JP2003229319A - Ignition coil for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ignition coil for an internal combustion engine capable of alleviating heat stress and improving reliability. <P>SOLUTION: A center core, a secondary coil wound on a secondary bobbin, a primary coil wound on a primary bobbin in turn from the inside in a coil case are arranged. A peeling layer is provided between a center core and the secondary bobbin, in the ignition coil for the internal combustion engine with an insulating resin filled between these components. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an ignition coil for an internal combustion engine. In particular, the present invention relates to an independent ignition type ignition coil for an internal combustion engine, which is attached to each spark plug of an engine and is directly connected to each spark plug for use.

[0002]

2. Description of the Related Art An ignition coil for an internal combustion engine is disclosed in Japanese Patent Laid-Open No.
No. 0-92670, JP-A No. 11-243023, JP-A No. 11-354345, and JP-A 2000-
It is described in JP-A-91144 and JP-A-2000-228322.

[0003]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
The elastic member between the next bobbins is that the pencil coil (independent ignition coil in the plug hole) is exposed to severe temperature environment (heat stress of about -40 ° C to 130 ° C). thermal stress due to difference in linear expansion coefficient between the members is because the work, in particular, the linear expansion coefficient of the center core (13 × 10 ^-6) and the linear expansion coefficient of the insulating resin (40
^{X10 -6} ) is large, and excessive thermal stress acts, and when a normal insulating resin (hard epoxy resin composition instead of the elastic member) is used, the insulating resin is cracked. This is because there is a concern that this may occur and dielectric breakdown may occur. To cope with such thermal stress, an elastic member having elasticity that is excellent in stress absorption is used. However, a pencil coil, whose coil part is inserted in the plug hole, does not have enough space, and the elastic member layer may not be removed sufficiently. The secondary bobbin causes a crack due to the circumferential stress.

The object of the present invention is to further reduce thermal stress,
An object of the present invention is to provide an ignition coil for an internal combustion engine that can improve reliability.

[0005]

In order to sufficiently reduce the thermal stress applied to the secondary bobbin, a peeling layer is provided between the center core and the secondary bobbin. For example, by providing the release layer between the center core and the elastic member, slippage between the center core and the elastic member occurs, and the stresses acting on each other can be canceled, and the stress applied to the secondary bobbin from the center core side can be relaxed.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION An independent ignition type ignition coil is called an in-plug mounting type because at least a part of the coil portion is introduced into the plug hole and mounted, and the coil portion has a plug hole. Since it is inserted into the inside, it is commonly referred to as a pencil-shaped slender pencil coil. Inside the slender cylindrical coil case, a center core (one in which a number of silicon steel plates are laminated with a magnetic path core), a primary coil, and a secondary coil are installed. ing. The high voltage required for ignition is generated in the secondary coil by controlling the energization and interruption of the current flowing in the primary coil. These coils are usually wound around their respective bobbins and are concentrically formed around the center core. It is arranged.

The bobbins are polybutylene terephthalate,
It is formed of a thermoplastic resin such as PPS or modified PPO, and a coil which is a copper wire is wound around it. Inside the secondary bobbin, a center core in which silicon steel plates are laminated, an elastic member is arranged between the center core and the secondary bobbin, and an insulating resin is cast between the respective constituent members. Therefore, since the metal and the resin are adjacent to each other, the difference in linear expansion coefficient is likely to be large.

Embodiments will be described below with reference to the drawings.

FIG. 1 is a sectional view showing the structure of an ignition coil for an internal combustion engine which is an embodiment.

Inside the elongated cylindrical case (exterior case) 6, from the center (inside) to the outside, the center core 5,
A secondary coil 3 wound around a secondary bobbin 4 and a primary coil 1 wound around a primary bobbin 2 are arranged concentrically. These components are filled with the thermosetting insulating resin 14 after being inserted into the outer case 6. A side core 7 that forms a magnetic path with the center core 5 is attached to the outside of the outer case 6.

The side core 7 is formed by rolling a thin silicon steel plate having a thickness of about 0.2 to 0.5 mm or a grain-oriented silicon steel plate into a tubular shape and stacking one to four sheets. However, in order to prevent short circuit of one turn of magnetic flux, at least 1 on the circumference of the side core 7
There are cuts at some places.

The center core 5 is made of a silicon steel plate or a grain-oriented silicon steel plate having a plate thickness of 0.2 to 0.7 mm. The center core 5 is close to a cylindrical shape so as to increase its cross-sectional area. For example, the width and length are set in several stages. A number of silicon steel plates are laminated by pressing. Although not shown here, one end surface of the center core 5 in the axial direction,
Alternatively, magnets may be provided on both end faces to apply a magnetic flux opposite to the magnetic flux generated by the coil to create a state in which a core having a high magnetic flux density is used to increase the magnetic energy.

An elastic member 8 (for example, silicone rubber) for absorbing stress is provided at the end (the upper end or the lower end) of the center core 5, and an elastic member 15 is also provided around the center core 5, and the secondary bobbin 4 and the center core 5 are provided. The thermal stress (stress caused by the difference in the coefficient of linear expansion) generated between them is relaxed. The elastic member 15 is made of heat-resistant silicone rubber (flexible epoxy resin in this example) or the like. A flexible epoxy resin has a glass transition temperature of room temperature (2
(0 ° C.) or lower, and an epoxy resin having elastic and soft properties (elastomer) at a glass transition point or higher,
For example, a mixture of epoxy resin and modified aliphatic polyamine.

The primary bobbin 2 contains polybutylene terephthalate (PBT) or polyphenylene oxide (modified PP) containing 20% by weight or more of an inorganic filler in order to secure mechanical strength.
O), or polyphenylene sulfide (PPS)
The primary coil 1 formed of a thermoplastic synthetic resin such as, and wound on the primary bobbin 2 is an enamel wire having a wire diameter of about 0.3 to 1.0 mm, which is tens to hundreds of times per layer. It is a winding in which several layers are wound 100 to 300 times in total.

The secondary bobbin 4 is also formed of a thermoplastic synthetic resin such as modified polyphenylene oxide (modified PPO) or polyphenylene sulfide (PPS) in which an inorganic substance is mixed in an amount of 20% by weight or more, more preferably 30% by weight or more. . The secondary bobbin 4 has a cylindrical shape with a bottom, and is installed in the secondary bobbin 4 so that the stress absorbing elastic member 8 and the center core 5 are received by the bottom portion of the secondary bobbin.

The secondary bobbin 4 is also interposed between the center core 5 and the secondary coil 3 and also serves to insulate the high voltage generated in the secondary coil 3. In order to insulate the high voltage generated in the secondary coil 3, the thickness of the secondary bobbin 4 is set to 0.5 to 1.5 mm, and electric field concentration and stress concentration between the secondary coil 3 and the center core 5 are prevented. In order to do so, the elastic member 15 is injected into the center bobbin 5 on the inner peripheral side of the secondary bobbin 4, and is cured and fixed. In this embodiment, the peeling layer 22 is provided between the center core 5 and the elastic member 15. This point will be described later with reference to FIGS. 2, 3 and 4.

The secondary coil 3 has a wire diameter of 0.03 to 0.06 mm.
A total of 10,000 to 30,000 using approximately enamel wire
About a number of times, a plurality of collars 4a arranged on the secondary bobbin 4 are divided and wound in a multilayer structure.

The insulating resin 14 includes a secondary coil 3 wound around a secondary bobbin 4 and a primary coil 1 wound around a primary bobbin 2.
Is inserted in the outer case 6, and the igniter unit 19
Is supplied and the terminal 19a of the igniter unit is welded and fixed to the connector terminal 21, and then injected in a vacuum state. Then, the insulating resin 14 is cured by heating, so that the insulating property and the mechanical strength can be secured.

The igniter unit 19 includes a power element (semiconductor chip) and an electronic circuit section such as a current limiting circuit.
It is built into chips and is externally molded with epoxy resin. In this embodiment, the IG is used as a power element.
BT (Insulated Gate Bipolar Transistor) is adopted so that it can be driven with a low current of 2 mA to 10 mA. Further, by forming one chip as described above, it is possible to significantly reduce the cost by simplifying the manufacturing process.

The outer case 6 is made of a thermoplastic synthetic resin such as polyphenylene sulfide (PPS) and accommodates and fixes the coil portion so that the insulating resin 14 can be cast.

13 is a high-voltage diode for preventing premature ignition, 1
Reference numeral 2 is an ita spring, 11 is a high-voltage terminal, 9 is a spring for connecting a spark plug, and 10 is a plug seal (silicone rubber) for connecting a spark plug. Reference numeral 18 is a cover for improving the appearance, and is attached to the casting surface of the insulating resin 14. A plug hole seal 16 is attached to the fitting portion between the connector case 17 and the outer case 6 to prevent water from entering the plug hole. Reference numeral 20 denotes a noise preventing capacitor, in which a ceramic type capacitor with a lead is arranged upside down and the lead is connected and fixed to the connector terminal 21 by welding.

Next, the provision of the release layer 22 between the center core 5 and the elastic member 15 will be described in detail with reference to FIGS. 2, 3 and 4.

When the ignition coil tries to thermally contract due to the temperature drop after the engine is stopped, the linear expansion coefficient becomes large.
The next bobbin 4 (about 30 × 10 ⁻⁶ ) contracts, but the center core 5 (about 13 × 10 ⁻⁶ ) having a small linear expansion coefficient has a small contraction. An expanding force acts in the circumferential direction from the side of the center core 5 due to thermal contraction (difference in linear expansion coefficient). Further, a tensile force in the circumferential direction relatively acts from the primary coil 1 and secondary coil 3 side via the insulating resin, and a large internal stress σ is generated in the secondary bobbin 4 due to their synergistic effect. However, in the present embodiment, the expansion force in the circumferential direction acting on the secondary bobbin 4 from the side of the center core 5 is applied to the peeling layer 22 between the center core 5 and the elastic member 15.
By providing, the center core 5 and the elastic member 15 slip, and the stresses acting on each other can be canceled.
The thermal stress applied to the inside of the secondary bobbin 4 can be reduced (relaxed).

Therefore, of the stress σ generated in the secondary bobbin, the total stress σ is reduced by reducing the thermal stress σ ₁ generated in the secondary bobbin 4 due to the thermal contraction of the center core 5 and the secondary bobbin 4. Will be possible. CAE
According to the (Computer Aided Engineering) analysis result (FIG. 4), it is possible to reduce (relieve) the overall internal stress σ by about 10% by reducing the stress component σ ₁ . Further, when the thermal shock resistance of the sample product provided with the release layer 22 was evaluated, it was confirmed that the life was improved by about 20%.

Another example is shown in FIG. If the peeling layer 22 is between the center core 5 and the secondary bobbin 4, the stress is relieved, so that the same effect as described above can be obtained.

In FIG. 5 (a), the center core 5 is covered with a tape 23 containing silicone, fluorine or the like as a main component, and the tape 2
A peeling layer 22 is provided between the elastic member 15 and the elastic member 15.

In FIG. 5 (b), the inner surface of the secondary bobbin 4 is coated with silicone, fluorine or the like as a main component.
A peeling layer is provided between the next bobbin 4 and the elastic member 15.

With the structure as described above, it is possible to achieve high quality and high reliability in an independent ignition type ignition coil which is exposed to a severe temperature environment.

[0029]

According to the present invention, it is possible to provide an ignition coil for an internal combustion engine which can further reduce thermal stress and improve reliability.

[Brief description of drawings]

FIG. 1 is a sectional view of an ignition coil for an internal combustion engine of the present invention.

2 is a cross-sectional view taken along the line AA of FIG.

FIG. 3 is a partial cross-sectional view of FIG.

FIG. 4 CAE analysis results.

FIG. 5 is a cross section of another example.

[Explanation of symbols]

1 ... Primary coil, 2 ... Primary bobbin, 3 ... Secondary coil, 4
... secondary bobbin, 4a ... tsuba, 5 ... center core, 6 ... exterior case, 7 ... side core, 8 ... stress absorbing elastic member, 9 ...
Spring, 10 ... Plug seal, 11 ... High voltage terminal, 1
2 ... Ita spring, 13 ... High voltage diode, 14 ... Insulating resin (epoxy resin), 15 ... Elastic member (flexible epoxy resin), 16 ... Plug hole seal, 17 ... Connector case, 18 ... Cover, 19 ... Igniter unit 1
9a ... Unit terminal, 20 ... Noise prevention capacitor, 21
... connector terminals, 22 ... release layer, 23 ... tape.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Manabu Hashimoto             Hitachinaka City, Ibaraki Prefecture 2520 Takaba             Ceremony Company Hitachi Ltd. Automotive equipment group F-term (reference) 3G019 KC04 KC06

Claims (7)

[Claims] 1. An independent ignition type ignition coil for an internal combustion engine which is inserted into a plug hole of an internal combustion engine and directly connected to each ignition plug for use, wherein a center core and a secondary bobbin are arranged in a coil case in order from the inside. An internal combustion engine ignition coil in which a wound secondary coil and a primary coil wound around a primary bobbin are concentrically arranged, and an insulating resin is filled between these constituent members, wherein An ignition coil for an internal combustion engine, characterized in that a peeling layer is provided between the next bobbins. 2. An ignition coil for an internal combustion engine according to claim 1, wherein an elastic member having elasticity exists between the center core and the secondary bobbin, and a peeling layer is provided between the center core and the elastic member. 3. The coating according to claim 2, wherein the center core is coated with silicone or fluorine,
An ignition coil for an internal combustion engine, characterized in that a peeling layer is formed. 4. The ignition coil for an internal combustion engine according to claim 1, wherein the center core is covered with a tape or the like that causes a peeling action, and a peeling layer is provided between the tape and the elastic member. 5. An ignition coil for an internal combustion engine according to claim 1, wherein the inner surface of the secondary bobbin is coated with a peeling action, and a peeling layer is provided between the secondary bobbin and the elastic member. 6. An ignition coil for an internal combustion engine according to claim 2, wherein a flexible epoxy resin is used for an elastic member between the center core and the secondary bobbin. 7. An elastic member between the center core and the secondary bobbin
The ignition coil for an internal combustion engine according to claim 2, 3, 4, or 5, wherein a rubber having a heat resistance of 30 ° C or higher is used.