JP5294960B2 - Spark ignition internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problem on a spark ignition type internal combustion engine that the reaction of spark discharge with an electric field generates plasma to ignite an air/fuel mixture while using microwaves to generate the plasma, that the amount of the plasma to be generated is determined by the intensity of the electric field by the microwaves and the great amount of plasma reacts with the spark discharge to wear an antenna exposed to high temperatures, thus resulting in such inconvenience that foreign matters remain in a combustion chamber and the radiating performance of the microwaves is deteriorated. <P>SOLUTION: In the spark ignition type internal combustion engine, the reaction of the plasma generated in the combustion chamber by the microwaves with the spark ignition caused by an ignition plug 1 ignites the air/fuel mixture as shown in Fig.1. A microwave radiating part is provided at a position in the combustion chamber 6 by the 1/2 of wavelengths of the microwaves or longer distant from the ignition plug. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a spark ignition internal combustion engine that generates an electric field in a combustion chamber, generates plasma by the electric field and spark discharge by an ignition plug, and ignites an air-fuel mixture.

  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 of generating plasma under atmospheric pressure, an electromagnetic wave, particularly using microwaves is considered. When the microwave is used, for example, a magnetron that outputs the microwave and an antenna that is provided so as to supply the microwave to the combustion chamber are connected by a coaxial cable that is connected to the waveguide. In this case, the amount of plasma generated is determined by the intensity of the electric field generated by the microwave. When the amount of plasma reacts with the spark discharge in the vicinity of the antenna in a large amount, the plasma is consumed by being exposed to a high temperature. For this reason, the exhaustion of the antenna has caused problems such as foreign matters remaining in the combustion chamber and the microwave radiation performance deteriorated.

  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 generates plasma by causing an electric field generated in a combustion chamber by electromagnetic waves to react with a spark discharge by an ignition plug and ignites an air-fuel mixture, The electromagnetic wave radiating portion is provided at a position of the combustion chamber separated from the spark plug by at least one half of the wavelength of the electromagnetic wave with at least one standing wave node interposed therebetween .

  According to such a configuration, since the distance between the spark plug and the electromagnetic wave radiation portion is at least half the wavelength of the electromagnetic wave, the electric field strength is at a position between the spark plug and the electromagnetic wave radiation portion. There is a region where becomes zero. Therefore, most of the plasma generated at the position of the spark plug does not reach the radiating portion, and it is possible to suppress the consumption of the radiating portion by the plasma.

For good production of plasma, the radiation of electromagnetic waves, preferably made provided at a position of 1/2 length away combustion chamber of a wavelength of an electromagnetic wave from the spark plug across the node of the standing wave . With such a configuration, the maximum electric field strength at the position of the radiating portion is also strong at the position of the spark plug. Therefore, a lot of plasma can be obtained at the position of the spark plug.

  The present invention is configured as described above, and can prevent the plasma generated at the position of the spark plug from expanding to the radiation portion of the electromagnetic wave, and can suppress the radiation portion from being consumed by the plasma.

Sectional drawing of embodiment of this invention. The graph which shows the positional relationship of the ignition plug and antenna in the same embodiment in relation to the voltage waveform of a microwave.

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

  In FIG. 1, 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 is of, for example, a three-cylinder double overhead camshaft (DOHC) type. The engine 100 includes a cylinder block 2 and a cylinder head 3. The cylinder block 2 includes a cylinder bore 5 in which a piston 4 reciprocates. The cylinder head 3 includes a combustion chamber 6. An intake port 7 and an exhaust port 8 are formed in the cylinder head, and the intake port 7 and the exhaust port 8 are opposed to each other centering on a spark plug 1 attached to substantially the center of the ceiling portion of the combustion chamber 6. Thus, the cylinder is opened so as to communicate with the combustion chamber 6 at two locations per cylinder. The intake port 7 is closed by the intake valve 9, and the intake camshaft 10 is rotated to open the intake valve 7. The exhaust port 8 is closed by the exhaust valve 11, and the exhaust camshaft 12 is rotated. The exhaust valve 11 is activated and opened. An antenna 13 serving as a radiating portion that radiates microwaves, which are electromagnetic waves for generating plasma, into the combustion chamber 6 is provided at the ceiling of the combustion chamber 6 of the cylinder head 3.

  The antenna 13 is, for example, of a monopole type, and the cylinder 13 is in a state where an end portion thereof is exposed to the combustion chamber 6 by an insulating material 13b filled in a through hole 13a that penetrates the cylinder head 3 and reaches the combustion chamber 6. The head 3 is provided so as to be electrically insulated. The tip of the antenna 13 is positioned at a part away from the spark plug 1 by an integral multiple of 1/2 the length of the microwave wavelength. Specifically, as shown in FIG. 2, the spark plug 1 is disposed at a position corresponding to the antinode of the standing wave where the intensity of the electric field formed by the microwave radiated from the antenna 13 is maximized, and at least The antenna 13 is located at a position corresponding to the antinode of the standing wave across one standing wave node. The antenna 13 is connected to a coaxial cable that guides microwaves output from a high-frequency generator (not shown), that is, a magnetron and a high-voltage AC generator including a control circuit that controls the output and output timing of the magnetron. The position has the property of becoming an antinode of standing waves.

  In such a configuration, the antenna 13 is provided in the manner described above for each cylinder of the engine 100 and radiates microwaves to generate plasma upon ignition. In the engine 100, when the air-fuel mixture in the combustion chamber 6 is ignited using the spark plug 1, the spark discharge of the spark plug 1 is caused to react with the electric field generated in the combustion chamber 6. It is larger than the spark discharge when the discharge does not react with the electric field.

  At the time of ignition, spark discharge is generated in the spark plug 1 by an ignition coil (not shown), and a high frequency electric field is generated by microwaves radiated from the antenna 13 almost simultaneously with or immediately after the spark discharge to generate plasma. Thus, the air-fuel mixture in the combustion chamber 6 is rapidly burned.

  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.

  In the configuration described above, the spark plug 1 is disposed in a region where the strength of the high-frequency electric field is maximized by being separated from the antenna 13 by an integral multiple of ½ the length of the wavelength of the microwave. Is positioned with respect to the spark plug 1 across a region where the intensity of the high-frequency electric field is the lowest, that is, almost zero. For this reason, when spark discharge is generated, plasma is sufficiently generated around the spark plug 1 where the strength of the high-frequency electric field is high. As a result, as described above, spark discharge is increased, plasma is generated, the ignition region is expanded, and combustion is expanded at a high combustion rate.

  On the other hand, the position of the antenna 13 becomes an antinode of the microwave, so that the intensity of the high-frequency electric field is strong, but most of the plasma generated around the spark plug 1 has a low high-frequency electric field intensity and suppresses the generation of plasma. When the microwave node is reached, the energy is lost and the state returns to the normal molecular state, so that the antenna 13 is not reached beyond the microwave node. As a result, the antenna 13 is not exposed to an excessively high temperature, and therefore consumption due to a temperature change is suppressed. Thereby, the member which comprises the antenna 13 can be made thin, and durability can be improved.

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

  In the above-described embodiment, the structure in which the antenna 13 protrudes from the ceiling portion of the combustion chamber 6 into the combustion chamber 6 has been described. However, the antenna may be provided in a recess opening in the cylinder bore 5. That is, since the antenna cannot protrude from the inner surface of the cylinder bore 5, it is provided in the recess. Even in this case, the distance between the antenna and the spark plug 1 is 1 of the wavelength of the microwave used. / 2 is set to a length that is an integral multiple of the length.

  In the above-described embodiment, the high frequency generator provided with the magnetron has been described. However, instead of the magnetron, a traveling wave tube or the like may be used, and further, a semiconductor microwave oscillation circuit may be provided.

  In the above-described embodiment, the microwave is used as the electromagnetic wave. However, the frequency of the electromagnetic wave is not limited to the microwave frequency range, and the polarity is alternately switched in the spark discharge portion of the spark plug 1. Any frequency that can generate an electric field and generate plasma can be used.

  Further, in the above-described embodiment, the distance between the antenna 13 and the spark plug 1 is set to a length that is an integral multiple of 1/2 the wavelength of the electromagnetic wave to be used. The antenna 13 may be disposed at a position that is at least a half of the wavelength of the electromagnetic wave to be used and that has the strength of the electric field enough to generate plasma.

  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 ... Spark plug 13 ... Antenna 6 ... Combustion chamber

Claims (2)

A spark ignition internal combustion engine that generates plasma by reacting an electric field generated by an electromagnetic wave in a combustion chamber with a spark discharge by an ignition plug, and ignites an air-fuel mixture,
A spark ignition internal combustion engine in which an electromagnetic wave radiation portion is provided at a position of a combustion chamber that is at least one- half of the wavelength of an electromagnetic wave, with at least one standing wave node sandwiched from an ignition plug. The radiating portion of the electromagnetic wave, across the nodes of the standing wave from the spark plug formed by providing a position of 1/2 length away combustion chamber of a wavelength of an electromagnetic wave according to claim 1 spark ignition type internal combustion engine according.

Images