JPH10256062A - Ignition coil for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To miniaturize an ignition coil while maintaining the ignition performance by surely winding the coil of a secondary coil around a secondary bobbin without requiring a large number of collar parts. SOLUTION: At least a pair of collar parts 21p and 21q are formed so that they oppose a secondary bobbin 21 of a cylindrical body at a specific distance, and the coil winding of a secondary coil 22 is wound on the outer-periphery surface between the collar parts. The inner surface of the collar part 21q at the winding start side of the coil winding of the secondary coil 22 is formed on an inclined surface 21t that is inclined at a specific angle for the axis of the secondary bobbin 21. An annular groove 21j is formed at a boundary between the inclined surface 21t and the outer-periphery surface of the secondary bobbin 21, and a coil winding is subjected to traction along the inclined surface 21t from here.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ignition coil for an internal combustion engine in which a primary coil and a secondary coil are mounted on a columnar member made of a magnetic material, and more particularly to a secondary coil having a pair of flanges of a secondary bobbin. The present invention relates to an ignition coil for an internal combustion engine wound around an outer peripheral surface between the parts.

[0002]

2. Description of the Related Art Recently, there has been a demand for further miniaturization of an ignition coil for an internal combustion engine. For example, as disclosed in Japanese Patent Application Laid-Open No. 4-87311, a magnetic core is bundled to form a central core. It is known to form a primary coil and a secondary coil around it. This is intended to form the ignition coil into a small cylindrical shape so as to be housed in the cylindrical plug hole of the engine. As disclosed in the publication, in this type of ignition coil,
A secondary coil is wound around a bobbin divided into a plurality of sections.

[0003]

Since the ignition coil described in the above publication requires a large number of flanges, there is a restriction on the reduction in the axial length. Although the winding of the secondary coil is not described in detail, it is generally necessary to suppress the potential difference between lines and the capacitance when winding the winding of the secondary coil. In this regard, Japanese Unexamined Patent Publication No. 3-44907
Although this publication is different from the subject of the present invention, in a small transformer used for a driver of a cold cathode fluorescent lamp, a transformer wound according to oblique lap winding in order to reduce a potential difference and a capacity between lines of a secondary coil. Is disclosed. In this publication, a coil section having a triangular coil section is formed in the vicinity of one flange of the bobbin, the intermediate section is repeatedly wound up and down in an oblique direction and wound, and the vicinity of the other collar is wound. A winding portion serving as an inverted triangular coil section layer is formed.

However, in the ignition coil described in Japanese Patent Application Laid-Open No. 3-44907, the outer peripheral surface of the bobbin main body and the inner side surface of the flange portion are orthogonal to each other, so that a triangular coil sectional layer is formed. This is not easy to perform winding work, and there is a possibility that winding disturbance or loose turn (looseness) may occur. In particular, it is not appropriate to directly apply the winding structure of the secondary coil in the transformer described in the publication to ignition coils for internal combustion engines having different use environment conditions. For example, if the potential difference between the lines becomes large due to the occurrence of a loose turn, the ignition performance is degraded, and if excessive tension is applied to the winding, there is a risk of disconnection.

On the other hand, when a secondary coil is wound around a secondary bobbin having an inclined flange as shown in FIG. 21, for example, the winding is started in the direction indicated by the arrow at the winding start portion. Moves and shifts as shown by the broken line, so that a loose turn occurs. Therefore, this cannot be put to practical use. still,
The circles in FIG. 21 indicate the cross sections of the windings, and the numbers in the circles indicate the winding order.

On the other hand, when the ignition coil is formed in a cylindrical shape as described in the above-mentioned Japanese Patent Application Laid-Open No. 4-87311, it is desirable that the center iron core, that is, the inner core, is also formed in a cylindrical shape. As one of the means, there is a method of bundling a plurality of wire rods as described in the same gazette, but it is difficult to manufacture and assemble, and the cost is increased. Therefore, it is appropriate that the inner core is basically formed by laminating a plurality of steel plates and has a substantially circular cross section. When manufacturing such an inner core, a rectangular cross section is generally formed at both ends. Further, in order to prevent the leakage magnetic flux, it is necessary to make both ends of the inner core rectangular in cross section, and to make the cross sectional area larger than that of the intermediate portion. However, since the outer diameter cannot be increased due to the demand for miniaturization, the distance between both ends of the inner core and the secondary coil wound around the inner core is inevitably reduced. For this reason, in this ignition coil, there is a problem in electrical insulation particularly at a portion where the winding of the secondary coil is connected to the high voltage terminal.

In view of the above, the present invention provides an internal combustion engine ignition coil comprising a magnetic columnar member having a primary coil and a secondary coil mounted thereon. An object of the present invention is to reduce the size while reliably winding the wire and maintaining the ignition performance.

[0008]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention relates to an ignition coil for an internal combustion engine comprising a magnetic columnar member and a primary coil and a secondary coil mounted thereon.
A secondary bobbin of a cylindrical body that has at least a pair of flanges formed so as to face each other at a predetermined distance and that winds the winding of the secondary coil on the outer peripheral surface between the pair of flanges. The inner bobbin of the secondary bobbin is provided with, among the inner surfaces of the pair of flanges opposing each other, the inner surface of the flange on the winding start side that starts winding the secondary coil between the pair of flanges. It is formed on an inclined surface inclined at a predetermined angle with respect to the axis, and an annular groove is formed at a boundary between the inclined surface and the outer peripheral surface of the secondary bobbin.

In the ignition coil for an internal combustion engine, it is preferable that a guide groove extending from the annular groove to the outer periphery of the flange on the winding start side is formed on the inclined surface of the flange on the winding start side. The inner side surface of the flange on the winding start side may be formed as an inclined surface inclined at least 17 degrees with respect to the axis of the secondary bobbin. Further, the depth of the annular groove may be larger than the outer diameter of the winding.

The present invention also provides a magnetic columnar member having an intermediate portion formed in a substantially circular cross section and both ends formed in a rectangular cross section, and a primary member formed by winding a winding around the intermediate portion of the columnar member. A coil, a secondary coil formed by winding a winding so as to surround the columnar member and the primary coil, and a high-voltage terminal connected to an end of the winding of the secondary coil near one end of the columnar member Wherein the secondary coil winds a winding around a secondary bobbin of a cylindrical body accommodating the columnar member and the primary coil with a predetermined gap between both ends of the columnar member and the primary coil. A portion of the secondary bobbin surrounding the end of the columnar member on the high-voltage terminal side is formed into a large-diameter cylindrical body, and a portion surrounding an intermediate portion of the columnar member is formed outside. While forming into a small diameter cylindrical body, An inclined surface inclined at a predetermined angle with respect to the axis of the secondary bobbin is formed between the small-diameter cylinder and the large-diameter cylinder, and an annular surface is formed at a boundary between the inclined surface and the outer peripheral surface of the secondary bobbin. A groove is formed, and a guide groove extending from the annular groove to the outer periphery of the large-diameter cylindrical body is formed on the inclined surface, and one layer of the secondary coil winding is formed on the outer peripheral surface of the large-diameter cylindrical body. After winding, guiding the annular groove through the guide groove, winding the winding of the secondary coil starting from the annular groove to form a plurality of layers in the small-diameter cylindrical body Is also good.

The columnar member may be a laminated body formed by laminating a plurality of silicon steel plates so that the cross-sectional area of both ends of the rectangular cross section is larger than the cross-sectional area of the middle part of the substantially circular cross section. desirable. Also, an intermediate portion of the inner core, and an insulating coating formed by, for example, powder coating on a portion adjacent to the intermediate portion of both ends of the inner core, after winding the primary coil on the insulating coating of the intermediate portion, A primary coil assembly may be formed by molding an elastic material, the secondary coil may be wound around the primary coil assembly and housed in a case, and then the case may be filled with an insulating material to form an ignition coil. . In this case, an epoxy resin may be used as the insulating material, and an elastomer may be used as the elastic material.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of an ignition coil for an internal combustion engine according to the present invention will be described below with reference to the drawings. FIG. 22 shows the entirety of an ignition coil for an internal combustion engine according to an embodiment of the present invention, in which a case 60 includes an igniter portion 60d of a housing having an upper opening and a cylinder extending downward from the bottom surface thereof. It is a container-shaped housing made of a synthetic resin having a coiled portion 60a and a high-voltage terminal portion 60b. FIGS. 1 to 4 show these cross sections, and FIG.
10 to FIG.

As shown in FIGS. 1 and 2, an inner core 10, which is a columnar member of the present invention, a primary coil 12, a secondary coil assembly 20,
The outer core 30 and a pair of auxiliary cores and permanent magnets (represented by 40 and 50, respectively) are housed therein. The igniter 8 is housed in the igniter section 60d, and the connector section 60c is integrally formed.
The igniter 8 controls the primary current of the primary coil 12, and is also called an ignition module. A post 60e is formed in the igniter section 60d, and the igniter 8 is inserted through the post 60e for positioning. A high-voltage terminal 7 is built in the lower high-voltage terminal portion 60b in FIGS. 1 and 2, and a plug cap 70 formed in a cylindrical shape with an insulating material (for example, rubber) is mounted outside the high-voltage terminal portion 60b. ing.

The inner core 10 of the present embodiment is formed by laminating a plurality of flat plates of a magnetic material, for example, eight kinds of silicon steel plates in total of 26 sheets, and has a substantially circular outer shape as shown in FIGS. Intermediate section 10a of cross section and enlarged section 1 of rectangular cross section
0b at both ends. Intermediate part 10
a, as shown in FIG. 14, a first portion P1 that is laminated in the order of increasing width of the silicon steel plate, and a second portion that laminates a predetermined number of silicon steel plates having the same width continuously to the first portion. Part P
2 and a third portion P3, which is successively stacked on the second portion P2 in the order of gradually decreasing the width of the silicon steel sheet, is sequentially joined by stacking to form a laminate, which is formed in the middle of a substantially circular section having a diameter of about 8 mm. It becomes a columnar member having the portion 10a. As shown in FIG. 12, both ends of this columnar member have
The enlarged portion 10b has a rectangular cross section having a larger cross-sectional area than that of the intermediate portion 10a. The silicon steel sheet of the inner core 10 shown in FIG. 1 is included in the second portion P2.

Here, the term "stacking" refers to forming a concave portion on one surface and a convex portion on the other surface of each of a plurality of flat plates at the time of press molding, and forming the plurality of flat plates on a surface facing each other. The convex portions are sequentially polymerized while being pressed into the concave portions,
Means for forming a laminate. In the present embodiment, as shown in FIG. 1, two rectangular stacking portions Sa in plan view are formed in the intermediate portion 10 a of the inner core 10, and the longitudinal directions of the stacking portions Sa are provided in the enlarged portions 10 b at both ends. A single rectangular stacking portion Sb in a plan view is formed which is orthogonal to the direction. In FIG. 2 and the like, hatching of the cross section of the inner core 10 is omitted because it is difficult to determine the hatching.

As described above, after the inner core 10 composed of the laminated body of the silicon steel sheets is formed, the outer surface of the inner core 10 is subjected to powder coating of an insulating material, and FIGS.
As is apparent from FIG. The insulating coating 11 is formed over the entire length of the intermediate portion 10a of the inner core 10, and the insulating coating 11b is also formed on the enlarged portion 10b adjacent thereto. Thereby, each silicon steel plate of the inner core 10 is hardly peeled off,
Sufficient bonding strength is ensured. Further, the diameter is greatly reduced as compared with the conventional primary bobbin.

The winding of the primary coil 12 is wound in two or four layers on the outer peripheral surface of the insulating coating film 11a in the intermediate portion 10a. At this time, the portion of the insulating coating film 11b of the enlarged portion 10b functions in the same manner as the flange portion of the conventional primary bobbin, so that it can be appropriately wound. Particularly, in the present embodiment, the cross section of the intermediate portion 10a of the inner core 10 is substantially circular, and the insulating coating film 11 is formed on the side surface by powder coating, so that the edge portion becomes a smooth surface. As described above, in the present embodiment, the insulating coating film 11b is formed on a part of the enlarged portion 10b, but may be formed on all side surfaces or on the whole. Further, the insulating coating film 11 may be formed using a resin-based coating or an adhesive.

A pair of concave portions 10c are formed on both side surfaces of the enlarged portion 10b of the inner core 10, and these concave portions 1c are formed.
The holder 14 is locked to 0c as shown in FIG. 1, FIG. 2, and FIG. 15 to FIG. The holder 14 is a resin member having a pair of extending portions 14b formed on one end side of an annular support portion 14a and a pair of engaging portions 14c formed on the other end side. But each inner core 10
It is configured to be locked by the pair of concave portions 10c. Each of the pair of extension portions 14b has a primary terminal 1
5 and 16 are integrally supported, and both ends of the winding of the primary coil 12 are electrically connected to respective base ends.

The inner core 10, the primary coil 12 and the holder 14 constructed as shown in FIGS. 15 to 17 are molded by an elastomer of an elastic material, and are formed as shown in FIGS. 1, 2, 7 and 8. An elastic layer 19 is formed around the periphery of the primary coil 12 and the primary coil 12, and these constitute a primary coil assembly. Incidentally, the elastomer is a polymer substance having high elasticity and usually shows rubber elasticity at around normal temperature.

On the other hand, the outer core 30, which forms a magnetic circuit together with the inner core 10, is formed of a silicon steel plate in a cylindrical shape as shown in FIGS. 1 and 6 to 9, and fits outside the coil portion 60a of the case 60. Is being worn. Further, as shown in FIGS. 1 and 2, rectangular permanent magnets 50 are disposed at both ends in the axial direction of the inner core 10, and an auxiliary core 40 formed by laminating a substantially rectangular silicon steel plate outside the permanent magnets 50. Is arranged. The permanent magnets 50 arranged at both ends are arranged such that the directions of the generated magnetic flux are the same, and opposite to the direction of the magnetic flux formed in the inner core 10 when the primary coil 12 is energized. .
Thus, the above-described inner core 10, permanent magnet 50, auxiliary core 40, and outer core 30 constitute a magnetic circuit.

The auxiliary cores 40 disposed at both axial ends of the inner core 10 are molded with an elastomer of an elastic material, respectively, and holders 49 and 49x (the low-pressure side is represented by 49x because the outer shape is slightly different between the high-pressure side and the low-pressure side). ) Is formed. The permanent magnets 50 are accommodated in the holders 49 and 49x, respectively, and are mounted on both ends of the inner core 10. The holder 4 on the high-voltage terminal 7 side
9 further includes a permanent magnet 50 containing the permanent magnet 50 therein.
A cylindrical portion 49a extending outward from the end surface of the inner core 10 is formed, and an end of the inner core 10 on which the elastic layer 19 is formed is fitted into the cylindrical portion 49a.

A secondary coil assembly 20 is provided so as to accommodate the primary coil assembly. The secondary coil assembly 20 is formed by winding a secondary coil 22 around a secondary bobbin 21 as shown in FIGS. The secondary bobbin 21 is a cylindrical body made of a synthetic resin (for example, modified polyphenylene oxide). As shown in FIG. 18, a portion surrounding the end of the inner core 10 on the high-voltage terminal 7 side is a cylinder having a large outer diameter. A portion formed on the body 21b and surrounding the intermediate portion of the inner core 10 is formed on a cylindrical body 21a having a small outer diameter.

Between these cylindrical bodies 21a and 21b,
An inclined surface 21t inclined at a predetermined angle (preferably 17 degrees or more) with respect to the axis of the secondary bobbin 21 is formed. That is,
The inner surface of the flange portion 21q is an inclined surface 21t inclined at a predetermined angle with respect to the axis of the secondary bobbin 21, as schematically shown in FIG. An annular groove 21j is formed at the boundary between the inclined surface 21t and the outer peripheral surface of the cylindrical body 21a. The depth of the annular groove 21j is larger than the outer diameter of the winding. Further, a guide groove 2 extending from the annular groove 21j to the outer periphery of the cylindrical body 21b is formed on the inclined surface 21t as shown in FIG.
1 g is formed.

As shown in FIG. 18, flanges 21p, 21q, and 21s are formed on the outer peripheral surface of the secondary bobbin 21, but are not divided into a large number of sections as in the prior art. No collar is required, and the axial length of the secondary bobbin 21 is reduced accordingly, and the axial length of the entire ignition coil is reduced accordingly. Note that annular grooves 21e and 21v are formed in the flanges 21p and 21s, respectively. The winding of the secondary coil 22 is wound one layer around the groove 21e and one layer around the outer peripheral surface of the cylindrical body 21b by an automatic winding machine (not shown), and then passes through the notch 21h. It is guided to the annular groove 21j of the cylindrical body 21a via the guide groove 21g. Thereafter, the windings of the secondary coil 22 are sequentially wound around the outer peripheral surface of the cylindrical body 21a starting from the annular groove 21j to form a plurality of layers.

FIG. 20 shows the winding sequence of the secondary coil 22 around the cylindrical body 21a of the secondary bobbin 21.
The windings are wound in the order indicated by numerals in the circular cross section of the winding of FIG. 20 by an automatic winding machine (not shown). That is, the winding of the secondary coil 22 starts from the annular groove 21j and the inclined surface 21t.
Is wound up in the radial direction of the secondary bobbin 21, for example, after being wound seven times, and then is wound down to the cylindrical body 21a side,
Furthermore, it is wound up along the inclined surface 21t. In this way, the winding and the unwinding are repeated and sequentially wound in the axial direction, thereby forming the secondary coil 22 shown in FIG.
Therefore, the winding operation can be reliably performed while preventing a loose turn, and both reduction of the potential difference between lines and maintenance of the winding state can be achieved.

As shown in FIGS. 1 and 2, of the portion of the winding of the secondary coil 22 wound around the secondary bobbin 21, the enlarged portion 10 of the inner core 10 on the high voltage terminal 7 side
The end 22h of the winding of the secondary coil 22 wound around the cylindrical body 21b in the portion surrounding b is a cylindrical body composed of one layer of winding. That is, the relationship is such that the conductor surface of the assembly of the windings and the surface of the inner core 10 do not face one core and the core or the like. In addition, since this conductor surface is located on the outermost side in the radial direction of the secondary bobbin 21, electric field concentration is less likely to occur at this portion, and even if it occurs, it is greatly reduced as compared with the conventional case. . Note that the end portion 22h may be formed in two or more layers, but it is preferable that the end portion 22h be one layer because the end portion 22h expands in the radial direction.

On the other hand, as shown in FIGS. 1 and 2, a rib 21r extending in the axial direction is formed on the inner surface of the end of the secondary bobbin 21 on the side arranged on the high pressure terminal 7. The rib 21r is in contact with the elastic layer 19, and the winding of the secondary coil 22 is held so as to be separated from the inner core 10 and the primary coil 12 with a predetermined gap.

As shown in FIGS. 1 to 4, the secondary coil 2
A secondary terminal 18 is provided on the low pressure side of 2,
The base end portion is fitted in the groove 21e of the flange portion 21p, and the front end portion 18a (FIG. 4) is formed so as to extend in the axial direction while being bent in a crank shape. Thus, the end of the winding of the secondary coil 22 on the low pressure side is formed by the axial groove 2 of the flange 21p.
1f (FIG. 3) and wound around the proximal end of the secondary terminal 18. 1 to 4 and FIG.
And the extension 21 of the secondary bobbin 21 as shown in FIG.
A secondary terminal 17 is attached to c and 21d, and an end on the high voltage side of the winding of the secondary coil 22 is connected to the leg 17d on the extension 21d side.

The secondary terminal 17 is formed by bending a plate made of a conductive material into a U-shape.
A hole 17a having an engagement projection is formed, and the tip of the high-voltage terminal 7 is engaged with the hole 17a. The leg 17c is locked to the extension 21c, and the leg 17d is locked to the extension 21d. The end of the winding of the secondary coil 22 is engaged with the claw 17f via a concave portion 17e formed in the leg 17d, and in this state, solder (indicated by 17g in FIG. 3) is attached to the concave portion 17e. You. Thus, after the winding of the secondary coil 22 is wound around the secondary bobbin 21, it is immediately connected to the secondary terminal 17 from the groove 21v.

As shown in FIG. 2, first to fourth connector terminals 61 to 64 are arranged in parallel in a connector portion 60c formed integrally with the case 60. An igniter terminal (not shown) is provided at the base end side of the first to fourth connector terminals 61 to 64.
Is connected. Furthermore, connector terminals 61 and 6
Primary terminal 1 with igniter terminal 3
5 and 16 are connected, and the power supply to the primary coil 12 is intermittently controlled. The first connector terminal 61 is connected to a power supply (not shown), and the primary terminal 15 is connected to the base end thereof together with the igniter terminal. As shown in FIG. 5, the primary terminal 15 is formed with a bent portion having a hole 15a.
a is inserted and soldered in the state shown in FIG.

In manufacturing and assembling the ignition coil having the above-described configuration, as described above, a plurality of ignition coils (for example, 8 types of 2
(Six) silicon steel sheets are joined by stacking to form the inner core 10. As shown in FIGS. 11 to 14, an insulating coating 11 is formed on the outer surfaces of the intermediate portion 10a and the enlarged portion 10b of the inner core 10, and the winding of the primary coil 12 is wound on the insulating coating 11a of the intermediate portion. Is done. After the holder 14 is attached to the inner core 10 and both ends of the winding of the primary coil 12 are connected to the primary terminals 15 and 16, the elastic layer 19 is molded as shown in FIGS. A coil assembly is formed.

On the other hand, the outer core 30 is formed into a cylindrical shape by a silicon steel plate and is pressed into the outside of the coil portion 60a of the case 60, or the silicon steel plate is wound around the coil portion 60a. Further, as described above, the secondary coil 22 is wound around the secondary bobbin 21 to form the secondary coil assembly 20, and the primary coil assembly is connected to the secondary bobbin 21.
Housed in the hollow part of Subsequently, the permanent magnets 50 are respectively housed in holders 49 and 49x in which the auxiliary cores 40 are built, and mounted on both ends of the inner core 10 in the axial direction. Further, after the secondary terminals 17 and 18 are mounted on the secondary bobbin 21, the winding of the secondary coil 22 is changed to the secondary terminal 1.
7 and 18 are electrically connected. As described above, the secondary bobbin 21 is accommodated in the case 60 with the secondary terminals 17 and 18 mounted. Further, the high-voltage terminal unit 60
b, the high pressure terminal 7 is pressed into the secondary terminal 17.
Is electrically connected to

The igniter section 60d of the case 60
The igniter 8 is accommodated in the connector terminals 61 to 64 and connected to the primary terminals 15 and 16.
Are connected to the connector terminals 61 and 63, respectively. Thus, one end of the winding of the secondary coil 22 is connected to the secondary terminal 1.
8 and the primary terminal 15 are connected to the connector terminal 61, and the other end is connected to the high voltage terminal 7 via the secondary terminal 17.

Thereafter, the coil portion 60a and the igniter portion 60d are filled with epoxy resin as an insulating material and cured to form the insulating portion 13 in the coil portion 60a as shown by stippling in FIGS. 13 is omitted in other drawings). As a result, the primary coil 12 and the secondary coil 22 are impregnated and fixed, the electrical connection portion is appropriately insulated, and the electrical insulation that can withstand the output high voltage of the secondary coil 22 is secured. The coil section 60a, the high-voltage terminal section 60b and the igniter section 6 shown in FIG.
0d and the connector 60c may be formed separately, and the coil 60a and the igniter 60d may be joined.

The ignition coil for an internal combustion engine according to the present embodiment has the outer shape shown in FIG. 22, and the plug cap 70 is mounted outside the coil portion 60a and the high-voltage terminal portion 60b. Via this plug cap 70, it is attached to an internal combustion engine (not shown) and connected to an ignition plug (not shown). When the primary current of the primary coil 12 is interrupted in this state, a counter electromotive force is induced in the secondary coil 22 to generate a high voltage of 30 to 40 kv, which is output to the ignition plug. As a result, spark discharge occurs in the electrode portion of each ignition plug, and the compressed air-fuel mixture in each combustion chamber (not shown) is ignited.

As described above, in the ignition coil for an internal combustion engine according to the present embodiment, it is possible to prevent a loose turn of the winding of the secondary coil and shorten the axial length while maintaining the desired ignition performance. it can. And the middle part 1 of the inner core 10
The entire cross section of Oa can be a magnetic circuit, and leakage of magnetic flux can be prevented by the enlarged portion 10b having a larger cross sectional area, and the effective magnetic flux density can be increased. Further, since the high-voltage side end 22h of the secondary coil 22 is formed by a single-layer winding wound around the cylindrical body 21b of the secondary bobbin 21, the inner core 10 on the high-voltage terminal 7 side is enlarged. The electric field concentration in the portion 10b is reduced. Thus, the entire device can be formed in a small size while maintaining a predetermined ignition performance.

[0037]

Since the present invention is configured as described above, the following effects can be obtained. That is, in the ignition coil for an internal combustion engine of the present invention, a secondary bobbin of a cylindrical body for winding the winding of the secondary coil is provided on the outer peripheral surface between the pair of flanges, and the secondary coil is provided between the pair of flanges. The inner surface of the flange on the winding start side at which winding of the winding starts is formed on an inclined surface inclined at a predetermined angle with respect to the axis of the secondary bobbin, and an annular groove is formed at a boundary between this inclined surface and the outer peripheral surface of the secondary bobbin. Because it is decided to form, without providing a large number of flanges, the winding of the secondary coil between the pair of flanges is securely wound to prevent loose turn, while maintaining the expected ignition performance A small ignition coil having a short axial length can be configured. In addition, the winding work of the secondary coil is easy, and good workability is obtained.

Further, if the guide groove extending from the annular groove to the outer periphery of the flange on the winding start side is formed on the inclined surface of the flange on the winding start side, the loose turn can be achieved. And the winding operation can be performed reliably, and the winding state can be maintained.

In the ignition coil for an internal combustion engine according to the third aspect, a portion of the secondary bobbin surrounding the end of the columnar member on the high voltage terminal side is formed into a cylindrical body having a large outer diameter. The portion surrounding the intermediate portion of the columnar member is formed in a cylindrical body having an outer diameter of a small diameter, and between a small-diameter cylindrical body and a large-diameter cylindrical body, a predetermined angle with respect to the axis of the secondary bobbin. Forming an annular groove at the boundary between the inclined surface and the outer peripheral surface of the secondary bobbin, and forming a guide groove extending from the annular groove to the outer periphery of the large-diameter cylindrical body on the inclined surface. After winding one layer of the secondary coil winding on the outer peripheral surface of the cylindrical body, the coil is guided to the annular groove through the guide groove, and the secondary coil winding is wound around the annular groove as a starting point, and a small diameter cylinder is formed. Since multiple layers are formed on the body, the winding of the secondary coil is securely wound by preventing loose turns It can axial length while maintaining the desired ignition performance constitutes a short compact ignition coil. In addition, by configuring the portion of the secondary coil surrounding the end of the columnar member on the high voltage terminal side with a single layer of winding, the distance between the portion and the inner core is increased, so that electric field concentration can be avoided. As a result, the electric insulation can be reliably maintained.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of an ignition coil for an internal combustion engine according to an embodiment of the present invention.

FIG. 2 is a vertical sectional view of an ignition coil for an internal combustion engine according to one embodiment of the present invention.

FIG. 3 is a partial sectional view of an ignition coil for an internal combustion engine according to one embodiment of the present invention.

FIG. 4 is a partial sectional view of an ignition coil for an internal combustion engine according to one embodiment of the present invention.

5 is a cross-sectional view of a coil portion of the ignition coil for an internal combustion engine according to one embodiment of the present invention, and is a cross-sectional view taken along line AA of FIG. 2;

6 is a cross-sectional view of a coil portion of the ignition coil for an internal combustion engine according to one embodiment of the present invention, and is a cross-sectional view taken along line BB of FIG. 2;

FIG. 7 is a cross-sectional view of a coil portion of the ignition coil for an internal combustion engine according to one embodiment of the present invention, and is a cross-sectional view taken along line CC of FIG. 2;

8 is a cross-sectional view of a coil portion of the ignition coil for an internal combustion engine according to one embodiment of the present invention, and is a cross-sectional view taken along line DD of FIG. 2;

9 is a cross-sectional view of a coil portion of the ignition coil for an internal combustion engine according to one embodiment of the present invention, which is a cross-sectional view taken along line EE of FIG. 2;

FIG. 10 is a cross-sectional view of a coil portion of the ignition coil for an internal combustion engine according to one embodiment of the present invention, and is a cross-sectional view taken along line FF of FIG. 2;

FIG. 11 is a plan view of an inner core according to an embodiment of the present invention.

FIG. 12 is a side view of the inner core according to the embodiment of the present invention.

FIG. 13 is a front view of the inner core according to the embodiment of the present invention.

FIG. 14 is a sectional view of an intermediate portion of the inner core according to one embodiment of the present invention.

FIG. 15 is a front view showing a state where a primary coil is wound around an inner core according to an embodiment of the present invention.

FIG. 16 is a plan view showing a state where a primary coil is wound around an inner core in one embodiment of the present invention.

FIG. 17 is a side view showing a state where a primary coil is wound around an inner core according to an embodiment of the present invention.

FIG. 18 is a side view of a secondary bobbin according to the embodiment of the present invention.

FIG. 19 is a front view showing a state where the primary coil assembly according to one embodiment of the present invention is assembled to a secondary coil assembly.

FIG. 20 is a cross-sectional view schematically illustrating a winding order of windings of a secondary coil according to the embodiment of the present invention.

FIG. 21 is a cross-sectional view schematically illustrating a winding state of a winding of a secondary coil in an ignition coil to be compared.

FIG. 22 is a perspective view of an ignition coil for an internal combustion engine according to one embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 8 igniter 10 inner core (columnar member) 10a intermediate part 10b enlarged part 11, 11a, 11b insulating coating 12 primary coil 13 insulating part 14 holder 15, 16 primary terminal 17, 18 secondary terminal 19 elastic layer 20 secondary coil assembly 21 Secondary bobbins 21a, 21b Cylindrical body 21g Guide groove 21j Annular groove 21p, 21q, 21s Collar 22 Secondary coil 30 Outer core 40 Auxiliary core 49, 49x Holder 50 Permanent magnet 60 Case

Claims (3)

[Claims] 1. An ignition coil for an internal combustion engine comprising a primary column and a secondary coil mounted on a columnar member of a magnetic material,
A secondary bobbin of a cylindrical body that has at least a pair of flanges formed so as to face each other at a predetermined distance and that winds the winding of the secondary coil on the outer peripheral surface between the pair of flanges. The inner bobbin of the secondary bobbin is provided with, among the inner surfaces of the pair of flanges opposing each other, the inner surface of the flange on the winding start side that starts winding the secondary coil between the pair of flanges. An ignition coil for an internal combustion engine, wherein the ignition coil is formed on an inclined surface inclined at a predetermined angle with respect to an axis, and an annular groove is formed at a boundary between the inclined surface and an outer peripheral surface of the secondary bobbin. 2. The internal combustion engine according to claim 1, wherein a guide groove extending from the annular groove to the outer periphery of the flange on the winding start side is formed on the inclined surface of the flange on the winding start side. Ignition coil. 3. A columnar member made of a magnetic material having an intermediate portion formed in a substantially circular cross section and both ends formed in a rectangular cross section, and a primary coil formed by winding a coil around the intermediate portion of the columnar member.
A secondary coil formed by winding a coil so as to surround the columnar member and the primary coil; and a high voltage terminal connected to an end of the secondary coil winding near one end of the columnar member. The secondary coil is formed by winding a winding around a secondary bobbin of a cylindrical body that houses the columnar member and the primary coil with a predetermined gap from both ends of the columnar member and the primary coil, Of the secondary bobbin, a portion surrounding the end of the columnar member on the high-voltage terminal side is formed into a large-diameter cylindrical body, and a portion surrounding the intermediate portion of the columnar member has a small outer diameter. And a slope inclined at a predetermined angle with respect to the axis of the secondary bobbin is formed between the small-diameter cylinder and the large-diameter cylinder, and the inclined surface and the secondary An annular groove is formed at the boundary with the outer peripheral surface of the bobbin. A guide groove extending from the annular groove to the outer periphery of the large-diameter cylindrical body is formed on the inclined surface, and a layer of the secondary coil is wound around the outer peripheral surface of the large-diameter cylindrical body. An ignition coil for an internal combustion engine, wherein the ignition coil is guided to the annular groove through a groove, and a plurality of layers are formed on the small-diameter cylindrical body by winding a winding of the secondary coil starting from the annular groove. .