JP2008169718A - Ignition coil failure detecting device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent an erroneous determination of failure and normal combustion of an ignition coil such as a layer short-circuit, when determining the existence of the failure of the ignition coil based on an ion current. <P>SOLUTION: An actual engine operation area is determined based on a characteristic (for example, a generating time width of a peak current and the ion current) of the ion current detected by an ion current detecting circuit 35. An estimated engine operation area is determined based on an operation parameter (for example, an engine speed and a load) except for the ion current. When a state of determining the estimated engine operation area as a high rotation operation area based on the characteristic of the ion current, continues by a predetermined cycle or more (for example, 10 cycles or more), the existence of failure of the ignition coil 21 is determined by whether the actual engine operation area is determined as an operation area (a low rotation operation area or a fuel cut) except for the high rotation operation area based on the operation parameter except for the ion current. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an ignition coil failure detection device for an internal combustion engine having a function of detecting, through an ignition plug, an ionic current generated in accordance with combustion of an air-fuel mixture in a combustion chamber of the internal combustion engine.

  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. Techniques have been developed to detect ignition / misfire based on values. The conventional ignition / misfire determination method uses the property that the ion current increases at the time of ignition and decreases when the misfire occurs, and the detected ion current peak value is compared with a predetermined misfire determination value. If the peak value is equal to or greater than the misfire determination value, it is determined as ignition, and if not, it is determined as misfire.

  In such a misfire detection apparatus using an ionic current, if the ionic current detection circuit fails due to a disconnection or a short circuit, misfire is erroneously detected.

As a countermeasure against this, as shown in Patent Document 1 (Japanese Patent No. 2657012), when the ion current detection signal shows the same level continuously for a predetermined time, it is determined that the ion current detection circuit has failed. There is.
Japanese Patent No. 2657012

  By the way, as shown in FIG. 3, when a short circuit between the primary windings of the ignition coil occurs, a noise current having a time width of about 1 ms is generated during the ion current detection period, and the rare current between the secondary windings is generated. When a short circuit occurs, a noise current having a time width of about 1.5 ms is generated during the ion current detection period. Therefore, when an ignition coil failure such as a short circuit between windings occurs, the output level of the ion current detection signal (noise current) fluctuates in a time width of about 1 to 1.5 ms. In a system that determines a failure when the ion current detection signal is continuously maintained at the same level as in the failure detection device of Document 1, it is not possible to detect a failure of the ignition coil such as a short circuit between the windings. Or, since the output level of the ion current detection signal (noise current) at the time of occurrence of the short circuit exceeds the misfire determination level, there is a problem that the abnormal combustion due to the short circuit is erroneously determined as normal combustion.

  As a countermeasure, it is conceivable to detect a failure of the ignition coil based on the waveform of the ion current detection signal (noise current). In the high speed operation region of the internal combustion engine, the ion current generation interval (60 Since the time width of ° C A) approaches the time width of the noise current due to the layer short and it is difficult to distinguish the two, normal combustion may be erroneously determined as a failure of the ignition coil.

  The present invention has been made in view of such circumstances. Therefore, the purpose of the present invention is to determine whether there is a failure and normality of the ignition coil such as a short circuit when determining the presence or absence of the failure of the ignition coil based on the ion current. An object of the present invention is to provide an ignition coil failure detection device for an internal combustion engine that can prevent erroneous determination of combustion and improve the accuracy and reliability of ignition coil failure determination.

  In order to achieve the above object, the invention according to claim 1 is characterized in that a first operating region determining means for determining an operating region of an internal combustion engine based on characteristics of an ion current detected by an ion current detecting means, and the ion current A second operating region determining means for determining the operating region of the internal combustion engine based on an operating parameter other than the above, and a state in which the first operating region determining unit determines that the operating region is a high speed operating region based on the characteristics of the ion current Is provided with a failure detection means for determining that the ignition coil is in failure when the second operation region determination means determines that the operation region is other than the high rotation operation region based on the operation parameter other than the ion current. This is a configuration.

  Depending on the operating region of the internal combustion engine, the combustion may become unstable due to a slight difference in operating conditions or environmental conditions, resulting in a large variation in ion current or a small ion current. Also, before the completion of warm-up of the internal combustion engine, there is a large amount of adhering fuel (wet) around the intake port, so even if the fuel is cut, the adhering fuel around the intake port may continue to burn for a while. Therefore, the detection of a failure such as a short circuit between the windings of the ignition coil needs to be confirmed in an operating state in which the ionic current is stably detected.

  Therefore, the present invention determines the operation region of the internal combustion engine based on the characteristics of the ion current detected by the ion current detection means (for example, the ion current peak value, the ion current generation time, etc.) and the operation parameters other than the ion current ( For example, when the operating region of the internal combustion engine is determined based on the engine rotational speed, the load, etc., and the state determined to be the high rotational operating region based on the characteristics of the ion current continues, based on the operating parameters other than the ion current Whether or not there is a failure in the ignition coil is determined based on whether or not it is determined as an operation region (low rotation operation region or fuel cut) other than the high rotation operation region.

  In short, even in the case of a failure of an ignition coil such as a short circuit, the determination result of the operation region based on the ion current characteristic is a high rotation operation region, but the determination result of the operation region based on the ion current characteristic and the ion current other than If the determination result of the operation region based on the operation parameter of both is the high rotation operation region, it is determined that the combustion is normal, and the determination result of the operation region based on the operation parameter other than the ion current is an operation region other than the high rotation operation region ( If it is a low rotation operation region or a fuel cut), it is determined that the ignition coil has failed. In this way, it is possible to prevent erroneous determination of ignition coil failure and normal combustion, such as a short circuit, and to improve the accuracy and reliability of ignition coil failure determination.

  According to a second aspect of the present invention, the first operating region determining means for determining the operating region of the internal combustion engine for each cylinder based on the characteristics of the ion current of each cylinder detected by the ion current detecting means, and the first When the operation region determination result of each cylinder by the operation region determination means is compared and all the other cylinders except for one of the cylinders are determined to be operation regions other than the high rotation operation region, the one cylinder is at a high rotation speed. A failure detection unit that determines that the ignition coil of one cylinder has failed when it is determined as the operation region may be provided. In short, since the failure of the ignition coil occurs almost only in any one of the cylinders, the other cylinders except for any one of the cylinders are all determined to be in the operation region other than the high-speed operation region (that is, When it is determined that the one cylinder is in the high rotation operation region when the actual operation region is determined as the low rotation operation region or the fuel cut), it is determined that the ignition coil of the one cylinder has failed. Even in this case, it is possible to prevent erroneous determination of failure and normal combustion of the ignition coil such as a rare short, and the accuracy and reliability of failure determination of the ignition coil can be improved.

  Further, in the invention according to claim 2, as in claim 3, there is provided second operation region determination means for determining an operation region of the internal combustion engine based on an operation parameter other than the ion current. When the operation region determination result of each cylinder by the operation region determination means is compared and all the other cylinders except for one of the cylinders are determined to be operation regions other than the high rotation operation region, the first operation region determination Means that the one cylinder is determined to be in the high-speed operation region and the operation region of the other cylinder matches the operation region determination result by the second operation region determination means, It may be determined (in short, it may be a combination of claim 1 and claim 2). In this way, it is possible to more reliably prevent erroneous determination of failure and normal combustion of the ignition coil such as a short circuit, and the accuracy and reliability of failure determination of the ignition coil can be further improved.

  Further, according to a fourth aspect of the present invention, the first operation region determination means determines the operation region of the internal combustion engine as a fuel cut region, a low rotation operation region, and a high rotation operation region based on the characteristics of the ion current for each cylinder. And the failure detection means determines that the operation area of any cylinder is determined to be an unspecified operation area by the first operation area determination means. In addition, failure determination of the ignition coil may be prohibited. In this way, when the operation region of any cylinder is an unspecified operation region that may erroneously determine failure of the ignition coil and normal combustion, the failure determination of the ignition coil is prohibited. It is possible to prevent erroneous determination more reliably.

  Further, as in claim 5, the first operation region determination means validates the operation region determination result when the operation region determination result is the same continuously for a predetermined cycle or more, and otherwise does not. You may make it determine with a specific driving | operation area | region. In this way, the accuracy and reliability of the ignition coil failure determination can be further improved.

  According to a sixth aspect of the present invention, the failure detection unit may prohibit failure determination of the ignition coil when the ion current output waveform of the ion current detection unit is an abnormal waveform. In short, if the ion current output waveform of the ion current detection means is an abnormal waveform, misfires, smoldering contamination of the ignition plug, failure of the ion current detection means, etc. are considered. The determination can be prevented in advance.

  Further, in consideration of the fact that misfire occurs when the ignition coil breaks down, as in claim 7, comprising misfire detection means for detecting misfire for each cylinder based on operating parameters other than the ion current, The failure detection means permits the failure determination of the ignition coil of the cylinder for the cylinder for which the misfire detection is detected by the misfire detection means, and for the cylinder for which the misfire is not detected by the misfire detection means, It is good also as a structure provided with the means to prohibit failure determination. In this way, it can be confirmed whether or not the cause of the misfire is a failure of the ignition coil, so that the failed part can be identified and the repair workability at the maintenance shop can be improved.

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.
An ignition coil 21 is provided for each cylinder of the engine, one end of the primary side winding 22 of the ignition coil 21 of each cylinder is connected to the battery 23, and the other end of the primary side winding 22 is built in the igniter 24. The power transistor 25 is connected to the collector. 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 engine 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. The ion current detection circuit 35 is provided for each cylinder, and the ion current is detected for each cylinder.

  During engine operation, the power transistor 25 is turned on / off at the rise / fall of the ignition command signal transmitted from the engine control circuit 34 to the igniter 24. When the power transistor 25 is turned on, a primary current flows from the battery 23 to the primary 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 corresponding to the ionic current is output to the engine control circuit 34 from the output terminal of the inverting amplifier circuit 33. Is output. An ionic current is detected from the output voltage V of the inverting amplifier circuit 33, and misfire, preignition, knocking, etc. are detected from the ionic current.

  Next, what is the ion current output pattern of the ion current detection circuit 35 at the time of misfire, mild smoldering contamination, failure of the ion current detection circuit 35 (when the ion current cannot be detected), and when the ignition coil 21 is short-circuited? 2 will be described with reference to FIG. Here, the rare short of the ignition coil 21 is a failure mode in which a line between the primary side windings 22 (or a line between the secondary side windings 26) is short-circuited as shown in 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 is generated by the residual magnetic energy on the secondary side of the ignition coil 21, and then the waveform of the ion current generated by combustion appears.

  Even if smoldering contamination occurs, if the degree of smoldering contamination is mild, the air-fuel mixture is ignited, so the time width of the noise current induced immediately after the start of energization to the primary side winding 22 is increased, After ignition, the LC resonance noise and the waveform of the ion current due to combustion appear as in normal ignition.

  On the other hand, at the time of misfire, a pulsed noise current immediately after the start of energization of the primary winding 22 and LC resonance noise after ignition appear, but the waveform of the ion current due to combustion does not appear.

  Further, when the ion current becomes undetectable due to a failure of the ion current detection circuit 35 (broken signal line, etc.) (or when the energization becomes impossible due to breakage of the primary side winding 22 of the ignition coil 21). The ion current signal of the ion current detection circuit 35 is not output at all, and not only the ion current due to combustion but also the noise immediately after switching the ignition signal ON and the LC resonance noise are not detected.

  Focusing on this point, in the present embodiment, whether or not there is an ionic current output (noise current) during the energization period of the ignition coil 21 (during the ignition signal ON period) is the time of the ionic current output exceeding the coil energization determination level Vth1. It is determined based on the width, and whether or not the ion current detection circuit 35 is faulty (or the ignition coil 21 cannot be energized) is determined based on whether or not the ion current output time width is equal to or shorter than a predetermined time. In addition, when the ion current detection circuit 35 fails (or when the ignition coil 21 cannot be energized), LC resonance noise does not occur, so by determining the presence or absence of ion current output due to the LC resonance noise after ignition, It may be determined whether or not the ion current detection circuit 35 has a failure (or the ignition coil 21 cannot be energized).

  Further, when a short circuit of the primary side winding 22 of the ignition coil 21 occurred, a noise current having a time width Ti of about 1 ms was generated during the ion current detection period, and a short circuit of the secondary side winding 26 occurred. Sometimes, a noise current having a time width Ti of about 1.5 ms is generated during the ion current detection period. Since this noise current is larger than the misfire determination level Vth2, conventionally, this noise current may be erroneously determined as an ionic current due to combustion.

  With respect to the failure mode of the ignition coil 21 as described above, the engine control circuit 34 executes an ignition coil failure diagnosis routine of FIGS. 4 and 5 to be described later, whereby the failure of the ignition coil 21 is performed in the following manner. The presence or absence of is determined.

  Although it is conceivable to detect a failure of the ignition coil 21 based on the waveform of the ion current detection signal (noise current), in the high speed operation region of the engine, the ion current generation interval (60 ° C. A) during normal combustion is considered. Since the time width approaches the time width Ti of the noise current at the time of failure of the ignition coil 21 and it becomes difficult to distinguish the two, normal combustion may be erroneously determined as a failure of the ignition coil 21. In addition, depending on the engine operating region, a slight unstable operating condition or environmental condition may result in an unstable combustion state, resulting in a large variation in ion current or a small ion current. In addition, before the engine is warmed up, there is a large amount of fuel adhering around the intake port (wet), so even if the fuel is cut, the fuel adhering around the intake port may continue to burn for a while. Therefore, the detection of the failure of the ignition coil 21 needs to be confirmed in an operating state in which the ion current is stably detected.

  Therefore, in this embodiment, the actual engine operation region is determined based on the characteristics of the ion current detected by the ion current detection circuit 35 (for example, the peak current Ip and the ion current generation time width Ti), and the operation other than the ion current is performed. An estimated engine operation region is determined based on parameters (for example, engine speed, load, etc.), and a state in which the estimated engine operation region is determined to be a high rotation operation region based on ion current characteristics is greater than or equal to a predetermined cycle (for example, 10 cycles). In the case where the above is continued, based on the operation parameter other than the ion current, whether or not the actual engine operation region is determined to be an operation region other than the high rotation operation region (low rotation operation region or fuel cut) is determined. The presence or absence of a failure is determined.

  In short, even in the case of a failure of the ignition coil 21 such as a short circuit, the operation region determination result (estimated engine operation region) based on the ion current characteristics is a high rotation operation region, but the operation region based on the ion current characteristics is If both the determination result and the operation region determination result (actual engine operation region) based on the operation parameters other than the ion current are both in the high rotation operation region, it is determined that the combustion is normal and the operation is based on the operation parameters other than the ion current. If the determination result of the region is an operation region other than the high rotation operation region (low rotation operation region or fuel cut), it is determined that the ignition coil 21 has failed. In this way, it is possible to prevent erroneous determination of failure and normal combustion of the ignition coil 21 such as a rare short, and the accuracy and reliability of failure determination of the ignition coil 21 can be improved.

  Further, in the present embodiment, the estimated engine operation region is determined for each cylinder based on the characteristics of the ion current of each cylinder detected by the ion current detection circuit 35, and the estimated engine operation region of each cylinder is compared to either When all other cylinders except for one cylinder are determined to be operating regions other than the high-speed operation region, the one cylinder is determined to be the high-speed operation region, and the estimated engine operation region of the other cylinder is other than the ion current It is determined that the ignition coil 21 of the one cylinder is out of order when it matches the actual engine operating range determined from the operating parameters.

  Further, in the present embodiment, considering that a misfire occurs when the ignition coil 21 fails, misfire is detected for each cylinder based on operating parameters other than the ionic current (for example, engine rotation fluctuation), and misfire is detected. For the detected cylinder, failure determination of the ignition coil 21 of the cylinder is permitted, and for the cylinder where misfire is not detected, failure determination of the ignition coil 21 of the cylinder is prohibited. In this way, it can be confirmed whether or not the cause of the misfire is a failure of the ignition coil 21, so that the failed part can be identified and the repair workability at the maintenance shop can be improved.

  The failure diagnosis of the ignition coil 21 described above is executed by the engine control circuit 34 according to the ignition coil failure diagnosis routine of FIGS. 4 and 5. Hereinafter, the processing content of this ignition coil failure diagnosis routine will be described. The ignition coil failure diagnosis routine shown in FIGS. 4 and 5 is started every time each cylinder is ignited (every time the ionic current detection period of each cylinder is finished), and serves as a failure detection means in the claims.

  When this routine is started, first, in step 101, a misfire determination routine (not shown) based on engine rotation fluctuation is executed, and misfire is detected for each cylinder #n based on engine rotation fluctuation. Instead of engine rotation fluctuation, misfire may be detected for each cylinder #n based on, for example, in-cylinder pressure (combustion pressure). In short, each cylinder # is based on operating parameters other than ion current. A misfire may be detected every n. The processing in step 101 serves as misfire detection means in the claims.

  Thereafter, the process proceeds to step 102, and the ion current output of the ion current detection circuit 35 of each cylinder #n is read. In the next step 103, the ion current peak value Ip of each cylinder #n is compared with the misfire determination value Vth2. In addition to determining misfire / combustion, the insulation resistance value of the spark plug 27 is calculated based on the leakage current (output current of the ion current detection circuit 35) flowing during a period other than the ion current detection period to determine the presence or absence of smoldering contamination. .

  Then, in the next step 104, referring to the actual engine operation region determination map of FIG. 6, the actual engine operation region Mex is determined as a fuel cut based on operation parameters other than ion current (for example, engine speed and load factor). It is determined which of the region Me1, the low rotation operation region Mex2, and the other operation region Mex0 is applicable. The processing in step 104 serves as a second operation region determination means in the claims.

  Thereafter, in step 105, it is determined whether failure diagnosis of the ignition coil 21 is permitted. Here, the conditions under which the failure diagnosis of the ignition coil 21 is permitted are, for example, that no smoldering contamination of the ignition plug 27 has occurred, and that the system related to the failure diagnosis of the ignition coil 21 is operating normally ( No abnormality is detected).

  If the failure diagnosis of the ignition coil 21 is permitted, the process proceeds to step 106, and the characteristics of the ion current of each cylinder #n (for example, the ion current before gain adjustment) are referred to with reference to the estimated engine operation region determination map of FIG. Based on the peak value Ip, ion current generation time Ti, etc., the estimated engine operation region Mix [#n] cannot be specified in any of the fuel cut region Mi1, the low rotation operation region Mix2, and the high rotation operation region Mix3. Which of the regions Mi0 corresponds is determined for each cylinder #n and stored in the memory of the engine control circuit 34. The processing in step 106 serves as a first operation region determination means in the claims.

  Thereafter, the routine proceeds to step 107, where it is determined for each cylinder #n whether or not the current determination result of the estimated engine operation region Mix [#n] based on the ionic current characteristics of each cylinder #n is the same as the previous time. If it is the same as the previous time, the routine proceeds to step 108 where the continuous determination number counter N [#n] for each cylinder #n is incremented by one, and in the next step 110, the number of continuous determinations for each cylinder #n. It is determined whether or not the count value of the counter N [#n] exceeds a predetermined value (for example, 10). On the other hand, if there is a cylinder in which the current determination result of the estimated engine operation region Mix [#n] is different from the previous one, the process proceeds to step 109, and the continuous determination number counter N [#n] of the cylinder is reset to zero.

  Until the count value of the continuous determination number counter N [#n] of each cylinder #n exceeds a predetermined value (for example, 10), the process proceeds to step 112 to determine the estimated engine operation area Mix [#n] of each cylinder #n. The result is an unspecified operation area Mi0. Thereafter, when the count value of the continuous determination number counter N [#n] of each cylinder #n exceeds a predetermined value (for example, 10), the process proceeds to step 111 and the estimated engine of each cylinder #n determined in step 106 is determined. The determination result of the operation region Mix [#n] is fixed as the final determination result.

  If it is determined in step 105 that the failure diagnosis of the ignition coil 21 is prohibited, the process proceeds to step 109, and after resetting the continuous determination number counter N [#n] of the cylinder to 0, step 112 is performed. Then, the determination result of the estimated engine operation region Mix [#n] of each cylinder #n is set as an unspecified operation region Mi0.

  On the other hand, when the determination result of the estimated engine operation region Mix [#n] of each cylinder #n is confirmed in step 111, the process proceeds to step 113 in FIG. 5 and the determination of the estimated engine operation region Mix [#n] is performed for all cylinders. It is determined whether or not it has been completed, and if there is a cylinder for which the estimation engine operation region Mix [#n] has not yet been determined, this routine is immediately ended.

  If the determination of the estimated engine operation region Mix [#n] has been completed for all cylinders, the process proceeds to step 114, where the estimated engine operation region Mix [#n] of any one cylinder is the estimated engine operation region of the other cylinders. It is determined whether or not there is a mismatch with Mix [#n]. If there is no mismatching cylinder, it is determined that a failure such as a short-circuit of the ignition coil 21 has not occurred, and this routine is terminated as it is.

  On the other hand, if the estimated engine operation region Mix [#n] of any one cylinder does not match the estimated engine operation region Mix [#n] of the other cylinders, the process proceeds to step 115 to estimate the mismatched cylinder. It is determined whether or not the engine operation region Mix [#n] is the high rotation operation region Mix3. If the engine operation region Mix [#n] is not the high rotation operation region Mix3, it is determined that a failure such as a short circuit of the ignition coil 21 has not occurred. This routine is finished as it is.

  If the estimated engine operation region Mix [#n] of the mismatched cylinder is the high speed operation region Mix3, the process proceeds to step 116, and the estimated engine operation region Mix [#n] of the other cylinders is actually determined in step 104. It is determined whether or not the engine operating range Mex of the other cylinders matches, and if the estimated engine operating range Mix [#n] of the other cylinders does not match the actual engine operating range Mex, an accurate failure diagnosis is performed. It is determined that the state is difficult and unstable, and this routine is finished as it is.

  On the other hand, if the estimated engine operation region Mix [#n] of the other cylinders matches the actual engine operation region Mex, the process proceeds to step 117, and the cylinders determined to be inconsistent in step 114 are determined in step 101. It is determined whether or not misfire has been detected from engine rotation fluctuations. If no misfire has been detected, it is determined that a failure such as a short-circuit of the ignition coil 21 has not occurred, and this routine is immediately terminated.

  If it is determined in step 117 that misfire has been detected from fluctuations in the engine speed with respect to the mismatched cylinder, the routine proceeds to step 118, where it is determined that the ignition coil 21 of the mismatched cylinder has failed and this routine is terminated. To do.

  According to the present embodiment described above, the estimated engine operation region Mix [#n] is determined for each cylinder #n based on the characteristics of the ion current of each cylinder #n detected by the ion current detection circuit 35, When the estimated engine operation region Mix [#n] of the cylinder #n is compared and all other cylinders except for one of the cylinders are determined to be operation regions other than the high-speed operation region Mix3, the one cylinder is Ignition of the one cylinder when it is determined as the high rotation operation region Mix3 and the estimated engine operation region Mix [#n] of the other cylinders matches the actual engine operation region Mex determined from the operation parameters other than the ionic current. Since the failure of the coil 21 is determined, it is possible to prevent erroneous determination of failure of the ignition coil 21 such as a short circuit and normal combustion. It is possible to improve the degree and reliability.

  In addition, in the present embodiment, in consideration of the fact that misfire occurs when the ignition coil 21 fails, misfire is detected for each cylinder based on operating parameters other than ionic current (for example, engine rotation fluctuation). Since the failure determination of the ignition coil 21 of the cylinder concerned is permitted only with respect to the detected cylinder, it can be confirmed whether or not the cause of the misfire is the failure of the ignition coil 21, and repair workability at a maintenance shop can be improved. There is an advantage that can be improved.

  The present invention may omit the function of detecting misfire for each cylinder based on operating parameters other than ion current.

  Further, in this embodiment, the S-DLI ignition system configuration in which the ignition coil 21 is provided for each cylinder is adopted, but the D-DLI ignition system configuration in which ignition is performed on two cylinders by one ignition coil is employed. You may do it. In this case, the estimated engine operating region is determined based on the characteristics of the ionic current (for example, the peak value of the ionic current and the generation time of the ionic current), and based on the operating parameters other than the ionic current (for example, the engine speed, the load, etc.). When the actual engine operation region is determined and the state where the estimated engine operation region is determined to be the high rotation operation region based on the characteristics of the ion current continues, the actual engine operation region is determined based on the operation parameters other than the ion current. What is necessary is just to determine the presence or absence of the failure of an ignition coil by determining whether it is determined to be an operation region (low rotation operation region or fuel cut) other than the high rotation operation region.

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 ionic current output pattern of the ionic current detection circuit changes at the time of misfire, smoldering contamination, and a rare short of the ignition coil. It is an equivalent circuit diagram explaining a layer short between primary windings of an ignition coil. It is a flowchart explaining the flow of a process of an ignition coil failure diagnosis routine (the 1). It is a flowchart explaining the flow of a process of an ignition coil failure diagnosis routine (the 2). It is a figure which shows notionally an example of the actual engine operation area | region determination map used when determining an actual engine operation area | region based on an engine speed and a load factor. It is a figure which shows notionally an example of the estimation engine operation area | region determination map used when determining an estimation engine operation area | region based on the characteristic of an ionic current.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 21 ... Ignition coil, 22 ... Primary coil, 23 ... Battery, 24 ... Igniter, 25 ... Power transistor, 26 ... Secondary coil, 27 ... Spark plug, 31 ... Ion current detection resistor, 33 ... Inversion amplification circuit, 34 ... Engine Control circuit (failure detection means, first operation region determination means, second operation region determination means, misfire detection means), 35 ... ion current detection circuit (ion current detection means), 36 ... center electrode, 37 ... ground electrode

Claims (7)

In an ignition coil failure detection apparatus for an internal combustion engine, comprising an ion current detection means for detecting an ion current generated along with combustion of an air-fuel mixture in a combustion chamber of the internal combustion engine via an ignition plug,
First operating region determining means for determining the operating region of the internal combustion engine based on the characteristics of the ion current detected by the ion current detecting unit;
Second operating region determining means for determining an operating region of the internal combustion engine based on an operating parameter other than the ion current;
When the first operation region determination unit continues to be determined as the high rotation operation region based on the characteristics of the ion current, the second operation region determination unit determines whether the second operation region determination unit is based on operation parameters other than the ion current. An ignition coil failure detection apparatus for an internal combustion engine, comprising: failure detection means for determining that an ignition coil has failed when it is determined that the operation region is other than the high-speed operation region. In an ignition coil failure detection device for an internal combustion engine, comprising an ion current detection means for detecting an ionic current generated by combustion of an air-fuel mixture in a combustion chamber of a plurality of cylinders of the internal combustion engine via an ignition plug for each cylinder.
First operating region determining means for determining the operating region of the internal combustion engine for each cylinder based on the characteristics of the ionic current of each cylinder detected by the ion current detecting unit;
When one of the cylinders except for one of the cylinders is determined to be an operating region other than the high-speed operating region by comparing the operating region determination results of each cylinder by the first operating region determining means, the one cylinder An ignition coil failure detection apparatus for an internal combustion engine, comprising: failure detection means for determining that a failure of the ignition coil of the one cylinder occurs when it is determined that the engine is in a high rotation operation region. A second operating region determining means for determining an operating region of the internal combustion engine based on an operating parameter other than the ion current;
The failure detection unit compares the operation region determination result of each cylinder by the first operation region determination unit, and determines that all other cylinders except for one of the cylinders are operation regions other than the high speed operation region. The first operating region determining means determines that the one cylinder is in the high rotation operating region and the operating region of the other cylinders matches the operating region determination result by the second operating region determining unit. 3. The ignition coil failure detection device for an internal combustion engine according to claim 2, wherein the failure is determined to be a failure of the ignition coil of the one cylinder. The first operation region determination means is an unspecified operation in which the operation region of the internal combustion engine cannot be specified as any one of a fuel cut region, a low rotation operation region, and a high rotation operation region based on the characteristics of the ion current for each cylinder. Judge by dividing into areas,
The failure detection means includes means for prohibiting the failure determination of the ignition coil when the operation range of any cylinder is determined to be an unspecified operation range by the first operation range determination unit. 4. The ignition coil failure detection device for an internal combustion engine according to claim 2, wherein the ignition coil failure detection device is an internal combustion engine.   The first operation region determination means makes the operation region determination result valid when the operation region determination result is the same continuously for a predetermined cycle or more, and determines otherwise as an unspecified operation region. The ignition coil failure detection device for an internal combustion engine according to claim 4.   6. The failure detection means includes means for prohibiting the failure determination of the ignition coil when the ion current output waveform of the ion current detection means is an abnormal waveform. An ignition coil failure detection apparatus for an internal combustion engine according to the description. Comprising misfire detection means for detecting misfire for each cylinder based on operating parameters other than the ion current;
The failure detection means permits the failure determination of the ignition coil of the cylinder for the cylinder where the misfire is detected by the misfire detection means, and the ignition coil of the cylinder for the cylinder where the misfire is not detected by the misfire detection means 6. The ignition coil failure detection device for an internal combustion engine according to claim 2, further comprising means for prohibiting the failure determination.

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