JP2006080189A - Ignition coil for internal combustion engine and automobile - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ignition coil improved so as to be able to effectively prevent the generation of an adhesive burr. <P>SOLUTION: In the ignition coil for an internal combustion engine, a primary coil and a secondary coil are arranged outside a central core 1 in a coaxial manner. In the ignition coil, approximately the whole body in the axial direction of the central core 1 is covered with an insulating film TP while both end sections 1C and 1C in the axial direction of the central core 1 exposed from the insulating film TP are covered with core caps CP and constituted. In the ignition coil, notched grooves or notches are formed to terminal faces 1D and 1D in the axial direction of the central core 1. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an ignition coil for an internal combustion engine that is attached to a plug hole of an engine of an automobile or the like and is used with an ignition plug attached to a tip portion thereof, and an automobile incorporating the ignition coil.

As an ignition coil for an internal combustion engine, a secondary coil wound around a secondary bobbin is disposed outside a round bar-shaped central iron core, and a primary coil wound around a primary bobbin is further disposed outside the secondary coil. It has been known. The central iron core is generally constructed by laminating a plurality of silicon steel sheets, and an insulating buffer tape is wound around the central iron core, and core caps are covered on both axial ends of the central iron core. Is known (Patent Document 1).
JP 2004-71911 A

  In the central iron core having the configuration as described in Patent Document 1, the adhesive may overflow from the core cap when the core cap is assembled. ), The crack may occur in the mold resin around the central iron core. And when a crack generate | occur | produces in mold resin, malfunctions, such as the ignition characteristic of an ignition coil getting worse by insulation failure, will arise.

  As a cause of the overflow of the adhesive, the shape of the inner peripheral surface of the core cap must be substantially matched with the outer peripheral surface shape of both ends in the axial direction of the central iron core. Here, the two shapes are almost the same in order to achieve reliable adhesiveness, which is an unavoidable condition for manufacturing.

  8 and 9 are diagrams for explaining an adhesive burr caused by an overflowing adhesive. Here, a state in which the tip portion TOP of the buffer tape 51 wound around the central iron core 50 is inserted while forcibly expanding the core cap 52 is shown in relation to manufacturing tolerance of each member. . In such an inserted state, the adhesive 53 rushes into a slight gap in a slightly pressurized state, and as a result, the adhesive 53 overflows vigorously from the core cap 52. was there. In particular, when the core cap 52 holding the adhesive 53 is covered with the central iron core 50 held in a horizontal state, the adhesive 53 moves vertically downward as shown in FIG. As a result, the possibility that the adhesive 53 overflows from the core cap 52 is increased.

  The overflowing adhesive not only impairs the commercial value of the appearance, but the adhesiveness that is originally planned is impaired by the amount of the overflowing adhesive. When the amount of the adhesive 53 held in the core cap 52 is larger than the design value, a considerable amount of the adhesive 53 overflows from the core cap 52, so that the adverse effect of the adhesive burr is more serious. It becomes.

  This invention is made | formed in view of said problem, Comprising: It aims at providing the improved ignition coil so that generation | occurrence | production of an adhesive burr | flash can be prevented effectively. It is another object of the present invention to provide an automobile incorporating an ignition coil that can effectively prevent the occurrence of adhesive burrs.

  In order to achieve the above object, an invention according to claim 1 is directed to an internal combustion engine ignition coil in which a primary coil and a secondary coil are coaxially disposed outside a central iron core. Covering substantially the whole axial direction with an insulating film, and covering both axial ends of the central iron core exposed from the insulating film with a core cap, the axial end surface of the central iron core has a cut groove Alternatively, a notch is formed.

  Further, the invention according to claim 2 is an assembling step of laminating a plurality of types of magnetic steel plates to form a central iron core, and a cutting step of forming a cut groove or a notch in the axial end surface of the central iron core. And a tape winding step of winding an insulating tape around the outer peripheral surface of the central iron core, and an adhesion step of covering the both ends of the central iron core in the axial direction with a substantially cylindrical core cap attached thereto. An ignition coil for an internal combustion engine.

  In each of the above inventions, a cut groove or a notch is formed in the axial end surface of the central iron core. Therefore, when the core cap is put on the central iron core, the cut groove or the cut is made of the adhesive. Functions as a moving passage. Therefore, even if a pressurized state occurs when the core cap is attached, the adhesive spreads smoothly over the entire area of both ends in the axial direction of the central iron core, resulting in poor adhesion due to uneven distribution of the adhesive and overflow of the adhesive. The problem is solved. In addition, the cut groove and notch function as an adhesive reservoir, so even if the core cap is in a pressurized state, it will be retained in the core cap without overflowing to the outside. Is done. In addition, the cut groove and notch can also serve as a positioning groove to hold the center iron core in a predetermined state in the operation of covering the whole axial direction of the center iron core with an insulating film, and assembling accuracy can be increased. It can also be improved.

  In the present invention, the shape and structure of the cut groove is not particularly limited. However, when a central iron core is formed by laminating a plurality of strip-shaped steel plates, it passes through the central point of the central iron core, and the one in the laminating direction. A cut groove formed by cutting a part of all the steel plates from the side to the other side in a straight line is preferable. Such a cut groove may be formed after the center iron core is assembled, or a notch may be provided in the steel plate in advance. However, from the viewpoint of ease of manufacture and accuracy, it is effective to form the cut groove after the center iron core is assembled.

  The cut groove is not necessarily one, and a plurality of cut grooves may be provided. In this case, it is effective to form a cut groove in a straight line passing through the center point of the central iron core, and to form a cross shape or a radial shape as a whole.

  On the other hand, when the end surface is notched, for example, as shown in FIG. 7, the end surface may be cut into an arc or other concave shape. In this configuration, the recess provided on the end surface functions as an adhesive reservoir (relief space). Therefore, even when a pressure is generated inside the core cap when the core cap is attached, the space through which the adhesive escapes is provided. There is no fear that the adhesive will be ejected to the outside as much as is secured.

  In the case of a central iron core with a substantially polygonal cross section, the peripheral straight line portion of the end surface functions as a movement path for the adhesive, so it is not necessary to cut out all the steel plates in the stacking direction to provide cut grooves However, it is also effective to provide a recess that does not cut the peripheral edge of the end face.

  As described above in detail, according to the present invention, it is possible to realize an improved ignition coil so as to effectively prevent the occurrence of adhesive burrs. Further, since the cut groove and the notch can be used for positioning, a highly accurate ignition coil can be manufactured smoothly.

  Hereinafter, an ignition coil for an internal combustion engine according to an embodiment will be described from a schematic configuration thereof. FIG. 1 is a schematic longitudinal sectional view of an ignition coil according to an embodiment. This ignition coil is attached to the plug hole of the engine, and a spark plug is attached to the tip of the ignition coil to directly supply a high voltage to the spark plug.

  As shown in the drawing, the ignition coil of the present embodiment has a primary winding wound around a central iron core 1, a secondary coil 3 wound around a secondary bobbin 2, and a primary bobbin 4 in order from the center. The primary coils 5 are arranged concentrically and are housed in a substantially cylindrical case 6. Further, an outer iron core 7 made of a steel plate having a notch in a part in the circumferential direction and formed in a substantially C shape is attached to the outer peripheral surface of the primary coil 3. In addition, in order to suppress saturation of the magnetic flux of the iron core, permanent magnets that generate a magnetic flux in a direction opposite to the magnetic flux generated by the primary coil 5 may be attached to both ends in the longitudinal direction of the central iron core 1.

  The case 6 is filled with a thermosetting epoxy resin. This epoxy resin penetrates between the central iron core 1 and the secondary coil 3, between the secondary coil 3 and the primary coil 5, and between the primary coil 5 and the case 6, respectively, and ensures insulation between them. . In addition, although the large diameter part 6a in which the igniter 8 etc. are accommodated is formed in the upper part of the case 6, the epoxy resin is also filled in this large diameter part 6a. This epoxy resin is injected and filled from the upper opening of the case 6 and is cured by being held in a furnace maintained at a uniform curing atmosphere temperature for a certain period of time.

  An igniter 8 as an ignition drive circuit for turning on and off the primary current is provided at the upper part of the case 6, and a primary current input connector terminal 9 for supplying the primary current to the igniter 8 is provided. A spring 11 is provided under the case 6 via a secondary high voltage terminal 10 electrically connected to the secondary coil 3. A spark plug is connected to the lower part of the case 6 via the spring 11. The connecting portion is built in a protector 12 provided at the lower portion of the case 6 so that a high voltage does not leak into a metal portion such as a plug hole.

  A buffer tape TP having electrical insulation is wound around the outer peripheral surface of the central iron core 1. The buffer tape TP of the present embodiment is a thin polyester film, and a rectangular film having an inner surface coated with an adhesive is wound around the outer peripheral surface of the central iron core 1. The buffer tape TP is wound with a little left and right end portions 1C and 1C of the center iron core 1, so that the upper and lower end portions 1C and 1C of the center iron core 1 are exposed exposed from the buffer tape TP. Part.

  A bottomed cylindrical core cap CP is attached to the exposed portions (upper and lower end portions) 1C and 1C. The core cap CP is formed of an elastic body having excellent heat resistance, and is bonded to both ends of the central iron core 1 and functions as a buffer material that absorbs the difference in thermal expansion coefficient between the strip plate PL and the epoxy resin. To do.

The ignition coil of the present invention basically has the above-described structure, but particularly has a feature in the structure and manufacturing method of the central iron core 1, and this point will be further described. The central iron core 1 of the present embodiment includes: (1) a cutting process for cutting a magnetic steel sheet with a press device to produce a plurality of types of strip plates PL... The strip plate PL... PL is bundled and laminated, and the assembly process is integrated by caulking, and (3) the cut groove 1A or 1D is formed on the axial end surfaces 1D and 1D of the integrated strip plate. A cutting step for forming a notch recess, (4) a tape winding step for winding a buffer tape around the outer peripheral surface of the central iron core 1, and (5) axial end portions (exposed portions) 1C, 1C of the central iron core 1 It is manufactured through a bonding process in which a substantially cylindrical core cap CP is put on and bonded.
[Cutting process to excision process]
FIG. 2 (a) illustrates the state of the central iron core 1 after the assembly process. In this embodiment, strip plates PL ... PL made of silicon steel plates of about 0.2 to 0.5 mm are shown. A plurality of layers are laminated to form a central iron core 1 having a substantially octagonal cross section as a whole. As shown in the drawing, a predetermined number of the widest strips are arranged at the center in the stacking direction, and strips with a narrow width are sequentially arranged above and below the strips in the stacking direction.

  In the case of this embodiment, since the crimping process is performed in the direction of the arrow in the figure prior to the cutting step, two to three recesses 1B are formed at regular intervals in the length direction of the central iron core. Convex portions are formed at symmetrical positions opposite to each other in the radial direction. Note that the strip plates PL may be bonded to each other with an epoxy adhesive instead of the caulking process, or the end surfaces 1D at both ends in the axial direction of the central iron core 1 may be replaced with or in addition to the caulking process. May be welded. When welding is performed in addition to caulking, the central portion of the end surface 1D of the central iron core 1 is welded in a substantially rectangular shape in the stacking direction of the strips before cutting (see FIG. 2 ( c)). This is in order to balance the thermal expansion coefficient in the stacking direction of the strips with the thermal expansion coefficient in the direction orthogonal thereto, and the substantially rectangular welding surface WL is formed by the cut groove 1A provided in the subsequent cutting process. It is wide and is formed about half the diameter of the central iron core.

In any case, a cut groove 1A is formed in the axial cutting ends 1D of the central iron core after the assembly process in the next cutting process. FIG. 2B illustrates the central iron core 1 after the cutting process. In this embodiment, a cut groove 1A is formed in the stacking direction of the strips. As illustrated, the cut groove 1A is formed in a straight line by cutting off a part of all the strip plates from the one side to the other side through the center point of the central iron core. In order to omit this excision step, the cut groove 1A may be formed in each strip plate PL in the cutting step of cutting out a plurality of types of strip plates.
[Tape winding process]
Next, the central iron core 1 in which the cut grooves 1A are formed on both end faces 1D in the axial direction is transferred to a tape winding process. In this case, since the cut groove 1A can be used for positioning, the tape winding accuracy can be increased accordingly.

  In this tape winding process, a buffer tape TP that is slightly narrower than the axial length of the central iron core 1 is wound around the outer periphery of the central iron core 1 (see FIG. 1). By covering the outer periphery of the central iron core 1 with the buffer tape TP, the electrical insulation of the strip plate which is a silicon steel plate is ensured. Further, by covering with the buffer tape TP, the edge portions at both ends in the width direction of each strip plate PL are relaxed, and the edge portions are prevented from coming into direct contact with the epoxy resin covering the center iron core 1, and thermal expansion / The occurrence of cracks in the epoxy resin due to stress concentration on the edge due to heat shrinkage is prevented.

  FIG. 3 illustrates a schematic configuration of the tape winding device 20 used in the tape winding process. The tape winding device 20 includes a tape reel 22 that holds the buffer tape TP, a tape transport roller 23 that unwinds the buffer tape TP from the tape reel 22, a pair of winding rollers 24A and 24B that rotate in the same direction, The pressing roller 25 that rotates the central iron core 1 in a pressed state in cooperation with the turning rollers 24A and 24B, the cutting blade 26 that cuts the buffer tape TP, and the central iron core 1 in the standby state are wound on the winding rollers 24A and 24B. And a transport mechanism (not shown) for taking out the central iron core 1 that has finished the tape winding operation.

  The tape conveying roller 23 and the winding roller 24 are rotated and stopped by being controlled by a controller (not shown), and the pressing roller 25 and the cutting blade 26 are appropriately controlled to be moved up and down by being controlled by the controller. . The buffer tape TP is a belt-like polyester film having a thickness slightly shorter than that of the central iron core 1 and having an adhesive layer on the back surface (upper side in the drawing) and having a thickness of about 60 μm. It is unwound on the path 27 and cut to the required length by the lowering of the cutting blade 26.

  The tape winding device 20 shown in FIG. 3 is in a standby state immediately before starting the tape winding operation, the tape conveying roller 23 and the winding roller 24 are stopped, and the pressing roller 25 and the cutting blade 26 are in the raised position. . In this standby state, a buffer tape TP having a length Ls is drawn forward from the cutting blade 26. Further, the central iron core 1 stands by in a posture in which each strip plate PL is in a horizontal state.

  FIG. 4 illustrates the moment when the standby state of FIG. 3 is shifted to the operation start state. First, a transport mechanism (not shown) holds the central iron core 1 in a standby state and places it between the winding rollers 24A and 24B. At this time, the central iron core 1 is placed so that the strip plate PL is positioned on a horizontal plane, but the buffer tape is positioned so that the tip of the buffer tape is positioned at the center of the lower surface of the lowermost strip plate. The TP withdrawal length Ls is set.

  When the central iron core 1 is placed between the winding rollers 24A and 24B, the pressing roller 25 descends and presses the uppermost strip plate of the central iron core 1. As a result, the entire central iron core 1 is pressed downward, and the buffer tape TP is securely bonded to the left half of the lower surface of the lowermost strip. Next, the winding rollers 24A and 24B start to rotate in the clockwise direction as the tape transport roller 23 starts to rotate in the counterclockwise direction. Of course, the rotational speeds of the rollers 23 and 24 are set so that the outer peripheral speed of the tape transport roller 23 having the radius R and the outer peripheral speed of the winding rollers 24A and 24B coincide with each other.

  When the winding rollers 24A and 24B rotate in the clockwise direction, the central iron core 1 pressed by the pressing roller 25 rotates in the counterclockwise direction, and the pressing roller 25 rotates in the clockwise direction. As is apparent, in this state, the tape transport roller 23 sends out the buffer tape TP toward the central iron core 1A at a speed corresponding to the bonding speed at which the buffer tape TP is bonded to the central iron core 1. Then, at the timing when the rotation angle from the start of rotation of the tape transport roller 23 reaches θ, the total length of the buffer tape TP sent to the winding rollers 24A and 24B is R × θ + Ls. Here, R is the radius of the tape transport roller 23, and Ls is the initial drawing length (FIG. 3).

  When the buffer tape TP is sent until the condition of R × θ + Ls = S (Expression 1) is satisfied by the rotation of the tape transport roller 23 and the winding roller 24, the rotation of the tape transport roller 23 and the winding roller 24 is performed. In this state, the cutting blade 26 descends and cuts the buffer tape TP (see FIG. 5A). In the above (Formula 1), S is the winding length of the buffer tape TP around the central iron core 1, and is located at the strip plate located at the adhesion start point ST of the buffer tape TP and the adhesion end point END. The strip plate is set so as to be symmetric with respect to the radial direction (see FIG. 5C).

  That is, the winding length S is set to S = n × L + L / 2 corresponding to the outer peripheral length L of the central iron core 1 and the number of windings n of the buffer tape TP. In the case of the present embodiment, the strip plate serving as the adhesion start point ST is the strip plate located in the lowermost layer in FIG. 4, so the strip plate serving as the adhesion end point END is the strip plate located in the uppermost layer in FIG. 4. It becomes.

3 to 5 described above, the winding work of the buffer tape TP around the central iron core 1 is completed. FIG. 5 (c) illustrates the center iron core 1 in a completed state, and a buffer tape TP slightly narrower than the axial length of the center iron core 1 is more than a single layer on the outer periphery of the center iron core 1. It is wound. Then, the adhesion start point ST and the adhesion end point END are in a radially symmetric position, and are located on the strip plate PL having the narrowest width in the stacking direction. Even in this state, the upper and lower ends 1C of the central iron core 1 are exposed to the outside without being covered with the buffer tape TP.
[Core cap bonding process]
Then, it transfers to the adhesion | attachment process which covers and adheres the core cap CP to the upper-and-lower-ends part 1C of the center iron core 1. Here, the core cap CP is made of silicone rubber because it has strong heat resistance and cold resistance and appropriate elasticity. In particular, in this embodiment, a transparent or translucent silicone rubber is used. Here, the silicone rubber is a rubber whose main chain is composed of a silicon-oxygen bond with respect to a general synthetic rubber whose main chain is a carbon-carbon bond. However, it is not particularly limited, and fluorine rubber may be used because it has heat resistance and cold resistance that exceed those of silicone rubber. Also in this case, it is preferable to use transparent or translucent fluororubber.

  The reason why the upper and lower ends 1C of the central iron core 1 are covered and fixed with the core cap CP is to absorb the difference in thermal expansion coefficient between the strip plate and the epoxy resin with the core cap CP. This is to prevent the epoxy resin from cracking due to stress concentration caused by thermal expansion / shrinkage with the axial end face 1D as a base point.

  FIG. 6A shows a core cap CP formed in a bottomed cylindrical shape. As shown in the figure, the circular hole of the core cap CP is a stepped hole with a slightly reduced diameter on the back side (lower side in the figure) from the axial center of the core cap CP. That is, as shown in FIG. 6E, in the state where the central iron core 1 is fitted in the core cap CP, the exposed side surface 1C (central iron core) in which the buffer tape TP is not wound around the small-diameter portion 13 on the back side. Are arranged so that the central iron core 1 around which the buffer tape TP is wound is disposed in the large-diameter portion 14 on the opening side. The large-diameter portion 14 has a tapered shape with an inclination angle γ that narrows outwardly of about 2 °.

  In the core cap bonding step, first, a silicone-based adhesive 15 is injected into the core cap CP. In this embodiment, since a silicone (silicon resin) -based adhesive is used, it has rubber elasticity after curing, and exhibits stable properties over a wide temperature range.

  After the core cap CP having the adhesive is prepared, the central iron core 1 is held in a horizontal state, and the core cap CP is pressed and covered on both axial end surfaces 1C in the horizontal direction. Then, the adhesive 15 is pressed and spread by the core cap CP. However, in the present embodiment, the cut groove 1A is formed on the end surface 1D of the central iron core 1, so that the adhesive 15 is cut into the cut groove 1A. To the exposed side surface 1C of the central iron core. That is, in the present embodiment, the adhesive 15 spreads uniformly on the exposed side surface 1C of the central iron core 1, and the adhesive 15 is ejected from one place in a pressurized state to spread the core cap CP and overflow. There is no such thing as going out.

  Moreover, in this embodiment, since the core cap is transparent or translucent, the spread state of the adhesive inside the core cap can be surely confirmed visually. If there is an adhesive overflowing from the core cap, immediately Abnormalities can be detected. In addition, for the purpose of facilitating the abnormality detection work, an appropriate colorant may be added to the originally transparent adhesive 15.

  Although the embodiments of the present invention have been specifically described above, the above description is merely an example, and can be appropriately changed without departing from the spirit of the present invention. For example, the shape of the cut groove is not necessarily a straight line, and is not necessarily formed by cutting out all the strip plates. That is, the recessed part formed in the terminal surface of a center iron core may be sufficient.

It is a schematic longitudinal cross-sectional view which shows one Example of the ignition coil of this invention. It is a schematic perspective view which expands and shows the termination | terminus surface of the center iron core of the ignition coil of FIG. It is the schematic which shows the structure of a tape winding apparatus. It is drawing explaining the operation start state of a tape winding apparatus. It is drawing explaining the operation | movement middle of a tape winding apparatus. The core cap and the central iron core with the core cap attached are illustrated. It is drawing which illustrated the notch structure of this invention. It is drawing explaining the problem of a prior art. It is drawing explaining the problem of a prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Center iron core 1C Axial direction both ends 1D Axial end surface 2 Secondary bobbin 3 Secondary coil 4 Primary bobbin 5 Primary coil TP Insulation film (buffer tape)
CP core cap

Claims (4)

In the internal combustion engine ignition coil formed by coaxially arranging a primary coil and a secondary coil on the outside of the central iron core,
Covering substantially the whole axial direction of the central iron core with an insulating film material, and covering both axial ends of the central iron core exposed from the insulating film with a core cap,
An ignition coil for an internal combustion engine, wherein a notch groove or a notch is formed in an axial end surface of the central iron core. An assembly process for stacking a plurality of types of magnetic steel sheets to form a central iron core, an excision process for forming a cut groove or a notch in the axial end surface of the central iron core, and an outer peripheral surface of the central iron core An ignition coil for an internal combustion engine, comprising: a tape winding step for winding an insulating tape; and an adhesion step for covering and adhering a substantially cylindrical core cap to both axial ends of the central iron core. . 2. The ignition coil for an internal combustion engine according to claim 1, wherein the central iron core is configured by laminating a plurality of magnetic steel materials, and the cut grooves are formed in a straight line in a laminating direction of the steel materials. An automobile provided with the ignition coil according to claim 1.

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