JP2004312047A - Ignition system for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a small-sized and high-output ignition system for an internal combustion engine that is superior in insulation performance. <P>SOLUTION: Components, such as a primary coil 2, a secondary coil 4, a center core 7 and a side core 8 and the like are arranged concentrically in the order of the center core 7, the secondary coil 4, the primary coil 2 and the side core 8, etc., starting from the inner side, and a locating means is provided that centers the center core 7 between a secondary bobbin 3 and the center core 7. Thus, a small-sized and high-output ignition system for an internal combustion engine that is superior in insulation performance can be provided. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  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.

  A conventional ignition device for an internal combustion engine includes a primary coil wound on a primary bobbin, a secondary coil wound on a secondary bobbin, a center core, and other components as disclosed in JP-A-63-70508. , The center core, the primary coil, the secondary coil, and the side core are arranged concentrically in this order.

JP-A-63-70508

  In the prior art, since the center core is disposed inside the primary coil and the side core is disposed outside the secondary coil, the secondary coil has a large electrostatic stray capacitance and a large secondary voltage loss. Further, since the secondary coil is disposed outside the center core and the primary coil, the secondary coil resistance 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 provided.

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

  In order to achieve the above object, as a means for centering the center core with respect to the secondary coil bobbin, the center core is rubber-molded to perform centering with respect to the secondary bobbin.

  As a result, the electric field intensity can be made uniform, and a small, high-output, highly reliable ignition coil for an internal combustion engine can be obtained.

  Hereinafter, embodiments of the present invention will be described 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 one embodiment of the present invention.

  The primary bobbin 1 is formed of a thermoplastic synthetic resin such as polybutylene terephthalate (PBT) or polyphenylene oxide (modified PPO), and has a primary coil 2 wound thereon. A secondary coil 4 is wound around a secondary bobbin 3 formed of a thermoplastic synthetic resin such as modified polyphenylene oxide (modified PPO) and polyphenylene sulfide (PPS).

To be specific, the primary coil 2 is formed by laminating an enamel 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 about 100 to 300 times over several layers. The secondary coil 4 uses an enameled wire having a wire diameter of about 0.03 to 0.1 mm and has a total of 5,000 to
It is wound about 30,000 times.

  The center core 7 is formed by press-stacking 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.

  The space between the center core 7 and the secondary bobbin 3 is filled with an elastic insulating material such as a flexible epoxy resin 16 or silicone rubber.

  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 by the primary coil 2 is provided. Since the magnetic flux by the magnet 12 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 that the same result as when a core material having an apparently high saturation magnetic flux density is used is obtained. In addition, high output of the coil can be expected.

  An elastic body such as rubber is provided outside 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 and an insulating epoxy. It is arranged between the resins 6. Thus, the elastic body absorbs the thermal strain in the axial direction. For this reason, a 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 sheet 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 place 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 case 5 from the inside. They are arranged concentrically in order.

Then, these coil component parts are press-fitted 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 162 ° C. and a coefficient of thermal expansion of 10 to 50 × 10 ^{6 to 6} ° C. as an average value in a temperature range of the glass transition temperature Tg or less. Of the degree, for example, 25 ×
Use a material having a characteristic of about 10 to ⁶ ° C. 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 passes through a premature ignition preventing high voltage diode 17, a high voltage terminal 13, and a spring 14, which are arranged in a direction perpendicular to the longitudinal direction so as to reduce the length of the ignition device as much as possible. And supplied to the ignition plug 10. 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, so that the influence of thermal strain generated between the center core 7 and the secondary bobbin 3 is not exerted on each other. The state when the center core 7 is inserted is as shown in FIG. 3. In this case, the flat 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. As a result, the inclination of the center core 7 is prevented, and the 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 is achieved. FIG. 5 shows an embodiment in which the projection 30 is set so as to be positioned in the concave portion of the center core 7 instead of being positioned on the plane portion of the center core 7. Even when the cross-sectional shape of the center core 7 is nearly circular, centering can be performed by providing the projections 30 at several locations inside the secondary bobbin 3. 6, in the centering structure shown in FIG. 3, in order to prevent erroneous insertion such as oblique insertion of the center core 7, resin around the protrusion 30 (hatched portion in the drawing) is also provided.

  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, if the taping 31 is applied to the upper side of the center core 7, 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 side, and impregnation becomes poor. The taping 31 is wound only on the lower side of the center core 7. A non-woven tape is used for the tape 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. According to this method, the step of injecting the flexible epoxy resin 16 to be filled in order to eliminate the gap between the secondary bobbin 3 and the center core 7 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.

  A conventional ignition device for an internal combustion engine includes a primary coil wound on a primary bobbin, a secondary coil wound on a secondary bobbin, a center core, and other components as disclosed in JP-A-63-70508. , A center core, a primary coil, a secondary coil, and a side core are arranged concentrically in this order, and in particular, the centering structure of the center core has not been adopted.

  In the prior art, since the center core is disposed inside the primary coil and the side core is disposed outside the secondary coil, the secondary coil has a large electrostatic stray capacitance and a large secondary voltage loss. Further, since the secondary coil is disposed outside the center core and the primary coil, the secondary coil resistance 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 provided.

  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.

  On the other hand, in the above-described embodiment, it is possible to provide an ignition coil for an internal combustion engine which is excellent in reliability while achieving downsizing and high output.

  In the above embodiment, the positioning portion for centering the center core with respect to the secondary coil bobbin is provided. Thereby, the electric field intensity could be made uniform.

Embodiment 1
In a cylindrical ignition device directly connected to an ignition plug and housed in a plug hole, components such as a primary coil wound around a primary bobbin, a secondary coil wound around a secondary bobbin, a center core, etc. A center core, a secondary coil, and a primary coil are concentrically arranged in this order, and the components are housed in a case molded in advance of a thermoplastic synthetic resin, and a thermoset is provided around the components in the case. In an ignition device for an internal combustion engine, a side core is arranged outside a primary coil, an insulating material is filled between a center core and a secondary bobbin, and elastic bodies are arranged at both ends of the center core. Characterized in that a centering positioning portion is provided for the secondary coil.

Embodiment 2
The ignition device for an internal combustion engine according to the first embodiment, wherein centering of the center core is performed by a secondary bobbin for winding and fixing a secondary coil.

Embodiment 3
An ignition device for an internal combustion engine according to a second embodiment, wherein centering of the center core is performed by providing several projections inside the secondary bobbin.

Embodiment 4
The ignition device for an internal combustion engine according to a third embodiment, wherein the protrusion on the inner side of the secondary bobbin has a semicircular end.

Embodiment 5
The ignition device for an internal combustion engine according to a third embodiment, wherein the length L1 of the protrusion inside the secondary bobbin is equal to or more than ３ of the length L2 of the center core.

Embodiment 6
The ignition device for an internal combustion engine according to the first embodiment, wherein centering of the secondary bobbin is performed by winding a tape around the center core.

Embodiment 7
An ignition device for an internal combustion engine according to a sixth embodiment, wherein the centering tape is wound around only the high pressure side of the center core.

Embodiment 8
The ignition device for an internal combustion engine according to embodiment 6, wherein the centering tape is a fibrous nonwoven fabric tape.

Embodiment 9
The ignition device for an internal combustion engine according to the first embodiment, wherein the center core is centered by rubber molding.

Embodiment 10
The igniter for an internal combustion engine according to embodiment 9, wherein the rubber to be molded is a conductive rubber.

  According to the embodiment described above, it is possible to provide an ignition device for an internal heat engine that is small, has high output, and is excellent in reliability, particularly, excellent insulation performance.

1 is a cross-sectional view illustrating a configuration of an internal combustion engine ignition device according to an embodiment of the present invention. FIG. 2 is an enlarged cross-sectional view of the embodiment of FIG. 1. FIG. 2 is an enlarged cross-sectional view of the embodiment of FIG. 1. FIG. 2 is an enlarged cross-sectional view in the axial direction of the embodiment of FIG. 1. FIG. 3 is a partially enlarged view showing an embodiment of the embodiment shown in FIG. 2 when the projection position is changed. FIG. 2 is an enlarged cross-sectional view of the embodiment of FIG. 1. FIG. 9 is a diagram showing another embodiment of the centering method. FIG. 9 is a diagram showing another embodiment of the centering method.

Explanation of reference numerals

DESCRIPTION OF SYMBOLS 1 ... Primary bobbin, 2 ... Primary coil, 3 ... Secondary bobbin, 4 ... Secondary coil, 5 ... Case, 6 ... Insulating epoxy resin, 7 ... Center core, 8 ... Side core, 9 ... Plug hole seal,
DESCRIPTION OF SYMBOLS 10 ... Ignition plug, 11 ... Plug hole, 12 ... Magnet, 13 ... High voltage terminal, 14 ... Spring, 15 ... Rubber boot, 16 ... Flexible epoxy resin, 17 ... Premature ignition prevention high voltage diode, 18 ... Foam rubber 19 ... air layer, 20 ... igniter unit, 21 ... base, 22 ... cylinder head cover, 24 ... connector part, 25 ... cylinder part, 30 ... protrusion, 31 ... taping, 32 ... rubber mold.

Claims (4)

A cylindrical ignition device for an internal combustion engine housed in a plug hole for mounting an ignition plug, comprising components such as a primary coil wound around a primary bobbin, a secondary coil wound around a secondary bobbin, and a center core. Is housed in a case molded from the center core insulating resin from the inside,
A cylindrical ignition device for an internal combustion engine, wherein an outer periphery of the center core is rubber-molded. The cylindrical ignition device for an internal combustion engine according to claim 1,
A cylindrical ignition device for an internal combustion engine, comprising a magnet at one or both ends of a center core for generating a magnetic flux in a direction opposite to a magnetic flux generated by a primary coil. The cylindrical ignition device for an internal combustion engine according to claim 2,
An ignition device for an internal combustion engine, wherein an elastic body is provided outside the magnet at a low-pressure end of the center core. The cylindrical ignition device for an internal combustion engine according to claim 3,
An ignition device for an internal combustion engine, wherein an insulating epoxy resin is filled outside the elastic body.

Images