JPH09205026A - Ignition coil - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a small-sized ignition coil having a high voltage output by a method wherein, in an ignition coil disposed directly above an ignition plug, a primary coil and a secondary coil are wound along a longitudinal direction of an iron core. SOLUTION: A central core 53 is on a cylindrical axis of a plug hole of an ignition coil 50, a primary coil is wound on an outer periphery of this central core 53 in a longitudinal direction of the central core 53, a secondary coil is provided on the same axis as the primary coil on this outer periphery, and a yoke 54 is provided on an outer periphery of the secondary coil to form a closed magnetic path iron core. Further, a rubber bush 58 for fixedly connecting an ignition plug 30 with an ignition coil body is provided in a bottom part of the ignition coil 50, and a high pressure output part 59 for supplying a high voltage output from the secondary coil is embedded in this inside. Further, a coil control element 55 and a primary connector 56 for inputting a primary voltage are integrated with a case 57. Thus, the degree of freedom in designing is increased and downsizing is possible.

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 directly mounted on a spark plug.

[0002]

2. Description of the Related Art In an internal combustion engine, particularly for an automobile, an ignition coil is required to have a small size and high characteristics with the miniaturization of the internal combustion engine. Conventionally, in a double overhead cam type internal combustion engine, an ignition coil that does not require a distributor is arranged in a space created between cylinder heads, and various plug-in type ignition coils have been put to practical use in other types of internal combustion engines. ing. However, such an ignition coil is also required to have additional values such as improved output characteristics and the incorporation of an igniter, and it is actually difficult to reduce the size of the ignition coil body. It has become difficult to arrange the coils in the limited space of the internal combustion engine, especially the cylinder head.

Under the above circumstances, there have been proposed some types in which a part or all of an ignition coil is arranged in a space formed in a plug hole in which a spark plug is mounted. Generally, the outer diameter of a spark plug of a vehicle internal combustion engine is about 16 mm to 20 mm, and a plug hole into which the spark plug is inserted has an inner diameter of about 20 mm to 35 mm and a depth of about 100 mm.

FIG. 3 shows a structure diagram of a conventional ignition coil of a plug hole insertion type, and FIG. 4 shows a sectional view of the FIG. 3 taken along line AA in the direction of the arrow. In FIGS. 3 and 4, an ignition plug 30 is arranged on the bottom surface of the plug hole 10, and an ignition coil 20 described later is provided directly above the ignition plug 30. The ignition coil 20 has an iron core 23 arranged on the cylinder axis of the plug hole 10 and a primary winding that is an outer periphery of the iron core 23 and is perpendicular to the longitudinal direction of the iron core 23. Coil 21, secondary coil 22 coaxially wound around primary coil 21 around this, high-voltage output unit 29 for outputting the output from secondary coil 22 to ignition plug 30, ignition plug 30, and ignition A rubber bush 28 for connecting and fixing the coil 20 main body is embedded in the plug hole 10, and outside the plug hole 10, a coil control element 25 such as a power transistor and a primary connector 26 for inputting a primary voltage. Is provided, and the parts forming the ignition coil 20 are integrated by a case 27.

[0005]

In the plug-hole-buried type ignition coil having the above-described structure, the iron core 23 and the primary coils 21, 2 are used.
Due to the arrangement method of the secondary coil 22, the magnetic flux induced in the primary coil passes in the cylinder axis direction. In addition, the central iron core cross-sectional area of the iron core 23 (in the “prior art”, the AA cross-sectional area of FIG. 3) is
It is limited by the diameter of the plug hole 10 and has a cross-sectional area of 10 to 20.
Only% can be used. For example, if the diameter of the cylinder is 22.5 mm (cylinder cross-sectional area of about 400 square millimeters), the central iron core cross-sectional area can be secured only about 50 square millimeters, and the iron core 23 will be magnetically saturated, so sufficient output performance It was difficult to induce enough magnetic flux.

Further, when the ignition coil is arranged in the plug hole 10, an eddy current is generated in the inner circumferential direction of the plug hole 10 so as to cancel the magnetic flux induced by the primary current, so that a sufficient output is obtained in the plug hole. Things are getting more and more difficult.

Further, when detecting the combustion state in the cylinder for controlling the ignition state, the combustion state is detected from a part of the secondary coil 22. The information is below the secondary coil as shown in FIG.
That is, it can be obtained only from the end of the secondary coil 22 on the spark plug 30 side. A control unit (not shown) that generally controls the ignition state
Is provided above the ignition coil or outside the ignition coil, so a high-voltage lead wire derived from the lower end of the secondary coil 22
The 223 must be pulled out from the secondary coil 22 to the top of the ignition coil with an appropriate insulation distance (several millimeters). Therefore, in order to secure this insulation distance, the ignition coil becomes large in size, and it is not suitable for an ignition coil immediately above the ignition plug arranged in a plug hole or the like.

In view of the above problems, it is an object of the present invention to provide an ignition coil which can be buried in a plug hole of an internal combustion engine, but which can provide a sufficiently high voltage output as needed.

[0009]

In order to solve the above problems, according to the present invention, in an ignition coil arranged directly above an ignition plug, a primary coil and a secondary coil are wound along a longitudinal direction of an iron core. The ignition coil is characterized by the above.

[0010]

1 is a side sectional view of an ignition coil according to an embodiment of the present invention, and FIG. 2 is a sectional view taken along the line BB. Figures 1 and 2
In the above, the ignition coil 50 is configured as follows. The present embodiment is an ignition coil embedded in a plug hole of a double overhead cam type internal combustion engine, an iron core (central core) 53 is located on the cylinder axis of the plug hole, and the outer periphery of the central core 53 is And 1 in the longitudinal direction of the central core 53.
A secondary coil 51 is wound, and a secondary coil 52 coaxially wound with the primary coil 51 is provided on the outer periphery of the secondary coil 51.
A yoke 54 is provided on the outer circumference of the secondary coil 52 to form a closed magnetic circuit iron core. Further, at the bottom of the ignition coil 50, a rubber bush 58 for connecting and fixing the ignition plug 30 and the main body of the ignition coil 50 is provided, and a high voltage output from the secondary coil 52 is supplied to the inside of the rubber bush 58. The high-voltage output section 59 is embedded. A primary connector for embedding in the plug hole and for inputting the primary voltage to the coil control element 55 such as a power transistor outside the plug hole.
56 is provided, and the parts forming the ignition coil 50 are integrated by a case 57. In the above description, the case shape in which the primary and secondary coils are arranged is a cylindrical shape having a diameter that can be inserted into the inner diameter of the plug hole or a square columnar shape similar to this.

As described above, in the present embodiment, the ignition coil of the type which is buried in the plug hole of the double overhead cam type internal combustion engine is described. However, this ignition coil is of a single overhead cam type or any other type. It is of course possible to use it in an internal combustion engine. Although there is a case where the plug hole does not exist in such other types of internal combustion engine, the present invention does not necessarily have to be buried in the plug hole, and even if the ignition coil is arranged directly above the ignition plug, the effect can be obtained. It is what is done.

[0012]

With the above structure, the cross-sectional area of the central iron core (BB cross-sectional area of FIG. 1 in the present invention) is not limited by the cylinder diameter of the ignition coil, and the required cross-sectional area can be increased by extending the cylinder length. Can be secured. For example, in the case where the diameter of the cylinder diameter of the case where the primary and secondary coils are arranged is 22.5 millimeters, the central iron core area is 50 square millimeters,
The ignition coil of the present invention can secure about 100 mm 2. Therefore, magnetic saturation of the central core 53 disappears, and it becomes possible to induce a magnetic flux sufficient to obtain sufficient output characteristics.

Even when a control device for detecting the combustion state in the cylinder is added, it is not necessary to consider the insulation distance between the high-voltage lead wire and the secondary coil as in the conventional ignition coil. The degree of freedom in design is increased, and the ignition coil body can be downsized.

[Brief description of drawings]

FIG. 1 shows a side cross-sectional view of an ignition coil of the present invention.

FIG. 2 shows a cut view of the BB plane of FIG.

FIG. 3 shows a cross-sectional view of a conventional ignition coil.

FIG. 4 shows a cut view of plane AA of FIG.

FIG. 5 is a diagram showing a positional relationship between a conventional high voltage lead wire and a secondary coil.

[Explanation of symbols]

 In the drawings, the same reference numerals indicate the same or corresponding parts. 10 Plug hole 30 Spark plug 50 Ignition coil 51 Primary coil 511 Primary bobbin 52 Secondary coil 522 Secondary bobbin 53 Central core 54 Yoke 55 Coil control element 56 Primary connector 57 Case 58 Rubber bush 59 High voltage output part

Claims (1)

[Claims] 1. An ignition coil arranged immediately above an ignition plug, wherein a primary coil and a secondary coil are wound along a longitudinal direction of an iron core.