JP5142087B2 - Ion current detection device for internal combustion engine - Google Patents

Description

  The present invention relates to an ionic current detection device for an internal combustion engine that detects an ionic current generated by combustion of an air-fuel mixture in a combustion chamber of each cylinder of the internal combustion engine through an electrode of a spark plug.

In recent years, in an ion current detection device of this type of internal combustion engine, in order to prevent erroneous determination of spike noise (spike-like corona discharge) generated by the insulator charge of the spark plug during a misfire as combustion ions, Some of them use an ion current detection ignition plug with noise countermeasures (see, for example, Patent Documents 1 to 4).
Japanese Patent Laid-Open No. 10-89221 JP 2005-129398 A JP 2005-129399 A Japanese Patent Laid-Open No. 11-219772

  As described above, even in the case of an internal combustion engine that uses an ion current detection spark plug with spike noise countermeasures, when replacing the spark plug on the user side, a heterogeneous spark plug with no spike noise countermeasure (general-purpose spark plug) There is a possibility that a spark plug will be attached.

  However, in the conventional ion current detection device, even when a different type of spark plug that does not deal with spike noise is installed, the installation of the different type of spark plug cannot be detected, so spike noise generated due to the insulator charge of the different type of spark plug at the time of misfire. May be erroneously determined as combustion ions, and may be erroneously determined as combustion despite misfire. Further, there is a possibility that combustion and misfire are erroneously determined even in a spark plug malfunction cylinder.

  The present invention has been made in view of such circumstances. Therefore, the object of the present invention is to install a heterogeneous spark plug that does not take countermeasures against spike noise in an ion current detector that uses a spark plug corresponding to spike noise. Another object of the present invention is to provide an ion current detection device for an internal combustion engine that can detect a cylinder or a spark plug malfunction cylinder.

In order to achieve the above object, the invention according to claim 1 is an ion current detecting means for detecting an ion current generated by combustion of an air-fuel mixture in a combustion chamber of each cylinder of an internal combustion engine through an electrode of a spark plug. In the ion current detecting device for an internal combustion engine, which uses a spark plug corresponding to a sudden current change (hereinafter referred to as “spike noise”) as the spark plug, a predetermined spike noise including a combustion stroke for each cylinder Spike noise counting means for analyzing the change pattern of the ion current detected by the ion current detecting means within the detection section and counting the number of occurrences of spike noise, and detecting spike noise of each cylinder counted by the spike noise counting means Spike noise for each cylinder depending on whether the number of occurrences of spike noise in the section is equal to or greater than a predetermined value Spike noise abnormal cycle determination means for determining whether or not it is a normal cycle, the number of ignition times and the number of occurrences of the spike noise abnormal cycle for each cylinder are counted, and the frequency of occurrence of the spike noise abnormal cycle (per predetermined ignition frequency) The number of occurrences of spike noise abnormal cycles is determined) and the cylinder in which the frequency of occurrence of the spike noise abnormal cycles is equal to or greater than the determination threshold is defined as a cylinder with a different type of spark plug that has not yet taken spike noise or a spark plug fault cylinder A spark plug abnormality detecting means for judging , wherein the spike noise counting means detects a peak point and / or a bottom point of a change pattern of the ion current detected by the ion current detecting means, and a current drop from the peak point Whether the rate and / or current rise rate from the bottom point is a predetermined value or more Means for determining whether or not pike noise is detected; means for detecting a saturating section in which the ion current detected by the ion current detecting means saturates and hardly changes; and detection of the peak and bottom points in the saturating section And a means for prohibiting the processing.

  Here, the spark plug corresponding to spike noise is, for example, a spark plug for which spike noise countermeasures have been taken or a spark plug of a predetermined type.

  The present invention pays attention to the fact that spike noise tends to occur frequently due to the insulator charge of the different type of spark plug when a misfire occurs when a different type of spark plug that does not take countermeasures against spike noise is installed or when the spark plug fails. It is a technical idea that determines a cylinder with frequent spike noise as a cylinder with a different type of spark plug that does not deal with spike noise or a cylinder with a failed spark plug. It is possible to prevent erroneous determination of spike noise as combustion ions at the time of failure.

In this case, when the spike current is detected by analyzing the change pattern of the ion current detected by the ion current detection means, the peak point of the change pattern of the ion current detected by the ion current detection means as in claim 1 and The bottom point is detected, and it is determined whether the spike noise is caused by whether the current decrease rate from the peak point and / or the current increase rate from the bottom point is equal to or greater than a predetermined value. It ’s fine. In this way, the peak point and the bottom point can be accurately detected from the ion current change pattern.

Furthermore, as in claim 1, and saturate the ion current detected by the ion current detecting means detects almost no change saturate section, it may be adapted to prohibit the detection processing of the peak point and a bottom point at this saturating section . In this way, it is possible to prevent the current change from the saturating state of the ionic current from being erroneously determined as spike noise.

Furthermore, as according to claim 2, in addition to the spike noise detection section including a combustion stroke, by setting the background noise detection section that does not include the combustion stroke, each said spike noise detection section in the background noise detecting section The number of occurrences of spike noise is counted, and the value obtained by subtracting and correcting the number of occurrences of spike noise in the spike noise detection section counted for each cylinder by the number of occurrences of spike noise in the background noise detection section is equal to or greater than a predetermined value. Whether or not it is a spike noise abnormal cycle may be determined for each cylinder.

  In general, spike noise is likely to occur in the spike noise detection section that includes the combustion stroke, and spike noise is less likely to occur in the background noise detection section that does not include the combustion stroke, so it is detected as spike noise in the background noise detection section. The number of generated background noises is detected. Therefore, if the number of spike noise occurrences in the spike noise detection section is subtracted and corrected by the number of spike noise (background noise) occurrences in the background noise detection section, the net noise excluding background noise generated in the spike noise detection section is excluded. The number of occurrences of spike noise can be detected.

  By the way, in the operating state where the combustion state of each cylinder is slow, the combustion ions may fluctuate relatively large in the spike noise detection section, and the fluctuation of the combustion ions may be erroneously determined as spike noise. Accordingly, there is a possibility that the detection accuracy of the number of occurrences of spike noise is lowered and the spike noise abnormal cycle is erroneously determined.

As a countermeasure, it is preferable to prohibit the spike noise abnormality cycle from being determined when the combustion state of each cylinder is slow as in the third aspect . In this way, it is possible to prevent the spike noise abnormality cycle from being erroneously determined due to fluctuations in the combustion ions in the operating state where the combustion state of each cylinder is slow. Here, the operating state in which the combustion state becomes slow is, for example, a specific operating region in which the combustion speed becomes slow, etc., when the ignition timing is retarded, when the EGR rate is increased, or when the air-fuel ratio lean control is performed.

Alternatively, focusing on the fact that the combustion ions fluctuate relatively during the exhaust stroke when the combustion state of each cylinder becomes slow, the ion current detection means for each exhaust stroke in each cylinder as in claim 4. When the average value of the detected ion current signal is equal to or greater than a predetermined value, it may be determined that the combustion state of each cylinder of the internal combustion engine is slow and the spike noise abnormality cycle is prohibited. . In this way, it is possible to prevent the spike noise abnormality cycle from being erroneously determined due to the fluctuation of the combustion ions when the slow combustion state is entered. In addition, since it is possible to determine whether or not the engine is in the slow combustion state based on the ion current signal detected in the exhaust stroke, the operating conditions (for example, the ignition timing retardation amount, etc.) in which the combustion state becomes slow for each internal combustion engine are determined. There is also an advantage that it is not necessary to perform complicated work such as conformance.

Further, as in claim 5 , when the control state in which the combustion stability of each cylinder of the internal combustion engine is reduced, when the operation state of the internal combustion engine is in a predetermined low load region, and the smoldering state of the spark plug is not less than a predetermined amount The determination of the spike noise abnormal cycle may be prohibited in at least one of the cases. In this way, combustion ion fluctuations when the combustion stability of each cylinder of the internal combustion engine is reduced and the combustion state is slow, and the operating state of the internal combustion engine is in a low load region (for example, a deceleration region). It is possible to reliably prevent erroneous determination of spike noise abnormal cycles due to destabilization of combustion ions at the time and a decrease in ion current detection accuracy when the smoldering state of the spark plug progresses. Here, the control state in which the combustion stability is lowered is, for example, at the time of valve overlap increase control, ignition timing retard control, air-fuel ratio lean control, or the like.

  In addition, when the battery that supplies the power supply voltage to the ignition system is overloaded, the influence of the voltage fluctuation of the alternator appears relatively large, and the noise generated by this voltage fluctuation of the alternator is mistakenly determined as spike noise. As a result, the detection accuracy of the number of occurrences of spike noise is lowered, and there is a possibility that a spike noise abnormal cycle is erroneously determined.

As a countermeasure, as in claim 6, the battery may be adapted to prohibit the determination of the spike noise abnormal cycle when the overloaded state. In this way, it is possible to prevent the spike noise abnormal cycle from being erroneously determined by the voltage fluctuation noise of the alternator.

  In general, a heterogeneous spark plug that does not take countermeasures against spike noise cannot obtain an effect of neutralizing the insulator charge in the event of a misfire, and therefore has a characteristic that spike noise tends to occur frequently due to the insulator charge of the spark plug in the event of a misfire. Due to such characteristics, in the case of different types of spark plugs that have not taken countermeasures against spike noise, if spike noise occurs frequently, there is a high possibility of misfire.

From this point of view, as described in claim 7 , when a spike noise abnormal cycle is detected, the spike noise abnormal cycle may be determined as a misfire cycle. In this way, it is possible to detect misfire even when a different type of spark plug that does not deal with spike noise is mounted.

In this case, even when different spark plug attachment of spike noise without countermeasures, in consideration of the characteristics of the ion current output time of the ion current detecting means at the time of misfire becomes shorter than the time of ignition, as in claim 8, each cylinder Depending on whether or not the number of spike noise occurrences within the spike noise detection interval is not less than a predetermined value and the ion current output time of the ion current detection means is not more than a predetermined time, a spike noise abnormal cycle and a misfire cycle are performed for each cylinder. You may make it determine whether there exists. In this way, it is possible to improve the misfire detection accuracy when a different type of spark plug with no spike noise countermeasure is attached.

Further, immediately after the ignition timing (immediately after the end of discharge), a noise waveform of LC resonance is generated by the residual magnetic energy on the secondary side of the ignition coil. Considering this point, as in claim 9 , the start timing of the spike noise detection section is set to the later of the predetermined crank angle after the elapse of the predetermined time and the top dead center after the ignition timing. It is good to make it. In this way, it is possible to prevent the LC resonance noise waveform generated by the residual magnetic energy on the secondary side of the ignition coil immediately after the ignition timing (immediately after the end of discharge) from being erroneously determined as spike noise. Spike noise detection accuracy can be improved.

In general, the width of spike noise is determined from the secondary inductance and secondary stray capacitance of the ignition coil. In consideration of such characteristics, the A / D conversion cycle of the ion current detection value for detecting spike noise is set to the A / D of the ion current detection value for detecting the combustion state such as misfire as in claim 10. The same period as the conversion period may be set, and the A / D conversion period may be set to ¼ or less of the width of the spike noise determined from the secondary inductance and secondary stray capacitance of the ignition coil. In this way, the circuit configuration and the A / D conversion process are performed by sharing the A / D conversion of the ion current detection value for detecting spike noise and the A / D conversion of the ion current detection value for detecting the combustion state. Thus, the spike noise detection accuracy can be ensured while satisfying the demand for cost reduction and processing load reduction.

Further, as described in claim 11 , the ion current detection gain may be set so that the ion current detection range by the ion current detection means is limited to 5 to 50 μA. In this way, it is possible to increase the detection sensitivity of combustion ions while ensuring the detection sensitivity of spike noise necessary for distinguishing and detecting generally occurring spike noise of 5 to 20 μA from other noises. .

  In addition, when a circuit constituting the ionic current detecting means fails, there is a failure mode in which the circuit oscillates and the oscillation waveform is erroneously detected as spike noise. The number of occurrences tends to be significantly larger than the actual number of spike noise occurrences.

In consideration of such characteristics, a first determination threshold value for detecting a spike noise abnormal cycle is set as in claim 12 and a second for detecting a failure of the ion current detection means. Is set to a value larger than the first determination threshold, and the number of occurrences of spike noise counted by the spike noise counting means is greater than or equal to the first determination threshold and the second It may be determined that the spike noise abnormality cycle is less than or equal to a determination threshold value, and that the ion current detection unit is in failure when the second determination threshold value is exceeded. In this way, the spike noise abnormal cycle and the failure of the ionic current detection means can be distinguished and detected.

  Several embodiments embodying the best mode for carrying out the present invention will be described below.

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 signal is input to the engine control circuit 34. The ion current detection circuit 35 (ion current detection means) 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 An ion current detection device is configured.

  The ion current detection apparatus according to the first embodiment has a specification in which an ignition plug for detecting an ion current with a spike noise countermeasure (corona discharge countermeasure) is used as the ignition plug 27. Ion current detection ignition plugs with countermeasures against spike noise are described in, for example, JP-A-10-89221, JP-A-2005-129398, JP-A-2005-129399, and JP-A-11-219772. A spark plug having a function for suppressing the occurrence of spike noise may be used.

  The engine control circuit 34 performs A / D conversion of the ion current signal from the ion current detection circuit 35 at a predetermined sampling period to the engine control microcomputer 41 that executes various engine control programs. An ion current signal processing circuit 42 for capturing, and a sensor signal processing circuit for processing various sensor signals for detecting the engine operating state such as the crank angle sensor 43 and the cam angle sensor 44 and capturing them in the engine control microcomputer 41 45 etc. are provided. The ion current signal processing circuit 42 may use a microcomputer with an A / D conversion function, or may be composed of a signal processing IC with an A / D conversion function.

  During engine operation, the power transistor 25 is turned on / off at the rise / fall of the ignition signal transmitted from the engine control microcomputer 41 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 ion current detection resistor 31, and the ion current signal of the voltage V corresponding to the ionic current is ionized from the output terminal of the inverting amplifier circuit 33 A / D conversion is performed by the current signal processing circuit 42 and is taken into the engine control microcomputer 41.

  The engine control microcomputer 41 performs fuel injection control and ignition timing control according to the engine operating state detected by the crank angle sensor 43, the cam angle sensor 44, the intake air amount sensor (not shown), etc., and also detects the ionic current. Using the ion current signal output from the circuit 35, the peak value, integral value, ion output time TMF, etc. of the ion current in a predetermined combustion ion detection section are detected, and the combustion state (misfire, preignition, knocking, combustion) A fluctuation state).

  As described above, the ion current detection device according to the first embodiment is designed to use the ion current detection spark plug 27 with spike noise countermeasures. However, when replacing the spark plug 27 on the user side, There is a possibility that different types of spark plugs (general-purpose spark plugs) that do not deal with spike noise will be mounted. If a different type of spark plug that does not deal with spike noise is installed, the effect of neutralizing the electrification charge in the event of a misfire will not be obtained, so the electrification of the spark plug will occur when the in-cylinder pressure in the second half of the combustion stroke decreases due to a misfire. There is a characteristic that spike noise is likely to occur frequently due to electric charges.

  Here, with reference to FIG. 2, an ion current detection waveform when the ion current detection ignition plug 27 with spike noise countermeasures is mounted and an ion current detection waveform when the different types of spark plugs without spike noise countermeasures are mounted will be described.

  In any spark plug, a pulse-like noise current having a short time width is induced 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). Immediately after the ignition signal is switched from ON to OFF, LC resonance noise is generated by the residual magnetic energy on the secondary side of the ignition coil 21, and then the current waveform of ions (combustion ions) generated by combustion is detected during normal combustion. However, since no combustion ions are generated during a misfire, the current waveform of the combustion ions is not detected.

  In the ion current detection ignition plug 27 with countermeasures against spike noise, the generation of spike noise due to the insulator charge is suppressed, so that the ion current waveform due to spike noise is not detected during a misfire as shown in FIG. In the case of different types of spark plugs that do not deal with spike noise, the effect of neutralizing the insulator charge is not obtained in the event of a misfire, and as a result, as shown in FIG. Spike noise tends to occur frequently due to the insulator charge of the spark plug at the time.

  In conventional ion current detectors, even when a different type of spark plug that does not take measures against spike noise is installed, the installation of the different type of spark plug cannot be detected. There is a possibility that it is erroneously determined as an ion, and there is a possibility that it is erroneously determined as combustion even though a misfire is occurring.

  As a countermeasure against this, the engine control microcomputer 41 detects the ion current detection circuit 35 within a predetermined spike noise detection section including a combustion stroke for each cylinder by executing a program shown in FIGS. Analyzes the ion current change pattern and counts the number of occurrences of spike noise-like sudden current changes (hereinafter simply referred to as “spike noise”), and the number of spike noise occurrences within the spike noise detection interval of each cylinder is a predetermined value. Whether or not it is a spike noise abnormal cycle is determined for each cylinder based on whether or not it is above, and the number of ignitions and the number of occurrences of the spike noise abnormal cycle are counted for each cylinder to calculate the spike noise abnormal cycle. Determine the frequency of occurrence (number of spike noise abnormal cycles per predetermined number of ignitions) Heterologous spark plug of spike noise without countermeasures cylinder occurrence frequency of the cycle is equal to or greater than the determination threshold value is to be determined loaded cylinders or spark plug faults cylinder.

Here, a method for determining whether or not the different type spark plug with no countermeasure against spike noise according to the first embodiment is mounted will be described in detail.
Generally, the spike noise width to is calculated by the equation (1) shown in FIG. 3 by the secondary inductance L2 and secondary stray capacitance C2 of the ignition coil 21 and is, for example, 100 to 150 .mu.s. Further, the spike noise peak current ip is calculated by the equation (2) shown in FIG. 3 based on the insulator charging capacity ΔC and the charging voltage Vt of the spark plug, and becomes, for example, 5 to 20 μA.

  In a system in which the detection gain of the ion current is set so that the saturation of the ion current signal is generated, the detection range of the ion current is set to 5 to 50 μA in consideration that the peak current ip of the spike noise is generally 5 to 20 μA. It is preferable to set the detection gain of the ion current so as to limit to In this way, it is possible to increase the detection sensitivity of combustion ions while ensuring the detection sensitivity of spike noise necessary for distinguishing and detecting generally occurring spike noise of 5 to 20 μA from other noises. .

  In addition, in order to detect a spike noise-like rapid current change by analyzing the ion current change pattern, the A / D conversion cycle (sampling cycle) of the ion current signal output from the ion current detection circuit 35 is set to spike noise. What is necessary is just to set to 1/4 or less of width to. From this viewpoint, in this embodiment, the A / D conversion period of the ion current signal is set to 16 μs, for example. Furthermore, the A / D conversion period of the ion current signal for detecting spike noise is set to the same period as the A / D conversion period of the ion current signal for detecting the combustion state such as misfire. Thereby, the A / D conversion of the ion current signal for detecting spike noise and the A / D conversion of the ion current signal for detecting the combustion state are made common, and the configuration and A / D conversion of the ion current signal processing circuit 42 are performed. Processing can be simplified, and spike noise detection accuracy can be ensured while satisfying demands for cost reduction and processing load reduction.

  As shown in FIG. 4, within the spike noise detection section, the ion current change pattern is analyzed from the ion current detection value captured at a predetermined A / D conversion period (for example, 16 μs), and the peak of the ion current change pattern is analyzed. Detect points and bottom points. At this time, each time an ion current detection value is taken in (each time an ion current signal is A / D converted), the previous detection value (peak hold value or bottom hold value) of the ion current is compared with the current detection value to determine the ion It is determined whether the current detection value is changing in the upward or downward direction. When the ion current detection value is changing in the upward direction, the current ion detection value is used as a new peak point to hold the peak. When the ion current detection value changes in the downward direction, the current ion current detection value is bottom-held as a new bottom point.

  At this time, if it is determined that the ion current detection value saturates and hardly changes because the change width between the previous detection value (peak hold value or bottom hold value) of the ion current and the current detection value is small, the saturating is performed. In the section, the determination result of the ion current change direction is maintained in the state immediately before the saturating section. In this way, it is possible to prevent the current change from the saturating state of the ion current detection value from being erroneously determined as spike noise.

  In the first embodiment, it is determined that spike noise has occurred when a current change equal to or greater than a predetermined value occurs within a predetermined time. Specifically, the spike noise is determined by whether or not the increase / decrease amount of the detected ion current value within a predetermined time ΔT (for example, 50 to 100 μs) from the peak / bottom point exceeds the spike noise determination value (for example, 5 μA). The spike noise counter is determined to be spike noise every time the rise / fall of the ion current detection value within a predetermined time ΔT from the peak / bottom point exceeds the spike noise judgment value. Is counted up to count the number of occurrences of spike noise within the spike noise detection interval.

  Then, it is determined whether or not there is a spike noise abnormal cycle for each cylinder based on whether or not the number of occurrences of spike noise in the spike noise detection section of each cylinder is a predetermined value or more, and the number of ignitions for each cylinder. The occurrence frequency of the spike noise abnormal cycle is counted to determine the occurrence frequency of the spike noise abnormal cycle (the number of occurrences of the spike noise abnormal cycle per predetermined number of ignitions), and the occurrence frequency of the spike noise abnormal cycle is determined. Cylinders with a threshold value or higher are determined as cylinders equipped with different types of spark plugs that have not taken countermeasures against spike noise.

  By the way, when the ion current detection circuit 35 fails due to a short circuit or the like, there is a failure mode in which the ion current detection circuit 35 oscillates and the oscillation waveform is erroneously detected as spike noise. The number of occurrences of spike noise tends to be significantly larger than the actual number of occurrences of spike noise.

  In consideration of such characteristics, in the first embodiment, a first determination threshold value for detecting a spike noise abnormal cycle is set, and a second value for detecting a failure of the ion current detection circuit 35 is set. Is set to a value larger than the first determination threshold, and the number of occurrences of spike noise counted by the spike noise counter is equal to or greater than the first determination threshold, and the second determination is performed. When it is below the threshold value, it is determined that the spike noise is abnormal, and when the second determination threshold value is exceeded, it is determined that the ion current detection circuit 35 has failed. In this way, the spike noise abnormal cycle and the failure of the ion current detection circuit 35 can be distinguished and detected.

  In general, a heterogeneous spark plug that does not take countermeasures against spike noise cannot obtain an effect of neutralizing the insulator charge in the event of a misfire, and therefore has a characteristic that spike noise tends to occur frequently due to the insulator charge of the spark plug in the event of a misfire. Due to such characteristics, in the case of different types of spark plugs that have not taken countermeasures against spike noise, if spike noise occurs frequently, there is a high possibility of misfire.

  From such a viewpoint, in the first embodiment, when a spike noise abnormal cycle is detected, the spike noise abnormal cycle is determined as a misfire cycle. In this way, it is possible to detect misfire even when a different type of spark plug that does not deal with spike noise is mounted.

  In this case, in consideration of the characteristic that the ion current output time TMF at the time of misfire is shorter than that at the time of ignition even when a different type spark plug that does not take measures against spike noise is installed, in the first embodiment, the spike noise detection section of each cylinder is taken into consideration. It is determined whether each of the cylinders has a spike noise abnormal cycle or a misfire cycle depending on whether or not the number of occurrences of spike noise is not less than a predetermined value and the ion current output time TMF is not more than a predetermined time. ing. In this way, it is possible to improve the misfire detection accuracy when a different type of spark plug with no spike noise countermeasure is attached.

  Further, as shown in FIG. 2, an LC resonance noise waveform is generated by the residual magnetic energy on the secondary side of the ignition coil 21 immediately after the ignition timing (immediately after the end of discharge). In consideration of this point, in this embodiment, the start timing of the spike noise detection interval is set to a predetermined crank angle (for example, ATDC 30 ° C. A) after a predetermined time (for example, after 2 ms) from the ignition timing and after the top dead center. I'm trying to set one of them later. In this way, it is possible to prevent the LC resonance noise waveform generated by the residual magnetic energy on the secondary side of the ignition coil 21 from being erroneously determined as spike noise immediately after the ignition timing (immediately after the end of discharge). , Spike noise detection accuracy can be improved.

  The heterogeneous spark plug detection process according to the first embodiment described above is executed by the engine control microcomputer 41 and the ion current signal processing circuit 42 according to the programs shown in FIGS. Hereinafter, the processing contents of these programs will be described.

[Ion current signal processing]
The ion current signal processing program of FIG. 5 is repeatedly executed by the ion current signal processing circuit 42 in the A / D conversion cycle of the ion current signal. When this program is started, first, in step 101, the crank angle signal output from the sensor signal processing circuit 45 is read and the ignition signal, misfire detection interval and spike noise detection interval output from the engine control microcomputer 41 are read. Read the indicated value.

  Thereafter, the process proceeds to step 102 where the ion current signal output from the ion current detection circuit 35 is A / D converted and captured, and in the next step 103, it is determined whether or not it is within the misfire detection section, and misfire detection is performed. If it is within the section, the process proceeds to step 104, a process of detecting the ion current peak value used in the misfire determination process, the ion current output time TMF (see FIG. 2), and the like is executed, and the process proceeds to step 105. If it is determined in step 103 that it is not within the misfire detection section, the process proceeds to step 105 without performing the process of step 104.

  In step 105, a spike noise count processing program shown in FIGS. 6 to 8 to be described later is executed, and the number of occurrences of spike noise in the spike noise detection section is counted by the spike noise counter CSPN. Each data such as the count value of the noise counter CSPN, the ion current peak value, and the ion current output time TMF is transmitted to the engine control microcomputer 41.

[Spike noise count processing]
The spike noise count processing program shown in FIGS. 6 to 8 is a subroutine executed in step 106 of the ion current signal processing program shown in FIG. 5, and plays a role as spike noise count means in the claims. This program is executed by the ion current signal processing circuit 42, but may be executed by the engine control microcomputer 41. This program is executed for each cylinder, and the number of occurrences of spike noise in the spike noise detection section is counted by the spike noise counter CSPN for each cylinder.

  When this program is started, first, in step 201, an ion current detection value obtained by A / D converting the ion current signal is read. Then, in the next steps 202 to 204, it is determined whether or not it is within the spike noise detection interval based on whether or not all the following three conditions (1) to (3) are satisfied.

(1) After a predetermined time has elapsed from the ignition timing (for example, after 2 ms) << Step 202 >>
(2) After a predetermined crank angle after top dead center (for example, after ATDC 30 ° C. A) << Step 203 >>
(3) Before spike noise detection section end set value (for example, ATDC 120 ° C. A) << Step 204 >>

  Here, the above conditions (1) and (2) are conditions for determining whether or not it is after the start timing of the spike noise detection section, and the start timing of the spike noise detection section is a predetermined time from the ignition timing. It is set to the later one of a predetermined crank angle (for example, ATDC 30 ° C. A) after elapse (for example, after 2 ms has elapsed) and after top dead center. Thereby, it is possible to prevent an LC resonance noise waveform generated by residual magnetic energy on the secondary side of the ignition coil 21 immediately after the ignition timing (immediately after the end of discharge) from being erroneously determined as spike noise. In the first embodiment, the start timing of the spike noise detection section is set to a timing slightly later than the start timing of the misfire detection section, and the end timing of the spike noise detection section is set to be the same as the end timing of the misfire detection section. However, this setting is not necessarily required.

  When there is a condition that does not satisfy any one of the above three conditions (1) to (3) (when “No” is determined in any of steps 202 to 204), the process proceeds to step 206 Then, it is determined that it is outside the spike noise detection section, and this program is terminated without performing the subsequent processing.

  On the other hand, when all of the above three conditions (1) to (3) are satisfied (when it is determined as “Yes” in steps 202 to 204), the process proceeds to step 205, and within the spike noise detection interval. The process proceeds to step 207, where it is determined whether or not the number of times of A / D conversion of the ion current signal in the spike noise detection section (the number of times of reading of the ion current detection value) is the second or later. As a result, if it is determined that the first A / D conversion is performed, the process proceeds to step 208, where initialization processing is executed, the count value of the spike noise counter CSPN is reset to the initial value “0”, and the ionic current change is also performed. The direction determination flag XUD is set to “1” which means the upward direction, the current ion current detection value is stored as storage data of the previous ion current detection value, and this program is terminated.

  On the other hand, if it is determined in step 207 that the number of A / D conversions of the ion current signal in the spike noise detection section is the second or later, the process proceeds to step 209, and the ion current change direction determination flag XUD is set in the upward direction. It is determined whether or not it is set to “1”. As a result, if it is determined that the ion current change direction determination flag XUD = 1 (upward direction), the process proceeds to step 210 to determine whether or not the current ion current detection value is greater than the previous peak hold value VP. If the current ion current detection value is larger than the previous peak hold value VP, the process proceeds to step 211, where the current ion current detection value is updated and stored as a new peak hold value VP, and the current A / D conversion timing is set. It is updated and stored as a new peak timing TP.

  If it is determined in step 209 that the ion current change direction determination flag XUD = 0 (downward direction), the process proceeds to step 212, and whether or not the current ion current detection value is smaller than the previous bottom hold value VB. If the current ion current detection value is smaller than the previous bottom hold value VB, the process proceeds to step 213, and the current ion current detection value is updated and stored as a new bottom hold value VB. The D conversion timing is updated and stored as a new bottom timing TB.

  Thereafter, the process proceeds to step 214 in FIG. 7, where it is determined whether or not the ion current change direction determination flag XUD is set to “1” meaning the upward direction, and the ion current change direction determination flag XUD = 1 (the upward direction) If the difference between the peak hold value VP (peak point) and the current ion current detection value is larger than a predetermined value C1 (for example, 2 μA), the change in the ion current detection value is determined. It is determined whether the direction is reversed from the peak point to the descending direction.

  As a result, if it is determined that the difference between the peak hold value VP and the current ion current detection value is larger than the predetermined value C1, it is determined that the change direction of the ion current detection value is reversed from the peak point to the downward direction. In step 216, the ion current change direction determination flag XUD is set to “0” indicating the downward direction, and in the next step 217, the gradient count history flag is reset to “0” indicating no gradient count history. .

  On the other hand, if it is determined in step 215 that the difference between the peak hold value VP and the current ion current detection value is equal to or less than the predetermined value C1, the change direction of the ion current detection value is determined to be the upward direction or the saturating state, Proceeding to step 218, the ion current change direction determination flag XUD is maintained at “1” which means the upward direction.

  If it is determined in step 214 that the ion current change direction determination flag XUD = 0 (downward direction), the process proceeds to step 219, where the difference between the current ion current detection value and the bottom hold value VB (bottom point) is determined. Is greater than a predetermined value C1 (for example, 2 μA), it is determined whether or not the direction of change in the detected ion current value is reversed from the bottom point to the upward direction.

  As a result, if it is determined that the difference between the current ion current detection value and the bottom hold value VB is greater than the predetermined value C1, it is determined that the direction of change in the ion current detection value is reversed from the bottom point to the upward direction. In step 220, the ion current change direction determination flag XUD is set to “1” which means the upward direction, and in the next step 221, the gradient count history flag is reset to “0” which means that there is no gradient count history. .

  On the other hand, if it is determined in step 219 that the difference between the current ion current detection value and the bottom hold value VB is equal to or less than the predetermined value C1, the change direction of the ion current detection value is determined to be a downward direction or a saturating state, Proceeding to step 222, the ion current change direction determination flag XUD is maintained at "0" meaning the downward direction.

  With the above processing, in the saturating section where the change in the detected ion current value is in the saturating state (within ± 2 μA), the ionic current changing direction determination flag XUD (the ionic current changing direction determination result) is maintained in the state immediately before the saturating section. Is done.

  Thereafter, the process proceeds to step 223 in FIG. 8 to determine whether or not the ion current change direction determination flag XUD is set to “1” meaning the upward direction, and the ion current change direction determination flag XUD = 1 (the upward direction) ), The process proceeds to step 224, and the ion current increase ΔVn from the bottom hold value VB (bottom point) to the current ion current detection value is calculated, and from the bottom timing TB to the current A / D conversion timing. The elapsed time ΔTn is calculated.

  Thereafter, in steps 225 to 227, it is determined as follows whether or not the current rising slope of the ion current detection value is spike noise. First, in step 225, it is determined whether or not the elapsed time ΔTn from the bottom timing TB is within a predetermined time CTH (eg, within 96 μs). If this elapsed time ΔTn is within the predetermined time CTH, the process proceeds to step 226. Then, it is determined whether or not the gradient count history flag is “0” meaning no gradient count history. Here, “no gradient count history” means that the rising slope of the ion current detection value from the bottom timing TB is not determined as spike noise, and the spike noise counter CSPN has not yet been counted up.

  If the gradient count history flag = 0 (no gradient count history), the process proceeds to step 227, and the current increase amount ΔVn from the bottom hold value VB to the current ion current detection value is equal to or greater than a predetermined value CVH (for example, 5 μA or greater). It is determined whether or not. If “Yes” is determined in all of these steps 225 to 227, it is determined that the noise is spike noise, the process proceeds to step 228, the spike noise counter CSPN is counted up, and the gradient count history flag indicates that the gradient count history is present. Set to “1” and proceed to step 234.

As a result of the above processing, if the elapsed time ΔTn from the bottom timing TB is within the predetermined time CTH and the ion current increase ΔVn from the bottom hold value VB is greater than or equal to the predetermined value CVH, it is determined as spike noise and the spike noise counter CSPN. Is counted up only once.
If it is determined as “No” in any of the above steps 225 to 227, it is determined that there is no spike noise or there is a gradient count history, and the process proceeds to step 234.

  On the other hand, if it is determined in step 223 that the ion current change direction determination flag XUD = 0 (downward direction), the process proceeds to step 229, and ions from the peak hold value VP (peak point) to the current ion current detection value are processed. A current drop amount ΔVn is calculated, and an elapsed time ΔTn from the peak timing TP to the current A / D conversion timing is calculated.

  Thereafter, in steps 230 to 232, it is determined as follows whether or not the current descending slope of the detected ion current value is spike noise. First, in step 230, it is determined whether or not the elapsed time ΔTn from the peak timing TP is within a predetermined time CTH (for example, within 96 μs). If the elapsed time ΔTn is within the predetermined time CTH, the process proceeds to step 231. Then, it is determined whether or not the gradient count history flag is “0” meaning no gradient count history. Here, “no gradient count history” means that the falling slope of the ion current detection value from the peak timing TP is not determined as spike noise, and the spike noise counter CSPN has not yet been counted up.

  If the gradient count history flag = 0 (no gradient count history), the process proceeds to step 232, and the current increase amount ΔVn from the bottom hold value VB to the current ion current detection value is equal to or greater than a predetermined value CVH (for example, 5 μA or greater). It is determined whether or not. If “Yes” is determined in all of these steps 230 to 232, it is determined that the noise is spike noise, the process proceeds to step 233, the spike noise counter CSPN is counted up, and the gradient count history flag indicates that there is a gradient count history. Set to “1” and proceed to step 234.

With the above processing, if the elapsed time ΔTn from the peak timing TP is within the predetermined time CTH and the ion current drop amount ΔVn from the peak hold value VP is equal to or greater than the predetermined value CVH, it is determined that the noise is spike noise and the spike noise counter CSPN. Is counted up only once.
If “No” is determined in any of the above steps 230 to 232, it is determined that there is no spike noise or that there is a gradient count history, and the process proceeds to step 234.

  In this step 234, it is determined whether or not the spike noise detection section ends (for example, after ATDC 120 ° C. A), and if it is determined that it is within the spike noise detection section, this program is ended as it is, and the spike noise detection section ends. If it is determined, the process proceeds to step 235, and the count value of the spike noise counter CSPN at the end of the spike noise detection section is updated and stored in the memory of the engine control microcomputer 41. The count value of the spike noise counter CSPN at the end of the spike noise detection section is used as information for evaluating the number of occurrences of spike noise in the spike noise detection section.

[Abnormal diagnosis]
The abnormality diagnosis program shown in FIGS. 9 and 10 is executed by the engine control microcomputer 41 at a predetermined cycle, and serves as spike noise abnormality cycle determination means and spark plug abnormality detection means in the claims. This program is executed for each cylinder, and an abnormality diagnosis described later is executed for each cylinder.

  When this program is started, first, in step 301, it is determined whether or not the count value data of the spike noise counter CSPN at the end of the spike noise detection section has been updated. If not, the subsequent processing is performed. Quit this program without

  On the other hand, if it is determined in step 301 that the count value data of the spike noise counter CSPN at the end of the spike noise detection section has been updated, the process proceeds to step 302, and the processing of the abnormality diagnosis execution condition determination program in FIG. Based on the result, it is determined whether the abnormality diagnosis execution condition is satisfied. If the abnormality diagnosis execution condition is not satisfied, the program is terminated without performing the subsequent processing, and the abnormality diagnosis execution condition is satisfied. If so, the process proceeds to step 303 to count the number of updates of the count value of the spike noise counter CSPN and count the number of ignitions.

  Thereafter, the process proceeds to step 304, where it is determined whether or not the count value of the spike noise counter CSPN is larger than the first determination threshold value VCH1 for detecting the spike noise abnormal cycle, and the count value of the spike noise counter CSPN is determined. Is equal to or less than the first determination threshold value VCH1, it is determined that the cycle is not a spike noise abnormal cycle, and the process proceeds to step 310 to be described later.

  On the other hand, if it is determined in step 304 that the count value of the spike noise counter CSPN is larger than the first determination threshold value VCH1, the process proceeds to step 305, where the count value of the spike noise counter CSPN is changed to the ionic current. It is determined whether or not it is larger than a second determination threshold value VCH2 for detecting a failure (oscillation abnormality) of the detection circuit 35. Here, the second determination threshold value VCH2 is set to a value larger than the first determination threshold value VCH1.

  If it is determined in step 305 that the count value of the spike noise counter CSPN is larger than the second determination threshold value VCH2, the process proceeds to step 306, where an oscillation abnormality cycle (hereinafter, “circuit oscillation abnormality”) of the ion current detection circuit 35 is performed. The circuit oscillation abnormality cycle counter NHSN that counts the number of occurrences of the circuit oscillation abnormality cycle is counted up, and the process proceeds to Step 310 described later.

  If “Yes” is determined in Step 304 and “No” is determined in Step 305, that is, if VCH1 ≦ CSPN <VCH2, the process proceeds to Step 307, and the ion current output time TMF (FIG. 2) is smaller than the predetermined time VCT1, and if the ion current output time TMF is equal to or longer than the predetermined time VCT1, the combustion ion fluctuation cycle at the time of ignition (the fluctuation of the combustion ions is erroneously determined as spike noise). Cycle), and the process proceeds to step 310 to be described later.

  On the other hand, the process proceeds to step 307, and if it is determined that the ion current output time TMF (see FIG. 2) is shorter than the predetermined time VCT1, the process proceeds to step 308, where it is determined that there is a spike noise abnormal cycle, and spike noise. A spike noise abnormal cycle counter NSPN that counts the number of occurrences of abnormal cycles is counted up, and in the next step 309, it is determined as a misfire cycle.

  Thereafter, the process proceeds to step 310, where it is determined whether or not the number of ignitions exceeds a predetermined number (for example, 1000 times). If the number of ignitions is equal to or less than the predetermined number, this program is terminated and the number of ignitions reaches the predetermined number. If exceeded, the process proceeds to step 311 to divide the number of occurrences of spike noise abnormal cycles NSPN by the predetermined number of ignitions (1000 times) to calculate the frequency of occurrence of spike noise abnormal cycles and to generate circuit oscillation abnormal cycles. The frequency of occurrence of an abnormal circuit oscillation cycle is calculated by dividing the number of times NHSN by the predetermined number of ignition times (1000 times).

  Thereafter, the process proceeds to step 312 in FIG. 10 to determine whether or not the occurrence frequency of the spike noise abnormal cycle is larger than the determination threshold value K1, and the occurrence frequency of the spike noise abnormal cycle is larger than the determination threshold value K1. For example, the process proceeds to step 313, where it is determined that a different type of spark plug that does not deal with spike noise is attached. If the occurrence frequency of the spike noise abnormal cycle is equal to or less than the determination threshold value K1, it is not determined that the different type of spark plug is mounted.

Thereafter, the process proceeds to step 314, where it is determined whether or not the occurrence frequency of the circuit oscillation abnormality cycle is larger than the determination threshold value K2. If the occurrence frequency of the circuit oscillation abnormality cycle is larger than the determination threshold value K2, Proceeding to 315, it is determined that a circuit oscillation failure has occurred. If the occurrence frequency of the circuit oscillation abnormality cycle is equal to or less than the determination threshold value K2, it is not determined that the circuit oscillation is faulty.
After performing the abnormality diagnosis as described above, the process proceeds to step 316, the number of ignitions is reset, and this program is terminated.

[Error diagnosis execution condition judgment]
The abnormality diagnosis execution condition determination program of FIG. 11 is executed by the engine control microcomputer 41 at a predetermined cycle, and determines whether or not the abnormality diagnosis execution condition is not established as follows. When this program is started, first, in step 401, it is determined whether or not the battery voltage that is the power supply voltage of the ignition system is higher than the predetermined voltage CBH. If the battery voltage is equal to or lower than the predetermined voltage CBH, step 408 is performed. Then, it is determined that the abnormality diagnosis execution condition is not satisfied, and this program is terminated. This is because when the battery voltage is lowered, the influence of voltage fluctuation of an alternator (not shown) appears relatively large, and noise generated by the voltage fluctuation of the alternator may be erroneously determined as spike noise.

  If it is determined in step 401 that the battery voltage is higher than the predetermined voltage CBH, the process proceeds to step 402, in which it is determined whether or not the battery voltage fluctuation amount is smaller than the predetermined value CDBH, and the battery voltage fluctuation amount is a predetermined value. If it is equal to or higher than CDBH, it is determined that the battery is overloaded and the noise generated by the voltage variation of the alternator may be erroneously determined as spike noise. The process proceeds to step 408, and the abnormality diagnosis execution condition is It is determined that it has not been established, and the program is terminated.

  If it is determined in step 402 that the battery voltage fluctuation amount is smaller than the predetermined value CDBH, the process proceeds to step 403 to determine whether or not the ignition system component is determined not to be in a failure state by another abnormality diagnosis function. It is determined whether or not the system component failure flag = 0, and if the ignition system component failure flag = 1 (ignition system component failure state), the circuit state is such that spike noise cannot be normally detected. Then, it is determined that the abnormality diagnosis execution condition is not satisfied, and this program is terminated.

  If it is determined in step 403 that the ignition system component failure flag = 0 (not an ignition system component failure state), the process proceeds to step 404, and whether or not the ignition timing is advanced from a predetermined value (for example, TDC). If the ignition timing is retarded from a predetermined value (for example, TDC), the routine proceeds to step 408, where it is determined that the abnormality diagnosis execution condition is not satisfied, and this program is terminated. This is because when the ignition timing is retarded, the combustion state becomes slow, and spike noise may be erroneously detected due to fluctuations in combustion ions.

  If it is determined in step 404 that the ignition timing is advanced from a predetermined value (for example, TDC), the routine proceeds to step 405, where it is determined whether the air-fuel ratio lean control flag = 0 (not under air-fuel ratio lean control). If the air-fuel ratio lean control flag = 1 (air-fuel ratio lean control is in progress), the routine proceeds to step 408, where it is determined that the abnormality diagnosis execution condition is not satisfied and the program is terminated. This is because during the air-fuel ratio lean control, the combustion state becomes slow and spike noise may be erroneously detected.

If it is determined in step 405 that the air-fuel ratio lean control flag = 0 (the air-fuel ratio lean control is not in progress), the routine proceeds to step 406, where it is determined whether or not the combustion state is within the abnormality diagnosis permission operation region in which the combustion state does not become slow. If it is not within the abnormality diagnosis permission operation region, the process proceeds to step 408, where it is determined that the abnormality diagnosis execution condition is not satisfied, and this program is terminated.
On the other hand, if it is determined as “Yes” in steps 401 to 406, the process proceeds to step 407, where it is determined that the abnormality diagnosis execution condition is satisfied, and this program is terminated.

  According to the first embodiment described above, paying attention to the fact that spike noise tends to occur frequently due to the insulator charging charge of the different type spark plug when misfire occurs when the different type spark plug that does not cope with spike noise is attached. Cylinders with frequent spike noise can be determined as cylinders with different types of spark plugs that do not take measures against spike noise. This makes it possible to misidentify spike noise as combustion ions when different types of spark plugs without spike noise are installed. This can be prevented in advance.

  In the second embodiment of the present invention shown in FIGS. 12 and 13, after the spike noise detection section including the combustion stroke, a background noise detection section not including the combustion stroke is set, and the spike noise detection section and the background are set. Counts the number of spike noise occurrences in each noise detection interval, and subtracts and corrects the spike noise occurrence count in the spike noise detection interval counted for each cylinder by the number of spike noise occurrences in the background noise detection interval. The number of spike noise occurrences is obtained, and whether or not the spike noise abnormality cycle is determined for each cylinder is determined based on whether or not the effective spike noise occurrence number is equal to or greater than a predetermined value.

  In general, spike noise is likely to occur in the spike noise detection section that includes the combustion stroke, and spike noise is less likely to occur in the background noise detection section that does not include the combustion stroke, so it is detected as spike noise in the background noise detection section. The number of generated background noises is detected. Therefore, if the number of spike noise occurrences in the spike noise detection section is subtracted and corrected by the number of spike noise (background noise) occurrences in the background noise detection section, the net noise excluding background noise generated in the spike noise detection section is excluded. The number of occurrences of spike noise (the number of occurrences of effective spike noise) can be detected.

  The determination of the spike noise abnormal cycle of the second embodiment described above is performed by the ion current signal processing circuit 42 (or the engine control microcomputer 41) according to the spike noise abnormal cycle determination program of FIG. Is executed. This program is executed for each cylinder, and a spike noise abnormal cycle is detected for each cylinder.

  When this program is started, first, in step 501, it is determined whether or not it is within a spike noise detection section including a combustion stroke. This spike noise detection section may be set by the same method as in the first embodiment, or a certain spike noise detection section may be set in advance.

  If it is determined in step 501 that it is within the spike noise detection section, the process proceeds to step 502, and the number of spike noise occurrences CSPN1 in the spike noise detection section is counted in the same manner as in the first embodiment. If it is not within the spike noise detection period, the spike noise occurrence count CSPN1 is not counted.

  Thereafter, the process proceeds to step 503, and it is determined whether or not it is within the background noise detection section not including the combustion stroke. For example, the background noise detection section may be set in the section from ATDC 180 ° C. to ATDC 360 ° C., and may be set in other sections.

  If it is determined in step 503 that it is within the background noise detection interval, the process proceeds to step 504, and spike noise (background noise) is generated in the background noise detection interval in the same manner as the spike noise detection interval. Count the number of times CSPN2. If it is not within the background noise detection interval, the spike noise occurrence count CSPN2 is not counted.

  Thereafter, the process proceeds to step 505, where it is determined whether or not the background noise detection section has ended. If the background noise detection section has not ended, the program ends without performing the subsequent processing.

After that, when the background noise detection period ends, the determination result in step 505 is “Yes”, and the process proceeds to step 506, where the spike noise occurrence count CSPN1 in the spike noise detection period is determined from the background noise detection period. The number of occurrences of spike noise (background noise) in the number CSPN2 is subtracted and corrected to determine the number of occurrences of effective spike noise.
Effective spike noise occurrence count = CSPN1-CSPN2

  Thereafter, the process proceeds to step 507, where it is determined whether the effective spike noise occurrence count is larger than a determination threshold value VHCSP1 for detecting the spike noise abnormal cycle, and the effective spike noise occurrence count is determined from the determination threshold value VHCSP1. If it is larger, it is determined as an abnormal spike noise cycle (step 508), and if the number of occurrences of effective spike noise is equal to or less than the determination threshold value VHCSP1, it is determined as a normal cycle (step 509).

  Thereafter, the process proceeds to step 510, where it is determined whether or not the background noise occurrence count CSPN2 in the background noise detection section is larger than the determination threshold value VHCSP2, and the background noise occurrence count CSPN2 is determined as the determination threshold value. If it is larger than VHCSP2, the routine proceeds to step 511, where the combustion fluctuation detection value (output time SMF of combustion ions generated by afterburning) is invalidated. This is because if the number of occurrences of background noise CSPN2 is large, the background noise may be erroneously detected as combustion ions caused by afterburning. If it is determined in step 510 that the background noise occurrence count CSPN2 is equal to or less than the determination threshold value VHCSP2, the process proceeds to step 512, and the combustion fluctuation detection value is validated.

  According to the second embodiment described above, the number of occurrences of spike noise in the spike noise detection section is subtracted and corrected by the number of occurrences of spike noise (background noise) in the background noise detection section, and is generated in the spike noise detection section. Since the number of occurrences of net spike noise to be performed (the number of occurrences of effective spike noise) is detected, it is possible to improve the accuracy of determining spike noise abnormal cycles.

Next, Embodiment 3 of the present invention will be described with reference to FIGS.
In the third embodiment, paying attention to the fact that the combustion ions change relatively greatly during the exhaust stroke when the combustion state of each cylinder becomes slow, the slow combustion state determination program of FIG. 14 and the abnormality diagnosis execution condition of FIG. By executing the determination program, the ion current detection circuit 35 detects the ion current signal for each exhaust stroke in each cylinder, and the combustion state of each cylinder becomes slow when the average value of the ion current signal is equal to or greater than a predetermined value. It is judged that the combustion is in the slow combustion state and the judgment of the spike noise abnormal cycle is prohibited, so that it is possible to prevent the spike noise abnormal cycle from being erroneously determined due to the fluctuation of the combustion ion when the slow combustion state is entered. I have to.

  Hereinafter, the processing contents of the slow combustion state determination program of FIG. 14 and the abnormality diagnosis execution condition determination program of FIG. 15 executed by the engine control circuit 34 (ion current signal processing circuit 42 or engine control microcomputer 41) in the third embodiment will be described. explain.

  The slow combustion state determination program shown in FIG. 14 is repeatedly executed by the ion current signal processing circuit 42 (or the engine control microcomputer 41) at the A / D conversion period of the ion current signal. When this program is started, first, in step 601, it is determined whether or not it is within a predetermined combustion ion fluctuation detection section. Here, the combustion ion fluctuation detection section is set to the entire section corresponding to the exhaust stroke of each cylinder (for example, the section from ATDC 180 ° C. to ATDC 360 ° C. A). Or you may set to the area equivalent to a part of exhaust stroke.

If it is determined in step 601 that it is within the combustion ion fluctuation detection section, the process proceeds to step 602, and the ion current signal Bi detected by the ion current detection circuit 35 for each cylinder (for example, ions in the combustion ion fluctuation detection section). After reading the maximum value of the current signal, the process proceeds to step 603, and the averaged value Bave of the ion current signal Bi detected for each exhaust stroke (for each combustion ion fluctuation detection section) is calculated by the following equation.
Bave = (7/8) × Bave (old) + (1/8) × Bi
Here, Bave (old) is the previous averaged value.

  Thereafter, the routine proceeds to step 604, where fluctuations in combustion ions during the exhaust stroke are relatively large depending on whether or not the smoothed average value Bave of the ion current signal Bi detected for each exhaust stroke is equal to or greater than a predetermined judgment value Cb. It is determined whether or not.

  If it is determined in step 604 that the average value Bave of the ion current signal Bi detected for each exhaust stroke is greater than or equal to the determination value Cb, it is determined that the fluctuation of combustion ions during the exhaust stroke is relatively large. Then, the process proceeds to step 605, where it is determined that the combustion is slow, and the slow combustion flag is set to “1”.

  On the other hand, if it is determined that the smoothed average value Bave of the ion current signal Bi detected for each exhaust stroke in step 604 is smaller than the determination value Cb, the process proceeds to step 606, where it is determined that the combustion state is not slow. Then, the slow combustion flag is reset to “0”.

  The abnormality diagnosis execution condition determination program shown in FIG. 15 is repeatedly executed at a predetermined cycle by the engine control microcomputer 41. In this program, as in steps 401 to 403 of FIG. 11 described in the first embodiment, it is determined in step 701 whether or not the battery voltage is higher than a predetermined voltage CBH, and in the next step 702, the battery voltage fluctuation is determined. It is determined whether or not the amount is smaller than a predetermined value CDBH, and it is determined in subsequent step 703 whether or not an ignition system component failure flag = 0 (not an ignition system component failure state), and any one of these steps 701 to 703 is performed. If it is determined as “No”, the process proceeds to step 706, where it is determined that the abnormality diagnosis execution condition is not satisfied, and this program is terminated. Thereby, the determination of the spike noise abnormal cycle is prohibited.

  On the other hand, if all of the above steps 701 to 703 are determined as “Yes”, the process proceeds to step 704, where it is determined whether or not the slow combustion state is present, depending on whether or not the slow combustion flag = 1, and the slow combustion flag is determined. If it is determined that = 1 (slow combustion state), spike noise may be erroneously detected due to fluctuations in combustion ions. Therefore, the process proceeds to step 706, where it is determined that the abnormality diagnosis execution condition is not satisfied. Exit the program. Thereby, the determination of the spike noise abnormal cycle is prohibited.

  On the other hand, if it is determined in step 704 that the slow combustion flag = 0 (not the slow combustion state), the process proceeds to step 705, where it is determined that the abnormality diagnosis execution condition is satisfied and the program is terminated. To do.

  In the third embodiment described above, when the smoothed average value Bave of the ion current signal Bi detected for each exhaust stroke is equal to or greater than the determination value Cb, it is determined that the combustion is slow and the spike noise abnormal cycle is determined. Since it is prohibited, it is possible to prevent an erroneous determination of the spike noise abnormal cycle due to the fluctuation of the combustion ions when the slow combustion state is reached. Moreover, since it is possible to determine whether or not the engine is in the slow combustion state based on the ion current signal detected for each exhaust stroke, the operating conditions (for example, the ignition timing retard amount, etc.) in which the combustion state becomes slow for each engine are determined. There is also an advantage that it is not necessary to perform complicated work such as conformance.

Next, Embodiment 4 of the present invention will be described with reference to FIG.
In the fourth embodiment, by executing the abnormality diagnosis execution condition determination program of FIG. 16, in a control state in which the combustion stability of each cylinder is reduced (for example, during ignition timing retard control, air-fuel ratio lean control, During the valve overlap increase control), when the engine operating state is in a predetermined low load region (for example, deceleration region), and when the smoldering state of the spark plug 27 is greater than or equal to a predetermined value, the spike noise abnormal cycle determination is prohibited. Thus, erroneous determination of spike noise abnormal cycles is surely prevented.

The processing contents of the abnormality diagnosis execution condition determination program of FIG. 16 executed by the engine control microcomputer 41 in the fourth embodiment will be described below.
The abnormality diagnosis execution condition determination program shown in FIG. 16 is repeatedly executed at a predetermined cycle by the engine control microcomputer 41. In this program, as in steps 401 to 403 of FIG. 11 described in the first embodiment, it is determined in step 801 whether or not the battery voltage is higher than a predetermined voltage CBH, and in the next step 802, the battery voltage fluctuation is determined. It is determined whether or not the amount is smaller than a predetermined value CDBH, and in subsequent step 803, it is determined whether or not an ignition system component failure flag = 0 (not an ignition system component failure state), and any one of these steps 801 to 803 is performed. If it is determined as “No”, the process proceeds to step 810, where it is determined that the abnormality diagnosis execution condition is not satisfied, and this program is terminated. Thereby, the determination of the spike noise abnormal cycle is prohibited.

  On the other hand, if it is determined as “Yes” in steps 801 to 803, the process proceeds to step 804, where it is determined whether or not the ignition timing is advanced from a predetermined value (for example, TDC). If the ignition timing retarding control is being retarded (for example, TDC), the combustion stability of each cylinder is reduced and the combustion becomes slow, so that spike noise can be erroneously detected due to fluctuations in combustion ions. If it is determined that the abnormality diagnosis execution condition is not satisfied, the program is terminated. Thereby, the determination of the spike noise abnormal cycle is prohibited.

  If it is determined in step 804 that the ignition timing is advanced from a predetermined value (for example, TDC), the routine proceeds to step 805, where it is determined whether the air-fuel ratio lean control flag = 0 (air-fuel ratio lean control is not in progress). If the air-fuel ratio lean control flag = 1 (during air-fuel ratio lean control), the combustion stability of each cylinder is lowered and the combustion state is slow, so spike noise is erroneously detected due to fluctuations in combustion ions. If it is determined that there is a possibility, the process proceeds to step 810, where it is determined that the abnormality diagnosis execution condition is not satisfied, and this program is terminated. Thereby, the determination of the spike noise abnormal cycle is prohibited.

  If it is determined in step 805 that the air-fuel ratio lean control flag = 0 (the air-fuel ratio lean control is not being performed), the process proceeds to step 806, where the valve timing advance amount of the intake valve is greater than a predetermined value (for example, 40 ° C. A). It is determined whether the valve timing advance amount of the intake valve is larger than a predetermined value (for example, 40 ° C. A), and it is determined whether the valve overlap increase control is being performed. If the lap increase control is being performed, the combustion stability of each cylinder is lowered and the combustion state is slow. Therefore, it is determined that spike noise may be erroneously detected due to fluctuations in combustion ions, and the process proceeds to step 810. It is determined that the abnormality diagnosis execution condition is not satisfied, and this program is terminated. Thereby, the determination of the spike noise abnormal cycle is prohibited.

  If it is determined in step 806 that the valve timing advance amount of the intake valve is equal to or less than a predetermined value (for example, 40 ° C. A), the process proceeds to step 807 to determine whether or not the engine operating state is in the deceleration region. It is determined based on whether or not the engine load is equal to or less than a predetermined value. If the engine operating state is a deceleration region, it is determined that combustion ions may become unstable and spike noise may be erroneously detected. Then, it is determined that the abnormality diagnosis execution condition is not satisfied, and this program is terminated. Thereby, the determination of the spike noise abnormal cycle is prohibited.

  If it is determined in step 807 that the engine operating state is not in the deceleration region, the process proceeds to step 808, where the smolder resistance value of the spark plug 27 (insulation resistance value between the electrodes of the spark plug 27) is a predetermined value (for example, 50 MΩ). It is determined whether or not the smoldering state of the spark plug 27 has progressed more than a predetermined value depending on whether or not the smoldering state is less than a predetermined value. If this is the case, it is determined that there is a possibility that the ion current detection accuracy is reduced and the spike noise abnormal cycle may be erroneously determined, and the process proceeds to step 810, where it is determined that the abnormality diagnosis execution condition is not satisfied and the program is terminated. To do. Thereby, the determination of the spike noise abnormal cycle is prohibited.

  On the other hand, if the smoldering resistance value of the spark plug 27 is larger than the predetermined value in step 808, the process proceeds to step 809, where it is determined that the abnormality diagnosis execution condition is satisfied, and this program is terminated.

  In the fourth embodiment described above, when the combustion stability of each cylinder is reduced (for example, during ignition timing retardation control, air-fuel ratio lean control, during valve overlap increase control), engine operation is performed. When the state is the deceleration region or when the smoldering state of the spark plug 27 is greater than or equal to a predetermined value, the spike noise abnormality cycle determination is prohibited, so that the combustion stability of each cylinder is lowered and the combustion state is slow. The spike noise abnormal cycle is caused by fluctuations in combustion ions at the time of combustion, destabilization of combustion ions when the engine operating state is in the deceleration region, and a decrease in ion current detection accuracy when the smoldering state of the spark plug 27 progresses. Can be reliably prevented from being erroneously determined.

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. In Embodiment 1 of the present invention, ignition signal, in-cylinder pressure, spike noise detection period, detection current waveform during normal combustion of a spike noise countermeasure ignition plug, detection current waveform during misfire, detection current waveform during misfire of a different type of spark plug It is a time chart explaining the relationship. It is a figure explaining the calculation method of spike noise peak value ip and noise width to. It is a time chart explaining the detection method of spike noise. It is a flowchart which shows the flow of a process of the ion current signal processing program of Example 1 of this invention. It is a flowchart which shows the flow of a process of the spike noise count processing program of Example 1 of this invention (the 1). It is a flowchart which shows the flow of a process of the spike noise count processing program of Example 1 of this invention (the 2). It is a flowchart which shows the flow of a process of the spike noise count processing program of Example 1 of this invention (the 3). It is a flowchart which shows the flow of a process of the abnormality diagnosis program of Example 1 of this invention (the 1). It is a flowchart which shows the flow of a process of the abnormality diagnosis program of Example 1 of this invention (the 2). It is a flowchart which shows the flow of a process of the abnormality diagnosis execution condition determination program of Example 1 of this invention. Ignition signal, spike noise detection period, background noise detection period, spike noise countermeasure ignition plug detection current waveform during normal combustion, detection current waveform during combustion deterioration, detection current waveform during misfire, It is a time chart explaining the relationship with the detected current waveform at the time of misfire of a different type spark plug. It is a flowchart which shows the flow of a process of the spike noise abnormal cycle determination program of Example 2 of this invention. It is a flowchart which shows the flow of a process of the slow combustion state determination program of Example 3 of this invention. It is a flowchart which shows the flow of a process of the abnormality diagnosis execution condition determination program of Example 3 of this invention. It is a flowchart which shows the flow of a process of the abnormality diagnosis execution condition determination program of Example 4 of this invention.

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, 35 ... ion current detection circuit (ion current detection means), 36 ... center electrode, 37 ... ground electrode, 41 ... microcomputer for engine control (spike noise abnormal cycle determination means, spark plug abnormality detection means), 42 ... ion Current signal processing circuit (spike noise counting means)

Claims (12)

Ion current detection means for detecting ion current generated by combustion of the air-fuel mixture in the combustion chamber of each cylinder of the internal combustion engine through the electrode of the spark plug, and as the spark plug, rapid current change (hereinafter referred to as “spike”) is provided. In an ion current detection device for an internal combustion engine that uses a spark plug corresponding to "noise"),
Spike noise counting means for analyzing the change pattern of the ion current detected by the ion current detection means within a predetermined spike noise detection section including a combustion stroke for each cylinder and counting the number of occurrences of spike noise;
Spikes for determining whether or not there is a spike noise abnormal cycle for each cylinder based on whether or not the number of spike noise occurrences within the spike noise detection interval of each cylinder counted by the spike noise counting means is greater than or equal to a predetermined value. Noise abnormal cycle determination means;
The number of ignitions and the number of occurrences of the spike noise abnormal cycle are counted for each cylinder to determine the frequency of occurrence of the spike noise abnormal cycle, and the cylinder having the spike noise abnormal cycle occurrence frequency equal to or higher than the determination threshold is spiked. A spark plug abnormality detection means for determining a cylinder with a non-noise-dissimilar spark plug or a spark plug malfunction cylinder ,
The spike noise counting means detects a peak point and / or a bottom point of a change pattern of the ion current detected by the ion current detecting means, and a current decrease rate from the peak point and / or a current increase from the bottom point. Means for determining whether the noise is spike noise based on whether the rate is equal to or greater than a predetermined value, means for detecting a saturating section in which the ion current detected by the ion current detecting means saturates and hardly changes, and An ion current detection device for an internal combustion engine , comprising: means for prohibiting the detection processing of the peak point and the bottom point in a saturating section . The spike noise counting means sets a background noise detection interval not including a combustion stroke in addition to a spike noise detection interval including the combustion stroke, and spike noise is detected in the spike noise detection interval and the background noise detection interval, respectively. Count the number of occurrences of
The spike noise abnormal cycle determination means is a value obtained by subtracting and correcting the number of spike noise occurrences in the spike noise detection section counted for each cylinder by the spike noise count means by the number of spike noise occurrences in the background noise detection section. 2. The ion current detection device for an internal combustion engine according to claim 1, wherein whether or not a spike noise abnormality cycle is determined for each of the cylinders is determined based on whether or not is equal to or greater than a predetermined value. The spike noise abnormality cycle determining means to claim 1 or 2, characterized in that it comprises means for prohibiting the determination of the spike noise abnormal cycle when operating conditions the combustion state of each cylinder of the internal combustion engine slows An ion current detection device for an internal combustion engine as described. The spike noise abnormal cycle determination means is slow that the combustion state of each cylinder of the internal combustion engine becomes slow when the average value of the ion current signal detected by the ion current detection means for each exhaust stroke in each cylinder is a predetermined value or more. The ion current detection device for an internal combustion engine according to claim 1 or 2 , further comprising means for determining that the engine is in a combustion state and prohibiting determination of the spike noise abnormal cycle. The spike noise abnormal cycle determining means is configured to control whether the combustion stability of each cylinder of the internal combustion engine is reduced, when the operating state of the internal combustion engine is in a predetermined low load region, and whether the smoldering state of the spark plug is predetermined. The ion current detection apparatus for an internal combustion engine according to claim 1 or 2 , further comprising means for prohibiting determination of the spike noise abnormal cycle in at least one of the above times. The spike noise abnormal cycle determination means includes means for prohibiting determination of the spike noise abnormal cycle when a battery for supplying a power supply voltage to the ignition system is in an overload state. The ionic current detection device for an internal combustion engine according to any one of 5 . The internal combustion engine according to any one of claims 1 to 6 , wherein the spike noise abnormal cycle determination means includes means for determining the spike noise abnormal cycle as a misfire cycle when the spike noise abnormal cycle is detected. Engine ion current detector. The spike noise abnormal cycle determination means determines whether or not the number of occurrences of spike noise in the spike noise detection section of each cylinder is equal to or greater than a predetermined value and whether the ion current output time of the ion current detection means is equal to or less than a predetermined time. 8. The ion current detection device for an internal combustion engine according to claim 7 , wherein it is determined whether or not each cylinder has a spike noise abnormal cycle and a misfire cycle. The spike noise counting means has means for setting a start timing of the spike noise detection section to a later one of a predetermined crank angle after elapse of a predetermined time and a top dead center after ignition timing. The ion current detection device for an internal combustion engine according to any one of claims 1 to 8 . The spike noise counting means sets the A / D conversion cycle of the ion current detection value for spike noise detection to the same cycle as the A / D conversion cycle of the ion current detection value for combustion state detection, and the A / D according to any one of claims 1 to 9, characterized in that it comprises means for setting the fourth or less of the width of the spike noise which is determined the conversion period and a secondary inductance and secondary stray capacitance of the ignition coil An ion current detection device for an internal combustion engine. Ion of the internal combustion engine according to any of claims 1 to 10, characterized in that detection gain of the ion current is set to limit the detection range of the ion current by the ion current detecting means 5~50μA Current detection device. The spike noise abnormal cycle determination means sets a first determination threshold value for detecting the spike noise abnormal cycle, and a second determination threshold value for detecting a failure of the ion current detection means. Is set to a value larger than the first determination threshold, and the number of occurrences of spike noise counted by the spike noise counting means is greater than or equal to the first determination threshold and the second determination threshold. wherein determining that the spike noise abnormal cycle when the value below, in any one of claims 1 to 11, wherein determining that a failure of the ion current detecting means when exceeding the second determination threshold value An ion current detection device for an internal combustion engine as described.

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