JP2011007162A - Method for controlling spark-ignition internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve problem of a conventional spark-ignition internal combustion engine wherein when plasma is generated in the combustion chamber using a magnetron, if discharge is made from an antenna which emits the microwave from the magnetron, an air-fuel mixture is ignited at an unintended timing, and a required torque cannot be provided.SOLUTION: In this method for controlling a spark-ignition internal combustion engine in which the electric field generated by an electric field generating means for generating the electric field in the combustion chamber is reacted with a spark discharge by an ignition plug for igniting an air-fuel mixture, the electric field generated by the electric field generating means is set to an intensity which is weaker than the electric field generated by the ignition plug during spark discharge and at which discharge into the combustion chamber is disabled.

Description

  The present invention relates to a control method for a spark ignition internal combustion engine that reacts an electric field generated in a combustion chamber with a spark discharge by an ignition plug to generate plasma and ignite 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 for generating plasma under atmospheric pressure, a method using a magnetron is considered. When plasma is generated in a combustion chamber using a magnetron, it is necessary to provide an electrode, that is, an antenna for radiating microwaves from the magnetron, on the spark plug or in the vicinity thereof, such as the auxiliary electrode of Patent Document 1 described above.

  In such a case, for example, if the output of the magnetron is increased according to the load of the internal combustion engine, a discharge may occur between the antenna and the combustion chamber wall. That is, the antenna originally forms a high-frequency electric field for generating plasma in the combustion chamber. In such an antenna, when a discharge occurs prior to the spark plug, there is a high possibility that the air-fuel mixture will be ignited at an unintended timing. Therefore, there is a possibility that the required torque cannot be obtained because it is different from the ignition and combustion at the original ignition timing.

  Therefore, the present invention aims to eliminate such problems.

  That is, the spark ignition type internal combustion engine control method according to claim 1 of the present application generates plasma by reacting the electric field generated by the electric field generating means for generating an electric field in the combustion chamber with the spark discharge by the spark plug. A method of controlling a spark ignition internal combustion engine that ignites an air-fuel mixture, wherein the electric field generated by the electric field generating means is weaker than the electric field generated by the spark plug during spark discharge, and cannot be discharged into the combustion chamber. It is characterized by setting to a strong intensity.

  According to such a configuration, the electric field generated by the electric field generating means is lower than the intensity of the electric field generated by the spark plug and is incapable of discharging into the combustion chamber, so that the electric field is formed. In the meantime, no discharge occurs other than the spark discharge of the spark plug. Therefore, the compressed air-fuel mixture is prevented from being ignited carelessly at a timing other than the ignition timing.

  As an electric field generating means for generating an electric field, an electromagnetic wave generator for generating electromagnetic waves of various frequencies, an AC voltage generator for applying an AC voltage to a pair of electrodes arranged in a combustion chamber, and a pulsating current to a pair of electrodes Examples thereof include a pulsating voltage generator that applies a voltage.

  Examples of the electromagnetic waves generated by the electromagnetic wave generator include microwaves and various radio communications such as high frequencies including frequencies used in amateur radio.

  The AC voltage output from the AC voltage generator has a frequency equal to the above-described high frequency.

  The pulsating voltage generator need only generate a DC voltage whose voltage periodically changes, and the waveform of the DC voltage may be arbitrary. That is, the pulsating voltage in the present application changes from a reference voltage including 0 volt to a pulse voltage that changes to a constant voltage at a constant cycle or a voltage that increases or decreases sequentially at a fixed cycle, for example, AC voltage is half-wave rectified. Such a DC voltage having such a waveform, and a DC voltage obtained by applying a DC bias to the AC are included. In this case, the fixed period may correspond to the frequency at the above-described high frequency. The waveform is not limited to that described above, and may be a sine wave, a sawtooth wave, a triangular wave, or the like.

  Further, the spark ignition type internal combustion engine control method according to claim 2 of the present application reacts with the electric field generated in the combustion chamber by the laser and the spark discharge by the spark plug to generate plasma to ignite the mixture. A control method for a spark ignition internal combustion engine, characterized in that, when an electric field is generated by a laser, laser energy is set to a level at which ignition is impossible.

  The laser is generated by a laser oscillation device capable of changing the output, and is configured to irradiate the combustion chamber through an optical fiber.

  The present invention is configured as described above, and by suppressing the discharge through the electric field generating means for forming an electric field, the air-fuel mixture can be reliably obtained at the intended ignition timing and at the position of the spark plug. Can ignite and burn.

BRIEF DESCRIPTION OF THE DRAWINGS Structure explanatory drawing which shows schematic structure of embodiment of this invention. The flowchart which shows the control procedure of the embodiment. The block diagram which shows the structure of the electromagnetic wave generator which can be used in embodiment of this invention. The block diagram which shows the structure of the alternating voltage generator which can be used in embodiment of this invention. FIG. 6 is a circuit diagram showing an example of an H bridge circuit in FIG. 5.

  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. The intake system 1 of the engine 100 is provided with a throttle valve 2 that opens and closes in response to an accelerator pedal (not shown), and a surge tank 3 is provided downstream of the throttle valve 2. A fuel injection valve 5 is further provided in the vicinity of the end on the cylinder head 4 side where the surge tank 3 communicates, and the fuel injection valve 5 is controlled by the electronic control unit 6. An antenna 9 constituting an electric field generating means for generating an electric field in the combustion chamber 7 is attached to the ceiling portion of the combustion chamber 7 with the spark plug 8 and a microwave generator 11 described later. The antenna 9 in this embodiment is a monopole antenna and is attached to a position near the spark plug 8 on the ceiling of the combustion chamber 7. An ignition coil 10 that is integrally provided with an igniter is attached to the ignition plug 8 in a replaceable manner. The antenna 9 is rod-shaped, is attached to the wall of the combustion chamber 7 via an insulator, and is provided so as to protrude into the combustion chamber 7. The antenna 9 is connected to the microwave generator 11 via a waveguide and a coaxial cable (not shown). In the exhaust system 12, a three-way catalyst (hereinafter referred to as catalyst 13) is disposed in a pipe line leading to a muffler (not shown), and an O ₂ sensor 14 is attached upstream thereof.

  The microwave generator 11 that is an electromagnetic wave generator includes a magnetron 15 and a control circuit 16 that controls the magnetron 15. The microwave output from the magnetron 15 is applied to the antenna 9 through a waveguide and a coaxial cable. Further, the control circuit 16 is configured to receive the microwave generation signal n output from the electronic control unit 6, and the control circuit 16 outputs the microwave output from the magnetron 15 based on the input microwave generation signal n. It controls the wave output timing and output power.

  The electronic control unit 6 is mainly configured by a microcomputer system including a central processing unit 18, a storage device 19, an input interface 20, and an output interface 21. The central processing unit 18 controls the operation of the engine 100 by executing a program described later stored in the storage device 19.

Information necessary for controlling the operation of the engine 100 is input to the central processing unit 18 via the input interface 20, and the central processing unit 18 sends a control signal to the fuel via the output interface 21. Output to the injection valve 5 or the like. Specifically, the input interface 20 includes an intake pressure signal a output from an intake pressure sensor 22 for detecting the pressure of intake air in the surge tank 3, and a rotation speed sensor 23 for detecting the engine speed. , An engine speed signal b output from the idle switch 24 for detecting the open / closed state of the throttle valve 2, and a water temperature signal output from the water temperature sensor 25 for detecting the cooling water temperature of the engine 100. d, an intake air temperature signal e output from the intake air temperature sensor 26 for detecting the temperature of fresh air taken in by the engine 100, and an oxygen concentration in the exhaust gas discharged from the combustion chamber 7 through the exhaust valve. A voltage signal f output from the O ₂ sensor 14 is input. On the other hand, the output interface 21 outputs a fuel injection signal p to the fuel injection valve 5, an ignition signal m to the igniter 10, a microwave generation signal n to the microwave generator 11, and the like. ing.

  The electronic control device 6 uses the intake pressure signal “a” output from the intake pressure sensor 22 and the rotation speed signal “b” output from the rotation speed sensor 23 as main information, and is determined according to various operating conditions of the engine 100. The basic injection time is corrected by the correction coefficient to determine the opening time of the fuel injection valve 5, that is, the final energization time of the injector, and the fuel injection valve 5 is controlled by the determined energization time so that the fuel corresponding to the engine load is supplied. A program for injecting fuel into the intake system 1 from the fuel injection valve 5 is incorporated.

  In this engine 100, in a normal operation state after starting, the microwave generated by the microwave generator 11 is radiated from the antenna 9 into the combustion chamber 7 in accordance with the output timing described above, and the electric field generated thereby. And spark discharge by the spark plug 8 are reacted to generate plasma and ignite the air-fuel mixture. The electric field may be generated almost simultaneously with the start of the spark discharge, immediately after the start of the spark discharge, or immediately before the start of the spark discharge. When plasma is generated, an electric field is formed in the combustion chamber 7 in a direction orthogonal to the spark discharge by the spark plug 8 by applying a microwave to the antenna 9. It should be noted that “immediately after the start of spark discharge” is preferably at the start of induction discharge constituting the spark discharge at the latest.

  Specifically, the spark discharge by the spark plug 8 becomes plasma in the electric field, and the flame nucleus at the beginning of flame propagation combustion is larger than the ignition of only the spark discharge by igniting the mixture with the plasma. At the same time, combustion is promoted by generating a large amount of radicals in the combustion chamber 7.

  This is because the flow of electrons due to the spark discharge and the ions and radicals generated by the spark discharge are vibrated and meandered by the influence of the electric field, resulting in a longer path length and a dramatic increase in the number of collisions with surrounding water and nitrogen molecules. This is due to the 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 ignition region for the air-fuel mixture dramatically increases, and the flame kernel that starts the flame propagation combustion also increases.

  As a result, the air-fuel mixture is ignited by the plasma generated by the reaction between the spark discharge and the electric field, so that the ignition region is expanded and the two-dimensional ignition of only the spark plug 8 is changed to the three-dimensional ignition. Therefore, the initial combustion is stabilized, the combustion rapidly propagates into the combustion chamber 7 with the increase of the radicals described above, and the combustion expands at a high combustion rate.

  In such a configuration, the engine 100 forms a spark discharge in the combustion chamber 7 by the spark plug 8, forms an electric field by the antenna 9, reacts the spark discharge and the electric field, generates plasma, and generates an air-fuel mixture. Is controlled by a control program that detects the operating state of the engine 100 and adjusts the high-frequency power supplied to the antenna in accordance with the detected operating state. In this control program, the intensity of the electric field is set to an intensity that is weaker than the electric field formed by the spark plug 8 during spark discharge and cannot be discharged into the combustion chamber 7 via the antenna 9. . The intensity of the electric field is controlled so as to be always lower than the set electric field intensity by controlling the output of the magnetron 15.

  Hereinafter, a schematic procedure for controlling the internal combustion engine 100 will be described with reference to a flowchart shown in FIG.

  In step S1, the operating state of engine 100 is detected. The operating state of the engine 100 is detected based on, for example, the engine speed and the intake pipe pressure. In this case, the operation state is detected by combining low load, medium load and high load with respect to low rotation, medium rotation and high rotation, respectively.

  In step S2, the output of the magnetron 15 is determined based on the detected operating state. The output of the magnetron 15 is set to be small when the operating state of the engine 100 is low rotation and low load, and to be large when the operation state is high rotation and high load. In this case, an upper limit value is set for the output of the magnetron 15. That is, the output of the magnetron 15 is such that the strength of the electric field formed in the combustion chamber 7 is weaker than the strength of the electric field formed when the spark plug 8 is subjected to spark discharge even in a high rotation and high load operating state. In addition, the upper limit is set to an output sufficient to form an electric field having a strength that disables discharge between the antenna 9 serving as the electric field supply electrode and the inner wall of the combustion chamber 7 serving as the ground electrode for the supply electrode. It is limited.

  In step S3, the magnetron 15 is controlled so that the determined output is obtained.

  As described above, the output of the magnetron 15 is controlled in accordance with the operating state of the engine 100. However, since the upper limit output is regulated by the upper limit value, between the antenna 9 and the combustion chamber 7 inner wall. There is no discharge. Therefore, in each cylinder, the air-fuel mixture can be ignited at the position of the spark plug 8 at each set ignition timing. Therefore, the engine 100 can be operated in a good combustion state by the amplification of the spark discharge by the electric field, that is, the spark discharge enlarged by the plasma generated by the reaction between the electric field and the spark discharge.

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

  The microwave generator may be a traveling wave tube or the like instead of the magnetron as described above, and may further include a semiconductor microwave oscillation circuit.

  In addition, in the above-described embodiment, a monopole antenna has been described, but a beam antenna may be used.

  Furthermore, the center electrode of the spark plug 8 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.

  On the other hand, the frequency of the electromagnetic wave in the electromagnetic wave generator is not limited to the microwave frequency band, and may be any frequency that can generate an electric field in the spark discharge portion of the spark plug 8 to generate plasma. Therefore, as the electromagnetic wave generator, one having a configuration as shown in FIG. 3 is suitable, for example.

  3 includes a transmitter 31 that oscillates an electromagnetic wave of, for example, 300 MHz, a matching tuner (or an antenna tuner) 33 that is connected to the output end of the transmitter 31 by a coaxial cable 32, and a matching tuner 33. A mixer 36 is connected to the output end by an unbalanced cable 34 and is also connected to an igniter 35. In this example, the center electrode 8 a of the spark plug 8 functions as an antenna that radiates electromagnetic waves. Therefore, the mixer 36 transmits the electromagnetic waves output from the transmitter 31 via the matching tuner 33 to the spark plug 8. While applying to the center electrode 8a, the ignition signal from the igniter 35 is applied to the center electrode 8a. The mixer 36 mixes the electromagnetic wave from the transmitter 31 and the ignition signal from the igniter 35.

  In this example, an electric field is generated between the center electrode 8a and the ground electrode 8b by electromagnetic waves from the transmitter 31. The generated electric field reacts with the spark discharge generated between the center electrode 8a and the ground electrode 8b to generate plasma and ignite the mixture.

  Instead of the electromagnetic wave generator described above, an AC voltage generator may be used. The AC voltage generator 40 shown in FIG. 4 boosts the voltage of the vehicle battery 41, for example, about 12V (volts) to 300 to 500V by the DC-DC converter 42 which is a booster circuit, and then exemplifies in FIG. The frequency is changed to an alternating current having a frequency of about 1 MHz to 500 MHz, preferably 100 MHz by the H bridge circuit 43, and further boosted to about 4 kVp-p to 8 kVp-p by the step-up transformer 44.

  In such an AC voltage generator 40, for example, when the center electrode 8a and the ground electrode 8b of the spark plug 8 are a pair of electrodes for generating an electric field, the AC voltage is the same as in the electromagnetic wave generator 30 described above. A mixer is disposed between the step-up transformer 44, the igniter, and the spark plug 8 serving as the output end of the power source. Then, by applying a high-voltage AC voltage between the center electrode 8a and the ground electrode 8b, an electric field in which the polarity is alternately switched in the frequency band is generated in the gap between the spark plugs 8 serving as a discharge region. Accordingly, the generated electric field and spark discharge react to generate plasma around the spark plug 8 and ignite the air-fuel mixture. In the case where the pair of electrodes is constituted by the center electrode 8a and the ground electrode 8b, a cylinder head, a cylinder block or a piston may be substituted for the ground electrode 8b.

  In addition to using the center electrode 8a and the ground electrode 8b of the spark plug 8 described above, the pair of electrodes may have a configuration in which electrodes are arranged at positions sandwiching the spark plug 8. That is, a pair of electrodes are arranged facing each other at a predetermined distance. In this case, the pair of electrodes are arranged so that the spark plug 8 is positioned between the electrodes. Also in this case, one of the electrodes may be replaced with a ground electrode, a cylinder head, a cylinder block, or a piston.

  Instead of such an AC voltage generator, a pulsating flow generator may be used. That is, instead of applying an alternating current between a pair of electrodes, an electric field is generated between the pair of electrodes by applying a pulsating voltage such as a pulse voltage. In the same way as the AC voltage generator, the pulsating flow generator converts the direct current supplied from the battery to DC? The voltage is boosted by a DC converter, and a pulsating flow is generated by intermittently applying a high-voltage direct current at a predetermined cycle. In the case of a pulsating flow generator, a switching circuit that is periodically turned on and off is used instead of the H-bridge circuit. By using such a pulsating flow generation circuit, an electric field can be generated between the pair of electrodes, and the same effect as in the above-described embodiment can be obtained.

  Next, another embodiment of the present invention will be described.

  In this other embodiment, an electric field is generated in the combustion chamber by a laser oscillation device that is an electromagnetic wave generator that constitutes the electric field generating means.

  The laser oscillation device has a configuration in which a laser diode, a lens assembly including a YAG (yttrium, aluminum, garnet) and a cylindrical lens are combined. This laser oscillation device controls the average output, that is, the laser energy by increasing or decreasing the number of pulses per second, for example, in a pulse oscillation system. The laser output from the laser oscillation device is sent to the combustion chamber 7 through an optical fiber. In this case, the optical fiber passes through the inside of the spark plug housing, and its tip is attached toward the gap between the center electrode and the ground electrode. Prior to the spark discharge, the laser is irradiated to a position where the spark discharge occurs.

  The laser emitted from the optical fiber is irradiated so as to be concentrated in the gap between the center electrode 8a and the ground electrode 8b of the spark plug 8, which is an electric field generation region and a spark discharge generation region. Therefore, the electric field can be generated at a desired position due to the directivity of the laser, and the plasma can be generated at the most suitable position for ignition of the air-fuel mixture.

  In such a configuration, similarly to the above-described embodiment, by controlling the output of the laser oscillation device, when generating an electric field by the laser, the laser energy is set to a non-ignitable level, and the laser is set in the combustion chamber. Irradiate. That is, the operating state of the engine 100 is detected based on the engine speed and the intake pipe pressure, the output of the laser oscillation device is determined based on the detected operating state, and the laser oscillation device is controlled so that the determined output is obtained. To do. As in the above-described embodiment, the relationship between the operating state and the output of the engine 100 is such that the output of the laser oscillation device is small when the rotation is low and the load is large, and is large when the rotation is high and the load is high. It is set.

  In such output control of the laser oscillation device, an upper limit value is set for the output so that ignition is impossible in an operation state of high rotation and high load. By controlling the output of the laser oscillation device in this manner, in each operating state, the laser energy generates an electric field sufficient to react with the spark discharge and generate plasma. In addition, even when the laser oscillation device irradiates the compressed air-fuel mixture, the laser energy does not heat the air-fuel mixture to a temperature sufficient for ignition, so that ignition due to laser irradiation does not occur.

  Therefore, in each cylinder, the air-fuel mixture can be ignited at the position of the spark plug 8 at each set ignition timing. As a result, the engine 100 can be operated in a good combustion state by the amplification of the spark discharge by the electric field, that is, the spark discharge enlarged by the plasma generated by the reaction between the electric field and the spark discharge.

  Note that the laser oscillation device is not limited to the solid-state laser oscillation device having the above-described configuration, and may be a well-known device that varies the laser energy, or may be a continuous oscillation type.

  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 6 ... Electronic controller 7 ... Combustion chamber 8 ... Spark plug 15 ... Magnetron 18 ... Central processing unit 19 ... Memory | storage device 20 ... Input interface 21 ... Output interface 9 ... Antenna

Claims (2)

A control method for a spark ignition internal combustion engine that generates plasma by reacting with an electric field generated by an electric field generating means for generating an electric field in a combustion chamber and a spark discharge by an ignition plug to ignite an air-fuel mixture,
A control method for a spark ignition type internal combustion engine, wherein an electric field generated by an electric field generating means is set to a strength that is weaker than an electric field generated by a spark plug during spark discharge and cannot be discharged into a combustion chamber. A control method for a spark ignition internal combustion engine that generates plasma by reacting with an electric field generated in a combustion chamber by a laser and spark discharge by an ignition plug to ignite an air-fuel mixture,
A control method for a spark ignition type internal combustion engine, wherein an electric field is generated by a laser and laser energy is set to a level at which ignition is impossible.

Images