JPH0349383Y2 - - Google Patents

Description

[Detailed Description of the Invention] <Industrial Field of Application> This invention relates to a closed magnetic path type ignition coil for igniting and driving internal combustion engines of various vehicles.

<Prior art> A secondary coil is fitted outside the primary coil and housed in an insulating case, and an insulating resin is cast into the case and hardened, and the inner periphery of the bobbin of the primary coil is A closed magnetic path type ignition coil that penetrates a part of a pair of iron cores forming a closed magnetic path inside was developed by the applicant in 1983.
-Proposed in No. 74513.

In a closed magnetic path type ignition coil, the total magnetic flux (Σф) generated by the primary coil's magnetomotive force (primary coil turns x current) is divided by фM flowing along the closed magnetic path of the iron core and the primary coil as shown in Figure 3. This is the sum of the leakage magnetic flux фL that passes through a part of the iron core in the coil bobbin (the primary bobbin penetrating part) and flows into the air, contrary to the above фM, and the magnetic flux фr that does not pass through the iron core at all and flows only in the air. On the other hand, in a closed magnetic circuit type ignition coil, an air gap is provided in the iron core in order to reduce the residual magnetic flux, increase the magnetic flux change when the primary current is cut off, and generate a high voltage in the secondary coil.

<Problems to be solved by the invention> In the above-mentioned prior example, the air gap is defined as the part surrounded by the winding part of the primary coil, that is, as shown in Fig. 3.
It is provided inside the winding section of the next coil. Therefore, among the aforementioned magnetic flux, leakage magnetic flux фL flows into the air through a part of the iron core that has passed through the bobbin of the primary coil.
The air gap becomes magnetic resistance.

Therefore, in order to obtain a predetermined total magnetic flux, it is necessary to take measures such as increasing the number of turns of the primary coil to correspondingly increase the magnetomotive force, which increases the product cost accordingly.

<Means for solving the problem> Therefore, in the present invention, the air gap provided in the iron core forming the closed magnetic circuit is located on the inner circumference of the primary coil bobbin, but in the axial direction from the part where the primary coil is wound. We propose a closed magnetic circuit type ignition coil located on the outside.

<Function> According to the present invention, since the air gap of the iron core is located axially outward from the part where the primary coil is wound, the magnetic resistance to the leakage magnetic flux фL is sufficiently small.

On the other hand, since the assumption that the air gap is located within the inner circumference of the primary coil bobbin is maintained, the same method as before can be used for the iron core fixing work, and no new separate parts are required. There's nothing to do.

<Example> Fig. 1 shows an example constructed according to the present invention, in which 1 is a primary coil, 2 is a secondary coil fitted outside the primary coil, and 3 is molded from synthetic resin. 4 is an insulating resin such as a thermosetting epoxy resin cast into the case, 5 and 6 are a pair of iron cores forming a closed magnetic path, and 7 is an air gap.

Case 3 has an opening at the bottom, and the primary,
When housing both secondary coils, the above-mentioned opening is closed with one end of the bobbin 1' of the primary coil, then insulating resin 3 is cast, and a part of the iron core forming a closed magnetic path is placed in the primary bobbin 1'. Make it penetrable.

The pair of cores 5 and 6 in the embodiment of FIG. 1 are L-shaped;
Long and short legs 5a and 5 are provided at each end of the intermediate pieces 5' and 6', respectively.
b, 6a and 6b, the long legs of one core, for example 5a, are inserted into the inner periphery of the primary bobbin from one end, and the short legs 6b of the other type of iron core are inserted from the other end to connect both cores 5.
and 6 are assembled in opposite directions, and an air gap 7 is provided between the legs 5a and 6b in the inner periphery of the primary bobbin. This air gap 7 is located in the primary bobbin 1' as described above, but because it is located outside in the axial direction away from the winding part of the primary coil 1, it has a large magnetic field with respect to the leakage magnetic flux фL. There will be no resistance,
It can be made substantially small enough.

On the other hand, the air gap is in the primary coil bobbin 1', in other words each core 5, 6 can be fitted into the bobbin with its respective leg portions 5a and 6b, so that these leg portions 5a, 6
b is mechanically held by the bobbin.

Therefore, the other legs 5b and 6 of both iron cores 5 and 6
As for the method of fixing the core by connecting a, any known existing method can be used as is.
All you have to do is butt the two together and weld them together.

For example, if the air gap simply satisfies the condition that it is not within the area where the primary coil is wound, and the structure is as shown in the second figure, the following problems occur.

That is, in the reference structure example shown in the second diagram,
The pair of cores 5 and 6 are U-shaped and have legs 5a and 5b, 6a and 6b of approximately the same length at each end of the intermediate pieces 5' and 6', with the legs of one core, e.g. From one end to the inner circumference of the primary bobbin, attach the leg of the other iron core, e.g.
are inserted from the other end, and an air gap 7 is provided outside the case 3 between the other legs 5b and 6b of each core. However, in the case of such a reference structure example, the legs 5a and 6a of the iron core inserted into the primary bobbin
Since the ends of the two legs cannot be welded, it is necessary to place them against each other, sandwich the other legs 5b and 6b with a backing plate 8 made of non-magnetic material such as aluminum or stainless steel, and tighten them with rivets 9 to fix the iron cores 5 and 6. This causes not only separate parts to be required but also the work process to be complicated.

<Effects of the invention> The air gap provided according to the invention is located at a position that does not impair manufacturability, and although the conventional assembly method can be adopted, the leakage magnetic flux is lower than that of the conventional example. The magnetic resistance to фL can be greatly reduced.

Therefore, if the current is the same, the number of turns of the primary coil can be reduced, and the primary coil can be made smaller and a cheaper product can be provided.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view of an embodiment of the closed magnetic circuit type ignition coil of the present invention, and Fig. 2 is an explanatory diagram of an example of a structure in which the gap is taken outside the primary coil, but is less desirable than that of the present invention. , Fig. 3 is an explanatory diagram of a conventional closed magnetic circuit type ignition coil and magnetic flux, and in the figure, 1 is the primary coil,
1' is the bobbin, 2 is the secondary coil, 3 is the case,
4 is an insulating resin, 5 and 6 are a pair of iron cores, 7 is an air gap, and фL is a leakage magnetic flux.

Claims (1)

[Claims for Utility Model Registration] A secondary coil is fitted outside the primary coil and housed in an insulating case, and an insulating resin is cast into the case and hardened, and the bobbin of the primary coil is In a closed magnetic path type ignition coil formed by penetrating a part of a pair of iron cores forming a closed magnetic path in the inner circumference of the iron core;
A closed magnetic circuit type ignition coil, characterized in that it is located on the inner circumference of a secondary coil bobbin but axially outside of a portion where the primary coil is wound.