JP4014965B2 - Ignition coil for internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an ignition coil that supplies a high voltage to an ignition plug of an internal combustion engine such as an automobile engine, and more particularly, to an ignition coil for an internal combustion engine that is improved so that cracks do not occur in a coil case.
[0002]
[Prior art]
In general, the ignition coil includes a secondary coil in which a central iron core is inserted, a primary coil disposed outside the secondary coil, and an exterior iron core disposed outside the primary coil. Here, the exterior iron core is for forming an optimum magnetic path of magnetic flux interlinking with two coils.
[0003]
As the shape of the outer core, a configuration in which a large number of slits formed short in the axial direction as described in Japanese Utility Model Publication No. 3-106720 may be provided. However, in terms of the manufacturing process and manufacturing cost, there is no simple slit. A rectangular plate material curved into a cylindrical shape is used. However, regardless of the presence or absence of a short slit, the open end of the exterior iron core is single and its cross section is substantially C-shaped.
[0004]
[Problems to be solved by the invention]
By the way, the ignition coil is exposed to a large change in heat between when the internal combustion engine is stopped and when it is in operation, and accordingly, each component member repeatedly expands and contracts, and in some cases, a crack may occur in the coil case. there were. If a crack occurs in the coil case, the outer iron core will rust, and it will not cause a particularly fatal trouble, but it may give a little distrust to the part that touches the user's eyes. is there.
[0005]
This invention is made | formed in view of this problem, Comprising: It aims at providing the ignition coil for internal combustion engines improved so that a crack might not arise in a coil case.
[0006]
[Means for Solving the Problems]
In order to solve the above problems, the inventor has repeated experiments and examinations. As a result, as shown in FIG. 5, the open end of the outer iron core having a C-shaped cross section and the parting line of the coil case are radially It has been found that cracks are likely to occur in the coil case. In particular, when the parting line of the coil case and the open end portion of the outer iron core are aligned on the same line not only in the radial direction but also in the axial direction of the ignition coil, the adverse effect is great.
[0007]
Here, the parting line is a line that occurs at the mating part of the mold when the coil case is manufactured by molding, and thermal stress is concentrated on that part due to the discontinuity of the thickness of the coil case. It is a part to be. On the other hand, in the case of an exterior iron core having a C-shaped cross section, it is considered that stress is concentrated on the opposite side of the open end, and the weakest part of the exterior iron core and the coil case are aligned in the axial direction of the ignition coil. It is considered that a crack occurs in the coil case in the axial direction, and the present invention has been completed based on such knowledge.
[0008]
That is, the gist of the present invention is that the discontinuous portion of the thickness of the coil case and the stress concentration portion of the outer core are not aligned on the same line in the axial direction of the ignition coil, more specifically. An ignition coil comprising a coil case integrally formed by a mold and an outer iron core having a substantially C-shaped cross section fitted to the outer periphery of a coil portion inserted in the coil case, in the axial direction of the coil case The extending mold alignment line and the symmetrical position line extending in the axial direction are assembled so as not to be aligned at the same position in the circumferential direction of the coil case at a position shifted by 180 degrees from the open end of the outer core. . In addition, by not aligning the mold alignment line and the symmetrical position line at the same position in the circumferential direction of the coil case, the discontinuous portion of the thickness of the coil case and the stress concentration portion of the outer iron core are reduced. They are not aligned on the same line in the axial direction .
[0009]
The outer core is preferably configured by curving a plate material that is not provided with a slit. In addition, the coil case is formed in a substantially cylindrical shape, and an angle formed between the mold alignment line of the coil case, the symmetrical position line of the open end portion of the exterior iron core, and the center of the coil case is approximately 90. It is preferable to set the degree.
[0010]
It is preferable that a substantially U-shaped groove is formed at the axial end of the open end of the outer core, and in this case, the substantially U-shaped groove is engaged with a protrusion formed on the bobbin of the coil portion. Is positioned. More preferably, the primary coil portion and the secondary coil portion are positioned by fitting a mounting flange formed on one bobbin into a recess formed on the other bobbin.
[0011]
Further, in integrating the primary coil part and the voltage supply part, it is preferable to fit one cylindrical protrusion into a cylindrical hole formed in the other, and a slide formed in the voltage supply part. It is preferable that the groove is slid into the receiving end face of the coil case and integrated as a whole.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, based on an Example, embodiment of this invention is described more concretely. Fig.1 (a) is a fragmentary sectional view which shows schematic structure of the ignition coil CL based on an Example, FIG.1 (b) is a whole circuit block diagram of the ignition coil CL.
[0013]
The ignition coil CL includes a coil case 1 (1a, 1b, 1c) formed integrally with a plastic mold, a rubber plug cap 2 fitted to the lower end portion of the coil case 1, and an internal coil case 1. The primary coil portion 3 to be inserted, the secondary coil portion 4 to be inserted into the primary coil portion 3, the center core portion 5 to be inserted into the secondary coil portion 4, and the outer periphery of the primary coil portion 3 are elastically fitted. It is comprised centering on the exterior iron core 6 and the voltage supply part 7 accommodated in the upper part of the coil case 1. FIG.
[0014]
The primary coil portion 3, the secondary coil portion 4, and the center core portion 5 are positioned concentrically, and a thermosetting epoxy resin 8 is vacuum-injected and cured so as to eliminate gaps in the respective portions. The voltage supply unit 7 is a part that supplies a pulse voltage to the primary coil unit 3. In this embodiment, the voltage supply unit 7 includes a power transistor PTr that performs an ON / OFF operation in response to the ignition pulse S (FIG. 1B). )reference).
[0015]
Specifically, the coil case 1 includes a cylindrical case main body 1a, a case base end 1b that accommodates the voltage supply unit 7, a high-voltage terminal 9 that receives a high voltage from the secondary coil unit 4, and an ignition plug (not shown). And a case tip 1c that holds a spring 10 for transmitting high pressure to the case.
[0016]
As shown in FIG. 2, the case base end 1b has a substantially cylindrical shape with one side (left side in FIG. 1) cut out in a rectangular shape, and a metal tube 11a on the other side (right side in FIG. 1). An interior mounting hole 11 is provided. The mounting hole 11 is used as a bolt hole when the ignition coil CL is mounted on a cylinder head such as an engine.
[0017]
A U-shaped receiving end surface 12 is formed in the cutout portion of the case base end portion 1 b so as to be engaged with the U-shaped slide groove 7 a of the voltage supply portion 7. That is, when the voltage supply unit 7 is received, the slide groove 7a is slid downward while sandwiching the receiving end surface 12 of the case base end 1b.
[0018]
The material of the coil case 1 having such a configuration is not particularly limited, but a thermoplastic synthetic resin such as PPS (polyphenylene sulfide) or modified PPO (modified polyphenylene oxide) is preferably used. In any case, since the coil case 1 is integrally formed using a plastic mold, a parting line 13 is inevitably generated on the contact surfaces of the plastic molds facing each other. In this embodiment, the case main body 1a is formed by facing two plastic molds from the front and back of the paper surface of FIG. 1, so that the parting line 13 is formed at the left and right positions of FIG. 1 (a). Become.
[0019]
As shown in FIG. 1 (c), the coil case 1 has a primary coil portion 3, a secondary coil portion 4 and a center core portion 5 inserted therein. The center core portion 5 is a plate having a thickness of about 0.3 mm. A central iron core 14 formed by laminating thick silicon steel plates, a protective member 15 that covers the central iron core 14 in a cylindrical shape, and a protective cap 16 that covers both ends of the central iron core 14 in the length direction. The protective cap 16 is in close contact with the central iron core 14 and the protective member 15, thereby reliably preventing the inflow of the epoxy resin 8 filled to seal the gap of the ignition coil CL.
[0020]
The secondary coil unit 4 includes a secondary bobbin 17 and a secondary winding 18 wound around the secondary bobbin 17. The primary coil unit 3 includes a primary bobbin 19, a primary winding 20 wound around the primary bobbin 19, and a cylindrical protective tape 21 covering the periphery of the primary winding 20. The outer iron core 6 is elastically fitted to the outside of the protective tape 21. The outer iron core 6, together with the central iron core 14, is optimally disposed between the primary winding 20 and the secondary winding 18. It is for forming a magnetic path.
[0021]
As shown in FIG. 3 (b), the outer iron core 6 has a simple substantially cylindrical shape having no slits, and has a substantially C-shaped cross section in which only one part in the circumferential direction is opened by bending. It has become. At the upper and lower end portions of the C-shaped open end portion 22, substantially U-shaped grooves 23 that are further cut out are formed. The material of the outer core 6 having such a structure is not particularly limited as long as it is a magnetic body having elasticity that can be fitted to the primary coil portion 3, but is preferably the same material as the central core. A thin silicon steel plate is used.
[0022]
As shown in FIG. 3A, the bobbin 19 of the primary coil unit 3 includes a bobbin main body 19 a around which the primary winding 20 is wound, a bobbin upper end portion 19 b from which the primary winding 20 is drawn, and the outer iron core 6. It is roughly divided into a bobbin lower end portion 19c for receiving and positioning. Note that the axial length of the bobbin main body 19 a is set to be substantially the same as the axial length of the outer core 6.
[0023]
The bobbin upper end portion 19b is provided with a total of four extension arms 24A, 24B, 25A, 25B extending in the front-rear direction of the paper surface of FIG. 3A (see FIG. 4A). Cylindrical holes 26 are respectively provided on the base end sides of the extension arms 24 and 25, and the primary coil portion 3 and the voltage supply portion 7 are positioned by the four cylindrical holes 26. .
[0024]
A rectangular concave portion 27 is formed between the proximal ends of the adjacent extension arms 24 and 25, and the primary coil portion 3 and the secondary coil portion 4 are positioned by the concave portion 27. Yes. Further, cylindrical portions 28 project from the distal ends of the extension arms 24 and 25, respectively, and the primary winding 20 drawn out to the drawing groove 29 is drawn through the cylindrical portions 28 to be the primary winding. The start point and the end point of the line 20 are held by the locking piece 30.
[0025]
As shown in FIG. 3 (a), the bobbin lower end portion 19c has a small diameter portion 31 that is substantially the same diameter as the bobbin main body 19a, and a protective tape 21 that is fitted on the outer periphery of the primary winding 20. It is divided into a medium-diameter portion 32 that becomes one and a large-diameter flange portion 33 having the maximum diameter. The large-diameter flange portion 33 and the medium-diameter portion 32 are formed with notch grooves 34 at both side positions on the radial line of the primary bobbin 19, and the small-diameter portion 31 and the bobbin main body 19 a are flush with each other through the notch grooves 34. Communicate.
[0026]
The notch groove 34 is on the radial line of the primary bobbin 19 and is provided in the front-rear direction of the paper surface of FIG. 3A, and on one side thereof, close to the notch groove 34, the large diameter flange portion. 33 extension pieces 33a are formed. The extension piece 33 a is obtained by extending the large-diameter flange portion 33 in the axial direction, and has a shape and a size corresponding to the substantially U-shaped groove 23 of the exterior iron core 6. That is, the length in the axial direction of the extension piece 33 a is substantially the same as the length in the axial direction of the substantially U-shaped groove 23 of the outer core 6, and the maximum circumferential width L of the extension piece 33 a is approximately equal to that of the substantially U-shaped groove 23. It is almost the same as the circumferential width.
[0027]
For this reason, when the outer iron core 6 is appropriately rotated in a state where the expanding force is released after the outer iron core 6 is slightly expanded and pushed in from the lower side of the primary coil portion 3, the outer iron core 6 is substantially rotated by the elastic force of the outer iron core 6. The U-shaped groove 23 is engaged with the extension piece 33a, so that the primary coil portion 3 and the outer core 6 are correctly positioned. That is, in the mounted state of the outer core 6, the open end 22 of the outer core 6 correctly matches the extending direction of the extension arms 24 and 25 of the primary bobbin 19, and the axial movement of the outer core 6 is as follows. The large-diameter flange portion 33 is reliably prevented.
[0028]
FIG. 4B illustrates a top plan view of the secondary coil unit 4. As shown in FIG. 4B, the upper end portion of the bobbin 17 of the secondary coil portion has a lead-out portion 35 of the secondary winding 18 and a pair of mounting flanges 36 extending in a direction orthogonal to the lead-out portion 35. , 36 are provided. The mounting flange 36 has a size and a shape corresponding to the concave portion 27 of the bobbin 19 of the primary coil portion, and positions the secondary coil portion 4. That is, in a state where the secondary coil portion 4 is inserted into the bobbin 19 of the primary coil portion, the two mounting flanges 36 and 36 are respectively fitted in the two concave portions 27 and 27 of the bobbin 19, and in this state, the primary coil portion 3. And the secondary coil part 4 are positioned concentrically.
[0029]
FIG. 4C is a rear view showing the back side of the voltage supply unit 7. As illustrated, four cylindrical protrusions 37 are provided on the back surface of the voltage supply unit 7. The cylindrical protrusions 37 are formed corresponding to the cylindrical holes 26 of the bobbin 19 of the primary coil portion, and the four cylindrical protrusions 37 are fitted into the four cylindrical holes 26 so that the voltage supply unit 7 and the primary coil portion 3 are positioned.
[0030]
A pair of connection terminals 38 and another connection terminal 39 are extended from the voltage supply unit 7. The pair of connection terminals 38 and 38 are formed in an L shape with a horizontal portion 38a and a vertical portion 38b, respectively. When the voltage supply portion 7 is positioned on the bobbin 19 of the primary coil portion, the two vertical portions 38b and 38b are The primary winding 20 drawn out from the bobbin 19 is sandwiched. The connection terminal 38 is connected to the primary winding 20, and the connection terminal 39 is connected to the secondary winding 18.
[0031]
Next, an assembly method for the ignition coil CL having the above configuration will be described. First, the center core portion 5 is inserted into the central opening 40 (FIG. 4B) of the secondary coil portion 4. In addition, since the outer diameter of the protective cap 16 of the center core part 5 is substantially the same as the inner diameter of the central opening 40 of the secondary coil part 4, the centers of both coincide correctly.
[0032]
Subsequently, the secondary coil portion 4 in this state is inserted into the bobbin 19 of the primary coil portion 3. As described above, the two mounting flanges 36 and 36 are fitted into the two recesses 27 and 27 for positioning. Next, in this state, the voltage supply unit 7 is overlaid on the primary coil unit 3, and the four cylindrical protrusions 37 of the voltage supply unit 7 are fitted into the four cylindrical holes 26 of the bobbin 19.
[0033]
In this state, since the voltage supply unit 7 and the primary coil unit 3 and the secondary coil unit 4 are correctly positioned, the primary winding 20 is connected to the connection terminal 38 and the secondary winding 18 is connected to the connection terminal 39. Connect to. As a result of the above processing, the primary coil unit 3, the secondary coil unit 4, and the voltage supply unit 7 are integrated, so that the slide groove 7a of the voltage supply unit 7 is slid into the receiving end surface 12 of the coil case 1. The whole is integrated (see FIG. 2).
[0034]
In this state, the parting line 13 of the coil case 1 and the open end 22 of the outer core 6 are correctly positioned as shown in FIG. Therefore, after vacuuming in this state, the thermosetting epoxy resin 8 is filled in each gap and cured to fix the whole.
[0035]
As mentioned above, although the Example of this invention was described concretely, the concrete description content does not specifically limit this invention. That is, the gist of the present invention is that the discontinuous portion of the thickness of the coil case and the stress concentration portion of the outer iron core are not aligned on the same line in the axial direction of the ignition coil, and other than that, appropriately It can be changed.
[0036]
For example, in the case of the embodiment, magnets are not particularly provided on both sides in the axial direction of the central iron core, but it is also preferable to arrange permanent magnets that generate a magnetic flux in a direction opposite to the magnetic flux from the central iron core. . In addition, for the purpose of preventing cracks, a cushioning material or the like may be disposed at an appropriate place.
[0037]
【The invention's effect】
As described above, according to the present invention, it is possible to realize an internal combustion engine ignition coil that is improved so that cracks do not occur in the coil case.
[Brief description of the drawings]
FIG. 1 is a partial sectional view (a), a circuit configuration diagram (b), and a CC sectional view (c) of an ignition coil according to an embodiment.
FIG. 2 is a diagram illustrating a method for assembling a voltage supply unit to a coil case.
FIG. 3 is a front view of a bobbin (a) of a primary coil and an outer iron core (b) fitted to the bobbin (a).
4A is a plan view of a primary coil section, FIG. 4B is a plan view of a secondary coil section, and FIG. 4C is a rear view of a voltage supply section.
FIG. 5 is a drawing for explaining problems of a conventional ignition coil.
[Explanation of symbols]
CL Ignition coil 1 Coil case 6 Exterior iron core 13 Mold alignment line (parting line)

Claims (3)

In an ignition coil comprising a coil case integrally molded by a mold, and an outer iron core having a substantially C-shaped cross section fitted to the outer periphery of a coil portion inserted in the coil case,
The die alignment line extending in the axial direction of the coil case and the symmetrical position line extending in the axial direction are not aligned at the same position in the circumferential direction of the coil case at a position shifted by 180 degrees from the open end of the exterior core. An ignition coil for an internal combustion engine characterized by being assembled as described above.   2. The ignition coil for an internal combustion engine according to claim 1, wherein the outer iron core is formed by curving a plate material not provided with a slit. The coil case is formed in a cylindrical shape,
The angle formed with the die alignment line of the said coil case, the symmetrical position line of the open end part of the said exterior core, and the center of the said coil case is set to 90 degree | times. Ignition coil for internal combustion engines.

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