JP2011007157A - Method for controlling operation of spark-ignition internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve problem of a conventional spark-ignition internal combustion engine in which plasma atmosphere is used for ignition wherein though it is considered that the state of generation of the plasma atmosphere is adjusted to make the amount of plasma to follow up a variation in load, the output of magnetron does not follow up a variation in the speed of an internal combustion engine in the transient operating state when microwave is used to generate plasma, and the output of the microwave does not correspond to a torque required in the transient operating state, and therefore, the internal combustion engine is not brought into an intended transient operating state.SOLUTION: This method for controlling the operation of a spark-ignition internal combustion engine controls the intensity of an electric field based on the operating state of the spark-ignition internal combustion engine in which the electric field generated in a combustion chamber is reacted with a spark discharge by an ignition plug to generate plasma for igniting an air-fuel mixture. The transient operating state of the engine is detected, and the intensity of the electric field is controlled according to the detected transient operating state, and the ignition timing is controlled.

Description

  The present invention relates to an operation control method for a spark ignition type internal combustion engine in which an electric field generated in a combustion chamber reacts 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, the internal combustion engine adjusts the amount of fuel and intake air to be supplied in accordance with load fluctuations, in particular, a transient operation state when shifting from a steady operation state to a steady operation state. Similar to such fuel supply control, in the case of using a plasma atmosphere such as that of Patent Document 1, it is conceivable that the amount of plasma follows the load change by adjusting the generation state of the plasma atmosphere. ing.

  It is also known to use a magnetron as a source of microwaves in those that use electromagnetic waves, such as microwaves, to generate plasma. However, in the case of using a magnetron, the output of the magnetron may not follow the changing speed in the transient operation state of the internal combustion engine. Therefore, the microwave output corresponding to the torque required for the transient operation state is not obtained, and the intended transient operation state may not be achieved.

  Therefore, the present invention aims to eliminate such problems.

  That is, the spark ignition type internal combustion engine operation control method of the present invention is a spark ignition type internal combustion engine that generates plasma by reacting an electric field generated in a combustion chamber with a spark discharge by a spark plug to ignite an air-fuel mixture. A spark ignition type internal combustion engine operation control method for controlling electric field strength based on an operating state, detecting a transient operation state of the engine, controlling the electric field strength according to the detected transient operation state, and igniting timing It is characterized by controlling.

  According to such a configuration, the amount of plasma generated is controlled by controlling the intensity of the electric field, and at the same time, the ignition timing is controlled to control the torque. As a result, even if the amount of plasma is delayed with respect to the change in the transient operation state, such a follow-up delay can be compensated by the ignition timing control, and a smooth transient operation state can be maintained.

  In the above configuration, the control of the electric field strength and the ignition timing are specifically controlled by increasing the electric field strength and advancing the ignition timing when the detected transient operation state is an operation state in which the output is increased. In the case where the angle is changed or the detected transient operation state is an operation state in which the output is reduced, it is preferable to reduce the electric field strength and temporarily retard the ignition timing.

  As described above, the electric field generating means for generating an electric field includes 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 the combustion chamber, and a pair of electrodes. And a pulsating voltage generator for applying a pulsating voltage to the device.

  Examples of the electromagnetic waves generated by the electromagnetic wave generator include microwaves, high frequencies including frequencies used in various wireless communications such as amateur radio, and lasers having wavelengths shorter than those of microwaves. In the case of a laser, a laser oscillation device having a configuration different from that of other electromagnetic wave generation devices is used.

  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.

  The present invention is configured as described above, and controls the amount of plasma generated by controlling the strength of the electric field, and at the same time controls the ignition timing to control the torque. Even if it is delayed by this change, such a follow-up delay can be compensated by ignition timing control, and a smooth transient operation state can be maintained.

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. 5 is a circuit diagram showing an example of an H bridge circuit in FIG. 4.

  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 ignition plug 8 and an antenna 9 for generating plasma are attached to the ceiling portion of the combustion chamber 7. 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 a microwave generator 11 that is an electric field generating means 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 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 the engine 100, 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 the spark discharge by the spark plug 8. To generate plasma and ignite the air-fuel mixture. When generating plasma, an electric field is generated in the combustion chamber 7 in a direction perpendicular to the spark discharge by the spark plug 8 by applying a microwave to the antenna 9.

  At the time of ignition, spark discharge is generated in the spark plug 8 by an ignition coil (not shown), and an electric field is generated by microwaves almost simultaneously with the start of the spark discharge or immediately after the start of the spark discharge. In this configuration, the air-fuel mixture in the combustion chamber 7 is rapidly burned by generating plasma by reacting with an electric field. 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 detects a transient operation state, and an operation control program that controls the output of microwaves that are electromagnetic waves according to the detected transient operation state and controls the ignition timing is stored in the electronic control unit 6. Built-in. Specifically, in the control of the microwave output and the ignition timing, when the detected transient operation state is an operation state in which the output is increased, the microwave output is increased and the ignition timing is increased in order to increase the strength of the electric field. When the detected transient operation state is an operation state in which the output is decreased, the microwave output is decreased and the ignition timing is temporarily retarded in order to weaken the electric field strength.

  Hereinafter, a schematic procedure of operation control of the engine 100 will be described with reference to a flowchart shown in FIG.

  In step S1, it is determined whether or not the operating state of engine 100 is a transient operating state in which the output is increased during a transition period from one steady operating state to another steady operating state. The transient operation state is determined based on, for example, whether or not the intake pipe pressure per unit time is high. That is, when the engine 100 is in the acceleration operation state, the change in the intake pipe pressure per unit time, that is, the change speed of the intake pipe pressure increases by opening the throttle valve 2, and therefore the change speed of the intake pipe pressure. Is determined to be a transient operation state during acceleration when the value becomes greater than the first predetermined speed.

  If it is determined in step S1 that the state is a transient operation state in which the output is increased, that is, a transient operation state during acceleration, in step S2, the output of the microwave is increased to increase the electric field strength and advance the ignition timing. That is, the output of the microwave is increased by the control circuit 16 controlling the magnetron 15 when the microwave generation signal n is output from the electronic control device 6 to the microwave generation device 11. On the other hand, the advance angle of the ignition timing is controlled by an ignition signal output to the igniter 10.

  On the other hand, when it determines with it not being the transient operation state at the time of acceleration in step S1, it progresses to step S3. In step S3, it is determined whether or not the operating state of engine 100 is a transient operating state in which the output during a transition period from one steady operating state to another steady operating state is reduced. In this case, since the change speed of the intake pipe pressure becomes small, it is determined that the engine is in a transient operation state during deceleration when the change speed becomes smaller than the second predetermined speed.

  If it is determined in step S3 that the operation is a transient operation state in which the output is reduced, that is, a transient operation state during deceleration, in step S4, the output of the microwave is decreased to weaken the electric field strength and retard the ignition timing. On the other hand, if it is determined in step S3 that the engine is not in the transient operation state during deceleration, the process proceeds to step S5, and the microwave output maintains the output until then and the ignition timing is assumed to be in the steady operation state. Also, advance angle control corresponding to the steady operation state is implemented.

  In such a configuration, when the engine 100 enters a transient operation state, it is determined whether the transient operation state is during acceleration or deceleration, and a micro corresponding to each transient operation state is determined. Wave output and ignition timing control are performed. That is, the output of the microwave is controlled by changing the output of the magnetron 15. However, since the change in the output of the microwave is delayed, it may not follow the change in the operating state during the transition. . For example, in a transient operation state during acceleration, even if the microwave output is increased, the increase in torque does not follow the change in the operation state. The ignition timing is controlled in order to eliminate such a delay in torque increase and a delay in torque decrease in the transient operation state during deceleration.

  Therefore, the follow-up delay in the increase / decrease in the output of the microwave is compensated by the advance / retard control of the ignition timing. In other words, when the operating state shifts from one steady state to another, the plasma generated by the reaction between the electric field generated by the microwave and the spark discharge increases or decreases in response to the change in the operating state. Therefore, the necessary torque is insufficient, but the insufficient torque can ensure the necessary torque in each transient operation state by controlling the ignition timing. Therefore, a smooth transient operation state following the request can be maintained.

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

  In the above-described embodiment, the transient operation state is determined based on the intake pipe pressure. However, even if the determination is based on the change rate of the opening degree of the throttle valve 2 or the change rate of the degree of depression of the accelerator pedal. Good.

  In the above description, the monopole antenna has been described. However, the antenna is not limited to this, and there are various types such as a horn antenna and an antenna in which the center electrode of the spark plug functions as an antenna. Things can be used.

  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.

  Furthermore, the center electrode of the spark plug 1 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 such an electromagnetic wave generator 30, the intensity of the electric field to be generated can be increased by increasing or decreasing the output of the electromagnetic wave by changing the frequency of the electromagnetic wave, or by increasing or decreasing the output of the electromagnetic wave with the frequency kept constant. Control.

  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.

  Moreover, a laser oscillation apparatus is mentioned as an electromagnetic wave generator. As the laser oscillation device, a combination of a laser diode, a lens assembly including YAG (yttrium, aluminum, garnet) and a cylindrical lens can be used. The laser output from the laser oscillation device is sent to the combustion chamber via 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 preferably applied to a position where the spark discharge occurs. The intensity of the electric field is controlled by increasing or decreasing the output (intensity) of the laser.

  The laser emitted from the optical fiber concentrates in the gap and concentrates the electric field near the gap. 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.

  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. Similar to the AC voltage generator, the pulsating flow generator boosts the direct current supplied from the battery with a DC-DC converter and turns the high-voltage direct current into a pulsating flow at predetermined intervals. Thus, the voltage is boosted and applied to a pair of electrodes. 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.

  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.

6 ... Electronic control unit 7 ... Combustion chamber 8 ... Spark plug 15 ... Magnetron 18 ... Central processing unit 19 ... Storage device 20 ... Input interface 21 ... Output interface

Claims (3)

A spark ignition type internal combustion engine that controls the intensity of an electric field based on the operating state of a spark ignition type internal combustion engine that generates plasma by reacting an electric field generated in a combustion chamber with a spark discharge by an ignition plug and ignites an air-fuel mixture The operation control method of
Detects transient engine operating conditions,
An operation control method for a spark ignition type internal combustion engine, which controls the ignition timing while controlling the intensity of an electric field in accordance with a detected transient operation state.   The spark ignition type internal combustion engine operation control method according to claim 1, wherein when the detected transient operation state is an operation state in which the output is increased, the electric field strength is increased and the ignition timing is advanced.   2. The operation control method for a spark ignition type internal combustion engine according to claim 1, wherein when the detected transient operation state is an operation state in which the output is reduced, the electric field strength is reduced and the ignition timing is temporarily retarded.

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