JP2000173850A - Manufacture of pencil coil - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable resin to be mixed well to flow into an elliptical cylinder by a method wherein a gate is provided in the side of a terminal support, and resin is injected in a certain direction so as to turn round at the terminal support. SOLUTION: Resin injected through a fan gate 45 or a ring gate provided in the side of a terminal support 42 flows lengthwise as it remains completely mixed without producing a joint in the terminal support 42. A gate can be automatically cut off in a case where a pin point gate is used, but in a case where the fan gate 45 is used, the fan gate 45 is not automatically cut off after the molding die is opened, so that a gate cutting mechanism is built in a molding die. A gate is cut off with a gate cutting mechanism before a molded body is taken out of the die. Moreover, if a gate cutting equipment is not built in a die, a joint between the fan gate 45 and the terminal support 42 is sharply lessened in cross sectional area, a cutout 45a is provided in the part, the part is made weakest in mechanical strength, and the gate 45 may be automatically cut off when the die is opened. By this setup, a weld is prevented from occurring.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a small pencil-shaped coil (pencil coil) which is a kind of ignition coil for automobiles.
The present invention relates to a manufacturing method and a mold structure for molding a secondary bobbin capable of preventing the occurrence of a weld defect, which is a molding defect, in a thin and long cylindrical secondary bobbin which is a molded article of a thermoplastic resin used in the present invention.

[0002]

2. Description of the Related Art Conventionally, a secondary bobbin used for a pencil coil, which is a kind of ignition coil for an automobile required to be miniaturized, has a multilayer structure including a coil hardened with a thermosetting resin for insulation at a high temperature near an engine. Since they are used in combination, high heat resistance and a small coefficient of linear expansion are required. In order to satisfy the required specifications, for example, Japanese Patent Application Laid-Open No. 9-167709
As disclosed in Japanese Patent Application Laid-Open Publication No. H10-209, a resin molded from a highly heat-resistant thermoplastic resin (modified PPO: polyphenylene oxide or the like) filled with a large amount of glass fiber and inorganic powder is used.

[0003]

The secondary bobbin having a thin and long cylindrical shape in the prior art is made by injection molding. However, since the gate structure serving as a resin injection port emphasizes productivity, a multi-point pin is required. Point gates are used. However, the resin injected from this multi-point gate,
Since the resin flows in the longitudinal direction without intersecting with each other, the boundary between the resins does not weld, so that there is a problem that a so-called weld is easily generated. Since the weld of the secondary bobbin occurs linearly in the longitudinal direction, there is a problem that the strength of the secondary bobbin in the circumferential direction is reduced, and the electrical insulation performance is reduced.

SUMMARY OF THE INVENTION An object of the present invention is to provide a thin and long cylindrical secondary bobbin which is a molded article of a thermoplastic resin used for a pencil coil which is a kind of automobile ignition coil. An object of the present invention is to provide a molding die for a secondary bobbin and a method for producing the secondary bobbin in which the occurrence of a weld which is a molding defect is prevented without lowering of the molding.

[0005]

In order to achieve the above object, first, the cause of the weld of the secondary bobbin is that the resin injected from the gates at multiple points flows in the longitudinal direction without intersecting with each other. It was thought that the boundary did not weld and was merely in contact. Therefore, first, a gate structure was devised in which a multi-point gate was set to one point and the opportunity for the resin to contact each other was eliminated.

More specifically, a method is adopted in which the resin flows in the longitudinal direction without any seams by employing a fan gate or a ring gate into which the resin flows from the center of the cylinder in all directions. In this case, the gate cannot be automatically cut at the time of mold release like the current pinpoint gate, so a gate cutting mechanism is built in the mold,
The gate was cut before removing the molded product from the mold. When a multipoint gate similar to the current gate scheme is used, the structure and location of the gate should be such that the resin injected from the gate can interlock at the terminal support before flowing into the long cylinder. I decided.

That is, a gate is provided on the side surface of the terminal support, not on the end face of the conventional terminal support, and the resin is injected from a direction that causes the resin to make a swirling motion at the terminal support, so that the resin can be connected to each other. Are mixed well, and then flow into the long cylindrical portion. In addition, a method of applying ultrasonic vibration to the cavity of the molding die was also used in order to promote intermingling of the resins.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings.

FIGS. 1A and 1B are sectional views of a pencil coil 1 according to the present invention. The components of the pencil coil 1 are centered on the center core 2, around which are a soft epoxy 3, a secondary bobbin 4, a secondary coil 5, a hard epoxy 6, a primary bobbin 7, a primary coil 8, a hard epoxy 6, and a coil case. 9, each of which is sequentially and concentrically stacked and arranged. The function of the pencil coil is to increase the voltage supplied from a storage battery (not shown) and supply the boosted voltage to a spark plug (not shown). Here, the thermoplastic resin used for the secondary bobbin 4 has the required functional specifications of high heat resistance and a small linear expansion coefficient, and the moldability capable of forming the thin and long cylindrical secondary bobbin 4 without excess or shortage. What is necessary is just to be satisfactory, for example, Japanese Patent Application Laid-Open No. 9-167709
In the publication, a modified PPO resin (polyphenylene oxide) filled with a large amount of glass fiber and inorganic powder is used.

FIGS. 2A and 2B are sectional views of a secondary bobbin 4 in a conventional example. The shape of the secondary bobbin 4 is a thin long cylinder having a thickness of about 1 mm, a diameter of about 16 mm, and a length of about 100 mm. Further, the secondary coil 5 having a wire diameter of about 40 mm is divided and wound so as to have a flange 41. Here, 4 on the end face of the terminal support portion 42
Reference numeral 3 denotes a gate serving as a resin injection port. In this case, the gate is a three-point pinpoint gate. The resin injected from here flows in the longitudinal direction without intermingling in the terminal support portion 42. That is, a place where the resin merges between the three gates becomes a weld 44, and the weld 44 is formed as a straight line in the longitudinal direction.

FIG. 3 is a sectional view of a molding die 10 for molding the secondary bobbin 4 in a conventional example. The molding die 10 includes a movable die 101, a fixed die 102, and a slide 10.
3, slide Naka 104, Omonaka 105, frame A
106 and a frame B107. This is where the molten resin injected from the nozzle (not shown) of the injection molding machine is cooled and solidified in the molding die 10 to form the secondary bobbin 4. Since the secondary bobbin 4 has the flange 41, the mold adopts a slide structure, and the movable mold 101
Is moved in the horizontal direction, the slide Naka 104 is moved in the vertical direction, so that the secondary bobbin 4 can be taken out. In addition, the slide Naka 1 for forming the collar 41
04 is composed of a large number of pieces because air in the mold cavity passes through a gap (not shown) of the pieces when the molten resin is injected into the molding die 10. This is to make it possible to discharge smoothly to the outside.

FIGS. 4A to 4D are sectional views of the secondary bobbin 4 according to the present invention. In this case, FIG.
Unlike the conventional example shown in (b), the resin injected from the fan gate 45 or the ring gate 46 flows in the terminal support portion 42 in the longitudinal direction without a seam, that is, in a completely interlocked state. Therefore, no weld occurs. Here, in the case of the fan gate structure, since the gate cannot be automatically cut at the time of releasing the mold as in the case of the pinpoint gate, a gate cutting mechanism (not shown) is built in the mold, and the molded product is molded. The gate is cut before taking it out of the mold.

The gate cutting mechanism is controlled by hydraulic pressure or pneumatic pressure independently of an injection molding machine (not shown). Even if the gate cutting mechanism is not built in, if the so-called notch 45a is provided in a state where the cross-sectional area of the connection portion between the fan gate and the terminal support portion 42 is sharply reduced, the portion is the weakest portion in terms of strength. Therefore, it is also possible to automatically cut the gate when releasing the mold.

FIG. 5 is a sectional view of the secondary bobbin 4 according to the present invention. In this case, unlike the gate structure shown in FIG. 4, the pin point gate shown in the conventional example of FIGS. 2A and 2B is applied. The pinpoint gates 47a to 47d here are connected to tabs 48a to 48d provided on the side surface of the terminal support 42.

The tabs 48a to 48d are connected to the terminal support 4
The two side surfaces are generally provided at the same distance from the end surface. However, in order to allow the resin injected from the tabs 48a to 48d to the terminal support portion 42 to intermingle well by a swiveling motion (clockwise in this case), the end surface is intentionally used. , For example, in a staggered manner. In any case,
Since the resin which has been seamlessly mixed due to the swirling motion flows into the long cylindrical portion, no weld is generated. Although the case where the number of gates is four is shown here, the purpose is to cause the resin injected into the terminal support part 42 to make a turning motion. Any number of points may be used.

FIGS. 6A and 6B are sectional views of the secondary bobbin 4 according to the present invention. In this case, FIGS.
Unlike the gate structure shown in FIG.
This is an example in which gates 49a and 49b are provided on the 9th side. In the secondary bobbin having a thin and long cylindrical shape, the thickness of the cylindrical portion in the longitudinal direction is inevitably provided with a gradient due to a mold structure for removing a molded product. That is, the terminal support portion 42 side is thin and the diode mounting portion 49 side is thick.

For this reason, FIG.
In the structure in which the gate is provided on the side of the terminal support portion 42 shown in (a) and (b), since the resin flows from the thin side to the thick side,
There was a concern that the pressure would drop at the top of the resin and voids would occur at the center of the cylinder thickness.

Therefore, here, the diode mounting portion 4
Since a gate was provided on the 9th side to allow the resin to flow from the thick side to the thin side, it was possible to prevent pressure drop at the head of the resin and generation of voids at the center of the cylindrical thickness. Gate 4
Although 9a and 49b are pinpoints, since the diode mounting portion 49 side serves as a lid for the cylindrical portion, the resin injected from two points is integrated at the lid portion and then flows into the long cylindrical portion. Also, no weld occurs.

Although the above-described method is only related to the gate structure, a method of applying ultrasonic vibration to the cavity of the molding die in order to reduce the melt viscosity of the flowable resin and promote the intermingling of the resins. (Not shown), and a high-speed injection molding machine (not shown) having a large injection rate representing a flow rate per unit time in order to shorten the resin filling time and prevent the melt viscosity from decreasing. ) Is also effective.

[0020]

The present invention is a component part of a product which is required to be small and light, such as a pencil coil, and is used under severe environmental conditions where it is repeatedly exposed to a high temperature (about 130 ° C.) and a low temperature (about -40 ° C.). In the case of a thin, long cylindrical secondary bobbin, which is a thermoplastic resin molded product that requires heat resistance and a low coefficient of linear expansion, by preventing the occurrence of welds, which are molding defects, electrical insulation performance and mechanical A pencil coil excellent in durability with respect to strength can be realized.

[Brief description of the drawings]

1A and 1B are a side sectional view of a pencil coil and an AA line sectional view of FIG. 1A showing an embodiment of the present invention.

FIGS. 2A and 2B are a side sectional view of a secondary bobbin (end face injection method) and a right side sectional view of FIG.

FIG. 3 is a sectional view of a mold for molding a secondary bobbin in a conventional example.

FIGS. 4 (a) and (b), (c) and (b) are side sectional views and right sectional views of a secondary bobbin (full circumference injection method) showing an embodiment of the present invention. 2) is a side sectional view of the fare gate and the ring gate.

FIGS. 5A and 5B are a side sectional view of a secondary bobbin (side injection method) and a right side sectional view of FIG.

6 (a) and 6 (b) are side sectional views of a secondary bobbin (thick side injection method) showing the embodiment of the present invention and FIG. 6 (a).
FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Pencil coil, 2 ... Center core, 3 ... Soft epoxy, 4 ... Secondary bobbin, 5 ... Secondary coil, 10 ... Molding die, 41 ... Flange, 42 ... Terminal support part, 43 ... Pinpoint gate, 44 ... weld, 45 ... fan gate, 46 ...
Ring gate, 48 tab, 49 diode mounting part, 101 movable type, 102 fixed type, 103 slide, 104 slide Nakago.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Kazutoshi Kobayashi 882 Ma, Hitachinaka-shi, Ibaraki F-term in the Automotive Equipment Division, Hitachi, Ltd. 5E044 AC02 BA03

Claims (6)

[Claims] 1. A thin and long cylindrical secondary bobbin which is a molded article of a thermoplastic resin used for a pencil-shaped small coil (pencil coil) which is a kind of ignition coil for automobiles, for the purpose of improving electrical insulation. A method of manufacturing a pencil coil, characterized by preventing the occurrence of a weld, which is a molding defect, by devising a gate structure, which is a resin injection port. 2. A thin-walled long cylindrical secondary bobbin, which is a molded product of a thermoplastic resin, has a fan gate or ring gate structure in which the resin is injected from the entire periphery of the terminal supporting portion. A method for producing the pencil coil described in the above. 3. The manufacturing of a pencil coil according to claim 2, wherein a gate cutting mechanism is provided inside a molding die in a thin and long cylindrical secondary bobbin which is a molded product of a thermoplastic resin. Method. 4. A thin-walled long cylindrical secondary bobbin which is a molded product of a thermoplastic resin, wherein a gate is provided on a side surface of the terminal supporting portion so that the resin injected from each gate intersects with each other. The method for manufacturing a pencil coil according to claim 1. 5. A thin-walled long cylindrical secondary bobbin which is a molded article of a thermoplastic resin, wherein a gate for injecting the resin is provided on the thick side of the cylinder having a thickness gradient in the longitudinal direction. A method for manufacturing a pencil coil according to claim 1. 6. A thin and long cylindrical secondary bobbin which is a molded article of a thermoplastic resin, for the purpose of improving electrical insulation.
2. The method for manufacturing a pencil coil according to claim 1, wherein ultrasonic vibration is applied to the mold cavity when the molten resin is injected.