JPH06168830A - Structure of coil - Google Patents

Abstract

PURPOSE:To suppress dispersion of product inductances by applying a heat- resisting adhesive on the double-projected end faces of an E-type core so as to reduce the number of manufacture steps for securing mechanical fixing after heating. CONSTITUTION:Firstly, a bobbin 6 is epicyclically fitted into the projection 3 of an E-type core 1 and thereafter a proper quantity of a heat-resisting adhesive 13 such as an acryl group adhesive is applied to a double projection end face of the E-type core 1. Thereafter, the central projection 4 of the other core 2 is inserted into the bobbin 6 so as to accord the centers of both cores 1, 2 and the end faces of the double projections 3, 4. Then, heating is performed for prescribed hours by cramping at a prescribed pressure. Thereby, the manday necessary for manufacture can be sharply reduced, and dispersion of product inductances and peeling-off of the core junction face can be reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coil, and more particularly to the structure of a coil or transformer suitable for surface mounting on a printed board.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 3, a small coil or transformer mounted on a printed board has been widely used. That is, a bobbin 6 having a conducting wire 5 wound around the central protrusions 3 and 4 of a pair of ferrite cores 1 and 2 having an E-shaped cross section is loosely fitted and protrudes from a base portion 7 of the bobbin 6.
The ends of the lead wires are connected to the terminals 8 and 8--.

In the conventional coil or transformer having such a structure, first, the bobbin 6 having the conductor wire 5 wound on the central protrusion 3 of the E-shaped core 1 is fitted and then the center of the other E-shaped core 2 is fitted. The protrusion 4 is inserted into the central hole of the bobbin 6, and thereafter, the outer circumferences of the E-shaped cores 1 and 2 paired with each other are wound with a tape 9 and then the protrusions on both sides of the E-shaped cores 1 and 2 are wound. Instant adhesives 10 and 11 which can be expected to be sucked in due to capillary action are injected between the contacting end faces to tightly fix the pair of cores, and further, to secure the cores 1 and 2 and the bobbin 6 to the flange of the bobbin 6. A very troublesome manufacturing method of injecting an adhesive 12 having a filling effect, such as an epoxy adhesive, into the gap between the E-shaped core 2 and the projecting portion has been used.

However, since it is difficult to control the winding degree of the tape 9 in the conventional coil having such a structure, a slight difference is maintained in the E-shaped core joint surface gap. Since it is fixed, there is not only a large variation in the inductance between products, but when it is mounted on a printed board, especially when it is subjected to a reflow process as a surface mounting strip, the E-shaped core 1, Since the bonding surfaces of the instant adhesives 10 and 11 that bond 2 are stripped and the close contact between the cores is broken, the inductance of the coil is significantly reduced compared to before mounting, and the electronic circuit does not exhibit desired characteristics. Had a serious flaw: loss of function.

Further, when the coil having such a structure is applied to the one for applying an alternating voltage such as a step-up transformer, there is a defect that chatter vibration occurs due to the breakage of the mechanical fixation between the cores and it is difficult to cope with it. It was one that had both.

[0006]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned defects of the conventional coil all at once, and can reduce the man-hours for manufacturing, and can improve the machine between cores and between the core and the bobbin even after heating. It is an object of the present invention to provide a coil having a structure capable of ensuring a fixed fixation and suppressing variation in inductance between products.

[0007]

SUMMARY OF THE INVENTION To achieve the above object, a coil according to the present invention is basically a coil of a type in which a bobbin inner wall around which a conductive wire is wound is loosely fitted in an E-shaped core central protrusion. The structure is such that the heat-resistant adhesive is applied to the end faces of the protrusions on both sides of the core.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will now be described in detail with reference to the embodiments shown in the drawings. 1 (a) to 1 (c) are a partially cutaway plan view, a front sectional view and a side sectional view, respectively, showing a basic embodiment of the present invention. In the figure, 1 and 2 are E-shaped ferrite cores forming a pair, and a bobbin 6 having a conducting wire 5 wound around the central projections 3 and 4 thereof is loosely fitted thereto and protrudes from a base portion 7 of the bobbin 6. The basic structure of connecting the ends of the conducting wire 5 to the terminals 8 and 8-- is exactly the same as the conventional coil.

The coil according to the present invention is different from the conventional coil in that both cores 1 and 2 are not wound and fastened by a tape, but instead, a bobbin 6 is loosely fitted on a protrusion 3 of the core 1 first. A proper amount of a heat-resistant adhesive 13 such as an acrylic adhesive is applied to the end faces of both sides of the E-shaped core 1 and then the central protrusion 4 of the other core 2 is inserted into the bobbin 6 and the central and bilateral protrusions of both cores are inserted. The manufacturing method is used in which the end faces are aligned, clamped at a predetermined pressure, and heated for a predetermined time.

By doing so, both E-shaped cores 1, 2
Are fixed to each other, and there is no problem even if this coil is placed on an appropriate circuit pattern on the printed circuit board and subjected to a reflow process and heating. At this time, an air layer is present between the abutting end faces of the central projections 3 and 4, and an adhesive layer is present between the end faces of both side projections of the core, which disturb magnetic lines of force penetrating the core. However, it is empirically known that such a core does not have a significant influence on the inductance of the coil because the end surface to be abutted is mirror-finished in the first place.

Since some play is provided between the core and the bobbin to facilitate the assembly, when the coil having the above structure is applied to an alternating voltage such as a step-up transformer. It is likely to cause chattering vibration. In order to prevent this, a heat-resistant adhesive 13 may be applied to an appropriate place between the core 2 and the flange of the bobbin 6. Or the above E
When inserting the bobbin 6 into the E-shaped core 1, the E-shaped core 1
Alternatively, an adhesive may be applied to the base of the central protrusion 3 so that the outside is adhered to the base 7 of the bobbin 6.

As is clear from the above description, since the coil according to the present invention can make the clamping pressure applied when bonding both cores constant, the variation in the inductance between the products is reduced and the surface mounting on the printed board is reduced. Since the mechanical fixation between cores is not broken by the heating of the coil, the inductance of the coil does not change after mounting, and when this structure is applied to a step-up transformer etc. There is no risk of this occurring. Moreover, it is obvious that the number of man-hours required for manufacturing is drastically reduced, and it can be understood that the cost can be significantly reduced. It should be noted that it may be effective to mix fine ferrite powder in the adhesive in order to reduce the influence of the adhesive layer interposed between the end faces on both sides of the E-shaped ferrite cores 1 and 2.

Further, the coil according to the present invention can be modified as shown in FIG. That is, the E-shaped core 1 and the flat plate core 14 may be combined as a core, and in such a case as well, the heat-resistant adhesive 1 is applied to both side projection end faces of the E-shaped core 1.
The upper flat plate core 14 subjected to No. 3 may be placed, aligned, clamped, and heated.

[0014]

Since the coil according to the present invention has the structure as described above, the cost is reduced and the inductance between the products is reduced as the man-hour required for the manufacturing is largely reduced in consideration of the manufacturing process. Not only can the manufacturing unit price be further reduced by improving the yield by reducing the variation, but the possibility of the peeling of the joint surface of the core after mounting on the printed board is almost eliminated, and the malfunction or loss of the electronic circuit due to the reduction in inductance. Since there is no fear of this, a remarkable effect can be obtained in improving the yield in manufacturing an electronic device using this coil. In addition, if the structure of the present invention is applied to a step-up transformer or the like, there is no room for chatter vibration due to the peeling of the core joint surface, which frequently occurs in the conventional case, so it is also necessary to take extra measures on the printed circuit board. It significantly contributes to the cost reduction of electronic circuits.

[0015]

[Brief description of drawings]

1A and 1B are views showing a basic embodiment of the present invention, in which FIG. 1A is a partially cutaway plan view thereof, and FIG.
(C) is a side sectional view.

FIG. 2 is a diagram showing a second embodiment of the present invention.

FIG. 3 is a diagram showing a structure of a conventional coil (a).
Is a partially cutaway plan view thereof, (b) is a front sectional view, and (c) is a side sectional view.

[0017]

[Explanation of symbols]

1, 2 and 14 --- E-shaped, 3,4 --- core central protrusion 5 ---- wire ring, 6 --- bobbin, 13 --- adhesive

Claims (2)

[Claims] 1. A coil of a type in which a bobbin wound with a conductive wire is loosely fitted to a central protrusion of a core having an E-shaped cross section, and at least the end face abutting portions of the E-shaped core both-side protrusions are heat-resistant bonded. A coil structure characterized by being treated with an agent. 2. The coil structure according to claim 1, wherein a heat-resistant adhesive is also filled in a gap between the bobbin flange and the core, which faces each other.