Composite inductor element

A composite inductor includes a block made of resin or rubber having a magnetic material dispersed therein. Spirally wound coils are buried in the block so that the coil axes of the coils are arranged in the same direction. The end portions of the coils are electrically connected to external electrodes provided on two surfaces of the block substantially at a right angle to the axes of the coils.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a composite inductor element. More particularly, the present invention relates to a composite inductor element constructed to function as an anti-noise component in personal computers and other electronic apparatuses.

2. Description of the Related Art

In recent years, software in personal computers has become more and more complicated and advanced. In order to perform instructions contained in such software at high speed, the clock frequency of CPUs in personal computers has greatly increased.

Personal computers have a plurality of types of power supply circuits such as power circuits to drive CPUs, power circuits to drive circuits other than the CPUs, power circuits to drive hard disks, floppy disks and the like, and so on. Among these power circuits, although there are supplying currents as large as tens of amperes, as in the power circuits for driving CPUs having high clock frequencies, there are also other supplying currents as small as hundreds of milliamperes. In each of these power circuits, an anti-noise component having a current capacity corresponding to each supply current is separately required. Up to now, a single element having a current capacity corresponding to the current capacity of each of the power circuits has been used as an anti-noise component.

However, when the above single elements are used in the power circuits of personal computers to function as an anti-noise component, many different types of anti-noise components are required. Accordingly, there is a problem that the cost of anti-noise components is greatly increased and the space occupied by the anti-noise components also increases.

SUMMARY OF THE INVENTION

To overcome the problems described above, preferred embodiments of the present invention provide a composite inductor element which has a significantly reduced cost and greatly reduced space requirement as compared to conventional anti-noise components.

According to a preferred embodiment of the present invention, a composite inductor element includes a plurality of coils buried in a block made up of at least either resin or rubber having magnetic material dispersed therein and the end portions of each of the coils are electrically connected to external electrodes provided on the block. The coils have different electrical characteristics such as current capacity, inductance, and other characteristics.

Therefore, in the block, coils constructed in accordance with the noise and current capacity specifications of power circuits in personal computers, and other apparatuses, are buried. In this way, a plurality of conventional anti-noise components are realized as single-type units.

Further, in a composite inductor element according to a preferred embodiment of the present invention, a plurality of electromagnetically close-coupled coils defined by spirally wound parallel lines are provided and a plurality of conductors integrally coated with insulating coating resin are arranged in parallel. The plurality of coils are buried in a block made up of at least either resin or rubber having a magnetic material dispersed therein.

With the above construction, a composite inductor element acts as a common-mode choke coil, and when common mode noise is applied to each of a plurality of electromagnetically close-coupled coils, the noise is prevented from being transmitted. Thus, an array type composite inductor element having a plurality of common-mode choke coils embedded in a block includes a plurality of spirally wound parallel-wire lines constituting a plurality of electromagnetically close-coupled coils buried in a block while being separated from each other.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Hereinafter, preferred embodiments of a composite inductor element according to the present invention are explained with reference to the attached drawings.

A plan view of a preferred embodiment of a composite inductor element according to the present invention and a front view of this preferred embodiment are shown inFIGS. 1 and 2, respectively. The composite inductor element1includes a plurality of spirally wound coils11,12,13,14(preferably, four coils in the first preferred embodiment) buried in a block2. The block2preferably has a substantially rectangular parallelepiped shape and the coils11–14are preferably arranged such that the axes of the coils extend in the same direction. The block2is preferably made of either resin or rubber having magnetic material of ferrite or other magnetic material, dispersed therein.

External electrodes21athrough24aand21bthrough24bare provided, respectively, on two opposite side portions2aand2bof the block2. The end portions11tand11tof the coil11are electrically connected to the external electrodes21aand21b, respectively, the end portions12tand12tof the coil12are electrically connected to the external electrodes22aand22b, respectively, the end portions13tand13tof the coil13are electrically connected to the external electrodes23aand23b, respectively, and the end portions14tand14tof the coil14are electrically connected to the external electrodes24aand24b, respectively. The external electrodes21athrough24aand21bthrough24bcan be formed, for example, by applying and hardening conductive paste of Ag, Ag—Pd, Ni, and other suitable material, on the side portions2aand2bof the block2. Further, the external electrodes21athrough24bmay be constructed using metal caps preferably having a substantially U-shape which is made up of silver or other suitable material. After the metal caps have been attached to the side portions2aand2bof the block2, the caps are electrically connected to the end portions11tthrough14tof the coils11through14preferably via soldering or spot welding.

A composite inductor element1having such a construction is mounted, for example, as an anti-noise element for power circuits in personal computers. The coils constructed in accordance with the noise and current capacity specifications of the power circuits in the personal computers where the element1is to be mounted are buried inside of the block2. As a result, a plurality of conventional anti-noise elements are realized in a single unit. Accordingly, the cost of providing anti-noise measures is greatly reduced and the space occupied by anti-noise elements is greatly reduced.

Next, one example of a manufacturing method of a composite inductor element1is explained with reference toFIGS. 3 through 5. First of all, pellets of PPS resin (polyphenylene sulfide resin) mixed with 90 wt % of ferrite powder are prepared. Further, sets of spirally wound coils11through14, which are needed for one molding shot, are prepared.

Next, as shown inFIG. 3, after the coils11through14have been put on pins41through44provided on a lower mold31for injection molding, an upper mold32and the lower mold31are joined together. Next, the PPS pellets mixed with ferrite prepared in the above process are melted and injected between the lower mold31and upper mold32as shown by arrows A1, and thus, a first injection molding is performed. After that, the lower mold31is removed to pull out the pins41through44from the coils11through14, and, a second injection molding is performed in order to fill the hollow portions previously occupied by the pins41through44, using the same melted PPS pellets mixed with ferrite as in the first injection molding. Thus, as shown inFIG. 4, a molded part34, in which coil sets33of the coils11through14of one molding shot (namely, four sets) are buried, is manufactured.

The molded part34is cut at locations shown by one-dot chain lines L1using a slicing machine, a dicing cutter, or other suitable device, to produce blocks2. The blocks2are further cut at the locations shown by one-dot chain lines L2inFIG. 5and the end portions11tthrough14tof the coils11through14, respectively, buried inside of the blocks2become exposed on the surface of the blocks2. Furthermore, conductive paste is applied and hardened on the side portions2aand2bwhere the end portions11tthrough14tof the coils11through14, respectively, are exposed. Thus, the external electrodes21athrough24aand21bthrough24belectrically connected to the end portions11tthrough14tof the coils11through14, respectively, are formed. In this way, via a molding process and a cutting process using resin material suitable for mass production, a composite inductor element1can be efficiently manufactured.

Another preferred embodiment of a composite inductor element according to the present invention will now be explained. In a composite inductor element51, the plan view of which is shown inFIG. 6, four coils61through64having different numbers of windings (that is, different inductances), which are different from those of the composite inductor element1of the first preferred embodiment, are buried in a block2. The number of windings of the coils61through64is determined individually based on the noise and current capacity specifications of the power circuits of the personal computers or other electronic apparatuses, to which the composite inductor element51is connected. On two opposite side portions2aand2bof the block2, external electrodes21athrough24aand21bthrough24bare provided, respectively. End portions61tand61tof the coil61are electrically connected to the external electrodes21aand21b, respectively, end portions62tand62tof the coil62are electrically connected to the external electrodes22aand22b, respectively, end portions63tand63tof the coil63are electrically connected to the external electrodes23aand23b, respectively, and end portions64tand64tof the coil64are electrically connected to the external electrodes24aand24b, respectively.

Further, in a composite inductor element71, the plan view of which is shown inFIG. 7, four coils61athrough64ahaving different numbers of windings and different coil wire thicknesses and different coil diameters, which are different from the case of the composite inductor element1of the first preferred embodiment, are buried in a block2. The wire thicknesses, numbers of windings, and coil diameters of the coils61athrough64aare determined individually based on the noise and current capacity specifications of the power circuits of the personal computers or other electronic apparatuses to which the composite inductor element71is connected. On two opposite side portions2aand2bof the block2, external electrodes21athrough24aand21bthrough24bare provided, respectively. End portions61tand61tof the coil61aare electrically connected to the external electrodes21aand21b, respectively, end portions62tand62tof the coil62aare electrically connected to the external electrodes22aand22b, respectively, end portions63tand63tof the coil63aare electrically connected to the external electrodes23aand23b, respectively, and end portions64tand64tof the coil64aare electrically connected to the external electrodes24aand24b, respectively.

In the composite inductor elements51and71having such a construction, a combination of coils61through64and61athrough64acan be changed, for example, in accordance with the current capacity and noise elimination characteristics corresponding to a plurality of power circuits of personal computers or other electronic apparatuses.

Another preferred embodiment of a composite inductor element according to the present invention will now be explained. A perspective view, a longitudinal sectional view, and a right-side view of a composite inductor element81are shown inFIGS. 8,9, and10respectively. The composite inductor element81preferably includes two electromagnetically close-coupled coils91and92. The two coils91and92are preferably made of a parallel-wire line94in which two conductors91aand92aintegrally coated with insulating coating resin93are arranged in parallel. The parallel-wire line94is spirally wound around one coil axis and buried in a block2having a substantially rectangular parallelepiped shape. The block2is preferably made of either resin or rubber having magnetic material of ferrite or other magnetic material dispersed therein.

On two opposite side portions2aand2bof the block2, external electrodes21aand21b, and22aand22bare provided. The end portions91tand91tof the coil91are electrically connected to the external electrodes21aand21b, respectively, and the end portions92tand92t(not illustrated) of the coil92are electrically connected to the external electrodes22aand22b, respectively.

In the composite inductor element81having such a construction, the two coils91and92are arranged to be parallel in the insulating coating resin93and are electromagnetically close-coupled. Accordingly, the composite inductor array element81is a common-mode choke coil of a bifilar type. When common mode noise is applied to each of the coils91and92, the noise is prevented from being transmitted therethrough. Further, because the coils91and92are made up of conductors91aand91b, the cross section of which can be made relatively large, the current capacity is greatly increased in comparison with a composite inductor element of a conventional laminated type where the conductors constituting coils are formed by printing conductive paste. Further, because the two conductors91aand92aconstituting the two coils91and92are covered by insulating coating resin93, the reliability of the insulation between the two coils91and92is also increased.

Next, one example of a manufacturing method of the composite inductor element81is explained with reference toFIG. 11. First, pellets of PPS resin mixed with ferrite powder are prepared. Further, the coils91and92made up of the parallel-wire line94of the two conductors91aand92acontained within the insulating resin93, which is spirally wound around one coil axis, are prepared.

Next, after the spirally wound parallel-wire line94has been put on a pin provided on a lower mold31afor injection molding, an upper mold32aand the lower mold31aare joined together. Next, the PPS pellets mixed with ferrite prepared in the above process are melted and injected between the lower mold31aand upper mold32aas shown by an arrow A1, and thus, a first injection molding is performed. After that, the lower mold31ais removed to pull out the pin41afrom the spirally wound parallel-wire line94, and a second injection molding is performed to fill the concave portion which was occupied by the pin41awith the same melted PPS pellets mixed with ferrite as in the first injection molding. Thus, a molded part having the coils91and92buried therein is produced.

Next, both of the end portions of the molded part are cut off using a slicing machine, a dicing cutter, or other suitable cutting apparatus, to produce the block2. At the side portions2aand2bof the block2, the end portions91tand92tof the coils91and92are exposed. Furthermore, by laser machining and so on, a guide groove95(seeFIG. 10) is formed on the side portions2aand2bof the block2. In accordance with this guide groove95, the end portions91tand92tof the coils91and92are guided respectively, and the end portions91tand92tare set within the guide groove95.

After that, on the side portions2aand2bwhere the end portions91tand92tof the coils91and92are exposed, conductive paste is coated and hardened. Thus, the external electrodes21aand21b, and22aand22belectrically connected to the end portions91tand92tof the coils91and92, respectively, are formed.

Information on the breakdown voltage, the coupling coefficient, and the direct-current resistance of the composite inductor element81manufactured in this way are shown in Table 1. In Table 1, for comparison, the measurements of laminated-type composite inductor elements, in which a plurality of magnetic layers and two sets of conductors defining coils are alternately laminated, are also shown (see Comparative Example 1 and Comparative Example 2). Example 1 was constructed by simply laminating each layer of conductors for defining the coils. Example 2 was constructed by arranging electrical insulation material having lower permeability than that of the magnetic layer between the conductor layers defining the coils.

As clearly seen in Table 1, the composite inductor element81of this preferred embodiment has superior reliability of insulation and a high coupling coefficient. Because the insulating coating resin93of the parallel-wire line94has a high breakdown voltage, the high breakdown voltage of the preferred embodiment was achieved, and thus, selection of the resin to be used the breakdown voltage can be further improved. Further, in the composite inductor element81, the permeability of the block2is about 13, but on the other hand, the permeability of the insulating coating resin93is about 1 and the magnetic reluctance is relatively high. Accordingly, the ratio of the magnetic flux leaking from the coils91and92(short path phenomenon) is relatively smaller than that of the laminated-type composite inductor elements, and the coupling coefficient is greatly improved. Furthermore, in the composite inductor element81, because the conductors of relatively large thickness and made of base metal such as copper and so on can be used as the conductors91aand92a, the problem of wire breakage caused by heating due to a large current is solved.

Although the two coils91and92are formed using the parallel-wire line94in which the two conductors91aand92aare arranged in parallel in the insulating coating resin93, in a composite inductor element101, as shown inFIGS. 12 through 14, three electromagnetically close-coupled coils96,97, and98spirally wound around one coil axis may be formed using a parallel-wire line99in which three (or more than three) conductors96a,97a, and98aare arranged in parallel in an insulating coating resin93, and buried in a block2with magnetic material dispersed therein. As shown inFIG. 14, through the groove guide95aformed in the block2, the end portions96tthrough98tof the coils96through98are electrically connected to external electrodes21athrough23aand21bthrough23b.

Further, the number of parallel-wire lines is not limited to one, and a plurality of spirally wound parallel-wire lines may be buried in a block such that the lines are separated from each other. Thus, because, in a composite an array-type inductor element, a plurality of common-mode choke coils are contained in the block2, the occupied space can also be further reduced.

The present invention is not limited to the above preferred embodiments, but various modifications are possible within the spirit and scope of the invention. For example, in the first and second preferred embodiments, the number of coils are not limited to four, and may be changed to any arbitrary number in accordance with the specification of equipment or product in which an anti-noise component is mounted. Further, apart from a spirally wound form, the coils may be of a linear form or other suitable form.

As clearly understood from the above explanation, according to the present invention, by burying a plurality of coils in a block made of at least either resin or rubber having a magnetic material dispersed therein, a plurality of anti-noise components are able to be realized as single-type units. As a result, the cost of anti-noise measures can be greatly reduced.

Further, since a plurality of electromagnetically close-coupled coils are constructed by spirally winding a parallel-wire line in which a plurality of conductors are integrally coated with insulating coating resin and arranged in parallel and buried in a block, a composite inductor element functioning as a common-mode choke coil having a high breakdown voltage, a large coupling coefficient, and a large current capacity can be obtained.

While the invention has been shown and described with reference to the preferred embodiments, it will be understood by those skilled in the art that the foregoing and other changes in form and details can be made without departing from the spirit and scope of the invention.