JPH088120A - Method of manufacturing coil product - Google Patents

Abstract

PURPOSE:To simplify the production process of a coil product by including a core gap forming step in the assembling work of cores by curing adhesives. CONSTITUTION:A lot of spherical or spindle-shaped or spheroidal even grains 1 are kneaded in an adhesive agent 3, this agent is coated on joint faces of cores 2 and hardened in the mutually closely contacted condition of the cores 2 whereby core gaps of a coil prod. are formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coil component used in electronic circuits in general.

[0002]

2. Description of the Related Art In a coil component composed of a combination of a plurality (usually two) of ferrite cores, a gap is formed in the joint surface to form a core gap, thereby intentionally reducing the inductance and using it. There is one that prevents magnetic saturation at the time. Examples of coil components for such applications include choke coils and transformers for flyback DC / DC converters. As a method for forming the core gap, a method in which a resin film having a constant thickness called a spacer is sandwiched between two cores is generally used. FIG. 5 shows a cross-sectional view of the core joining surface of the conventional example in which the spacer 22 is sandwiched between the cores 21. The core 2 is fixed because the mutual positions of the two cores 21 are fixed.
The adhesive tape 23 is wound around the outer periphery of 1. Adhesive tape 23
There is also an example of fixing the core by using a fixing metal fitting having elasticity instead of. Further, as another means for forming the core gap, as shown in FIG.
It is also common practice to grind only one to shorten it and provide a so-called center gap with the I core 26.

[0003]

The conventional core gap forming method shown in FIGS. 5 and 6 has the following problems. (1) When the film-shaped spacer is placed on the joint surface of the core, the thin and lightweight spacer is easy to slip and easily protrude from the joint surface. Also, after inserting the spacer, it is necessary to wind the tape or attach the fixing metal to fix the core immediately, which makes the work complicated and difficult to automate.
For this reason, this work is often performed manually, which is an obstacle to cost reduction. (2) To suppress variations in the amount of gaps formed,
The spacer should cover most of the area of the joint surface of the core. Therefore, it is necessary to prepare spacers having different shapes for each core shape. (3) In the case of the method of polishing the middle foot to obtain the center gap, the work of incorporating the spacer is unnecessary, but the core must be repolished according to the required gap value. This polishing process takes time, and even cores of the same shape have different uses depending on the center gap value, the number of core stocks becomes huge, and their management is complicated. Also, due to a change in production schedule, cores that had once been polished and had a center gap could not be used and became an unnecessary inventory, and in the worst case, the cores had to be discarded. The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method of manufacturing a coil component that achieves simplification of a process for forming a gap.

[0004]

In order to solve the above-mentioned problems, a method for forming a gap, which is described in claim 1 and whose cross section is shown in FIG. 1, is invented. That is, a large number of particles 1 having a uniform particle size are kneaded in advance with the adhesive 3, and this is applied to the joint surface of the core 2 and then the adhesive 3 is cured in the state where the cores 2 are in close contact with each other. Thus, a core gap equal to the particle size of the kneaded particles 1 is formed. The particles used are preferably spherical, but they can be used in a spindle shape as shown in FIG. 2 or a spheroidal shape as shown in FIG. In the case of spindle-shaped particles, the diameter of the thickest part of the particle is the amount of gap. In the case of a spheroidal particle, the height of the particle when the particle is in the most stable posture in terms of gravity is the gap amount. The rod-shaped or fibrous particles as shown in FIG. 4 are not used in the present invention because the particles may overlap each other.

[0005]

The present invention employs a method in which an adhesive, in which a large number of particles having uniform particle diameters are kneaded in advance, is applied to the joining surface of a ferato core, and the adhesive is cured while the cores are in close contact with each other. By doing so, it becomes possible to realize the steps of forming the core gap and fixing the mutual core positions by simple operations of applying and curing the adhesive. It is easy to automate the adhesive application process, and the manual work can be significantly reduced as compared with the conventional gap forming method using a spacer. Further, it becomes unnecessary to manage the inventory of various kinds of cores having different gap values as in the conventional gap forming method by the center gap polishing, and the production management system of coil parts is simplified. Further, the step of polishing the core for forming the center gap becomes unnecessary, and as a result, the manufacturing cost of the coil component can be significantly reduced.

[0006]

Embodiments of the present invention will be described below with reference to the drawings. Example Commercially available glass beads were used as particles to be kneaded with the adhesive. The shape of the glass beads is roughly spherical, but it also contains about 20% of the spindle-shaped particles shown in FIG. 2 and the spheroidal particles shown in FIG. The glass beads were passed through a commercially available standard sieve, and only particles that passed through a 70-mesh (opening diameter of 212 μm) sieve and did not pass through a 83-mesh (opening diameter of 180 μm) sieve were selected. These particles are designated as glass beads A. The accuracy of the opening diameter of the sieve is not very accurate, so two steel plates with good parallelism should be 210μ
Glass beads A
Among the particles, only the particles passing between the slits were separated and used as glass beads B. As the adhesive, a one-part thermosetting epoxy adhesive having a relatively high viscosity (viscosity: 1000 poise) was adopted, and the glass beads A and B were kneaded with this adhesive. The mixing ratio by volume is 75% adhesive and 25% glass beads. The specific gravity of the adhesive is 1.4 and that of the glass beads is 2.5. The material of the particles to be mixed may be of any type as long as the strength and heat resistance are appropriate, but the specific gravity is close to that of the adhesive so that the adhesive and the particles do not separate due to the difference in specific gravity during the coating operation on the core. Is preferable, and resinous particles are optimal if possible. However, if the viscosity of the adhesive is sufficiently high, this point need not be considered. As the ferrite core, Mn-Zn ferrite material SB-7C manufactured by Hitachi Ferrite Co., Ltd. having an EI-25B shape was used. Attach 1 UEW of 0.50mmφ wire rod to the bobbin for this shape.
After winding 0T, as a comparative example, first, a spacer made of polyethylene terephthalate having a thickness of 200 μm was inserted between the E core and the I core into a bobbin, and the insulating tape was wound three times and fixed. The purpose of this coil component is a choke coil, and the inductance is about 1100μH.
The rated current is 1.5A. Next, as an example, the epoxy adhesive obtained by kneading the glass beads A or the glass beads B was applied to the I core, combined with the E core incorporated in the bobbin, and thermally cured at 100 ° C. for 30 minutes. A force of about 300 g was applied when the E core and the I core were put together, but only about 20 g of the dead weight of the core and the bobbin was applied to the joint surface during thermosetting.
The number of prototypes for each of the comparative example, Example A (using glass beads A) and Example B (using glass beads B) was 15 each.
Individual. The results are shown in Table 1. The largest cause of inductance fluctuation is the variation in core gap value. The standard deviation σ of the inductance is larger in the example A than in the comparative example, but in the example B in which the particle diameters are uniform, it is rather smaller than that in the comparative example.

[0007]

[Table 1]

[0008]

According to the present invention, it is possible to include the step of forming the core gap in the core assembling work by hardening the adhesive, which simplifies the manufacturing process of the coil component and reduces the manufacturing cost. You can

[Brief description of drawings]

FIG. 1 is an example of a cross-sectional view of a core joint surface in which a core gap is formed by applying an adhesive obtained by kneading spherical particles to the core joint surface and curing the adhesive according to the present invention.

FIG. 2 is an example of spindle-shaped particles as particles to be kneaded with an adhesive according to the present invention.

FIG. 3 is an example of spheroidal particles as particles to be kneaded with an adhesive according to the present invention.

FIG. 4 is an example of particles (rods) not used in the present invention.

FIG. 5 is a cross-sectional view of a core joining surface of a conventional example in which a core gap is formed by using a spacer.

FIG. 6 is an external perspective view of a set of conventional EI cores in which a core gap is formed by providing a center gap in the middle leg of the E core.

[Explanation of symbols]

 1 particle 2 core 3 adhesive

Claims (1)

[Claims] 1. In a coil component formed by combining a plurality of ferrite cores, a large number of spherical, spindle-shaped or spheroidal particles having a uniform particle size are kneaded with an adhesive, and the resulting ferrite core is used. A coil characterized by forming a core gap by applying the adhesive to each other's joint surfaces and then curing the adhesive in a state where a plurality of ferrite cores are in close contact with each other to bond the ferrite cores together. Manufacturing method of parts.