of positioning, height reduction, and so forth. In addition, the slit24is provided on the bottom surface22a. Therefore, for example, in a circuit to which the magnetic element14, magnetic element15, magnetic element16or magnetic element17is mounted, an influence of magnetic flux leakage to the other electronic parts from the above of the respective magnetic elements can be reduced as compared to the case where the slit is provided, for example, on the upper surface22c.

Here, the magnetic element14shown inFIGS. 7 and 8is the one having the slit24formed on the magnetic element10shown inFIGS. 1 to 3. Also, the magnetic element15shown inFIG. 9is the one having the slit24formed on the magnetic element11shown inFIG. 4. Besides, the magnetic element16shown inFIG. 10is the one having the slit24formed on the magnetic element12shown inFIG. 5. Further, the magnetic element17shown inFIG. 11is the one having the slit24formed on the magnetic element13shown inFIG. 6.

Note thatFIG. 7andFIGS. 9 to 11are perspective views showing the configurations of the magnetic elements14to17, respectively. Further,FIG. 8shows the shape of the slit24and is a front view showing the configuration of the magnetic element14.

Further, in the above-described embodiment, the magnetic element10is provided with the two conductors30and the two bottom surface recessed portions23together. However, the number of the conductors30or bottom surface recessed portions23is not limited to two, and one or three or more is also accepted.

Furthermore, in the above-described embodiment, the depth of the bottom surface recessed portion23is designed to be smaller than the thickness of the mounting portion32. However, the depth of the bottom surface recessed portion23may be designed to be the same size as of the thickness of the mounting portion32or larger. Also, when the magnetic element10is thus configured, the magnetic element10can be mounted onto a mounting substrate favorably, provided that, for example, a mounting portion of the mounting substrate protrudes or another conductive member is provided therebetween.

Further, in the magnetic element12shown inFIG. 5described above, the depth of the end surface recessed portion232is designed to be larger than the thickness of the downward extension31(conductor30). However, the depth of the end surface recessed portion232may be the same size as the thickness of the downward extension31(conductor30) or smaller. Also, when the magnetic element12is thus configured, the longitudinal size of the magnetic element12can be reduced in that the downward extensions31(conductors30) are fitted into the end surface recessed portions232.

Furthermore, the usage of the magnetic element according to the present invention has no limitation. For instance, when the magnetic element has only a single conductor, the magnetic element can be used as an inductor, a noise filter or the like used in a high-frequency-driven circuit. Also, when the magnetic element has two or more conductors, the magnetic element can be used as a multiple inductor, a multiple noise filter, a common-mode choke coil, transformer or the like used in the high-frequency-driven circuit.

Note that when the magnetic element is used as the multiple inductor, multiple noise filter, common-mode choke coil, transformer or the like used in the high-frequency-driven circuit, it is desirable to provide a slit passing through the core.

Also, in the above-described embodiment, the core20has almost a rectangular solid shape in appearance. However, the shape of the core is not limited to the almost rectangular solid shape, and various shape such as an almost tubular shape is applicable. Also, the conductor30in the above-described embodiment forms the downward extension31and the mounting portion32by bending itself. In other words, the conductor30is provided integrally with the mounting terminal composed of the downward extension31and mounting portion32. However, the configuration of the mounting terminal is not limited thereto, and a configuration in which a mounting terminal is provided independently from the conductor30may be accepted.

Note that when adopting the independent configuration, for example, in the state where the conductor30is inserted into the through hole21, one end side of the independently-provided mounting terminal processed in advance to have a C shape is inserted into the through hole21in a manner overlapping the conductor30. In this case, a conductive adhesive agent or the like may be coated on one end side of the mounting terminal in advance. If so, the bending process becomes unnecessary after the conductor30is inserted into the through hole21, so that productivity can be improved as well.

Further, in the above-described embodiment, the bottom surface recessed portion23has a groove shape passing through the bottom surface22a. However, the shape of the bottom surface recessed portion is not limited to the groove shape passing through the bottom surface22a. For instance, the bottom surface recessed portions may be designed to recess from the end surfaces22e,22fby a predetermined length along the bottom surface22a.

The magnetic element according to the present invention can be used in the field of electric equipment.