JP4014966B2 - 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 does not cause a problem during assembly.
[0002]
[Prior art]
FIG. 8 is a view showing a state (a) immediately before assembly of the conventional ignition coil 60 to the ignition plug 61 and a state (b) after completion of assembly.
[0003]
The illustrated ignition coil 60 includes a coil case 62, a plug cap 63 fitted to the lower end portion of the coil case 62, a primary coil 64 and a secondary coil 65 inserted in the coil case 62, and an upper portion of the coil case 62. It is comprised centering on the voltage supply part 66 accommodated in this. The illustrated coil case 62 has a divided structure of a main body 62A and a tip 62B, and a plug cap 63 is fitted to the coil case tip 62B.
[0004]
The ignition coil 60 is combined with the ignition plug 61 to realize the ignition operation of the internal combustion engine. As shown in FIG. 8A, the cylinder head 67 of the internal combustion engine has a plug communicating with a combustion chamber (not shown). A hole 68 is formed, and a spark plug 61 is fixed below the hole 68 with the discharge terminal 69 protruding into the combustion chamber.
[0005]
The outer diameter of the coil case 62 of the ignition coil 60 is determined corresponding to the diameter of the flag hole 68, and the insertion depth M of the ignition coil 60 is determined corresponding to the depth L of the plug hole 68. . Accordingly, when the ignition coil 60 is lowered to the limit position of the plug hole 68 at the time of assembly, the plug tower 70 of the ignition plug 61 enters the flag cap 63, and the ignition coil 60 and the ignition coil 60 are energized by the biasing force of the spring 71 in the compressed state. A reliable electrical connection with the spark plug 61 is realized.
[0006]
[Problems to be solved by the invention]
By the way, if the coil case 62 is divided as shown in FIG. 8, the manufacturing process becomes complicated, and an integrally formed coil case is also preferably used. FIG. 9 illustrates an engagement portion between the plug cap 63 and the plug tower 71 in the ignition coil 60 including the integrally formed coil case 62. As described above, when the coil case 62 is an integrally molded product, the thickness of the case tip portion 62b cannot be made as thin as the case tip portion 62B of the split structure, so that the ignition coil 60 and the spark plug 61 can be assembled well. There were cases where it was not possible.
[0007]
That is, the ignition coil 60 and the ignition plug 61 are generally correctly assembled as shown in FIG. 9A. However, the depth L of the plug hole 68 and the insertion depth M of the ignition coil 60 are respectively Since there are allowable errors ± ΔL and ± ΔM, in the worst case, the elastic deformation limit of the plug cap 63 may be exceeded as shown in FIG. 9B. FIG. 9B is a diagram showing that the elastic deformation limit of the plug cap 63 may be exceeded, and in fact, it cannot be assembled as shown.
[0008]
Here, it is conceivable to increase the inner diameter and the outer diameter of the plug cap 63 while maintaining the thickness of the case distal end portion 62b. As a result, reliable fitting and insulation performance are deteriorated.
[0009]
The present invention has been made in view of the above-described problems, and it is an object of the present invention to provide an ignition coil that is suitably applied to an ignition coil that integrally forms a coil case and that eliminates problems during assembly. .
[0010]
[Means for Solving the Problems]
In order to solve the above-described problems, the present invention provides an ignition coil including a plug cap made of an elastic body that receives an ignition plug, and a coil case to which the plug cap is fitted. , And the plug cap is located radially inward of the enlarged diameter surface and extends in a radially inwardly inclined direction from the distal end side toward the proximal end side. A small cylindrical portion (52) is provided. In the present invention, the foremost inner peripheral surface of the coil case has a diameter-enlarged surface, and a small cylindrical portion (52) is provided on the inside thereof, so that the ignition coil can be used without any problem regardless of the dimensional accuracy of the ignition coil or plug hole. Can be assembled.
[0011]
In addition, this invention is applied suitably for the ignition coil whose coil case is an integrally molded product made of synthetic resin. An opening groove corresponding to the innermost peripheral surface of the coil case is provided on the inner periphery of the plug cap, and the opening groove has a second cylindrical portion (51) extending in the axial direction and the diameter-expanding. Typically, the small cylindrical part (52) having substantially the same angle as the surface is formed in a substantially V shape.
[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]
FIG. 3A illustrates the case tip 1c in detail, and FIG. 3B illustrates the state where the plug cap 2 is attached to the case tip 1c. As shown in the figure, the case tip 1c is formed with a substantially smaller diameter than the case body 1a by the thickness of the plug cap 2, and an engagement protrusion is formed between the large-diameter cylindrical portion 42 and the small-diameter cylindrical portion 43. Article 44 is circulated. The engagement protrusion 44 includes an inclined surface 44c for receiving the plug cap 2, an outer peripheral flat surface 44b extending in the axial direction, and a radial end surface 44a substantially orthogonal to the outer peripheral flat surface 44b. Ensuring the engagement is secure.
[0019]
A holding end surface 45 that holds the high-voltage terminal 9 is provided on the proximal end side of the inner peripheral surface of the case distal end portion 1c. The holding end surface 45 extends in the axial direction from the holding end surface 45 toward the distal end side in the axial direction. An inner peripheral flat surface 47 and a second tapered surface 48 are connected. Sufficient mechanical strength is ensured by such a gradual diameter expansion structure from the base end side toward the tip end side. The material of the coil case is not particularly limited, but a thermoplastic synthetic resin such as PPS (polyphenylene sulfide) or modified PPO (modified polyphenylene oxide) is preferably used.
[0020]
FIG. 4A illustrates a specific configuration of the plug cap 2 fitted to the above-described case tip 1c. As shown in the figure, the plug cap 2 has a large-diameter cap base end portion 2a and a small-diameter cap distal end portion 2c connected in series through a cap inclined portion 2b. Further, reinforcing ribs 2d extending in the axial direction are provided at equal intervals in the circumferential direction on the upper surfaces of the cap inclined portion 2b and the cap small diameter portion 2c (FIG. 4C). The plug cap 2 is made of a rubber material having appropriate elasticity and excellent insulation performance.
[0021]
On the inner peripheral side of the cap base end portion 2 a and the cap inclined portion 2 b, a first cylindrical surface 49 extending in the axial direction that fits into the large-diameter cylindrical portion 42 of the coil case 1 and an engagement protrusion 44 are fitted. Engaging groove 50, second cylindrical surface 51 extending in the axial direction that fits into small-diameter cylindrical portion 43, and inclined radially inward from the distal end side to the proximal end side of second cylindrical surface 51. An extending small cylindrical portion 52 is formed.
[0022]
As shown in the drawing, the small cylindrical portion 52 has a tapered shape with a small diameter toward the proximal end without changing its thickness, and the taper angle is the second tapered surface 48 of the case distal end portion 1c. This corresponds to the taper angle. Therefore, the V-shaped groove formed by the second cylindrical portion 51 and the small cylindrical portion 52 accommodates the small diameter cylindrical portion 43 and the second tapered surface 48 of the case tip portion 1c without difficulty.
[0023]
In addition, instead of forming the small cylindrical part 52 continuously with the inner peripheral surface of the cap small diameter part 2c as in the embodiment of FIG. 4A, a small cylinder as shown in FIG. While the portion 52 is slightly thinned, the cap small diameter portion 2c may be slightly thickened. That is, the thickness t2 of the cap small-diameter portion 2c in FIG. 4B is set to t2> t1 as compared with the thickness t1 of the cap small-diameter portion 2c in FIG. In this case, a step 53 is formed at the connecting portion between the small cylindrical portion 52 and the cap small-diameter portion 2c. Thus, the step 53 is not straight but provided from the inner diameter of the cap small-diameter portion 2c to the small cylindrical portion 52. Thus, the rubber deformation pressure when the spark plug is received in the cap small diameter portion 2c is not transmitted in the direction of the large diameter surface 48. As a result, when the ignition coil is inserted into the spark plug, the insertion force can be reduced, and at the same time, no pressure is applied to the diameter-expanded surface 48, so that connection between the two can be realized without stress.
[0024]
As described above, in this embodiment, the second tapered surface 48 is formed on the most distal inner peripheral surface of the case tip 1c, and the small cylindrical portion 52 of the plug cap is positioned inside the second tapered surface 48. The trouble when assembling to the spark plug is solved. That is, the plug tower can be reliably received in the ignition coil CL regardless of the dimensional accuracy of the spark plug and the plug hole that accommodates the spark plug.
[0025]
Hereinafter, the other parts of the ignition coil will be described for reference. As shown in FIG. 1C, the coil case 1 includes a primary coil portion 3, a secondary coil portion 4, and a center core portion 5 therein. Although inserted, the center core portion 5 includes a central iron core 14 formed by laminating silicon steel plates having a thickness of about 0.3 mm, a protective member 15 that covers the central iron core 14 in a cylindrical shape, and the length of the central iron core 14. It is comprised with the protective cap 16 which covers the both ends of a 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.
[0026]
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.
[0027]
As shown in FIG. 5 (b), the outer iron core 6 has a simple substantially cylindrical shape having no slit, and has a substantially C-shaped cross section in which only one portion 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.
[0028]
As shown in FIG. 5A, the bobbin 19 of the primary coil portion 3 includes a bobbin main body 19a around which the primary winding 20 is wound, a bobbin upper end portion 19b 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.
[0029]
The bobbin upper end portion 19b is provided with a total of four extension arms 24A, 24B, 25A, and 25B extending in the front-rear direction of the paper surface of FIG. 5A (see FIG. 6A). 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. .
[0030]
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.
[0031]
As shown in FIG. 5 (a), the bobbin lower end portion 19c is, in detail, substantially the same surface as the small diameter portion 31 having substantially the same diameter as the bobbin main body 19a and the protective tape 21 fitted to 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.
[0032]
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. 5A. On one side thereof, the notch groove 34 is adjacent to the notch groove 34 and has a 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.
[0033]
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.
[0034]
FIG. 6B illustrates a plan view of the secondary coil unit 4. As shown in FIG. 6B, at the upper end portion of the bobbin 17 of the secondary coil portion, 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, 36. 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.
[0035]
FIG. 6C 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.
[0036]
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.
[0037]
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 of the secondary coil portion 4 (FIG. 6B). 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.
[0038]
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.
[0039]
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).
[0040]
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.
[0041]
The ignition coil CL thus completed is assembled to the ignition plug 61. FIG. 7A illustrates this state, and shows a state in which the inner peripheral surface of the cap tip portion 2 c that is originally formed straight is compressed and deformed by the plug tower 70 of the spark plug 61. ing. In the case of FIG. 7, the plug cap 2 having the configuration shown in FIG.
[0042]
As shown in FIG. 7A, when the plug hole depth L and the ignition coil insertion depth M are the design values, the small cylindrical portion 52 of the plug cap is assembled without being particularly elastically deformed. Is completed. On the other hand, from the relationship between the tolerances ± ΔL and ± ΔM, even when the plug hole depth L−ΔL and the ignition coil insertion depth M + M, as shown in FIG. Is appropriately elastically deformed to complete the assembly.
[0043]
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 to provide a diameter-expanding portion that expands on the tip end side on the innermost peripheral surface of the coil case, and further provide an elastic deformation portion on the inner peripheral side, and other than that, as appropriate Can be changed.
[0044]
【The invention's effect】
As described above, according to the present invention, it is possible to realize an ignition coil for an internal combustion engine that is suitably applied to an ignition coil that integrally molds a coil case and that eliminates problems during assembly.
[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 diagram illustrating a configuration of a tip portion of a coil case.
FIG. 4 is a diagram illustrating a configuration of a plug cap.
FIG. 5 is a front view of a bobbin (a) of a primary coil and an outer iron core (b) fitted to the bobbin (a).
6A is a plan view of a primary coil section, FIG. 6B is a plan view of a secondary coil section, and FIG. 6C is a rear view of a voltage supply section.
FIG. 7 is a drawing for explaining an assembled state of the ignition coil.
FIG. 8 is a drawing for explaining the positional relationship between an ignition coil and a spark plug.
FIG. 9 is a diagram illustrating an assembled state of a conventional ignition coil.
[Explanation of symbols]
CL Ignition coil 1 Coil case 2 Plug cap 48 Expanded surface (tapered surface)
52 Substantially cylindrical part (small cylindrical part)

Claims (3)

In an ignition coil comprising a plug cap made of an elastic body that receives an ignition plug, and a coil case to which the plug cap is fitted,
The innermost peripheral surface of the coil case is a diameter-expanded surface that expands toward the distal end side, and the plug cap is located on the radially inner side of the diameter-expanded surface, from the distal end side toward the proximal end side. An ignition coil for an internal combustion engine, characterized in that a small cylindrical part extending inwardly in a radial direction is provided.   The ignition coil for an internal combustion engine according to claim 1, wherein the coil case is an integrally molded product made of a synthetic resin. An opening groove corresponding to the innermost peripheral surface of the coil case is provided on the inner periphery of the plug cap, and the opening groove substantially includes a second cylindrical portion extending in the axial direction and the diameter-enlarging surface. The ignition coil for an internal combustion engine according to claim 1, wherein the ignition coil is formed in a substantially V shape with the small cylindrical portion having the same angle.

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