JP2010101206A - Spark ignition type internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problem wherein wall surfaces such as a piston and a combustion chamber of a cylinder head made of metal such as aluminum alloy contacts with ozone during operation of an internal combustion engine, and the combustion chamber and the piston and the like are always exposed to ozone and are earlier oxidized as compared to internal combustion engines not using plasma in ignition, in the internal combustion engine using plasma in ignition. <P>SOLUTION: This spark ignition type internal combustion engine makes spark discharge by a spark plug and plasma generated in the combustion react to ignite air fuel mixture. Pore-free oxide film is provided on an inner wall of the combustion chamber, especially the oxide film is provided at least on a position around the spark plug. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a spark ignition internal combustion engine that uses plasma for ignition.

  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, the plasma causes intense movement of atoms and molecules constituting the gas by applying energy. As a result, some or many of them are divided into negatively charged electrons and positively charged ions. As a whole, it is a state of a substance with unique properties that moves around while maintaining electrical neutrality. Such plasma also contains OH radicals, N radicals and ozone.

  In the internal combustion engine described in Patent Document 1, a wall surface such as a combustion chamber or a piston of a cylinder head made of a metal such as an aluminum alloy comes into contact with ozone during operation of the internal combustion engine. For this reason, compared with the internal combustion engine which does not use plasma at the time of ignition, a combustion chamber, a piston, etc. may always be exposed to ozone and may oxidize earlier.

  Therefore, the present invention aims to eliminate such problems.

  That is, the spark ignition internal combustion engine of the present invention is a spark ignition internal combustion engine that ignites an air-fuel mixture by reacting a spark discharge by a spark plug with plasma generated in a combustion chamber, and is provided on the inner wall of the combustion chamber. A porous oxide film is provided.

  According to such a structure, it becomes possible to suppress that the metal which comprises the inner wall of a combustion chamber by an oxide film, for example, aluminum, is oxidized with the ozone in plasma. In this case, since the oxide film is non-porous, it is possible to prevent the oxide film from being oxidized by ozone entering the pores in the porous oxide film.

  In order to effectively suppress oxidation, it is preferable to provide an oxide film at least at a peripheral position of the spark plug.

  In the present invention, the term “nonporous” means that the oxide film does not have a hole that opens on the surface, and that the hole that opens on the surface is closed by a sealing treatment and there is no opening on the surface when used. Is included.

  The present invention has a configuration as described above, and can suppress oxidation of the combustion chamber wall due to plasma generated each time combustion is performed.

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

  An engine 100 schematically showing the configuration of one cylinder in FIG. 1 is a three-cylinder for an automobile. In the following description, the structure centered on the combustion chamber of one cylinder will be described. The engine 100 is made of aluminum and mainly includes a cylinder block 1, a cylinder head 2 attached to the cylinder block 1, and a piston 4 that reciprocates in a cylinder bore 3 of the cylinder block 1.

  The cylinder block 1 includes three cylinder bores 3 in the direction of a crankshaft (not shown). Each cylinder bore 3 is structured to be cooled by a water jacket 5.

  The cylinder head 2 is formed with a dome-shaped (pent roof type) combustion chamber 6 corresponding to each cylinder bore 3, and an intake port 7, an exhaust port 8, and an ignition plug are mounted around the combustion chamber 6. Holes 9 and the like are formed. An intake valve 10 that opens and closes the intake port 7, an exhaust valve 11 that opens and closes the exhaust port 8, and a spark plug 12 are attached to the cylinder head 2. The configuration itself of the cylinder block 1 and the cylinder head 2 described above may be the same as the structure of a spark ignition type engine well known in this field.

  An oxide film 13 is formed on the cylinder head 2 on the ceiling surface of the combustion chamber 6, that is, the surface facing the top surface 4 a of the piston 4. In this embodiment, since the spark plug 12 is attached to the ceiling of the combustion chamber 6, the oxide film 13 is provided on the entire ceiling surface including the peripheral position of the spark plug 12. Note that the oxide film 13 is very thin. In FIG. 1, the thickness is emphasized more than other components in order to clarify the formation position.

  The oxide film 13 is phosphoric acid alumite formed by, for example, anodizing treatment. Since phosphoric acid alumite is porous immediately after the anodizing treatment, a sealing treatment is applied to smooth the surface of the oxide film, that is, to make it nonporous. In addition, in this embodiment, each of the valve heads 10a, 11a of the intake valve 10 and the exhaust valve 11 constituting a part of the ceiling surface of the combustion chamber 6 when the compression stroke and the expansion stroke are closed. In addition, oxide films 14, 15, 16 made of phosphoric acid alumite subjected to sealing treatment are formed on the surface of the top surface 4 a of the piston 4 that is the bottom surface of the combustion chamber 6 at a position near the top dead center. It is.

  In such a configuration, in this engine 100, in the operating state, microwaves generated by the high-voltage AC generator are radiated into the combustion chamber 6 from, for example, a horn type antenna filled with a dielectric, and thereby generated. The plasma is caused to react with the spark discharge by the spark plug 12 to ignite the air-fuel mixture. The high-voltage AC generator includes a magnetron and a control circuit that controls the magnetron. The microwave output from the magnetron is supplied to the antenna through the waveguide. The control circuit controls the output timing and output power of the microwave output from the magnetron based on the high-voltage AC generation signal output from the electronic control device that controls the operation of the engine 100. When plasma is generated, a microwave is supplied to the antenna, whereby a high-frequency electric field is formed in the combustion chamber 6 in a direction perpendicular to the spark discharge by the spark plug 12.

  At the time of ignition, a spark discharge is generated in the spark plug 12 by an ignition coil (not shown), and a high-frequency electric field is generated by microwaves almost simultaneously with or immediately after the spark discharge to generate plasma, whereby the combustion chamber 6 It is the structure which burns the inside air-fuel mixture rapidly.

  Specifically, the spark discharge by the spark plug 12 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 12 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.

  Of the radicals generated by generating plasma during such combustion, ozone remarkably acts on the oxidation of the metal, but the ceiling surface of the combustion chamber 6, the intake valve 10 and the exhaust valve 11 Since the oxide films 13, 14, 15, and 16 are formed on the valve heads 10a and 11a and the top surface 4a of the piston 4, respectively, the cylinder head 2, the intake valve 10, and the exhaust gas are generated by ozone contained in the generated plasma. The valve 11 and the piston 4 are not oxidized. In this case, since the oxide films 13, 14, 15, and 16 have a non-porous surface due to the sealing treatment, ozone does not enter the oxide films 13, 14, 15, and 16. 13, 14, 15, 16 itself does not deteriorate (oxidize).

  Therefore, even if the air-fuel mixture is ignited using plasma, oxidation of the combustion chamber 6 and the intake valve 10, the exhaust valve 11, and the top surface 4 a of the piston 4 associated with the combustion chamber 6 is performed. Can be suppressed, and a decrease in durability of the engine 100 can be suppressed.

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

The oxide film, in addition to phosphoric acid anodized aluminum which has been described in the above embodiment, may be one of the non-porous, for example, DLC (Diamond Like Carbon), SiO 2 ( silicon oxide), or the like. Even in these oxide films, there is no hole on the surface where ozone may enter, or a film similar to a state in which there is no hole by performing sealing treatment is used.

  In addition, the oxide film 13, 14, 15, 16 formed by anodic oxidation has been described, but the oxide film is formed by a thin film forming technique, in particular, a vapor phase method including chemical vapor deposition or physical vapor deposition. It may be.

  Furthermore, in the above-described embodiment, the oxide film 13 is formed on the ceiling surface of the combustion chamber 6 including the periphery of the spark plug 12, and the valve head 10 a of the intake valve 10 and the valve head 11 a of the exhaust valve 11. In addition, although the description has been given of the oxide film 14, 15, 16 provided on the top surface 4 a of the piston 4, in addition to this, an oxide film may be provided on the cylinder bore 3.

  The high-voltage AC generator may be a traveling wave tube or the like in addition to the magnetron as described above, and may further include a microwave oscillation circuit made of a semiconductor.

  In addition, the antenna that radiates microwaves may be a horn type, beam type, or monopole type antenna.

  Furthermore, the center electrode of the spark plug 12 may function as an antenna to form a high-frequency power feeding unit. In this case, if the high frequency is continuously applied to the center electrode at a constant voltage, the temperature of the center electrode rises excessively, so the high frequency voltage is set to be lower than the upper limit temperature set based on the heat resistance temperature of the center electrode. It is something to control.

  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.

The principal part expanded sectional view which shows embodiment of this invention.

Explanation of symbols

6 ... Combustion chamber 12 ... Spark plug 13 ... Oxide film 14 ... Oxide film 15 ... Oxide film 16 ... Oxide film

Claims (2)

A spark ignition type internal combustion engine that ignites an air-fuel mixture by reacting a spark discharge by a spark plug and plasma generated in a combustion chamber,
A spark ignition internal combustion engine in which a nonporous oxide film is provided on the inner wall of a combustion chamber.   The spark ignition type internal combustion engine according to claim 1, wherein the oxide film is provided at least at a peripheral position of the spark plug.

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