JP2010101173A - Method for controlling operation of spark-ignition internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problems in a spark-ignition internal combustion engine improving ignition of an air-fuel mixture by using plasma, wherein, when rotation fluctuates by, for example, smoldering of an ignition plug, ignition timing adjustment control for reducing torque, for example, is performed with respect to a cylinder in an excellent combustion state, however, since the torque of the cylinder in the excellent combustion state is adjusted, a characteristic using the plasma may not be sufficiently utilized. <P>SOLUTION: This method for controlling the operation of a spark-ignition internal combustion engine controls output of an electromagnetic wave according to the operating condition of the spark-ignition internal combustion engine including a plurality of cylinders having combustion chambers and igniting the air-fuel mixture by reacting the plasma generated in each combustion chamber by the electromagnetic wave with spark discharge by the ignition plug. The combustion state of each cylinder is detected, and the output of the electromagnetic wave with respect to the cylinder with the detected combustion state most degraded is increased. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an operation control method for a spark ignition type internal combustion engine that ignites an air-fuel mixture by reacting plasma generated in a combustion chamber by electromagnetic waves with 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, even when the ignition of the air-fuel mixture is improved by using plasma as in Patent Document 1, rotation fluctuation may occur due to, for example, intake air filling variation or combustion variation due to deterioration over time. As described above, when the rotational fluctuation occurs, generally, control is performed to adjust the ignition timing so as to reduce the torque, for example, for the cylinder in a good combustion state in order to suppress variation.

  However, with such a configuration, the combustion state of the combustion state is adjusted so as to match the state of the cylinder where the combustion state is lowered, although a stable flame can be obtained using plasma. In order to adjust the torque of a good cylinder, there was a case where the characteristics using plasma could not be fully utilized.

  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 includes a plurality of cylinders having combustion chambers, and reacts plasma generated in the combustion chambers by electromagnetic waves and spark discharge by the spark plug to ignite the mixture. An operation control method for a spark ignition type internal combustion engine that controls the output of electromagnetic waves according to the operation state of the spark ignition type internal combustion engine, wherein the combustion state of each cylinder is detected, and the detected combustion state is the least It is characterized by increasing the output of electromagnetic waves.

  According to such a configuration, the generation state of plasma in the cylinder is improved by increasing the output of the electromagnetic wave to the cylinder in which the combustion state is the lowest. As a result, the combustion state of the cylinder is improved and approaches the torque of the cylinder where the torque remains. Therefore, variation in torque between cylinders is eliminated, and rotational fluctuations can be collected.

  The present invention is configured as described above, and by increasing the output of electromagnetic waves to the cylinder in which the combustion state is the lowest, the plasma generation state of the cylinder can be improved. As a result, the combustion state of the cylinder is improved, approaching the torque of the cylinder where the torque remains, the variation in torque between the cylinders is eliminated, and rotational fluctuations can be collected.

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

An engine 100 schematically shown in FIG. 1 is a spark-ignition four-cycle four-cylinder engine for an automobile. A throttle valve 2 that opens and closes in response to an accelerator pedal (not shown) is disposed in an intake system 1 thereof. A surge tank 3 is provided on the downstream side. A fuel injection valve 5 is further provided in the vicinity of one end communicating with the surge tank 3, and the fuel injection valve 5 is controlled by the electronic control unit 6. The cylinder head 31 forming the combustion chamber 30 is provided with an intake valve 32 and an exhaust valve 33, and with an ignition plug 18 that serves as an electrode for generating a spark and detecting an ionic current. Further, in the exhaust system 20, an O ₂ sensor 21 for measuring the oxygen concentration in the exhaust gas is located upstream of the three-way catalyst 22 which is a catalyst device arranged in a pipe line leading to a muffler (not shown). Is attached to. In FIG. 1, the configuration of one cylinder of engine 100 is shown as a representative.

The electronic control device 6 is mainly configured by a microcomputer system including a central processing unit 7, a storage device 8, an input interface 9, an output interface 11, and an A / D converter 10. The input interface 9 includes an intake pressure signal a output from an intake pressure sensor 13 for detecting the pressure in the surge tank 3, that is, an intake pipe pressure, and an output from a cam position sensor 14 for detecting the rotation state of the engine 100. Cylinder discrimination signal G1, crank angle reference position signal G2, engine speed signal b, vehicle speed signal c output from the vehicle speed sensor 15 for detecting the vehicle speed, idle switch for detecting the open / closed state of the throttle valve 2 The IDL signal d output from 16, the water temperature signal e output from the water temperature sensor 17 for detecting the coolant temperature of the engine 100, the current signal h output from the O ₂ sensor 21, etc. are input. On the other hand, the output interface 11 outputs a fuel injection signal f to the fuel injection valve 5 and an ignition pulse g to the spark plug 18.

  A bias power source 24 for measuring ion current is connected to the spark plug 18, and an ion current measuring circuit 25 is connected between the input interface 9 and the bias power source 24. The ignition plug 18, the bias power supply 24, and the ion current measurement circuit 25 constitute an ion current detection system 40. The bias power supply 24 applies a measurement voltage (bias voltage) for measuring an ion current to the spark plug 18 when plasma is generated. The ion current flowing between the inner wall of the combustion chamber 30 and the center electrode of the spark plug 18 and between the electrodes of the spark plug 18 by application of the measurement voltage is measured by the ion current measurement circuit 25. As the bias power source 24 and the ion current measuring circuit 25, various devices well known in the art can be applied.

  In addition to such an ion current detection system 40, an electromagnetic wave, for example, a microwave is supplied to the center electrode of the spark plug 18 in order to generate plasma in the combustion chamber 30. The microwave is output from a high voltage AC generator 52 including a magnetron 50 and a control circuit 51 that controls the magnetron 50. The control circuit 51 is configured to receive a high-voltage AC generation signal k output from the electronic control device 6. As the transmission path 53 for transmitting the microwave to the spark plug 18, a well-known one can be used. For example, a waveguide electrically connected to the magnetron 50, the waveguide and the spark plug 18 are connected to each other. It comprises a coaxial cable and a coaxial distributor that are electrically connected to the center electrode, and a continuously variable attenuator that is provided corresponding to each cylinder and transmitted to each spark plug 18. Therefore, the center electrode functions as an antenna that radiates microwaves. The control circuit 51 controls the output of the magnetron 50, that is, the output timing and output power of the microwave output from the magnetron 50 based on the input high-voltage AC generation signal. The output of the magnetron 50 is adjusted according to the operating state of the engine 100.

  In the above-described configuration, the electronic control unit 6 uses the intake pressure signal a output from the intake pressure sensor 13 and the rotation speed signal b output from the cam position sensor 14 as main information, and determines the operating state of the engine 100. The basic injection time (basic injection amount) is corrected by various correction coefficients determined accordingly to determine the fuel injection valve opening time, that is, the injector final energization time T, and the fuel injection valve 5 is controlled by the determined energization time. A program for injecting fuel corresponding to the engine load into the intake system 1 is incorporated. Further, while controlling the fuel injection of the engine 100 in this way, the electronic control unit 6 detects the combustion state of each cylinder and increases the microwave output to the cylinder in which the detected combustion state is the lowest. It is programmed like this.

  In this engine 100, in a normal operation state, a microwave generated by the high-voltage AC generator 52 is radiated from the center electrode of the spark plug 18 into the combustion chamber 30 in accordance with the output timing, and plasma generated thereby And spark discharge by the spark plug 18 are reacted to ignite the air-fuel mixture. When generating plasma, a microwave is applied to the center electrode, whereby a high-frequency electric field is formed in the combustion chamber 30 against a spark discharge by the spark plug 18.

  At the time of ignition, a spark discharge is generated in the spark plug 18 by an ignition coil (not shown), and a high-frequency electric field is generated by microwaves almost simultaneously with or immediately after the spark discharge to generate plasma, thereby generating a combustion chamber 30. It is the structure which burns the inside air-fuel mixture rapidly.

  Specifically, the spark discharge by the spark plug 18 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 18 is changed to the three-dimensional ignition. Accordingly, the initial combustion is stabilized, the combustion rapidly propagates into the combustion chamber 30 with the increase of the radicals described above, and the combustion expands at a high combustion rate.

  While the engine 100 is being operated by the ignition control of the air-fuel mixture as described above, the ion current generated in the combustion chamber 30 in each cylinder during combustion of the air-fuel mixture, that is, in the combustion stroke, is detected, and based on the detected ion current. Thus, the combustion state of each cylinder is detected, and the torque fluctuation of the engine 100 is suppressed. Next, this embodiment will be described with reference to the flowchart shown in FIG.

  In FIG. 2, in step S1, the ion current of each cylinder is detected in the order of ignition. The ion current is detected by the center electrode of the spark plug 18 immediately after the start of combustion. If the combustion state is good, the ion current becomes the maximum current value immediately after the piston reaches top dead center, and then decreases. To do. Therefore, such a characteristic of the ionic current can be detected to grasp the combustion state.

  When the detection of the ionic current is completed in the four cylinders, in step S2, the detected ionic currents are compared, and the cylinder having the smallest ionic current value is determined. That is, the minimum ion current value indicates that the combustion state in the cylinder in which the ion current value is detected is lower than that in other cylinders.

  In step S2, the microwave output for the cylinder having the lowest combustion state is increased. In this embodiment, since the continuous variable attenuator is provided in the transmission path 53, the continuous variable attenuator of the cylinder is controlled so that the output of the target cylinder increases. That is, each continuously variable attenuator is set to the same attenuation rate in the initial state. After starting the operation of the engine 100, the damping rate of the continuously variable attenuator of the cylinder in which the combustion state is minimized is decreased. As a result, the amount or rate at which the microwave output is attenuated in the continuously variable attenuator is reduced, and a microwave having a larger output than before the adjustment of the continuously variable attenuator is substantially applied to the center electrode of the spark plug 18. Is transmitted.

  In the above configuration, when the engine 100 is operated, if torque fluctuation occurs, the combustion state of each cylinder is determined based on the characteristics of the ionic current, and for the cylinder with the lowest combustion state, Control is performed to increase the output of the microwave.

  Therefore, among the combustion states that vary among the cylinders, the microwave output to the cylinder with the lowest combustion state is increased, thereby improving the plasma generation state and improving the combustion state of the cylinder. Can be made. In this way, by improving the combustion state of the cylinder in which the combustion state is the lowest, the combustion state of each cylinder approaches the cylinder with the best combustion state, and the difference in torque between the cylinders is reduced. Torque fluctuations can be suppressed without reducing the torque as a whole.

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

  In the above-described embodiment, the combustion state is determined by the current value of the ion current. However, it is determined by the time or crank angle during which the detected ion current exceeds the threshold, or after the measurement of the ion current is started. It may be one that is detected by an integral value of ion current values within a predetermined period. Such determination of the combustion state from the ion current characteristics from the characteristics of the ion current may be performed using a method known in this field.

  Further, the detection of the combustion state may be performed by attaching a pressure sensor to each cylinder and comparing the in-cylinder pressure of the combustion stroke in each cylinder. That is, in a cylinder with good combustion state, the pressure in the cylinder is high, and in a slow combustion state, that is, in a cylinder in which the combustion state is low, the pressure in the cylinder is low. By comparing the output signals that are output, it is possible to determine which cylinder has the lowest combustion state.

  Furthermore, the rotation fluctuation of the engine 100 may be detected to determine the cylinder having the lowest combustion state. That is, when the rotational fluctuation occurs in the engine 100, that is, when the torque is different for each cylinder, the rotational angular velocity of the crankshaft increases because the torque is large in a cylinder having a good combustion state. On the other hand, in the cylinder where the combustion state is the lowest, the torque is also smaller than that of a good cylinder, so the rotational angular velocity is small. Therefore, by comparing the rotational angular velocities at that time for each combustion stroke, the cylinder having the smallest rotational angular velocity can be determined as the cylinder in which the combustion state is the lowest.

  In addition, in the above-described embodiment, the output of the microwave transmitted to each cylinder is adjusted using a continuously variable attenuator. However, a waveguide corresponding to each cylinder is provided in the transmission path, and each waveguide is provided. The microwave output may be adjusted by making the wave tube variable. That is, by adjusting the length of each waveguide constituting the transmission path, the impedance of the waveguide is changed and the output of the microwave is adjusted. The tube length of the waveguide is adjusted using, for example, a stepping motor. Each waveguide communicates with the combustion chamber, and the end opened to the combustion chamber is closed by a dielectric.

  The antenna for radiating microwaves to the combustion chamber 30 may be a monopole antenna or a horn antenna provided so as to protrude from the combustion chamber 30.

  Further, the high-voltage AC generator may be a traveling wave tube or the like instead of the above-described magnetron, and may further include a semiconductor microwave oscillation circuit.

  Further, when the center electrode of the spark plug 18 is made to function as an antenna to form a high-frequency power feeding unit, if the high frequency is continuously applied to the center electrode at a constant voltage, the temperature of the center electrode excessively increases, The high frequency voltage is controlled to be lower than the upper limit temperature set based on the heat resistant temperature of the electrode.

  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.

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.

Explanation of symbols

6 ... Electronic control unit 7 ... Central processing unit 8 ... Storage unit 9 ... Input interface 11 ... Output interface
DESCRIPTION OF SYMBOLS 50 ... Magnetron 51 ... Control circuit 52 ... High voltage alternating current generator 18 ... Spark plug 30 ... Combustion chamber

Claims (1)

It has a plurality of cylinders with combustion chambers, and controls the output of electromagnetic waves according to the operating state of a spark ignition internal combustion engine that ignites an air-fuel mixture by reacting plasma generated in the combustion chambers by electromagnetic waves and spark discharge by spark plugs. An operation control method for a spark ignition internal combustion engine,
Detect the combustion state of each cylinder,
An operation control method for a spark ignition type internal combustion engine that increases an electromagnetic wave output to a cylinder in which the detected combustion state is the lowest.

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