JP2007309274A - Combustion condition determining device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To stably prevent false determination of a combustion state due to noise, in a system for detecting an ion current generated along with combustion of air fuel mixture inside a combustion chamber of an internal combustion engine via an electrode of an ignition plug and determining the combustion state based on the detection value. <P>SOLUTION: Detection charge amount Qi is determined by time quadrature of an ion current detection value i within a predetermined detection section set corresponding to a generation section of noise (corona discharge), and noise charge amount Qn is determined by multiplying charge part capacity Cp and charge voltage Vp of the ignition plug 27. When the detection charge amount Qi is compared with the noise charge amount Qn, if the detection charge amount Qi exceeds the noise charge amount Qn, it is determined that determination of the combustion state by a combustion ion current is possible, and the determination of the combustion state is permitted. If the detection charge amount Qi is smaller than the noise charge amount Qn, it is determined that determination of the combustion state by the combustion ion current is difficult due to much noise, and the determination of the combustion state is prohibited. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention detects an ionic current generated by combustion of an air-fuel mixture in a combustion chamber of an internal combustion engine through an electrode of a spark plug, and determines a combustion state based on the detected value. It is invention regarding.

  In recent years, focusing on the characteristics that ions are generated when the air-fuel mixture burns in the cylinder of an internal combustion engine, the ion current generated in the cylinder at each ignition is detected via the electrode of the ignition plug, and the ion current is detected. A technique for determining a combustion state based on a value has been developed. For example, in Patent Document 1 (Japanese Patent Application Laid-Open No. 2005-155634), either an ion current peak value or an integral value is detected in an ignition operation period and a combustion period, and incomplete combustion or ignition is performed based on the detected value. The failure is judged.

  By the way, in the process of smoldering fouling of the spark plug (the state where carbon generated during incomplete combustion adheres to the insulator surface of the spark plug), the carbon remaining on the insulator surface of the spark plug and the center electrode It is known that corona discharge occurs between the two. When this corona discharge occurs, the corona discharge noise superimposed on the ion current signal is misjudged as an ionic current due to combustion, and the combustion state is judged. As a result, misfire or incomplete combustion actually occurs. However, it may not be detected.

As a countermeasure against this, as shown in Patent Document 2 (Japanese Patent Laid-Open No. 10-300634), a insulator potential detection electrode for detecting the potential of the surface of the center electrode insulator of the spark plug is provided, and the potential detected by the insulator potential detection electrode is provided. In some cases, the presence or absence of noise is determined from the change in the noise and the determination of the combustion state is prohibited when noise is generated, thereby preventing erroneous determination of the combustion state due to noise.
JP-A-2005-155634 (pages 4 to 5 etc.) Japanese Patent Laid-Open No. 10-300634 (pages 2 to 3 etc.)

  However, in the technique disclosed in Patent Document 2, the presence or absence of noise is determined from the change in potential on the surface of the center electrode insulator of the spark plug. According to the results of experiments by the inventors, the potential on the surface of the center electrode insulator is determined. Change also occurs due to changes in the engine operating state (engine speed, load factor, etc.). Therefore, if the presence or absence of noise is determined from the change in potential on the surface of the center electrode insulator, the center due to the change in engine operating state There is a possibility that a change in potential on the surface of the electrode insulator is erroneously determined as a change due to noise, and as a result, an ion current detection value in a normal combustion state may be erroneously determined as noise.

  The present invention has been made in view of such circumstances. Therefore, the object of the present invention is to be able to stably prevent misjudgment of the combustion state due to noise without being affected by changes in the engine operating state. Another object of the present invention is to provide a combustion state determination device for an internal combustion engine that can improve the determination accuracy of the combustion state.

  In order to achieve the above object, an invention according to claim 1 is directed to an ion current detection means for detecting an ion current generated by combustion of an air-fuel mixture in a combustion chamber of an internal combustion engine through an electrode of a spark plug; In a combustion state determination device for an internal combustion engine comprising a combustion state determination unit that determines a combustion state based on an ion current detection value of an ion current detection unit, generation of noise superimposed on the ion current detection value of the ion current detection unit A charge amount detecting means for obtaining a detected charge amount by time-integrating the detected ion current value within a predetermined detection interval set corresponding to the interval, and a noise charge based on a charging portion capacity and a charging voltage of the spark plug A noise charge amount calculating means for calculating a quantity, wherein the combustion state determining means compares the detected charge amount with the noise charge amount and is based on the detected ion current value. It is obtained so as to determine the validity / invalidity of the constant execution enable / disable or combustion state determination result.

In general, the main noise superimposed on the detected ion current value is generated by corona discharge, and there is a relationship that as the amount of charge of corona discharge increases, the noise becomes larger and it becomes easier to erroneously determine the combustion state. Here, since the charge amount of the corona discharge depends on the charge amount charged in the charging portion (center electrode insulator portion) of the spark plug, the charge amount of the corona discharge and hence the noise charge amount is calculated from the charge amount of the charging portion of the spark plug. Can be estimated. The charge amount of the charging part of the spark plug is calculated by the product of the charging part capacity and the charging voltage.
Charge amount of charging part = charging part capacity x charging voltage

  In view of such circumstances, the present invention obtains the detected charge amount by time-integrating the ion current detection value within a predetermined detection interval set corresponding to the noise generation interval, The noise charge amount is calculated based on the capacity and the charging voltage, and the detection charge amount is compared with the noise charge amount to enable / disable the combustion state determination based on the ion current detection value or to enable / disable the combustion state determination result. Judgment is made. In this way, it becomes possible to judge the charge generation state of the combustion ions based on the charge amount of the corona discharge (noise charge amount), and to determine the noise generation state, and to change the engine operating state. Without being affected, it is possible to stably prevent erroneous determination of the combustion state due to noise, and improve the determination accuracy of the combustion state.

  By the way, as shown in FIG. 2, the generation pattern of the corona discharge includes “continuous corona discharge” continuously generated when the in-cylinder pressure immediately after ignition is high, and intermittently after the in-cylinder pressure decreases. There is a “spike corona discharge” that occurs. In general, the continuous corona discharge generation section is a section from after ignition to the vicinity of ATDC 60 ° C. A, and the spike corona discharge generation section is a section after ATDC 60 ° C. A.

  In consideration of such a corona discharge generation pattern, as in claim 2, the detection interval for detecting the detected charge amount includes a first detection interval corresponding to a continuous corona discharge generation interval, and spike corona discharge. A first detection charge amount and a second detection charge amount are obtained by time-integrating the ion current detection value for each detection interval by dividing into a second detection interval corresponding to the generation interval, and the first detection interval. And the second noise charge amount in the second detection interval is calculated based on the charging portion capacity and the charging voltage of the ignition plug in each detection interval, and detected in the first detection interval. Only when it is determined that the first detected charge amount is less than or equal to the first noise charge amount and the second detected charge amount detected in the second detection section is less than or equal to the second noise charge amount, the ion current detection. In value If the determination of the combustion state is prohibited or the combustion state determination result is invalidated, and it is determined that the detected charge amount is larger than the noise charge amount in one or both of the first detection interval and the second detection interval, A combustion state determination based on the detected ion current value may be executed to validate the combustion state determination result.

  As described above, when the detection period is divided into the first detection period corresponding to the generation period of the continuous corona discharge and the second detection period corresponding to the generation period of the spike corona discharge, the noise charge amount and the generation of noise are generated for each detection period. The state can be evaluated with high accuracy, and the noise / combustion ion discrimination accuracy can be further improved. Moreover, since the detection charge amount and the noise charge amount are compared for each detection section divided into two detection sections, misfire can be detected even in a region where misfire cannot be detected by general conventional peak value determination. Thus, the misfire-detectable region can be expanded as compared with the conventional case.

  Further, as in claim 3, when it is determined that the combustion state determination based on the detected ion current value is prohibited or the combustion state determination result is invalid from the comparison result between the detected charge amount and the noise charge amount, It may be determined that the combustion is complete. Thereby, misfire or incomplete combustion can be detected with high accuracy.

  By the way, after the start of the internal combustion engine, until the warm-up is sufficiently performed, the carbon adhesion region on the surface of the charging portion (center electrode insulator portion) of the spark plug is expanded and smoldering fouling proceeds. As the internal combustion engine warms up and the spark plug temperature becomes sufficiently high, the carbon adhering to the surface of the charged part of the spark plug gradually burns out and expands the burnout area. Gradually recovers. During this smoldering fouling recovery period (the period until carbon is almost burned out), the charged part capacity of the spark plug is larger than usual, and the carbon remaining on the charged part surface of the spark plug and the center electrode Corona discharge is likely to occur between the two.

  In consideration of this point, the charged part capacity of the spark plug used for calculating the noise charge amount is set based on the standard capacity of the charged part when new (no smoldering). The charging plug capacity of the spark plug is preferably increased during a predetermined period (a period until the carbon is almost burned out) in the recovery process of the smoldering contamination of the spark plug. In this way, it is possible to easily set the charged portion capacity according to the smoldering state of the spark plug, and to accurately calculate the noise charge amount during the smolder recovery process in which corona discharge is likely to occur. Ion discrimination accuracy can be further improved.

  In the present invention, the charging voltage of the spark plug may be actually measured by the voltage detection method described in, for example, Patent Document 2 (Japanese Patent Laid-Open No. Hei 10-300494). Since it is necessary to newly provide a circuit, the manufacturing cost increases and the demand for cost reduction cannot be satisfied.

  Therefore, in consideration of the characteristic that the charging voltage of the spark plug changes according to the operating state of the internal combustion engine, the charging voltage of the spark plug is set according to the operating state of the internal combustion engine as in claim 5 to reduce noise. It is preferable to calculate the charge amount. In this way, it is not necessary to newly provide a detection electrode and a voltage detection circuit as in Patent Document 2, and the cost reduction requirement can be satisfied.

  Further, the charging voltage of the spark plug in the second detection section may be set higher than that in the first detection section. Thereby, the charging voltage in each detection section can be set with high accuracy.

  Hereinafter, two Examples 1 and 2, which embody the best mode for carrying out the present invention, will be described.

A first embodiment of the present invention will be described with reference to FIGS.
First, the circuit configuration of the ignition control system will be described with reference to FIG.
One end of the primary coil 22 of the ignition coil 21 is connected to the battery 23, and the other end of the primary coil 22 is connected to the collector of the power transistor 25 built in the igniter 24. One end of the secondary coil 26 is connected to a spark plug 27, and the other end of the secondary coil 26 is connected to the ground via two Zener diodes 28 and 29.

  The two Zener diodes 28 and 29 are connected in series in opposite directions, a capacitor 30 is connected in parallel to one Zener diode 28, and an ion current detection resistor 31 is connected in parallel to the other Zener diode 29. A potential Vin between the capacitor 30 and the ionic current detection resistor 31 is input to the inverting input terminal (−) of the inverting amplifier circuit 33 via the resistor 32 and is inverted and amplified. The output voltage V of the inverting amplifier circuit 33 is ionized. The current detection signal is input to the engine control circuit 34. The ion current detection circuit 35 includes Zener diodes 28 and 29, a capacitor 30, an ion current detection resistor 31, an inverting amplification circuit 33, and the like. The ion current detection circuit 35 and the engine control circuit 34 are used to detect an ion current detection device (ion ion). Current detection means).

  During engine operation, the power transistor 25 is turned on / off at the rise / fall of the ignition signal transmitted from the engine control circuit 34 to the igniter 24. When the power transistor 25 is turned on, a primary current flows from the battery 23 to the primary coil 22. After that, when the power transistor 25 is turned off, the primary current of the primary coil 22 is cut off and a high voltage is electromagnetically induced in the secondary coil 26. This high voltage causes spark discharge between the electrodes 36 and 37 of the spark plug 27. This spark discharge current flows from the ground electrode 37 of the spark plug 27 to the center electrode 36, is charged to the capacitor 30 via the secondary coil 26, and flows to the ground side via the Zener diodes 28 and 29. After the capacitor 30 is charged, the ion current detection circuit 35 is driven using the charging voltage of the capacitor 30 regulated by the Zener voltage of the Zener diode 28 as a power source, and the ion current is detected as described later.

  On the other hand, the ion current flows in the opposite direction to the spark discharge current. In other words, after ignition is finished, a voltage is applied between the electrodes 36 and 37 of the spark plug 27 by the charging voltage of the capacitor 30, so that ions generated when the air-fuel mixture burns in the cylinder are connected between the electrodes 36 and 37. Although an ionic current flows, the ionic current flows from the center electrode 36 to the ground electrode 37, and further flows from the ground side through the ion current detection resistor 31 to the capacitor 30. At this time, the input potential Vin of the inverting amplifier circuit 33 changes according to the change of the ionic current flowing through the ionic current detection resistor 31, and the voltage V corresponding to the ionic current is output to the engine control circuit 34 from the output terminal of the inverting amplifier circuit 33. Is output. An ion current is detected from the output voltage V of the inverting amplifier circuit 33.

  The engine control circuit 34 is mainly composed of a microcomputer, and corresponds to an operating state detected by a rotation angle detection sensor 38 (crank angle sensor), a load detection sensor 39 (intake air amount detection sensor, intake pressure detection sensor) and the like. While performing fuel injection control and ignition timing control, the output of the ion current detection circuit 35 is used to detect the peak value Ii, integral value Qi, ion output time Ti, etc. of the ion current in a predetermined combustion ion detection section. Determine the combustion state (misfire, preignition, knocking, etc.).

  Next, how the ion current waveform detected by the ion current detection circuit 35 changes during normal combustion and when corona discharge occurs will be described with reference to FIG.

  As shown in FIG. 2 (d), immediately after the start of energization of the primary winding 22 of the ignition coil 21 (immediately after the ignition signal is switched from OFF to ON), a pulse-like noise current having a short time width is induced. LC resonance is generated by the residual magnetic energy on the secondary side of the ignition coil 21 (immediately after the ignition signal is switched from ON to OFF), and thereafter, a current waveform of ions (hereinafter referred to as “combustion ions”) generated by combustion during normal combustion. Appears. In the first embodiment, the combustion state (misfire, preignition, knocking, etc.) is determined based on at least one of the peak value Ii, the integral value Qi, and the ion current output time Ti of the combustion ions that appear after LC resonance.

  On the other hand, the generation pattern of corona discharge that occurs in the process of smoldering fouling of the spark plug 27 (the state in which carbon generated during incomplete combustion adheres to the insulator portion surface of the spark plug 27) is shown in FIG. As shown in FIG. 2, “continuous corona discharge” continuously generated when the in-cylinder pressure immediately after ignition is high, and intermittently after the in-cylinder pressure decreases as shown in FIG. There is “spike corona discharge”. In general, the continuous corona discharge generation section is a section from after ignition to the vicinity of ATDC 60 ° C. A, and the spike corona discharge generation section is a section after ATDC 60 ° C. A.

  If such noise due to corona discharge is detected as combustion ions, it may not be detected even if misfire or incomplete combustion actually occurs.

Therefore, in the first embodiment, one detection interval (interval from after ignition to ATDC 180 ° C. A) including the continuous corona discharge generation interval and the spike corona discharge generation interval is set. The ion current detection value i is integrated over time to obtain the detected charge amount Qi.
Qi = ∫idt

Furthermore, the noise charge amount Qn (corona discharge charge amount) is obtained by multiplying the capacitance Cp of the charging portion (center electrode insulator portion) of the spark plug 27 by the charging voltage Vp.
Qn = Cp x Vp

  Then, the detected charge amount Qi is compared with the noise charge amount Qn, and if the detected charge amount Qi is equal to or greater than the noise charge amount Qn, it is determined that the combustion state can be determined by the combustion ion current, and the combustion state The determination is permitted (or the combustion state determination result may be validated). If the detected charge amount Qi is less than the noise charge amount Qn, it is determined that it is difficult to determine the combustion state by the combustion ion current due to the noise, and the determination of the combustion state is prohibited (or the combustion state determination result) May be invalidated).

  By the way, after the engine is started, until the warm-up is sufficiently performed, the carbon adhesion region of the charging portion of the spark plug 27 is expanded and smoldering fouling progresses, but after that, the warm-up of the engine is completed. As the temperature of the spark plug 27 becomes sufficiently high, the carbon adhering to the charged portion of the spark plug 27 gradually burns out and expands the burned area, and the smoldering fouling gradually recovers. During this smoldering fouling recovery period (a period until the carbon is almost burned out), the charged portion capacity of the spark plug 27 becomes larger than usual, and the carbon remaining on the charged portion surface of the spark plug 27 and the center Corona discharge easily occurs between the electrodes.

  In consideration of this point, in the first embodiment, the capacity Cp of the charging portion of the spark plug 27 used when calculating the noise charge amount Qn is the standard capacity of the charging portion (when no smoldering is present) For example, 5 pF) is set as a reference, and a predetermined period (a period until the carbon is almost burned out) of the recovery process of the smoldering contamination of the spark plug 27 is set by increasing the charged portion capacitance Cp of the spark plug 27 to, for example, 9 pF. Like to do.

  As for the detection of the charging voltage Vp of the spark plug 27, the charging voltage Vp of the spark plug 27 may be actually measured by a voltage detection method described in, for example, Japanese Patent Application Laid-Open No. 10-300634. However, in this case, since it is necessary to newly provide a detection electrode and a voltage detection circuit, the manufacturing cost increases, and the demand for cost reduction cannot be satisfied.

  Therefore, in the first embodiment, the charging voltage Vp of the spark plug 27 is changed to the engine operating state (for example, the engine speed and the load factor) in consideration of the characteristic that the charging voltage Vp of the spark plug 27 changes according to the engine operating state. ) Is calculated using a map or the like.

  The determination of the combustion state of the first embodiment described above is executed as follows by the engine control circuit 34 according to the combustion state determination routine of FIGS. 3 and 4. This routine is executed at a predetermined cycle during engine operation, and serves as a combustion state determination means in the claims.

  When this routine is started, first, in step 101, the engine operating state such as the engine rotation speed Ne and the load factor is detected based on output signals from the rotation angle detection sensor 38, the load detection sensor 39, and the like. Thereafter, the process proceeds to step 102, where a smoldering state determination routine (not shown) is executed to determine the smoldering state of the spark plug 27 based on the detected ion current value. The determination of the smoldering state may be performed by a method described in, for example, Japanese Patent Application Laid-Open No. 2003-83222. This smoldering state determination method detects current (leakage current) flowing in a period other than the ion current detection period (period in which combustion ions are not generated) at least twice during an engine operation at an appropriate sampling interval. The insulation resistance value of the spark plug 27 is calculated from the detected current value, and the smoldering state of the spark plug 27 is determined based on the insulation resistance value.

  Thereafter, the process proceeds to step 103, and it is determined whether or not smolder recovery is in progress (a predetermined period of the recovery process of smoldering stain) based on the determination result of the smoldering state in step 102. At this time, immediately after the determination result of the smoldering state in the step 102 is switched from “smoldering” to “no smoldering”, carbon still remains on the surface of the charged portion of the spark plug 27. Even after the determination result of the state is switched to no smoldering, the period until the carbon on the surface of the charged portion of the spark plug 27 is almost burned out is determined to be in the middle of smolder recovery. This period may be determined based on the travel distance, travel time, and the like. For example, when the travel distance exceeds a predetermined distance (for example, 50 km) after the determination result of the smoldering state is switched to no smolder, the spark plug 27 It may be determined that the carbon on the surface of the charged portion is almost completely burned out (that is, almost completely recovered from the smoldering state).

  If it is determined in step 103 that smolder recovery is in progress, the process proceeds to step 104, where the charged part capacitance Cp of the spark plug 27 is set to the standard capacity of the charged part when new (no smoldering) (5 pF in the first embodiment). ) To a predetermined amount, for example, set to 9 pF.

  On the other hand, if “No” is determined in Step 103, it is determined that the state is completely recovered from the smoldering state, and the process proceeds to Step 105, where the charged portion capacity Cp of the spark plug 27 is set to a new one (when there is no smoldering). ) Of the charging portion (5 pF in the first embodiment).

  Thereafter, the routine proceeds to step 106, where the charging voltage Vp of the spark plug 27 is calculated from the charging voltage map according to the current engine operating state (the load factor and the engine speed Ne in the first embodiment). In this charging voltage map, for example, in a region where the load factor is a predetermined value or less, the charging voltage Vp is set to a constant value regardless of the load factor and the engine speed Ne, but in a region where the load factor is a predetermined value or more. The charging voltage Vp increases as the load factor increases, and the charging voltage Vp increases as the engine speed Ne increases.

After calculating the charging voltage Vp, the routine proceeds to step 107, where the charging portion capacitance Cp of the spark plug 27 and the charging voltage Vp are multiplied to determine the noise charge amount Qn.
Qn = Cp x Vp
The processing in steps 102 to 107 serves as noise charge amount calculation means in the claims.

  Thereafter, the process proceeds to step 108 in FIG. 4, and it is determined whether or not it is within the detection zone (the zone from after ignition to ATDC 180 ° C. in the first embodiment). The ion current detection value i detected by the ion current detection circuit 35 is read, and in the next step 110, the ion current peak value Ii, the ion current integrated value Qi (detected charge amount), and the ion current output time Ti in the detection section are detected. To do. The processing of these steps 108 to 110 serves as charge amount detection means in the claims.

  Thereafter, when the detection interval end timing is reached, “No” is determined in Step 108, “Yes” is determined in Step 111, the process proceeds to Step 112, and the ion current integrated value Qi (detected charge) in the detection interval is determined. Amount) is compared with the noise charge amount Qn, and if the ion current integrated value Qi (detected charge amount) is equal to or greater than the noise charge amount Qn, it is determined that the combustion state can be determined by the combustion ion current, and combustion Allow state judgment. In this case, the routine proceeds to step 113, where the ion current peak value Ii in the detection section is directly used as the combustion ion current peak value Iion, the ion current output time Ti is used as it is as the combustion ion current output time Tion, and the ion current integrated value Qi ( The net combustion ion charge amount Qion is obtained by subtracting the noise charge amount Qn from the detected charge amount). Thereafter, the routine proceeds to step 114, where the combustion state (misfire, preignition, knocking, etc.) is determined by a map or the like based on the combustion ion current peak value Iion, the combustion ion charge amount Qion, and the combustion ion current output time Tion.

  It should be noted that the combustion state may be determined based on any one or two of the combustion ion current peak value Iion, the combustion ion charge amount Qion, and the combustion ion current output time Tion. Further, as the combustion ion charge amount Qion, the ion current integrated value Qi in the detection section may be used as it is.

  On the other hand, if it is determined in step 112 that the ion current integrated value Qi (detected charge amount) is smaller than the noise charge amount Qn, it is determined that there is a lot of noise and it is difficult to determine the combustion state by the combustion ion current. Thus, determination of the combustion state is prohibited (or the combustion state determination result may be invalidated). In this case, the process proceeds to step 115 and it is determined that misfire (or incomplete combustion) has occurred.

  According to the first embodiment described above, the detected charge amount Qi is obtained by integrating the ion current detection value i with time within a predetermined detection interval set corresponding to the noise (corona discharge) generation interval, and ignition. The charge portion capacitance Cp of the plug 27 and the charging voltage Vp are multiplied to calculate the noise charge amount Qn, and the detected charge amount Qi is compared with the noise charge amount Qn to permit / prohibit execution of combustion state determination (or combustion state) Since the determination result is valid / invalid), the charge amount of the combustion ions is legitimately evaluated based on the charge amount (noise charge amount Qn) of the corona discharge, and the noise generation state is determined. This makes it possible to stably prevent erroneous determination of the combustion state due to noise without being affected by changes in the engine operating state, and improve the determination accuracy of the combustion state.

In the first embodiment, one detection interval (interval from after ignition to, for example, ATDC 180 ° C.) including the continuous corona discharge generation interval and the spike corona discharge generation interval is set. In the second embodiment of the present invention shown in FIG. 2, the first detection interval (interval from after ignition to, for example, ATDC 60 ° C. A) corresponding to the generation interval of continuous corona discharge, and the second detection interval corresponding to the generation interval of spike corona discharge The first detection charge amount Qi1 and the second detection charge amount Qi2 are obtained by dividing the detection value i into time divisions (for example, a section from ATDC 60 ° C. to ATDC 180 ° C.) and time-integrating the ion current detection value i for each detection section. I am doing so. Then, the first noise charge amount Qn1 in the first detection interval and the second noise charge amount Qn2 in the second detection interval are multiplied by the charging portion capacitance Cp of the ignition plug 27 and the charging voltages Vp1 and Vp2 in each detection interval, respectively. Ask.
Qn1 = Cp x Vp1
Qn2 = Cp x Vp2

  In this case, the charging portion capacitance Cp of the spark plug 27 uses the same value in the first detection section and the second detection section, but the charging voltage Vp varies depending on the in-cylinder pressure, and thus the charging voltage Vp1 in the first detection section. And the charging voltage Vp2 in the second detection section are calculated separately using the two maps shown in FIGS.

  Then, it is determined that the first detected charge amount Qi1 detected in the first detection interval is equal to or less than the first noise charge amount Qn1, and the second detected charge amount Qi2 detected in the second detection interval is equal to or less than the second noise charge amount Qn2. Only when it is determined that the combustion state determination is prohibited or the combustion state determination result is invalid, and it is determined that the detected charge amount is larger than the noise charge amount in one or both of the first detection interval and the second detection interval. For example, the determination of the combustion state is executed, and the combustion state determination result is validated.

  The determination of the combustion state of the second embodiment described above is executed by the engine control circuit 34 as follows according to the combustion state determination routines of FIGS. When this routine is started, first, in step 201, the engine operating state such as the engine rotation speed Ne and the load factor is detected based on output signals from the rotation angle detection sensor 38, the load detection sensor 39, and the like. Thereafter, the process proceeds to step 202, and the smoldering state of the spark plug 27 is determined by the same method as in the first embodiment. Thereafter, the process proceeds to step 203, where it is determined in the same manner as in the first embodiment whether or not smolder recovery is in progress (a predetermined period of the recovery process of smoldering stain) based on the determination result of the smoldering state in step 202. If it is determined that smolder recovery is in progress, the process proceeds to step 204, where the charged part capacity Cp of the spark plug 27 is increased from the standard capacity (5 pF in the second embodiment) of the charged part when new (no smoldering). For example, it is set to 9 pF.

  On the other hand, if “No” is determined in step 203, it is determined that the state is completely recovered from the smoldering state, and the process proceeds to step 205, where the charged portion capacity Cp of the spark plug 27 is set to a new one (when there is no smoldering). ) Of the charging portion (5 pF in the second embodiment).

  Thereafter, the process proceeds to step 206, where it is determined whether or not it is within the first detection interval (in this embodiment, the interval from after ignition to ATDC 60 ° C. A). The charging voltage Vp1 of the spark plug 27 in the first detection section is determined based on the charging voltage map in the first detection section of FIG. 8 according to the current engine operating state (load factor and engine speed Ne in the second embodiment). calculate. The charging voltage map in the first detection section is set to a constant value (for example, 1 kV) in the entire load region and the entire rotational speed region.

After the calculation of the charging voltage Vp1 in the first detection section, the process proceeds to step 208, where the charging portion capacity Cp of the spark plug 27 and the charging voltage Vp1 in the first detection section are multiplied to obtain the noise charge amount Qn1 in the first detection section. Is calculated.
Qn1 = Cp x Vp1

  Thereafter, the process proceeds to step 209, and the ion current detection value i detected by the ion current detection circuit 35 is read. In the next step 210, the ion current peak value Ii1 and the ion current integration value Qi1 (first detection interval) in the first detection section. Charge amount) and ion current output time Ti1.

  After that, the process proceeds to step 211 in FIG. 7 to determine whether or not it is within the second detection interval (the interval from ATDC 60 ° C. A to ATDC 180 ° C. A in the second embodiment). In step 212, the charging voltage Vp2 of the spark plug 27 in the second detection section is set to the second detection section in FIG. 9 according to the current engine operating state (load factor and engine speed Ne in the second embodiment). It is calculated from the charging voltage map. In the charging voltage map of the second detection section, in a region where the load factor is equal to or less than a predetermined value (for example, 40% or less), the charging voltage Vp2 is set to a constant value (for example, 1 kV) regardless of the load factor and the engine rotation speed Ne. However, in a region where the load factor is equal to or greater than a predetermined value, the charging voltage Vp2 increases as the load factor increases, and the charging voltage Vp2 increases as the engine speed Ne increases.

After the calculation of the charging voltage Vp2 in the second detection interval, the process proceeds to step 213, where the charging portion capacitance Cp of the spark plug 27 and the charging voltage Vp2 in the second detection interval are multiplied to obtain the noise charge amount Qn2 in the second detection interval. Is calculated.
Qn2 = Cp x Vp2

  Thereafter, the process proceeds to step 214, and the ion current detection value i detected by the ion current detection circuit 35 is read. In the next step 215, the ion current peak value Ii2 and ion current integration value Qi2 (second detection) in the second detection section. Charge amount) and ion current output time Ti2.

Thereafter, when the second detection interval end timing is reached, “No” is determined in Step 211, “Yes” is determined in Step 216, the process proceeds to Step 217, and the first detected in the first detection interval is detected. It is determined whether the detected charge amount Qi1 is greater than or equal to the first noise charge amount Qn1, or whether the second detected charge amount Qi2 detected in the second detection interval is greater than or equal to the second noise charge amount Qn2. As a result, if the detected charge amount is determined to be greater than or equal to the noise charge amount in either or both of the first detection interval and the second detection interval, it is determined that the combustion state can be determined based on the combustion ion current, and combustion is performed. Allow state judgment. In this case, the process proceeds to step 218, the ion current peak value Ii1 in the first detection interval and the ion current peak value Ii2 in the second detection interval are compared, and the larger one is selected as the combustion ion peak value Iion. A value obtained by adding the ion current output time Ti1 in the detection section and the ion current output time Ti2 in the second detection section is a combustion ion current output time Tion, and further, the first detected charge amount Qi1 and the second detected charge amount Qi2 The net combustion ion charge amount Qion is obtained by subtracting the sum value (Qn1 + Qn2) of the first noise charge amount Qn1 and the second noise charge amount Qn2 from the total value (Qi1 + Qi2).
Qion = (Qi1 + Qi2)-(Qn1 + Qn2)

The total value (Qi1 + Qi2) of the first detected charge amount Qi1 and the second detected charge amount Qi2 may be used as the combustion ion charge amount Qion.
Qion = Qi1 + Qi2

  Thereafter, the process proceeds to step 219, and the combustion state (misfire, preignition, knocking, etc.) is determined by a map or the like based on the combustion ion current peak value Iion, the combustion ion charge amount Qion, and the combustion ion current output time Tion. It should be noted that the combustion state may be determined based on any one or two of the combustion ion current peak value Iion, the combustion ion charge amount Qion, and the combustion ion current output time Tion.

  On the other hand, in step 217, the first detected charge amount Qi1 detected in the first detection interval is equal to or less than the first noise charge amount Qn1, and the second detected charge amount Qi2 detected in the second detection interval is the second noise charge. If it is determined that the amount is Qn2 or less, it is determined that it is difficult to determine the combustion state based on the combustion ion current due to the noise, and the determination of the combustion state is prohibited (or the combustion state determination result may be invalidated). . In this case, it progresses to step 220 and determines with misfire (or incomplete combustion).

  In the second embodiment described above, since the first detection interval corresponding to the generation interval of the continuous corona discharge and the second detection interval corresponding to the generation interval of the spike corona discharge are divided, noise charge is detected for each detection interval. As a result, the noise generation state can be accurately evaluated, and the noise / combustion ion discrimination accuracy can be further improved. Moreover, since the detection charge amount and the noise charge amount are compared for each detection section divided into two detection sections, misfire can be detected even in a region where misfire cannot be detected by general conventional peak value determination. Thus, the misfire-detectable region can be expanded as compared with the conventional case.

  Needless to say, the present invention is not limited to the first and second embodiments, and can be implemented with various modifications, for example, the method for determining the combustion state may be appropriately changed.

It is a circuit diagram which shows the structure of the ignition control system and ion current detection circuit in Example 1 of this invention. The relationship among the ignition signal, in-cylinder pressure, generation period, detection current waveform during normal combustion, detection current waveform when continuous corona discharge occurs, and detection current waveform when spike corona discharge occurs in Example 1 of the present invention will be described. It is a time chart. It is a flowchart which shows the flow of a process of the combustion state determination routine in Example 1 of this invention (the 1). It is a flowchart which shows the flow of a process of the combustion state determination routine in Example 1 of this invention (the 2). The relationship among the ignition signal, in-cylinder pressure, generation period, detection current waveform during normal combustion, detection current waveform when continuous corona discharge occurs, and detection current waveform when spike corona discharge occurs in Example 2 of the present invention will be described. It is a time chart. It is a flowchart which shows the flow of a process of the combustion state determination routine in Example 2 of this invention (the 1). It is a flowchart which shows the flow of a process of the combustion state determination routine in Example 2 of this invention (the 2). It is a figure which shows an example of the charging voltage map of a 1st detection area. It is a figure which shows an example of the charging voltage map of a 2nd detection area.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 21 ... Ignition coil, 22 ... Primary coil, 23 ... Battery, 24 ... Igniter, 25 ... Power transistor, 26 ... Secondary coil, 27 ... Spark plug, 31 ... Ion current detection resistor, 33 ... Inversion amplification circuit, 34 ... Engine Control circuit (combustion state determination means, charge amount detection means, noise charge amount calculation means), 35 ... ion current detection circuit (ion current detection means), 36 ... center electrode, 37 ... ground electrode

Claims (6)

Ion current detection means for detecting ion current generated by combustion of the air-fuel mixture in the combustion chamber of the internal combustion engine through the electrode of the spark plug, and determining the combustion state based on the ion current detection value of the ion current detection means A combustion state determination device for an internal combustion engine, comprising:
A charge amount detection means for obtaining a detected charge amount by time-integrating the ion current detection value within a predetermined detection section set corresponding to a noise generation section superimposed on an ion current detection value of the ion current detection means;
A noise charge amount calculating means for calculating a noise charge amount based on a charging portion capacity and a charging voltage of the spark plug;
The combustion state determination means compares the detected charge amount with the noise charge amount to determine whether to permit / inhibit execution of the combustion state determination based on the detected ion current value or whether the combustion state determination result is valid / invalid. A combustion state determination device for an internal combustion engine. The charge amount detection means divides the detection section into a first detection section corresponding to a continuous corona discharge generation section and a second detection section corresponding to a spike corona discharge generation section. The first detected charge amount and the second detected charge amount are obtained by time-integrating the detected ion current value with respect to time,
The noise charge amount calculating means calculates the first noise charge amount in the first detection interval and the second noise charge amount in the second detection interval based on the charging portion capacity and the charging voltage of the spark plug in each detection interval, respectively. Calculated,
The combustion state determining means is configured such that the first detected charge amount detected in the first detection interval is equal to or less than the first noise charge amount, and the second detected charge amount detected in the second detection interval is the first detection charge amount. Only when it is determined that the amount of noise charge is 2 or less, the determination of the combustion state based on the detected ionic current value is prohibited or the determination result of the combustion state is invalid, and either or both of the first detection interval and the second detection interval On the other hand, if it is determined that the detected charge amount is larger than the noise charge amount, a combustion state determination based on the detected ion current value is executed, and the combustion state determination result is validated. A combustion state determination device for an internal combustion engine according to claim 1.   If the combustion state determination means prohibits the determination of the combustion state based on the detected ion current value from the comparison result between the detected charge amount and the noise charge amount, or determines that the combustion state determination result is invalid, the combustion state determination means The combustion state determination device for an internal combustion engine according to claim 1 or 2, wherein it is determined that the combustion is complete.   The charging part capacity of the spark plug used when calculating the noise charge amount is set with reference to the standard capacity of the charging part when new, and the predetermined period of the recovery process of the smoldering stain of the spark plug is the The combustion state determination device for an internal combustion engine according to any one of claims 1 to 3, wherein the charging portion capacity is increased.   The internal combustion engine according to any one of claims 1 to 4, wherein the noise charge amount calculation means calculates a noise charge amount by setting a charging voltage of the spark plug according to an operating state of the internal combustion engine. Combustion state determination device.   The combustion state determination device for an internal combustion engine according to claim 2, wherein the noise charge amount calculation means sets a charging voltage of the spark plug in the second detection section higher than that in the first detection section.

Images