JP2009156143A - Method and device for detecting combustion state of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and device for detecting a combustion state of an internal combustion engine capable of surely detecting smouldering. <P>SOLUTION: Voltage generating ion current by ion generated by combustion is applied on an electrode of a spark plug. Current flowing via the electrode for a predetermined detection section including a period during which at least ignition signal is generated by the application of the voltage is detected, and existence of smouldering at the spark plug is detected by determining whether predetermined noise is included in the detected current. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a combustion state detection method and apparatus for an internal combustion engine having a smoldering detection function.

  In an internal combustion engine, when incomplete combustion of the fuel-air mixture occurs in the cylinder, carbon deposits are generated, and the carbon deposits adhere to the surface of the insulator between the spark plug electrodes and insulate between the spark plug electrodes. Resistance decreases and in some cases can lead to misfire. This phenomenon is usually referred to as smoldering, but when smoldering occurs, the operation of the internal combustion engine becomes unstable. In addition, a hot spot or the like due to the residual heat of the carbon deposit is generated in the cylinder, which may cause so-called preignition that causes spontaneous ignition before the ignition time of the air-fuel mixture due to discharge of the spark plug. When pre-ignition occurs, the operation of the internal combustion engine becomes unstable, and in some cases, the internal combustion engine may be damaged.

  Smoldering often occurs in the low-speed rotation region of the internal combustion engine. When smoldering is detected, the internal combustion engine is automatically rotated at a high speed for a predetermined period by the control device of the internal combustion engine, and carbon deposits adhering to the spark plug are burned out. May be controlled. Also, when the occurrence of pre-ignition is detected, the pre-ignition suppression control is performed so that the combustion temperature in the cylinder is lowered by controlling the air-fuel ratio to the fuel rich side, and the temperature of the ignition part and hot spot of the spark plug is lowered. Things to do are known.

  As is well known, when the fuel-air mixture burns, ions are generated in the cylinder. Conventionally, the generated ions are detected as an ion current to detect pre-ignition, and the leakage current due to the smolder is detected. A detection method has been proposed to detect (see, for example, Patent Document 1). The conventional detection method disclosed in Patent Document 1 detects smoldering based on the leakage current of the spark plug in the first half of the ignition coil during the energization period to the primary coil (ignition signal generation period). The pre-ignition is detected based on the ion current in the latter half of the energization period.

JP-A-9-317620

  In the case of the above-mentioned conventional device, if the occurrence of pre-ignition becomes severe and the ignition signal generation timing is shifted to an early stage, the leakage current due to smoldering and the ionic current due to pre-ignition overlap, and the leakage occurs at the time of smolder detection. There is a problem that it is difficult to distinguish between current and ion current and it is difficult to reliably detect the occurrence of smoldering.

  An object of the present invention is to solve the above-described problems in conventional apparatuses, and to obtain a combustion state detection method for an internal combustion engine that can reliably detect the occurrence of smoldering.

  Another object of the present invention is to provide a combustion state detection device for an internal combustion engine that can reliably detect the occurrence of smoldering.

  The method for detecting the combustion state of an internal combustion engine according to the present invention is an electrode that is installed in a combustion chamber of an internal combustion engine, generates a spark discharge in the combustion chamber by igniting an air-fuel mixture, and burns it. A method for detecting a combustion state in an internal combustion engine comprising: an ignition plug comprising: an ignition plug; and an ignition coil that induces the ignition voltage based on generation of an ignition signal, wherein an ion current caused by ions generated by the combustion is detected. A voltage to be generated is applied to the electrode of the spark plug, and a current flowing through the electrode is detected in a predetermined detection section including at least a period in which the ignition signal is generated by the application of the voltage. It is a method characterized by detecting the presence or absence of smoldering in the spark plug by determining whether or not predetermined noise is included in the current.

  The combustion state detecting device for an internal combustion engine according to the present invention is installed in a combustion chamber of the internal combustion engine, and an ignition voltage is applied to generate a spark discharge in the combustion chamber to ignite an air-fuel mixture and burn it. An apparatus for detecting a combustion state in an internal combustion engine comprising an ignition plug having an electrode for causing ignition and an ignition coil for inducing the ignition voltage based on generation of an ignition signal, wherein the ions are generated by ions generated by the combustion A voltage applying device for applying a voltage for generating a current to the electrode of the spark plug; a current detecting device for detecting a current flowing through the electrode by a voltage applied by the voltage applying means; and the ignition signal is generated. A detection interval setting device that sets a predetermined detection interval including a predetermined period, and a current flowing in the detection interval of the current detected by the current detection device is predetermined Is a device which is characterized in that a smoldering detection means for detecting the occurrence of smoldering in the spark plug by determining whether it contains a noise.

  According to the combustion state detection method for an internal combustion engine according to the present invention, a voltage for generating an ionic current due to ions generated by combustion is applied to the electrode of the ignition plug, and at least a period during which an ignition signal is generated by the application of the voltage. The presence or absence of smoldering in the spark plug is detected by detecting a current flowing through the electrode in a predetermined detection section and determining whether or not the detected current includes a predetermined noise. Since it is detected, the smoldering of the spark plug can be reliably detected regardless of the presence or absence of the ionic current due to pre-ignition.

  According to the combustion state detecting device for an internal combustion engine of the present invention, a voltage applying device for applying a voltage for generating an ionic current due to ions generated by combustion to the electrode of the spark plug, and a voltage applied by the voltage applying means. A current detection device for detecting a current flowing through the electrode, a detection interval setting device for setting a predetermined detection interval including a period in which an ignition signal is generated, and a current detected by the current detection device Since it has smolder detecting means for detecting the presence or absence of smoldering in the spark plug by determining whether or not a predetermined noise is included in the current flowing in the detection section, a simple configuration Thus, it is possible to reliably detect the smoldering of the spark plug regardless of the presence or absence of an ion current due to pre-ignition.

Embodiment 1 FIG.
Hereinafter, a combustion state detection method and apparatus for an internal combustion engine according to Embodiment 1 of the present invention will be described in detail with reference to the drawings. 1 is a circuit diagram showing a partial circuit configuration of a combustion state detection apparatus for an internal combustion engine according to Embodiment 1 of the present invention.

  In FIG. 1, a spark plug 5 installed in a combustion chamber (not shown) of an internal combustion engine includes a pair of electrodes opposed via a gap, and these electrodes are exposed in the combustion chamber. When an ignition voltage is applied between the electrodes, a spark discharge is generated to ignite the air-fuel mixture in the combustion chamber and burn it. The ignition coil 1 includes a primary coil 2 connected to a power source VB from a battery (not shown), and a secondary coil 3 coupled to the primary coil 2 via a magnetic iron core.

  The primary coil 2 is connected in series to the transistor 4, and ignition to be described later from an engine control unit (hereinafter referred to as ECU) 12 including a microprocessor (hereinafter referred to as MPU) provided in the vehicle. By receiving the signal and conducting, the primary current is supplied from the power supply VB and energized. When the primary current supply to the primary coil 2 is stopped, the ignition coil 1 induces a negative high voltage as an ignition voltage in the secondary coil 3 and applies this ignition voltage to the electrode of the spark plug 5.

  The bias circuit 7 is inserted between the secondary coil 3 and the ground potential portion of the vehicle. The capacitor 9, the Zener diode 8 connected in parallel to the capacitor 9, and these parallel circuits are connected in series. And a diode 10. The bias circuit 7 applies a positive voltage to the electrode of the spark plug 5 in order to detect an ion current due to pre-ignition described later and a leakage current due to smoldering of the internal combustion engine.

  The spark plug 5 has a function as a probe for detecting an ionic current and a leakage current in addition to the function of generating a spark discharge for igniting the fuel-air mixture. An ion current detection circuit 11 serving as a current detection means is connected to the cathode side of the diode 10, detects the aforementioned ion current and leakage current flowing through the electrode of the spark plug 5, and inputs the detected current value to the ECU 12. To do. The primary coil 2, the secondary coil 3, the transistor 4, the bias circuit 7, and the ion current detection circuit 11 are integrally configured as the ignition coil 1 and are mounted on the internal combustion engine.

  FIG. 10 is an explanatory diagram showing a current waveform when a severe smoldering and strong preignition occur in the ignition plug of the internal combustion engine. When the ignition signal shown in FIG. 10A is turned on at time t1, the transistor 4 shown in FIG. 1 is turned on, and the primary current is supplied to the primary coil 2 from the power source VB. As a result, a secondary voltage V2 having a peak value of about 1 [KV], for example, is induced in the secondary coil 3 as shown in FIG. Due to the secondary voltage V2, as shown in (C) and (D), a noise current In resulting from the capacitance flows instantaneously in the ignition system. When the ignition signal is turned off at time t2, the transistor 4 is turned off and the primary current to the primary coil 2 is cut off.

  By blocking the primary current flowing through the primary coil 2, an ignition voltage V2i, which is a negative high voltage of, for example, about 20 [KV] is induced in the secondary coil 3. The ignition voltage V2i is generated, for example, at a time around a crank angle of −10 ° CA and is applied between the electrodes of the spark plug 5 to generate a spark discharge between the electrodes. The discharge current due to the spark discharge flows from the electrode on the ground side of the spark plug 5 to the electrode connected to the secondary coil 3, and charges the capacitor 9 via the secondary coil 3. When the capacitor 9 reaches a predetermined charging voltage, the Zener diode 8 breaks down, and the discharge current flows to the ground side via the diode 10.

  The fuel-air mixture in the combustion chamber is ignited and burned immediately before the crank angle of 0 ° CA, which is the top dead center of the piston, by the spark discharge of the spark plug 5, and the internal combustion engine shifts to the combustion stroke C2. When the fuel-air mixture burns, ions are generated in the combustion chamber, but a bias voltage VL of, for example, about 100 [V] based on the charging voltage of the capacitor 9 is applied between the electrodes of the spark plug 5. As shown in (D), the ion current Id flows following the noise current In. The ion current Id gradually attenuates and becomes almost zero at the stage from the end of the combustion stroke to the exhaust stroke C3.

  When smoldering becomes severe, for example, when a secondary voltage of 800 [V] is applied between the electrodes of the spark plug 5, a leakage current Ik of about 400 [μA] at the peak is obtained as shown in FIG. After that, the flow gradually decreases, but continues to flow during the period from t1 to t2 when the ignition signal is applied. The leakage current Ik flows through the spark plug 5 due to smoldering following the noise current In due to the bias voltage VL applied between the electrodes of the spark plug 5 in the combustion stroke C2 after ignition. In this case, if the bias voltage is 100 [V], the leakage current Ik is about 50 [μA].

  When a strong preignition occurs in the combustion chamber, an ion current Ip based on the preignition flows after the noise current In as shown in FIG. The ion current Ip due to this pre-ignition has a peak value of about 500 [μA] when the secondary voltage V2 is, for example, 500 [V], and thereafter gradually attenuates. An ion current Id based on ions generated by the spark discharge of the spark plug 5 flows through the spark plug 5 due to the bias voltage VL applied between the electrodes of the spark plug 5 in the combustion stroke C2 after ignition. It becomes. In this case, if the bias voltage is 100 [V], the ion current Id has a peak value of about 100 [μA].

  If smoldering and preignition occur at the same time, the leakage current Ik due to smoldering and the ion current Ip due to preignition are superimposed and flow from the ignition coil 1 to the ground potential portion via the spark plug 5.

  The ion current detection circuit 11 shown in FIG. 1 can detect any of the leakage current Ik due to smoldering, the ion current Ip due to preignition, and the ion current Id due to spark discharge of the spark plug 5. However, when the leakage current Ik caused by smoldering and the ionic current Ip caused by pre-ignition flow, the current value detected by the ion current detection circuit 11 is either the leakage current Ik caused by smoldering or the ion current Ip caused by pre-ignition. You can't tell if it is.

  2A and 2B are explanatory diagrams for explaining a combustion state detection method for an internal combustion engine according to Embodiment 1 of the present invention, in which FIG. 2A is a waveform diagram showing an ignition signal, and FIG. 2B is a case where smoldering occurs in an ignition plug. (C) is a waveform diagram of ion current when a slight pre-ignition occurs, and (D) is a waveform diagram of ion current when a severe pre-ignition occurs. Indicates.

  In FIG. 2, when the ignition signal shown in FIG. 2A is given to the transistor 4 at the time point t1, if the smoldering is generated in the spark plug 5, as shown in FIG. Based on the noise current In, a leakage current Ik due to smoldering flows. A high-frequency noise current Ikn is intermittently superimposed on the leakage current Ik. This high-frequency noise current Ikn is usually a high-frequency current having a frequency of 10 [KHz] or higher. The reason why the high-frequency noise current Ikn is superimposed on the leakage current Ik due to smoldering is considered to be mainly due to uncertain adhesion of the carbon deposit between the electrodes of the ignition plug 5 to the surface of the insulator due to smoldering. It is done. On the other hand, the high-frequency noise current as described above is not superimposed on the ion current Ip based on the occurrence of pre-ignition shown in FIGS.

  When the leakage current Ik due to smoldering shown in FIG. 2B is subjected to frequency analysis in the detection zone Z described later, the high frequency band intensity is increased by the high frequency noise current Ik as shown in the figure. On the other hand, when the ion current Ip at the time of the occurrence of severe pre-ignition shown in FIG. 2D is subjected to frequency analysis, the intensity of the high frequency band is weak as shown in the figure, and the intensity of the high frequency band of about 10 [KHz] or more is 0. Become.

  Therefore, in the combustion state detection method for an internal combustion engine according to Embodiment 1 of the present invention, a voltage for generating an ion current due to ions generated by combustion is applied to the electrode of the spark plug, and at least an ignition signal is generated by the application of the voltage. Current flowing through the electrode of the spark plug within a predetermined detection interval including the period during which the spark plug is detected, and detecting the occurrence of smoldering in the spark plug based on the frequency component of the detected current is there.

  Next, an internal combustion engine combustion state detection apparatus according to Embodiment 1 of the present invention, which uses the internal combustion engine combustion state detection method according to Embodiment 1 described above, will be described. FIG. 3 is a block diagram showing the overall configuration of the internal combustion engine combustion state detection apparatus according to Embodiment 1 of the present invention.

  In FIG. 3, the ion current detection circuit 11 detects an ion current or leakage current flowing through the spark plug 5 and the ignition coil 1 or a current on which both are superimposed. Here, the ion current is the ion current due to the combustion of the fuel based on the spark discharge of the ignition plug 5 and the ion current due to the occurrence of pre-ignition as described above, and the leakage current is the leakage current due to the smolder generated in the ignition plug 5. It is.

  In addition to the well-known control function of the internal combustion engine, the ECU 12 includes a part of the configuration as the combustion state detection device for the internal combustion engine according to the first embodiment of the present invention, as described below. That is, the ECU 12 includes an A / D conversion device 16, a detection section setting device 18, and a smolder detection unit 19 including a noise determination unit 20. The detection section setting device 18 and the smoldering detection means 19 provided with the noise discrimination means 20 are constituted by an MPU provided in the ECU 12.

  The A / D conversion device 16 converts the analog current value detected by the ion current detection circuit 11 into a digital current value and inputs the digital current value to the detection section setting device 18. The detection section setting device 18 sets a detection section Z for analyzing the current value based on the digital signal converted by the A / D conversion device 18. As shown in FIG. 2, the detection zone Z set by the detection zone setting device 18 is the time t2 when the ignition signal is turned off from the time t11 when the influence of the noise current In generated at the time t1 when the ignition signal is turned on is eliminated. Is set to a period up to a time point t12. That is, the period from time t1 to t11 is a mask period. The detection zone Z is set based on the crank angle detected by the crank angle sensor of the internal combustion engine, but is set including at least the period during which the ignition signal is generated. Details of the setting of the detection section Z will be described later.

  The noise discriminating means 20 provided in the smoldering detecting means 19 discriminates whether or not a predetermined noise exists in the current in the detection zone Z detected by the ion current detecting circuit 11. In the first embodiment, the noise determination unit 20 determines that predetermined noise is present when a current component of approximately 10 [KHz] or more is detected by, for example, analysis using a bandpass filter or Fourier transform.

  Next, the operation of the internal combustion engine combustion state detection apparatus according to Embodiment 1 of the present invention will be described. In FIG. 3, a bias voltage is applied between the electrodes of the spark plug 5 by a bias circuit 7 in order to generate an ion current due to ions generated by combustion. The ion current detection circuit 11 detects the ion current and inputs it to the ECU 12. As shown in FIG. 10, the current detected by the ion current detection circuit 11 includes an ion current Id caused by combustion of fuel based on a spark discharge of the spark plug 5, an ion current Ip when preignition occurs, and a smoldering. This may be the leakage current Ik when. When severe pre-ignition occurs and smoldering occurs, the ion current Ip and the leakage current Ik are detected in a superimposed manner. The A / D conversion device 16 provided in the ECU 12 converts an analog signal indicating a current value detected by the ion current detection circuit 11 into a digital signal and inputs the digital signal to the detection section setting device 18.

  FIG. 4 is a flowchart showing the operations of the detection section setting device 18 and the smolder detection means 19. In FIG. 4, first, in step S11, it is determined whether or not the current value detected by the ion current detector 11 is larger than the ion generation threshold value Th. Here, the ion determination threshold Th has a meaning of determining the start time of the detection section Z after the mask period. That is, as shown in FIG. 2, when the ion generation threshold Th is set, the current value detected after the end of the mask period for cutting the noise current In exceeds the ion generation threshold Th first. This time becomes the start position of the detection zone Z.

  For example, if the leakage current Ik due to smoldering flows as shown in FIG. 2 (B), the time when the ion generation threshold Th is first exceeded is t11, and the detection zone Z is a predetermined time after the time t11. It is set as a period until t12. On the other hand, as shown in FIG. 2C, if a mild pre-ignition has occurred, the time when the ion current Ip due to the occurrence of the mild pre-ignition first exceeds the ion generation threshold Th is t21, The detection zone Z is set as a period from time t21 to time t22 after a predetermined time. Also, as shown in FIG. 2D, if a severe preignition has occurred, the time when the ion current Ip first exceeds the ion generation threshold Th is t11, and the detection zone Z is shown in FIG. As in the case of (B), it is set as the period from time t11 to t12.

  Returning to FIG. 4, if the result of determination in step S <b> 11 is that the detected current value is not larger than the ion generation threshold Th, the process proceeds to step S <b> 12. In step S12, it is determined whether or not energization of the current is completed within the period in which the ignition signal is generated. If completed, the process proceeds to step S110 and it is determined that pre-ignition has not occurred, and the processing routine is executed. finish. As a result of the determination in step S12, when it is determined that energization has not ended, the process returns to step S11 and the process is repeated.

  Next, as a result of the determination in step S11, when it is determined that the detected current is larger than the ion generation threshold Th, a predetermined detection zone Z is set from that point and the process proceeds to step S13, where the ion The value of current or leakage current is stored in the memory and held. Next, it progresses to step S14 and it is determined whether the supply of the electric current detected in the set detection zone Z was complete | finished. If the detected current is an ionic current caused by slight pre-ignition, the detection zone Z is set as a period from time t21 to t22 as shown in FIG. 2C, and the ionic current caused by pre-ignition is set. Since the energization of Ip ends at the end of the ignition signal, the determination result in step S14 is YES, and the process proceeds to step S18, where it is determined that pre-ignition has occurred.

  On the other hand, if the detected current is an ionic current due to severe pre-ignition, the energization does not end within the set detection zone Z as shown in FIG. 2D, so the determination result in step S14 is It becomes NO and progresses to step S15. If the detected current is a leakage current due to the occurrence of smoldering, as shown in FIG. 2B, the energization does not end within the set detection zone Z, so the determination result in step S14 is NO The process proceeds to step S15. Furthermore, when severe pre-ignition and smoldering occur simultaneously, since the ion current Ip and the leakage current Ik are superimposed, the determination result in step S14 is still NO, and the process proceeds to step S15. .

  In step S15, it is determined whether or not the value of the current held in the memory has a condition capable of Fourier analysis, that is, whether or not the number of FFT points is exceeded. If not, the process returns to step S3 and the operation is repeated. . If it exceeds FFT, the process proceeds to step S16, the current held in the memory is Fourier analyzed, and the process proceeds to step S7. In step S17, as a result of Fourier analysis, it is determined whether or not the intensity of the high frequency component is strong. If not, the process proceeds to step S18, where it is determined that the ion current is due to preignition, and occurrence of preignition is detected. The process ends. As a result of the determination in step S17, if it is determined that the intensity of the high-frequency component is strong, the process proceeds to step S19, where it is determined that the leakage current is caused by smoldering, the occurrence of smolder is detected, and the process is terminated. The determination of the strength of the high frequency component in step S17 is performed based on whether or not a high frequency component of, for example, 10 [KHz] or more exists as described above.

  In the above description, the case where the current stored in the memory is processed by Fourier analysis has been described. However, the current stored in the memory is processed using a bandpass filter to determine the strength of the high frequency component. May be.

  As described above, according to the combustion state detection method and apparatus for an internal combustion engine according to the first embodiment of the present invention, smoldering can be ensured even if ion current due to pre-ignition and leakage current due to smolder are superimposed. The leakage current can be detected, and the leakage current is detected by paying attention to the frequency of noise generated in the leakage current due to smoldering, so that the detection accuracy can be improved.

Embodiment 2. FIG.
Next, a combustion state detection method and apparatus for an internal combustion engine according to Embodiment 2 of the present invention will be described. In the combustion state detection method for an internal combustion engine according to Embodiment 2 of the present invention, a voltage for generating an ion current due to ions generated by combustion is applied to the electrode of the spark plug, and at least an ignition signal is generated by the application of the voltage. Noise detected by detecting the current flowing through the electrode of the spark plug within a predetermined detection interval including a certain period and comparing the detected current value with the filter value obtained by filtering the detected current. The presence or absence of smoldering is discriminated to detect the occurrence of smoldering in the spark plug.

  5A and 5B are explanatory diagrams for explaining a combustion state detection method for an internal combustion engine according to Embodiment 2 of the present invention, where FIG. 5A is a waveform diagram showing an ignition signal, and FIG. 5B is a case where smoldering occurs in the spark plug. (C) is a waveform diagram showing a filter value obtained by filtering the leakage current Ik, and (D) is an ion current Ip when severe preignition occurs. (E) is a waveform diagram showing a filter value obtained by filtering the ion current Ip, (F) is a waveform diagram showing an absolute value of a deviation between the leakage current Ik and the filter value IF1, (G ) Is a waveform diagram showing the absolute value of the deviation between the ion current Ip and the filter value 2. Filter waveforms IF1 and IF2 shown in (C) and (D) of FIG. 5 are obtained by filtering the current detected by the ion current detection circuit 11. Examples of the filter processing include a case where the detected current is based on a moving average, and a case where a median filter or a low-pass filter is used, but is not limited thereto.

  In FIG. 5, when the ignition signal shown in FIG. 5A is given to the transistor 4 at the time point t1, when the smoldering is generated in the spark plug 5, noise based on the capacitance as shown in FIG. A leakage current Ik due to smoldering flows following the current In. A high-frequency noise current Ikn is intermittently superimposed on the leakage current Ik. As described above, the high-frequency noise current Ikn is usually a high-frequency current having a frequency of 10 [KHz] or more. Therefore, when the detected leakage current Ik and the filter value IF1 are compared and the absolute value of the deviation is taken, the noise current Ikn is extracted as shown in FIG. Therefore, by detecting the presence of the noise current Ikn, it can be determined that the current flowing in the detection zone Z is the leakage current Ik due to smoldering.

  On the other hand, when severe preignition occurs, an ion current Ip flows following the noise current In as shown in FIG. When the detected ionic current Ip and the filter value IF2 are compared and the deviation is taken, the noise current is not superimposed on the ionic current Ip, so that the deviation becomes 0 as shown in FIG. Therefore, it can be determined that the current flowing in the detection zone Z is the ion current Ip due to pre-ignition.

  When the smoldering of the spark plug and severe preignition occur simultaneously, the leakage current Ik and the ionic current Ip flow in a superimposed manner, but the detected current is compared with the filter value IF to obtain the absolute value of the deviation. Thus, the noise component can be extracted as shown in FIG. 5F, and the presence of the leakage current Ik due to smoldering can be detected. Of course, the filter value in this case corresponds to the total value of the leakage current Ik and the ion current Ip.

  Next, an internal combustion engine combustion state detection apparatus according to Embodiment 2 of the present invention, which uses the internal combustion engine combustion state detection method according to Embodiment 2 described above, will be described. The overall configuration is the same as the overall configuration of the internal combustion engine combustion state detection apparatus according to Embodiment 1 shown in FIG.

  FIG. 6 is a flowchart showing the operation of the smolder detecting means 19 in the combustion state detecting device for an internal combustion engine according to the second embodiment of the present invention, and the processing routine is repeated every ignition cycle of the internal combustion engine. In FIG. 6, the operation of the detection section setting device 18 is omitted, but the operation is the same as that in the first embodiment. In FIG. 6, in step S <b> 21, the filter value IF for the current value in the detection zone Z detected by the ion current detection circuit 11 is set as a function of the detected current I. Next, the deviation between the detected current I and the filter value IF is calculated. Further, the detected current value I in the detection zone Z is added.

  In step S22, it is determined whether or not the calculated deviation is larger than the noise determination threshold value. If not larger, the process returns to step S21 and the above-described operation is repeated. Here, the noise discrimination threshold is set as shown in FIGS. As a result of the determination in step S22, if the deviation is larger than the noise determination threshold value, the process proceeds to step S23, and “1” is added to the count value of the noise counter.

  In step S24, it is determined whether or not the detected current is completed within the detection zone Z. If not completed, the process returns to step S21 to repeat the above-described operation. As a result of the determination in step S24, if the detected current ends in the detection zone Z, the process proceeds to step S25, and the integrated value of the detected current in the detection zone Z integrated in step S21 is integrated. It is determined whether or not it is larger than the threshold value. As a result of the determination, if the integrated value of the detected current is equal to or less than the integrated threshold value, it is determined that pre-ignition and smoldering have not occurred, and the process ends. This means that the smolder detecting means 19 detects the occurrence of the smolder only when it is determined that the current detected in the detection zone Z is larger than the integrated threshold value. Of course, it is possible not to detect the occurrence of smoldering only when the detected current is zero by selecting the magnitude of the integrated threshold.

  If the integrated value of the detected current is larger than the integrated threshold value as a result of the determination in step S25, the process proceeds to step S26, and whether or not the count value of the noise counter counted in step S23 is larger than the noise count threshold value. Determine. As a result of the determination, if the count value is equal to or less than the count threshold, it is determined that pre-ignition has occurred although smoldering has not occurred, and the process is terminated. As a result of the determination in step S26, if the count value is larger than the count threshold value, the process proceeds to step S27, where it is determined that smoldering and pre-ignition have occurred, and the process is terminated.

  As described above, according to the combustion state detection method and apparatus for an internal combustion engine according to the second embodiment of the present invention, smoldering can be ensured even if ion current due to pre-ignition and leakage current due to smolder are superimposed. Leakage current can be detected, and noise generated in smoldering leakage current is extracted by comparing the detection current with the filter value to detect the leakage current, so that the detection accuracy is improved. be able to.

Embodiment 3 FIG.
Next, a combustion state detection apparatus for an internal combustion engine according to Embodiment 3 of the present invention will be described. The device according to Embodiment 3 of the present invention includes dynamic range setting means for setting a dynamic range on the output side of the current detection device, and when the current detected by the current detection device is in a predetermined condition, the dynamic range is set. The range is switched.

  FIG. 7 is a circuit diagram showing a partial circuit configuration of an internal combustion engine combustion state detection apparatus according to Embodiment 3 of the present invention. In FIG. 7, the ECU 12 includes resistors 14 and 15 connected in parallel between the output side of the ion current detection circuit 11 and the input side of the A / D converter 16, and range switching connected in series to the resistor 15. Dynamic range switching means including a transistor 13 is provided. The range switching transistor 13 is conduction-controlled based on a signal from the MPU 17. Other configurations are the same as those of the combustion state detection apparatus for an internal combustion engine according to the first or second embodiment.

  Next, the operation of the combustion state detection apparatus for an internal combustion engine according to Embodiment 3 will be described. FIG. 8 is a flowchart showing the dynamic range switching operation by the dynamic range switching means. FIGS. 9A and 9B are explanatory diagrams for explaining the dynamic range switching operation. FIG. 9A shows a case where severe smoldering occurs, and FIG. 9B shows a case where mild smoldering occurs. In FIG. 8, in step S31, the maximum detected current value Ikmax detected by the ion current detection circuit 11 is stored in the memory. As shown in FIGS. 9A and 9B, the maximum detected current value Ikmax is detected mainly by the noise current In flowing at time t1 when the ignition signal is turned on. In step S31, the counter value is set to "0". The detection period in which the ion current detection circuit 11 detects current is set to the same period as the period during which the ignition signal is generated.

  Next, proceeding to step S32, the comparison threshold value Ith shown in FIG. 9 is set. The comparison threshold value Ith is set to a value that is 60% of the maximum current detection value Ikmax. In step S33, it is determined whether or not the value of the current detected by the ion current detection circuit 11 in the detection section is greater than the comparison threshold value Ikth. If the detected current value is greater than the comparison threshold value Ikth, the process proceeds to step S34. To add “1” to the count value of the counter. If the result of determination in step S33 is that the detected current value is less than or equal to the comparison threshold value Ikth, step S34 is passed and processing proceeds to step S35.

  In step S35, it is determined whether or not energization is completed within the detection section. If not, the process returns to step S33 and the above-described operation is repeated. If the result of determination in step S35 is that energization has been completed, processing proceeds to step S36, where it is determined whether or not the count value of the counter is 20% or more of the energization period within the detection interval. That is, the determination in step S36 is whether or not the period X in which the detected current exceeds the comparison threshold value Ith exceeds 20% of the energization period in the detection section as shown in FIG. Judgment. When severe smoldering has occurred as shown in FIG. 9A, the period X exceeds 20% of the energization period in the detection section, but as shown in FIG. In the case of mild smoldering, the period X is 20% or less of the energization period in the detection section.

  As a result of the determination in step S36, if the period X is 20% or less of the energization period in the detection section, the process proceeds to step S38, and the dynamic range switching of the dynamic range switching means is not performed. As a result of the determination in step S36, if the period X exceeds 20% of the energization period in the detection section, the process proceeds to step S37 and the dynamic range of the dynamic range switching means is switched. That is, in this case, the range switching transistor 13 is turned on by the switching signal from the MPU 17 and the dynamic range is switched to the lower stage by disconnecting the resistor 15.

  When the dynamic range of the dynamic range switching means is switched to the lower stage in step S37, the detection section setting device 18 and the smolder detecting means 19 perform the above-described implementation without any problem even if an excessive current occurs when a severe smolder occurs. The operation shown in mode 1 or 2 can be performed.

  In the combustion state detection apparatus for an internal combustion engine according to the third embodiment described above, the period X in which the detected current exceeds the comparison threshold Ith exceeds 20% of the energization period in the detection section. In addition, the gain is reduced by switching the dynamic range to the lower side, but the period X in which the detected current value exceeds the comparison threshold value Ith is less than a predetermined ratio with respect to the energization period in the detection period. When this state reaches a predetermined number of times, the dynamic range may be switched to the upper side to increase the gain.

Modifications of Embodiments 1 to 3 In the above-described Embodiments 1 to 3, the case where the internal combustion engine includes only one spark plug has been described. However, the internal combustion engine includes the first spark plug and the first spark plug. A current detection device configured to detect a current corresponding to the spark discharge of the second spark plug, when the second spark plug is provided with a second spark plug that generates the spark discharge later than the spark discharge of The smoldering occurrence detection described in the first to third embodiments can be performed.

1 is a circuit diagram showing a partial circuit configuration of a combustion state detection device for an internal combustion engine according to Embodiment 1 of the present invention; FIG. It is explanatory drawing explaining the combustion state detection method of the internal combustion engine which concerns on Embodiment 1 of this invention. 1 is a block diagram showing an overall configuration of a combustion state detection apparatus for an internal combustion engine according to Embodiment 1 of the present invention. It is a flowchart which shows operation | movement of the detection area setting apparatus of the combustion condition detection apparatus of the internal combustion engine which concerns on Embodiment 1 of this invention, and a smolder detection means. It is explanatory drawing explaining the combustion state detection method of the internal combustion engine which concerns on Embodiment 2 of this invention. It is a flowchart which shows operation | movement of the smoldering detection means of the combustion state detection apparatus of the internal combustion engine which concerns on Embodiment 2 of this invention. It is a circuit diagram which shows a part circuit structure of the combustion state detection apparatus of the internal combustion engine which concerns on Embodiment 3 of this invention. It is a flowchart which shows the dynamic range switching operation | movement of the combustion state detection apparatus of the internal combustion engine which concerns on Embodiment 3 of this invention. It is explanatory drawing explaining the dynamic switching operation | movement of the combustion state detection apparatus of the internal combustion engine which concerns on Embodiment 3 of this invention. It is explanatory drawing which shows the electric current waveform in case the heavy smoldering and strong preignition generate | occur | produced in the ignition plug of the internal combustion engine.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Ignition coil 2 Primary coil 3 Secondary coil 4 Transistor 5 Spark plug 7 Bias circuit 8 Zener diode 9 Capacitor 10 Diode 11 Ion current detection circuit 12 ECU
13 Range switching transistor 14, 15 Resistance 16 A / D converter 17 MPU
18 Detection interval setting device 19 Smoldering detection device 20 Noise discrimination means In noise current Ik Leakage current Ikn Noise current included in leakage current Ip Ion current IF1, IF2 Filter waveform Z Detection interval Ikmax Maximum detection current Ith Comparison threshold Th Ion generation Threshold X period

Claims (16)

  An ignition plug provided with an electrode that is installed in a combustion chamber of an internal combustion engine to generate a spark discharge in the combustion chamber by igniting an air-fuel mixture by applying an ignition voltage, and to burn the mixture, and based on generation of an ignition signal A method for detecting a combustion state in an internal combustion engine including an ignition coil for inducing the ignition voltage, and applying a voltage for generating an ionic current due to ions generated by the combustion to an electrode of the ignition plug, A current flowing through the electrode is detected in a predetermined detection section including at least a period in which the ignition signal is generated by application of the voltage, and whether or not the detected current includes a predetermined noise. A method of detecting a combustion state of an internal combustion engine, wherein the presence or absence of smoldering in the spark plug is detected by determining.   The method for detecting a combustion state of an internal combustion engine according to claim 1, wherein the determination as to whether or not the predetermined noise is included is made based on a frequency component of the detected current.   3. The internal combustion engine according to claim 2, wherein the frequency component is a frequency component in the vicinity of 10 [KHz], and when the frequency component is present, the occurrence of the smoldering is detected. Combustion state detection method.   The determination as to whether or not the noise is included is performed based on a result of comparison between a filter value obtained by performing a filtering process on the detected current and a value of the detected current. 2. A method for detecting a combustion state of an internal combustion engine according to 1.   5. The smoldering is detected when a current change of 20 [μA] or more occurs a predetermined number of times or more as a result of comparison between the detected current value and a filter value. The combustion state detection method of the internal combustion engine as described in 2.   An ignition plug provided with an electrode that is installed in a combustion chamber of an internal combustion engine to generate a spark discharge in the combustion chamber by igniting an air-fuel mixture by applying an ignition voltage, and to burn the mixture, and based on generation of an ignition signal A device for detecting a combustion state in an internal combustion engine having an ignition coil for inducing the ignition voltage, and applying a voltage for generating an ion current due to ions generated by the combustion to an electrode of the ignition plug An application device, a current detection device for detecting a current flowing through the electrode by a voltage applied by the voltage application means, and a detection interval setting for setting a predetermined detection interval including a period in which the ignition signal is generated By determining whether or not a predetermined noise is included in a current flowing in the detection section among currents detected by the device and the current detection device. Combustion state detecting system for an internal combustion engine, characterized in that a smoldering detection means for detecting the occurrence of smoldering in the spark plug.   The combustion state detecting device for an internal combustion engine according to claim 6, wherein the smolder detecting means includes a noise determining means for determining whether or not a predetermined noise is included in the current flowing in the detection section.   8. The combustion state detection method for an internal combustion engine according to claim 7, wherein the noise determination means performs the determination based on a frequency component of the detected current.   The said noise discrimination | determination means performs the said discrimination | determination based on the result of the comparison with the filter value obtained by performing the filter process to the said detected electric current, and the value of the said detected electric current. A combustion state detection method for an internal combustion engine. The predetermined detection section set by the detection section setting device is started from a time point after the elapse of a predetermined mask period from the time point when the ignition signal is generated. A combustion state detection device for an internal combustion engine as described.   The combustion state detecting device for an internal combustion engine according to any one of claims 6 to 10, wherein the smoldering detecting means includes dynamic range setting means for setting a dynamic range of the current detecting device.   Comparison threshold setting means for setting a comparison threshold; current comparison means for comparing the comparison threshold with a current value detected by the current detection device during the detection period; and Switching means for switching the dynamic range of the dynamic range setting means according to the result, the switching means is a current conduction period of the current in the detection period during which the detected current value exceeds the comparison threshold value The combustion state detecting device for an internal combustion engine according to claim 11, wherein the dynamic range is switched to a lower stage when the ratio is greater than or equal to a predetermined ratio.   Comparison threshold setting means for setting a comparison threshold; current comparison means for comparing the comparison threshold with a current value detected by the current detection device during the detection period; and Switching means for switching the dynamic range of the dynamic range setting means according to the result, the switching means energizing the current in the detection interval during which the value of the detected current exceeds the comparison threshold The combustion state detecting device for an internal combustion engine according to claim 11, wherein the dynamic range is switched to an upper stage when a predetermined number of times or less of the period reaches a predetermined number.   The combustion of the internal combustion engine according to claim 12 or 13, wherein the comparison threshold value setting means sets the comparison threshold value to a predetermined ratio of a maximum detected current value that can be detected by the current detection device. State detection device.   The smolder detecting means determines whether or not the smolder is generated only when it is determined whether or not a current is detected by the current detection device within the detection section, and the current is detected. The combustion state detection device for an internal combustion engine according to any one of claims 6 to 14.   The internal combustion engine includes a first spark plug and a second spark plug that generates a spark discharge later than a spark discharge of the first spark plug, and the current detection device includes a second spark plug. The combustion state detection device for an internal combustion engine according to any one of claims 6 to 15, wherein the current is detected corresponding to a spark discharge.

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