JP2000252040A - Coil-incorporated spark plug - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a coil-incorporated spark plug having no large loss of a supply voltage to a spark plug part accompanying leakage of magnetic flux, having a closed magnetic path allowing a superior spark discharge, and allowing miniaturization. SOLUTION: This spark plug comprises an ignition coil part 32 and an ignition plug part 11, non-rotatably integrated together. The ignition coil part 32 includes a coil core 31 made of ferromagnetic material having a center core part 31a wound with both a primary coil 19 and a secondary coil 21, and an outer core part 31b disposed outside the center core part 31a, while the ignition plug part 11 includes both an insulator 13 having an axial hole 14 through which a center electrode 15 is inserted and a main metal fitting 16 fitting on the insulator 13. The coil core 31 and the main metal fitting 16 form a closed magnetic path. Thereby, leakage of magnetic flux at the time of inducing the magnetic flux by a primary current can be reduced to realize miniaturization and generate a high voltage in the secondary coil 21. Accordingly, a loss of the supply voltage to the ignition plug part 11 is small, the voltage with sufficient energy can be supplied to the ignition part 11, and an excellent, stable spark discharge can be always performed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coil-integrated spark plug in which both an ignition coil unit and a spark plug unit attached to an internal combustion engine are non-rotatably integrated.

[0002]

2. Description of the Related Art In recent years, there has been a tendency to effectively secure a space in an engine room because many accessories (electrical components) are mounted in an engine room as the performance of automobiles increases. . Therefore, the installation space of the internal combustion engine is required to be reduced, and the internal combustion engine itself is also required to be downsized. Therefore, the ignition coil unit and the ignition plug unit attached to the internal combustion engine are attached separately from each other,
The conventional method of connecting the both using a high tension cord or the like hinders a measure for securing a space in the engine room.

[0003] In view of the above, conventionally, an ignition plug portion comprising an insulator having a shaft hole and a center electrode inserted in the shaft hole, and a metal shell formed by fitting the insulator, There has been proposed a coil-integrated ignition plug in which an ignition coil unit provided with voltage generating means (primary coil, secondary coil, coil core, etc.) for supplying a high voltage to the ignition plug unit is directly non-rotatably integrated. I have. In the coil-integrated ignition plug in which the ignition coil portion and the ignition plug portion are integrated as described above, it is not necessary to connect the both using a high tension cord or the like, and the number of parts can be reduced.
Further, it is possible to prevent adverse effects such as poor ignition caused by insulation deterioration of the high tension cord. In addition, a mechanical distributor such as a distributor can be eliminated, the number of components can be reduced, and furthermore, it is possible to prevent adverse effects of radio noise on the internal combustion engine, electrical components, and the like.

[0004]

The conventional coil-integrated spark plug has a configuration in which a coil core is provided in an ignition coil portion. However, the shape of the coil core is various and not constant. Is a coil core constituting an open magnetic circuit (hereinafter referred to as an open magnetic circuit coil core). Therefore, in the case of a coil-integrated spark plug having an open-magnetic-path coil core, the outside of the coil core (in air)
Is used as a magnetic path, the magnetic resistance increases. Therefore, there is a concern that leakage of magnetic flux may occur, causing a loss in the supply voltage to the ignition plug. That is,
In the conventional coil-integrated spark plug, the magnetic path is not sufficiently considered, and it is hard to say that it has excellent magnetic properties.

Therefore, as shown in FIG.
No. 3,780, proposes a coil-integrated spark plug 1 in which a coil core 4 (hereinafter, referred to as a closed-magnetic-path coil core) that forms a closed magnetic circuit is disposed in an ignition coil unit 2. In the above-mentioned publication technology, since the closed magnetic path coil core 4 is provided in the ignition coil section 2, the magnetic path is
It is formed by When a magnetic flux is generated in the coil-integrated ignition plug 1, the magnetic flux does not pass through the outside of the coil core 4 (in the atmosphere), so that the occurrence of the leakage of the magnetic flux can be reduced. As a result, the loss of the supply voltage to the ignition plug unit 3 due to the leakage magnetic flux is small, and it is possible to perform a good spark discharge.

However, the closed magnetic circuit type coil core 4 disposed in the ignition coil section 2 is usually provided with two sets of U-shaped coils or E-shaped coils (not shown) facing each other as in the above-mentioned publication. It is configured by combining a U-shaped coil and an I-shaped coil. Therefore, when compared with an open-magnetic-path coil core formed by a pair of I-shaped coils or T-shaped coils and a coil-integrated spark plug arranged in the ignition coil section, the space of the ignition coil section 2 is designed to be larger. I can't help but. That is, in the coil-integrated ignition plug 1 in which the ignition coil unit 2 is provided with the closed magnetic circuit type coil core 4 having excellent magnetic characteristics, the coil-integrated ignition plug 1 may be increased in size, and the size of the ignition plug 1 itself may be reduced. Therefore, it is difficult to reduce the space in the internal combustion engine.

Further, as shown in FIG.
No. 984 proposes a coil-integrated spark plug 5 in which a closed magnetic path formed by a combination of a coil core 8 and a cylinder 9 formed of a ferromagnetic material is arranged in an ignition coil section 6. According to the above publication, a closed magnetic path is provided by a combination of a coil core 8 and a cylinder 9 formed of a ferromagnetic material.
As in Japanese Patent Publication No. 0, the loss of the supply voltage to the ignition plug portion 7 due to the leakage magnetic flux is small, and it is possible to perform a good spark discharge.

[0008] However, even in the above publication technology,
A coil-integrated spark plug 5 in which a closed magnetic path is formed in advance by combining a coil core 8 and a cylinder 9 formed of a ferromagnetic material, and the closed magnetic path is arranged in an ignition coil section 6. There is a limit to miniaturization. That is,
Even in the coil-integrated spark plug 5 having the closed magnetic circuit having the above-described configuration in the ignition coil unit 6, the magnetic characteristics are excellent, but the closed magnetic circuit is formed separately from the ignition plug unit. Is formed and then integrated with the spark plug part, so that the coil-integrated spark plug is configured to extend in the vertical direction (vertical direction in the figure), which is not suitable for miniaturization. It can be said.

Further, as disclosed in Japanese Utility Model Laid-Open Publication No. 64-32464, an ignition transformer having a primary coil and a secondary coil wound around a closed magnetic circuit type coil core is miniaturized by being embedded in an insulator and a metal shell. However, it is practically difficult to embed such an ignition transformer in the insulator and the metal shell, and to process the insulator and the metal shell in such a manner. As such, it is hard to say that it is excellent in terms of manufacturing cost and manufacturing efficiency.

The present invention has been made in view of the above-mentioned problems, and has a small loss of a supply voltage to a spark plug portion due to leakage of magnetic flux, and can perform a good spark discharge. It is an object of the present invention to provide a coil-integrated spark plug which has a closed magnetic circuit in the coil-integrated spark plug and which can sufficiently satisfy the requirement for miniaturization.

[0011]

Means for Solving the Problems, Functions, and Effects To achieve the object, a coil-integrated spark plug according to the present invention comprises:
An ignition coil portion including a coil core made of a ferromagnetic material having a central core portion wound with a primary coil and a secondary coil and an external core portion located outside the central core portion; An ignition plug having an insulator in which a center electrode is inserted in the shaft hole, and a metal shell for fitting the insulator, wherein the ignition coil and the ignition plug are provided. Are integrated so as not to rotate, and a closed magnetic path is formed by the coil core of the ignition coil portion and the metal shell of the ignition plug portion.

A point to be noted in the present invention is that, by integrating the ignition coil portion and the ignition plug portion, a closed magnetic path is formed by the coil core of the ignition coil portion and the metal shell of the ignition plug portion. is there.

In this configuration, since a closed magnetic path is formed by the coil core and the metallic shell, when a low voltage (primary voltage) is sent to the primary coil wound around the central core portion of the coil core and a primary current flows, the coil core And a magnetic flux is generated in the closed magnetic path composed of the metal shell. At this time, in the closed magnetic path, unlike the open magnetic path type coil core, the magnetic flux does not pass through the outside of the coil core (in the atmosphere), so that the magnetic resistance can be reduced. Therefore, since leakage of magnetic flux when magnetic flux is induced by the primary current can be reduced, a high secondary coil voltage (secondary voltage) can be generated despite its small size. As a result, it is possible to supply a voltage (secondary voltage) having sufficient energy to the ignition plug portion with little loss of the voltage supplied to the ignition plug portion, and to always perform a good and stable spark discharge. it can.

Further, in such a configuration, unlike the related art, when forming a coil-integrated ignition plug having a closed magnetic path, the ignition coil section is provided with a closed magnetic path in advance and combined with the ignition plug section to be integrated. There is no need. That is, in the present invention, a closed magnetic circuit is formed only by integrating the ignition coil unit and the ignition plug unit. Therefore, since the closed magnetic path is formed by using the metal shell without disposing the closed magnetic path in the ignition coil section in advance, not only the space of the ignition coil section can be reduced, but also the compactness while having the closed magnetic path is provided. Thus, it is possible to provide a coil-integrated spark plug that satisfies the requirements for compactness. Furthermore, since it is possible to form a closed magnetic circuit simply by integrating the ignition coil unit and the ignition plug unit in a non-rotatable manner by joining or the like,
In terms of manufacturing cost and manufacturing efficiency, it is very excellent.

Further, in the coil-integrated spark plug, an outer core portion forming a coil core may be formed in a substantially cylindrical shape, and the outer core portion may form a part of a casing of the ignition coil portion. .

In this configuration, the coil core is formed by the central core portion and the cylindrical outer core portion located outside the central core portion, and a closed magnetic path is formed by a combination of the coil core and the metal shell. It is possible to provide a coil-integrated spark plug that is excellent in magnetic properties despite its small size. Further, since the cylindrical outer core portion forms (substitutes) a part of the casing of the ignition coil portion, it is not necessary to store the coil core in a metal casing or the like. Therefore, the coil core of the present invention forms a closed magnetic circuit and also forms a casing, so that a smaller coil-integrated spark plug can be realized.

Further, in the coil-integrated spark plug, a part of the central core may be inserted into a shaft hole of the insulator.

[0018] With this configuration, it is possible to reduce the portion of the closed magnetic path formed by the coil core and the metal shell, which serves as a break in magnetic flux. Thus, it is possible to make it difficult to cause leakage of the magnetic flux generated in the closed magnetic circuit by the primary current. As a result, in the coil-integrated spark plug of the present invention, it is possible to further reduce the leakage magnetic flux, and it is possible to efficiently perform spark discharge.

Further, in the coil-integrated ignition plug, it is preferable that at least a part of a center electrode of the ignition plug part is formed of a ferromagnetic material and also forms a part of the closed magnetic circuit.

In this configuration, at least a part of the center electrode of the ignition plug can form a part of the closed magnetic path together with the coil core and the metal shell, so that a portion where a magnetic flux breaks in the closed magnetic path is minimized. Can be reduced. This makes it possible to minimize the leakage of the magnetic flux generated in the closed magnetic circuit by the primary current. as a result,
ADVANTAGE OF THE INVENTION In the coil-integrated ignition plug of this invention, a leakage magnetic flux can be suppressed to the minimum, and more efficient and favorable and stable spark discharge can be performed.

Further, in the coil-integrated spark plug, the closed magnetic path may have at least one magnetic flux saturation gap.

The closed magnetic path according to the present invention varies depending on the coil core and the metallic shell constituting the closed magnetic path and the ferromagnetic material of the center electrode. However, the maximum value of the magnetic flux density on the hysteresis characteristic (hereinafter referred to as the maximum) Magnetic flux density). Therefore, when the magnetic flux generated in the closed magnetic circuit by the primary current reaches the maximum magnetic flux density on the hysteresis characteristic, the change of the magnetic flux stops, and the coil core loses its function as an inductor and functions as an electric resistance. There is a concern that it will only be. That is, in a coil-integrated spark plug having a closed magnetic circuit, if the magnetic flux generated in the closed magnetic circuit by the primary current reaches the maximum magnetic flux density, the magnetic flux does not change effectively and magnetic saturation occurs. That is, an overcurrent is generated so as to cancel the magnetic flux induced by the primary current. As a result, high voltage (secondary voltage) boosted from the secondary coil
Cannot be obtained sufficiently, so that good spark discharge cannot be performed in the spark plug portion, and in an extreme case, there is a risk that a misfire may occur.

Therefore, in the present invention, at least one or more magnetic flux saturation gap is formed in a closed magnetic circuit formed by the coil core, the metal shell, and the center electrode. Specifically, since the ignition plug portion has an insulator for insulating a high voltage (secondary voltage) applied from the ignition coil portion, the thickness of the insulator is large. To form a magnetic flux saturation gap.
This makes it possible to intentionally limit the maximum value of the magnetic flux density to around the value of the maximum magnetic flux density determined on the basis of the hysteresis characteristic. As a result, in the coil-integrated spark plug having the closed magnetic circuit of the present invention, a change in magnetic flux generated in the closed magnetic circuit by the primary current can be effectively secured, and a good and stable spark discharge is always generated in the spark plug section. It can be carried out. It is desirable that the thickness of the insulator be as thin as possible while having a thickness in a range allowed for the withstand voltage.

Next, the coil-integrated spark plug is
It is more effective when attached to a gas engine that uses gaseous fuel as fuel.

Since gaseous fuel has higher insulating properties than gasoline, which is liquid fuel, a gas engine using gaseous fuel has a relatively high discharge voltage. More specifically, the discharge voltage at the ignition plug in a gas engine is 30 to 40% higher than that in a gasoline engine. In addition, in order to cause a spark at the spark plug, the power supply voltage supplied for spark discharge must be higher than the discharge voltage. It is necessary that the supplied voltage has no loss.

Therefore, by mounting the coil-integrated spark plug of the present invention, which can reduce the leakage magnetic flux and can supply the voltage supplied for spark discharge without losing it, to the gas engine, a high discharge voltage can be obtained. Even with a required gas engine, the voltage supplied for spark discharge can always be supplied higher than the discharge voltage, and high-efficiency, good and stable spark discharge can always be provided.

[0027]

(Embodiment 1) Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a coil-integrated spark plug 100 according to an embodiment of the present invention.
FIG. The coil-integrated ignition plug 100 has a configuration in which the ignition coil section 11 and the ignition plug section 12 are integrated.

The ignition plug portion 11 constituting one of the coil-integrated ignition plugs 100 includes a ceramic insulator 13 having a shaft hole, a metal center electrode 15 inserted in the shaft hole 14, And a cylindrical metal shell 16 to which the body 13 is fitted. The metal shell 16 is formed of a ferromagnetic material, specifically, a mild steel (carbon steel) or the like to form a part of a closed magnetic circuit as described later. Further, the metal shell 16 has a caulked portion 16a which is caulked in an approximately R shape inward with an inorganic powder 28 such as talc powder interposed therebetween in order to prevent the insulator 13 from coming off, and is adjacent to the caulked portion 16a. A substantially cylindrical main body 16b having a large diameter, and a screw (male screw) for attachment to an internal combustion engine (cylinder head) are formed, and a screw 16c formed smaller in diameter than the main body 16b. It is configured. Further, a single-pole ground electrode 17 is fixed to the tip of the metal shell 16. The tip of this ground electrode 17 is
5 so as to form a predetermined discharge gap with the center electrode 1.
5 and is bent back into a substantially L-shape.

Next, the ignition coil section 12 which constitutes the other of the coil-integrated ignition plug 100 according to the present embodiment will be described. The ignition coil unit 12 has a central core 1
A coil core 18 composed of an E-shaped coil having an outer core portion 18b located substantially parallel to both sides of the center core portion 18a is provided. As the coil core 18 of the present embodiment, a coil core formed by laminating silicon steel plates, which are ferromagnetic materials, is used. In the present embodiment, the coil core 18 is formed of an E-shaped coil. For example, the coil core 18 is formed by combining a U-shaped coil and an I-shaped coil formed by laminating silicon steel plates in an E-shape. A thing may be used. Further, the central core portion 18
In a, a primary coil 19 wound on a primary bobbin 20 and a secondary coil 21 wound on a secondary bobbin 22
Are wound coaxially. Note that a part of the central core portion 18a is configured to be inserted (inserted) into the shaft hole 14 of the insulator 13 of the ignition plug portion 11.

The primary coil 19 wound around the coil core 18 and the central core portion 18a constituting the coil core 18
The secondary coil 21 is housed in a metal-made, specifically, iron-made, cylindrical casing 23.
The reason for housing the casing 23 using the casing 23 is as follows.
The reason for this is that defects such as chipping and cracks do not occur in the substrate 8. The outer diameter of this casing 23 is
The metal shell 16 is formed to have substantially the same outer diameter as the main body 16 b of the metal shell 16, and to have a size to be in contact with the coil core 18. Then, the tip 23a of the casing 23
Is formed in a planar shape, and as described later, the metal shell 1
6 and the upper surface of the main body 16b. The coil core 18 and the contact portion 24 of the metal shell 16 are joined by welding or brazing. And
The inside of the casing 23 is molded by using a resin material 26 (epoxy resin or the like) having excellent insulation and heat resistance in order to improve insulation.

A hexagon nut 23b for engaging a tool such as a spanner or a wrench when the metal shell 16 is mounted on the internal combustion engine (cylinder head) is formed on the upper portion of the casing 23. Further, the primary coil 1 is passed through a cable 27 penetrating the hexagon nut portion 23b.
9, a high voltage (secondary voltage) generated by the secondary coil 21 is supplied to an output terminal 25 connected to a cable 27b for transmitting the secondary voltage. It is configured to be supplied to

Next, the integration of the ignition plug section 11 and the ignition coil section 12 according to the present embodiment will be described. First, a coil core 18 made of an E-shaped coil is formed, and a primary bobbin 20 in which a primary coil 19 is wound and a secondary bobbin 22 in which a secondary coil 21 is wound around a central core portion 18a constituting the coil core 18. Is wound coaxially. Next, the ignition plug part 11 is arranged,
The output terminal 25 connected to the cable 27b extending from the secondary coil 21 is brought into contact with (connected to) the center electrode 15 of the ignition plug portion 11, and the coil core 18 and the metal shell 16
And abut. Then, the contact portion 24 is joined by welding or brazing. Then, the coil core 18
A casing 23 for accommodating the spark plug 11 is provided.
The casing 23 is inserted until the casing 23 comes into contact with the upper surface of the body 16b. The contact portion 24 between the distal end 23a of the casing 23 and the upper surface of the main body 16b of the metal shell 16 is joined by resistance welding, laser welding, or the like. At this time, the tip portion 23a of the casing 23 and the main body portion 16 of the metal shell 16 are
b may be joined in a state where it is pressed against. Further, a resin material 26 having excellent insulation and heat resistance is filled from a part of the casing 23 in a softened state until the space inside the casing 23 (coil core 18) is filled, and the resin material 26 is cured to form a casing. 23 is molded.

By thus integrating the ignition plug portion 11 and the ignition coil portion 12, the coil-integrated ignition plug 100 forms a closed magnetic path by the coil core 18 and the metal shell 16. Therefore, in the coil-integrated ignition plug 100, when a low voltage is sent to the primary coil 19 of the ignition coil section 12 and a primary current flows, a magnetic flux Φ is generated in a closed magnetic path formed by the coil core 18 and the metal shell 16. The magnetic flux Φ forms a magnetic path as shown in FIG. 2, and the magnetic flux Φ does not pass through the outside of the coil core 18 (in the atmosphere), so that the magnetic resistance can be reduced. As a result, the leakage of the magnetic flux Φ when the magnetic flux is induced by the primary current is small, and a high voltage (secondary voltage) of the secondary coil 21 can be generated. The loss of the voltage supplied to the electrode 15 can be reduced, and a good and stable spark discharge can be performed in the discharge gap of the spark plug section 11.

Further, in the coil-integrated spark plug 100 of the present embodiment, the closed magnetic path is
Since it is formed by a combination of the metal shell 8 and the metal shell 16, there is no need to arrange a closed magnetic path in the ignition coil section in advance and integrate it with the ignition plug section. That is, it is possible to provide the coil-integrated ignition plug 100 that not only can reduce the space of the ignition coil section 12 but also has a closed magnetic circuit and satisfies downsizing.

When a closed magnetic circuit is provided as in the coil-integrated ignition plug 100 of the present embodiment, the hysteresis characteristic varies depending on the ferromagnetic material of the coil core 18 and the metal shell 16 constituting the closed magnetic circuit. Above, the maximum value of the magnetic flux density (hereinafter, referred to as the maximum magnetic flux density) is determined. Therefore, the magnetic flux generated in the closed magnetic circuit by the primary current reaches the maximum magnetic flux density, the magnetic flux does not change effectively, magnetic saturation occurs, and an overcurrent is generated to cancel the magnetic flux induced by the primary current. There is a risk that it will. Therefore, the coil-integrated spark plug 10 of the present embodiment is
At 0, a magnetic flux saturation gap is formed in a closed magnetic path formed by the coil core 18 and the metal shell 16. Specifically, the magnetic flux saturation gap 29 is formed (substituted) with the thickness of the insulator 13 of the ignition plug portion 11. By forming the magnetic flux saturation gap 29 in this manner,
The maximum value of the magnetic flux density is restricted near the value of the maximum magnetic flux density on the hysteresis characteristic, and the change of the magnetic flux generated when the primary current flows through the primary coil 19 is effectively secured. In addition, the thickness of the insulator 13 is such that the ignition plug portion 11 can withstand a withstand voltage.

In the above-described embodiment, since a silicon steel sheet having poor impact resistance is used as the coil core 18, the coil core 18 is stored in the metal casing 23 in order to prevent defects such as chipping and cracking of the coil core 18. After that, a coil-integrated spark plug is formed (see FIG. 1).
As shown in FIG. 3, a threaded recess 28 is formed in a part of the upper surface of the main body 16 b of the metal shell 16 without using a metal casing, and insulation is provided so as to fill the recess 28. The coil-integrated spark plug 200 may be molded with a resin material 26 having excellent heat resistance and heat resistance and integrated so as not to rotate. In such a coil-integrated spark plug 200, it is not necessary to use a metal casing, so that the number of manufacturing steps is reduced and it is possible to contribute to cost reduction.

(Embodiment 2) In the first embodiment, a coil core 18 composed of a substantially E-shaped coil having a central core portion 18a and external core portions 18b positioned substantially parallel to both sides of the central core portion 18a, and a metallic shell are provided. 16 shows an example of a coil-integrated spark plug 100 that forms a closed magnetic circuit (FIG. 1).
However, in the present embodiment, an example will be described in which a closed magnetic path is formed by a combination of a coil core and a metal shell in another form. In detail, the coil core is formed by a combination of a central core portion and a cylindrical outer core portion located outside the central core portion, and the outer core portion forms a part of a casing of the ignition coil portion. Is what you do.

The spark plug 30 of the present embodiment has an integral coil.
0 will be described with reference to FIG. Note that the coil-integrated ignition plug 300 of the present embodiment has a structure in which an ignition coil unit 32 having a coil core 31 is integrated with the ignition plug unit 11 described in the first embodiment, as described later. The ignition coil portion 32 is provided outside a T-shaped coil formed by laminating silicon steel plates so as to have a central core portion 31a, and is formed of a ferromagnetic material, specifically, a cylindrical external shape made of ferrite. A core 31b is provided, and the coil core 31 is provided by combining a T-shaped coil and a cylindrical outer core 31b. In addition, a primary bobbin 20 around which the primary coil 19 is wound and a secondary bobbin 22 around which the secondary coil 21 is wound are coaxially wound around the central core portion 31a. The outer diameter of the cylindrical outer core portion 31b is formed to be substantially the same as the outer diameter of the main body portion 16b of the metal shell 16.

Next, the integration of the ignition plug 11 and the ignition coil 32 according to this embodiment will be described. First, a T-shaped coil is formed, and a primary bobbin 20 on which a primary coil 19 is wound and a secondary bobbin 22 on which a secondary coil 21 is wound are coaxially formed on a central core portion 31a of the T-shaped coil. Wrap. A part of the central core portion 18a is inserted (inserted) into the shaft hole 14 of the insulator 13 of the ignition plug portion 11. Then, an output terminal 25 connected to a cable 27b for sending a voltage (secondary voltage) generated by the secondary coil 21 is connected to the ignition plug unit 1
The first central electrode 15 is brought into contact (connected). Then, a cylindrical outer core portion 31b is inserted so as to cover the T-shaped coil, and the coil core 31 is formed by combining the outer core portion 31b with the T-shaped coil. Further, when inserting the cylindrical outer core 31b, the outer core 31b is inserted until the distal end surface 31c of the outer core 31b comes into contact with the upper surface of the main body 16b of the metal shell 16 of the ignition plug 11. Then, the tip surface 31c of the cylindrical outer core portion 31b
33 between the metal shell 16 and the upper surface of the main body 16b
Are joined by resistance welding, laser welding, or the like. At this time, the distal end portion 31c of the outer core portion 31b and the main body portion 16b of the metal shell 16 may be joined while being pressed against each other. Then, from the opposite side where the cylindrical outer core portion 31b and the metal shell 16 are joined, a softened resin material 34 (epoxy resin or the like) having excellent insulation and heat resistance is filled into a space in the cylinder. The resin material 34 is cured until it is filled, and a disk 36 made of a paramagnetic material having a hexagonal nut portion 35 on one surface is joined to the outer core portion 31b to hermetically seal.

By thus integrating the ignition coil section 32 and the ignition plug section 11, the coil-integrated ignition plug 300 of this embodiment is
1 and a metal shell 16 form a closed magnetic circuit. Further, a cylindrical outer core portion 31b constituting the coil core 31 is formed.
However, it has the structure which substitutes a part of casing of the ignition coil part 32. Therefore, in the coil-integrated spark plug 300, it is not necessary to house the coil core using a separate casing, and the coil core is formed so as to simultaneously perform the function of the coil core and the function of the casing.
As compared with the first embodiment, it is possible to provide a coil-integrated spark plug that satisfies a further downsizing.

(Embodiment 3) In this embodiment, the center electrode of the ignition plug portion in the coil-integrated ignition plug of Embodiment 1 or 2 is formed by using a ferromagnetic material such as nickel (nickel alloy). By doing, together with the closed magnetic path formed by the coil core and the metal shell,
It forms a part of the closed magnetic circuit. Hereinafter, the present embodiment will be described using a coil-integrated spark plug having the same structure as that of the first embodiment.

As shown in FIG. 5, the structure of the coil-integrated spark plug 400 of this embodiment is basically the same as that of the first embodiment.
1 (see FIG. 1), except that the center electrode 42 is formed of an alloy of nickel, which is a ferromagnetic material. That is, the center electrode 42 constitutes a part of a closed magnetic circuit formed by the coil core 18 and the metal shell 16. Therefore, when the magnetic flux Φ is generated by the primary current, the magnetic flux Φ forms a magnetic path as shown in FIG. As a result, the portion of the closed magnetic path that becomes a break in the magnetic flux is reduced to a minimum, so that leakage of the magnetic flux Φ can be suppressed to a minimum, and the ignition for supplying to the center electrode 42 of the ignition plug portion 41 can be performed. Voltage loss from the coil section 12 can also be minimized. Note that also in the present embodiment, the magnetic flux saturation gap 43 is formed by using the thickness of the insulator 13 as a substitute.

Moreover, the coil-integrated spark plugs described in the first to third embodiments are more effective when attached to a gas engine using gaseous fuel such as methane gas as fuel.

Normally, gaseous fuel has a higher insulating property than gasoline which is a liquid fuel, so that a gas engine using gaseous fuel has a relatively high discharge voltage. For details,
The discharge voltage at the ignition plug in a gas engine is 30 to 40% higher than that in a gasoline engine. Furthermore, in order to cause a spark at the spark plug portion, the power supply voltage supplied for spark discharge must be higher than the discharge voltage. Therefore, in the coil-integrated spark plug attached to the gas engine, it is required that the leakage of the voltage supplied for spark discharge is small.

Therefore, in the coil-integrated spark plugs according to the first to third embodiments, a closed magnetic path is formed by the coil core and the metal shell or by the center electrode in addition to the coil core and the metal shell as described above. Therefore, even when a low voltage is sent to the primary coil and a primary current flows, the leakage of the magnetic flux generated in the closed magnetic circuit is small, and the voltage (secondary voltage) of the high secondary coil is reduced. Is what can happen. That is, the first embodiment
Even when the coil-integrated spark plug described in No. 3 is attached to a gas engine, it is possible to perform high-efficiency, good and stable spark discharge. Therefore, in a gas engine using gaseous fuel as a fuel, the coil-integrated spark plug of the present invention is very effective.

In addition, since the gas engine uses gaseous fuel as the fuel, there is almost no smoldering (carbon deposition on the insulator) in the ignition plug.
Therefore, the life of the coil-integrated spark plug can be extended, and the plug can be omitted from being replaced, so that the maintenance of the coil-integrated plug can be realized.

In the above, the present invention has been described with reference to the embodiments. However, it is needless to say that the present invention is not limited to the above-described embodiments, and can be appropriately modified and applied without departing from the gist thereof. Nor. For example, Embodiments 1-3
In the above, the spark plug portion is constituted by a single-pole ground electrode, but it may be multi-pole. In the third embodiment, the center electrode is made of a nickel alloy which is a ferromagnetic material. However, in order to improve the heat removal of the center electrode, a core made of copper is used. May be coated with an alloy made of nickel, which is a ferromagnetic material, to form the center electrode.

Further, in the first to third embodiments, the screw portion is formed on the metal shell of the ignition plug portion for fixing to the internal combustion engine (cylinder head). It is also possible to provide a coil-integrated spark plug having a configuration in which a screw is not formed and a flange is formed with a bolt hole for fixing the internal combustion engine to a part of the ignition coil. By configuring the coil-integrated spark plug in this way, for mounting on an internal combustion engine, it is necessary to insert a plug wrench or the like into the hexagon nut part and rotate it to rotate the screw part of the metal shell for mounting. Absent. That is, since the coil-integrated spark plug having the above-described configuration is inserted into the internal combustion engine, and the bolt holes in the flange portion are aligned with the bolt holes provided in the internal combustion engine, the bolts can be fixed only by bolting and fixing. This makes it possible to easily mount the coil-integrated spark plug.

[Brief description of the drawings]

FIG. 1 is an overall partial sectional view of a coil-integrated spark plug according to a first embodiment.

FIG. 2 is a conceptual diagram showing a magnetic path of a magnetic flux Φ in a closed magnetic path formed in the coil-integrated ignition plug of the first embodiment.

FIG. 3 is an overall partial cross-sectional view of a coil-integrated ignition plug showing another embodiment of the first embodiment in which the entire coil core is covered with a resin material.

FIG. 4 is an overall partial cross-sectional view of a coil-integrated spark plug according to a second embodiment.

FIG. 5 is a partial cross-sectional overall view of a coil-integrated ignition plug according to a third embodiment, and a conceptual diagram showing a magnetic path of a magnetic flux Φ in a closed magnetic path formed in the coil-integrated ignition plug.

FIG. 6 is a partial cross-sectional overall view of a coil-integrated spark plug in which a closed magnetic circuit type coil core is arranged in an ignition coil unit in the related art.

FIG. 7 is an overall partial cross-sectional view of a coil-integrated spark plug in which a closed magnetic path formed by a combination of a coil core and a cylinder formed of a ferromagnetic material is provided in an ignition coil unit in the related art.

[Explanation of symbols]

100, 200, 300, 400 Coil-integrated ignition plug 11, 41 Ignition plug part 12, 32 Ignition coil part 13 Insulator 15, 42 Center electrode 16 Metal shell 16b Main body part 18, 31 Coil core 18a, 31a Central core part 18b External Core part 31b External core part (cylindrical external core part) 19 Primary coil 21 Secondary coil 29, 43 Magnetic flux saturation gap

Claims (7)

[Claims] 1. An ignition coil section comprising a coil core made of a ferromagnetic material having a central core section wound with a primary coil and a secondary coil and an external core section located outside the central core section. And an ignition plug portion including an insulator having a shaft hole and a center electrode inserted into the shaft hole, and a metal shell for fitting the insulator. The ignition plug part is integrated so as not to rotate, and a closed magnetic circuit is formed by the coil core of the ignition coil part and the metal shell of the ignition plug part. . 2. The ignition plug according to claim 1, wherein the outer core is formed in a substantially cylindrical shape, and the outer core forms a part of a casing of the ignition coil. A coil-integrated spark plug characterized in that: 3. The coil-integrated spark plug according to claim 1, wherein a part of the central core portion is inserted into the shaft hole of the insulator. Integrated spark plug. 4. The spark plug according to claim 1, wherein at least a part of the center electrode is formed of a ferromagnetic material, and a part of the closed magnetic path is formed. A spark plug integrated with a coil. 5. The coil-integrated spark plug according to claim 1, wherein the closed magnetic path has at least one magnetic flux saturation gap. . 6. The coil-integrated spark plug according to claim 5, wherein the insulator is inserted into the magnetic flux saturation gap. 7. The coil-integrated spark plug according to claim 1, which is mounted on a gas engine that uses gaseous fuel as fuel.