KR101724622B1 - Low Frequency Antenna, Method for Making the Same and Keyless Entry System Using the Same - Google Patents

Abstract

The present invention relates to a low-frequency (LF) antenna, a method of manufacturing the same, and a key entry system using the same, wherein the antenna core is manufactured by a non-infiltrating process using a synthetic resin case, .
The LF antenna of the present invention is an LF antenna including a bar-shaped antenna core and a coil wound around the antenna core, the antenna core including a plurality of laminated ribbon sheets laminated to form an inductor core; And a flexible case made of a synthetic resin and accommodating and sealing the plurality of stacked ribbon sheets therein.

Description

TECHNICAL FIELD [0001] The present invention relates to a low-frequency antenna, a method of manufacturing the same, and a keyless entry system using the same.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low frequency (LF) antenna and a keyless entry system using the same, and more particularly, to an antenna core manufactured by a non-infiltrating process using a synthetic resin case, To a LF antenna, a manufacturing method thereof, and a keyless entry system using the LF antenna.

The antenna core or antenna is used as a transmitting antenna for generating a magnetic field. The antenna generally operates in a resonant circuit, which is tuned by adapting the series capacitance and / or series resistance at the desired transmit frequency to the impedance of the antenna layout.

In the simplest case, the transmitting antenna may be fabricated using a ferrite core as the magnetic core. Thanks to the high isotropic volume resistivity of this magnetic material, excellent quality and low hysteresis loss have already been achieved without any additional measurement.

However, the space for accommodating the antenna installed in the vehicle in order to construct the keyless entry system requires an antenna that can define the section of the antenna, or be bent or bent. An antenna made of a ferrite core is not suitable because of insufficient elasticity and low saturation induction.

Generally, a magnetic core formed by laminating a plurality of amorphous ribbon sheets has a structure in which the flexibility is poor because the core is impregnated with an epoxy resin adhesive. Also, since the impregnated antenna core is solidified by the impregnation process, there is a problem that the loss is large (Q value is decreased) and the process cost is increased according to the impregnation process.

Further, a laminate of a soft magnetic member made of a plurality of amorphous ribbon sheets is proposed in U.S. Patent No. 5,567,537 (Patent Document 1). U.S. Patent No. 5,567,537 uses amorphous and nanocrystalline alloys for the manufacture of thin film antennas and can maintain softness and other physical properties before and after bending stresses in chip cards. In particular, unlike a ferrite bar, this thin film antenna does not cause cracking due to bending stress.

Patent Document 1 discloses a flexible antenna core composed of a laminate composed of a plurality of layers of an amorphous alloy, and additionally, a bundle in which foil insulation is inserted between layers as needed is described. Furthermore, the possibility that the insulation of each amorphous magnetic member is caused by the oxide layer or another layer which can be generated by the chemical treatment of the magnetic member is also described.

In practice, the known internal structures of amorphous and nanocrystalline alloys and in particular of the antenna cores, in particular in the case of antennas which can bend significantly, especially for bulky and bulged windings, are suitable for very limited applications. In automobile access systems, ferrite cores which have been difficult to bend for a long time have been used.

In consideration of this point, U.S. Patent Application Publication No. 2006/0022886 (Patent Document 2) discloses an amorphous antenna having a low magnetostriction value so as to ensure deformation of an antenna without greatly changing the magnetic property of the antenna at the time of deformation Or a nanocrystalline alloy is rolled in a toroidal shape and then one side is cut into a bar shape and the soft magnetic member is electrically separated by an insulating foil and is wound on an antenna core taped with an adhesive tape An antenna structure in which a coil is wound is proposed.

Patent Document 2 discloses that a reinforcing sheet made of synthetic resin is provided on each of upper and lower sides in order to stabilize the laminate in which the soft magnetic member and the insulating foil are laminated.

Korean Patent Laid-Open Publication No. 10-2012-115341 (Patent Document 3) discloses a method of winding a continuous strip made of a soft magnetic alloy having an amorphous or nanocrystal structure in a toroidal manner, then flat- And winding the coil.

The above-mentioned Patent Document 3 has a problem that it is difficult to realize a thin-film core because the amorphous metal is generally a very light material even though the continuous strip is pressed flatly in the toroidal-like continuous strip.

: U.S. Patent No. 5,567,537 : United States Patent Application Publication No. 2006/0022886 : Korean Patent Publication No. 10-2012-115341

It is an object of the present invention to provide a method of manufacturing an antenna core by a non-impregnation process using a synthetic resin case, (LF: Low Frequency) antenna, a manufacturing method thereof, and a keyless entry system using the same.

Another object of the present invention is to provide an LF antenna capable of improving the Q (Quality) value and increasing the recognition distance due to a small core loss as an antenna core is manufactured by a non-infiltration process using a synthetic resin case, a method of manufacturing the antenna, and a keyless entry system using the LF antenna I have to.

It is still another object of the present invention to provide an LF antenna capable of reducing manufacturing process and manufacturing cost by eliminating the need for a separate bobbin necessary for coil winding by packaging a laminated amorphous ribbon sheet using a synthetic resin case which is an insulating material, And to provide a keyless entry system using the same.

In order to achieve the above object, an LF antenna according to the present invention is an LF antenna including a bar-shaped antenna core and a coil wound around the outer periphery of the antenna core, wherein the antenna core is stacked to form an inductor core A plurality of stacked ribbon sheets with a plurality of stacked ribbon sheets; And a flexible case made of a synthetic resin and accommodating and sealing the plurality of stacked ribbon sheets therein.

The plurality of laminated ribbon sheets may be formed of a soft magnetic alloy having an amorphous or nanocrystal structure and may be formed by processing ribbons or strips into a sheet having a predetermined length.

In addition, when the plurality of laminated ribbon sheets are made of a soft magnetic alloy having an amorphous structure, the laminated ribbon sheet is subjected to a non-magnetic or magnetic field heat treatment (vertical or horizontal in the range of Max 4,000 Gauss) for 30 minutes to 6 hours at a temperature range of 300 ° C to 600 ° C, Wherein the plurality of laminated ribbon sheets are made of a soft magnetic alloy having a nanocrystal structure and subjected to a heat treatment without any magnetic field or magnetic field in a temperature range of 300 ° C to 700 ° C for 30 minutes to 6 hours Horizontal) can be performed. By changing the slope of the B-H loop by the magnetic field heat treatment, the linearity of the inductance value according to the frequency change can be increased and a high Q value can be derived.

The plurality of laminated ribbon sheets may be divided into minute pieces to improve flexibility and Q (quality) value.

In this case, the plurality of laminated ribbon sheets are constituted by a plurality of unit laminated ribbons, and each of the plurality of unit laminated ribbons has a protective sheet attached to the upper and lower surfaces thereof, and a double-sided tape is inserted between the laminated ribbon sheets, And the ribbon sheet may be divided into minute pieces.

The case is made of a heat shrinkable tube, and preferably the heat shrinkable tube is made of a polyolefin resin.

Both ends of the heat-shrinkable tube are squeezed and sealed, and a central portion between both ends can be closely attached to the outer periphery of a plurality of laminated ribbon sheets.

In addition, the case may be formed of a rectangular box made of engineering plastic. In this case, the rectangular box may include a rectangular barrel in which the laminated ribbon sheet is accommodated; And a lid which is formed integrally with one side of the rectangular barrel so as to cover the rectangular barrel. The three sides of the lid can be joined by a rectangular cross-section by ultrasonic welding to achieve sealing.

A keyless entry system according to the present invention includes a transmitter; And a keyless entry system including a receiver, wherein the transmitter and / or receiver includes the antenna.

A method of manufacturing an LF antenna according to the present invention includes: preparing a continuous ribbon made of a soft magnetic alloy having an amorphous or nanocrystal structure; Stacking a plurality of ribbon sheets slit and cut into a desired width and length to obtain a laminated ribbon sheet; Heat-treating the laminated ribbon sheet; Sealing the laminated ribbon sheet subjected to the heat treatment in a synthetic resin case and sealing the antenna sheet to form an antenna core; And forming an LF antenna by winding a coil around an outer periphery of the antenna core.

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The step of housing the heat-treated laminated ribbon sheet in a synthetic resin case and then sealing the laminated ribbon sheet to form an antenna core includes: assembling the laminated ribbon sheet into a heat shrinkable tube; Fixing the tube to the laminated ribbon sheet block by applying heat to the heat-shrinkable tube to shrink the tube; And thermally compressing and sealing both ends of the heat-shrinkable tube.

Further, the step of housing the laminated ribbon sheet subjected to the heat treatment in the synthetic resin case and then sealing the laminated ribbon sheet to form the antenna core may be performed by injection molding using an engineering plastic so that one side of the lid is integrally connected to one side of the rectangular tube, Manufacturing a box; And a step of receiving the laminated ribbon sheet in the rectangular box and bonding the three sides of the lid overlapping the rectangular shape by ultrasonic welding and sealing.

The method of manufacturing an LF antenna according to the present invention may further include a step of heat treating the laminated ribbon sheet and then separating the ribbon sheet into fine pieces by flake treatment.

The step of heat-treating the plurality of laminated ribbon sheets may include stacking the plurality of laminated ribbon sheets between a pair of fixing jigs and laminating them in a sandwich manner, and fastening a bolt-nut fixing device to both ends of the pair of fixing jigs .

As described above, according to the present invention, since the antenna core is manufactured by the non-impregnation process using the synthetic resin case, the structure is simple and the manufacturing process can be simplified with flexibility.

In addition, according to the present invention, as the antenna core is manufactured by the non-impregnation process using the synthetic resin case, the core loss is small and the Q value can be improved and the recognition distance can be increased.

Further, according to the present invention, since a laminated amorphous ribbon sheet is packaged using a synthetic resin case which is an insulating material, a separate bobbin necessary for winding the coil is not needed, which can reduce manufacturing process and manufacturing cost.

1 is a perspective view showing an LF antenna according to an embodiment of the present invention,
FIG. 2A is a sectional view taken along the line X-X 'in FIG. 1,
2B is a cross-sectional view of an LF antenna having a modified appearance according to an embodiment of the present invention,
3 is a flowchart showing a method of manufacturing an LF antenna according to the present invention,
4A to 4D are diagrams illustrating a method of manufacturing an antenna core for an LF antenna according to a first embodiment of the present invention,
5A and 5B are schematic sectional views of a case and an assembled state of the antenna core for an LF antenna according to a second embodiment of the present invention,
6 is a perspective view showing a state in which the LF antenna of the present invention is mounted on a door handle of a vehicle,
7 is a perspective view showing a state where the LF antenna of the present invention is molded and then mounted on an indoor bumper.

The following detailed description is merely an example, and is merely an example of the present invention. Further, the principles and concepts of the present invention are provided for the purpose of being most useful and readily explaining.

Accordingly, it is not intended to provide a more detailed structure than is necessary for a basic understanding of the present invention, but it should be understood by those skilled in the art that various forms that can be practiced in the present invention are illustrated in the drawings.

Hereinafter, an LF antenna according to an embodiment of the present invention will be described.

FIG. 2 is a cross-sectional view taken along the line X-X 'of FIG. 1, and FIG. 2B is a cross-sectional view of the LF antenna according to an embodiment of the present invention. Sectional view of the LF antenna.

1, an LF antenna 1 according to an embodiment of the present invention includes an antenna core 10 in the form of a bar and a coil 20 wound around the outer periphery of the antenna core 10 have.

The antenna core 10 includes a case 11 made of a synthetic resin and a plurality of laminated ribbon sheets 13 laminated to form a bar-shaped inductor core in the case 11.

The case 11 may be manufactured using a heat shrinkable tube 11c having a rectangular, elliptical or circular cross section, as shown in FIG. 4C. The heat-shrinkable tube 11c can be made of, for example, polyolefin resin and has a shrinkage ratio of generally 2: 1, and the use temperature is in the range of -55 to 125 ° C.

However, the heat-shrinkable tube 11c may be formed of another tube that is shrinkable by heat treatment in addition to polyolefin.

The case 11 is formed by inserting a plurality of laminated ribbon sheets 13 stacked in the heat shrinkable tube 11c and then heating the heat shrinkable tube 11c in accordance with the heat treatment of the heat shrinkable tube 11c and the structure shown in FIG. Lt; / RTI > That is, a plurality of laminated ribbon sheets 13 are inserted into the heat-shrinkable tube 11c to heat-treat the tubes 11c to shrink the tubes 11c to adhere to a plurality of laminated ribbon sheet 13 blocks, Is pressed and pressed to one side to obtain a structure shown in FIG. 2A. When both sides are simultaneously pressed, molding is performed with the symmetrical structure shown in FIG. 2B.

The both ends 11a and 11b of the case 11 formed by pressing both ends of the heat shrinkable tube 11c are formed so that the width of the region where the coil 20 is wound is larger than the width of the region where the coil 20 is wound, It is also possible to form it to have a wide flange.

A plurality of laminated ribbon sheets 13 laminated to form an inductor core is made of a soft magnetic alloy having an amorphous or nanocrystal structure. The soft magnetic alloy is obtained by, for example, a rapid quenching method (RSP) To a thickness of 10 [mu] m to 30 [mu] m is processed into a sheet having a predetermined length.

The laminated ribbon sheet 13 can constitute a bulk inductor core by stacking, for example, 100 individual ribbon sheets having a length of 80 mm and a width of 10 to 12 mm.

The amorphous ribbon used for the laminated ribbon sheet 13 may be a thin ribbon made of a soft magnetic alloy having an amorphous or nanocrystal structure.

The amorphous soft magnetic alloy may be an Fe-based or a Co-based amorphous alloy, and it is preferable to use an Fe-based amorphous alloy in consideration of material cost. The Fe-based amorphous alloy may be, for example, a Fe-Si-B alloy or an Fe-Si-B-Co alloy, Si-B, and Co-Fe-Cr-Si-B alloys. The soft magnetic alloy having the nanocrystal structure may be, for example, Fe-Si-B-Cu-Nb alloy.

The coil 20 wound around the outer circumference of the antenna core 10 may be an enameled wire that is enameled to the outside of the copper wire, and may be twisted wire, electric wire, cable, or the like. A capacitor (not shown) is connected in parallel to the two output terminals 20a and 20b led out from the coil 20 so as to constitute a resonant circuit.

As described above, in the present invention, when a plurality of laminated ribbon sheets 13 are laminated, lamination is performed without inserting any insulating foil, forming an oxide film, or impregnating an adhesive resin between the ribbon sheets.

Therefore, even if deformation such as bending or twisting is applied, the antenna core 10 made up of a plurality of laminated ribbon sheets 13 with the heat-shrinkable tube 11c pressed on the outer periphery is not deformed easily It has flexibility that can be achieved.

Hereinafter, a method of manufacturing the LF antenna according to the present invention will be described with reference to FIGS. 3 and 4A to 4D. FIG.

First, an amorphous ribbon or strip made of a soft magnetic alloy having an amorphous or nanocrystal structure is continuously produced by a rapid quenching method (RSP) by melt spinning.

Thereafter, the amorphous ribbon is first slit to a desired width (S11) using a slitter (not shown) so as to facilitate the post-treatment after the heat treatment, and then, A plurality of ribbon sheets 13a to 13n having a predetermined length are successively fed to the tray 133 by cutting the amorphous ribbon 131 continuously fed to a predetermined length using a cutter 130 (S12). In this case, the stacked ribbon sheets 13 (13a to 13n) stacked on the respective trays 133 can be stacked by a preset number of sheets by counting by a counter (not shown).

The laminated ribbon sheet 13 laminated by a predetermined number of sheets is then inserted between a pair of fixing jigs 14a and 14b to be laminated in a sandwich manner and the bolts 14a and 14b are fastened to both ends of the pair of fixing jigs 14a and 14b, And the fastening device 14c made of a nut is fastened to fix the laminated ribbon sheet 13. The fixing of the laminated ribbon sheet 13 using the pair of fixing jigs 14a and 14b is for facilitating the handling of the laminated ribbon sheet 13 during the heat treatment and after the heat treatment.

The laminated ribbon sheet 13 assembled by using the pair of fixing jigs 14a and 14b is heat-treated in the heat treatment furnace (S13).

When the laminated ribbon sheet 13 is made of a soft magnetic alloy having an amorphous structure, it is preferable to adjust the soft magnetic properties such as the permeability, the slope of the BH loop (Loop), the Q value, For 30 minutes to 6 hours, and the magnetic field heat treatment is performed along the vertical or horizontal direction at a maximum range of 4,000 Gauss. In particular, when the magnetic field is heat-treated, the slope of the B-H loop is changed to increase the linearity of the inductance value according to the frequency change and to induce a high Q value.

In this case, the heat treatment atmosphere does not need to be performed in the atmosphere because the heat treatment is performed in a temperature range in which oxidation is not caused even if the Fe content is high, and the heat treatment may proceed in the atmosphere. Further, even if the heat treatment is performed in an oxidizing atmosphere or a nitrogen atmosphere, the magnetic permeability of the amorphous ribbon sheet is not substantially different under the same temperature condition.

When the temperature of the heat treatment is less than 300 ° C, it has a higher permeability than the desired permeability and requires a longer heat treatment time. When the temperature exceeds 600 ° C, the permeability is remarkably lowered due to the superheating treatment, . Generally, if the heat treatment temperature is low, the treatment time is long. On the contrary, if the heat treatment temperature is high, the treatment time is shortened.

When the soft magnetic alloy having a nanocrystal structure, for example, Fe-Si-B-Cu-Nb alloy is used, the laminated ribbon sheet 13 forms nanocrystals, (In the range of up to 4,000 Gauss, vertical or horizontal) for 30 minutes to 6 hours at a temperature range of from 700 to 700 占 폚. By applying the magnetic field heat treatment, the slope of the B-H loop is changed to increase the linearity of the inductance value according to the frequency change, and to derive a high Q value.

In this case, since the content of Fe is 70 at% or more in the heat treatment atmosphere, if the heat treatment is performed in the air, oxidation is performed, which is not preferable from the viewpoint of the visual point. However, even if the heat treatment is performed in the oxidizing atmosphere, the permeability of the sheet is not substantially different at the same temperature condition.

In this case, when the heat treatment temperature is less than 300 ° C., nanocrystals are not sufficiently generated, and a desired magnetic permeability is not obtained and the heat treatment time is long. In the case where the temperature exceeds 700 ° C., the permeability is remarkably lowered there is a problem. If the heat treatment temperature is low, the treatment time is long. On the other hand, if the heat treatment temperature is high, the treatment time is preferably shortened.

Thereafter, the laminated ribbon sheet 13 subjected to the heat treatment can be separated into fine pieces through a flake treatment process so as to increase the flexibility and further improve the quality value.

A plurality of unit laminated ribbon sheets are formed for flake treatment of the plurality of laminated ribbon sheets, and each unit laminated ribbon sheet has a protective sheet attached on the upper and lower surfaces thereof, and a double-sided tape is inserted between the laminated ribbon sheets And the ribbon sheet may have a structure divided into fine pieces.

In this case, since a plurality of laminated ribbon sheets 13 are difficult to be flaked at the same time, for example, a unit laminated ribbon sheet is formed by 2 to 3 sheets, a single-sided tape is attached as a protective sheet to both exposed sides, , A flake treatment is applied to the ribbon sheet as it passes through the flake treatment apparatus in the state where the double-sided tape is laminated, and a plurality of flake-treated unit laminated ribbon sheets are stacked to form the antenna core 10 .

Thereafter, as shown in Fig. 4C, the laminated ribbon sheet 13 subjected to the heat treatment and flaking is counted by a predetermined number of times so as to generate a magnetic field suitable for the antenna core 10 for the LF antenna, (S14). Heat is applied to the heat-shrinkable tube 11c to shrink the tube so that the tube is fixed to the laminated ribbon sheet 13 (S15).

Then, both ends 11a and 11b of the heat-shrinkable tube 11c are thermally compressed and sealed to obtain the antenna core 10 shown in Fig. 4D (S16). The obtained antenna core 10 undergoes a quality check to confirm whether it has inductance (L), resistance (R) and Q (quality) values set in advance as an inductor core.

Thereafter, an enamel wire is wound on the outer periphery of the obtained antenna core 10 to form a coil 20 (S17), and an LF antenna 1 is obtained.

In the above description of the first embodiment, the laminated ribbon sheet 13 is assembled in the heat-shrinkable tube 11c to form the case 11 by the heat treatment method. However, in the case of the second embodiment shown in FIG. The case 110 can be used to assemble.

In this case, the case 110 can be manufactured by injection molding using engineering plastics such as, for example, PA66, PP, PET, PC, PBT, LCP and the like, And is foldable.

In this embodiment, the lid 113 is integrally connected to one side of the rectangular barrel 111 for convenience of operation. However, since the lid 113 is separate from the rectangular barrel 111, .

The antenna core 10a according to the second embodiment is constructed such that the laminated ribbon sheet 13 is received in the rectangular barrel 111 and the three sides of the lid 113 overlapping the rectangular barrel 111 are joined by ultrasonic welding, As shown in FIG. The rectangular barrel 111 and the lid 113 may be manufactured to have a thickness of 0.4 to 0.6 mm, for example.

As described above, the antenna core 10, 10a according to the present invention has a sufficient flexibility as a whole because the laminated ribbon sheet 13 having flexibility in the flexible cases 11, 110 is packaged in a sealed state. As a result, it is possible to easily mount the LF antenna 1 even in a complicated structure inside the vehicle.

In addition, since the laminated ribbon sheet 13 is embedded in the flexible cases 11 and 110, the laminated ribbon sheet 13 itself does not require an integration process such as binder impregnation.

Further, in the present invention, since the case 11, 110 having excellent insulation is enclosed on the outside of the laminated ribbon sheet 13, there is no need to form a separate insulating bobbin, so that the manufacturing process can be shortened and the cost can be reduced.

A low frequency (LF) keyless entry system can be realized by using the LF antenna 1 according to the present invention.

As shown in FIGS. 6 and 7, the LF antenna 1 is mounted inside the handle 30 of the automobile door or installed in the bumper of the automobile interior, and is mounted on a smart key carried by the user. (KEY FOB).

A keyfob mounted on the smart key of the user is provided with a low frequency (LF) receiver including a LF antenna 1, a 3D active immobilizer and a microcontroller, A transceiver including an antenna 1, an immobilizer reader, a microcontroller, a door handle interface and an antenna diagnostic device.

For example, when low frequency (LF) communication in the 22 kHz band is performed, communication required for user recognition is performed between the key fob mounted on the smart key of the user and the control unit mounted on the vehicle, Or more can be easily achieved.

In the conventional keyless entry system for a vehicle, several short ferrite antennas are installed in an automobile in order to adequately cover the entire space area around the automobile. However, when the LF antenna 1 according to the present invention is used, It is possible to use a number of antennas.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, I will understand.

Therefore, the scope of the present invention should not be limited to the above-described embodiments, but should be determined by equivalents to the appended claims, as well as the appended claims.

1: LF antenna 10: Antenna core
11: Case 11a, 11b: Both ends
11c: heat-shrinkable tube 13: laminated ribbon sheet
14a, 14b: fixing jig 14c: fastening device
20: Coils 20a and 20b: Output terminal
130: Cutter 131: Amorphous ribbon
133: Tray

Claims (15)

1. A low-frequency (LF) antenna comprising a bar-shaped antenna core and a coil wound around the antenna core,
The antenna core
A plurality of laminated ribbon sheets laminated to form an inductor core in the form of a bar; And
And a flexible case made of a synthetic resin and accommodating and sealing the plurality of stacked ribbon sheets therein,
Wherein the flexible case has a flange whose both ends are wider than a width of a region in which the coil is wound and is press-molded and sealed so that a central portion between both ends is in close contact with the outer periphery of a plurality of laminated ribbon sheets,
Wherein the plurality of laminated ribbon sheets are divided into fine pieces. The method according to claim 1,
Wherein the plurality of laminated ribbon sheets is a soft magnetic alloy having an amorphous or nanocrystal structure. delete The method according to claim 1,
Wherein the plurality of laminated ribbon sheets are composed of a plurality of unit laminated ribbons,
Wherein each of the plurality of unit laminated ribbons has a protective sheet attached on an upper surface and a lower surface thereof, and a double-sided tape is inserted between the laminated ribbon sheets and laminated, and the ribbon sheet is divided into minute pieces. The method according to claim 1,
Wherein the case is made of a heat-shrinkable tube. 6. The method of claim 5,
Wherein the heat shrinkable tube is made of a polyolefin resin. delete delete delete delete transmitter; And
receiving set;
Characterized in that the transmitter and / or receiver has an antenna according to any one of claims 1, 2, 4 to 6 embedded therein. Entry system. Preparing a continuous ribbon made of a soft magnetic alloy having an amorphous or nanocrystal structure;
Stacking a plurality of ribbon sheets slit and cut into a desired width and length to obtain a laminated ribbon sheet;
Heat-treating the laminated ribbon sheet;
Separating the heat-treated laminated ribbon sheet into fine pieces by flake processing;
Forming a bar-shaped antenna core by sealing a laminated ribbon sheet subjected to flaking treatment after heat treatment in a synthetic resin case; And
And winding a coil around an outer periphery of the antenna core to form an LF antenna,
Wherein the synthetic resin case of the antenna core has a flange having a width larger than a width of a region where both ends of the coil are wound and a center portion between the both ends is press-molded so as to be in close contact with an outer periphery of the plurality of laminated ribbon sheets. 13. The method of claim 12,
Wherein the step of forming the antenna core by sealing the laminated ribbon sheet subjected to the flaking treatment after the heat treatment in the synthetic resin case,
Assembling the laminated ribbon sheet into a heat shrinkable tube;
Fixing the tube to the laminated ribbon sheet block by applying heat to the heat-shrinkable tube to shrink the tube; And
And thermally compressing both ends of the heat-shrinkable tube to seal the LF antenna. delete delete

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