JPS60264105A - Ferrite antenna - Google Patents

Abstract

PURPOSE:To increase the mechanical strength of a core and to improve the temperature characteristic by winding a coil on a ferrite core formed by inserting an adhesives or a magnetic substance different from plural ferrite plates and the adhesives between said ferrite plates. CONSTITUTION:The ferrite core 11 is formed by adhering the two ferrite plates 11a sliced and plished to a required thickness and the coil 12 is wound thereupon. Epoxy group or vinylbutylal group adhesives is used as the adhesives 14 used for the adhesion and the desired electric characteristic and mechanical strength are obtained by selecting the thickness of the type of material of the adhesives and the thickness of the bonding layer. Since the inductance temperature characteristic of a nickel group ferrite has a positive temperature coefficient, a gap between the ferrite plates 11a is changed by using the type of material having a positive thermal expansion coefficient and a large value for the adhesives 14 and the temperature characteristics of the core 11 is cancelled, thereby improving the temperature characteristic.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a small and thin ferrite antenna that is built into a small radio, a cassette tape recorder with a radio, and the like.

Conventional configurations and their problems In recent years, electronic devices have become increasingly smaller and thinner, and it is natural that ferrite antennas built into radios and the like are also required to be smaller and thinner.

FIG. 1 shows a conventional small and thin ferrite antenna. It consists of a coil 2 wound around a flat ferrite core 1 and a lead 3 thereof.

However, as the conventional ferrite core 1 is made thinner, the warping and bending during firing become larger, and the reduction in mechanical strength is large, and the current limit is about 2fi thickness. If the thickness was less than that, the ferrite core 1 would easily break during use, making it difficult to put it into practical use. There is also the problem that the thinner material also deteriorates its multi-temperature characteristics.

Purpose of the Invention In view of the above drawbacks, the present invention provides an ultra-thin ferrite antenna that improves the mechanical strength (flexural strength, anti-impact strength) of a ferrite core and also improves temperature characteristics. .

Structure of the Invention In order to achieve this object, the ferrite antenna of the present invention includes a ferrite core made by laminating a plurality of cut and polished ferrite plates with a thickness of about 0.2 m to 1.01111 I with an adhesive, etc.; Or between the above ferrite plates 7
A coil is wound around a ferrite core that is bonded with an adhesive into which a magnetic material such as 1,000-yrite powder or amorphous foil is inserted.This configuration improves the mechanical strength of the ferrite core. .

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the drawings. Fig. 2 shows a light antenna coil according to the first embodiment of the present invention, and 11 is a block-shaped core whose thickness is several times to several tens of times the required thickness, which is sliced to the required thickness and polished. A ferrite core is made by bonding two ferrite plates 11a together, 12 is a coil wound thereon, and 13 is a lead wire of the coil 12. FIG. 3 shows an enlarged cross-sectional view of the ferrite core 11.
4 is used. Materials for the adhesive 14 include epoxy, vinyl butyral, and chloroprene rubber, and desired electrical properties and mechanical strength can be obtained by selecting the material and the thickness of the adhesive layer. .

Note that the thickness of the adhesive layer needs to be sufficiently smaller than the overall thickness (about 1/10). Further, the inductance temperature characteristic of nickel-based ferrite, which is normally used in ferrite antennas, has a positive temperature coefficient, and as the temperature rises, the inductance increases. Therefore, by using a material with a large positive coefficient of thermal expansion (such as vinyl butyral) for the adhesive 14, the thickness of the adhesive layer (that is, the gap between the ferrite plates 11a) changes, and the ferrite core 11
The temperature characteristics are improved because it acts in the direction of canceling out the temperature characteristics.

Next, a second embodiment will be explained with reference to an enlarged sectional view of the core in FIG. 4. Two ferrite plates 11a are bonded together with an adhesive 14' to constitute a ferrite core 11, and an appropriate amount of ferrite powder 16 is mixed into the adhesive 14'. As the thickness of the adhesive layer becomes thicker, the effective magnetic permeability μe of the ferrite core 11 becomes smaller, so it is necessary to slightly increase the width or length of the ferrite core in order to obtain the same gain compared to the conventional one. there were. Therefore, the above-mentioned drawbacks are compensated for by mixing ferrite powder 15 into the adhesive 14, and a different magnetic material 16 is inserted as a replacement for the ferrite powder, for example, a ferrite material with a higher μe than the upper and lower ferrite plates 11a. It is also possible to improve the gain of the siferite antenna by inserting an amorphous thin plate 16.

Although the above three embodiments all use two ferrite plates 11a, it goes without saying that a larger number can be used.

Effects of the Invention As described above, the ferrite antenna of the present invention can improve mechanical strength and temperature characteristics using the same ferrite material and thickness as conventional ones.In other words, an ultra-thin ferrite antenna with good temperature characteristics can be provided. , is of great industrial value.

[Brief explanation of drawings]

FIG. 1 is a perspective view of a conventional small and thin ferrite antenna, and FIG. 2 is a partially enlarged sectional view of a ferrite material according to an embodiment of the present invention. 11... Ferrite core, 11a...
Ferrite plate, 12... Coil, 13...
...Lead wire, 14...Adhesive, 14'...
... Adhesive, 16 ... Ferrite powder, 16
...Magnetic material. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 Figure 4

Claims (1)

[Claims] A ferrite antenna is made by winding a coil around a ferrite core in which adhesive or an adhesive and a magnetic material different from the ferrite plates are inserted between multiple ferrite plates.