JP2597779B2 - Inductor and manufacturing method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inductor suitable for use in applications such as a noise filter, a band-pass filter, and a choke coil for blocking an AC signal, and a method of manufacturing the inductor.

[0002]

2. Description of the Related Art An inductor is used as a common mode or normal mode noise elimination filter or a bandpass filter in combination with a capacitor, and is also used alone to eliminate an unnecessary AC signal as a choke coil. Also used for. Such an inductor usually has a core wound with a copper wire, and has a core shape such as a toroidal shape, a pot shape, an EI shape, and an EE shape.
The material is also various, such as a metal dust core (a dust core), an amorphous core, and an oxide ferrite core. In any case, the core itself is formed of a tangible dense body. Here, the toroidal core is a ring, the EI core is a combination of E type and I type, and the EE core is a combination of E type and E type, which is very common. There is a combination of a C-type core and a T-type core as disclosed in Japanese Unexamined Patent Publication No. 60-61708.

[0003] As an improvement technique of an inductor using the above-mentioned tangible core, an E-shaped core having a coil mounted thereon and an opponent I-shaped core have been proposed.
Type core or a T type core with a similar coil and C
A coil winding is first applied to a mold core in which a mold core is joined with a ferromagnetic powder containing an adhesive (Japanese Utility Model Application Laid-Open No. 59-171315) or a dust core having a gap. When a direct current is applied to the wire, the magnetic powder is adsorbed in the gap, and at the same time, is impregnated with an insulating resin and solidified.
No.-32495) or magnetic powder is preformed to prepare a plurality of core pieces in advance, and then one of these core pieces is prepared.
There is a method in which a wire is applied to one piece, assembled with another core piece, and further subjected to pressure molding (JP-A-59-63809). These are all intended to make the winding to the core easier. Based on the same idea, there is a type in which a coil is fitted in a mold or a case, a mixture of a magnetic powder and a thermosetting resin powder is poured, heated and cured (Japanese Patent Application Laid-Open No. 54-13994). In addition, although not related to the simplification of the winding, as an aim of omitting the core molding, a ring-shaped insulating resin case is filled with iron powder whose particle surface is insulated, There is a technique of winding a copper wire from the outside to form a toroidal coil (Japanese Patent Application Laid-Open No. 53-20562).

[0004]

The manufacturing process of the iron powder dust type toroidal coil will be described by way of example. As the manufacturing process, compaction molding and curing of the core, insulation coating of the molded core with an epoxy resin or the like, Each process of copper wire winding and soldering to the core is required, but each process is troublesome, and there is a problem with the so-called lead time length that it is not possible to move to the next process unless the previous process is completed was there. In addition, since the manually processed portion occupies a considerable weight, there are many problems in production such as high cost and low productivity.
Furthermore, metal-based dust coils have important Q values (=
1 / tan δ) and the L value (inductance) are low overall.

[0005] Among the above-mentioned known techniques,
In the publication 1708, two types of core molding are required,
It is necessary to improve the finishing accuracy of the mating surface, and in other cases, resin molding as a core or an adhesive is necessary, so that the heat curing treatment cannot be omitted, or JP-A-53-20562. As described above, there still remains a complicated problem in the manufacturing process, such as the need for toroidal hand winding.

The present invention advantageously solves the above-mentioned problems, and has not only a short lead time, but also an inductor that can be automated, has high productivity, is low in cost, and has extremely excellent characteristics. With its advantageous manufacturing method.

[0007]

According to the inductor of the present invention, the whole air-core coil wound uniaxially is buried in a ferromagnetic powder so that the coil extends from the center axis of the coil toward the outside of the coil. A closed magnetic path is formed via the ferromagnetic powder. That is, the present invention is an inductor (first invention) in which the entire air-core coil non-toroidally wound in a uniaxial direction is embedded in ferromagnetic powder.

Further, according to the present invention, a coil obtained by applying a winding to an insulating bobbin having a hollow core portion is inserted into a storage case having an open end with the center axes of both coils being coincident with each other. Fill the ferromagnetic powder so that the entire coil is buried,
Thereafter, there is provided a method of manufacturing an inductor, which comprises sealing an opening of a case (second invention).

Hereinafter, the present invention will be described specifically. FIG.
Next, a preferred example of the inductor according to the present invention is shown in a longitudinal section. In the figure, number 1 is an insulating bobbin, 2 is a coil winding, 3
Is a case, 4 is a ferromagnetic powder, 5 is a sealing portion, and 6 is a coil lead wire. In this figure, the protective insulating film on the outer peripheral portion of the coil winding, the pins for attaching the inductor to the substrate, and the like are omitted, but it goes without saying that these are necessary. In the present invention, the ferromagnetic powder may be a metal-based or non-metal-based powder, and an amorphous alloy-based powder (including a pulverized powder) can also be used. Further, a mixture thereof may be used. Non-metals include Mn-Zn, Cu-Zn, Mg
Soft ferrite powders such as -Zn and Ni-Zn are particularly suitable. The cross-sectional shape of bobbin 1 and case 3
Although a corner or a circle may be used, a round shape is usually easier to handle. The material of the case 3 may be any of metal and plastic, but plastic is easy to manufacture. In a general inductor, the larger the magnetic path cross-sectional area and the shorter the magnetic path length, the higher the inductance. Therefore, even in the inductor of the present invention, in the direction of increasing the cross-sectional area and decreasing the height. Dealing with it has good consequences.

Next, a method for manufacturing such an inductor will be described, but the manufacturing process is extremely simple. (1) First, prepare a coil storage case with one end opened. (2) Next, a coil is formed on the insulating bobbin whose core is hollow. At this time, the outermost peripheral portion of the winding is protected by winding an insulating tape or the like. Also, the portion of the lead wire portion inside the inductor is protected by covering it with an insulating tube. (3) While matching the axial direction of the coil prepared in step (2) with the axial direction of the case prepared in step (1), fix the coil to the center of the case by an appropriate method. (4) Thereafter, the ferromagnetic powder is filled so that the entire coil wound on the bobbin is buried. (5) Finally, after the lead wires are drawn out and the pins for attaching the inductor to the substrate are fixed, the opening of the case is sealed with a resin or the like.

As described above, in the inductor of the present invention,
Since a tangible core is not used for the core material and the winding does not need to be wound in a toroidal shape, fully automated production is possible.
Moreover, since it is only necessary to separately prepare the coil wound around the case or the bobbin and the ferromagnetic powder and finally load the inside of the case, the lead time can be greatly reduced. As described above, the closed magnetic path is formed by the filled ferromagnetic powder.

[0012]

According to the present invention, an inductor is formed by placing a coil automatically wound on a bobbin in a case, filling the coil with a ferromagnetic powder, and forming the closed magnetic circuit by using the powder as a core material. As a result, in addition to being superior in productivity, the production time can be significantly reduced, and the product yield can be significantly increased, thereby enabling cost reduction. In addition, the degree of freedom of the shape is large, the core molding machine and firing furnace,
No coating device or the like is required, which is extremely convenient for production. Further, since the powder is filled as it is, magnetic saturation is unlikely to occur, and the energy absorption is increased, and the noise suppressing effect is correspondingly increased.

[0013]

EXAMPLES In the manner described below, inductors according to Examples 1 to 8 and Comparative Examples 1 to 5 were manufactured, and the frequency was adjusted to 10 and 10 at a voltage of 1 V using an impedance meter.
The inductance L (μH), the quality factor Q, the phase angle θ (°), and the impedance | Z | (Ω) were measured at various changes of 0,1000 kHz. The obtained results are shown in Table 1 for Examples 1 to 4, Table 2 for Examples 5 to 8, and Table 3 for Comparative Examples 1 to 5, respectively. FIGS. 2 and 3 show the results of examining the frequency characteristics of L and Q for some of the examples and comparative examples, respectively.

[0014]

[Table 1]

[0015]

[Table 2]

[0016]

[Table 3]

Example 1 A copper wire having a thickness of 0.6 mm was wound around a plastic bobbin for 30 turns, and an insulating tape was wound around the outer periphery of the bobbin.
φ, 4mmH of the coil, the inner dimension is 26mmφ,
After loading the center of the 10mmH plastic case with the center axis aligned, fill the case with -149 μm Cu-Zn soft ferrite powder to completely wrap the coil, and finally pull out the lead wire and open it. The part was sealed with resin to form an inductor.

As is clear from Table 1, the inductor according to the present invention has a lower inductance L even at higher frequencies.
And Q (the reciprocal of the loss coefficient) did not decrease, and especially Q showed a high value exceeding 70. This is a very high value as compared with iron powder dust-based toroidal coils (Comparative Examples 1 and 2) of the same dimensions to be described later, and thus can be expected to be used as a low-pass filter in combination with a capacitor.
In addition, the inductance is sufficiently high and the impedance in a high frequency range is large, so that it is expected to be used as a choke coil.

Example 2 Example 1 was the same as Example 1 except that the filler powder was changed from soft ferrite powder to sendust alloy powder of -44 μm.
An inductor was formed in the same manner as described above. As shown in Table 1, L, Q and | Z | were slightly lower than those in Example 1, but the tendency to increase as the frequency increased was as follows.
Same as Example 1. Note that L, Q, and | Z | were sufficiently high values as compared with Comparative Examples 1 and 2.

Example 3 An inductor was formed in the same manner as in Example 1 except that the filler powder was changed from soft ferrite powder to -62 μm magnetite powder. As shown in Table 1, Q and | Z | increased as the frequency increased, as in Example 1, but L showed a slight decreasing tendency. Although L, Q, and | Z | were relatively low as compared with Examples 1 and 2, it was nevertheless generally higher than Comparative Examples 1 and 2, and especially Q on the high frequency side was a sufficiently high value. there were.

Example 4 An inductor was formed in the same manner as in Example 1, except that the filler powder was changed to metal-based iron powder. As shown in Table 1, this inductor exhibited a high inductance exceeding 100 μH, and the impedance was sufficiently high. On the other hand, Q shows a maximum around 50 kHz (Fig. 3
(See (a)), as in Comparative Examples 1 and 2, there was a tendency to decrease at higher frequencies. However, the value was still relatively higher than Comparative Examples 1 and 2.

Fifth Embodiment In the first embodiment, the coil winding size of the bobbin is set to 33 mm.
φ, 27mmφ, 4mmH, and the inside dimension of the case is 41mmφ,
An inductor was formed in the same manner as in Example 1, except that the magnetic path cross-sectional area of the coil portion was 5 times that of Example 1. In this case, the magnetic path length was 1.4 times that of the first embodiment, and 5 / 1.4 = 3.5. In other words, the inductance was predicted to be 3.5 times that of the first embodiment. The value was 208 μH, which was 2.4 times that of Example 1. Although L and | Z | increased with an increase in frequency, Q showed a peak value of 96.6 at 200 KHz and then showed a tendency to decrease, exhibiting a behavior different from that of Example 1.

Example 6 A filler was prepared by mixing Cu-Zn ferrite powder and iron powder used in Examples 1 and 4 in a volume ratio of 1 to 1, that is, 50% each, as a filler. An inductor was formed in the same manner as in Example 1. As shown in Table 2, L, Q, and | Z |
As is clear from the comparison between FIG. 3B and FIG. 3A, the peak value is relatively high from the vicinity of over 30 kHz as compared with the fourth embodiment, and its peak is approximately equal to that of the fourth embodiment. In contrast to 50 kHz, in this example the frequency shifted to a high frequency side of about 100 kHz. It can be seen that the characteristics are improved by mixing the ferrite powder with the iron powder.

Example 7 Water vapor was passed through the iron powder used in Example 4 while heating it at 650 ° C. for 30 minutes in the air to oxidize the particle surface to magnetite. Using this iron powder as a filler, an inductor was formed under the same conditions as in Example 1 except for all the other conditions. As shown in Table 2, L and | Z | at each frequency showed almost intermediate values between the iron powder of Example 4 and the magnetite of Example 3. On the other hand, Q had a peak at about 100 kHz as in Example 6, but was relatively lower than Example 6. Nevertheless, it still showed a higher value than that of Example 4 on the high frequency side exceeding 80 kHz. As in this example, even when the surface of the iron powder particles is oxidized and electrically insulated, if the inside of the particles is essentially metal and the particles are large, the loss increases on the high frequency side and the Q value increases. It can be seen that is decreased. This is considered to be due to eddy currents induced inside the particles.

Example 8 An inductor was formed in the same manner as in Example 1 except that the filler was changed to -10 μm carbonyl iron powder. As shown in Table 2, L shows a high value exceeding 75 μH, which is almost the same as that of Example 7, and | Z |,
θ also showed a value similar to that of Example 7. However, Q showed a behavior similar to the ferrite powder of Example 1, and
The particle size of No. 7 was significantly different from that of the iron powder having a relatively coarse particle size. As described above, in the case where the particles are fine, even if the particles are essentially metal, it is considered that the eddy current hardly occurs in the particles, so that the loss on the high frequency side is kept small. It should be noted that high-pressure water-atomized iron powder of -44 μm and the like also showed a similar behavior to carbonyl iron powder regardless of annealed powder or unannealed powder, although the Q value was relatively low.

Comparative Example 1 As a core, the density was 6.5 g / cm ³ , the dimensions were 20.8 mmφ, 12.3 mm
A copper wire with a thickness of 0.6 mm is toroidally wound around a φ, 6.5 mmH, iron powder-based toroidal dust core coated with epoxy resin for 30 turns, and then L, Q under the same conditions as in Example 1. , θ, | Z | were measured. As shown in Table 3, L decreased in the high frequency range (see FIG. 2A), and Q gradually decreased after showing a peak value of 26 at 50 kHz (see FIG. 3A). Moreover, when compared with Example 1,
These values themselves were also quite low.

COMPARATIVE EXAMPLE 2 An inductor was formed in the same manner as in Comparative Example 1, except that a coarser iron powder than Comparative Example 1 was used, and a dust core having the same core size as that of Comparative Example 1 having a lower core density of 6.0 g / cm ³ was used. . As shown in Table 3, L and Q were lower than in Comparative Example 1.

Comparative Example 3 A coil having the same dimensions and the same conditions as those used in Examples 1 to 4 was measured without any air core, and as shown in Table 3,
L, Q and | Z | all showed much lower values than Examples 1-4. In addition, L, |
Z | was generally low.

COMPARATIVE EXAMPLE 4 A coil having the same dimensions and the same conditions as those used in Example 5 was measured without any air core, and L, Q and | Z | were all considerably lower than those in Example 5. . As is apparent from the comparison between Comparative Examples 3 and 4 and Examples 1 to 4 and 5, formation of a closed magnetic circuit around the coil by the ferromagnetic powder is an extremely important factor.

Comparative Example 5 A container made of plastic and having inner dimensions of 26 mmφ, 9 mmφ, and 10 mmH was prepared, and Cu-Zn of -149 μm was used as in Example 1.
Filled with ferrite powder, a 0.6 mm thick copper wire was wound in a toroidal shape from the outside of this case for 30 turns.
As shown in Table 3, this inductor has almost the same external dimensions as those of the first to fourth embodiments, but L, | Z | is considerably lower than those of the first to fourth embodiments, and the Q value has a low value up to 100 kHz. Indicated. However, these Q values exceeded the order of Example 4 → Example 3 → Example 2 → Example 1 between 100 and 500 kHz, and showed a value of about 102 at 1000 kHz. However, it is extremely difficult to automatically perform the toroidal winding as in this example, and in addition to the reduction in productivity, the cost increases and the problem remains due to the low L, │Z│. .

[0031]

As described above, according to the method of the present invention, the automatic production of inductors is possible and the process can be greatly shortened, so that low-cost production can be expected, as well as stable quality and miniaturization of products. The merit is considerable, for example. In addition, since the inductor of the present invention has a high Q and a high L in characteristics, it can be used in combination with a capacitor.
Alternatively, it can be applied to use alone as a choke coil, and its application and use are wide-ranging.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a preferred inductor according to the present invention.

FIG. 2 is a diagram illustrating frequency dependence of an inductance L in Examples 1 to 8 and Comparative Examples 1 and 2.

FIG. 3 is a diagram illustrating frequency dependence of a quality factor Q in Examples 1 to 8 and Comparative Examples 1 and 2.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Insulating bobbin 2 Coil winding 3 Case 4 Ferromagnetic powder 5 Sealing part 6 Lead wire

Claims (2)

(57) [Claims] An inductor formed by embedding an entire air-core coil wound non-toroidally in a uniaxial direction in ferromagnetic powder. 2. A coil obtained by winding a coil on an insulating bobbin having a hollow core portion is placed in a storage case having an open end.
A method of manufacturing an inductor, comprising: loading the two coils with their central axes aligned, filling the ferromagnetic powder so that the entire coil is buried, and then sealing the opening of the case.