JP3846798B2 - Coil device manufacturing method - Google Patents

Description

  The present invention relates to a core and a coil device using the core. The coil device according to the present invention includes an antenna applicable to a vehicle-mounted transponder or the like, or an inductor or choke coil for communication equipment.

  Various types of coil devices have been proposed and put into practical use. As one of them, recently, a coil device applicable as a vehicle-mounted antenna or a transponder has been proposed. In a coil device applied to such a use, a core having a good high frequency characteristic is generally used. And while winding the coil of required number of turns around this core, connecting the coil terminal to the metal terminal electrode provided at both ends in the longitudinal direction of the core, and covering the whole with a thermosetting resin such as epoxy resin Take.

  By the way, not only in the case of a vehicle-mounted coil device, but in a coil device used as an inductor for communication equipment or a choke coil, the electrical characteristics greatly depend on the core size. In general, the larger the core size, the better the electrical characteristics.

  However, since the outer dimensions of the coil device are limited depending on the application, if the core size is increased in the limited outer dimensions, the thickness of the insulating covering formed of a thermosetting resin such as an epoxy resin is increased. However, it becomes relatively thin, and the whole or a part of the core and the coil are exposed to the outside, and it is impossible to guarantee the impact resistance, vibration resistance, durability, etc., which are the purposes of the insulation coating. On the other hand, if the thickness of the insulating covering is increased to ensure impact resistance, vibration resistance, durability, etc., the core size is reduced and the electrical characteristics are sacrificed. That is, in this type of coil device, how to increase the core size and ensure high electrical characteristics without impairing the impact resistance, vibration resistance and durability of the insulation coating is an important issue. become.

  Furthermore, in consideration of the influence of the insulating coating on the core, a structure that does not deteriorate the core characteristics must be adopted.

  From this point of view, when examining the publicly known technology, for example, in Patent Document 1, a synthetic resin base by injection molding is attached to the flanges provided at both ends in the longitudinal direction of the core, and the outer periphery of the synthetic resin base is mounted. Discloses a structure in which a metal electrode terminal is mounted by its own spring action. However, this prior art does not disclose means for solving the above-described problems.

Next, Patent Document 2 discloses a structure that covers the entire surface with an exterior material such as a resin. However, there is no mention of a resin material that constitutes the exterior material, and the means for solving the above-described problems is also disclosed. Is not disclosed.
JP 2001-339224 A JP-A-7-130556

  An object of the present invention is to provide a coil device in which the core size is increased and the electrical characteristics are improved without impairing the impact resistance, vibration resistance and durability of the insulating coating.

  Another object of the present invention is to provide a coil device in which the amount of change in inductance value due to temperature fluctuation is reduced.

  In order to solve the above-described problems, the present invention provides a lower mold and an upper mold that include a cavity that accommodates a core around which a coil is wound and that have a plurality of protrusions that project toward the core when accommodated. The core around which the coil is wound is accommodated in the cavity, molten resin is injected between the lower mold and the upper mold, and the core and the coil, and is insulated around the core and the coil. A method of manufacturing a coil device that forms a covering, wherein the core and the coil are positioned in the cavity by the plurality of protrusions.

  As described above, the coil device according to the present invention includes an insulating cover, and the insulating cover covers the core and the coil. According to this structure, the core and the coil are protected by the insulating cover, and a coil device having excellent reliability can be realized.

  In the present invention, one of the important points is that the core and the coil are positioned substantially at the center of the insulating covering. According to such a structure, a highly reliable coil device that is sealed inside the core and coil insulation covering body, prevents the entire exposure of the core and the coil, and is excellent in impact resistance and vibration resistance. Can be realized. In addition, since the thickness of the insulation coating can be set to the minimum required value, the outer dimensions of the inner core and the coil are set relatively large with respect to the determined outer dimensions of the coil device, and excellent electrical Characteristics can be obtained.

  In the present invention, another important point is that the insulating covering is made of a thermoplastic insulating resin. When the insulating cover is made of a thermoplastic insulating resin material, the amount of change in inductance value due to temperature fluctuation can be reduced as compared with a case where the insulating cover is made of a thermosetting insulating resin material. This is because if the insulating cover is made of a thermoplastic insulating resin material, the thermal expansion and contraction of the insulating cover on the core is less affected than the case where the insulating cover is made of a thermosetting resin material. This is presumably because the magnetic properties inherent to the core can be exhibited. The insulating covering is preferably composed of a liquid crystal polymer.

  Specific examples of application of the coil device of the present invention are antennas, particularly in-vehicle antennas, transponders, inductors for electronic devices, and the like.

As described above, according to the present invention, the following effects can be obtained.
(A) It is possible to provide a coil device in which the core size is increased and the electrical characteristics are improved without impairing the impact resistance, vibration resistance, and durability due to the insulating coating.
(B) It is possible to provide a coil device in which the amount of change in inductance value due to temperature fluctuation is reduced.

FIG. 1 is a cross-sectional view of a coil device according to the present invention, and FIG. 2 is a perspective view showing a state before a terminal is bent in the coil device shown in FIG. The coil device of the illustrated embodiment can also be used for an antenna, an in-vehicle antenna, a transponder, an inductor of an electronic device, and the like. The illustrated coil device includes a core 1, a coil 4, two terminals 51 and 52, and an insulating cover 7.
The core 1 includes a coil winding part 11 and two collar parts 21 and 22. The core 1 in the illustrated embodiment is made of ferrite and can be obtained by sintering a ferrite powder, machining a ferrite rod, or a combination of both.

  The coil winding part 11 extends in the longitudinal direction X. In the illustrated embodiment, the coil winding portion 11 has a square cross section. In addition, any cross-sectional shape such as another polygonal cross-section, a circular cross-section, or an elliptical cross-section can be adopted. The coil winding part 11 has an elongated shape extending long in the longitudinal direction X.

  Each of the flange portions 21 and 22 is provided at the both ends of the coil winding portion 11 in the longitudinal direction X and is provided with the coil winding portion 11, and has grooves 31 and 32 on the outer end surface in the longitudinal direction X. . As for the collar parts 21 and 22, the cross section in the position where the grooves 31 and 32 do not exist is a square cross section. It is preferable that the outer edge portions and the inner corner portions of the collar portions 21 and 22 are rounded or slightly chamfered.

  Each of the grooves 31 and 32 has a depth direction that coincides with the longitudinal direction X, has a groove width in the thickness direction Z, extends in the width direction Y, and the groove width Z3 narrows toward the bottom. . According to this structure, it is possible to obtain a highly reliable core and coil device having excellent impact resistance and vibration resistance by selecting the depths of the grooves 31 and 32 with respect to the dimension in the longitudinal direction X of the collar portions 21 and 22. it can.

  In the drawing, the grooves 31 and 32 are substantially completely V-shaped, with both inclined surfaces intersecting at the bottom and the depth direction coinciding with the longitudinal direction X. In addition, the bottom may be a flat surface or a circular surface. Further, in the drawing, it is formed over the entire width of the collar portions 21 and 22, but it may be a structure that is shorter than the entire width and closed at both ends.

  The core 1 is combined with a coil 4 and terminals 51 and 52. The coil 4 is wound around the coil winding portion 11 of the core 1. The number of turns, the wire diameter, etc. of the coil 4 vary depending on the coil device to be obtained.

  Each of the terminals 51 and 52 is made of a metal plate material, has two bent portions bent inward, one end is inserted into and fixed to the grooves 31 and 32 of the core 1, and the terminal 41 of the coil 4. , 42 are connected. As the metal plate material constituting the terminals 51 and 52, a non-magnetic and springy material such as a phosphor bronze plate or a stainless steel plate such as SUS 304-CSP can be used.

  One end of each of the terminals 51 and 52 is inserted into the grooves 31 and 32 of the core 1. As described above, since the groove widths of the grooves 31 and 32 become narrower toward the bottom, the terminals 51 and 52 are positioned inside the grooves 31 and 32 at fixed positions determined by the plate thickness. . For this reason, the positions of the terminals 51 and 52 with respect to the core 1 are uniquely determined, and the fluctuation of the frequency-inductance characteristic and the fluctuation of the frequency-Q characteristic due to the positional fluctuation of the terminals 51 and 52 do not occur.

  Each of the grooves 31 and 32 of the collar portions 21 and 22 has both inclined surfaces intersecting at the bottom, the depth direction coincides with the longitudinal direction X, has a groove width in the thickness direction Z, and extends in the width direction Y. Yes. Therefore, each of the terminals 51 and 52 is fixed to the grooves 31 and 32 so that the plate surfaces are parallel to each other when viewed in the thickness direction Z with respect to the flange portions 21 and 22 of the core 1.

  The terminals 51 and 52 are fixed inside the grooves 31 and 32 by adhesives 61 and 62 filled in the grooves 31 and 32. In the illustrated embodiment, the terminals 51 and 52 have notches at one end inserted into the grooves 31 and 32. With such a structure, since the adhesives 61 and 62 are filled in the notches, the attachment strength of the terminals 51 and 52 to the core 1 is improved.

  The insulating cover 7 covers the core 1, the coil 4, and part of the terminals 51 and 52. According to this structure, the insulating cover 7 protects the core 1 and the coil 4, improves the coupling strength of the terminals 51 and 52 to the core 1, and realizes a coil device having excellent mechanical reliability.

  The core 1 and the coil 4 are positioned substantially at the center of the insulating cover 7. That is, in FIG. 1, the thicknesses t <b> 1 and t <b> 2 of the insulating cover 7 that covers the upper surface and the lower surface of the core 1 are substantially equal. Although not shown, the thickness of the insulating cover 7 is substantially equal to the thicknesses t1 and t2 of the coating on the upper surface and the lower surface on both side surfaces connected to the upper surface and the lower surface as viewed in a cross section perpendicular to the upper surface and the lower surface. . According to such a structure, the core 1 and the coil 4 are encapsulated inside the insulating covering 7 to prevent the core 1 and the coil 4 from being exposed completely or partially, and is excellent in shock resistance and vibration resistance. A reliable coil device can be realized.

  In addition, since the core 1 and the coil 4 are positioned substantially at the center of the insulating cover 7, the thicknesses t1 and t2 of the insulating cover 7 can be set to the minimum required values. For this reason, the external dimensions of the inner core 1 and the coil 4 can be set relatively large with respect to the determined external dimensions of the coil device, and excellent electrical characteristics can be obtained.

  FIG. 3 is a diagram showing a molding process suitable for positioning the core 1 and the coil 4 at substantially the center of the insulating covering 7. In the example of FIG. 3, protrusions A1 and B1 having substantially the same height are provided in the cavities of the lower mold A and the upper mold B, and the core 1 and the coil 4 are connected to the lower mold A and the upper mold B by the protrusions A1 and B1. Is accurately positioned at a predetermined position inside the. The tips of the protrusions A1 and B1 are preferably slightly separated from the surface of the core 1. As a result, the core 1 and the coil 4 are positioned substantially at the center of the insulating coating and are completely covered by the insulating coating 7 without being exposed to the outside from the insulating coating 7.

  Further, according to the molding process, the gaps G1 and G2 between the lower mold A and the upper mold B and the core 1 and the coil 4 are kept constant by regulating the positions of the core 1 and the coil 4 by the protrusions A1 and B1. Therefore, the thicknesses t1 and t2 (see FIG. 1) of the insulating covering 7 can be set to the necessary minimum values. For this reason, the external dimensions of the inner core 1 and the coil 4 can be set relatively large with respect to the determined external dimensions of the coil device, and excellent electrical characteristics can be obtained.

  The insulating cover 7 is made of a thermoplastic insulating resin. When the insulating cover 7 is made of a thermoplastic insulating resin, the effects of thermal expansion and contraction of the insulating cover on the core 1 are reduced as compared with a case where the insulating cover 7 is made of a thermosetting insulating resin. For this reason, the thermal stress in the core 1 is reduced, and the amount of change in inductance value due to temperature fluctuation can be reduced.

  FIG. 4 is a diagram showing temperature-L change rate characteristic data. In the figure, the horizontal axis represents temperature (° C.), and the vertical axis represents L change rate (%), which is the change rate of inductance. Curve Cr is a characteristic when the insulation coating body 7 is not provided, curve C1 is a characteristic of the coil device according to the present invention using a thermoplastic resin (liquid crystal polymer) as the insulation coating body 7, and curve C2 is an insulation coating body 7 shows the characteristics of a coil device using a thermosetting resin (diallyl resin). The characteristic curves Cr, C1, and C2 are all obtained by the coil device having the structure shown in FIGS. 1 and 2 except for the point of the insulating cover 7.

  Referring to FIG. 4, when a thermosetting resin is used as the insulating coating 7, the temperature-L change rate characteristic is greatly deviated from the reference characteristic curve Cr as shown as a characteristic curve C 2. On the other hand, the coil device according to the present invention exhibits a temperature-L change rate characteristic very close to the reference characteristic curve Cr. This is because when the insulating covering 7 is made of a thermoplastic insulating resin, the effect of thermal expansion and contraction on the core 1 becomes smaller than when the insulating covering 7 is made of a thermosetting resin (characteristic curve C2). This is presumably because the stress is reduced and the magnetic characteristics (characteristic curve Cr) inherent to the core 1 can be exhibited.

It is sectional drawing of the coil apparatus which concerns on this invention. In the coil apparatus shown in FIG. 1, it is a perspective view which shows the state before bending a terminal. It is a figure which shows the mold process of the insulation coating body which consists of thermoplastic resins. It is a figure which shows temperature-L change rate characteristic data.

Explanation of symbols

1 Core 11 Coil winding part 4 Coil 7 Insulation coating

Claims (4)

A lower mold and an upper mold having a cavity for housing a core wound with a coil and having a plurality of protrusions projecting toward the core at the time of housing are prepared in the cavity,
The core around which the coil is wound is accommodated in the cavity,
Injecting a molten resin between the lower mold and the upper mold and the core and the coil to form an insulating coating around the core and the coil.
A method of manufacturing a coil device,
The method of manufacturing a coil device, wherein the core and the coil are positioned in the cavity by the plurality of protrusions. The core has a coil winding part and a pair of collar parts provided at both ends in the longitudinal direction,
The method of manufacturing a coil device according to claim 1, wherein the plurality of protrusions are formed at positions that sandwich the pair of flange portions from above and below.   3. The method of manufacturing a coil device according to claim 1, wherein the plurality of protrusions are set to a height at which the core can take a position that does not contact all the protrusions.   The method for manufacturing a coil device according to any one of claims 1 to 3, wherein the plurality of protrusions are set at the same height.

Images