JP2001339224A - Very small antenna coil - Google Patents

Abstract

PROBLEM TO BE SOLVED: To contribute to an increase in the transmission distance of a transponder, etc. SOLUTION: This antenna coil is equipped with a ferrite core 1, a coil 2 wound around the ferrite core 1, and a metal electrode terminal 4 made of a nonmagnetic body connected to the leader and end of the coil 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a small antenna coil applicable to a transponder or the like embedded in an engine key used in, for example, an anti-theft system for automobiles called an immobilizer system.

[0002]

2. Description of the Related Art In an immobilizer system, a transponder is embedded in an engine key, an ID signal is transmitted from the transponder, and if the ID signal does not match an ID signal stored in advance in an electronic control unit of a vehicle body, the engine is started. Can not do it.

[0003] The antenna coil used in the transponder is naturally small since the transponder itself is embedded in the engine key. At the same time, transponders are required to have a long transmission signal transmission distance, and there is an increasing demand for improved performance of minute antenna coils.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned demands for a small antenna coil.
An object of the present invention is to provide a small antenna coil which can contribute to extending a transmission distance of a transponder or the like.

[0005]

A minute antenna coil according to the present invention comprises a ferrite core, a coil wound around the ferrite core, and a non-magnetic metal electrode terminal connected to the start and end of the coil. And characterized in that: As a result, the resonance Q can be increased, which contributes to the extension of the transmission distance.

A minute antenna coil according to the present invention is provided with a ferrite core, a coil wound around the ferrite core, and electrode terminals connected to the start and end of the coil. And a base made of a molding material. by this,
The antenna sensitivity can be improved, and the transmission distance can be extended.

In a minute antenna coil according to the present invention, a core having a rod-shaped winding portion and two flange portions provided at both ends of the winding portion, a coil wound around the core,
A non-magnetic metal electrode terminal connected to the start and end of the coil. This allows
Better antenna sensitivity can be obtained than when no flange is provided.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A small antenna coil according to the present invention will be described below with reference to the accompanying drawings. FIG. 1 shows an embodiment of a small antenna coil according to the first embodiment of the present invention. This small antenna coil has a coil 2 wound around a ferrite core 1 and a ferrite core 1
Are held on bases 3, 3 obtained by injection molding.

FIG. 2 shows the details of the base 3. The base 3 has a substantially cubic shape, and a concave portion 31 that receives the end of the ferrite core 1 is formed in a portion facing the end of the core 1. A groove 32 is formed in the base 3 at a position facing the end from the recess 31 in the same direction as the winding direction of the coil 2. A hole 33 is formed from the upper surface side of the base 3.

A substantially U-shaped electrode terminal 4 is fitted in the groove 32 of the base 3 and is bent downward and fixed in the hole 33. The start (end) 21 of the coil 2 is
It is pulled out and connected to the electrode terminal 4 by soldering or the like.

In the micro antenna coil having the above structure, when the electrode terminal 4 is made of copper or a non-magnetic stainless steel (for example, SUS 304-CSP), and without using the electrode terminal 4 Q with respect to frequency when measurement is performed at the beginning (end) 21 of coil 2
The value of (sharpness of resonance) is shown in FIG.

As is apparent from FIG. 3, Q can be increased by using a non-magnetic stainless steel metal, and the transmission distance can be extended by improving the resonance performance.

The base 3 is obtained by injection molding.
Ferrite particles, which are magnetic substances, are mixed in the plastic of the molding material as an additive at about 85%. FIG. 4 shows the antenna sensitivity of the base 3 and a base formed without mixing ferrite particles as an additive, and FIG. 5 shows a measurement circuit.

FIG. 4 shows that the sensitivity of the base 3 in which ferrite particles are mixed as an additive is good. That is, by providing the base 3 made of a molding material containing magnetic particles as an additive, it is possible to improve the antenna sensitivity and to contribute to the extension of the transmission distance.

This small antenna coil is, for example,
16mm long, 3mm deep, 2mm high
The size of the base 3 is about 3 mm × 3 mm × 2 mm. The width of the electrode terminal 4 is about 0.5 mm. Therefore, in the present invention, in a minute antenna coil, by devising the minute electrode terminal 4,
In addition, it is shown that adding a device to the minute base 3 can contribute to extending the transmission distance.

Next, a small antenna coil according to a second embodiment will be described. The small antenna coil according to the second embodiment uses the core 100 shown in FIG.
That is, the core 100 includes the rod-shaped winding portion 102 and the flange portions 101, 101 provided at both ends of the winding portion 102.

FIG. 7 shows the inner side 104 of the flange 101.
A U-shaped resin base 130 is fitted so as to receive the winding portion 102 as shown in FIG. That is, the core 100 is pushed down in the direction of the arrow X in FIG. 7 toward the resin base 130, so that the core 100 and the resin base 130 are joined.

A slightly cut groove 131 is formed in the U-shaped outer peripheral portion on the front side of the resin base 130 in FIG. 7, and both ends are bent inward.
The letter-shaped electrode terminals 140 are fitted as shown by the arrow Y in FIG. The start end (end) of the coil wound around the winding part 102 is pulled out and connected to the electrode terminal 140 by soldering or the like.

As described above, a small antenna coil constituted by using the core 100 having the flange portions 101, 101;
FIG. 8 shows a comparison of the sensitivity with a small antenna coil formed by using a core having no flange. As is clear from FIG.
It can be seen that the sensitivity of the small antenna coil formed by using the core 100 having the core is better than the sensitivity of the small antenna coil formed by using the core having no flange.

FIG. 8 shows the result of comparing the sensitivity by changing the thickness of the flange portion 101. It is considered that the thickness of the flange 101 does not greatly affect the sensitivity. The composition of the resin base 130 may be the same as the composition of the base 3 in the first embodiment.

[0021]

As described above, according to the present invention, a ferrite core, a coil wound around the ferrite core, and a non-magnetic metal electrode terminal connected to the start and end of the coil are formed. As a result, there is an effect that the Q of resonance can be increased and the transmission distance can be extended.

As described above, according to the present invention, a ferrite core, a coil wound around the ferrite core, and electrode terminals connected to the start and end of the coil are provided. Since a base made of a molding material as an agent is provided, antenna sensitivity can be improved, and there is an effect that the transmission distance can be extended.

As described above, according to the present invention, the core is composed of a rod-shaped winding portion and two ends provided at both ends of the winding portion.
Since two flanges are provided, better antenna sensitivity can be obtained than when no flange is provided, and there is an effect that the transmission distance can be extended.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view of a small antenna coil according to a first embodiment of the present invention.

FIG. 2 is an enlarged perspective view of a main part of the small antenna coil according to the first embodiment of the present invention.

FIG. 3 is a diagram showing a Q characteristic with respect to a frequency of the small antenna coil according to the first embodiment of the present invention.

FIG. 4 is a diagram showing sensitivity characteristics of the small antenna coil according to the first embodiment of the present invention.

FIG. 5 is a circuit diagram for measuring the characteristics of FIG. 4;

FIG. 6 is a perspective view of a core used for a small antenna coil according to a second embodiment of the present invention.

FIG. 7 is an enlarged perspective view of a main part of the small antenna coil according to the first embodiment of the present invention.

FIG. 8 is a diagram illustrating sensitivity characteristics of the small antenna coil according to the second embodiment of the present invention.

[Explanation of symbols]

1, Ferrite core 2 Coil 3, 130 Base 4, 140
Electrode terminal 21 Starting end (end) of coil 31 Depression 32, 131 Groove 33 Hole 100 Core

Claims (6)

[Claims] 1. A small antenna coil comprising: a ferrite core; a coil wound around the ferrite core; and a nonmagnetic metal electrode terminal connected to the start and end of the coil. 2. The small antenna coil according to claim 1, wherein the metal electrode terminal is made of a stainless metal. 3. A ferrite core, a coil wound around the ferrite core, and a base made of a molding material provided with electrode terminals connected to the start and end of the coil, the magnetic material being an additive. A minute antenna coil comprising: 4. The small antenna coil according to claim 3, wherein ferrite particles are used as an additive. 5. A core comprising a rod-shaped winding portion, two flanges provided at both ends of the winding portion, a coil wound around the core, and a start end and an end connected to the coil. And a non-magnetic metal electrode terminal. 6. A resin base provided inside the two flanges and receiving the winding portion, wherein the resin base is formed with a groove for providing the metal electrode terminal. 6. The small antenna coil according to 5.