JP4953380B2 - Coil parts - Google Patents

Description

  The present invention relates to a coil component comprising a bobbin and a core wound with a winding, and more particularly to a coil component in which a gap is formed between opposing magnetic legs.

Conventionally, various coil components such as a choke coil and a transformer have been used in accordance with applications and required characteristics.
For example, the coil component 10 shown in FIG. 7 includes a cylindrical bobbin 5 around which a winding 6 is wound around an outer peripheral portion, and a core 2. The pair of core halves 2a and 2b constituting the core 2 are the same, and the cross-sectional shape is E-shaped. That is, the core half 2a (2b) includes two outer magnetic legs 4a (4b) and one middle magnetic leg 3a (3b) disposed therebetween. The core halves 2a and 2b are arranged so as to face each other so that the middle magnetic legs 3a and 3b and the outer magnetic legs 4a and 4b abut each other.

  In the coil component 10 shown in FIG. 7, a gap 7 is formed between the middle magnetic legs 3a and 3b to prevent magnetic saturation. The gap 7 may be formed between the outer magnetic legs 4a and 4b. In some cases, the gap is formed by sandwiching the gap paper, but the gap 7 in the following description is an air layer formed between the middle magnetic legs 3a and 3b whose tip is ground.

By the way, the coil component 10 in which the gap 7 is formed sometimes generates a roaring sound (hereinafter referred to as “abnormal noise”) due to the vibration of the middle magnetic legs 3a and 3b during driving.
Therefore, in the coil component 10 ′ shown in FIG. 8, the tips of the middle magnetic legs 3 a and 3 b are joined with the adhesive 9 to suppress the vibration of the middle magnetic legs 3 a and 3 b and prevent the generation of abnormal noise. It is out. (For example, refer to Patent Document 1).
Japanese Patent Laid-Open No. 2004-200336

In the conventional coil component 10 ′ shown in FIG. 8, for example, when an adhesive 9 made of an epoxy resin is used to firmly join the tips of the middle magnetic legs 3 a and 3 b, abnormal noise is surely suppressed. .
However, such a coil component 10 ′ may cause another new problem that the core 2 breaks due to a change in ambient temperature. For example, when a thermal shock test in which the temperature is repeatedly raised and lowered in the range of −40 to 125 [° C.] is performed, there is a possibility that the crack 11 is generated at the base portion of the middle magnetic legs 3a and 3b.

On the other hand, it is conceivable to use an adhesive 9 made of another material having a certain degree of elasticity even after being cured. However, when such an adhesive 9 is used, even though the generation of the crack 11 can be prevented, the joining of the middle magnetic legs 3a and 3b becomes weak, so that it is impossible to suppress abnormal noise. End up.
That is, in the conventional coil component 10 ′, it was not possible to prevent the generation of abnormal noise and the crack 11 at the same time.

  Then, this invention makes it a subject to provide the coil components which can suppress the noise resulting from a gap, without generating a crack, even if it performs the thermal shock test which repeats raising / lowering temperature.

The inventor of the present application considered the cause of cracks as follows. That is, the linear expansion coefficient of the ferrite constituting the core is 100 × 10 ⁻⁷ [ppm / ° C.], whereas an adhesive (for example, EP-138 manufactured by CEMEDINE is used as the adhesive). The linear expansion coefficient is 5.7 × 10 ⁻⁷ [ppm / ° C.], and the volume change with respect to the temperature change of the adhesive is very small. Thus, when the linear expansion coefficient of the core and the linear expansion coefficient of the adhesive are greatly different, as shown in FIG. 9, the total length L ′ of the middle magnetic leg and the adhesive at high temperature is the total length of the outer magnetic leg. It becomes shorter than L, and the load concentrates on the base part of the middle magnetic leg. And since this load exceeded M intensity | strength (after-mentioned) of a core, the crack 11 had generate | occur | produced.
Based on such knowledge, the inventor of the present application configured the coil component as follows.

The coil component according to the present invention is
A cylindrical bobbin having a winding wound around an outer peripheral portion, and a pair of core halves in which middle magnetic legs inserted into the bobbin cylinder face each other with a predetermined gap therebetween. In the coil component, at least one of the middle magnetic legs is formed with a middle magnetic leg buffer layer made of a coating agent that covers the opposing surface and the side wall of the tip, and the middle magnetic legs are at least one of the middle magnetic legs. The leg buffer layer is sandwiched and bonded via an adhesive, and the coating agent is made of silicone resin, while the adhesive is made of epoxy resin, and the inner wall of the bobbin and the tip of the middle magnetic leg A side wall is bonded via the adhesive with the middle magnetic leg buffer layer interposed therebetween .

  In the coil component, each of the pair of core halves includes outer magnetic legs that are opposed to each other with a predetermined gap outside the cylinder of the bobbin, and at least one of the opposed outer magnetic legs has an opposed surface and An outer magnetic leg buffer layer made of the coating agent covering the side wall of the tip is formed, and the opposing outer magnetic legs are joined via the adhesive with at least one outer magnetic leg buffer layer interposed therebetween. Preferably it is.

In the coil component, before Symbol silicone resin is preferably selected from silicone varnish group consisting of three-dimensional polymer.

  In the coil component, the coating thickness of the coating agent is preferably 20 μm or more.

Further, in the coil component, the core half body couples the middle magnetic leg, the pair of outer magnetic legs arranged with the middle magnetic leg interposed therebetween, and the middle magnetic leg and the pair of outer magnetic legs. Preferably, the coupling strength between the middle magnetic leg buffer layer and the middle magnetic leg is lower than the M strength of the core half.
As shown in FIG. 10, the M-strength is an E composed of a middle magnetic leg 3a, a pair of outer magnetic legs 4a arranged with the middle magnetic leg 3a interposed therebetween, and a back magnetic leg 12 that couples them. The letter-shaped core half 2a is arranged on the base so that the back magnetic leg 12 is positioned above the middle magnetic leg 3a and the outer magnetic leg 4a (when arranged in this way, "M" in side view). The core half 2a has a strength that can withstand destruction when a load is applied vertically downward from above to the center of the upper surface of the back magnetic leg 12 (the position above the middle magnetic leg). Say. This M intensity is measured using a general-purpose push-pull gauge (load measuring device). Moreover, in general coil components, it is prescribed | regulated that M intensity | strength has 180 [N] or more.

  ADVANTAGE OF THE INVENTION According to this invention, even if it performs the thermal shock test which repeats raising / lowering temperature, a coil component which can suppress the noise resulting from a gap without generating a crack can be provided.

  Hereinafter, a coil component according to an embodiment of the present invention, and a coil component according to a comparative example and a conventional example in which a comparative test is performed will be described with reference to the drawings.

[Example]
FIG. 1 shows a coil component according to the embodiment.
The coil component 1 includes a cylindrical bobbin 5 around which a winding 6 is wound around an outer peripheral portion, and a PQ type core 2. The pair of core halves 2a and 2b constituting the core 2 are the same, and the cross-sectional shape is E-shaped. That is, the core half 2a (2b) includes two outer magnetic legs 4a (4b) and one middle magnetic leg 3a (3b) disposed therebetween. The core halves 2a and 2b are arranged such that the middle magnetic legs 3a and 3b and the outer magnetic legs 4a and 4b face each other. The dimensions of the core 2 are as shown in FIG.

  A gap 7 is formed between the middle magnetic legs 3a and 3b to prevent magnetic saturation and improve the DC superposition characteristics. The gap 7 is formed by uniformly grinding the middle magnetic legs 3a and 3b. As shown in FIG. 2, the gap dimension G is 6 [mm]. The gap dimension G differs depending on the core size. If the core size (W dimension) is 5 [mm] or less and 50 to 100 [μm], and the core size (W dimension) is about 50 [mm], It is set to about 4 to 6 [mm].

  With reference to FIG. 1, in the coil component 1 according to the embodiment, a buffer layer (middle magnetic leg buffer layer) 8 made of silicone resin (coating agent) on each of the opposing surfaces and the tip end side walls of the middle magnetic legs 3 a and 3 b. Is formed. As the silicone resin, one arbitrarily selected from a group of silicone varnishes made of a three-dimensional polymer is used. The buffer layer 8 is applied by immersing it in a dip tank storing a silicone resin.

  The middle magnetic legs 3a and 3b are joined by an adhesive 9 made of epoxy resin with the buffer layer 8 interposed therebetween. In the coil component 1 according to the embodiment, a large amount of adhesive 9 is applied in advance to one or both surfaces of the buffer layer 8 formed on the middle magnetic legs 3a and 3b. Then, the middle magnetic legs 3a and 3b are inserted into the inside of the cylinder of the bobbin 5, and the adhesive 9 protrudes to the side wall side of the tip of the middle magnetic legs 3a and 3b, and the inner wall of the middle magnetic legs 3a and 3b and the bobbin 5 And are joined. As shown in FIG. 1, the tip side walls of the middle magnetic legs 3 a and 3 b and the cylinder inner wall of the bobbin 5 are joined via an adhesive 9 with a buffer layer 8 interposed therebetween.

Although specific test results will be described later, in the coil component 1 according to the example, the buffer layer 8 has the following functions.
That is, when the temperature change is relatively small, the buffer layer 8 itself expands and contracts, so that the load generated at the base portion of the middle magnetic legs 3a and 3b is alleviated and the occurrence of cracks can be prevented (first effect) ).
Further, since the coupling strength between the buffer layer 8 and the middle magnetic legs 3a and 3b is lower than the M strength of the core 2, before the crack occurs due to the load exceeding the M strength applied to the base portions of the middle magnetic legs 3a and 3b. The tip portions of the middle magnetic legs 3a and 3b are pulled out from the cap-shaped buffer layer 8. Thereby, even when the temperature change is relatively large, for example, when the temperature changes from room temperature to 125 [° C.], it is possible to prevent the occurrence of cracks (second effect).

  Furthermore, the middle magnetic legs 3a and 3b in this embodiment are not only joined to each other via the adhesive 9, but also joined to the cylinder inner wall of the bobbin 5 at the tip side wall thereof, and vibrations in all directions are suppressed. Therefore, abnormal noise can also be suppressed (third effect).

Note that, from the viewpoint of suppressing abnormal noise, the buffer layer 8 is essentially unnecessary, so the third effect increases as the coating thickness of the buffer layer 8 decreases. However, when the buffer layer 8 is thinned, the first and second effects are reduced.
Therefore, in the coil component 1 according to the present invention, it is important to make the coating thickness of the buffer layer 8 as thin as possible so that cracks do not occur. For this reason, in this embodiment, the film thickness is set to 20 to 25 [μm]. From such a viewpoint, a coating agent having a relatively low viscosity, for example, a coating agent having a viscosity of about 15 [mPa · s] is preferable.

  As the coating agent, (1) the film thickness can be reduced, (2) it has elasticity, and (3) the bond strength to the core 2 is high (however, it is lower than the M strength of the core 2). Required. For this reason, as a coating agent, what was selected from the silicone varnish group which consists of an above-mentioned three-dimensional polymer is used. In this embodiment, KR251 manufactured by Shin-Etsu Chemical Co., Ltd. is used as the silicone resin agent.

[Comparative Example 1]
FIG. 3 shows a coil component according to Comparative Example 1.
In the coil component 1 ′, the amount of the adhesive 9 to be used is reduced, and the middle magnetic legs 3a, 3b and the inner wall of the bobbin 5 are not joined (the state where the adhesive 9 does not reach the inner wall of the bobbin 5) )It has become. Other elements, for example, the coating thickness of the buffer layer 8, the core dimension, the gap dimension, and the like are all the same as those of the coil component 1 according to the embodiment.

[Comparative Example 2]
FIG. 4 shows a coil component according to Comparative Example 2.
The coil component 1 ″ is obtained by reducing the amount of the adhesive 9 and reducing the coating thickness of the buffer layer 8 to 10 μm or less with respect to the coil component 1 according to the embodiment. For example, the core dimensions, gap dimensions, and the like are all the same as those of the coil component 1 according to the embodiment.

[Conventional example]
FIG. 7 shows a coil component according to a conventional example.
As described above, in the conventional coil component 10, the middle magnetic legs 3 a and 3 b are directly joined by the adhesive 9. Further, the middle magnetic legs 3a, 3b and the inner wall of the bobbin 5 are not joined. Other elements, for example, core dimensions, gap dimensions, and the like are all the same as those of the coil component 1 according to the embodiment.

なお、熱衝撃試験では、“−４０［℃］に設定された槽内で３０分間放置した後、瞬時に１２５［℃］に設定された槽内に移し替えて３０分間放置し、その後、瞬時に−４０［℃］に設定された槽内に移し替え”を１サイクルとし、これを１００サイクル行った後に、コアにクラックが発生しているか否かについて評価を行った。
また、異音測定では、各コイル部品をスイッチング電源回路における力率改善用チョークコイルとして使用した際に、コイル部品から発せられる異音を騒音計（リオン社製ＮＬ−２２）によって測定した。使用した騒音計の測定周波数範囲は、２０〜８ｋ［Ｈｚ］であり、騒音計を直接にコアに当接させて測定した。なお、表１の異音測定結果では、従来例の異音を基準（０［ｄＢ］）として基準値からの変化量を記載した。 [Comparison experiment]
20 coil parts according to the example, comparative example 1 and the conventional example are produced, and 10 coil parts according to comparative example 2 are produced. For each coil part, crack generation after the thermal shock test and driving An abnormal noise was evaluated.
Table 1 shows the evaluation results of each coil component.

In the thermal shock test, after being left in a tank set at “−40 [° C.] for 30 minutes, it was immediately transferred to a tank set at 125 [° C.] and left for 30 minutes. "Transition into the tank set to -40 [° C]" was defined as 1 cycle, and after 100 cycles, the core was evaluated for cracks.
Further, in the abnormal noise measurement, when each coil component was used as a power factor improving choke coil in the switching power supply circuit, the abnormal noise emitted from the coil component was measured with a noise meter (NL-22 manufactured by Rion Co., Ltd.). The measurement frequency range of the used sound level meter was 20 to 8 k [Hz], and the sound level meter was directly brought into contact with the core for measurement. In the abnormal noise measurement results in Table 1, the amount of change from the reference value is described with the abnormal noise of the conventional example as a reference (0 [dB]).

As is apparent from the results shown in Table 1, the coil component 1 (see FIG. 1) according to the example has a conventional example in which the occurrence of cracks in the thermal shock test is suppressed and the middle magnetic legs 3a and 3b are directly joined. Abnormal noise is suppressed to the same extent as (see FIG. 7).
On the other hand, in the coil component 1 ′ according to the comparative example 1 (see FIG. 3), since the middle magnetic legs 3a and 3b and the bobbin 5 are not joined, the middle magnetic legs 3a and 3b vibrate and are compared with the conventional example. Then the abnormal noise worsened by 6 dB.
Further, in the coil component 1 ″ according to the comparative example 2 (see FIG. 4), the noise is deteriorated for the same reason as in the comparative example 1, and the buffer layer 8 has an original function because the application thickness of the silicone resin is too thin. In some samples, cracks occurred.

  As described above, according to the coil component according to the present invention, the middle magnetic legs are joined to each other with the buffer layer interposed therebetween, and the temperature rise and fall are repeated by joining the tip side wall of the middle magnetic leg and the inner wall of the bobbin. Even if it went, it was possible to suppress abnormal noise caused by the gap without generating cracks.

In addition, the coil component which concerns on this invention is not limited to the said structure, A various modification is considered.
For example, in the example and comparative examples 1 and 2, the buffer layer (medium magnetic leg buffer layer) is formed on both of the opposing middle magnetic legs, but the above-described effects are obtained even when formed on only one of them. be able to. However, if the buffer layer is formed on both the middle magnetic legs, the first and second effects can be more effectively exhibited for each middle magnetic leg.

  Further, when a gap is formed on both the middle magnetic leg and the outer magnetic leg, a buffer layer may be formed on both the middle magnetic leg and the outer magnetic leg. That is, as shown in FIG. 5, the middle magnetic leg buffer layer 8a is formed on both (or any one) of the middle magnetic legs 3a and 3b, and both the outer magnetic legs 4a and 4b facing each other are formed. You may form the outer magnetic leg buffer layer 8b which consists of a coating agent which covers the opposing surface and front-end | tip part side wall. The opposing outer magnetic legs 4a and 4b are joined via an adhesive 9 with the outer magnetic leg buffer layers 8b interposed therebetween. In addition, you may form not only in the case where the outer magnetic leg buffer layer 8b is formed in both of the opposing outer magnetic legs 4a and 4b, but in any one.

  The present invention is not limited to a “PQ core” formed by combining core halves having an E-shaped cross-section, and can also be applied to coil components using cores of other shapes. Applicable cores include, for example, an “EI core” (see FIG. 6) formed by combining an E-shaped core half 2a and an I-shaped core half 2b, and an “EE core”.

  Further, the term “coil component” in this specification includes various electronic components such as a choke coil according to the embodiment, a transformer, and the like that are wound around a core.

It is sectional drawing of the coil components which concern on an Example. It is a perspective view of the core used for the coil component which concerns on an Example, the comparative example 1, the comparative example 2, and a prior art example. 6 is a cross-sectional view of a coil component according to Comparative Example 1. FIG. 6 is a cross-sectional view of a coil component according to Comparative Example 2. FIG. It is sectional drawing of the coil components which concern on a modification. It is sectional drawing of the coil components which concern on a modification. It is sectional drawing of the conventional coil components. It is sectional drawing of the coil components which concern on a prior art example. It is a graph which shows the change of the magnetic leg length of each magnetic leg in a thermal shock test. It is a figure for demonstrating M intensity | strength.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Coil components 2 Core 2a, 2b Core half 3a, 3b Middle magnetic leg 4a, 4b Outer magnetic leg 5 Bobbin 6 Winding 7 Gap 8 Buffer layer (coating agent)
8a Middle magnetic leg buffer layer 8b Outer magnetic leg buffer layer 9 Adhesive 10 Conventional coil component 10 'Conventional coil component 11 Crack 12 Back magnetic leg

Claims (5)

A cylindrical bobbin having a winding wound around an outer peripheral portion, and a pair of core halves in which middle magnetic legs inserted into the bobbin cylinder face each other with a predetermined gap therebetween. Coil parts,
At least one of the middle magnetic legs is formed with a middle magnetic leg buffer layer made of a coating agent that covers the opposing surface and the tip side wall, and the middle magnetic legs sandwich at least one of the middle magnetic leg buffer layers, Bonded through an adhesive ,
While the coating agent is made of silicone resin, the adhesive is made of epoxy resin,
A coil component, wherein an inner wall of a cylinder of the bobbin and a side wall of the tip of the middle magnetic leg are joined via the adhesive with the middle magnetic leg buffer layer interposed therebetween . Each of the pair of core halves includes outer magnetic legs facing each other with a predetermined gap outside the cylinder of the bobbin,
An outer magnetic leg buffer layer made of the coating agent covering the opposing surface and the tip side wall is formed on at least one of the opposing outer magnetic legs, and the opposing outer magnetic legs are at least one of the outer magnetic legs. The coil component according to claim 1, wherein the coil component is joined via the adhesive with a leg buffer layer interposed therebetween. The coil component according to claim 1 or 2, wherein the silicone resin is selected from a group of silicone varnishes made of a three-dimensional polymer . The coil component according to claim 1, wherein the coating thickness of the coating agent is 20 μm or more . The core half includes the middle magnetic leg, a pair of outer magnetic legs arranged with the middle magnetic leg sandwiched therebetween, and a back magnetic leg that couples the middle magnetic leg and the pair of outer magnetic legs. Formed in an E shape,
The coil component according to claim 2, wherein the coupling strength between the middle magnetic leg buffer layer and the middle magnetic leg is lower than the M strength of the core half .

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