JP2010090882A - Control device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent failure owing to an on-flying-spark abnormal state by accurately detecting an abnormal state of an on-flying-spark (a phenomenon of spark flying at an ignition plug in an initial period of applying electricity to an ignition coil). <P>SOLUTION: In a specific operation area other than both of a safe flying spark area where the on-flying-spark occurs when an ignition system is normal and an abnormal flying spark area where the on-flying-spark occurs when the ignition system is abnormal, a carbon fouling state of the ignition plug is determined based on an ion current signal and an on-flying-spark detection permission state is determined when the carbon fouling state is a predetermined value or lower. When it is determined as the on-flying-spark detection permission state, existence/non-existence of on-flying-spark is determined based on the ion current signal in the abnormal flying spark area and when detection frequency of the on-flying-spark is a predetermined value or higher, it is determined as an on-flying-spark abnormal state. In the case that it is determined as the on-flying-spark abnormal state, a diagnostic determination of an on-flying-spark fault is executed and fail-safe processing (for example, fuel cut) is conducted in a predetermined fail-safe operation area. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a control device for an internal combustion engine having a function of detecting, through an electrode of a spark plug, an ionic current generated with combustion of an air-fuel mixture in a combustion chamber of the internal combustion engine.

  In recent years, focusing on the characteristic that ion current is generated in the combustion chamber of each cylinder of an internal combustion engine with combustion of the air-fuel mixture, the ion current generated in the combustion chamber of each cylinder for each ignition is passed through the electrode of the ignition plug. A technique for detecting and detecting the combustion state of an internal combustion engine based on the ion current signal has been developed.

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

Therefore, as described in Patent Document 1 (Japanese Patent Application Laid-Open No. 11-13520), when the smoldering state of the spark plug proceeds, the time width of the leakage current flowing in the initial period of the energization period of the ignition coil increases. Attention is paid to the presence or absence of smoldering of the spark plug based on the ion current signal (leakage current) detected by the ion current detection circuit in the initial period of energization of the ignition coil.
Japanese Patent Laid-Open No. 11-13520

  In recent years, in an internal combustion engine mounted on a vehicle, in order to meet the demands for higher rotation, higher compression ratio, improved response, etc., the performance of the ignition coil has been increased or the gap between the electrodes of the spark plug has been reduced. Some have improved the ignition performance. In such an internal combustion engine, for example, a phenomenon in which a spark is ignited by an ignition plug (hereinafter referred to as “on spark”) may occur due to the energization voltage of the ignition coil in the initial stage of the energization period of the ignition coil in a high rotation / low load region. When the ignition system is abnormal (for example, when the ignition coil is faulty or when a different type of plug is installed), the operating range in which on-fire is generated is expanded and is wider than the operating range in which on-fire is generated when the ignition system is normal. There may be an on-firing abnormal state where on-firing frequently occurs in the operating area. In such an on-firing abnormal state, depending on the operation region, pre-ignition (pre-ignition) occurs due to on-firing when the battery voltage rises due to a failure of the regulator that adjusts the battery voltage, etc., which may damage the internal combustion engine. Since a secondary failure may occur, it is necessary to accurately detect the on-firing abnormal state and prevent a malfunction due to the on-firing abnormal state.

However, the conventional technology cannot accurately detect the on-firing abnormal state for the following reason.
As shown in FIG. 2, when an on-fire occurs, the time width of the ion current signal detected by the ion current detection circuit at the initial stage of the energization period of the ignition coil becomes longer. It is conceivable to determine whether or not there is an on-firing based on the ion current signal detected by the ion current detection circuit in the initial stage of the energization period of the ignition coil. However, as shown in FIG. 3, when the smoldering state of the spark plug progresses, the ion current detected by the ion current detection circuit at the beginning of the ignition coil energization period is the same as in the case where the on-fire occurs. Since the time width of the signal becomes longer, the ignition plug smoldering state can be determined simply by determining whether or not there is an on-firing based on the time width of the ion current signal detected by the ion current detection circuit at the beginning of the ignition coil energization period. When it progresses, there is a possibility of erroneously determining that an on-fire has occurred.

  The present invention has been made in consideration of these circumstances. Therefore, the object of the present invention is to detect an on-firing abnormal state with high accuracy and to prevent a malfunction due to the on-firing abnormal state. It is to provide an engine control device.

  In order to achieve the above object, an invention according to claim 1 is directed to an ionic current detecting means for detecting an ionic current generated by combustion of an air-fuel mixture in a combustion chamber of an internal combustion engine through an electrode of a spark plug; An on-fire detection means for detecting a phenomenon (hereinafter referred to as “on-on-fire”) that causes a spark plug to ignite with an ignition voltage based on an ionic current signal detected by the ionic current detection means at the initial stage of the energization period of the coil; Specific set in the operation region other than the operation region of both the safety spark region where the on-ignition occurs when the ignition system is normal and the abnormal spark region where the on-firing occurs when the ignition system is abnormal An on-fire detection detection determination unit that determines whether or not the predetermined on-fire detection detection enabled state is in the operation region; When the on-firing detection means detects an on-firing fire in the abnormal scorching region, the on-firing abnormality state determining means determines that the on-firing abnormality state is present, and the on-firing abnormality state determining means indicates the on-firing abnormality state. And a diagnostic means for performing diagnostic determination of an on-fire failure when it is determined.

  The present invention pays attention to the characteristic that the time width of the ion current signal detected by the ion current detection circuit at the beginning of the ignition coil energization period becomes longer at the beginning of the ignition coil energization period when an on-fire occurs. On-fire is detected based on the ion current signal detected by the ion current detection circuit.

  Here, the specific operation region set in the operation region other than the operation region of both the safe sparking region and the abnormal sparking region is an operation region in which the on-firing hardly occurs. Without being affected, it is possible to accurately determine whether or not an ionic current signal change (for example, an ionic current signal change due to the progress of the smoldering state of the spark plug) that causes an on-fire to be erroneously detected occurs. As a result, if it is determined that it is not a state in which an ionic current signal change that causes false detection of on-firing occurs, it is determined that the on-firing can be accurately detected based on the ionic current signal, It can be determined that the on-fire detection detection is permitted.

  When it is determined that the on-fire detection detection is permitted, and an on-fire is detected in the abnormal ignition region (the operation region where on-ignition occurs when the ignition system is abnormal), By determining, it is possible to accurately detect the on-firing abnormal state. In addition, when it is determined that the on-fire condition is abnormal, it is possible to prompt the repair of the failure of the ignition system by making a diagnosis of an on-fire condition and warning the driver with a warning lamp or the like. System failures can be repaired at an early stage to prevent problems due to on-fire abnormal conditions.

  Further, in the invention according to claim 2, when it is determined that the on-firing abnormality state determination means determines that the on-firing abnormality state is present, abnormal combustion is performed in a fail-safe operation region having a predetermined load or more including at least a part of the abnormal ignition region. In this configuration, fail-safe control means for executing the fail-safe process to be prevented is provided. In this configuration, when it is determined that the on-firing fire abnormal state is detected, in a fail-safe operation area (high load operation area in which pre-ignition is likely to occur due to on-firing) that includes at least a part of the abnormal scorching area. By executing the fail-safe process for preventing abnormal combustion, it is possible to prevent pre-ignition due to on-fire, and it is possible to prevent secondary failure leading to damage to the internal combustion engine due to pre-ignition due to on-fire.

  The specific determination method of the on-fire detection permission state includes smolder detection means for detecting the smoldering state of the spark plug based on the ion current signal detected by the ion current detection means as in claim 3, The permission determination means may be determined to be in the on-fire detection detection permission state when the smoldering state of the spark plug detected by the smolder detection means is not more than a predetermined value in the specific operation region.

  When the smoldering state of the spark plug progresses, the time width of the ion current signal detected by the ion current detection circuit at the beginning of the ignition coil energization period becomes longer, as in the case where the on spark is generated. An ionic current signal change that causes false detection occurs, but when the smoldering state of the spark plug is less than a predetermined value, an ionic current signal change that causes false detection of on spark is not generated, so on spark It can be determined that the detection is permitted. Thereby, when the smoldering state of the spark plug has progressed, it can be reliably prevented that it is erroneously determined that an on-fire has occurred.

  Further, as in claim 4, when the ion current detection system is in a failure state, the detection of on-fire by the on-fire detection means may be prohibited by the prohibit means. In this way, it is possible to prevent erroneous detection of on-fire due to failure of the ion current detection system, and it is possible to prevent erroneous diagnosis and erroneous fail-safe processing due to erroneous detection of on-fire.

  The specific determination method of the on-firing abnormal state is the on-firing abnormal state when the detection frequency of on-firing is equal to or higher than a predetermined value or when the number of on-firing continuous detections is equal to or higher than a predetermined value. May be determined. If the on-fire detection frequency and the number of continuous detections increase, there is a higher possibility of secondary failures leading to damage to the internal combustion engine due to pre-ignition due to on-fire, so if the on-fire detection frequency is greater than or equal to a predetermined value, If it is determined that there is an on-firing abnormality when the number of consecutive on-firing detections is greater than or equal to the specified value, the on-firing abnormality will definitely occur before the secondary failure that leads to damage to the internal combustion engine due to pre-ignition due to on-firing. The state can be detected.

  Further, as in claim 6, when it is determined that the on-fire condition is abnormal, if the battery voltage is abnormal, the diagnosis of on-fire condition is prohibited and the diagnosis of the battery voltage failure is performed. good. In this way, when an on-fire condition is abnormal due to an abnormality in the battery voltage, a diagnosis of a battery voltage failure can be made in distinction from an on-fire condition due to an abnormality in the ignition system. There is an advantage that it becomes easy to specify the failure part from the diagnosis determination result.

  Further, as in claim 7, when it is determined that the on-fire is abnormal, the fail-safe process for performing fuel cut in the fail-safe operation region is executed, and then it is determined that the on-fire is not abnormal Alternatively, the fail-safe process may be canceled. Alternatively, the fail-safe process for limiting the throttle opening to a predetermined value or less is continued until the operation of the internal combustion engine is stopped when it is determined that the on-firing abnormal state is detected. Also good. In either case, while preventing a decrease in the operating performance of the internal combustion engine to a minimum, prevent pre-ignition due to on-fire, and prevent secondary failures leading to internal combustion engine damage due to pre-ignition due to on-fire. Can do.

  Further, as in claim 9, it is determined whether or not each cylinder is in an on-firing abnormality state, and when there is a cylinder determined to be in an on-firing abnormality state, when the battery voltage is normal, the on-firing abnormality is detected. The fail safe process may be executed for the cylinders determined to be in a state, and the fail safe process may be executed for all cylinders when the battery voltage is abnormal. In this way, if there is a cylinder that is determined to be in an on-firing abnormality state and the battery voltage is normal, it is determined that there is a low possibility of an on-firing abnormality state in another cylinder, and an on-firing abnormality is detected. The fail-safe process is executed only for the cylinders determined to be in the state, and when the battery voltage is abnormal, it is determined that there is a high possibility that all cylinders will be in an on-fire condition and the fail-safe process is executed for all cylinders. The fail-safe process can be executed as necessary.

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

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

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

  During engine operation, the power transistor 25 is turned on / off at the rise / fall of the ignition signal transmitted from the engine control microcomputer 41 to the igniter 24. When the power transistor 25 is turned on, a primary current flows from the battery 23 to the primary coil 22. After that, when the power transistor 25 is turned off, the primary current of the primary coil 22 is cut off and a high voltage is electromagnetically induced in the secondary coil 26. This high voltage causes spark discharge between the electrodes 36 and 37 of the spark plug 27. This spark discharge current flows from the ground electrode 37 of the spark plug 27 to the center electrode 36, is charged to the capacitor 30 via the secondary coil 26, and flows to the ground side via the Zener diodes 28 and 29. After the capacitor 30 is charged, the ion current detection circuit 35 is driven using the charging voltage of the capacitor 30 regulated by the Zener voltage of the Zener diode 28 as a power source, and the ion current is detected as described later.

  On the other hand, the ion current flows in the opposite direction to the spark discharge current. In other words, after ignition is finished, a voltage is applied between the electrodes 36 and 37 of the spark plug 27 by the charging voltage of the capacitor 30, so that ions generated when the air-fuel mixture burns in the cylinder are connected between the electrodes 36 and 37. Although an ionic current flows, the ionic current flows from the center electrode 36 to the ground electrode 37, and further flows from the ground side through the ion current detection resistor 31 to the capacitor 30. At this time, the input potential Vin of the inverting amplifier circuit 33 changes according to the change of the ionic current flowing through the ion current detection resistor 31, and the ionic current signal of the voltage V corresponding to the ionic current is ionized from the output terminal of the inverting amplifier circuit 33. The current signal processing circuit 37 performs A / D conversion and takes in the engine control microcomputer 41.

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

  As shown in FIG. 2, for example, in the high engine speed / low load region, for example, a phenomenon in which the spark plug 27 ignites by the energizing voltage of the ignition coil 21 at the beginning of the energizing period of the ignition coil 21 (the period of ignition signal ON) (hereinafter “ When the on-fire occurs, the time width of the ion current signal detected by the ion current detection circuit 35 in the initial period of the energization period of the ignition coil 21 is long.

  However, as shown in FIG. 3, even when the smoldering state of the spark plug 27 has progressed, it is detected by the ion current detection circuit 35 at the beginning of the energization period of the ignition coil 21 as in the case where the on-fire is generated. Since the time width of the ion current signal is long, the ignition plug 27 is simply determined based on the ion current signal detected by the ion current detection circuit 35 at the beginning of the energization period of the ignition coil 21. When the smoldering state progresses, there is a possibility of erroneously determining that an on-fire has occurred.

  Therefore, the engine control microcomputer 41 executes an on-fire detection detection determination routine shown in FIG. 4 to be described later, so that a safety spark region, which is an operation region where on-fire occurs when the ignition system is normal, and an abnormality in the ignition system. In a specific operation region (see FIG. 7) set in an operation region other than both operation regions of the abnormal spark region, which is an operation region in which an on-fire occurs when the ignition coil fails or a different type of plug is installed, for example. It is determined whether the on-fire detection detection is permitted. In this embodiment, the smoldering state of the spark plug 27 is determined based on the ion current signal detected by the ion current detection circuit 35 in the specific operation region, and the on-fire detection detection permission state when the smoldering state of the spark plug 27 is equal to or less than a predetermined value. It is determined that

  The specific operation region set as the operation region other than the operation region of both the safety spark region and the abnormal spark region is an operation region in which almost no on-fire occurs, and therefore is affected by changes in the ion current signal due to the occurrence of on-fire. In addition, the smoldering state of the spark plug 27 can be accurately determined based on the ion current signal. When the smoldering state of the spark plug 27 proceeds, the time width of the ion current signal detected by the ion current detection circuit 35 in the initial period of the energization period of the ignition coil 21 becomes longer, as in the case where the on-fire occurs. Therefore, an ion current signal change that erroneously detects on-fire is generated, but when the smoldering state of the spark plug 27 is equal to or less than a predetermined value, an ion current signal change that erroneously detects on-fire is generated. Therefore, based on the ion current signal, it is determined that the on-firing can be accurately detected, and the on-firing detection permission state is determined.

  Further, the engine control microcomputer 41 executes an on-fire detection abnormal state determination routine of FIG. 5 to be described later, and when it is determined that the on-fire detection detection permission state is set, the ion is detected in the abnormal ignition region for each cylinder. Based on the ion current signal detected by the current detection circuit 35, it is determined whether or not there is an on-firing, and the on-firing is detected when the on-firing detection frequency is equal to or greater than a predetermined value (or when the on-detection frequency is equal to or greater than a predetermined value). It is determined that there is a flying fire abnormal state.

Further, the engine control microcomputer 41 executes a diagnosis and fail-safe control routine of FIG. 6 to be described later, and when it is determined that the on-fire condition is abnormal, it performs a diagnosis determination of an on-fire condition and warns. A fail-safe that warns the driver with a lamp, etc., and prevents abnormal combustion in a fail-safe operation region (high-load operation region where pre-ignition is likely to occur due to on-fire) including at least a part of the abnormal spark region Processing (for example, fuel cut) is executed.
The processing contents of the routines shown in FIGS. 4 to 6 executed by the engine control microcomputer 41 will be described below.

[On-fire detection permission judgment routine]
The on-fire detection detection determination routine shown in FIG. 4 is repeatedly executed at a predetermined cycle during engine operation, and serves as an on-fire detection permission determination means in the claims. When this routine is started, first, in step 101, the ionic current signal detected by the ionic current detection circuit 35 at the beginning of the energization period of the ignition coil 21 is compared with a predetermined determination level Vth1 for each cylinder. The detection time Tk (#i) is measured (#i is the cylinder number). Here, the smoldering detection time Tk (#i) is a time width in which the state in which the ion current signal exceeds the determination level Vth1 at the beginning of the energization period of the ignition coil 21 continues.

  Thereafter, the process proceeds to step 102, where it is determined whether or not the current engine operating state (engine rotational speed and engine load) is in a specific operating region. Here, as shown in FIG. 7 (a), the safety spark region is set to an operation region in which an on spark occurs when the ignition system is normal, and the abnormal spark region is an abnormality when the ignition system is abnormal (for example, when the ignition coil is faulty). Or when different types of plugs are installed, etc.). And the specific operation area | region is set to all the operation areas (namely, the operation area | region which almost does not generate | occur | produce on-on-fire) other than the operation area | region of both a safe sparking area and an abnormal sparking area. Alternatively, as shown in FIG. 7B, the specific operation region is set to an operation region in which the on-fire is surely not generated in the operation regions other than the operation region of both the safety spark region and the abnormal spark region. Anyway.

  If it is determined in this step 102 that the current engine operating state is not the specific operating region, it is an operating region in which on-fire may occur. This routine is terminated without performing the processing from step 103 onward.

  On the other hand, if it is determined in step 102 that the current engine operating state is the specific operating region, it is an operating region in which almost on-firing does not occur. If it is determined that it will not be received, the processing after step 103 is executed as follows.

  First, in step 103, it is determined for each cylinder whether or not the smolder detection time Tk (#i) is equal to or longer than a predetermined smolder determination value Tth1 (for example, 500 μs). As a result, if the smolder detection time Tk (#i) is equal to or greater than the smolder determination value Tth1, the routine proceeds to step 104, where it is determined as a smolder cycle. On the other hand, if the smolder detection time Tk (#i) is smaller than the smolder determination value Tth1, the routine proceeds to step 105, where it is determined as a normal cycle. The processing of these steps 103 to 105 serves as smolder detection means in the claims.

  Thereafter, the routine proceeds to step 106, where the number of smoldering cycles is counted for each cylinder to determine the smoldering detection frequency K (#i). Here, the smolder detection frequency K (#i) is, for example, the number of smolder cycles per 100 ignitions. Thereafter, the process proceeds to step 107, and it is determined for each cylinder whether or not the smolder detection frequency K (#i) is equal to or lower than a predetermined determination value Kth (for example, 0).

  If it is determined in this step 107 that the smolder detection frequency K (#i) is equal to or less than the determination value Kth, it is not a state in which an ion current signal change that erroneously detects an on-fire is generated, so that the ion current Based on the signal, it is determined that the on-firing can be accurately detected, and the process proceeds to step 108, where it is determined that the on-firing detection is permitted, and the on-firing detection permission flag KOKF is set to ON. To do.

  On the other hand, if it is determined in step 107 that the smolder detection frequency K (#i) is greater than the determination value Kth, an ion current signal change that causes false detection of on-fire is generated. Therefore, based on the ion current signal, it is determined that it is in a state where it is not possible to accurately detect on-fire, and the process proceeds to step 109, where it is determined that the on-fire detection detection is prohibited, and the on-fire detection detection flag KOKF is turned off ( To OFF).

[On-flying fire abnormal state judgment]
The on-fired abnormal condition determination routine shown in FIG. 5 is repeatedly executed at a predetermined cycle during engine operation, and serves as an on-fire abnormal condition determining means in the claims. When this routine is started, first, in step 201, the ion current signal detected by the ion current detection circuit 35 at the beginning of the energization period of the ignition coil 21 is compared with a predetermined determination level Vth2 for each cylinder. The spark detection time To (#i) is measured. This on-fire detection time To (#i) is a time width in which the state in which the ion current signal exceeds the determination level Vth2 continues in the initial period of the energization period of the ignition coil 21. Note that the smolder detection time Tk (#i) measured in step 101 of FIG. 4 may be read as the on-fire detection time To (#i).

Thereafter, the routine proceeds to step 202, where it is determined whether or not a predetermined on-fire detection condition is satisfied. Here, the on-fire detection condition is, for example, the following conditions (1) to (3).
(1) The on-fire detection detection enabled state (the on-fire detection detection flag KOKF is set to ON)
(2) The current engine operating state (engine speed and engine load) is in the abnormal spark area (see Fig. 7).
(3) The ion current detection system is in a normal state (the ion current signal is within a predetermined normal range).

  If all of these conditions (1) to (3) are met, the on-fire detection condition is met, but if any one of the above conditions (1) to (3) is not met, The spark detection condition is not satisfied.

  If it is determined in this step 202 that the on-fire detection condition is not satisfied, this routine is terminated without performing the processing after step 203. As a result, when the ion current detection system is not in a normal state (failure state), detection of on-fire is prohibited. This function serves as a prohibition means in the claims.

  On the other hand, if it is determined in step 202 that the on-fire detection condition is satisfied, the process proceeds to step 203, where the on-fire detection time To (#i) is set to a predetermined on-fire detection value Tth2 for each cylinder. It is determined whether or not (for example, 500 μs) or more. As a result, if the on-fire detection time To (#i) is equal to or longer than the on-fire detection value Tth2, the routine proceeds to step 204, where it is determined as an on-fire cycle. On the other hand, if the on-fire detection time To (#i) is smaller than the on-fire detection value Tth2, the routine proceeds to step 205, where a normal cycle is determined. The processing in these steps 203 to 205 serves as an on-fire detection means in the claims.

  Thereafter, the routine proceeds to step 206, where the number of on-firing cycles is counted for each cylinder, and the on-firing detection frequency S (#i) is obtained. Here, the on-firing detection frequency S (#i) is, for example, the number of on-firing cycles per 100 ignitions. Thereafter, the routine proceeds to step 207, where it is determined whether or not the on-fire detection frequency S (#i) is equal to or greater than the determination value Sth for each cylinder.

  If it is determined in step 207 that the on-fire detection frequency S (#i) is equal to or greater than the determination value Sth, the process proceeds to step 208, where it is determined that the on-fire detection abnormal state is present, and the on-fire detection abnormal state flag is determined. Set NFJ on.

  On the other hand, if it is determined in step 207 that the on-fire detection frequency S (#i) is smaller than the determination value Sth, the process proceeds to step 209, where it is determined that the state is normal and the on-fire is detected. The abnormal state flag NFJ is reset to off.

  In the routine shown in FIG. 5, it is determined whether or not the on-fire detection condition S (#i) is equal to or higher than the determination value Sth. The number of continuous on-fire detection times L (#i) is obtained by counting the number of consecutive on-firing cycles, and whether the on-fire detection status L (#i) is equal to or greater than a predetermined judgment value Lth. You may make it determine whether there exists.

[Diagnostic and fail-safe control]
The diagnosis and failsafe control routine shown in FIG. 6 is repeatedly executed at a predetermined cycle during engine operation. When this routine is started, first, in step 301, whether or not a predetermined diagnosis determination condition is satisfied, for example, whether or not the engine control system (various actuators, various sensors, etc.) is in a normal state. judge.

  If it is determined in step 301 that the diagnosis determination condition is satisfied, the process proceeds to step 302, and whether or not there is a cylinder determined to be in an on-firing abnormal state (a cylinder in which the on-firing abnormal state flag NFJ is on). If it is determined that there is a cylinder determined to be in an on-firing abnormal state, the process proceeds to step 303 to determine whether or not the battery voltage is in a normal state (for example, 16 V or less).

  If it is determined in step 303 that the battery voltage is in a normal state, it is determined that an on-firing abnormality state has occurred due to an abnormality in the ignition system, and the process proceeds to step 304 to perform a diagnosis determination process for on-firing failure. Do. In this diagnosis determination process, for example, a warning lamp (not shown) provided on the instrument panel of the driver's seat is turned on, or a warning display section (not shown) of the instrument panel of the driver's seat is displayed. A warning is displayed to warn the driver, and the abnormality information (abnormality code or the like) is stored in a rewritable nonvolatile memory such as a backup RAM (not shown) of the engine control circuit 34 (even when the engine control circuit 34 is powered off). It is stored in a rewritable memory that holds data.

  On the other hand, if it is determined in step 303 that the battery voltage is in an abnormal state, it is determined that an on-firing failure state has occurred due to an abnormality in the battery voltage, and diagnosis of an on-fire failure is prohibited. Then, the process proceeds to step 305, where a diagnosis of a battery voltage failure diagnosis is made. The processing of these steps 301 to 305 plays a role as a diagnostic means in the claims.

  Thereafter, the process proceeds to step 306, where it is determined whether or not there is a cylinder that is determined to be in an on-firing abnormal state. If it is determined that there is a cylinder that is determined to be in an on-firing abnormal state, the process proceeds to step 307. It is determined whether or not the current engine operation state (engine rotation speed and engine load) is in a predetermined fail-safe operation region. Here, as shown in FIG. 8, the fail-safe operation region is set to an operation region (a high-load operation region in which pre-ignition is likely to occur due to on-fire) that includes at least a part of the abnormal spark region. Yes.

  If it is determined in step 307 that the current engine operation state is the fail-safe operation region, the process proceeds to step 308, and it is determined whether or not the battery voltage is in a normal state (for example, 16 V or less).

  If it is determined in step 308 that the battery voltage is in a normal state, it is determined that there is a low possibility that the other cylinders will be in an on-firing abnormal state, and the process proceeds to step 309 to determine an on-firing abnormal state. Fail-safe processing (fuel cut) for preventing abnormal combustion with only the cylinders that have been performed is executed.

  On the other hand, if it is determined in step 308 that the battery voltage is in an abnormal state, it is determined that there is a high possibility that all cylinders will be in an on-firing abnormal state, and the routine proceeds to step 310 where abnormal combustion occurs in all cylinders. Fail-safe processing (fuel cut) is performed to prevent

  Thereafter, when it is determined in step 306 that there is no cylinder determined to be in an on-firing abnormal state, or when it is determined in step 307 that the current engine operating state is not in the fail-safe operating region. Then, the process proceeds to step 311 to cancel the fail-safe process (end the fuel cut and restart the fuel injection). The processes in these steps 306 to 311 serve as fail-safe control means in the claims.

  In the present embodiment described above, the smoldering state of the spark plug 27 is determined based on the ion current signal in a specific operation region (operation region in which almost no on-firing occurs) other than the operation region of both the safety spark region and the abnormal spark region. In addition, when the smoldering state of the spark plug 27 is equal to or less than a predetermined value, it is not a state in which an ionic current signal change that causes false detection of on-sparking is generated, so that on-sparking can be accurately detected based on the ionic current signal. It is determined that it is in the on-fire detection permission state. Then, when it is determined that the on-fire detection is permitted, the presence of on-fire is determined based on the ion current signal in the abnormal spark region, and if on-fire is detected in the abnormal spark region, Since the state is determined to be the state, it is possible to accurately detect the on-firing abnormal state.

  At this time, considering that the possibility of a secondary failure leading to engine damage due to pre-ignition due to on-sparking increases as the detection frequency of on-sparking fire and the number of continuous detections increase, If it is greater than the judgment value, or if the number of consecutive on-fire detections is greater than or equal to the judgment value, it is determined that the on-fire is abnormal, so a secondary failure that leads to engine failure due to pre-ignition due to on-fire occurs. Before, it is possible to reliably detect an on-firing abnormal state.

  In addition, when it is determined that there is an on-firing abnormal condition, a diagnosis of on-firing failure is performed and the driver is warned with a warning lamp etc. It can be repaired to prevent malfunctions caused by an on-firing abnormal state. In addition, when it is determined that the on-fire condition is abnormal, abnormal combustion occurs in a fail-safe operation area (a high-load operation area where pre-ignition is likely to occur due to on-fire) that includes at least a part of the abnormal spark area. Since the fail-safe process (for example, fuel cut) is performed to prevent the occurrence of pre-ignition due to on-fire, it is possible to prevent secondary failure leading to engine damage due to pre-ignition due to on-fire. be able to.

  In addition, in this embodiment, since detection of on-fire is prohibited when the ion current detection system is in a failure state, it is possible to prevent erroneous detection of on-fire due to failure of the ion current detection system. It is possible to prevent erroneous diagnosis and erroneous fail-safe processing due to false detection.

  Furthermore, in this embodiment, when it is determined that the on-fire alarm is in an abnormal state, when the battery voltage is in an abnormal state, the on-fire alarm failure diagnosis determination is prohibited and the battery voltage failure diagnosis determination is performed. When an on-fire error condition occurs due to an abnormality in the battery voltage, a diagnosis of battery voltage failure can be made separately from when an on-fire condition occurs due to an abnormality in the ignition system. There exists an advantage which becomes easy to specify a site | part.

  Further, in this embodiment, a fail-safe process for performing fuel cut in the fail-safe operation region is executed when it is determined that the on-fire condition is abnormal, and then it is determined that the on-fire condition is not abnormal. Since the safe process is canceled (fuel cut is ended and fuel injection is resumed), pre-ignition due to on-fire is prevented while minimizing deterioration in engine operating performance, and pre-ignition due to on-fire is prevented. It is possible to prevent secondary failures leading to engine damage by ignition.

  Further, in the present embodiment, when there is a cylinder determined to be in an on-firing abnormality state, when the battery voltage is normal, it is determined that the possibility of an on-firing abnormality state in other cylinders is low, and the on-firing abnormality state is determined. Fail-safe processing is executed only for cylinders that are determined to be in an abnormal state. When the battery voltage is abnormal, it is determined that there is a high possibility that all cylinders will be in an on-firing abnormal state, and fail-safe processing is executed for all cylinders. As a result, fail-safe processing can be executed as necessary.

  In the above-described embodiment, the fail-safe process for performing fuel cut in the fail-safe operation region is executed when it is determined that the on-fire condition is abnormal, but when it is determined that the on-fire condition is abnormal. Alternatively, the fail-safe process for limiting the throttle opening to a predetermined value or less may be continued only in the fail-safe operation region (or the entire operation region) until the engine operation is stopped.

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 on-fire. It is a time chart which shows behavior, such as an ion current signal at the time of on-firing occurrence, an ion current signal at the time of smoldering occurrence. It is a flowchart explaining the flow of a process of an on-fire detection detection permission determination routine. It is a flowchart explaining the flow of a process of on-firing abnormal state determination routine. It is a flowchart explaining the flow of a process of a diagnosis and a fail safe control routine. It is a figure explaining a safe spark region, an abnormal spark region, and a specific operation region. It is a figure explaining a fail safe driving | operation area | region.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 21 ... Ignition coil, 22 ... Primary coil, 23 ... Battery, 24 ... Igniter, 25 ... Power transistor, 26 ... Secondary coil, 27 ... Spark plug, 31 ... Ion current detection resistor, 33 ... Inversion amplification circuit, 34 ... Engine Control circuit, 35 ... ion current detection circuit (ion current detection means), 36 ... center electrode, 37 ... ground electrode, 41 ... engine control microcomputer (on spark detection means, on spark detection detection judging means, on spark detection abnormal state judgment Means, diagnostic means, fail-safe control means, smoldering detection means, prohibition means), 42 ... ion current signal processing circuit

Claims (9)

An ion current detection means for detecting an ion current generated by combustion of the air-fuel mixture in the combustion chamber of the internal combustion engine through an electrode of the spark plug;
On-fire detection that detects a phenomenon (hereinafter referred to as “on-sparking fire”) that sparks at the spark plug based on the energizing voltage of the ignition coil based on the ion current signal detected by the ion-current detecting means in the initial period of energization of the ignition coil Means,
It is set to an operation region other than the operation region of both the safe spark region where the on-fire occurs when the ignition system is normal and the abnormal spark region where the on-fire occurs when the ignition system is abnormal. On-firing detection detection determination means for determining whether or not the predetermined on-firing detection detection is permitted in the specific operation region;
On-fire detection abnormal state determination means for determining that the on-fire detection condition is detected when the on-fire detection is detected by the on-fire detection means in the abnormal ignition region when it is determined that the on-fire detection detection enabled state. ,
A control device for an internal combustion engine, comprising: a diagnostic unit that performs diagnostic determination of an on-firing failure when the on-firing abnormality state determining unit determines that the on-firing abnormality state is present. An ion current detection means for detecting an ion current generated by combustion of the air-fuel mixture in the combustion chamber of the internal combustion engine through an electrode of the spark plug;
On-fire detection that detects a phenomenon (hereinafter referred to as “on-sparking fire”) that sparks at the spark plug based on the energizing voltage of the ignition coil based on the ion current signal detected by the ion-current detecting means in the initial period of energization of the ignition coil Means,
It is set to an operation region other than the operation region of both the safe spark region where the on-fire occurs when the ignition system is normal and the abnormal spark region where the on-fire occurs when the ignition system is abnormal. On-firing detection detection determination means for determining whether or not the predetermined on-firing detection detection is permitted in the specific operation region;
On-fire detection abnormal condition determination means for determining that the on-fire detection condition is detected when the on-firing detection means is detected by the on-firing detection means in the abnormal ignition area when it is determined that the on-fire detection condition is permitted. ,
Performs a fail-safe process for preventing abnormal combustion in a fail-safe operation region of a predetermined load or more including at least a part of the abnormal spark region when the on-firing region abnormality determination unit determines that the on-firing region is in an abnormal state. And a fail-safe control means. Smolder detecting means for detecting a smoldering state of the spark plug based on an ion current signal detected by the ion current detecting means;
The on-fire detection detection permission determining unit determines that the on-sparking fire detection permission state is obtained when a smoldering state of the spark plug detected by the smolder detection unit in the specific operation region is equal to or less than a predetermined value. Item 3. The control device for an internal combustion engine according to Item 1 or 2.   The internal combustion engine control according to any one of claims 1 to 3, further comprising prohibiting means for prohibiting detection of the on-fire by the on-fire detection means when the ion current detection system is in a failure state. apparatus.   The on-fired abnormal condition determining means determines that the on-fired abnormal condition is present when the on-fire detection frequency is a predetermined value or more, or when the on-fire detection frequency is the predetermined value or more. The control device for an internal combustion engine according to any one of claims 1 to 4.   The diagnosis means, when it is determined that the on-firing abnormal state has occurred, and when the battery voltage is in an abnormal state, the on-firing failure diagnosis determination is prohibited and a diagnosis of the battery voltage failure is performed. The control apparatus for an internal combustion engine according to claim 1.   The fail-safe control means performs a fail-safe process for performing fuel cut in the fail-safe operation region when it is determined that the on-fire condition is abnormal, and is then determined not to be the on-fire condition. 3. The control device for an internal combustion engine according to claim 2, wherein the fail-safe process is sometimes canceled.   The fail-safe control means continues the fail-safe process for limiting the throttle opening to a predetermined value or less until the operation of the internal combustion engine is stopped when it is determined that the on-firing abnormal state has occurred. The control apparatus for an internal combustion engine according to claim 2. The on-fired abnormal state determining means determines whether or not the on-fired abnormal state is in each cylinder,
The fail-safe control means performs the fail-safe process on the cylinder determined to be in the on-firing abnormal state when the battery voltage is normal when there is a cylinder determined to be in the on-firing abnormal state, and the battery voltage 9. The control device for an internal combustion engine according to claim 2, wherein the fail-safe process is executed in all cylinders when the engine is in an abnormal state.

Images