JP2000049024A - Ignition coil for internal combustion engine and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an ignition coil for internal combustion engine having high electric insulating ability. SOLUTION: An ignition coil for internal combustion engine is of an inner secondary coil type, in which a secondary coil bobbin 14 is positioned in a primary coil bobbin 16, and a center core 11 is put in the secondary coil bobbin 14. The surface of the center core 11 is coated with a high elasticity high- polymer insulating resin 131. The resin 131 is also filled in the clearance between the laminated cores 111 of the center core 11. Between the center core 11 and a secondary coil bobbin 14, two layers of the high elasticity high-polymer insulating resin 131 and a coil insulating resin 20 are formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an ignition coil for an internal combustion engine, and more particularly, to an ignition coil for an internal combustion engine that can be housed in a plug hole of an engine.

[0002]

2. Description of the Related Art JP-A-8-64438 discloses a resin-molded ignition coil in which a primary winding is wound on a surface of an iron core without a bobbin, in order to reduce the thermal resistance between the primary winding and the iron core.
A resin-molded ignition coil in which the surface of an iron core is covered with an electrically insulating film or an insulating film having good thermal conductivity is described.

[0003] As an internal combustion engine ignition coil housed in a plug hole of an engine, there is an internal secondary coil type internal combustion engine ignition coil in which a secondary coil is arranged inside a primary coil. In the inner secondary coil system, the center core has a floating potential, and a potential difference occurs between the secondary coil and the center core, which are high potential, but the potential difference is reduced to about half compared to the outer secondary coil type ignition coil. Can be. Then, the gap between the center core and the secondary bobbin is filled with an insulating resin.

Japanese Patent Application Laid-Open No. Hei 10-22144 describes that a gap between the center core and the secondary bobbin is filled with a flexible epoxy resin in order to reduce stress concentration due to thermal stress near the center core. .

[0005]

However, in a conventional ignition coil for an internal combustion engine of the inner secondary coil system, the gap between the center core and the secondary bobbin is filled with a flexible epoxy resin. Stress concentration due to thermal stress near the center core can be reduced. However, since the center core is formed by laminating 20 to 30 thin silicon steel sheets, the center core is arranged in the secondary bobbin between the center core and the secondary bobbin as in the related art. When the insulating resin is filled, the gas (air) between the silicon steel sheets is hardly removed and remains in the center core. This residual gas may form voids, causing partial discharge, which may impair the electrical insulation performance of the ignition coil.

An object of the present invention is to provide an ignition coil for an internal combustion engine having good electric insulation performance.

[0007]

A feature of the present invention that achieves the above object is that a first insulating resin contacts and surrounds a center core between a secondary coil bobbin and a center core,
The second insulating resin is in contact with and surrounds the first insulating resin.

According to this feature, since the periphery of the center core is covered with the first insulating resin, even if gas remains inside the center core, the first insulating resin removes the residual gas in the center core. Since it is prevented from coming out, generation of a void between the center core and the secondary coil bobbin can be suppressed, and partial discharge due to the void can be prevented. Therefore, it is possible to obtain an ignition coil for an internal combustion engine with further improved electric insulation performance.

Further, if the first insulating resin portion is a highly elastic polymer insulating resin or a flexible resin, the concentration of thermal stress near the center core can be reduced, and the durability of the ignition coil for an internal combustion engine against vibration and impact can be reduced. Properties can be further improved.

Another feature of the present invention is that the center core is impregnated with the first insulating resin, or the center core is molded with the first insulating resin, and then the center core is disposed inside the secondary coil bobbin. And filling the second insulating resin between the first insulating resin and the secondary coil bobbin.

According to this feature, since the center core is impregnated with the first insulating resin or the center core is molded with the first insulating resin, the gas inside the center core is easily removed, and the second core is removed. The insulating resin is composed of the first insulating resin and 2
When the space between the center coil and the next coil bobbin is filled, the amount of gas flowing out of the center core into the second insulating resin is reduced. Therefore, generation of voids in the second insulating resin can be prevented, partial discharge does not occur between the center core and the secondary coil, and the electrical insulation performance of the ignition coil can be further improved.

[0012]

(Embodiment 1) An ignition coil 10 according to an embodiment of the present invention will be described. FIG. 1 shows a cross section in the radial direction of the ignition coil 10 of the present embodiment.

The ignition coil 10 of this embodiment is an ignition coil for an internal combustion engine of an internal secondary coil system in which a secondary coil bobbin 14 is disposed inside a primary coil bobbin 16 and a center core 11 is disposed inside the secondary coil bobbin 14. It is. 1
A primary coil 17 is wound around the secondary coil bobbin 16. The secondary coil 15 has 10 secondary coils 15.
It is wound 3,000 to 30,000 turns. The coil insulating resin 2 is provided between the coil case 19 and the primary coil 17 and between the primary coil bobbin 16 and the secondary coil 15.
0 is filled.

The center core 11 is formed by stacking thin silicon steel sheets having a thickness of about 0.3 mm and stacking them (each of a plurality of flat plates has a concave portion formed on one surface during press molding and a convex portion formed on the other surface). Are formed, and the plurality of flat plates are successively overlapped while press-fitting the convex portions of the surfaces facing each other into the concave portions to form a laminate. So that the cross section of the center core 11 is substantially circular,
The silicon steel plate of the center core 11 is pressed while changing its width. The surface of the center core 11 is made of a high elastic polymer insulating resin 1
31. The high elastic polymer insulating resin 131 is
The space between the laminated cores 111 of the center core 11 is also filled.

FIG. 2 shows a center core 11 and a permanent magnet 12.
1 shows a vertical cross section of FIG. Permanent magnets 12 are arranged at both ends of the center core 11 in the longitudinal direction. The high elastic polymer insulating resin 131 also covers the surface of the permanent magnet 12. FIG.
2 shows a cross section taken along line A1-A2 in FIG.

A method for manufacturing an ignition coil for an internal combustion engine according to this embodiment will be described.

First, a product in which the center core 11 and the permanent magnet 12 are integrated with a high elastic polymer insulating resin 131 is prepared. A permanent magnet 1 is provided at each end of the center core 11.
2 is immersed in the high elastic polymer insulating resin 131 under a reduced pressure for a predetermined time. Then, it is taken out to the atmosphere and cured by heating. In this embodiment, the high elastic polymer insulating resin 1
31 is a flexible epoxy resin (XN1 manufactured by Nagase Ciba)
019 (N)). The conditions for dipping the center core 11 and the permanent magnet 12 in the high elastic polymer insulating resin 131 in this embodiment are as follows: temperature: 60 ° C., degree of vacuum: 5 to 10 torr.
r, immersion time: 10 minutes, heat curing conditions in air: 120
C. for 1 hour.

Next, the igniter 1 is placed in the coil case 19.
8 and the high voltage terminal 23 are arranged in advance. In the secondary coil bobbin 14 around which the secondary coil 15 is wound, the center core 11 and the permanent magnet 12 integrated with the high elastic polymer insulating resin 131 are arranged. Center core 11 and permanent magnet 1
2 is placed inside the primary coil bobbin 16 and placed in the coil case 19. Then, each component in the coil case 19 is connected.

Finally, the coil insulating resin 20 is filled in the coil case 19 from the igniter 18 side under reduced pressure. The coil insulating resin 20 is made of a high elastic polymer insulating resin 13
The space between the primary coil and the secondary coil bobbin 14 and the space between the secondary coil 15 and the primary coil bobbin 16 are filled. Therefore, between the center core 11 and the secondary coil bobbin 14, two layers of the high elastic polymer insulating resin 131 and the coil insulating resin 20 are formed. FIG. 4 shows a state in which two insulating resin layers are formed between the center core 11 and the secondary coil bobbin 14.

FIG. 5 shows a cross section of the ignition coil 10 of this embodiment in the coil axis direction. The magnetic circuit of the ignition coil 10 is formed by a center core 11, a permanent magnet 12, and a side core 21. A closed cell rubber 26 is disposed below the secondary coil bobbin 14 to suppress stress concentration near the tip of the permanent magnet 12. Coil case 19
A high-voltage connection spring 22, a high-voltage terminal 23, and a plug connection spring 27 are arranged below the, and guide the generated high voltage to an ignition plug (not shown). The portion where the spark plug is inserted is insulated by a rubber boot 25.

The ignition coil 10 is an internal combustion engine (not shown)
And connected to a spark plug. Igniter 18
When the primary current of the primary coil 17 is interrupted by the above operation, a high voltage of 30 kV to 40 kV is generated in the secondary coil 15 and output to the ignition plug. Spark discharge occurs in the electrode portion of the spark plug, and the compressed air-fuel mixture in the combustion chamber (not shown) is ignited.

In this embodiment, the center core 11 and the permanent magnet 12 are immersed in the first high elastic polymer insulating resin 131 to be integrated. However, the center core 11 and the permanent magnets 12 may be arranged in a cylindrical mold slightly larger than the diameter of the center core 11, and may be integrated by molding with a high elastic polymer insulating resin 131.

According to the ignition coil for an internal combustion engine of the present embodiment, the gap between the laminated cores 111 is filled with the high elastic polymer insulating resin 131 so that the gas between the laminated cores 111 can be removed. When the coil insulating resin 20 is filled in the coil container 19, the insulating resin 2
The generation of voids during zero can be prevented.

Further, since the surface of the center core 11 is covered with the high elastic polymer insulating resin 131, even if gas remains inside the center core, the high elastic polymer insulating resin 131 can be used. Since the residual gas is prevented from flowing out into the coil insulating resin 20, the generation of voids in the coil insulating resin 20 can be prevented. In addition, the high elastic polymer insulating resin 132 covering the surface of the center core 11 can reduce the concentration of thermal stress generated in the vicinity of the center core 11 and further improve the durability of the ignition coil for the internal combustion engine against vibration and impact. it can.

Therefore, a highly reliable ignition coil for an internal combustion engine having excellent electric insulation performance and excellent durability against vibration and impact was obtained.

(Embodiment 2) An ignition coil according to a second embodiment of the present invention will be described. FIG. 6 shows a radially enlarged cross section near the secondary coil bobbin 14 of the ignition coil of the present embodiment. Between the center core 11 and the secondary coil bobbin 14, there are two high-elastic polymer insulating resins 131 and 132.

In the first embodiment, the secondary coil bobbin 14 in which the center core 11 and the permanent magnet 12 are accommodated is disposed in the coil case 19, and then the high-elastic polymer insulating resin 131 and the secondary coil bobbin 14 And the coil insulating resin 20 was filled. However, in the present embodiment, before the secondary coil bobbin 14 is disposed in the coil case 19, the center core 11, the permanent magnet 12, and the secondary coil bobbin 14 are integrated in advance.

First, as in the first embodiment, the center core 11 and the permanent magnet 12 are separated from each other by a high elastic polymer insulating resin 13.
Integrate with 1. After that, the center core 11 and the permanent magnet 12 are put inside the secondary coil bobbin 14, and the space between the high elastic polymer insulating resin 131 and the secondary coil bobbin 14 is filled with the high elastic polymer insulating resin 132 under reduced pressure. Then, the integrated center core 11, the permanent magnet 12, and the secondary coil bobbin 14 are arranged together with the primary coil bobbin 16 in the coil case 19, and the respective components are connected in the same manner as in the first embodiment. In coil insulation resin 20
Fill.

According to the ignition coil of this embodiment, the same operation and effect as those of the ignition coil of the first embodiment can be obtained.
Since the two layers of the high elastic polymer insulating resin 131 and the high elastic polymer insulating resin 132 are made of the high elastic polymer insulating resin around the center core, the concentration of the thermal stress generated near the center core can be reduced in the first embodiment. It can be more relaxed than the ignition coil, and the durability against vibration and impact can be further improved.

In the first and second embodiments, a flexible epoxy resin is used as the high elastic polymer insulating resin.
The same effect can be obtained by using a silicone resin. Also,
By pre-treating the center core 11 and the permanent magnet 12 with a coupling agent such as silane before forming the high elastic polymer insulating resin 131, the high elastic polymer insulating resin 131 can be used between the lamination of the center core 11 and Since it can be reliably formed on the outer surface, the electrical insulation performance of the ignition coil can be further improved.

[0031]

According to the present invention, since the periphery of the center core is covered with the first insulating resin, even if a gas remains inside the center core, the first insulating resin remains in the center core. Center core and 2
Generation of voids between the next coil bobbins can be suppressed, and partial discharge due to voids can be prevented.
Therefore, it is possible to obtain an ignition coil for an internal combustion engine with further improved electric insulation performance.

If the first insulating resin portion is a high elastic polymer insulating resin or a flexible resin, the concentration of thermal stress near the center core can be reduced, and the durability of the ignition coil for the internal combustion engine against vibration and impact can be reduced. Properties can be further improved.

Further, since the center core is impregnated with the first insulating resin or the center core is molded with the first insulating resin, the gas inside the center core is easily removed, and the second insulating resin becomes the second insulating resin. When the space between the first insulating resin and the secondary coil bobbin is filled, the amount of gas flowing out of the center core into the second insulating resin is reduced. Therefore, generation of voids in the second insulating resin can be prevented, partial discharge does not occur between the center core and the secondary coil, and the electrical insulation performance of the ignition coil can be further improved.

[Brief description of the drawings]

FIG. 1 shows an ignition coil 10 according to a first embodiment of the present invention.
The figure which shows the cross section of the radial direction of.

FIG. 2 is a view showing a longitudinal section of a center core 11 and a permanent magnet 12.

FIG. 3 is a diagram showing a cross section taken along line A1-A2 of FIG. 2;

FIG. 4 is a diagram showing a radial cross section of the center core 11 and the secondary coil bobbin 14.

FIG. 5 is a diagram showing a cross section of the ignition coil 10 in a coil axis direction.

FIG. 6 is a diagram showing a radial cross section of a secondary coil bobbin 14 of an ignition coil according to a second embodiment.

[Explanation of symbols]

Reference numeral 10: ignition coil, 11: center core, 12: permanent magnet, 14: secondary coil bobbin, 15: secondary coil, 16
... primary coil bobbin, 17 ... primary coil, 18 ... igniter, 19 ... coil case, 20 ... coil insulating resin, 2
DESCRIPTION OF SYMBOLS 1 ... Side core, 22 ... High voltage connection spring, 23 ... High voltage terminal, 24 ... Plug connection spring, 25 ... Rubber boot,
26: closed-cell rubber, 111: laminated core, 131, 13
2: High elastic polymer insulating resin.

Claims (4)

[Claims] An annular primary coil bobbin on which a primary coil is wound; an annular secondary coil bobbin on which a secondary coil is wound and disposed inside the primary coil bobbin; An ignition coil for an internal combustion engine including a center core disposed inside, wherein a first insulating resin that is in contact with and surrounds the center core between the secondary coil bobbin and the center core; An ignition coil for an internal combustion engine, comprising: a second insulating resin in contact with and surrounding. 2. The ignition coil according to claim 1, wherein the first insulating resin is a high elastic polymer insulating resin. 3. The ignition coil for an internal combustion engine according to claim 1, wherein said first insulating resin is a flexible epoxy resin. 4. An annular primary coil bobbin on which a primary coil is wound, an annular secondary coil bobbin on which a secondary coil is wound and disposed inside the primary coil bobbin, A method of manufacturing an ignition coil for an internal combustion engine, comprising: a center core disposed inside; impregnating the center core with a first insulating resin, or molding the center core with a first insulating resin; Disposing the center core impregnated in a first insulating resin or molded with the first insulating resin inside the secondary coil bobbin; and the first insulating resin and the secondary coil bobbin. Filling a second insulating resin between the two.