JPH0997726A - Ignition coil - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to suppress the generation of the Joule heat of a primary coil to a certain degree so as to be able to increase the stored energy of the primary coil by making high a primary current. SOLUTION: An ignition coil is constituted of a coil main body part 10 and a case 20 for houding this main body part 10 and the coil main body part 10 is constituted of a magnetic core 11 formed by laminating electrical sheets and primary and secondary coils 12 and 15, which are mounted on this magnetic core 11 into a concentric shape. The coil 12 is one obtained by a method, wherein a 25-μm thick copper foil 14 obtainable by backing a 20-μm thick insulative film, which is formed of a polyethylene terephtalate, a polyether imide or a polyimicle, is cut in a width of 1.5cm and this cut copper foil is wound on a primary coil bobbin 13 100 to, 150 times, and lead wires are respectively led out from the winding start and winding end parts of the copper foil 14.

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 independent ignition system used in an internal combustion engine.

[0002]

2. Description of the Related Art An ignition coil for an internal combustion engine basically has a primary coil and a secondary coil formed by winding a magnet wire such as an enameled wire around a magnetic core. By intermittently passing a current through the primary coil side, a high voltage is generated on the secondary coil side to ignite the spark plug.

By the way, in order to fully exhibit the performance of the ignition coil, the energy stored in the primary coil U (= 1/2)
LI ² , L: inductance, I: primary current) must be sufficiently secured, but as can be seen from the above equation, 1
In order to increase the stored energy U of the secondary coil, it is necessary to increase the inductance L or the primary current I.

Since the inductance L is proportional to the square of the number of turns of the magnet wire, in order to increase the stored energy U by increasing the inductance L, the number of turns of the magnet wire must be increased. In the coil, a relatively thin magnet wire with a diameter of 0.4 to 0.6 mm was wound around a hundred and a dozen times, but an automatic winding machine is indispensable for winding a hundred and a dozen times in this way. There was a problem that equipment costs increased.

On the other hand, if an attempt is made to increase the stored energy U of the primary coil by increasing the primary current I, the loss due to Joule heat generation increases because the wire diameter of the magnet wire used is small. Since it is necessary to consider removal of the heat generation, it can be said that increasing the stored current U by increasing the primary current I has a structural limit in this type of ignition coil.

Therefore, an object of the present invention is to provide an ignition coil capable of suppressing Joule heat generation of the primary coil to some extent so that the energy stored in the primary coil can be increased by increasing the primary current. To provide.

[0007]

In order to solve the above problems, the present invention provides an ignition coil comprising a magnetic core and a primary coil and a secondary coil formed on the magnetic core, wherein the primary coil is It is formed by winding a metal conductor foil lined with an insulating film around the magnetic core.

The insulating film may be formed of polyethylene terephthalate, polyetherimide or polyimide, and a copper foil may be used as the metal conductor foil.

[0009]

Embodiments will be described below with reference to the drawings. As shown in FIG. 1, the ignition coil 1 is an independent ignition type ignition coil housed and installed in a plug hole H formed in a cylinder head C of an engine. It is composed of a case 20 for housing 10.

The coil body 10 has a magnetic core 11 formed by laminating electromagnetic steel sheets, and is mounted concentrically with the magnetic core 11.
It is composed of a secondary coil 12 and a secondary coil 15. The primary coil 12 is mounted on the primary coil bobbin 13 mounted on the magnetic core 11, and the secondary coil 15 is mounted on the primary coil bobbin 13. Secondary coil bobbin 1
6 are provided respectively.

As shown in FIG. 2 (a), the primary coil 12 has a copper foil (thickness: 25 μm) backed by an insulating film 14a (thickness: 20 μm) formed of polyethylene terephthalate (PET). Is 45 μm in total)
14 was cut into a width of 1.5 cm (the cut portion of the copper foil 14 was subjected to insulation treatment), and this was wound 100 to 150 times around the primary coil bobbin 13 as shown in FIG. The lead wires are drawn from the winding start portion and the winding end portion of the copper foil 14, respectively.

The secondary coil 15 is formed by winding a magnet wire 17 around the secondary coil bobbin 16 as in the conventional case.

A thermosetting resin such as an epoxy resin or an insulating oil 30 is filled in a space inside the case 20 in which the coil body 10 is housed. The thermosetting resin or the insulating oil is filled. By 30, the primary coil 12 and the secondary coil 15 are impregnated and fixed, and at the same time, the insulating property of withstanding the high output voltage of the secondary coil 15 is secured.

Although the insulating film 14a is formed of PET in this embodiment, it may be formed of, for example, polyetherimide or polyimide.

The ignition coil 1 configured as described above is
The cross-sectional area of the conductor when the primary coil 12 is energized is φ0.
The conductor resistance is halved because it is almost twice as large as that of the conventional ignition coil having the primary coil formed by winding the 5 mm magnet wire 100 to 150 times. By the way, since the Joule heat is proportional to the conductor resistance and also to the square of the primary current, assuming that the Joule heat generated in the conventional ignition coil is allowed, about 1.4 times the primary current can flow. become.

Further, since the thickness of the copper foil 14 is smaller than the diameter of the magnet wire which has been conventionally used, even if the copper foil 14 includes the lined insulating film 14a, the number of turns of the copper foil 14 is the same as the conventional one. Can be secured.

Therefore, since the primary current can be increased while the inductance L of the primary coil 12 is maintained at the conventional value, the energy stored in the primary coil 12 as a whole can be increased. Become.

[0018]

As described above, in the ignition coil according to the present invention, the metal conductor foil backed by the insulating film is wound around the magnetic core instead of the conventional magnet wire. If properly set, its cross-sectional area can be made larger than that of a conventional magnet wire, so that Joule heat generation can be suppressed even if the primary current is increased to some extent.

Therefore, the energy stored in the primary coil can be increased by increasing the primary current without increasing the number of turns, and as a result, the performance of the entire ignition coil can be improved.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment according to the present invention.

FIG. 2 is a schematic view showing a primary coil of the above.

[Explanation of symbols]

 1 Ignition coil 10 Coil body 11 Magnetic core 12 Primary coil 13 Primary coil bobbin 14 Copper foil 14a Insulating film 15 Secondary coil 16 Secondary coil bobbin 17 Magnet wire 20 Case 30 Thermosetting resin or insulating oil C Cylinder head H plug hole

Claims (2)

[Claims] 1. An ignition coil comprising a magnetic core and a primary coil and a secondary coil formed on the magnetic core, wherein the primary coil winds a metal conductor foil lined with an insulating film around the magnetic core. An ignition coil, which is formed by: 2. The ignition coil according to claim 1, wherein the insulating film is formed of polyethylene terephthalate, polyetherimide or polyimide, and a copper foil is used as the metal conductor foil.