JPH03222404A - Ignition coil for internal combustion engine - Google Patents

Abstract

PURPOSE:To improve both thermal and impact resistance by inhibiting the inflow of hot-setting resin into a gap between an iron core and a primary coil in an internal combustion engine ignition coil made of hot-setting materials. CONSTITUTION:An attempt is made to lay out a sealing material 8 which covers the upper end of a gap 11 between an iron core 7 and a primary bobbin 1 on the upper end of the iron core 7. A further attempt is made to inject hot- setting synthetic resin, for example, epoxy resin 10 into a case 9 and then heat the resin 10 so that it may hot-set. Before the hot-setting synthetic resin 10 is injected, a sealing material 8 is installed to one end of the iron core 7. The sealing material 8 is designed to cover a gap 11 produced between a bobbin 1 and a primary coil which adjoins the iron core 7. This construction prevents the hot-setting synthetic resin from flowing into a gap when it is injected so that an air layer may be formed in the gap 8. It is, therefore, possible to prevent the generation of thermal stress induced by a differential linear expansion coefficient of the iron core 7 and the hot-setting synthetic resin 10 at the gap between the iron core 7 and the primary bobbin 1, thereby preventing thermal impact resistance.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an ignition coil for an internal combustion engine and a method for manufacturing the same, and particularly to a case in which the components of the ignition coil such as the coil and the iron core are pre-molded with thermoplastic resin. The present invention relates to an ignition coil for an internal combustion engine, which is obtained by injecting a thermosetting synthetic resin into the case and thermosetting the ignition coil after the ignition coil is housed in the case, and a method for manufacturing the same.

[Conventional technology]

There are several manufacturing methods for ignition coils for internal combustion engines, and one of them, for example, as described in Japanese Patent Application Laid-Open No. 63-70508, is to manufacture ignition coil components such as the primary coil, secondary coil, and iron core. There are some cases in which a thermosetting synthetic resin such as an epoxy resin is injected into the case after being housed in a case pre-injection molded with a thermoplastic synthetic resin such as polybutylene terephthalate, and then thermosetted.

[Problem to be solved by the invention]

In this prior art, the above-mentioned components of the ignition coil are housed in a pre-injection molded case, and the upper end of the iron core is open, and these parts are separated between the iron core and the primary bobbin. After manufacturing, there is a small gap in order to store the iron core in the primary bobbin. Therefore, when thermosetting resin is subsequently injected into the case,
The thermosetting resin also flows into the gap between the iron core and the primary bobbin, and is thermoset together with other resins.

By the way, there is a difference in linear expansion coefficient between the iron core and the thermosetting synthetic resin due to the difference in materials. For this reason, in a thermal shock test, cracks occurred in the thermosetting resin located in the gap between the iron core and the primary bobbin due to the difference in linear expansion coefficient, and the cracks that appeared near the upper end of the iron core developed, and the primary coil There is a problem in that dielectric breakdown occurs between the coil and the secondary coil, resulting in a drop in output voltage.

Incidentally, as related to this kind of problem with ignition coils for internal combustion engines produced by other manufacturing methods, Japanese Patent Application Laid-Open No. 50-741
No. 23, JP-A-50-98625, JP-A-Sho 5
There are publications such as No. 6-93309.

The purpose of the present invention is to store the components of the ignition coil such as the coil and iron core in a case pre-molded with thermoplastic resin, and then
In internal combustion engine ignition coils, which are made by injecting thermosetting synthetic resin into the case and thermosetting it, thermal shock resistance is achieved by preventing the thermosetting resin from flowing into the gap between the iron core and the primary coil. It is an object of the present invention to provide a scorching coil for an internal combustion engine that is excellent in terms of performance, and to provide a method for manufacturing the same.

[Means to solve the problem]

In order to achieve the above-mentioned object, the present invention stores the components of an ignition coil such as a primary coil, a secondary coil, and an iron core in a case pre-molded with thermoplastic synthetic resin, and then injects thermosetting resin into the case. In an ignition coil for an internal combustion engine formed by injecting a synthetic resin and thermosetting it, the thermosetting synthetic resin is placed adjacent to one end of the iron core, and when the thermosetting synthetic resin is injected, the thermosetting synthetic resin is bonded to the iron core and the bobbin of the primary coil. A sealing member is provided to prevent air from flowing into the gap between the two, and the gap is used as an air layer.

The sealing member is preferably made of silicone rubber having closed cells.

Furthermore, the present invention involves housing the components of the ignition coil, such as the primary coil, secondary coil, and iron core, in a case pre-molded with thermoplastic synthetic resin, and then injecting thermosetting synthetic resin into the case. In the method for manufacturing a thermosetting ignition coil for an internal combustion engine, before injecting the thermosetting synthetic resin, a lid is placed adjacent to one end of the iron core in the gap between the iron core and the bobbin of the primary coil. A sealing member is disposed to prevent thermosetting synthetic resin from flowing into the gap when it is injected.

The sealing member is preferably arranged by dropping a liquid silicone rubber that can be cured at room temperature and a thermosetting resin that forms closed cells. Further, the sealing member may be arranged by using a press molding of a silicone rubber sheet having closed cells.

[Effect]

Before injecting the thermosetting synthetic resin, place a sealing member adjacent to one end of the iron core to cover the gap between the iron core and the bobbin of the primary coil. By preventing the flow into the gap, an air layer is formed in the gap, which prevents the generation of thermal stress due to the difference in linear expansion coefficient between the iron core and the thermosetting synthetic resin, resulting in excellent thermal shock resistance. A new configuration can be obtained.

In addition, by using silicone rubber with closed cells for the sealing member, a sufficient stress absorption effect can be expected.
The sealing member absorbs thermal stress due to the difference in linear expansion coefficient between one end of the core and the thermosetting synthetic resin adjacent to the sealing member, further improving thermal shock resistance.

Liquid silicone rubber can be cured at room temperature, and at the same time,
By disposing the sealing member by dropping a material that foams to form closed cells when cured under heat, the work of disposing the sealing member becomes easy.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG.

In FIG. 1, a primary coil 2 is wound around a primary bobbin 1, and a secondary coil 4 is wound around a secondary bobbin 3. The primary bobbin 1 is molded from thermoplastic synthetic resin.

The primary coil 2 is made of enamelled wire with a wire diameter of about 0°3 to 1.0 mm, and is rolled several thousand times per layer, totaling 10 to 3 times over several layers.
It is laminated and wound about 00 times. The secondary bobbin 3 is molded from the same synthetic resin as the primary bobbin 1,
It has a plurality of flanges 5 arranged in the axial direction and a plurality of grooves 6 separated by the flanges 5.

The secondary coil 4 is wound approximately 5,000 to 20,000 times in total using enameled wire with a wire diameter of approximately 0.03 to 0.1 wn. An iron core 7 is inserted inside the primary bobbin 1, and a sealing member 8, which will be described later, is arranged at the upper end of the iron core 7. The primary bobbin 1 is inserted inside the secondary bobbin 3. These components of the ignition coil are housed in a case 9 that has been injection molded in advance from a thermoplastic synthetic resin such as polybutylene terephthalate. is filled.

The ignition coil for an internal combustion engine having the above configuration is manufactured as follows.

After inserting the iron core 7 inside the primary bobbin 1 and inserting the primary bobbin 1 inside the secondary bobbin 3, these ignition coil components are pre-injection molded from thermoplastic synthetic resin such as polybutylene terephthalate. Store in case 9. Next, a sealing member 8 is placed on the upper end of the iron core 7 to cover the upper end of the gap 11 between the iron core 7 and the primary bobbin 1. Here, the sealing member 8 is arranged by dropping a liquid silicone rubber which can be cured at room temperature and which foams to form closed cells when cured under heat. Thereby, the sealing member 8 can be arranged with a simple operation. Next, a thermosetting synthetic resin, for example, an epoxy resin 1o, is injected into the case 9, and then the thermosetting synthetic resin is heated and hardened.

Therefore, according to this embodiment, the iron core 7 and the primary bobbin 1
Since the sealing member 8 is disposed to cover the gap 11 between the thermosetting resin and the thermosetting synthetic resin, it is prevented from flowing into the gap 11 when the thermosetting synthetic resin is injected, and an air layer is formed in the gap. Generation of thermal stress in the gap 11 due to the difference in linear expansion coefficient between the iron core and the thermosetting synthetic resin is prevented, and thermal shock resistance is improved. Further, the closed cells of the sealing member 8 made of silicone rubber account for 30 to 70% of the total volume of the sealing member, and since there is almost no intrusion of epoxy resin into these closed cells, the thickness of the sealing member 8 is 1. A sufficient stress absorption effect can be expected with a thickness of ~3 mm. Therefore, the sealing member 8 absorbs the thermal stress due to the difference in linear expansion coefficient between the end face of the iron core 7 and the epoxy resin 10 above the sealing member 8, and the thermal shock resistance is further improved.

FIG. 2 shows the thermal shock test results of this example in comparison with a conventional product. Thermal shock test is -40°01 hour and +130°C
This was done by repeating for 1 hour.

If one cycle is one hour at -40°C and one hour at +130°C, cracks occurred in the thermosetting synthetic resin after 50 to 100 cycles in the conventional product, but this example product reached 300 cycles. No cracks were observed, demonstrating that the material has extremely good thermal shock resistance.

In this example, the sealing member 8 was arranged by pouring liquid silicone rubber and curing it. The same effect can also be obtained by this method.

〔effect〕

According to the present invention, thermal shock resistance is improved because thermal stress is prevented from occurring due to the difference in linear expansion coefficient between the iron core and the thermosetting synthetic resin in the gap between the iron core and the primary bobbin.

In addition, since silicone rubber with closed cells is used for the sealing member, thermal stress due to the difference in linear expansion coefficient between one end of the core and the thermosetting synthetic resin adjacent to the sealing member is absorbed, making it heat resistant. Impact resistance is further improved.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of an ignition coil for an internal combustion engine according to an embodiment of the present invention, and FIG. 2 is a thermal shock test of a conventional product and a product of the present invention to demonstrate the improvement effect of the present invention on thermal shock resistance. It is a figure showing a result. Explanation of symbols 1...Primary bobbin 2...Primary coil 3...Secondary bobbin 4...Secondary coil 7...Iron core 8...Sealing member 9...Case 10... Thermosetting synthetic resin 11... Gap

Claims (5)

[Claims] (1) After storing the components of the ignition coil such as the primary coil, secondary coil, and iron core in a case pre-molded with thermoplastic synthetic resin, thermosetting synthetic resin is injected into the case and thermoset. In the ignition coil for an internal combustion engine, there is provided an ignition coil for an internal combustion engine, which is provided adjacent to one end of the iron core to prevent the thermosetting synthetic resin from flowing into the gap between the iron core and the bobbin of the primary coil when the thermosetting synthetic resin is injected. An ignition coil for an internal combustion engine, characterized in that a sealing member is provided to prevent the ignition, and the gap is an air layer. (2) The ignition coil for an internal combustion engine according to claim 1, wherein the sealing member is made of silicone rubber having closed cells. (3) After storing the components of the ignition coil such as the primary coil, secondary coil, and iron core in a case pre-molded with thermoplastic synthetic resin, thermosetting synthetic resin is injected into the case and thermoset. In the method of manufacturing an ignition coil for an internal combustion engine, before injecting the thermosetting synthetic resin, sealing is performed adjacent to one end of the iron core to cover a gap between the iron core and the bobbin of the primary coil. A method for manufacturing an ignition coil for an internal combustion engine, comprising arranging a member to prevent thermosetting synthetic resin from flowing into the gap when it is injected. (4) In the method for manufacturing an ignition coil for an internal combustion engine according to claim 3, the arrangement of the sealing member is such that liquid silicone rubber can be cured at room temperature and at the same time foams to form closed cells when cured under heat. 1. A method for producing an ignition coil for an internal combustion engine, the method comprising dropping an ignition coil having the properties of (5) The method for manufacturing an ignition coil for an internal combustion engine according to claim 3, wherein the sealing member is arranged by using a press-molded silicone rubber sheet having closed cells. ignition coil manufacturing method.