JP2008261304A - Ion current detection device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately detect a smolder state, based on an ion current detection signal. <P>SOLUTION: This device is provided with a function making smolder detection during excitation period of an ignition coil, a smolder detection during intake-compression stroke, and pre-ignition detection, prohibits or invalidates smolder detection during the excitation period of the ignition coil in a predetermined region set in a high speed-light load region, and selects a smolder detection result during the intake-compression stroke as a final judgment result of the smolder state. In a region other than the predetermined region, a smolder detection result during the excitation period of the ignition coil is selected as a final judgment result of the smolder state as it is. When both of the smolder detection result during the excitation period of the ignition coil and the smolder detection result during the intake-compression stroke indicate existence of smolder, heavy smolder is determined and pre-ignition detection is prohibited or invalidated. It is thereby prevented to determine erroneously smolder as pre-ignition. <P>COPYRIGHT: (C)2009,JPO&INPIT

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 the internal combustion engine through a spark plug.

  In recent years, focusing on the characteristics that ions are generated when the air-fuel mixture burns in the cylinder of an internal combustion engine, the ion current generated in the cylinder at each ignition is detected via the electrode of the ignition plug, and the ion current is detected. A technique for detecting the combustion state of the internal combustion engine based on the value has been developed.

  In such a combustion state detection system using ionic current, if smoldering of the spark plug (a phenomenon in which carbon generated during incomplete combustion adheres to the insulator surface around the spark plug electrode) occurs, the ionic current detection accuracy deteriorates. Therefore, since it is easy to erroneously detect the combustion state, it is necessary to accurately detect the smoldering state of the spark plug.

  As described in Patent Document 1 (Japanese Patent Application Laid-Open No. 11-13620), a conventional smolder detection method is an insulation resistance value between electrodes of a spark plug (hereinafter referred to as “smolder resistance value”) as a smoldering state progresses. Focusing on the characteristic that the leakage current increases due to a decrease in ()), the leakage current (drift current) detected by the ion current detection circuit during the intake / compression stroke (the period when combustion ions are not generated) after the combustion stroke ends On the basis of this, a smolder resistance value of the spark plug is calculated, and the presence or absence of the smolder of the spark plug is determined based on whether or not the smolder resistance value is equal to or less than a determination value.

Further, as described in Patent Document 1 and Patent Document 2 (Japanese Patent No. 2942351), when the smoldering state proceeds, the time width of the leakage current flowing in the initial period of the energization period of the ignition coil increases. Paying attention, the presence or absence of smoldering of the ignition plug is determined based on the time width of the leakage current flowing in the initial period of the energization period of the ignition coil (or the magnitude of the leakage current after the elapse of a predetermined period from the start of ignition coil energization) There is what I did.
Japanese Patent Laid-Open No. 11-13620 Japanese Patent No. 2942351

  When detecting the smoldering state based on the leakage current during the intake / compression stroke described above, as the smoldering state progresses and the smolder resistance value decreases, as shown in FIG. Since the leakage current flows, the leakage current hardly flows thereafter, and there is a problem that the smoldering state cannot be detected. In addition, in the low rotation region where the engine rotation state is unstable, the leakage current is also unstable, and the smoldering state cannot be accurately detected.

  On the other hand, when the smoldering state is detected based on the time width of the leakage current that flows in the initial stage of the energization period of the ignition coil (or the magnitude of the leakage current after the lapse of a predetermined period from the start of ignition coil energization), the smolder resistance value is large There is a problem that almost no leakage current can be detected in the region, and the smoldering state cannot be detected (see FIG. 8). In addition, in the high rotation / low load region, the leakage current varies due to the applied voltage variation during the energization period of the ignition coil, so that the smoldering state cannot be detected accurately. Furthermore, if preignition occurs in the second half of the energization period of the ignition coil, there is a possibility that leakage current due to smoldering and ion current due to preignition may overlap, which makes it difficult to distinguish between smoldering and preignition. There is also.

  The present invention has been made in view of such circumstances, and therefore, an object thereof is to provide an ion current detection device for an internal combustion engine that can accurately detect a smoldering state based on an ion current detection signal. It is in.

  In order to achieve the above object, an invention according to claim 1 is an internal combustion engine comprising ion current detection means for detecting an ion current generated by combustion of an air-fuel mixture in a combustion chamber of the internal combustion engine via a spark plug. In the ion current detecting device, the first smolder detecting means for detecting the smoldering state of the ignition plug based on the ion current detection signal during the energization period of the ignition coil, and the ion current detection signal during the intake / compression stroke Second smolder detecting means for detecting the smoldering state of the spark plug, and finally determining the smoldering state of the spark plug based on the detection results of the first and second smolder detecting means by the final judging means. This is a judgment. In this configuration, since two types of smolder detecting means for detecting a smoldering state in different smolder detection sections are provided, select a smolder detecting means with higher smolder detection accuracy according to the operating conditions of the internal combustion engine. The state can be detected, and the smoldering state can be detected with higher accuracy than in the past.

  In this case, as in claim 2, the ionic current detection signal may be corrected by the correcting means based on the smoldering state determined by the final determining means. In this way, only the net combustion ion current component obtained by removing the leakage current component (drift component) caused by smoldering from the ion current detection signal can be extracted, and the detection accuracy of the combustion ion current can be improved.

  Further, when the present invention is applied to a system including combustion state determination means for determining the combustion state of the internal combustion engine based on the ion current detection signal as in claim 3, it is based on the determination result of the final determination means. Then, the determination result of the combustion state determination means may be corrected by the correction means. In this way, erroneous determination of the combustion state due to smoldering can be prevented in advance, and the determination accuracy and reliability of the combustion state can be improved.

  By the way, in the high rotation / low load region, the leakage current varies due to the applied voltage variation during the energization period of the ignition coil. Therefore, the first smolder detection means using the ion current detection signal during the energization period of the ignition coil The smoldering state cannot be detected accurately in the rotation / low load range. An area exists.

  Therefore, as in claim 4, in the specific region set in the high rotation / low load region of the internal combustion engine, the detection of the first smolder detecting unit is prohibited or invalidated, and the detection of the second smolder detecting unit is performed. The result may be selected as a final smoldering state determination result, and in a region other than the specific region, the detection result of the first smoldering detection unit may be selected as the final smoldering state determination result. In this way, in the high rotation / low load region where the smoldering state cannot be accurately detected during the energization period of the ignition coil, the smoldering state is detected by the second smoldering detection means using the ion current detection signal during the intake / compression stroke. The detection accuracy can be ensured, and in other areas, the detection accuracy of the smoldering state can be ensured by the first smolder detection means using the ion current detection signal during the energization period of the ignition coil.

  According to a fifth aspect of the present invention, detection of the smoldering state by the first smoldering detection unit may be prohibited by the detection prohibition unit in a region where the battery voltage is equal to or higher than a predetermined voltage. The reason for this is that when the battery voltage is high, the ion current detection signal is likely to fluctuate due to fluctuations in the applied voltage during the energization period of the ignition coil, and the detection accuracy of the smoldering state is lowered.

  According to a sixth aspect of the present invention, the second smolder detecting means prohibits detection of the smoldering state by the second smolder detecting means by the detection prohibiting means in a low rotation region where the rotational state of the internal combustion engine is unstable. It is good to do. The reason for this is that the leakage current (drift current) during the intake / compression stroke is likely to fluctuate in the low rotation region where the rotation state of the internal combustion engine is unstable, and the detection accuracy of the smoldering state is lowered.

  By the way, if preignition occurs in the latter half of the energization period of the ignition coil, there is a possibility that leakage current due to smoldering and ion current due to preignition may overlap and it is difficult to distinguish between smoldering and preignition.

  Therefore, as in claim 7, when the present invention is applied to a system including preignition detection means for detecting preignition of the spark plug based on the ion current detection signal in the latter half of the energization period of the spark plug, The final determination means may validate the detection result of the pre-ignition detection means when the detection result of the second smolder detection means is no smolder. In this way, when preignition occurs during the energization period of the ignition coil, the preignition can be detected separately from smoldering.

  According to another aspect of the present invention, the final determination means may validate the detection result of the pre-ignition detection means when the detection result of the first smolder detection means is smolderless. In this way, when only the pre-ignition occurs during the energization period of the ignition coil, it is possible to prevent the pre-ignition from being erroneously determined as smoldering.

  According to a ninth aspect of the present invention, the final determination means prohibits or disables the detection of the pre-ignition detection means when the detection results of the first and second smolder detection means both have smolder. May be. In this way, it is possible to prevent erroneous determination of smoldering as pre-ignition.

  When carrying out the invention according to claims 1 to 9 as described above, as in claim 10, an arithmetic processing circuit for taking in an ion current detection signal by A / D conversion at a predetermined sampling period is provided, and the arithmetic processing is performed. The circuit executes smoldering state detection processing by the first smoldering detection means during the energization period of the ignition coil, and executes smoldering state detection processing by the second smoldering detection means during the intake / compression stroke. It is good to do. In this way, the function as the first smolder detection means and the second smolder detection can be achieved by switching the signal processing method for each smolder detection section using a single arithmetic processing circuit (microcomputer or digital IC). The functions as means can be realized with the same configuration, and the system configuration can be made inexpensive and with a high degree of freedom in detection.

Hereinafter, an embodiment embodying the best mode for carrying out the present invention will be described.
First, the circuit configuration of the ignition control system will be described with reference to FIG.
One end of the primary side winding 22 of the ignition coil 21 is connected to the battery 23, and the other end of the primary side winding 22 is connected to the collector of the power transistor 25 built in the igniter 24. One end of the secondary winding 26 is connected to the spark plug 27, and the other end of the secondary winding 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 control circuit 34. The ion current detection circuit 35 (ion current detection means) is composed of Zener diodes 28 and 29, a capacitor 30, an ion current detection resistor 31, an inverting amplification circuit 33, and the like.

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

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

  When the smoldering state of the spark plug 27 progresses, the insulation resistance value (smoldering resistance value) Rn between the electrodes 36 and 37 decreases, so that a leakage current (drift current) flows from the center electrode 36 to the ground electrode 37. This leakage current also flows along the same path as the ionic current, and the input potential Vin of the inverting amplifier circuit 33 changes according to the change of the leakage current flowing through the ionic current detection resistor 31, and the leakage current flows from the output terminal of the inverting amplifier circuit 33. The corresponding voltage V is output to the control circuit 34. When an ionic current is generated, an ionic current (hereinafter referred to as “combustion ionic current”) due to combustion of the air-fuel mixture and a leakage current flow in a superimposed manner.

Next, how the ion current output pattern of the ion current detection circuit 35 changes at the time of ignition, smoldering, preignition, and misfire will be described with reference to FIG.
If the ignition system is normal, a pulse-like noise current having a short time width is induced immediately after the start of energization of the primary coil 22 of the ignition coil 21 (immediately after the ignition signal is switched from OFF to ON). Immediately after the signal is switched from ON to OFF, LC resonance occurs due to the residual magnetic energy on the secondary side of the ignition coil 21, and then the waveform of the combustion ion current appears.

  Even if the smoldering of the spark plug 27 occurs, if the smoldering degree is light, the air-fuel mixture is ignited, so that the time width of the noise current induced immediately after the energization of the primary winding 22 is started becomes long. However, after ignition, the LC resonance noise and combustion ion current waveforms appear as in normal ignition.

On the other hand, when pre-ignition occurs, if the degree of pre-ignition is slight, an ion current due to pre-ignition starts to flow slightly before the end timing of the energization period of the ignition coil 21 (ON period of the power transistor 25). As the degree of pre-ignition becomes worse, the time when ion current starts to flow due to pre-ignition becomes earlier. For this reason, if both smoldering and preignition occur during the energization period of the ignition coil 21, the leakage current due to smoldering and the ionic current due to preignition may overlap, but the leakage current due to smoldering is caused by energization of the ignition coil 21. Since it flows from the beginning, the leakage current due to smolder begins to flow before the ion current due to pre-ignition.
Further, at the time of misfire, a pulsed noise current immediately after the start of energization of the ignition coil 21 and LC resonance noise after ignition appear, but the waveform of the ion current due to combustion does not appear.

  The ion current detection signal output from the ion current detection circuit 35 is taken into the control circuit 34 at a predetermined sampling period. The control circuit 34 is configured by using a microcomputer or a digital IC provided with peripheral devices such as an A / D converter for A / D converting the ion current detection signal, and various engine control routines stored in the ROM. Thus, fuel injection control and ignition timing control are performed, and the smoldering state of the spark plug 27 is detected by the following two methods using the ion current detection signal output from the ion current detection circuit 35.

[Method for detecting smoldering during energization period of ignition coil 21]
During the energization period of the ignition coil 21, the ion current detection signal is compared with a predetermined determination level Vth1, and the state in which the ion current detection signal (leakage current) exceeds the determination level Vth1 continues from the beginning of energization of the ignition coil 21. The time width (hereinafter referred to as “smolder detection time”) Tpl is measured, and the presence or absence of smolder is determined based on whether or not the smolder detection time Tpl exceeds the smolder determination value T1. This function corresponds to the first smolder detecting means in the claims.
[Method for detecting smoldering during intake and compression strokes]
During the intake / compression stroke, an ion current detection signal is detected as a leakage current DFT, and the presence or absence of smoldering is determined based on whether or not the leakage current DFT exceeds the smoldering determination value P2. This function corresponds to the second smolder detecting means in the claims.

Note that the smolder resistance value Rn of the spark plug 27 may be detected during the intake / compression stroke, and the presence or absence of smoldering may be determined based on whether or not the smolder resistance value Rn is equal to or less than the smolder determination value. At this time, during the intake / compression stroke, the ion current detection signal (leakage current DFT) is detected at least twice at an appropriate sampling interval Δt, the previous current detection value is i1, and the subsequent current detection value is i2. The smoldering resistance value Rn of the spark plug 27 may be calculated by an equation.
Rn = .DELTA.t / {Co.ln (i1 / i2)}-Ro
Here, Co is the capacitance of the capacitor 30, and Ro is the resistance value of the ion current detection resistor 31.

  The control circuit 34 detects preignition as follows based on the ion current detection signal during the energization period of the ignition coil 21. The pre-ignition is measured by measuring a time width (hereinafter referred to as “pre-ignition detection time”) Tpr during which the ion current detection signal exceeds the determination level Vth1 from the middle of the energization period of the ignition coil 21 to the end of the energization period. The presence or absence of pre-ignition is determined based on whether or not the detection time Tpr is longer than the pre-ignition determination value TO. This function corresponds to pre-ignition detection means in the claims.

  Further, the control circuit 34 detects the peak value PH of the ion current detection signal during the combustion / exhaust stroke (combustion ion current detection section), and a correction value f (DFT) corresponding to the leakage current DFT from the peak value PH. Is calculated to obtain a corrected peak value (net combustion ion current peak value) Pf obtained by removing the leakage current DFT from the ion current detection signal peak value PH, and is this corrected peak value Pf larger than the misfire determination value Vth2? The presence or absence of misfire is judged by no. This function corresponds to the combustion state determining means in the claims.

  By the way, when detecting the smoldering state based on the leakage current during the intake / compression stroke, as the smoldering state progresses and the smolder resistance value decreases as shown in FIG. Since the leakage current flows, the leakage current hardly flows thereafter, and the smoldering state cannot be detected. In addition, in the low rotation region where the engine rotation state is unstable, the leakage current is also unstable, and the smoldering state cannot be accurately detected.

  On the other hand, when the presence or absence of smoldering of the spark plug 27 is determined based on the time width Tpl of the leaking current flowing in the initial period of the energization period of the ignition coil 21, it is almost impossible to detect the leakage current in a region where the smolder resistance value is large. The smoldering state cannot be detected (see FIG. 8). In addition, in the high rotation / low load region, the leakage current varies due to the applied voltage variation during the energization period of the ignition coil 21, so that the smoldering state cannot be detected accurately. Furthermore, when pre-ignition occurs in the second half of the energization period of the ignition coil 21, there is a possibility that leakage current due to smoldering and ion current due to pre-ignition may overlap and it is difficult to distinguish between smoldering and pre-ignition.

  In this embodiment, therefore, the smoldering detection during the energization period of the ignition coil 21, the smoldering detection during the intake / compression stroke, and the pre-ignition detection are provided, and the specific set in the high rotation / low load region is provided. In the area A (see FIG. 6), the smolder detection during the energization period of the ignition coil 21 is prohibited or invalidated, and the smolder detection result during the intake / compression stroke is selected as the final smolder state determination result. In the other region, the smolder detection result during the energization period of the ignition coil 21 is directly selected as the final smolder state determination result.

  Further, when the battery voltage is high, the ion current detection signal is likely to fluctuate due to the fluctuation of the applied voltage during the energization period of the ignition coil 21, and the detection accuracy of the smoldering state is lowered. In the region (for example, 16 V or more), smoldering detection during the energization period of the ignition coil 21 is prohibited.

  In addition, in the low rotation region where the engine rotation state is unstable, the leakage current during intake and compression strokes fluctuates and the detection accuracy of the smoldering state decreases, so in this embodiment, the low rotation speed where the engine rotation state is unstable In the area, detection of smoldering during the intake / compression stroke is prohibited.

  Furthermore, in the present embodiment, when the smolder detection result during the intake / compression stroke is smolderless, the pre-ignition detection result is validated, and when the smolder detection result during the energization period of the ignition coil 21 is smolderless. The pre-ignition detection result is validated.

  Further, when the smolder detection result during the energization period of the ignition coil 21 and the smolder detection result during the intake / compression stroke are both smoldered, there is a possibility that leakage current due to smolder flows up to the ion current generation section due to pre-ignition. Yes, there is a possibility that smoldering may be misjudged as pre-ignition, so pre-ignition detection is prohibited or invalidated.

  The smoldering detection and preignition detection according to the present embodiment described above are executed by the control circuit 34 according to the routines shown in FIGS. The processing contents of these routines will be described below.

[Ion current detection signal processing routine]
The ion current detection signal processing routine of FIG. 3 is executed by the control circuit 34 at a predetermined ion current sampling period (for example, 20 μs period) during engine operation. This routine is executed by a microcomputer (or digital IC) dedicated to ion current detection provided separately from the control circuit 34, and the detection data is transmitted to the control circuit 34. The calculation processing load may be reduced.

  When this routine is started, first, in step 101, the A / D conversion value of the ion current detection signal output from the ion current detection circuit 35 is read. In the next step 102, whether the ignition coil 21 is energized or not. Determine whether or not. As a result, if it is determined that the energization period of the ignition coil 21 is reached, the process proceeds to step 103, and the smolder detection time Tpl and the pre-ignition detection time Tpr are measured by comparing the ion current detection signal with a predetermined determination level Vth1. Here, the smoldering detection time Tpl is a time width in which the ion current detection signal (leakage current) exceeds the determination level Vth1 from the beginning of energization of the ignition coil 21, and the preignition detection time Tpr is the ignition coil 21. The time duration during which the ion current detection signal exceeds the determination level Vth1 continues from the middle of the energization period to the end of the energization period.

If it is determined in step 102 that it is not the energization period of the ignition coil 21, the measurement processing of Tpl and Tpr in step 103 is omitted.
Thereafter, the routine proceeds to step 104, where it is determined whether or not the combustion / exhaust stroke is in progress (combustion ion current detection section). If the combustion / exhaust stroke is being performed, the routine proceeds to step 105 and the peak value of the ion current detection signal PH is detected. The peak value PH of the ion current detection signal is a peak value when the state where the ion current detection signal is equal to or greater than the misfire determination value Vth2 continues for a predetermined time or more.

On the other hand, if it is determined in step 104 that the combustion / exhaust stroke is not in progress, the peak value PH detection process in step 105 is omitted.
Thereafter, the routine proceeds to step 106, where it is determined whether or not the intake / compression stroke is being performed. If the intake / compression stroke is being performed, the routine proceeds to step 107 where the leakage current DFT is detected and this routine is terminated. If not in the compression stroke, the leakage current DFT detection process in step 107 is omitted, and this routine is terminated.

[Smoldering / misfire detection routine]
The smoldering / misfire detection routine of FIG. 4 is executed at predetermined intervals by the control circuit 34 during engine operation. When this routine is started, first, in step 201, the engine operating state (for example, engine speed, load factor, battery voltage, etc.) is read, and each detected value detected in the ion current detection signal processing routine of FIG. Read Tpl, Tpr, PH, DFT.

Thereafter, the process proceeds to step 202, and it is determined whether or not the first smoldering detection execution condition is satisfied. Here, the first smoldering detection execution condition is an execution condition for executing the smoldering detection during the energization period of the ignition coil 21, and by satisfying both of the following two conditions (1) and (2): is there.
(1) The engine operation area is an area other than the specific area A (see FIG. 6) set to the high rotation / low load area.
(2) The battery voltage is below a predetermined voltage (for example, 16V or less)

  If any one of these two conditions is not satisfied, the first smolder detection execution condition is not satisfied, and the routine proceeds to step 205 where the smolder detection flag X1ks is set to OFF which means no smoldering. set. For example, when the engine operating region is the specific region A set to the high rotation / low load region, or when the battery voltage is equal to or higher than a predetermined voltage (for example, 16 V or higher), the applied voltage fluctuation during the energization period of the ignition coil 21 As a result, the leakage current is likely to fluctuate and the smoldering state cannot be detected with high accuracy, so that smoldering detection during the energization period of the ignition coil 21 is prohibited.

  On the other hand, if both of the above two conditions (1) and (2) are satisfied, the first smolder detection execution condition is established, and the routine proceeds to step 203 where the smolder detection time detected during the energization period of the ignition coil 21 is established. If Tpl is compared with smoldering judgment value T1, and if smoldering detection time Tpl is larger than smoldering judgment value T1, smoldering detection flag X1ks is set to ON indicating smoldering during energization period (step 204), and smoldering detection time is set. If Tpl is equal to or less than the smolder determination value T1, the smolder detection flag X1ks is set to OFF, which means no smolder, during the energization period (step 205).

  Thereafter, the process proceeds to step 206, and it is determined whether or not the second smoldering detection execution condition is satisfied. Here, the second smoldering detection execution condition is an execution condition for executing smoldering detection during the intake / compression stroke, and whether or not the engine rotational speed is equal to or higher than a predetermined rotational speed (for example, 300 rpm or higher), It is determined whether the second smoldering detection execution condition is satisfied. For example, in the low rotation range of 300 rpm or less, the engine rotation state is unstable, the leakage current during the intake / compression stroke is likely to fluctuate, and the detection accuracy of the smoldering state decreases, so the engine rotation state is unstable and low rotation In the region, the second smolder detection execution condition is not satisfied, and the routine proceeds to step 209, where the smolder detection flag X2ks is set to OFF which means no smolder during the intake / compression stroke.

  On the other hand, if the engine rotation speed is equal to or higher than the predetermined rotation speed, the second smolder detection execution condition is satisfied, the process proceeds to step 207, and the leakage current DFT detected during the intake / compression stroke is compared with the smolder determination value P2. If the leakage current DFT is larger than the smoldering judgment value P2, the smoldering detection flag X2ks is set to ON indicating smoldering during the intake / compression stroke (step 208), and the leakage current DFT is less than the smoldering judgment value P2. For example, during the intake / compression stroke, the smolder detection flag X2ks is set to OFF which means no smoldering (step 209).

  Thereafter, the process proceeds to step 210, where it is determined whether the smolder detection flag X1ks during the energization period or the smolder detection flag X2ks during the intake / compression stroke is ON (with smolder). The smolder abnormality flag Xpp used for vehicle self-diagnosis (diagnosis) is set to ON (smolder abnormality), and this routine ends.

  On the other hand, if it is determined in step 210 that both the smoldering detection flags X1ks and X2ks are both OFF, the process proceeds to step 213, and the leakage current is detected from the ion current detection signal peak value PH detected during the combustion / exhaust stroke. A correction peak value (net combustion ion current peak value) Pf obtained by subtracting the leakage current DFT from the ion current detection signal peak value PH is obtained by subtracting the correction value f (DFT) corresponding to the DFT. The processing in step 213 serves as correction means in the claims.

  Thereafter, the routine proceeds to step 214, where the corrected peak value Pf is compared with the misfire determination value Vth2. If the corrected peak value Pf is larger than the misfire determination value Vth2, the routine proceeds to step 215, where ignition is determined and the misfire detection flag Xf is set. If it is set to OFF and the corrected peak value Pf is equal to or less than the misfire determination value Vth2, the routine proceeds to step 216, where it is determined that misfire has occurred and the misfire detection flag Xf is set to ON.

[Preignition detection routine]
The pre-ignition detection routine of FIG. 5 is executed at a predetermined cycle by the control circuit 34 during engine operation. When this routine is started, it is first determined in step 301 whether or not the smolder detection flag X2ks during the intake / compression stroke is ON (with smoldering), and the smolder detection flag X2ks during the intake / compression stroke is OFF ( If no smoldering), the routine proceeds to step 306, where the pre-ignition detection time Tpr detected during the energization period of the ignition coil 21 is compared with the pre-ignition determination value TO, and the pre-ignition detection time Tpr is greater than the pre-ignition determination value TO. If it is larger, the pre-ignition detection flag Xpr is set to ON which means the presence of pre-ignition (step 307), and if the pre-ignition detection time Tpr is less than or equal to the pre-ignition determination value TO, the pre-ignition detection flag Xpr is not pre-ignitioned. Set to OFF, meaning That (step 308).

  On the other hand, if it is determined in step 301 that the smoldering detection flag X2ks is set to ON (with smoldering) during the intake / compression stroke, the routine proceeds to step 302, where the smoldering detection flag X1ks is ON (with smoldering). If the smolder detection flag X1ks is OFF (no smolder) during this energization period, the process proceeds to step 306, and whether or not the pre-ignition detection time Tpr is longer than the pre-ignition determination value TO. Then, the presence or absence of pre-ignition is determined, and the pre-ignition detection flag Xpr is set to ON or OFF according to the determination result (steps 307 and 308).

  On the other hand, if it is determined as “Yes” in the above steps 301 and 302 (when both smolder detection flags X1ks and X2ks are both ON), it is determined that the smolder is severe and step 303 is performed. Then, it is determined whether or not the pre-ignition detection time Tpr is longer than the pre-ignition determination value TO. In this case, even when severe smoldering occurs, if the pre-ignition detection time Tpr is equal to or shorter than the pre-ignition determination value TO, it can be confirmed that no pre-ignition has occurred, so the process proceeds to step 305 and the pre-ignition detection flag Xpr is set. Set to OFF.

  On the other hand, when severe smoldering occurs (when both smoldering detection flags X1ks and X2ks are both ON), even if the preignition detection time Tpr is longer than the preignition determination value TO, it is not determined that preignition has occurred. (Pre-ignition detection is prohibited or invalidated). This is because when a severe smolder occurs, a leakage current due to the smolder may flow up to an ion current generation period due to pre-ignition, and the smolder may be erroneously determined as pre-ignition. In this case, the pre-ignition detection flag Xpr is maintained in the same state as the previous time (step 304).

  According to the present embodiment described above, the smoldering detection during the energization period of the ignition coil 21, the smoldering detection during the intake / compression stroke, and the pre-ignition detection are provided and set in the high rotation / low load region. In the specified area A (see FIG. 6), the smolder detection during the energization period of the ignition coil 21 is prohibited or invalidated, and the smolder detection result during the intake / compression stroke is selected as the final smolder state determination result, In regions other than the specific region A, the smolder detection result during the energization period of the ignition coil 21 is selected as it is as the final smoldering state determination result, so that the smolder detection accuracy is higher according to the engine operating region. It is possible to detect the smoldering state by selecting the smoldering detection method, and it is possible to detect the smoldering state more accurately than in the past.

  In addition, in this embodiment, the ion current detection signal peak value PH detected during the combustion / exhaust stroke is corrected according to the leakage current DFT (smoldering state detection result), and the leakage current is calculated from the ion current detection signal peak value PH. Since the corrected peak value (net combustion ion current peak value) Pf from which the DFT component has been removed is obtained, the presence or absence of a misfire (combustion state) can be accurately determined using the corrected peak value Pf.

  In the present invention, the determination result of the combustion state (for example, the misfire degree) may be corrected according to the leakage current DFT (detection result of the smoldering state).

  In the present embodiment, since the smoldering detection during the energization period of the ignition coil 21 is prohibited when the battery voltage is equal to or higher than a predetermined voltage (for example, 16 V or more), the applied voltage during the energization period of the ignition coil 21 It is possible to prevent erroneous detection of a smoldering state caused by fluctuations in leakage current due to fluctuations.

  Furthermore, in this embodiment, when the engine rotation speed is in a low rotation region below a predetermined rotation speed (for example, 300 rpm or less), detection of smoldering during the intake / compression stroke is prohibited, so the engine rotation state is unstable. This makes it possible to prevent erroneous detection of a smoldering state caused by fluctuations in leakage current in a low rotation region.

  Further, in this embodiment, when the smolder detection result during the intake / compression stroke is smolderless, the pre-ignition detection result is valid, and when the smolder detection result during the energization period of the ignition coil 21 is smolderless. Since the pre-ignition detection result is validated, the pre-ignition can be detected separately from the smoldering.

  In addition, in this embodiment, when severe smoldering occurs (when both smoldering detection flags X1ks and X2ks are both ON), even if the preignition detection time Tpr is longer than the preignition judgment value TO, Since occurrence is not determined (pre-ignition detection is prohibited or invalid), it is possible to prevent smoldering from being erroneously determined as pre-ignition.

  Even when only one of the two smoldering detection flags X1ks and X2ks is ON (when a slight smoldering occurs), the detection of preignition may be prohibited or invalidated.

  In addition, the present invention can be implemented with various modifications, such as the smolder detection method and the pre-ignition detection method may be appropriately changed.

It is a circuit diagram which shows the structure of the ignition control system and ion current detection circuit in one Example of this invention. It is a time chart explaining how the ion current output pattern of the ion current detection circuit changes at the time of ignition, smoldering, preignition, and misfire. It is a flowchart explaining the flow of a process of an ion current detection signal processing routine. It is a flowchart explaining the flow of a process of a smoldering / misfire detection routine. It is a flowchart explaining the flow of a process of a pre-ignition detection routine. It is a figure which shows roughly the map which sets the area | region which prohibits the smoldering detection during an ignition coil energization period. It is a figure explaining the relationship between the leakage current in the case of detecting a smoldering state based on the leakage current in an intake / compression stroke, and a smolder resistance value. It is a figure explaining the relationship between the time width of a leakage current in the case of detecting a smoldering state based on the time width (smolding detection time) of the leakage current which flows in the initial stage of the energization period of an ignition coil, and a smolder resistance value.

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 amplifier circuit, 34 ... Control Circuit (first smolder detecting means, second smolder detecting means, final judging means, correcting means, pre-ignition detecting means), 35 ... ion current detecting circuit (ion current detecting means), 36 ... center electrode, 37 ... grounding electrode

Claims (10)

In an ionic current detection device for an internal combustion engine comprising an ionic current detection means for detecting an ionic current generated along with combustion of an air-fuel mixture in a combustion chamber of the internal combustion engine through an ignition plug,
First smolder detecting means for detecting a smoldering state of the spark plug based on an ion current detection signal during the energization period of the ignition coil;
Second smolder detecting means for detecting a smoldering state of the spark plug based on an ion current detection signal during the intake and compression strokes;
An ionic current detection apparatus for an internal combustion engine, comprising: final determination means for finally determining a smoldering state of the spark plug based on detection results of both the first and second smolder detection means.   2. The ion current detection apparatus for an internal combustion engine according to claim 1, further comprising correction means for correcting the ion current detection signal based on a determination result of the final determination means. Combustion state determination means for determining the combustion state of the internal combustion engine based on the ion current detection signal;
2. The ion current detection device for an internal combustion engine according to claim 1, further comprising correction means for correcting the determination result of the combustion state determination means based on the determination result of the final determination means.   The final judging means prohibits or invalidates the detection of the first smolder detecting means in the specific region set in the high rotation / low load region of the internal combustion engine, and finally determines the detection result of the second smolder detecting means. 2. The smoldering state determination result is selected, and the detection result of the first smoldering detection unit is selected as the final smoldering state determination result as it is in a region other than the specific region. The ion current detection device for an internal combustion engine according to any one of claims 1 to 3.   5. The internal combustion engine according to claim 1, further comprising a detection prohibiting unit that prohibits detection of a smoldering state by the first smoldering detection unit in a region where the battery voltage is equal to or higher than a predetermined voltage. Ion current detection device.   6. A detection prohibiting unit for prohibiting detection of a smoldering state by the second smoldering detection unit in a low rotation region where the rotational state of the internal combustion engine is unstable. An ion current detection device for an internal combustion engine as described. Pre-ignition detection means for detecting pre-ignition of the ignition plug based on an ion current detection signal in the latter half of the energization period of the ignition plug;
The final determination means validates the detection result of the pre-ignition detection means when the detection result of the second smolder detection means is smolderless. An ion current detection device for an internal combustion engine.   The ionic current of the internal combustion engine according to claim 7, wherein the final determination means validates the detection result of the pre-ignition detection means when the detection result of the first smolder detection means is smolderless. Detection device.   9. The final determination means for prohibiting or invalidating detection of the pre-ignition detection means when both the detection results of the first and second smolder detection means are smoldering. An ion current detection device for an internal combustion engine as described. An arithmetic processing circuit that captures the ion current detection signal by A / D conversion at a predetermined sampling period;
The arithmetic processing circuit executes smoldering state detection processing by the first smoldering detection means during the energization period of the ignition coil, and smoldering state detection processing by the second smoldering detection means during the intake / compression stroke. The ionic current detection device for an internal combustion engine according to any one of claims 1 to 9, wherein:

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