JP2010196513A - Spark-ignition internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a spark-ignition internal combustion engine solving the following problem: when ignition is caused by reaction of plasma with spark discharge, the plasma is generated by a microwave; however, if the plasma exists after igniting an air-fuel mixture, combustion speed is further increased by the plasma to cause excessively sudden combustion, and as a result, a desired torque cannot be obtained. <P>SOLUTION: In this spark-ignition internal combustion engine, the plasma generated in a combustion chamber by an electromagnetic wave is reacted with the spark discharge by an ignition plug, thereby igniting the air-fuel mixture. An electromagnetic wave radiation section is provided in the position of the combustion chamber with radiation of the electromagnetic wave blocked out by a piston when ignition timing is delayed. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a spark ignition 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 ignition is performed in a plasma atmosphere as in the above-mentioned Patent Document 1, the ignition is strengthened by plasma, and the combustion rapidly expands into the combustion chamber. This means that combustion is good, but if plasma is present after ignition, the plasma may further increase the combustion rate, resulting in excessively rapid combustion.

  In the case of an internal combustion engine using a crank mechanism, such excessively rapid combustion may not provide the desired torque. Also, depending on the operating conditions of the internal combustion engine, the ignition timing may be retarded to make combustion slow, but there is a problem that slow combustion does not occur if plasma exists after ignition. In order to suppress such excessively rapid combustion, plasma generation may be stopped after ignition. However, the response speed when the magnetron is intermittently oscillated and stopped is much slower than the speed of the internal combustion engine for automobiles and the speed at which the driving conditions change, so the plasma is intermittently controlled by controlling the magnetron. However, it has been difficult to make the configuration to generate automatically.

  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 plasma generated in a combustion chamber by electromagnetic waves and spark discharge by an ignition plug, and radiating portions of electromagnetic waves When the ignition timing is retarded, the piston is provided at the position of the combustion chamber where the radiation of electromagnetic waves is blocked.

  According to such a configuration, when the ignition timing is not retarded, the electromagnetic wave radiation portion is not blocked by the piston from the electromagnetic wave radiation during ignition. Therefore, plasma is generated in the combustion chamber by electromagnetic waves. After this, when the piston reaches the operating position for retarding the ignition timing, the piston blocks the radiation of electromagnetic waves. Accordingly, the generation of plasma due to the emission of electromagnetic waves is stopped, and excessively rapid combustion can be suppressed.

  Further, when it is necessary to operate the internal combustion engine in a slow combustion state and the ignition timing is retarded near the top dead center, the electromagnetic wave radiation portion is blocked by the piston during ignition. Therefore, since no plasma is generated in the combustion chamber, an intended slow combustion state can be realized.

  In such a configuration, in order to be able to block the emission of electromagnetic waves according to the operating state, the electromagnetic wave radiating part has a plurality of radiation ends provided at different positions according to the engine rotation speed Is preferred.

  The present invention is configured as described above, and by controlling the emission of electromagnetic waves by the operation of the piston, it is possible to control the reaction between the spark discharge and the plasma, thus effectively suppressing excessively rapid combustion. can do.

Sectional drawing of embodiment of this invention. Sectional drawing when a radiation | emission part is obstruct | occluded in embodiment of this invention.

  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 3, 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, two openings per cylinder are provided so as to communicate with the combustion chamber 6. 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. A radiation unit 13 that radiates microwaves, which are electromagnetic waves for generating plasma, to the combustion chamber 6 through the cylinder bore 5 is provided at a position near the cylinder head 3 of the cylinder block 2.

  The radiating portion 13 passes through the cylinder block 2 to reach the cylinder bore 5, the antenna 13b disposed in the through hole 13a, and the antenna 13b until the through hole 13a is sealed inside the through hole 13a. And a dielectric 13c to be filled. When the piston 4 reaches the top dead center, the radiating portion 13 is disposed so that the radiating end 13d that is the end portion on the cylinder bore 5 side is blocked by the piston 4. That is, the position of the radiating end 13d is set to a position that is not blocked at the ignition timing when the ignition timing is advanced by a predetermined crank angle during normal operation. That is, this position is a position closed by the piston 4 as shown in FIG. 2 at the ignition timing where the ignition timing is retarded to a crank angle corresponding to a predetermined crank angle. In this case, the advanced ignition timing is the ignition timing at the crank angle at which the radiating end 13d is not blocked by the piston 4 in the crank angle until the piston 4 reaches top dead center in the compression process. The retarded ignition timing is the ignition timing after the top surface of the piston 4 passes through the radiation end 13d in the compression process. It should be noted that ignition is also included in the retarded ignition timing in the early stage of the expansion stroke.

  The radiating end 13d is flush with the inner surface of the cylinder bore 5 or slightly recessed. The antenna 13b is connected to a coaxial cable that guides a microwave output from a high-frequency generator (not shown), that is, a high-voltage AC generator including a magnetron and a control circuit that controls the output of the magnetron.

  In such a configuration, the radiating unit 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 by using the spark plug 1, the spark discharge of the spark plug 1 is caused to react with the plasma generated in the combustion chamber 6. The discharge is larger than the spark discharge in the case where the discharge does not react with the plasma.

  At the time of ignition, a spark discharge is generated in the spark plug 1 by an ignition coil (not shown), and a plasma is generated by superimposing the spark discharge and a high-frequency electric field generated by the microwave radiated from the radiating unit 13. 6 is a configuration in which the air-fuel mixture in 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. In addition, by continuing to apply a high-frequency electric field by electromagnetic waves even after the spark discharge is completed, the electrons, radicals, and ions that are generated when the above plasma is generated vibrate and collide with other atoms and ions in a chain. It is possible to maintain the state.

  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 such a configuration, in the case of the advanced ignition timing, after plasma is generated at the ignition timing, the piston 4 passes through the top dead center before reaching the top dead center, and the top surface of the piston further reaches the radiation end. Since the piston 4 closes the radiation end 13d of the radiating portion 13 until the crank angle position corresponding to the position lower than the position 13d is reached, the microwave radiation is blocked. For this reason, plasma is generated and maintained from the time of the spark discharge until the radiation end 13d is closed by the piston 4, but no plasma is generated after the radiation end 13d is closed. Therefore, as described above, after the initial combustion is stabilized and the combustion expands at a high combustion rate, the combustion proceeds in a state where there is no plasma.

  Further, when the ignition timing is set after the piston top surface reaches the position of the radiating end 13d, that is, when the ignition timing is retarded, the radiating end 13d is closed by the piston 4 at the time of ignition. 6 is not emitted. Therefore, since there is no expansion of the ignition region, stabilization of initial combustion, and expansion of combustion at a high combustion speed as described above, it is possible to perform moderate combustion corresponding to the retard of the ignition timing.

  The present invention is not limited to the above embodiment.

  In the above-described embodiment, the radiation unit 13 includes the antenna 13b. However, the through hole 13a constituting the radiation unit 13 functions as a waveguide for guiding microwaves and is embedded in the dielectric 13c. The antenna may be omitted. Therefore, such a radiation | emission part 13 is comprised with the through-hole 13a and the dielectric material 13c with which the inside is filled.

  In the above-described embodiment, the radiation portion 13 is provided only in one place. However, the distance from the combustion chamber 6 is different from that of the cylinder bore 5 so that it functions at different positions according to the engine speed. A plurality of them may be provided. That is, in this case, it is provided at a position that is not closed at the ignition timing in normal operation, and corresponds to the ignition timing that is advanced according to the engine speed in the section from the position until the piston 4 reaches top dead center. Thus, it is provided at a position that is not closed at those ignition timings.

  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 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.

DESCRIPTION OF SYMBOLS 1 ... Spark plug 4 ... Piston 6 ... Combustion chamber 13 ... Radiation part 13d ... Radiation end

Claims (2)

A spark ignition internal combustion engine that ignites an air-fuel mixture by reacting plasma generated in a combustion chamber by electromagnetic waves and spark discharge by an ignition plug,
A spark ignition internal combustion engine in which an electromagnetic wave radiation portion is provided at a position of a combustion chamber where a piston blocks electromagnetic wave radiation when the ignition timing is retarded.   The spark ignition internal combustion engine according to claim 1, wherein the electromagnetic wave radiation portion includes a plurality of radiation ends provided at different positions according to the engine rotation speed.