JPH10340822A - Igniter for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make the electrical field strength of a center core uniform and to reduce the size of the core, and then, to improve the output and insulating property of the core, by providing a positioning section which performs the centering of the secondary coil bobbin of a center core. SOLUTION: Projections 30 are provided at several locations on the inside of a secondary bobbin 3 so as to position the planar section of an inserted center core 7 with the projections 30. The space factor of the bobbin 3 is increased against the inside diameter of the bobbin 3 by forming the cross section of the core 7 in a polygon which is made closer to a circle, and the core 7 is inserted into the bobbin 3 after molding the outer periphery of the core 7 with rubber. Since the core 7 can be formed in a cylindrical state when conductive rubber is used for molding the outer periphery of the core 7, the electric field impressed upon a secondary coil becomes uniform and the insulating property of an igniter can be improved. Since the center core 7 is provided with magnets 12 for generating magnetic fluxes in the direction opposite to that of magnetic fluxes generated from a primary coil 2 and minus magnetic fluxes are given to the core 7, the magnetization curve of the core 7 can be utilized from the negative side to the positive side and the output of the coil 2 can be increased.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ignition device for an internal combustion engine, and more particularly to a cylindrical ignition device housed in a plug hole.

[0002]

2. Description of the Related Art A conventional ignition device for an internal combustion engine is disclosed in
As in -70508, the components such as the primary coil wound on the primary bobbin, the secondary coil wound on the secondary bobbin, and the center core are arranged in this order from the inside in the order of center core, primary coil, secondary coil, and side core. They are arranged concentrically, and the centering structure of the center core is not particularly adopted.

[0003]

In the prior art, the center core is arranged inside the primary coil and the side core is arranged outside the secondary coil. Therefore, the electrostatic stray capacitance of the secondary coil is large and the secondary voltage is small. There were many losses. Further, since the secondary coil is disposed outside the center core and the primary coil, the resistance of the secondary coil is increased, and the loss of the secondary energy and the discharge duration is increased. Therefore, by arranging the components such as the primary coil, the secondary coil, the center core, and the side core concentrically from the inside in the order of the center core, the secondary coil, the primary coil, and the side core, the electrostatic stray capacitance of the secondary coil is reduced. Therefore, the loss of the secondary voltage can be reduced. In addition, the loss of the secondary energy and the discharge duration time is reduced by reducing the secondary coil resistance. Thus, a compact, lightweight, and high-output internal combustion engine ignition device can be obtained.

However, when the center core and the secondary coil are arranged from the inside, if the electric field intensity between the center core and the secondary coil is not made uniform, partial electric field concentration occurs and dielectric breakdown occurs.

Accordingly, it is an object of the present invention to provide a highly reliable ignition coil for an internal combustion engine while achieving a small size and high output.

[0006]

In order to achieve the above object, a positioning portion for centering a center core on a secondary coil bobbin is provided. Thereby, the electric field intensity could be made uniform.

[0007]

Embodiments of the present invention will be described below with reference to the drawings.

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

The primary bobbin 1 is made of polybutylene terephthalate (PBT) or polyphenylene oxide (modified PP).
O) or the like, and the primary coil 2 is wound. In addition, modified polyphenylene oxide (modified PPO), polyphenylene sulfide (PP
A secondary coil 4 is wound around a secondary bobbin 3 formed of a thermoplastic synthetic resin such as S).

[0010] Specifically, the primary coil 2
Is an enameled wire having a wire diameter of about 0.3 to 1.0 mm, several tens to one hundred and several tens times per layer, for a total of 100 to 30 over several layers.
The secondary coil 4 has a wire diameter of 0.0
5,000-total using enameled wire of about 3 to 0.1 mm
It is wound about 30,000 times.

The center core 7 is formed by pressing and laminating a silicon steel plate having a thickness of 0.2 to 0.7 mm, and is inserted inside the secondary bobbin 3. The cross-sectional shape of the center core 7 is a polygonal shape close to a circle, and the space factor with respect to the inner diameter of the secondary bobbin 3 is improved.

Between the center core 7 and the secondary bobbin 3,
An elastic insulating material such as a flexible epoxy resin 16 or silicone rubber is filled.

At one end or both ends of the center core 7, a magnet 12 for generating a magnetic flux in a direction opposite to the magnetic flux generated in the primary coil 2 is provided. Magnet 1
Since the magnetic flux due to 2 gives a negative magnetic flux to the center core, it can be used from the negative side of the magnetization curve of the core to the positive side, so the result is the same as using a core material with an apparently high saturation magnetic flux density. Higher coil output can be expected.

An elastic body such as rubber is provided on the outside of the center core 7 or the magnet 12. The high pressure side is between the secondary bobbin 3 and the magnet 12, and the low pressure side is the magnet 12. It is arranged between the insulating epoxy resins 6. Thus, a structure is adopted in which the thermal strain in the axial direction is absorbed by the elastic body. For this reason, closed-cell rubber whose volume can be changed is suitable as the elastic body.

The side core 8 is formed by rolling a silicon steel plate having a thickness of 0.2 to 0.7 mm into a tube and stacking one to three sheets. However, in order to prevent one-turn short-circuit of the magnetic flux, at least one location on the circumference of the side core 8 is provided with a cut.

The case 5 is formed of the same thermoplastic synthetic resin as the primary bobbin 1 and includes a cylindrical portion 25 and a connector portion 24. Therefore, when a different type of connector is required, it can be dealt with only by changing the connector portion, and the tubular portion 25 can be shared.

These components are, in order, the center core 7, the secondary coil 4, the primary coil 2, the case 5, and the side core 8 from the inside, or the center core 7, the secondary coil 4, the primary coil 2, the side core 8, and the like from the inside. Case 5 is arranged concentrically.

Then, these coil component parts are pressed into the case 5 and filled with a filling insulating material such as an insulating epoxy resin 6 for insulating high voltage. The insulating epoxy resin 6 has a glass transition temperature Tg after curing of 120 ° C. to 1 ° C.
62 ° C. and a coefficient of thermal expansion of 10 to 50 × 10 to ⁶ ° C. as an average value in a temperature range not higher than the glass transition temperature Tg.
For example, a material having a characteristic of about 25 × 10 to ⁶ ° C. is used. By using such an epoxy resin for insulation having a high glass transition temperature Tg, the electrical insulation characteristics at high temperatures are further stabilized.

The high voltage generated in the secondary coil 4 causes the premature ignition preventing high-voltage diode 17, which is arranged in a direction perpendicular to the longitudinal direction so as to reduce the length of the ignition device as much as possible.
The ignition plug 10 is connected via the high voltage terminal 13 and the spring 14.
Supplied to The part where the spark plug 10 is inserted is insulated by a rubber boot 15 such as silicon rubber. A seal rubber 9 that seals the plug hole 11 is provided at a portion in contact with the cylinder head cover 22. The igniter unit 20 installed on the upper part of the coil has a power transistor chip and a hybrid IC circuit built in a metal base 21 made of copper or aluminum pressed into a box shape. Gel is filled.

Next, the present invention will be described in detail with reference to the sectional view of the secondary bobbin shown in FIG.

Several protrusions 30 are provided inside the secondary bobbin 3. The tip of the projection 30 has a semicircular shape in order to reduce the contact area with the center core.
And the secondary bobbin 3 does not affect each other. The state when the center core 7 is inserted is as shown in FIG. 3. In this case, the plane portion of the center core 7 is positioned by the projection 30. As shown in FIG. 4, the length of the centering projection 30 is set to be at least 1/3 of the length of the center core from the high pressure side of the secondary bobbin 3. This achieves both prevention of the inclination of the center core 7 and improvement of the impregnation of the flexible epoxy resin 16 to be filled in order to eliminate the gap between the secondary bobbin 3 and the center core 7. FIG. 5 shows an embodiment in which the projection 30 is set not to be positioned on the plane portion of the center core 7 but to be located in the concave portion of the center core 7. Even when the cross-sectional shape of the center core 7 is almost circular, centering can be performed by providing the projections 30 at several places inside the secondary bobbin 3. FIG. 6 shows the centering structure shown in FIG.
In order to prevent erroneous insertion, such as the center core 7 being inserted obliquely, the periphery of the projection 30 (the hatched portion in the figure) is also provided with a resin wall.

As another method of centering, there is a method of applying taping 31 to a part of the center core 7 as shown in FIG. In this case, taping 3
If the step (1) is performed, the flexible epoxy resin 16 to be filled in order to eliminate the gap between the secondary bobbin 3 and the center core 7 is blocked at the upper part and impregnating property is deteriorated. . In addition, a non-woven fabric tape is used so that the flexible epoxy resin 16 is easily impregnated.

As another method of centering, as shown in FIG. 8, there is a method in which the outer periphery of the center core 7 is previously rubber-molded 32 and inserted into the secondary bobbin 3. This method uses a flexible epoxy resin 1 filled to eliminate a gap between the secondary bobbin 3 and the center core 7.
6 can be omitted. Then, by making the rubber material to be molded conductive, it becomes the same as that of the center core 7 having a columnar shape, so that the electric field to the secondary coil 4 becomes uniform, and an improvement in insulation can be expected.

[0024]

According to the present invention, it is possible to provide an ignition device for an internal heat engine which is compact, has a high output, and is excellent in reliability, especially in insulation performance.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a configuration of an ignition device for an internal combustion engine according to one embodiment of the present invention.

FIG. 2 is an enlarged sectional view of the embodiment of FIG.

FIG. 3 is an enlarged sectional view of the embodiment of FIG. 1;

FIG. 4 is an enlarged sectional view in the axial direction of the embodiment of FIG. 1;

FIG. 5 is a partially enlarged view showing an embodiment of the embodiment shown in FIG. 2 when the projection position is changed.

FIG. 6 is an enlarged sectional view of the embodiment of FIG. 1;

FIG. 7 is a view showing another embodiment of the centering method.

FIG. 8 is a diagram showing another embodiment of the centering method.

[Explanation of symbols]

1: primary bobbin, 2: primary coil, 3: secondary bobbin, 4
... secondary coil, 5 ... case, 6 ... epoxy resin for insulation,
7 center core, 8 side core, 9 plug hole seal, 10 spark plug, 11 plug hole, 12
Magnet, 13 ... High voltage terminal, 14 ... Spring, 15
... rubber boots, 16 ... flexible epoxy resin, 17 ... high voltage diode for preventing premature ignition, 18 ... foamed rubber, 19 ...
Air layer, 20 igniter unit, 21 base, 2
2 ... Cylinder head cover, 24 ... Connector, 25 ...
Cylindrical part, 30 ... projection, 31 ... taping, 32 ... rubber mold.

Claims (10)

[Claims] 1. A cylindrical ignition device directly connected to an ignition plug and housed in a plug hole, wherein a primary coil wound on a primary bobbin, a secondary coil wound on a secondary bobbin,
The components such as the center core are arranged concentrically from the inside in the order of the center core, the secondary coil, and the primary coil, and the components are housed in a case molded in advance with a thermoplastic synthetic resin. A thermosetting synthetic resin is filled around the component, a side core is further arranged outside the primary coil, an insulating material is filled between the center core and the secondary bobbin, and elastic bodies are arranged at both ends of the center core. The ignition device for an internal combustion engine according to claim 1, wherein the center core is provided with a centering positioning portion with respect to the secondary coil. 2. The ignition device for an internal combustion engine according to claim 1, wherein centering of the center core is performed by a secondary bobbin for winding and fixing a secondary coil. 3. An ignition device for an internal combustion engine according to claim 2, wherein the center core is centered by providing several projections inside the secondary bobbin. 4. The ignition device for an internal combustion engine according to claim 3, wherein the protrusion inside the secondary bobbin has a semicircular tip. 5. The ignition device for an internal combustion engine according to claim 3, wherein the length L1 of the projection inside the secondary bobbin is not less than 1/3 of the length L2 of the center core. 6. The ignition device for an internal combustion engine according to claim 1, wherein the centering of the secondary bobbin is performed by winding a tape around the center core. 7. The ignition device for an internal combustion engine according to claim 6, wherein the centering tape is wound around only the high pressure side of the center core. 8. The ignition device for an internal combustion engine according to claim 6, wherein the centering tape is a fibrous nonwoven fabric tape. 9. The ignition device for an internal combustion engine according to claim 1, wherein the center core is centered by rubber molding. 10. The ignition device for an internal combustion engine according to claim 9, wherein the rubber to be molded is a conductive rubber.