JP2003197448A - Ignition coil for internal combustion engine and manufacturing method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ignition coil which has high electrical insulation characteristics and is low in production costs. <P>SOLUTION: The ignition coil 1 include a case 2, a core 22 located inside the case 2, a primary spool 25 located coaxially around the core 22 in the case 2, a primary coil 26 wound around the primary spool 25, a secondary spool 23 located coaxially around the core 22 in the case 2, a secondary coil 24 wound around the secondary spool 23, and a resin insulator 5 filled in the case 2. Between the primary spool 25 and the secondary spool 23, the spool between the secondary coil 24 and the core 22 and/or the secondary coil 24 and the primary core 26 is composed of a base material resin, which is lower than polybutyleneterephthalate in adhesion with respect to the resin insulator 5, and is higher than polyphenylenesulphide in dielectric breakdown voltage. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an internal combustion engine ignition coil for generating a high voltage applied to an ignition plug of an internal combustion engine and a method for manufacturing the same.

[0002]

2. Description of the Related Art An ignition coil for an internal combustion engine (hereinafter, simply referred to as "ignition coil") is a device for generating a spark in a gap of a spark plug by generating a high voltage by a mutual induction action. There are various types of this ignition coil. For example, a stick-type ignition coil installed in a plug hole is a rod-shaped core, a cylindrical secondary spool installed on the outer peripheral side of the core, and a secondary coil wound around this secondary spool. And a cylindrical primary spool installed on the outer peripheral side of the secondary coil, and a primary coil wound around the primary spool. That is, the core, the secondary spool, the secondary coil, the primary spool, and the primary coil are arranged coaxially from the inner peripheral side. These members are housed in a hollow cylindrical case. A resin insulating material is filled in the case in order to ensure electric insulation of each member in the case and to bond each member.

Here, in the prior art, among the primary spools and the secondary spools, in particular, the base resin forming the spool (primary spool in the above example) which is arranged between the primary coil and the secondary coil is used. It was required to have high electrical insulation. The reason for this is that if insulation breakdown occurs and the secondary coil side, that is, the high voltage side, and the primary coil side, that is, the low voltage side, become conductive, the secondary coil side may not be able to secure a desired voltage.

Conventionally, among the primary spool and the secondary spool, particularly the base resin forming the spool arranged between the primary coil and the secondary coil has adhesiveness with the resin insulating material. It was required to be expensive. The reason is that the linear expansion coefficient of the base resin of the spool is different from that of the wire material of the coil wound around the spool. Therefore, if the resin insulation material filled between the spool and the wire and the base resin of the spool have low adhesiveness, the spool and the resin insulation material may be separated due to thermal stress. . When the spool and the resin insulating material are separated from each other, corona discharge is generated in the space formed by the separation, and the secondary coil side may not be able to secure a desired voltage.

As described above, conventionally, the base resin for forming the spool has been required to have high electric insulation and high adhesiveness with the resin insulating material.

In order to meet the above requirements, polyphenylene ether (PPE), polybutylene terephthalate (PBT), polyethylene terephthalate (PET), etc., which have high electric insulation and high adhesion to resin insulating materials, are used as the base material of the spool. It was used as a material resin.

[0007]

However, when the spool is formed of the base resin having high adhesiveness with the resin insulating material, the following problems occur. That is, as described above, the linear expansion coefficient of the base resin is different from that of the wire material of the coil. For this reason, when the ignition coil is used in a cooling / heating cycle environment in which temperature increase and temperature decrease are repeated, thermal stress is repeatedly generated in the spool due to the difference in linear expansion coefficient. This thermal stress can be relaxed if the spool and the resin insulating material are separated. However, the adhesiveness between the spool and the resin insulating material is high in order to suppress peeling. Therefore, the thermal stress cannot be relaxed, and the spool may be cracked. When the spool is cracked, the high voltage side and the low voltage side are electrically connected to each other, and the secondary coil may not be able to secure a desired voltage.

Therefore, for example, Japanese Patent Laid-Open No. 11-115545.
In the conventional ignition coil, as shown in Japanese Patent Publication No.
As shown in (a) and (b), the spool 200 and the wire 2
The peeling tape 203 was wound around the resin insulating material 202 filled on the 01 side. And this peeling tape 20
By separating the spool 200 and the resin insulating material 202 by 3, the difference in linear expansion coefficient between the spool 200 and the resin insulating material 202 in FIG. 9A, and the spool 200 and 206 and the wire material in FIG. 9B. The generation of thermal stress due to the difference in linear expansion coefficient between 201 and the resin insulating materials 202 and 204 was suppressed. And spools 200 and 206
The cracks were suppressed from occurring.

Further, in order to suppress the occurrence of cracks in the spool, in the conventional ignition coil, for example, styrene ethylene butene styrene (SEB) is used as the base resin of the spool.
A rubber component such as S) was added. The rubber component enhances the toughness of the spool and prevents the spool from cracking.

As described above, in the conventional ignition coil,
In order to prevent the spool from cracking, it is necessary to wind a release tape around the spool or add a rubber component to the spool. Therefore, the manufacturing cost of the ignition coil is high. Also, the manufacturing process was complicated.

By the way, the above problem is caused by the high adhesiveness between the base resin forming the spool and the resin insulating material. Therefore, for example, polyphenylene sulfide (PP) introduced in JP-A-8-339928 is disclosed.
If a resin having low adhesiveness with the resin insulating material is adopted as the base resin as in S), the possibility that the spool will be cracked is small.

However, PPS is composed of PPE, PBT,
The electrical insulation is lower than that of PET. Therefore, PP
When S is used as the base resin, when the resin insulating material and the spool are separated due to the low adhesiveness of PPS, the insulation between the high-voltage side and the low-voltage side may be rather easily broken.

That is, if there is a slight gap between the resin insulating material and the spool, the insulating property may be impaired. For this reason, conventionally, as the base resin forming the spool, a resin having high adhesiveness with the resin insulating material is used, and the gap between the resin insulating material and the spool is configured to be eliminated as much as possible. Was the design concept in.

As described above, the base resin for forming the spool has conventionally been required to have high electric insulation and high adhesion to the resin insulating material. However, if the adhesiveness is high, the spool will crack. On the contrary, if the adhesiveness is low, the spool and the resin insulating material are likely to be separated from each other.

Therefore, the present inventor has examined how the combination of the adhesiveness of the base resin forming the spool to the resin insulating material and the electrical insulation of the base resin has a relationship with dielectric breakdown. . As a result, we have found that by using a resin with low adhesiveness to resin insulation and high electrical insulation as the base resin of the spool, dielectric breakdown is less likely to occur without using a peeling tape or the like. .

The ignition coil of the present invention has been completed based on this finding. Therefore, it is an object of the present invention to provide an ignition coil which has high electric insulation and does not require a peeling tape or the like and has a low manufacturing cost.

Another object of the present invention is to provide a method of manufacturing an ignition coil which can manufacture the ignition coil of the present invention relatively easily.

[0018]

In order to solve the above-mentioned problems, an ignition coil of the present invention is provided with a case, a rod-shaped core installed in the case, and a coaxial installation on the outer peripheral side of the core in the case. A primary coil made of a wire wound around the primary spool, a cylindrical secondary spool installed coaxially on the outer peripheral side of the core in the case, and a secondary spool. An ignition coil having a secondary coil made of a wound wire and a resin insulating material filled in a case, the secondary coil being a primary spool or a secondary spool, and a core and / or a secondary coil. The spool between the primary coil and the primary coil is made of a base resin whose adhesive force to the resin insulation material is less than that of polybutylene terephthalate and whose breakdown voltage exceeds that of polyphenylene sulfide. And wherein the door.

That is, in the ignition coil of the present invention, at least one of the primary spool and the secondary spool is PBT.
It is formed of a base resin having both an adhesive strength of less than PPS and a dielectric breakdown voltage exceeding PPS.

Here, the adhesive force with the resin insulating material is a parameter for evaluating the adhesiveness of the base resin to the resin insulating material. The higher the adhesive strength, the higher the adhesiveness. The adhesive force is measured by the measuring method shown in Examples described later.
The dielectric breakdown voltage is a parameter for evaluating electric insulation. The higher the breakdown voltage, the higher the electrical insulation. The dielectric breakdown voltage is also measured by the measuring method shown in Examples described later.

In the ignition coil of the present invention, the adhesive force of the base resin forming the spool to the resin insulating material is low. Therefore, peeling may occur between the spool and the resin insulating material. However, even if peeling occurs, since the base resin has high electric insulation, there is little possibility that dielectric breakdown occurs between the high voltage side and the low voltage side.

That is, in the ignition coil of the present invention, the spool itself is intentionally peeled off from the resin insulating material by forming the spool itself from the base resin having a low adhesive force to the resin insulating material, so that the spool is cracked. It is to suppress doing. Even if the spool and the resin insulating material are separated from each other, the high electric insulation property suppresses the dielectric breakdown between the high voltage side and the low voltage side.

According to the ignition coil of the present invention, high electric insulation can be ensured. Further, according to the ignition coil of the present invention, it is not necessary to wind a peeling tape around the spool or add a rubber component to the base resin of the spool. Therefore, the structure of the ignition coil can be simplified and the manufacturing cost can be reduced.

In order to solve the above-mentioned problems, the ignition coil of the present invention includes a case, a rod-shaped core installed in the case, and a cylindrical shape installed substantially coaxially on the outer peripheral side of the core in the case. Primary spool, a primary coil made of a wire wound around the primary spool, a cylindrical secondary spool installed substantially coaxially on the outer peripheral side of the core in the case, and a secondary spool. An ignition coil having a secondary coil made of wire and a resin insulating material filled in a case, the secondary coil and the core and / or the secondary coil and the primary coil among the primary spool and the secondary spool. The spool between is made of a base resin whose adhesive strength to the resin insulation material is less than that of polyethylene terephthalate and whose breakdown voltage exceeds that of polyphenylene sulfide. To.

That is, in the ignition coil of the present invention, at least one spool of the primary spool and the secondary spool is PET.
It is formed of a base resin having both an adhesive strength of less than PPS and a dielectric breakdown voltage exceeding PPS.

In the ignition coil of the present invention, the adhesive force of the base resin forming the spool to the resin insulating material is low. Therefore, peeling may occur between the spool and the resin insulating material. However, even if peeling occurs, since the base resin has high electric insulation, there is little possibility that dielectric breakdown occurs between the high voltage side and the low voltage side.

That is, in the ignition coil of the present invention, the spool itself is intentionally separated from the resin insulating material by forming the spool itself with the base resin having a low adhesive force to the resin insulating material, so that the spool is cracked. It is to suppress doing. Even if the spool and the resin insulating material are separated from each other, the high electric insulation property suppresses the dielectric breakdown between the high voltage side and the low voltage side.

According to the ignition coil of the present invention, high electric insulation can be ensured. Further, according to the ignition coil of the present invention, it is not necessary to wind a peeling tape around the spool or add a rubber component to the base resin of the spool. Therefore, the structure of the ignition coil can be simplified and the manufacturing cost can be reduced.

It is preferable that the base resin is crystalline polystyrene. The adhesive strength of crystalline polystyrene to the resin insulating material is very low, less than PBT. Also, the dielectric breakdown voltage of crystalline polystyrene exceeds PPS and is extremely high. Therefore, when the spool is made of crystalline polystyrene, there is little risk of dielectric breakdown between the high voltage side and the low voltage side even if the spool is separated from the resin insulating material. Also, crystalline polystyrene has high tracking resistance. Further, crystalline polystyrene has a high fluidity of the molten resin at the time of molding such as injection molding. From these points, crystalline polystyrene is also suitable as the base resin for forming the spool.

The ignition coil of the present invention is suitable for being embodied as a stick type ignition coil which is mounted in a plug hole of a cylinder.

The ignition coil of the present invention can maintain high electrical insulation for a long period of time even in a severe cold-heat cycle environment. Further, according to the ignition coil of the present invention,
There is no need to wind release tape on the spool. Therefore, it is easy to reduce the outer diameter of the ignition coil. Therefore, the ignition coil of the present invention is suitable for being embodied as a stick type ignition coil that undergoes severe temperature changes and requires a small diameter.

In order to solve the above-mentioned problems, the ignition coil of the present invention comprises a case, a rod-shaped core installed in the case, and a cylindrical shape installed substantially coaxially on the outer peripheral side of the core in the case. Primary spool, a primary coil made of a wire wound around the primary spool, a cylindrical secondary spool installed substantially coaxially on the outer peripheral side of the core in the case, and a secondary spool. An ignition coil having a secondary coil made of wire and a resin insulating material filled in a case, the secondary coil and the core and / or the secondary coil and the primary coil among the primary spool and the secondary spool. The spool between the two is characterized by being made of a base resin having an electrical insulating property even when a high voltage is generated in the secondary coil against peeling between the resin insulating material and the spool.

The base resin of the ignition coil of the present invention can ensure insulation between the secondary coil side and the primary coil side even if peeling occurs between the resin insulating material and the spool. In other words, even if peeling occurs, the high-voltage side and the low-voltage side are less likely to cause dielectric breakdown.

Preferably, the crystalline polystyrene is an improved crystalline polystyrene whose linear expansion coefficient can be adjusted, and the linear expansion coefficient of the end portion of the spool made of the improved crystalline polystyrene is 100 times that of the resin insulating material. %,
It is better to set it as 135% or less.

Here, the linear expansion coefficient is set to 135% or less because, as will be described later, when the linear expansion coefficient of the end portion of the spool exceeds 135%, the expansion / contraction amount of the resin insulating material is
This is because the amount of expansion and contraction of the ends becomes extremely large. And
This is because some problems may occur in the resin insulating material and the spool.

Preferably, the improved crystalline polystyrene is
It is formed by adding reinforcing fibers to crystalline polystyrene, and it is preferable that the reinforcing fibers are randomly or circumferentially oriented at the ends of the spool.

By randomly or circumferentially dispersing the reinforcing fibers, the coefficient of linear expansion at the end of the spool can be reduced. For this reason, the difference between the amount of expansion and contraction of the resin insulating material and the amount of expansion and contraction of the ends is reduced. Therefore, according to this configuration, the possibility that the resin insulating material and the spool will be defective is reduced.

Preferably, the reinforcing fiber is glass fiber and the resin insulating material is epoxy resin. If the combination of the reinforcing fiber and the resin insulation material is limited to the above combination, the difference between the expansion and contraction amount of the resin insulation material and the expansion and contraction amount of the end portion can be surely reduced.

In order to solve the above-mentioned problems, the method of manufacturing an ignition coil according to the present invention comprises a winding part around which a wire is wound,
A method for manufacturing an ignition coil, comprising a spool including end portions arranged at both longitudinal ends of a winding portion, a spool raw material preparing step of adding a reinforcing fiber to a molten resin to prepare a spool raw material, and a spool raw material Is injected into the cavity from a gate located at a position facing the end molding portion of the cavity of the mold, the injected spool raw material is cooled and hardened in the cavity, and the reinforcing fibers are randomly or circumferentially formed at the end. A spool material forming step of forming a spool material oriented in a direction and a gate cutting step of cutting a portion of the spool material corresponding to a gate are provided.

That is, the ignition coil manufacturing method of the present invention includes a spool raw material preparing step, a spool material forming step, and a gate cutting step. Of these, in the spool raw material preparation step, reinforcing fibers are added to and dispersed in the molten resin. Then, a spool raw material that is a raw material of the spool is prepared. Further, in the spool material molding step, a spool material in which the reinforcing fibers are randomly or circumferentially oriented at the end is molded. Further, in the gate cutting step, the gate corresponding portion connected to the end of the spool material is cut off. The ignition coil of the present invention is completed by disposing the spool thus obtained in the case together with other members and filling the case with a resin insulating material. According to the manufacturing method of the present invention, an ignition coil having a spool in which reinforcing fibers are oriented can be manufactured relatively easily.

Preferably, the gate is a ring gate or a film gate. According to this configuration, the reinforcing fibers can be oriented more easily. Therefore, the ignition coil of the present invention can be manufactured more easily. However, the ignition coil of the present invention in which the reinforcing fibers are oriented can be manufactured not only by the manufacturing method of the present invention described above but also by other known manufacturing methods.

In order to solve the above-mentioned problems, the ignition coil of the present invention is provided with a case, a rod-shaped core installed in the case, and a coaxial winding installed on the outer peripheral side of the core in the case. A cylindrical primary spool that has a winding part around which a coil is wound, and a cylindrical secondary spool that is installed coaxially around the outer periphery of the core in the case and that has a winding part around which the winding is wound. And a resin insulating material filled in a case and cured, wherein at least one spool of the primary spool and the secondary spool is an SPS spool using crystalline polystyrene as a base resin. Is characterized by.

That is, in the ignition coil of the present invention, at least one of the primary spool and the secondary spool is an SPS spool. As described above, the adhesive force of crystalline polystyrene to the resin insulating material is very low. Therefore, according to the ignition coil of the present invention, the thermal stress caused by the difference in linear expansion coefficient can be relaxed. Also, the dielectric breakdown voltage of crystalline polystyrene is very high. Therefore, according to the ignition coil of the present invention, SP
Even if the S spool is separated from the resin insulating material, there is little risk of dielectric breakdown between the high voltage side and the low voltage side. As described above, according to the ignition coil of the present invention, it is possible to have both high thermal stress relaxation property and high electrical insulation property.

Preferably, the primary spool is an SPS spool. The winding wound on the primary spool has a lower voltage than the winding wound on the secondary spool. Therefore, when the SPS spool is used as the primary spool rather than the secondary spool, it is less likely that a defect such as dielectric breakdown will occur between windings due to separation of the SPS spool and the resin insulating material. Therefore, the ignition coil of this configuration has high reliability against defects such as dielectric breakdown.

Preferably, the adhesive force of the base resin to the resin insulating material is less than 15 MPa.

The reason why the adhesive strength is set to less than 15 MPa is as follows. Regarding the thermal stress (tensile stress) acting on the spool due to the contraction of the resin insulating material when the spool and the resin insulating material do not separate, FEM analysis (analysis software: Cybernet System Co., Ltd. De
sign Space) was performed. As a result of the analysis, the tensile stress acting on the spool was 24 MPa.

Therefore, if the adhesive force is set to less than 24 MPa, the SPS spool can be separated from the resin insulating material. However, it is necessary to consider variations in the dimensions of the members forming the ignition coil and variations or changes in the material characteristics of the members. Also, the adhesive force is 24MP
Even if it is less than a, if the adhesive strength is high, a defect such as a crack may occur in the SPS spool. For this reason, the adhesive strength of the base resin to the resin insulation material is 15 MPa, with a safety margin of 24 MPa secured.
Less than

Preferably, a winding portion of the SPS spool,
A gap is defined between the resin insulating material that has penetrated and hardened between the windings wound around the winding portion, and the gap is formed over 70% or more of the surface area of the winding portion. It is better to have a structure.

A winding forming a coil is wound around the winding portion of the SPS spool. The resin insulating material has penetrated and hardened between the windings. In this configuration, a gap is defined between the winding portion and the resin insulating material. This gap is 70 when the total surface area of the winding is 100%.
% Over the area. The reason why the gap is formed to be 70% or more of the surface area of the winding portion is that if it is less than 70%, thermal stress is easily transmitted to the SPS spool due to the difference in linear expansion coefficient between the members in the ignition coil. And SP
This is because the S spool may have a defect such as a crack. In the present invention, the winding portion means a portion having a coil on the outer peripheral surface of the spool, as shown in FIG. 4 described later.

Preferably, the gap is 90 times the surface area of the winding portion.
It is better to have a structure in which it is formed over the range of 100% or more. According to this configuration, the SPS spool is used even in a severe cold environment of the vehicle, for example, in a cold region or a severe heat region, on a hill, on a hill, on a full accelerator, in a race, or for a long time. It is unlikely that defects such as cracks will occur. That is, the ignition coil of this configuration has high durability against a cold environment.

Preferably, a winding portion of the SPS spool,
A gap is defined between the resin insulating material that has penetrated and hardened between the windings wound around the winding portion, and the radial width of the gap is 0.01 mm or more. Good. The radial width of the gap is 0.01 mm or more is 0.01 m
This is because if it is less than m, the gap is not substantially defined and the thermal stress is easily transmitted to the SPS spool.

Preferably, the radial width of the gap is 0.3 m.
It is better to set it as less than m. The reason why the radial width of the gap is less than 0.3 mm is as follows. That is, when the SPS spool is arranged on the outer peripheral side with respect to the other spool, this gap is a coil (for example, a primary coil) formed by windings wound around the SPS spool.
And a coil (for example, a secondary coil) including a winding wound around another spool. Therefore, if the radial width of the gap is large, the insulation distance between the primary coil and the secondary coil is substantially reduced accordingly. For these reasons, the radial width of the gap is set to less than 0.3 mm.

Preferably, the radial width of the gap is 0.01.
It is preferable that the width is at least mm and the gap is formed over 70% or more of the surface area of the winding portion. According to this configuration, it is possible to more reliably reduce the thermal stress transmitted from the resin insulating material to the SPS spool.

Preferably, the radial width of the gap is 0.01.
It is preferable that the width is not less than mm and the gap is formed over 90% or more of the surface area of the winding portion. According to this configuration, the thermal stress transmitted from the resin insulating material to the SPS spool can be more reliably relaxed.

Preferably, the dielectric breakdown voltage of the base resin is
15 kV / m according to JIS K 6911 measurement method
It is better to set it as m or more. In this structure, the dielectric breakdown voltage of crystalline polystyrene is set to 15 kV / mm or more.

The dielectric breakdown voltage is set to 15 kV / mm or higher for the following reason. FEM analysis of the electric field strength generated on the spool (analysis software: Cybernet System Co., Design Space)
I went. As a result of the analysis, the electric field strength generated on the spool was 14.5 kV.

Therefore, the dielectric breakdown voltage is set to 14.5 kV.
With the above settings, insulation can be ensured. However, it is necessary to consider variations in the dimensions of the members forming the ignition coil and variations or changes in the material characteristics of the members. For this reason, the dielectric breakdown voltage of the base resin is 15k, with a safety margin of 14.5kV secured.
It was set to V or more.

When the breakdown voltage is 15 kV or higher,
For operating environment conditions where a relatively high voltage is applied to the base resin,
The outer diameter of the ignition coil can be reduced without causing dielectric breakdown in the base resin. For example, it is possible to obtain an ignition coil which can be inserted into a plug hole to apply a high voltage of 30 kV to an ignition plug.

Preferably, the case is made of a highly adhesive resin having a higher adhesiveness to the resin insulating material than the base resin. The highly adhesive resin forming the case has higher adhesiveness to the resin insulating material than the base resin. Therefore, in the case, the resin insulating material is pulled to the inner surface of the case. Therefore, according to this configuration, the resin insulating material and the SPS spool are more likely to be separated. Therefore, a gap can be easily formed between the resin insulating material and the SPS spool.

In order to solve the above-mentioned problems, the ignition coil of the present invention is provided with a case, a rod-shaped core installed in the case, and a coaxial winding installed on the outer peripheral side of the core in the case. A cylindrical primary spool that has a winding part around which a coil is wound, and a cylindrical secondary spool that is installed coaxially around the outer periphery of the core in the case and that has a winding part around which the winding is wound. An ignition coil having a resin insulating material filled in a case and hardened, the winding portion having at least one spool of the primary spool and the secondary spool, and a winding wound around the winding portion. It is characterized in that a gap is formed between the resin insulating material that has penetrated between the wires and hardened, and after the resin insulating material has hardened.

In the ignition coil of the present invention, a gap is formed between the winding portion of at least one of the spools and the resin insulating material that has penetrated and hardened between the windings wound around the winding portion. Has been done. According to the ignition coil of the present invention, the thermal stress applied to the spool from the thermosetting resin can be blocked by this gap. Therefore, it is possible to suppress the occurrence of defects such as cracks in the spool.

Preferably, the spool adjacent to the gap is
It is better to have a structure that is a primary spool. The winding wound on the primary spool has a lower voltage than the winding wound on the secondary spool. Therefore, when the primary spool is arranged adjacent to the gap rather than the secondary spool, the gap is less likely to cause a problem such as dielectric breakdown between windings. Therefore, the ignition coil of this configuration has high reliability against defects such as dielectric breakdown.

Preferably, the base resin forming the spool adjacent to the gap is made of crystalline polystyrene. As mentioned above, the breakdown voltage of crystalline polystyrene is very high. Therefore, according to the ignition coil of this configuration, the high-voltage side and the low-voltage side are less likely to cause dielectric breakdown despite the formation of the gap. Therefore, according to the ignition coil of this configuration, it is possible to have both high thermal stress relaxation and high electrical insulation.

Preferably, the gap is 70 times the surface area of the winding portion.
It is better to have a structure in which it is formed over the range of 100% or more. The reason why the gap is formed in 70% or more of the surface area of the winding portion is that, as described above, if it is less than 70%, the thermal stress is easily transmitted to the SPS spool due to the difference in linear expansion coefficient between the members in the ignition coil. Is. Then, a problem such as a crack may occur in the SPS spool.

Preferably, the gap is 90 times the surface area of the winding portion.
It is better to have a structure in which it is formed over the range of 100% or more. As described above, according to this configuration, even if the cold environment of the vehicle is severe, the possibility that the spool will suffer a crack or the like is small. That is, the ignition coil of this configuration has high durability against a cold environment.

Preferably, the radial width of the gap is 0.01.
It is better to have a configuration of mm or more. As described above, the radial width of the gap is set to 0.01 mm or more.
This is because if it is less than 1 mm, the gap is not substantially defined and the thermal stress is easily transmitted to the spool.

Preferably, the radial width of the gap is 0.3 m.
It is better to set it as less than m. The reason why the radial width of the gap is less than 0.3 mm is as follows. That is, as described above, when the spool adjacent to the gap is arranged on the outer peripheral side of the other spool, if the radial width of the gap is large, the primary coil and the secondary coil are substantially separated by that amount. This is because the insulation distance of is shortened.

Preferably, the radial width of the gap is 0.01.
It is preferable that the width is at least mm and the gap is formed over 70% or more of the surface area of the winding portion. According to this configuration, it is possible to more reliably reduce the thermal stress transmitted from the resin insulating material to the spool adjacent to the gap.

Preferably, the radial width of the gap is 0.01.
It is preferable that the width is not less than mm and the gap is formed over 90% or more of the surface area of the winding portion. According to this structure, the thermal stress transmitted from the resin insulating material to the spool adjacent to the gap can be more surely relaxed.

Preferably, the dielectric breakdown voltage of the base resin forming the spool adjacent to the gap is JIS K 691.
In the measurement method of No. 1, it is better to set it as 15 kV / mm or more. In this structure, the dielectric breakdown voltage of the base resin is set to 15 kV / mm or more.

The dielectric breakdown voltage is set to 15 kV / mm or higher because a safety allowance is secured at the electric field strength of 14.5 kV obtained by FEM analysis as described above. When the dielectric breakdown voltage is 15 kV or higher, the outer diameter of the ignition coil can be reduced without causing dielectric breakdown in the base resin under the use environment condition in which the base resin has a relatively high voltage. For example, it is possible to obtain an ignition coil which can be inserted into a plug hole to apply a high voltage of 30 kV to an ignition plug.

Preferably, the dielectric breakdown voltage of the base resin forming the spool adjacent to the gap is 15 kV / mm or more in the measuring method of actually measuring the spool itself. The method of measuring the dielectric breakdown voltage according to JIS K 6911 is a method of applying a voltage to a test piece and measuring the dielectric breakdown voltage. On the other hand, the method for measuring the dielectric breakdown voltage of this configuration directly measures the dielectric breakdown voltage of the spool itself.

FIG. 10 conceptually shows the measuring method of this configuration. A grounded rod-shaped electrode 501 is inserted on the inner peripheral side of the cylindrical spool 500. On the other hand, another electrode 502 is arranged on the outer peripheral surface of the spool 500. That is, the cylindrical wall of the spool 500 is sandwiched by the two electrodes 501 and 502. The voltage applied between the two electrodes 501 and 502 is gradually increased, and the voltage when the electrodes 501 and 502 are electrically connected is the breakdown voltage in this configuration. According to this configuration, the dielectric breakdown voltage can be easily measured without separately preparing a test piece or the like. Here, the breakdown voltage is set to 15 kV / mm or more because, as described above, the electric field strength obtained by FEM analysis is 14.5 kV.
This is because the safety cost was secured.

Preferably, the adhesive force of the base resin forming the spool adjacent to the gap to the resin insulating material is 15M.
It is better to set it as less than Pa. Here, the adhesive force is set to less than 15 MPa as described above.
This is because the tensile stress obtained by the M analysis secured a safety allowance of 24 MPa.

In order to solve the above-mentioned problems, the method of manufacturing an ignition coil according to the present invention is such that a case, a rod-shaped core installed in the case, and a substantially coaxial shape in the case on the outer peripheral side of the core. And a cylindrical inner spool having a winding portion around which the winding is wound, and a winding portion around the outer periphery of the core in the case and being substantially coaxial with the winding. A method for manufacturing an ignition coil, comprising: a cylindrical outer spool having an outer peripheral surface having a lower adhesiveness with a resin insulating material than the inner peripheral surface of the case; and the resin insulating material filled and cured in the case. And an insulating material filling step of filling the resin insulating material in a liquid state in the case in which each of the members is arranged, an insulating material gelling step of gelling the filled resin insulating material at high temperature, The resin insulating material is applied to the case and the outer spacer. And having and an insulating material cooling step of cooling with Lumpur.

That is, the method for manufacturing an ignition coil according to the present invention includes an insulating material filling step, an insulating material gelling step, and an insulating material cooling step. Among them, in the insulating material filling step, first, members such as a primary spool and a secondary spool are arranged in the case, and then the case is filled with a liquid resin insulating material. In the insulating material gelling step, the resin insulating material is held at the curing temperature for a predetermined time and gelled. In the insulating material cooling step, the thermosetting resin that has completed the curing reaction is cooled. Since the adhesiveness between the outer peripheral surface of the outer spool and the resin insulation is lower than the adhesiveness between the inner peripheral surface of the case and the resin insulation, the resin insulation from the outer peripheral surface of the outer spool may be removed during cooling of the thermosetting resin. Separated, it comes to adhere to the inner surface of the case. When the thermosetting resin was filled through the above steps, it penetrated and hardened between the winding portion of at least one of the primary spool and the secondary spool and the winding wound around the winding portion. A gap is formed between the resin insulation material and the resin insulation material. That is, according to the method for manufacturing an ignition coil of the present invention, the ignition coil according to claim 22 can be manufactured.

The manufacturing method of the present invention utilizes the total shrinkage of the resin insulating material to form the gap. FIG. 11 schematically shows the volume change in the curing process of the thermosetting resin. In the figure, the horizontal axis represents temperature. In the figure, the vertical axis represents the volume. As shown in the figure, first, point A to point B accompanying heating.
Up to (curing temperature), the volume of the liquid thermosetting resin increases due to the simple thermal expansion of the liquid. Next, from point B to point C,
The thermosetting resin is kept at the curing temperature for a predetermined time.
At this time, the thermosetting resin changes from liquid to gel due to the curing reaction. Then, the volume of the thermosetting resin is reduced. Finally, from point C to point D, the thermosetting resin for which the curing reaction has ended is cooled to room temperature. At this time, the volume of the thermosetting resin is further reduced. As a result, the volume of the point D is reduced with respect to the volume of the point A. This is called total contraction.

According to the manufacturing method of the present invention, the ignition coil of claim 22 can be manufactured relatively easily by utilizing this total contraction. However, the ignition coil according to claim 22 is not limited to the manufacturing method of the present invention, and can be manufactured by a known manufacturing method.

[0079]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

(1) First Embodiment First, the structure of the ignition coil 1 of this embodiment will be described. FIG. 1 shows an axial sectional view of the ignition coil device 1 of the present embodiment. The ignition coil 1 is a so-called stick-type ignition coil, and is arranged for each cylinder in a plug hole above an engine block (not shown). As shown in the figure, the outer shell of the ignition coil 1 is composed of a case 2 and a high pressure tower 3. The case 2 is made of resin and has a cylindrical shape. The high-voltage tower 3 is also made of resin and has a cylindrical shape. The high voltage tower 3 is fixed to the lower end of the case 2.

Inside the case 2, a core 22, a secondary spool 23, a secondary coil 24, a primary spool 25, a primary coil 26, an outer peripheral core 27, a rubber tube 28 and the like are housed.

The core 22 has a rod shape and is arranged on the central axis of the cylindrical case 2. This core 22
It is formed by laminating silicon steel plates in the radial direction.

The rubber tube 28 is arranged so as to cover the outer peripheral surface of the core 22. The rubber tube 28 has a role as an insulating material.

The secondary spool 23 is arranged on the outer peripheral side of the rubber tube 28. The secondary spool 23 is made of resin and has a bottomed cylindrical shape. The secondary coil 24 is arranged on the outer peripheral surface of the secondary spool 23. The secondary coil 24 is made of a wire material wound and laminated on the secondary spool 23.

The primary spool 25 is arranged on the outer peripheral side of the secondary coil 24. Here, the base resin forming the primary spool 25 is crystalline polystyrene. Like the secondary spool 23, the primary spool 25 also has a bottomed cylindrical shape. Further, the primary coil 26 is the primary spool 2
5 is arranged on the outer peripheral surface. This primary coil 26 is
The primary spool 25 is made of a wire wound and laminated.

The dummy coil 29 is connected below the secondary coil 24. This dummy coil 29 is also formed by winding a wire rod. The dummy coil 29 electrically connects the secondary coil 24 and the terminal plate 30. By electrically connecting the two members by the dummy coil 29 instead of the single wire, the surface area of the electrical connection portion between the both members is increased, and electric field concentration on the electrical connection portion is avoided.

The outer peripheral core 27 is arranged outside the primary coil 26. The outer peripheral core 27 is formed by winding a thin silicon steel plate in a tubular shape. The outer peripheral core 27 suppresses the magnetic force lines from leaking out of the ignition coil 1. The winding start end and the winding end end of the outer peripheral core 27 are not joined. Therefore, a slit extending in the axial direction is formed between the winding start end and the winding end end.

The connector 4 is arranged so as to project obliquely upward in the radial direction from the upper end of the case 2. A terminal 40 is fixed to the connector 4 by insert molding. The terminal 40 is electrically connected to the igniter 20 arranged on the upper part of the case 2. The igniter 20 has a role of switching the primary current supplied to the primary coil 26.

The inside of the case 2 is filled with a resin insulating material 5 made of epoxy resin. And the insulation between each said member arrange | positioned closely is ensured.

On the other hand, inside the high voltage tower 3, a terminal plate 30, a high voltage terminal 31 and a spring 32 are installed.

The terminal plate 30 has a disk shape. At the center of the terminal plate 30, a plate-shaped claw portion bent upward is arranged. The high voltage terminal 31 has a disk shape having a convex portion in the center of the upper surface, that is, a pot lid shape. Then, the convex portion of the high voltage terminal 31 is inserted into the claw portion of the terminal plate 30. On the other hand, the lower portion of the high voltage terminal 31 has a cup shape. An upper end of a spring 32 connected to an ignition plug (not shown) is inserted on the inner peripheral side of the cup-shaped lower portion. A cylindrical plug cap 6 made of rubber is attached to the lower end of the high-pressure tower 3. The spark plug is pressed into this plug cap 6.

Next, the current flow of the ignition coil device 1 of this embodiment will be described. On the primary side, that is, the low-voltage side, the primary current flows in the order of terminal 40 → igniter 20 → primary coil 26. When the primary current is switched by the igniter 20, a high voltage is generated on the secondary side due to the mutual induction effect. This high voltage causes a spark in the spark plug gap. That is, on the secondary side, that is, on the high voltage side, the secondary current flows from the secondary coil 24 to the dummy coil 29.
→ Terminal plate 30 → High voltage terminal 31 → Spring 32 → Spark plug.

Next, the features and effects of the ignition coil device 1 of this embodiment will be described. In the present embodiment, the base resin of the primary spool 25 arranged between the primary coil 26 and the secondary coil 24 is crystalline polystyrene (Sy).
ndiotactic-Poly-Styrene, S
PS). Unlike the structure of conventional amorphous polystyrene (PS), SPS has a structure in which side chains are alternately coordinated to the main chain in opposite directions. Due to this structure, S
The adhesive strength of PS to the resin insulating material is very low, less than PBT. Moreover, the breakdown voltage of SPS exceeds PPS and is very high. Since this SPS is the base resin of the primary spool 25, the primary spool 25 of the ignition coil 1 of the present embodiment.
Is easily separated from the resin insulating material 5 with which the primary coil 26 side is filled. Therefore, the possibility that a crack will occur in the primary spool 25 and the secondary spool 23 is small. Further, the primary spool 25 has high electric insulation. Therefore, even if the primary spool 25 is separated from the resin insulating material 5, the high-voltage side and the low-voltage side are less likely to cause dielectric breakdown.

Further, SPS has a characteristic that a carbonized conductive path (track) is hard to be formed even if the surface where electrolysis occurs is contaminated with dust or moisture. That is, the tracking resistance is high. Also, the fluidity of the molten resin during molding such as injection molding is high. From these points,
SPS is suitable as a base resin that forms the spool of the ignition coil of the present invention.

In the first embodiment, when viewed minutely, a gap is defined between the resin insulating material that has penetrated into the primary coil and the primary spool.

2 (a) and 2 (b) are enlarged sectional views showing the vicinity of the winding portion 255 of the primary spool 25 of the ignition coil of this embodiment. As shown in the figure, the resin insulating material 5a penetrates between the windings 256 and is hardened. This resin insulation material 5a
A gap 9 is defined between the inner peripheral surface and the outer peripheral surface of the winding portion 255. The gap 9 is formed over 95% of the surface area of the winding portion 255. The radial width of the gap 9 is
It is 0.15 mm.

In the ignition coil of the present embodiment, the outer peripheral core 2 which is a part of the case in claim 34
The base resin forming the primary spool 25 has lower adhesiveness to the resin insulating material 5 than the material of No. 7. In particular,
The outer peripheral core 27 is made of a silicon steel plate. The base resin forming the primary spool 25 is crystalline polystyrene.

The ignition coil of this embodiment was manufactured by the manufacturing method including the above-described insulating material filling step, insulating material gelling step, and insulating material cooling step. The curing temperature of the resin insulating material at the time of manufacturing was 120 ° C. (see FIG. 11). FIG. 3 shows an enlarged cross-sectional view of the vicinity of the primary spool end of the ignition coil of this embodiment (corresponding to the portion A in FIG. 1). By adopting the above-described manufacturing method, as shown in the figure, from the adhesiveness between the resin insulating material 5 and the inner peripheral surface 271 of the outer peripheral core 27,
Since the adhesiveness between the resin insulating material 5 and the outer peripheral surface 257 of the primary spool 25 is low, a gap can be formed between the resin insulating material 5 and the outer peripheral surface 257 of the primary spool 25 during cooling.

According to the ignition coil of this embodiment, as shown in FIG.
As shown in (a), the primary spool 25 and the resin insulating material 5
and a are separated by a gap 9. Therefore, the thermal stress due to the difference in linear expansion coefficient between the primary spool 25 and the resin insulating material 5a can be relaxed. Further, as shown in FIG. 2B, the primary spool 25 and the secondary spool 23
The thermal stress due to the difference in linear expansion coefficient between the winding 256 and the resin insulating materials 5a and 5b can be relaxed.

According to the ignition coil of this embodiment,
The gap 9 is formed over 95% of the surface area of the winding portion 255. Therefore, for example, even in a cold environment of the vehicle such as use in a cold region or a severe heat region, heavy use on slopes, heavy use of fully open accelerator such as race, long-term use, etc. It is unlikely that defects such as cracks will occur. That is, the ignition coil of this embodiment has high durability against a cold environment.

According to the ignition coil of this embodiment,
The radial width of the gap 9 is set to 0.15 mm.
Therefore, there is little risk that the insulation distance between the primary coil and the secondary coil will be substantially shortened.

(2) Second Embodiment The difference between this embodiment and the first embodiment is that the primary spool is formed by the improved SPS. Therefore, only this point will be described in this section.

First, the structure of the primary spool will be described. FIG. 4 shows an enlarged cross-sectional view of the ignition coil of the present embodiment near the primary spool end (corresponding to the portion A in FIG. 1). The members corresponding to those in FIG. 3 are indicated by the same symbols. The rubber tube is omitted. As shown in the figure, the primary spool 25 is formed by an improved SPS 252 including an SPS 250 and a glass fiber 251. The primary spool 25 has a winding portion 25 having a primary coil 26 on the outer peripheral surface.
3 and the end portions 25 arranged at both ends in the axial direction of the winding portion 253.
It consists of 4 and.

The primary spool 25 of this embodiment is also an improved S.
Since it is made of PS252, it can be easily peeled off from the resin insulating material 5, like the primary spool of the first embodiment. Therefore, the end portion 254 and the resin insulating material 5 are easily separated. When the end portion 254 and the resin insulating material 5 are separated from each other, the end portion 254 and the resin insulating material 5 independently expand and contract with respect to the same heat load.

At this time, if the linear expansion coefficient of the end portion 254 exceeds 135% of the linear expansion coefficient of the resin insulating material 5, the expansion / contraction amount of the end portion 254 is extremely large with respect to the expansion / contraction amount of the resin insulating material 5. growing. Therefore, for example, when the end portion 254 is reduced in diameter toward the inner peripheral side (left side in FIG. 4), the end portion 254 and the resin insulating material 5 filling the lower side or the inner peripheral side of the end portion 254 are separated. There is a risk of pressure contact. Then, due to this pressure contact force, some trouble may occur in the resin insulating material 5 and the primary spool 25.

In this respect, the glass fibers 251 are randomly dispersed at the end 254 of the primary spool 25 of this embodiment. When the glass fibers 251 are randomly dispersed, the linear expansion coefficient of the end portion 254 can be reduced. Therefore, the linear expansion coefficient of the end portion 254 of the present embodiment is determined by the resin insulating material 5.
It is almost equal to the linear expansion coefficient of the epoxy resin constituting the. Therefore, the amount of expansion and contraction when the end portion 254 and the resin insulating material 5 are subjected to the same heat load is substantially equal. Therefore, according to the ignition coil of the present embodiment, the end portion 254 and the resin insulating material 5 are
There is little risk that and will come into pressure contact. For this reason, the ignition coil of this embodiment is less likely to cause defects and has high reliability.

On the other hand, the glass fiber 251 is axially oriented in the winding portion 253 of the primary spool 25 of this embodiment. When the glass fiber 251 is oriented in the axial direction, the linear expansion coefficient of the winding portion 253 becomes large. That is, the winding portion 253
The difference between the linear expansion coefficient and the linear expansion coefficient of the resin insulating material 5 becomes large. However, in the winding portion 253, only the resin insulating material 5 around the winding portion 253 expands and contracts in the radial direction to form a gap, and even if the gap is formed, SPS is used as the resin material. It has a high breakdown voltage and is less problematic.

Next, a method for manufacturing the ignition coil of this embodiment will be described. Of the members that make up the ignition coil,
The primary spool is manufactured by a manufacturing method including a spool material preparing step, a spool material forming step, and a gate cutting step.

In the spool raw material preparation process, SPS
(Product name: XAREC, manufactured by Idemitsu Petrochemical Co., Ltd.) Glass fibers are added to a molten resin and dispersed. Then, a spool raw material that is a raw material for the primary spool is prepared.

In the spool material forming step, a spool material in which glass fibers are oriented is formed. FIG. 5 shows a perspective view of the vicinity of the cavity of the mold used in this step. The cavity 302 includes an end molding portion 303 and a winding portion molding portion 304. The end portion molding portion 303 is set to have a larger radial width than the winding portion molding portion 304. A ring gate 301 is provided around the outer peripheral side of the portion of the cavity 302 that faces the end portion molding portion 303.

The spool raw material 300 injected from the nozzle (not shown) of the injection molding machine flows from the ring gate 301 into the end molding portion 303 in the cavity 302. That is, it flows in the direction of diameter reduction. Here, the extending direction of the cavity 302 is perpendicular to the inflow direction of the spool raw material 300. In addition, the end portion molding portion 303 is the winding portion molding portion 3
The width in the radial direction is larger than 04. For this reason, the glass fiber 305 in the spool raw material 300 which has flowed into the end portion 3
In No. 03, it has no orientation and is randomly dispersed.

The spool raw material 300 which has flowed into the end portion molding portion 303 subsequently flows into the winding portion molding portion 304.
The winding portion molding portion 304 has a smaller radial width than the end portion molding portion 303. The spool raw material 300 flows in along the longitudinal direction of the winding portion molding portion 304. Therefore, the glass fiber 305 in the spool raw material 300 is oriented along the longitudinal direction of the winding portion molding portion 304 in the winding portion molding portion 304.

The spool raw material 300 is placed in the cavity 302.
After being filled, the spool raw material 300 is cooled and hardened. Then, a mold (not shown) is released to obtain a spool material.
At the end of the obtained spool material, glass fibers are randomly arranged. Further, in the winding portion of this spool material, glass fibers are oriented in the longitudinal direction.

In the gate cutting step, the ring gate corresponding portion connected to the end of the spool material is cut off. Then, if necessary, a finishing process is performed on the gate cut surface at the end portion by a grinder or a flat file.

The primary spool of this embodiment is manufactured through the above steps. Then, the primary coil is arranged on the outer peripheral surface of the winding portion of the primary spool, and combined with a secondary spool manufactured by injection molding, a case, a member such as a high pressure tower, and the ignition coil of the present embodiment is completed.

(3) Third Embodiment The difference between this embodiment and the second embodiment is that the glass fibers are oriented in the circumferential direction at the end of the primary spool. Therefore, only this point will be described in this section.

FIG. 6 shows an enlarged cross-sectional view of the vicinity of the primary spool end of the ignition coil of this embodiment (corresponding to the portion A in FIG. 1). The members corresponding to those in FIG. 3 are indicated by the same symbols. The rubber tube is omitted. As shown in the figure, the end portion 254 of the primary spool 25 of the present embodiment is
The glass fibers 251 are oriented in the circumferential direction. By orienting the glass fibers 251 in the circumferential direction, the linear expansion coefficient of the end portion 254 can be reduced. The linear expansion coefficient of the end portion 254 of the present embodiment is substantially equal to the linear expansion coefficient of the epoxy resin forming the resin insulating material 5. Therefore, the amount of expansion and contraction when the end portion 254 and the resin insulating material 5 are subjected to the same heat load is substantially equal. Therefore, according to the ignition coil of the present embodiment, the possibility that the end portion 254 and the resin insulating material 5 are pressed against each other is small.
For this reason, the ignition coil of this embodiment is less likely to cause defects and has high reliability.

Next, a method of manufacturing the ignition coil of this embodiment will be described. The difference between the manufacturing method of the present embodiment and the manufacturing method of the second embodiment is that a film gate, instead of a ring gate, is arranged at the end molding portion of the cavity. Therefore, only this point will be described in this section.

FIG. 7 is a perspective view showing the vicinity of the cavity of the mold used in the spool material forming step of this embodiment. The cavity 302 includes an end molding portion 303 and a winding portion molding portion 304. A film gate 307 is arranged on the outer peripheral side of the portion of the cavity 302 that faces the end portion molding portion 303.

The spool material 300 injected from the nozzle (not shown) of the injection molding machine flows from the film gate 307 into the end molding portion 303 in the cavity 302. At this time, the spool raw material 300 flows in the circumferential direction of the end molding portion 303. Therefore, the glass fibers 305 in the spool raw material 300 are oriented in the circumferential direction at the end portion molding portion 303.

The spool raw material 300 which has flowed into the end portion molding portion 303 subsequently flows into the winding portion molding portion 304.
At this time, the spool raw material 300 has the winding portion molding portion 304.
Flows in along the longitudinal direction. For this reason, the glass fiber 305 in the spool raw material 300 is
In, the winding portion molding portion 304 is oriented along the longitudinal direction.

The spool raw material 300 is placed in the cavity 302.
After being filled, the spool raw material 300 is cooled and hardened. Then, a mold (not shown) is released to obtain a spool material. At the ends of the obtained spool material, the glass fibers are oriented in the circumferential direction. Further, in the winding portion of this spool material, glass fibers are oriented in the longitudinal direction.

In the gate cutting step, the ring gate corresponding portion connected to the end of the spool material is cut off. Then, if necessary, a finishing process is performed on the gate cut surface at the end portion by a grinder or a flat file.

The primary spool of this embodiment is manufactured through the above steps. Then, the primary coil is arranged on the outer peripheral surface of the winding portion of the primary spool, and combined with a secondary spool manufactured by injection molding, a case, a member such as a high pressure tower, and the ignition coil of the present embodiment is completed.

(4) Others The embodiments of the ignition coil of the present invention have been described above. However, the embodiment is not particularly limited to the above embodiment. Various modifications and improvements can be made by those skilled in the art.

For example, in the ignition coil device 1 of the above embodiment, the primary spool 25 is arranged on the outer side and the secondary spool 23 is arranged on the inner side, but the secondary spool 23 is arranged on the outer side and the primary spool 25 is arranged on the inner side. Good.

In the ignition coil 1 of the first embodiment, only the base resin of the primary spool 25 is SPS, but the base resin of all spools may be SPS. The base resin is not limited to SPS. P
Any resin having both an adhesive strength of less than BT and a dielectric breakdown voltage of more than PPS can be used as the base resin.

In addition, in the ignition coils of the second and third embodiments, the secondary coil 24 and the primary coil 2
6, the primary spool 25 arranged on the outer peripheral side is formed by the improved SPS 252. The reason is that the end portion of the spool on the outer peripheral side is surrounded by the resin insulating material, and in particular, a problem is likely to occur near the end portion due to a difference in linear expansion coefficient between the spool and the resin insulating material. . However, the spool on the inner peripheral side (the secondary spool 23 in the second and third embodiments) may be formed by the improved SPS 252. If the spool on the inner peripheral side is formed by the improved SPS 252, the reliability of the ignition coil is further improved.

In the ignition coils of the second and third embodiments, the primary spool 25 is the SPS250.
And modified glass fiber 251 and modified SPS252. Then, due to the orientation of the glass fibers 251, the end 2
The linear expansion coefficient of 54 and the winding part 253 was adjusted. However, the coefficient of linear expansion can also be adjusted by controlling the density of the glass fibers in the end portion 254 and the winding portion 253. The configuration of the improved SPS is not particularly limited as long as the linear expansion coefficient can be adjusted. For example, instead of the glass fiber 251, carbon fiber or the like may be used. Further, other additives may be added instead of the fiber material.

In order to orient the glass fiber, a ring gate was used in the manufacturing method of the second embodiment and a film gate was used in the manufacturing method of the third embodiment. The reason is that when a ring gate or a film gate is used, it is easy to orient the glass fibers in a random or circumferential direction at the ends.
However, the type of gate is not particularly limited as long as the glass fibers can be oriented. For example, a disc gate or a fan gate may be used.

Further, for example, magnets having a polarity opposite to the direction of the magnetic flux generated by being excited by the coil may be arranged at both ends of the core 22 of the ignition coil of the above embodiment. With this configuration, the voltage generated on the secondary side can be easily increased in voltage.

The ignition coil of the above embodiment is a so-called stick type ignition coil which is mounted in the plug hole. The ignition coil of the present invention can maintain high electrical insulation for a long period of time even under a severe thermal cycle environment. Further, according to the ignition coil of the present invention, it is not necessary to separately wind a peeling tape or the like on the spool in order to prevent cracks. Therefore, it is easy to reduce the outer diameter of the ignition coil. Therefore, the ignition coil of the present invention is suitable for being embodied as a stick-type ignition coil in which the temperature change is severe and the diameter is required to be reduced, as in the present embodiment. However, the ignition coil of the present invention can be embodied as another type of ignition coil.

Further, although the case according to claim 34 is the outer peripheral core in the first embodiment, the case 2 made of resin may be used as the case in the ignition coil without the outer peripheral core. In this case, the case has high adhesiveness with the resin insulation material.
Made of ET or PBT, which has low adhesion with resin insulation
The outer spool can be formed of PS and SPS.

[0134]

EXAMPLE In this section, a plate-shaped sample using SPS (trade name XAREC, manufactured by Idemitsu Petrochemical Co., Ltd.) as a base resin instead of the spool of the actual ignition coil is taken as an example, and a resin insulation material made of epoxy resin The adhesive strength with and the dielectric breakdown voltage were measured. In addition, PPE, PBT, PET, PP
The plate-like samples having S as a base resin were used as Comparative Example 1, Comparative Example 2, Comparative Example 3 and Comparative Example 4, respectively, and the adhesive force with the resin insulating material and the dielectric breakdown voltage were measured. The samples of Examples and Comparative Examples were produced by injection molding.

(1) Measuring Method First, the measuring method of the adhesive force with the resin insulating material will be described. FIG. 8 shows an outline of the measuring method of the adhesive force. In the preparation for measurement, as shown in the drawing, first, the sample 100 and the sample 101 are arranged in a state in which only a part of their surfaces are superposed. The sample 100 and the sample 101 are made of the same resin. Next, a portion where the sample 100 and the sample 101 overlap each other is bonded with a resin insulating material 102 made of an epoxy resin. Then, in this state, the resin insulating material 102 is cured.

The adhesive force is measured by pulling the sample 100 and the sample 101 in the directions in which they are separated from each other, as indicated by the arrows in the figure. Then, by pulling, the load when either the sample 100 or the sample 101 and the resin insulating material 102 are separated is measured.
The value obtained by dividing this load by the adhesive area (indicated by the dotted line in the figure) between the sample 100 or the sample 101 and the resin insulating material 102 is taken as the adhesive force.

The dielectric breakdown voltage is measured by gradually applying a voltage to the sample. Then measure the lowest voltage at which the insulation of the sample is destroyed. This minimum voltage is the breakdown voltage.

(2) Measurement Results Table 1 shows the measurement results of the adhesive strength with the resin insulating material and the dielectric breakdown voltage of the examples and comparative examples.

[0139]

[Table 1]

As shown in Table 1, it is understood that the example samples have lower adhesive strength to the resin insulating material than the samples of comparative examples 1 to 3. Further, it is found that the sample of the example has the same adhesive force as the sample of the comparative example 4.

Further, it is understood that the sample of the example has a higher dielectric breakdown voltage than the samples of the comparative examples 2 to 4.
Further, it is found that the sample of the example has the same dielectric breakdown voltage as the sample of the comparative example 1.

[0142]

According to the present invention, it is possible to provide an ignition coil having a high electric insulation and a low manufacturing cost.

[Brief description of drawings]

FIG. 1 is an axial sectional view of an ignition coil according to a first embodiment.

FIG. 2 is an enlarged cross-sectional view of the vicinity of the winding portion of the primary spool of the ignition coil of the first embodiment.

FIG. 3 is an enlarged cross-sectional view of the ignition coil of the first embodiment in the vicinity of the primary spool end portion.

FIG. 4 is an enlarged cross-sectional view of an ignition coil according to a second embodiment in the vicinity of an end portion of a primary spool of the ignition coil.

FIG. 5 is a perspective view of the vicinity of a cavity used in a spool material forming step of the ignition coil manufacturing method according to the second embodiment.

FIG. 6 is an enlarged cross-sectional view of an ignition coil according to a third embodiment in the vicinity of an end portion of a primary spool of the ignition coil.

FIG. 7 is a perspective view of the vicinity of a cavity used in a spool material molding step of the ignition coil manufacturing method according to the third embodiment.

FIG. 8 is a diagram showing a method for measuring an adhesive force with a resin insulating material.

FIG. 9 is an axially enlarged cross-sectional view near a spool of a conventional ignition coil.

FIG. 10 is a conceptual diagram of a dielectric breakdown voltage measuring method for actually measuring the spool itself.

FIG. 11 is a schematic diagram showing a volume change in the curing process of the thermosetting resin.

[Explanation of symbols]

1: Ignition coil, 2: Case, 22: Core, 23: Secondary spool, 24: Secondary coil, 25: Primary spool, 2
50: SPS, 251: glass fiber, 252: improved SP
S, 253: winding part, 254: end part, 255: winding part,
256: winding, 257: outer peripheral surface, 26: primary coil, 2
7: outer peripheral core, 271: inner peripheral surface, 28: rubber tube,
29: Dummy coil, 3: High voltage tower, 30: Terminal plate, 31: High voltage terminal, 32: Spring, 4:
Connector, 40 terminal, 5: resin insulating material, 5a: resin insulating material, 5b: resin insulating material, 6: plug cap, 3
02: cavity, 303: end molding portion, 304: winding portion molding portion, 301: ring gate, 300: spool raw material, 305: glass fiber, 307: film gate, 9: gap.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Atsushi Konishi             1-1, Showa-cho, Kariya city, Aichi stock market             Inside the company DENSO (72) Inventor Kazuhide Kawai             1-1, Showa-cho, Kariya city, Aichi stock market             Inside the company DENSO (72) Inventor Junichi Wada             1-1, Showa-cho, Kariya city, Aichi stock market             Inside the company DENSO

Claims (34)

[Claims] 1. A case, a rod-shaped core installed in the case, a cylindrical primary spool installed substantially coaxially on the outer peripheral side of the core in the case, and wound around the primary spool. A primary coil made of a wire rod, a cylindrical secondary spool installed substantially coaxially on the outer peripheral side of the core in the case, and a secondary coil made of a wire wound around the secondary spool. An insulating coil filled in the case, the secondary coil and the core and / or the secondary coil and the primary coil of the primary spool and the secondary spool. The spool in between is an ignition coil characterized by being made of a base resin having an adhesive strength to the resin insulation material of less than polybutylene terephthalate and a dielectric breakdown voltage exceeding polyphenylene sulfide. 2. A case, a rod-shaped core installed in the case, a cylindrical primary spool installed substantially coaxially on the outer peripheral side of the core in the case, and wound around the primary spool. A primary coil made of a wire rod, a cylindrical secondary spool installed substantially coaxially on the outer peripheral side of the core in the case, and a secondary coil made of a wire wound around the secondary spool. An insulating coil filled in the case, the secondary coil and the core and / or the secondary coil and the primary coil of the primary spool and the secondary spool. The spool between is an ignition coil characterized in that it is made of a base resin having an adhesion to the resin insulation material of less than polyethylene terephthalate and a dielectric breakdown voltage of more than polyphenylene sulfide. 3. The ignition coil according to claim 1, wherein the base resin is crystalline polystyrene. 4. The ignition coil according to claim 1, which is installed in a plug hole of a cylinder. 5. A case, a rod-shaped core installed in the case, a cylindrical primary spool installed substantially coaxially on the outer peripheral side of the core in the case, and wound around the primary spool. A primary coil made of a wire rod, a cylindrical secondary spool installed substantially coaxially on the outer peripheral side of the core in the case, and a secondary coil made of a wire wound around the secondary spool. An insulating coil filled in the case, the secondary coil and the core and / or the secondary coil and the primary coil of the primary spool and the secondary spool. The spool between is made of a base resin having an electrical insulating property even if a high voltage is generated in the secondary coil against the peeling generated between the resin insulating material and the spool. Ignition coil. 6. The crystalline polystyrene is an improved crystalline polystyrene whose linear expansion coefficient can be adjusted, and the linear expansion coefficient of the end portion of the spool made of the improved crystalline polystyrene is
When the linear expansion coefficient of the resin insulation material is 100%, 13
The ignition coil according to claim 3, which is 5% or less. 7. The improved crystalline polystyrene is formed by adding reinforcing fibers to crystalline polystyrene, and the reinforcing fibers are randomly or circumferentially oriented at the end portion of the spool. Item 6. The ignition coil according to item 6. 8. The ignition coil according to claim 7, wherein the reinforcing fiber is glass fiber, and the resin insulating material is epoxy resin. 9. A method of manufacturing an ignition coil having a spool, comprising: a winding part around which a wire is wound; and end parts arranged at both ends in the longitudinal direction of the winding part. A spool raw material preparation step of adding fibers to prepare a spool raw material, and injecting the spool raw material into the cavity through a gate arranged at a position facing the end molding portion of the cavity of the mold, and injecting the spool raw material Is cooled and hardened in the cavity, and the reinforcing fiber forms a spool material in which the reinforcing fibers are randomly or circumferentially oriented at the ends, and a portion of the spool material corresponding to the gate is cut. And a gate cutting step to perform the ignition coil manufacturing method. 10. The method for manufacturing an ignition coil according to claim 9, wherein the gate is a ring gate or a film gate. 11. A tube having a case, a rod-shaped core installed in the case, and a winding part around which a winding is wound, the coaxial core being installed on the outer peripheral side of the core in the case. -Shaped primary spool, a cylindrical secondary spool that is installed on the outer peripheral side of the core in the case substantially coaxially, and has a winding portion around which the winding is wound, and is filled in the case and cured. An ignition coil having a resin insulating material, wherein at least one of the primary spool and the secondary spool is an SPS spool having crystalline polystyrene as a base resin. . 12. The ignition coil according to claim 11, wherein the primary spool is the SPS spool. 13. The ignition coil according to claim 11, wherein the adhesive force of the base resin to the resin insulating material is less than 15 MPa. 14. The winding portion of the SPS spool,
A gap is defined between the winding wound around the winding portion and the resin insulating material that has penetrated and hardened, and the gap covers 70% or more of the surface area of the winding portion. The ignition coil according to claim 11, wherein the ignition coil is formed. 15. The gap is 90 times the surface area of the winding portion.
The ignition coil according to claim 14, wherein the ignition coil is formed over a range of not less than%. 16. The winding portion of the SPS spool,
A gap is defined between the winding and the resin insulating material that has penetrated between the windings and hardened, and the radial width of the gap is 0.01 mm or more. 1
The ignition coil according to 1. 17. The ignition coil according to claim 16, wherein the radial width of the gap is less than 0.3 mm. 18. The gap is 70 times the surface area of the winding portion.
The ignition coil according to claim 16, wherein the ignition coil is formed over a range of not less than%. 19. The gap is 90 times the surface area of the winding portion.
The ignition coil according to claim 16, wherein the ignition coil is formed over a range of not less than%. 20. The dielectric breakdown voltage of the base resin is JI
The ignition coil according to claim 11, which has a value of 15 kV / mm or more in the measuring method of S K 6911. 21. The ignition coil according to claim 11, wherein the case is made of a highly adhesive resin having a higher adhesiveness to the resin insulating material than the base resin. 22. A tube having a case, a rod-shaped core installed in the case, and a winding portion around which a winding is wound, the winding part being installed substantially coaxially with the core on the outer peripheral side of the core. -Shaped primary spool, a cylindrical secondary spool that is installed on the outer peripheral side of the core in the case substantially coaxially, and has a winding portion around which the winding is wound, and is filled in the case and cured. An ignition coil having the above-mentioned resin insulating material, and between the winding part of at least one of the primary spool and the secondary spool and the winding wound around the winding part. An ignition coil, wherein a gap is formed between the resin insulating material that has penetrated and hardened after the resin insulating material has hardened. 23. The ignition coil according to claim 22, wherein the spool adjacent to the gap is the primary spool. 24. The ignition coil according to claim 22, wherein the base resin forming the spool adjacent to the gap is crystalline polystyrene. 25. The gap has a surface area of 70 of the winding portion.
The ignition coil according to claim 22, wherein the ignition coil is formed so as to extend over at least%. 26. The gap is 90 times the surface area of the winding portion.
The ignition coil according to claim 25, wherein the ignition coil is formed so as to extend over at least%. 27. The radial width of the gap is 0.01 mm
The ignition coil according to claim 22, which is the above. 28. The ignition coil according to claim 27, wherein a radial width of the gap is less than 0.3 mm. 29. The gap is 70 times the surface area of the winding portion.
The ignition coil according to claim 27, wherein the ignition coil is formed so as to extend over at least%. 30. The gap is 90 times the surface area of the winding portion.
The ignition coil according to claim 27, wherein the ignition coil is formed so as to extend over at least%. 31. The dielectric breakdown voltage of the base resin forming the spool adjacent to the gap is 15 kV / mm or more according to the measuring method of JIS K6911.
The ignition coil according to 2. 32. The ignition coil according to claim 22, wherein a dielectric breakdown voltage of a base resin forming a spool adjacent to the gap is 15 kV / mm or more in a measuring method of actually measuring the spool itself. 33. The adhesive force of the base resin forming the spool adjacent to the gap to the resin insulating material is 15M.
The ignition coil according to claim 22, wherein the ignition coil is less than Pa. 34. A tube having a case, a rod-shaped core installed in the case, and a winding portion around which a winding is wound, the winding part being installed substantially coaxially on the outer peripheral side of the core. -Shaped inner spool and a winding portion around the outer periphery of the core in the case, which are substantially coaxial with each other, have a winding portion around which the winding is wound. A method for manufacturing an ignition coil, comprising: a cylindrical outer spool having a low outer peripheral surface; and a resin insulating material filled and cured in the case, the method comprising: Insulating material filling step of filling resin insulating material, insulating material gelling step of gelling the filled resin insulating material at high temperature, and insulating material cooling the gelled resin insulating material together with the case and the outer spool And a cooling step, Method of manufacturing that the ignition coil.