JPH1041121A - Coil and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve a coil inductance by giving a taper to the peripheral part of a drum-type core, giving the taper of the same angle to the inner wall of a ferrite core which becomes a cover, and closely adhering them. SOLUTION: A taper of the prescribed angle is given to a ring part at the periphery of a drum-type core 1 and the taper work having the same angle as the drum-type core 1 is given to the inner wall of a recessed-type ferrite core 2. The differences in the sizes of the drum-type core 1 after thermal work and the recessed-type ferrite core 2 are generated but the angle of the taper in the ring part at the periphery of the drum-type core 1 and the taper angle of the inner wall of the recessed-type ferrite core 2 do not change. When the drum-type core 1 after thermal work is covered by the recessed-type ferrite core 2, they are closely adhered to each other. A slight clearance 3 is provided between the upper face of the drum-type core 1 and the upper plane of the recessed-type ferrite core 2, and adhesive is previously applied to the part of a clearance 3. Thus, they can completely and closely be fixed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a small coil, particularly a coil using a drum core, and a method for manufacturing the same.

[0002]

2. Description of the Related Art FIGS. 2 and 3 are explanatory views of a conventional example showing a coil using a drum core. FIG. 2 shows a type in which a winding 5 is simply wound around a drum core 4 and a magnetic circuit 7 is provided. Since the gap of the (magnetic flux passage) is extremely large, only a small inductance can be obtained.

FIG. 3 shows a structure in which a cylindrical ferrite material core 6 is put on a drum-shaped core 4 to shorten the gap length of a magnetic circuit 7 so that a large inductance can be obtained. , Still not getting enough inductance.

When a cylindrical ferrite core 6 is put on the drum-shaped core 4 as shown in FIG. 3, a large gap 8 is formed therebetween. This is because the core is subjected to thermal processing, so that there is a difference in dimensions between the core before thermal processing and the core after thermal processing. Therefore, the dimensions before thermal processing must take into account the dimensional differences (tolerances) caused by thermal processing. Therefore, when the columnar core 6 after the thermal processing is put on the drum-shaped core 4 subjected to the thermal processing, a large gap 8 is generated.

[0005]

As described above, in the conventional coil configuration using the drum core, only a small inductance can be obtained because the gap of the magnetic circuit is extremely large.

Further, when a cylindrical ferrite material core is put on the drum-shaped core, a large gap is formed between the cores, so that a satisfactory inductance cannot be obtained, and there is a problem that the application is limited.

[0007]

SUMMARY OF THE INVENTION Accordingly, the present invention provides a drum-shaped core which is formed by tapering the peripheral portion of the drum-shaped core and the inner wall of the concave ferrite core over the drum-shaped core. By putting a concave ferrite core on the two, both are completely adhered.

Thus, a magnetic circuit having a small gap is formed, and a large coil inductance can be obtained.

[0009]

FIG. 1 is a sectional view showing a coil using a drum-shaped core according to an embodiment of the present invention. In FIG. 2) a ferrite core made of a concave ferrite material, 3 a gap, and 5 a winding wound around the drum core 1.

As shown in FIG. 1, the ring portion around the drum core 1 is tapered at a constant angle, and the concave ferrite core 2 has a tapered inner wall having the same angle as the drum core 1. Processed. Therefore, the dimensional difference (tolerance) occurs between the drum core 1 and the concave ferrite core 2 after the heat processing, but the taper angle of the ring portion around the drum core 1 and the inner wall of the concave ferrite core 2 The taper angle does not change. As a result, when the concave ferrite 2 is put on the drum-shaped core 1 after the thermal processing, the two closely adhere to each other.

However, since a difference in dimensions occurs after thermal processing, a slight gap 3 needs to be provided between the upper surface of the drum core 1 and the upper plane of the concave ferrite core 2. By applying an adhesive to the gap 3 in advance, both can be completely adhered and fixed.

[0012]

As described above, according to the present invention, the peripheral portion of the drum core is tapered, and the inner wall of the ferrite core serving as the lid is also tapered at the same angle so that both are brought into close contact with each other. Therefore, a magnetic circuit having a small gap is formed, and a large coil inductance can be obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a coil using a drum core according to an embodiment of the present invention.

FIG. 2 is an explanatory view showing a coil using a conventional drum-shaped core.

FIG. 3 is an explanatory view showing a coil using a conventional drum-shaped core.

[Explanation of symbols]

 Reference Signs List 1 drum core 2 ferrite core 3 gap 5 winding

Claims (2)

[Claims] 1. A drum core having a ring portion tapered at a constant angle around the drum core, a winding wound around the drum core, and an inner wall tapered at the same angle as the drum core. And a concave ferrite core that covers the drum-shaped core. 2. The method for manufacturing a coil according to claim 1, wherein a ring portion around the drum-shaped core is tapered at a fixed angle, and the inner wall of the concave ferrite core that covers the drum-shaped core is formed on the drum. Applying taper processing at the same angle as the shaped core, providing a gap between the upper surface of the drum-shaped core and the plane of the ferrite core, applying an adhesive to the gap, and covering the drum-shaped core with the ferrite core. A method for manufacturing a coil, comprising: