Plasma apparatus using a cylinder head

Provided is a plasma apparatus using a cylinder head, which comprises a discharge device installed with an electrode exposed to the combustion chamber and installed in the cylinder head, an antenna installed to protrude from the cylinder head into the combustion chamber, a bulging portion bulging from the cylinder head to the combustion chamber so as to cover the antenna, made from insulator or dielectric, an electromagnetic wave transmission line installed in the cylinder head and with one end connected to the antenna and the other end, covered with insulator or dielectric, penetrating the cylinder head to extend to an outer wall of the cylinder head, and an electromagnetic wave generator for feeding electromagnetic waves to the electromagnetic wave transmission line. At compression stroke, discharge is generated with the electrode of the discharge device and the electromagnetic waves, fed from the electromagnetic wave generator through the electromagnetic wave transmission line, are radiated from the antenna.

TECHNICAL FIELD

This invention belongs to the technical field of the internal combustion engine, and relates to the improvement of combustion in the combustion chamber of an internal combustion engine with a cylinder head.

BACKGROUND OF THE INVENTION

Patent Document 1 shows an internal combustion engine including a combustion/reaction chamber, auto-ignition means, microwave radiation means, and control means. The combustion/reaction chamber consists of a cylinder and piston. The combustion/reaction chamber is supplied with a mixture of reactive and oxidation gas. In the combustion/reaction chamber, a plasma reaction of the mixture is carried out. The auto-ignition means automatically ignites the mixture by injecting a mixture of reactive and oxidation gas under high pressure, compressing the mixture and increasing the temperature. The microwave radiation means radiates the combustion/reaction chamber with microwaves. The control means controls the auto-ignition means and microwave radiation means, and repeats a cycle that involves radiating the combustion/reaction chamber with microwaves so that large amounts of hydroxyl (OH) radicals and ozone (O3) are generated from the moisture in the combustion/reaction chamber mixture, which then oxidizes and reacts chemically, combustion of the mixture in the combustion/reaction chamber is promoted by the large amount of OH radicals and O3, when the auto-ignition, means ignites the mixture.

The internal-combustion engine with an electrical field formed in the combustion chamber is disclosed in Patent Documents 2 to 4. Patent Document 2 outlines an internal combustion engine, containing the following: a cylinder block with a cylinder wall; a cylinder head on the cylinder block; a piston in the cylinder block; a combustion chamber formed by the cylinder wall, cylinder head and piston; and an electrical field apply means for applying an electrical field in the combustion chamber during combustion of the engine. When an electrical field is applied to the flame in this internal combustion engine, ions move into the flame and collide. This increases the flame propagation speed, and the ions in the gas that has already burnt move to unburned gas and alter the chemical reaction in the unburned gas. This maintains a uniform flame temperature and controls engine knock.[Patent Document 1] Japanese Patent Application Laid-open Publication No. 2007-113570[Patent Document 2] Japanese Patent Application Laid-open Publication No. 2000-179412[Patent Document 3] Japanese Patent Application Laid-open Publication No. 2002-295259[Patent Document 4] Japanese Patent Application Laid-open Publication No. 2002-295264

SUMMARY OF THE INVENTION

The inventor of the present invention extrapolated the mechanism of combustion promotion in the internal combustion engine which is disclosed in Patent Document 1, and obtained a constant finding about the mechanism. In this mechanism, a small amount of plasma is discharged firstly. The plasma is irradiated with microwaves for a given period of time, so that the amount of plasma increases. Thus a large amount of OH radicals and ozone is generated from moisture in the air-fuel mixture within a short period of time, promoting an air-fuel mixture reaction. This mechanism of the combustion promotion, obtained by generating a large amount of OH radicals and ozone, promotes combustion with plasma, is entirely different from combustion-promoting mechanisms that use ions to increase flame propagation speed, disclosed in Patent Documents 2 through 4.

In the art of Patent Documents 2, said electrical field apply means comprises a conductive member arranged so as to apply the electrical field in the combustion chamber. This conductive member is a nickel-chromium alloy wire, with a preferable diameter of 1.0 mm, and installed in an annular groove established in an annular insulator inserted in the cylinder wall of the cylinder block. In the art of Patent Documents 2 through 4, the substantial modifications required for the cylinder block and other structural components of a conventional internal combustion engine. These modifications increase the time required to design an engine, and do not permit the sharing of parts with existing internal combustion engines.

In the view of the foregoing, the present invention has been achieved. An object of the invention is to provide the plasma apparatus using a cylinder head, which can easily realize the combustion-promoting mechanism, obtained by generating a large amount of OH radicals and ozone with plasma, by using the existing internal combustion engine as far as possible. By this realization, it can be realized to minimize the time required to design an engine and facilitate the sharing of many parts between existing internal combustion engines.

The present invention is plasma apparatus using a valve, which installed in an internal combustion engine of which combustion chamber formed by a cylinder block that is penetrated by a cylinder, a piston fits into the cylinder so as to reciprocate freely, and the cylinder head assembled to the anti-crankcase side of the cylinder block, the plasma apparatus comprises, a discharge device with an electrode exposed to the combustion chamber and installed in the cylinder head, an antenna installed to protrude from the cylinder head into the combustion chamber, a bulging portion bulging from the cylinder head to the combustion chamber so as to cover the antenna, made from insulator or dielectric, an electromagnetic wave transmission line installed in the cylinder head and with one end connected to the antenna and the other end, covered with insulator or dielectric, penetrating the cylinder head to extend to an outer wall of the cylinder head, and an electromagnetic wave generator for feeding electromagnetic waves to the electromagnetic wave transmission line, wherein the plasma apparatus is configured such that discharge is generated with the electrode of the discharge device and the electromagnetic waves fed from the electromagnetic wave generator through the electromagnetic wave transmission line are radiated from antenna at compression stroke.

At the compression stroke in the actuation of the internal combustion engine, discharge is generated at the electrode of the discharge device and the electromagnetic waves fed from the electromagnetic wave generator through the electromagnetic wave transmission line are radiated from the antenna. Therefore, the plasma is generated near the electrode. This plasma receives energy of an electromagnetic waves (electromagnetic wave pulse) supplied from the antenna for a given period of time. As a result, the plasma generates a large amount of OH radicals and ozone to promote the combustion. In fact electrons near the electrode are accelerated, fly out of the plasma area, and collide with gas such as air or the air-fuel mixture in surrounding area of said plasma. The gas in the surrounding area is ionized by these collisions and becomes plasma. Electrons also exist in the newly formed plasma. These also are accelerated by the electromagnetic wave pulse and collide with surrounding gas. The gas ionizes like an avalanche and floating electrons are produced in the surrounding area by chains of these electron acceleration and collision with electron and gas inside plasma. These phenomena spread to the area around discharge plasma in sequence, then the surrounding area get into plasma state. In the result of the phenomena as mentioned above it, the volume of plasma increases. Then the electrons recombine rather than dissociate at the time when the electromagnetic wave pulse radiation is stopped. As a result, the electron density decreases, and the volume of plasma decreases as well. The plasma disappears when the electron recombination is completed. A large amount of OH radicals and ozone is generated from moisture in the gas mixture as a result of a large amount of the generated plasma, promoting the combustion of the mixture.

In this case, the cylinder block etc. which are the major structural materials can be used without modification compared with existing internal combustion engine. And the cylinder head is remodeled. With the exception of internal combustion engine which basically needs spark plug, it may mount a discharge device on the cylinder head in internal combustion engine that is not necessary a spark plug. Therefore, it is realized to minimize the time required to design an internal combustion engine and share many parts with existing internal combustion engines. In addition, the bulging portion reduces the heat load which affects the antenna in the combustion chamber and the fatigue of the antenna due to mechanical vibration.

The plasma apparatus of the present invention may be applicable for which the antenna edge aims at the electrode of the discharge device.

This allows the plasma generated by the discharge at the electrode to radiate electromagnetic wave pulses from the antenna intensively. As a result, the plasma is supplied energy intensively, which generates a large amount of OH radicals and ozone efficiently, further promoting the combustion.

The plasma apparatus of the present invention may be applicable for which the electrode is placed in the vicinity of the center of the combustion chamber, and the antenna is installed between the electrode and a portion corresponding to a cylinder wall on the cylinder head, when viewed from the direction of reciprocation of the piston.

This allows the plasma generated by the discharge near the electrode to receive energy from the electromagnetic wave pulse radiated from the antenna, increasing its volume. The antenna is placed between the electrode and the portion corresponding to the cylinder wall. Hence, a large amount of plasma is distributed from the electrode to the portion corresponding to the cylinder wall, and the combustion flame is spread from the electrode to the cylinder wall by the OH radicals and ozone generated by the plasma.

The plasma apparatus of the present invention may be applicable for which the electrode is placed in the vicinity of the center of the combustion chamber, and a plurality of antennas queue up from the electrode toward a portion corresponding to a cylinder wall on the cylinder head, when viewed from the direction of reciprocation of the piston.

This allows the plasma generated by the discharge near the electrode to receive energy from the electromagnetic wave pulse radiated from the antennas, increasing its volume. The antennas queue up from the electrode to the portion corresponding to the cylinder wall. Hence, a large amount of plasma is distributed from the electrode to the portion corresponding to the cylinder wall, and the combustion flame is spread from the electrode to the cylinder wall by the OH radicals and ozone generated by the plasma.

The plasma apparatus of the present invention may be applicable for which the electrode and the antenna are arranged so that a virtual line, which connect the electrode and the antenna, pass through two adjoining ports of one or more inlet ports and one or more exhaust ports in the cylinder head, the intake port is opened and closed by an intake valve and the exhaust port is opened and closed by an outlet valve.

This makes possible that the antenna is allocated effectively by using plane between ports.

The plasma apparatus of the present invention may be applicable for which the electrode is located close to a portion where the electric field intensity generated by the electromagnetic waves becomes strong in the antenna when the electromagnetic waves are fed to the antenna.

This makes it possible that the electromagnetic wave pulse irradiates the plasma generated by the discharge at the electrode from the antenna near plasma. The energy is intensively supplied to said plasma. As a result, a large amount of OH radicals and ozone is efficiently generated, further promoting the combustion.

DESCRIPTION OF REFERENCE CHARACTERS

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, embodiments of the present invention will be described.FIGS. 1 and 2shows the embodiment of the internal combustion engine E comprising the plasma apparatus using a cylinder head of the present invention. The present invention targets reciprocating engines. In this embodiment, engine E is a four-cycle gasoline engine. Item100is the cylinder block. Cylinder block100contains cylinder110, which has an approximately circular cross section. Cylinder110penetrates cylinder block100. Piston200, which has an approximately circular cross section corresponding to cylinder110, fits into cylinder110and reciprocates freely. Cylinder head300is assembled on the anti-crankcase side of cylinder block110. Cylinder head300, piston200, and cylinder110form combustion chamber400. Item910is a connecting rod, with one end connected to piston200and the other end connected to crankshaft920, which is the output shaft. Cylinder head300has intake port310, which is a component of the intake line, and exhaust port320, which is a component of the exhaust line. One end of intake port310connects to combustion chamber400; the other end is open at the outside wall of cylinder head300. One end of exhaust port320connects to combustion chamber400; the other end is open at the outside wall of cylinder head300. The cylinder head has guide hole330that passes through intake port310to the outside wall of cylinder head300. Rod-shaped valve stem511of intake valve510fits into guiding hole330and reciprocates freely. Umbrella-shaped valve head512, set at the end of valve stem511, opens and closes the combustion chamber side opening311of intake port310at a given timing by a valve open/close mechanism having a cam and so on(not shown in the figure). Cylinder head300has guiding hole340that passes through exhaust port320to the outside wall of cylinder head300. Rod-shaped valve stem521of exhaust valve520fits into guiding hole340and reciprocates freely. Umbrella-shaped valve head522, set at the end of valve stem521, opens and closes the combustion chamber side opening321of the exhaust port320at a given time by the valve open/close mechanism having cam and so on (not shown in the figure). Item810is a spark plug installed in cylinder head300to expose a pair of electrodes812,813to combustion chamber400. Spark plug810discharges at the electrodes when piston200is near top dead center. Therefore, four strokes (intake, compression, combustion of mixture, and exhaust of exhaust gas) occur while piston200reciprocates between top dead center and bottom dead center twice. However, this embodiment does not restrict the interpretation of the internal combustion engine targeted by the present invention. The present invention is also suitable for use with two-stroke internal combustion engines and diesel engines. Target gasoline engines include direct-injection gasoline engines, which create a mixture inside the combustion chamber to inject fuel into the intake air. Target diesel engines include direct-injection diesel engines, which inject fuel into the combustion chamber directly, and divided-chamber diesel engines, which inject fuel into divided chamber. Internal combustion engine E in this embodiment has four cylinders, but this does not restrict number of cylinders of the internal combustion engine targeted by the present invention. The internal combustion engine for this embodiment has two intake valves510and two exhaust valves520, but this does not restrict the number of intake or exhaust valves of the internal combustion engine targeted by the present invention. Item700is a gasket installed between cylinder block100and cylinder head300.

Said spark plug810also functions as a discharge device810of the plasma apparatus using a cylinder head of the present invention. This discharge device810is installed in the cylinder head300. This discharge device810is set on the wall of the combustion chamber400. This discharge device810comprises a connection811set outside of the combustion chamber400, a first electrode812electrically-connected to the connection811, and a second electrode813contacts the cylinder head300and connects in ground. The first electrode812and the second electrode813are placed opposite at specified interval on the discharge device810. Both of them are exposed to the combustion chamber400. The discharge device810is connected to a discharge voltage generator950which generates voltage for discharge. Here, the discharge voltage generator950is DC 12V power supply and a spark coil. The cylinder head300is earthed and the connection811connects to the discharge voltage generator950. In case of applying voltage between the cylinder head300and the connection811, discharge happens between the first electrode812and the second electrode813. As described above, it may discharge between the electrodes of the discharge device and a wall of the combustion chamber, or other earthed members without a pair of electrodes. For example, in case that the internal combustion engine is a diesel engine, it does not install a spark plug under normal circumstances. Therefore it needs to install the discharge device, having an electrode exposed to the combustion chamber, on the cylinder head. In this case, it may install the spark plug as explained above as the discharge device, and connects it to the discharge voltage generator. However the discharge device does not always need to use a spark plug, because the discharge device requires generating plasma by discharge regardless the size. The discharge device may be used for example piezo element or other device.

Antenna820is installed in cylinder head300to radiate electromagnetic waves to combustion chamber400. The wall of combustion chamber400in cylinder head300contains a hole that penetrates to the outside wall. Inside support370is installed near the combustion chamber side opening of this hole, and tubular outside support380is installed outside and continuation of the inside support370. Inside support370and outside support380are made from a ceramic. Both supports may be made from dielectric material or an insulator. Antenna820, which is made from metal, is installed in inside support370. However, it can be made from a conductor, dielectric or insulator, provided that electromagnetic waves are radiated well from it to the combustion chamber when they are supplied between the antenna and the earth member. Antenna820consists of a bar installed near the combustion chamber side opening of said hole. Antenna820protrudes from cylinder head300to combustion chamber400. Inside support370contains a bulging portion371. This bulging portion371bulges from the wall of combustion chamber400in cylinder head300, covering antenna820. Bulging portion371may be made from an insulator or dielectric. Because the bulging portion371forms part of inside support370, it is also made from a ceramic. The bulging portion may be made from different materials against inside support. For example, the length of the antenna820is set to a quarter of wavelength in electromagnetic waves, standing wave is generated in the antenna820. Thus, electrical field strength at the end of antenna820becomes strong. For example, the length of the antenna820is set to a multiple of a quarter wavelengths of the electromagnetic waves so that standing waves are generated in the antenna820, increasing the electrical field at multiple points, where the anti-nodes of the standing waves are generated, in the antenna820. Here, antenna820is buried inside support370. The solid cross-section of antenna820is approximately circular for its entire length. However, antenna820of the plasma apparatus of the present invention is not restricted to a circular cross-sectional shape. The first electrode812and the second electrode813are located close to a portion where the electric field intensity generated by the electromagnetic waves becomes strong in the antenna820when the electromagnetic waves are fed to the antenna820. Here, the end of antenna820, the first electrode812and the second electrode813are close to each other along the wall of combustion chamber400in cylinder head300at specified intervals. Thus, when electromagnetic waves are supplied between antenna820and cylinder head300, which is earthed, electromagnetic waves are radiated from antenna820to combustion chamber400. In this embodiment, antenna820is a rod-shaped curved monopole. However, the antenna of the plasma apparatus in the present invention is not restricted. The antenna of the plasma apparatus in the present invention may be dipole type, Yagi-Uda type, single wire type, loop type, phase difference feeder type, grounded type, ungrounded and perpendicular type, beam type, horizontal polarized omni-directional type, corner-reflector type, comb type or other type of linear antenna, microstrip type, planar inverted F type or other type of flat antenna, slot type, parabola type, horn type, horn reflector type, Cassegrain type or other type of solid antenna, Beverage type or other type of traveling-wave antenna, star EH type, bridge EH type or other type of EH antennas, bar type, small loop type or other type of magnetic antenna, or dielectric antenna.

Electromagnetic wave transmission line830is installed in cylinder head300. One end of electromagnetic wave transmission line830is connected to antenna820, and the other end is covered by a dielectric that penetrates and stretches to the outside wall of cylinder head300. Electromagnetic wave transmission line830is installed in outside support380, and is made from copper wire. Electromagnetic wave transmission line830may also be made from any conductor, insulator, or dielectric, as long as electromagnetic waves are transmitted well to antenna820when they are supplied between antenna820and the earthed member. A possible variation is an electromagnetic wave transmission line that consists of a waveguide made from a conductor or dielectric. Here, electromagnetic wave transmission line830is buried in outside support380, and passed through outside support380. One end of the electromagnetic wave transmission line830is connected to said antenna820and the other end is extracted from the outside wall of cylinder head300to outside. Thus, when electromagnetic waves are supplied between electromagnetic wave transmission line830and cylinder head300that is the earth member, they are introduced into antenna820.

Electromagnetic wave generator840supplies the electromagnetic waves to transmission line830, and is installed in internal combustion engine E or its surroundings. Electromagnetic wave generator840in this embodiment is a magnetron that generates 2.4-GHz-bandwidth microwaves. However, this does not restrict the construction of the electromagnetic wave generator of the plasma apparatus in the present invention.

As shown inFIG. 1, antenna820stretches from the outside wall of cylinder head300to combustion chamber400along the pass of hole. Then the antenna820turns off L-shaped. The end of antenna820aims at the first electrode812and the second electrode813of discharge device810along the wall of combustion chamber400in cylinder head300. In addition, as shown inFIG. 2, the first electrode812and the second electrode813are placed in the vicinity of the center of the combustion chamber400, when viewed from the direction of reciprocation of the piston. Antenna820is installed from the first electrode812and the second electrode813to a portion corresponding to a cylinder wall on the cylinder head. Two exhaust valves520are installed in this embodiment, although multiple exhaust values520may be used. The first electrode812, the second electrode813, and antenna820are arranged so that a virtual line, which connects the first electrode812or the second electrode813and the antenna820, pass through two adjoining ports of two inlet ports310and two exhaust ports320in the cylinder head300.

In this plasma apparatus, discharge is generated between the first electrode812and the second electrode813, and electromagnetic waves fed from the electromagnetic wave generator840through the electromagnetic wave transmission line830are radiated from the antenna820at the compression stroke. Cylinder head300is earthed. The earth terminals of discharge voltage generator950and electromagnetic wave generator840are earthed. Discharge voltage generator950and electromagnetic wave generator840are controlled by controller880, which has a CPU, memory, and storage etc, and outputs control signals after computing input signals. A signal line from crank angle detector890for detecting crank angle of crankshaft920is connected to control unit880. Crank angle detection signals are sent from crank angle detector890to controller880. Therefore, controller880receives signals from crank angle detector890and controls the actuations of discharge device810and electromagnetic wave generator840. However, this does not restrict the control method and the composition of the input-output signals as for plasma apparatus of the present invention.

Therefore, at the compression stroke in the actuation of the internal combustion engine E, discharge is generated between the first electrode812and the second electrode813of said discharge device810and the electromagnetic waves fed from the electromagnetic wave generator840through the electromagnetic wave transmission line830are radiated from the antenna820. Therefore, plasma is generated near the first electrode812and the second electrode813by discharge. This plasma receives energy of an electromagnetic waves (electromagnetic wave pulse) supplied from the antenna820for a given period of time. As a result, the plasma generates a large amount of OH radicals and ozone to promote the combustion. In fact electrons near the electrode are accelerated, fly out of the plasma area, and collide with gas such as air or the air-fuel mixture in surrounding area of said plasma. The gas in the surrounding area is ionized by these collisions and becomes plasma. Electrons also exist in the newly formed plasma. These also are accelerated by the electromagnetic wave pulse and collide with surrounding gas. The gas ionizes like an avalanche and floating electrons are produced in the surrounding area by chains of these electron acceleration and collision with electron and gas inside plasma. These phenomena spread to the area around discharge plasma in sequence, then the surrounding area get into plasma state. In the result of the phenomena as mentioned above it, the volume of plasma increases. Then the electrons recombine rather than dissociate at the time when the electromagnetic wave pulse radiation is stopped. As a result, the electron density decreases, and the volume of plasma decreases as well. The plasma disappears when the electron recombination is completed. A large amount of OH radicals and ozone is generated from moisture in the gas mixture as a result of a large amount of the generated plasma, promoting the combustion of the mixture.

In this case, the cylinder block etc. which are the major structural materials can be used without modification compared with existing internal combustion engine. And the cylinder head is remodeled. With the exception of internal combustion engine E which basically needs spark plug810, it may mount a discharge device on the cylinder head in internal combustion engine that is not necessary a spark plug. Therefore, it is realized to minimize the time required to design an internal combustion engine and share many parts with existing internal combustion engines. In addition, the bulging portion reduces the heat load which affects the antenna in the combustion chamber and the fatigue of the antenna due to mechanical vibration.

In the plasma apparatus using a cylinder head of the present invention, the antenna may be installed to protrude from the cylinder head into the combustion chamber. The direction of the antenna tip is not restricted. Though there are various embodiments, the tip direction of the antenna820aims at the first electrode812and the second electrode813of the discharge device810in the plasma apparatus using a cylinder head of the present invention. This allows the plasma generated by the discharge at the electrode to radiate electromagnetic wave pulses from the antenna820intensively. As a result, the plasma is supplied energy intensively, which generates a large amount of OH radicals and ozone efficiently, further promoting the combustion.

In the plasma apparatus using a cylinder head of the present invention, the electrodes of the discharge device, installed in the cylinder head, may be exposed to the combustion chamber. The position of the electrodes is not restricted. Moreover, the antenna may be installed to protrude from the cylinder head into the combustion chamber. The position of the antenna is not restricted. Though there are various embodiments, the first electrode812and the second electrode813are placed in the vicinity of the center of the combustion chamber400when viewed from the direction of reciprocation of the piston in the plasma apparatus using a cylinder head of the present invention. Said antenna820is installed between the first electrode812or the second electrode813and the portion corresponding to the cylinder wall. This allows the plasma generated by the discharge near the first electrode812and the second electrode813to receive energy from the electromagnetic wave pulse radiated from the antenna820, increasing its volume. Antenna820is installed between the first electrode812or the second electrode813and the portion corresponding to the cylinder wall. Hence, a large amount of plasma is distributed from the first electrode812or the second electrode813to the portion corresponding to the cylinder wall, and the combustion flame is spread from the first electrode812or the second electrode813to the cylinder wall by the OH radicals and ozone generated by the plasma.

In the plasma apparatus using a cylinder head of the present invention, relative position of the electrodes and the antenna is not restricted. Though there are various embodiments, the first electrode812, the second electrode813, and antenna820are arranged so that a virtual line, which connects the first electrode812or the second electrode813and the antenna820, pass through two adjoining ports of two inlet ports310and two exhaust ports320in the cylinder head300. This makes possible that the antenna820is allocated effectively by using plane between exhaust ports320.

In the plasma apparatus using a cylinder head of the present invention, the positional relationship between the antenna and the electrodes are not restricted. Though there are various embodiments, the first electrode812and the second electrode813are located close to a portion where the electric field intensity generated by the electromagnetic waves becomes strong in the antenna820when the electromagnetic waves are fed to the antenna820in the plasma apparatus using a cylinder head of the present invention. This makes it possible that the electromagnetic wave pulse irradiates the plasma, generated by the discharge at the first electrode812and the second electrode813, from the antenna820near plasma. The energy is intensively supplied to said plasma. As a result, a large amount of OH radicals and ozone is efficiently generated, further promoting the combustion.

Next, the second embodiment about the plasma apparatus using a cylinder head will be described. The plasma apparatus in the second embodiment is different from the first embodiment in only number and alignment of the antenna820. The plasma apparatus of the first embodiment installs one antenna820. On the other hand, the plasma apparatus of the second embodiment, shown inFIG. 3installs multiple antennas820which are same as the antenna820in the first embodiment. Said first electrode812and second electrode813are placed in the vicinity of the center of the combustion chamber400when viewed from the direction of reciprocation of the piston200. Moreover said multiple antennas820queue up from said first electrode812or second electrode813toward the portion corresponding to the cylinder wall, when viewed from the direction of reciprocation of the piston200. Here, three antennas820queue up respectively along four directions radiated from the center, when viewed from the direction of reciprocation of the piston820. The angle between two directions next to each other is almost 90 degrees. Moreover, the first electrode812, the second electrode813, and antennas820are arranged so that a virtual line, which connects the first electrode812or the second electrode813and the antenna820, pass through two adjoining ports of two inlet ports310and two exhaust ports320in the cylinder head300.

In the second embodiment of the plasma apparatus of the present invention, said first electrode812and second electrode813are placed in the vicinity of the center of the combustion chamber400, when viewed from the direction of reciprocation of the piston. Multiple antennas queue up from the first electrode812or the second electrode813toward the portion corresponding to a cylinder wall. This allows the plasma generated by the discharge near the first electrode812and the second electrode813to receive energy from the electromagnetic wave pulse radiated from the antennas820, increasing its volume. The antennas820queue up from the first electrode812or the second electrode813to the portion corresponding to the cylinder wall. Hence, a large amount of plasma is distributed from the first electrode812or the second electrode813to the portion corresponding to the cylinder wall, and the combustion flame is spread from the electrodes to the cylinder wall by the OH radicals and ozone generated by the plasma.

In the second embodiment of the plasma apparatus of the present invention, the first electrode812, the second electrode813, and antennas820are arranged so that a virtual line, which connects the first electrode812or the second electrode813and the antenna820, pass through two adjoining ports of two inlet ports310and two exhaust ports320in the cylinder head300. This makes possible that the antennas are allocated effectively by using plane between ports. Other functions and effects are similar to the case of the plasma apparatus in the first embodiment.

In the plasma apparatus using a cylinder head of the present invention, a pair of the electrodes or a pair of the electrode and the earth member may as well be covered with a dielectric. In this case, the dielectric-barrier discharge is generated by voltage applied between the electrodes or between the electrode and the earth member. The dielectric-barrier discharge is restricted because charges are accumulated in the surface of the dielectric covering the electrode or the earth member. Therefore, the discharge is generated on a very small scale over a very short period of time. Thermalization does not occur in the area surrounding the discharge because the discharge is terminated after a short period of time. Therefore, the gas temperature rise due to the discharge between the electrodes is reduced, which reduces the amount of NOx produced by the internal combustion engine.

The present invention includes some embodiments that combine the characteristics of the embodiments described above. Moreover, the embodiments described above are only examples of the plasma apparatus using a cylinder head of the present invention. Thus, the description of these embodiments does not restrict interpretation of the plasma apparatus using a cylinder head of the present invention.