JP2010101208A - Ignition coil for spark-ignition internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problems wherein, when an air-fuel mixture is ignited by reacting plasma generated in a combustion chamber by an electromagnetic wave with spark discharge by an ignition plug, the electromagnetic wave may be leaked from the connection of an ignition coil to the ignition plug when a conductor with the electromagnetic wave passed is built into the ignition coil attached to the ignition plug and the electromagnetic wave is emitted from the center electrode of the ignition plug into the combustion chamber. <P>SOLUTION: This ignition coil for a spark-ignition internal combustion engine is detachably directly attached to the ignition plug for the spark-ignition internal combustion engine igniting the air-fuel mixture by reacting the spark discharge by the ignition plug with the plasma generated in the combustion chamber by the electromagnetic wave. The ignition coil includes: a coil portion provided with a rod-like center iron core, and a primary winding and a secondary winding which are wound around the outside of the center iron core; the conductor passed through the inside of the coil portion and transmitting the electromagnetic wave; the connection electrically connecting the secondary winding of the coil portion and conductor to the ignition plug; and a magnetic pipe member arranged on the peripheral portions of the coil portion and connection and extending to the housing of the ignition plug. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an ignition coil of a spark ignition type internal combustion engine that generates plasma in a combustion chamber and ignites an air-fuel mixture by plasma and spark discharge by an ignition plug.

  2. Description of the Related Art Conventionally, in a spark ignition internal combustion engine mounted on a vehicle, particularly an automobile, an air-fuel mixture in a combustion chamber is ignited at each ignition timing by spark discharge between a center electrode and a ground electrode of a spark plug. In such ignition by an ignition plug, for example, in an internal combustion engine of a type in which fuel is directly injected into a cylinder, if the injected fuel is not distributed at the spark discharge position of the ignition plug, it rarely occurs.

For this reason, in such an internal combustion engine, a plasma atmosphere is generated in the discharge region of the spark plug, for example, as described in Patent Document 1, in order to compensate for the spark discharge of the spark plug, and an arc is generated in the plasma atmosphere. It is known that the discharge is performed to surely ignite the air-fuel mixture in the combustion chamber without applying a higher voltage than in the past and to obtain a stable flame.
JP 2007-32349 A

  By the way, as a method for generating plasma under atmospheric pressure, for example, a method using a magnetron is considered. When plasma is generated in a combustion chamber by a magnetron, an antenna that radiates microwaves is required. In this case, the center electrode of the spark plug can be used as an antenna.

  In recent years, some spark plugs have an ignition coil attached together with an igniter. In such a spark plug, a secondary coil and a primary coil are wound around the central core in this order, a cylindrical outer core is provided outside the primary coil, an igniter is attached to the upper end side of the central core, and the central core is It is a structure provided with a connection part with a spark plug including a secondary high-voltage terminal on the lower end side.

  When microwaves are supplied to the center electrode of the spark plug through the ignition coil having such a structure, the microwaves may leak from the inside of the ignition coil through the connection portion. That is, there is an ignition coil containing a conductor through which microwaves pass, and microwaves are radiated from the conductor. However, in the portion where the outer iron core is present, the outer iron core serves as a shield member, and the microwave is blocked. On the other hand, in the connection portion, since there is no external iron core, it was impossible to block the microwave.

  Therefore, the present invention aims to eliminate such problems.

  That is, the ignition coil of the spark ignition type internal combustion engine of the present invention is attached to and detached from the spark plug of the spark ignition type internal combustion engine that ignites an air-fuel mixture by reacting the spark discharge of the spark plug with the plasma generated in the combustion chamber by electromagnetic waves. An ignition coil of a spark ignition type internal combustion engine that can be directly attached, comprising a rod-shaped central core and a primary side winding and a secondary side winding wound around the outer side of the central core, and the inside of the coil unit , A conductor for transmitting electromagnetic waves, a connection part for electrically connecting the secondary winding and conductor of the coil part to the spark plug, and an outer peripheral part of the coil part and the connection part and extending to the housing of the spark plug And a magnetic pipe member.

  According to such a configuration, since the magnetic tube member is disposed on the outer peripheral portion of the coil portion and the connection portion, the magnetic tube member is not used for the primary winding and the secondary winding of the coil portion. It functions as an exterior iron core, and functions as an electromagnetic shielding member against high frequency at both the coil part and the connection part for the conductor. Therefore, high frequency leakage from the inside can be suppressed.

  It is preferable that the magnetic pipe member has a cylindrical shape with a single inner diameter and a single outer diameter, and the conductor passes through substantially the center in the radial direction of the magnetic pipe member. According to such a configuration, it becomes possible to make the impedance to the electromagnetic wave substantially uniform over almost the entire length of the magnetic tube member.

  The present invention is configured as described above, and the magnetic pipe member is used as an outer core for the primary side winding and secondary side winding of the coil part, and further, the coil part and It can be made to function as an electromagnetic shielding member against high frequency at both parts of the connecting portion, and thus leakage of the high frequency from the inside to the outside can be suppressed.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 shows an engine 100, which is a spark ignition type internal combustion engine, showing an enlarged mounting portion of a spark plug 1 in one cylinder, for example, of a three-cylinder double overhead camshaft (DOHC) type. 3 and the opening 5 of the exhaust port 4 are arranged opposite to each other centering on a spark plug 1 attached to substantially the center of the ceiling portion of the combustion chamber 6 and are opened at two locations per cylinder. That is, the engine 100 is attached to the cylinder block 7, and the camshafts 9 and 10 are attached to the intake side and the exhaust side of the cylinder head 8 forming the ceiling portion of the combustion chamber 6, respectively. The intake port 2 of the cylinder head 8 is opened and closed by an intake valve 11 that reciprocates when the camshaft 9 rotates, and the exhaust port 4 is opened and closed by an exhaust valve 12 that reciprocates when the camshaft 10 rotates. Is. In FIG. 1, the engine 100 is illustrated with the ignition coil 20 removed from the spark plug 1.

  The spark plug 1 includes a housing 13 made of a conductive material, a center electrode 14 that is insulated and attached in the housing 13, and a ground electrode 15 that is provided at the lower end of the housing 13 away from the center electrode 14. That is, in the spark plug 1, the housing 13 supports the substantially cylindrical insulator 16, and the connection terminal 17 attached to the upper end of the insulator 16 has a center electrode 14 protruding from the lower end of the insulator 16 and a center shaft (not shown). The ground electrode 15 is integrally provided in the housing 13 at a position that is electrically connected and extends from the lower end of the housing 13 to a position facing the lower end of the center electrode 14.

  As shown in FIG. 2, the ignition coil 20 connected to such a spark plug 1 is integrally provided with an igniter 21, and has a rod-shaped center core 22 and a primary side coil wound around the center core 22. 23 and a secondary side winding 24, a conductor 26 that transmits microwaves that pass through the inside of the coil portion 25 and into the combustion chamber 6, and a secondary side winding 24 of the coil portion 25. And a connecting portion 27 for electrically connecting the conductor 26 to the spark plug 1 and a magnetic pipe member 28 disposed on the outer peripheral portion of the coil portion 25 and the connecting portion 27. The ignition coil 20 is inserted into a mounting portion 30 provided in the cylinder head 8 and coupled to the spark plug 1, and then the igniter 21 is fixed to the cylinder head 8 and attached. In FIG. 2, the ignition coil 20 is illustrated in a state of being attached to the spark plug 1, and the configuration of the engine 100 other than the spark plug 1 and the ignition coil 20 is omitted from illustration.

  The coil portion 25 includes a central iron core 22, a secondary winding bobbin 31 incorporating the central iron core 22, a secondary winding 24 wound around the outer peripheral surface of the secondary winding bobbin 31, and a secondary winding. A primary winding bobbin 32 disposed on the outer periphery of the wire 24 and a primary winding 23 wound around the outer peripheral surface of the primary winding bobbin 32. The coil portion 25 is built in the substantially cylindrical magnetic tube member 28 and is electrically connected to the igniter 21 attached to the end of the magnetic tube member 28 on the opposite side of the connection portion 27. One end of the secondary winding 24 is electrically connected to a coil spring 33 of a connecting portion 27 described later, and the connection terminal 17 is guided to the coil spring 33 and connected to the inside of the ignition coil 20. An elastic member-made spark plug mounting portion 34 for preventing entry of foreign matter or the like is provided.

  The magnetic pipe member 28 serves as an iron core with respect to the coil portion 25 and is disposed on the outer periphery of the primary side winding 23. As such a magnetic pipe member 28, various pipe members made of a material capable of forming a magnetic circuit can be adopted. Specifically, for example, iron or iron alloy is used. Any material can be used. That is, the magnetic tube member 28 has an inner diameter larger than the outer diameter of the coil portion 25. The magnetic tube member 28 of this embodiment also covers the connection portion 27 and the spark plug mounting portion 34, and its end portion is the end of the housing 13 of the spark plug 1 as schematically shown in FIG. 3. It extends to a position beyond the part. The magnetic pipe member 28 is kept at the ground potential when the ignition coil 20 is attached to the cylinder head 8.

  The connecting portion 27 includes a secondary high-voltage terminal 34 to which the secondary winding 24 is electrically connected, and a coil spring 33 that is electrically connected to the secondary high-voltage terminal 34. The connecting portion 27 is formed integrally with the primary side winding bobbin 32.

  The conductor 26 is made of, for example, an inner conductor of a coaxial cable 35 that is covered with an insulator. The conductor 26 extends from the igniter 21 to a connection portion 27 through a through-hole provided in the center portion of the central iron core 22. The portion 27 can be electrically connected to the spark plug 1. In this case, the conductor 26 may be in direct contact with and electrically connected to the spring 33 of the connecting portion 27, and is in a non-contact state with a gap between the conductor 26 and the spring 33. It may be connected so as to be conductive. A coaxial cable 35 continuing to the conductor 26 is connected to a waveguide electrically connected to a magnetron that outputs a microwave via a coaxial converter.

  In such a configuration, when the air-fuel mixture in the combustion chamber 6 is ignited using the spark plug 1, the engine 100 reacts the spark discharge of the spark plug 1 with the plasma generated in the combustion chamber 6. The spark discharge of the spark plug 1 is made larger than the spark discharge when not reacting with plasma.

  At the time of ignition, spark discharge is generated in the spark plug 1 by the ignition coil 20, and a high-frequency electric field is generated by microwaves almost simultaneously with or immediately after the spark discharge to generate plasma, thereby mixing in the combustion chamber 6. It is the structure which burns qi rapidly.

  Specifically, the spark discharge by the spark plug 1 becomes plasma in a high-frequency electric field, and the flame becomes large.

  This is because the flow of electrons due to the spark discharge and the ions and radicals generated by the spark discharge oscillate and meander due to the influence of the high-frequency electric field, resulting in a longer path length and the number of collisions with surrounding water and nitrogen molecules. This is due to a dramatic increase. Water molecules and nitrogen molecules that have been struck by ions and radicals become OH radicals and N radicals, and the surrounding gas that has been struck by ions and radicals is ionized, in other words, a plasma state. The flame will increase dramatically.

  As a result, the air-fuel mixture is ignited by the spark discharge increased by reacting with the high-frequency electric field, so that the ignition region is expanded and the two-dimensional ignition of only the spark plug 1 is changed to the three-dimensional ignition. Therefore, the initial combustion is stabilized, and the combustion rapidly propagates into the combustion chamber 6 as the radicals increase, and the combustion expands at a high combustion rate.

  As described above, when plasma is generated in the combustion chamber 6, the center electrode 14 of the spark plug 1 is caused to function as an antenna for radiating microwaves via the conductor 26. At this time, since microwaves flow through the conductor 26 and the center electrode 14, the microwaves are radiated from the conductor 26 and the center electrode 14. In the state where the ignition coil 20 is attached to the cylinder head 8, the magnetic tube member 28 is held at the ground potential, so that the microwaves radiated from the conductor 26 and the center electrode 14 are outside the magnetic tube member 28, that is, Leakage to the outside of the ignition coil 20 can be suppressed. Similarly, the microwave radiated from the center electrode 14 does not pass through the metal housing 13 and leak outside. Moreover, since the central iron core 22 passes through the center of the magnetic tube member 28, the distance from the inner surface of the magnetic tube member 28 is substantially constant, and the impedance of the portion passing through the coil portion 25 is substantially constant. can do. Therefore, the microwave can be supplied to the combustion chamber 6 with minimal attenuation of the microwave.

  In addition, this invention is not limited to the above-mentioned embodiment.

  In the above-described embodiment, the conductor 26 composed of the inner conductor covered with the insulator of the coaxial cable 35 is provided so as to pass through the central core 22, but the conductor 26 is disposed inside the magnetic pipe member 28. If it is located in, it will not be limited to the central iron core 22. For example, the conductor may be configured by passing only the inner conductor of the coaxial cable from the igniter 21 side to the connection portion 27 between the secondary winding 24 and the primary winding bobbin 32. In this case, the conductor may be electrically connected to the connecting portion 27, or a through hole may be provided in the connecting portion 27 and guided to the inside of the combustion chamber 6 through the through hole. In this case, the tip of the conductor is exposed in the combustion chamber 6 and functions as an antenna that radiates microwaves.

  Such a conductor is connected to the magnetron via a coaxial transducer connected to the waveguide. Therefore, by directly attaching the waveguide incorporating the coaxial converter to the end of the ignition coil 20 on the igniter 21 side, the coaxial is connected to the waveguide and enters the ignition coil 20. The cable can be omitted.

  In addition, in the above-described embodiment, the magnetic body tube member 28 is configured by a single cylindrical member. However, the magnetic body tube member is a first member disposed corresponding to the position of the coil portion 25. And a second member arranged corresponding to the position of the connecting portion 27. In this case, each of the first member and the second member is made of the same material, that is, a magnetic material, and is kept at the ground potential during use.

  In the above-described embodiment, the magnetron is described as outputting microwaves. However, instead of the magnetron, a traveling wave tube or the like may be used, and a semiconductor microwave oscillation circuit may be provided.

  In addition, the specific configuration of each part is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.

  As an application example of the present invention, it can be used for a spark ignition type internal combustion engine that uses gasoline or liquefied natural gas as fuel and requires spark discharge by an ignition plug for ignition.

1 is an enlarged sectional view showing a main part of an engine to which an embodiment of the present invention is applied. Sectional drawing of the embodiment. Sectional drawing which shows the relationship between the ignition plug of the embodiment and the edge part of a magnetic body pipe member.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Spark plug 6 ... Combustion chamber 13 ... Housing 20 ... Ignition coil 22 ... Central iron core 23 ... Primary side winding 24 ... Secondary side winding 25 ... Coil part 27 ... Connection part 26 ... Conductor 28 ... Magnetic body pipe member

Claims (2)

An ignition coil of a spark ignition internal combustion engine that is detachably attached directly to the spark plug of a spark ignition internal combustion engine that ignites an air-fuel mixture by reacting spark discharge of the spark plug with plasma generated in the combustion chamber by electromagnetic waves. And
A coil portion comprising a rod-shaped central iron core and a primary winding and a secondary winding wound around the outer side of the central iron core;
A conductor that transmits electromagnetic waves through the inside of the coil section;
A connection part for electrically connecting the secondary winding and the conductor of the coil part to the spark plug;
An ignition coil for a spark ignition type internal combustion engine, comprising: a magnetic pipe member disposed on an outer peripheral portion of the coil portion and the connection portion and extending to a housing of the spark plug.   The ignition coil for a spark ignition type internal combustion engine according to claim 1, wherein the magnetic pipe member has a cylindrical shape with a single inner diameter and a single outer diameter, and the conductor passes through substantially the center in the radial direction of the magnetic pipe member.

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