JP6150614B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to a control device for an internal combustion engine. In particular, the present invention relates to a control device that detects an abnormality when an abnormality occurs in a spark plug or a spark ignition circuit connected to the ignition plug.

  Recently, an internal combustion engine mounted on a vehicle or the like is often accompanied by a self-diagnosis system for detecting the failure. For example, Patent Document 1 below discloses an apparatus that detects an ionic current flowing through an electrode of a spark plug during combustion and determines whether the combustion state of the fuel in the cylinder is good or bad. Japanese Patent Application Laid-Open No. 2004-228561 discloses a technique for estimating the relief flow rate of fuel supplied to an injector and determining whether the fuel pressure is maintained within an appropriate range. When it is detected that some failure has occurred in the internal combustion engine, an engine check lamp (warning light) in the cockpit of the vehicle is turned on to notify the user of the abnormality.

  When misfiring continues in a cylinder, the engine check lamp is lit, but there are various causes. Specifically, the aging of the spark plug, the electric circuit or ignition coil that applies a high voltage for spark discharge to the spark plug, damage to the capacitor, abnormality in the fuel system that supplies fuel to the injector, and filling the cylinder An abnormality in the intake system for supplying the intake air or the exhaust gas recirculation system may be considered.

  Even if only the spark plug is taken, the center electrode or the ground electrode may be worn out and the plug gap may be widened, or a conductive deposit such as carbon may be deposited to cause a short circuit between the center electrode and the ground electrode. is there. Both of these make spark discharge between the electrodes of the spark plug impossible.

  Furthermore, an insulator interposed between the center electrode and the ground electrode may be cracked, or a hole may be opened in the tube that accommodates the spark plug, causing discharge at the crack or hole. . Such an unexpected discharge leads to a decrease in the voltage applied to the center electrode of the spark plug during ignition, which hinders the ignition of the air-fuel mixture.

Japanese Patent Application Laid-Open No. 06-034490 JP 2011-064100 A

  As described above, there are various types of failures. In order to specify the content of the failure, it has been necessary to scrutinize each part of the internal combustion engine and the vehicle.

  An object of the present invention is to make it possible to easily know an abnormality of a spark plug, which is one cause of malfunction of an internal combustion engine.

A failure diagnosis device for an internal combustion engine according to the present invention is for determining a current state of a spark plug provided in a cylinder of the internal combustion engine, and energizing a primary coil of an ignition coil prior to spark ignition. In the circuit, the current flowing through the circuit connected to the electrode of the spark plug is repeatedly measured, and the circuit including the electrode of the spark plug obtained from the time series of the current value measured during the period or the time series of the current value The current state of the spark plug is determined based on the magnitude of the electrical resistance value, and the current value measured during the period exceeds the threshold for a short time equal to or less than a certain value, or the current measured during the period If the electrical resistance value of the circuit including the electrode of the spark plug determined from the value is below the threshold value for a short period of time below a certain value, an unexpected discharge in the spark plug or an unexpected leakage in the circuit Characterized by determining that There has occurred.

  According to the present invention, it is possible to easily know the abnormality of the spark plug, which is one cause of the malfunction of the internal combustion engine.

The figure which shows schematic structure of the internal combustion engine in one Embodiment of this invention. The circuit diagram of the spark ignition device in the embodiment. The figure which shows transition of the primary current which flows through the primary side coil of an ignition coil in the period from ignition of an igniter to spark ignition. The figure which shows each transition of the combustion pressure and the ionic current in the cylinder of an internal combustion engine. The figure which shows each transition of the ignition signal and the electric current signal which flows through the electrode of a spark plug in the period from ignition of an igniter to spark ignition. The figure which shows each transition of the ignition signal and the electric current signal which flows through the electrode of a spark plug in the period from ignition of an igniter to spark ignition. The figure which shows each transition of the ignition signal and the electric current signal which flows through the electrode of a spark plug in the period from ignition of an igniter to spark ignition. The figure which shows each transition of the ignition signal and the electric current signal which flows through the electrode of a spark plug in the period from ignition of an igniter to spark ignition. The figure which shows each transition of the ignition signal and the electric current signal which flows through the electrode of a spark plug in the period from ignition of an igniter to spark ignition. The figure explaining the content of the judgment process which the control apparatus of this embodiment performs. The figure explaining the content of the judgment process which the control apparatus of this embodiment performs. The figure explaining the content of the judgment process which the control apparatus which concerns on one modification of this invention performs. The figure explaining the content of the judgment process which the control apparatus of the modification performs.

  An embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows an outline of an internal combustion engine for a vehicle in the present embodiment. The internal combustion engine in the present embodiment is a spark ignition type 4-stroke gasoline engine, and includes a plurality of cylinders 1 (one of which is shown in FIG. 1). In the vicinity of the intake port of each cylinder 1, an injector 11 for injecting fuel is provided. A spark plug 12 is attached to the ceiling of the combustion chamber of each cylinder 1.

  FIG. 2 shows an electric circuit for spark ignition. The spark plug 12 receives spark voltage generated by the ignition coil 14 and causes spark discharge between the center electrode and the ground electrode. The ignition coil 14 is integrally incorporated in the coil case together with the igniter 13 having the semiconductor switching element 131.

  When the igniter 13 receives an ignition signal i from an ECU (Electronic Control Unit) 0, which is a control device for the internal combustion engine, first, the semiconductor switch 131 of the igniter 13 is ignited and a current flows to the primary side of the ignition coil 14, immediately thereafter. At this spark ignition timing, the semiconductor switch 131 extinguishes and this current is cut off. Then, a self-induction action occurs, and a high voltage is generated on the primary side. Since the primary side and the secondary side share the magnetic circuit and the magnetic flux, a higher induced voltage is generated on the secondary side. The induced voltage on the secondary side reaches 10 kV to 30 kV. This high induction voltage is applied to the center electrode of the spark plug 12, and a spark discharge occurs between the center electrode and the ground electrode.

  The primary coil of the ignition coil 14 is connected to the in-vehicle power supply battery 17 via the semiconductor switch 131. When the semiconductor switch 131 is ignited and a DC voltage supplied from the battery 17 is applied to the primary side coil to start energization, the primary current flowing through the primary side (low voltage system) circuit including the primary side coil increases.

FIG. 3 illustrates the transition of the primary current after the start of energization of the primary coil. In FIG. 3, the case where the current limiting function does not work is drawn with a broken line, and the case where the current limiting function works is drawn with a solid line. Assuming that the primary side electric circuit including the battery 17 and the primary side coil is an RL series circuit, the primary current I (t) when the DC voltage E is applied at time t = 0 is
I (t) ≈ {1-e- ^{(R / L) t} } E / R
It becomes. That is, the primary current increases as a transient phenomenon, but the rate of increase gradually decreases. When a sufficiently long time elapses, the primary current saturates to E / R as shown by the broken line in FIG.

  The igniter 13 has a current limiting function that suppresses excessive primary current. This current limiting function is similar to that of off-the-shelf igniters that are popular today. Specifically, the control circuit 132 constantly measures the primary current in the form of the voltage across the resistor 133 via the detection resistor 133. Then, the semiconductor switch 131 is ignited while the magnitude of the primary current (voltage across the resistor 133) is equal to or less than the predetermined value, while the semiconductor switch 131 is extinguished when it exceeds the predetermined value. As a result, the primary current is clipped to a predetermined value as shown by the solid line in FIG.

  The igniter 13 also has a function of forcibly shutting off the energization of the primary coil when detecting abnormal heat generation such that the temperature of the ignition coil 14 or the igniter 13 itself exceeds a threshold value.

  The ECU 0 of the present embodiment can detect an ionic current generated in the combustion chamber of the cylinder 1 during fuel combustion, and can determine the combustion state with reference to the ionic current.

  As shown in FIG. 2, in this embodiment, a circuit for detecting an ionic current is added to the electric circuit for spark ignition. This detection circuit includes a bias power supply unit 15 for effectively detecting an ionic current and an amplification unit 16 that amplifies and outputs a detection voltage corresponding to the amount of the ionic current. The bias power supply unit 15 includes a capacitor 151 that stores a bias voltage, a Zener diode 152 for increasing the voltage of the capacitor 151 to a predetermined voltage, current blocking diodes 153 and 154, and a load that outputs a voltage corresponding to the ion current. A resistor 155. The amplifying unit 16 includes a voltage amplifier 161 typified by an operational amplifier.

  The capacitor 151 is charged during arc discharge between the center electrode and the ground electrode of the spark plug 12, and then an ion current flows through the load resistor 155 by the bias voltage charged in the capacitor 151. The voltage between both ends of the resistor 155 generated by the flow of the ionic current is amplified by the amplifying unit 16 and received by the ECU 0 as the ionic current signal h.

  FIG. 4 illustrates respective transitions of the ionic current and the combustion pressure in the cylinder 1 (in-cylinder pressure) in normal combustion. In FIG. 4, the ionic current is drawn with a broken line, and the combustion pressure is drawn with a solid line. The ionic current cannot be detected during the discharge for ignition. In the case of normal combustion, the ionic current decreases by a chemical reaction before the compression top dead center after the end of spark ignition, and then increases again by thermal dissociation. In addition, the ionic current reaches a maximum almost simultaneously with the peak of the combustion pressure.

  The intake passage 3 for supplying intake air takes in air from the outside and guides it to the intake port of each cylinder 1. On the intake passage 3, an air cleaner 31, an electronic throttle valve 32, a surge tank 33, and an intake manifold 34 are arranged in this order from the upstream.

  The exhaust passage 4 for discharging the exhaust guides the exhaust generated as a result of burning the fuel in the cylinder 1 from the exhaust port of each cylinder 1 to the outside. An exhaust manifold 42 and an exhaust purification three-way catalyst 41 are disposed on the exhaust passage 4.

  The ECU 0 that controls operation of the internal combustion engine is a microcomputer system having a processor, a memory, an input interface, an output interface, and the like.

  The input interface includes a vehicle speed signal a output from a vehicle speed sensor that detects the actual vehicle speed of the vehicle, a crank angle signal b output from an engine rotation sensor that detects the rotation angle and engine speed of the crankshaft, and depression of an accelerator pedal. An accelerator opening signal c output from a sensor that detects the amount or the opening of the throttle valve 32 as an accelerator opening (so-called required load), and a brake pedaling amount signal d output from a sensor that detects the amount of depression of the brake pedal The intake air temperature / intake pressure signal e output from the temperature / pressure sensor for detecting the intake air temperature and the intake pressure in the intake passage 3 (particularly, the surge tank 33), and the output from the water temperature sensor for detecting the cooling water temperature of the engine. The cam angle sensor outputs the cooling water temperature signal f and a plurality of cam angles of the intake camshaft or the exhaust camshaft. Angle signal g, a current signal h or the like to be output from the circuit for detecting an ion current caused by the combustion of the mixture in the combustion chamber are inputted.

  From the output interface, an ignition signal i is output to the igniter 13, a fuel injection signal j is output to the injector 11, and an opening operation signal k is output to the throttle valve 32.

  The processor of the ECU 0 interprets and executes a program stored in the memory in advance, calculates operation parameters, and controls the operation of the internal combustion engine. The ECU 0 acquires various information a, b, c, d, e, f, g, and h necessary for operation control of the internal combustion engine via the input interface, knows the engine speed, and is filled in the cylinder 1. Estimate the intake volume. Based on the engine speed, the intake air amount, and the like, various operating parameters such as required fuel injection amount, fuel injection timing (including the number of times of fuel injection for one combustion), fuel injection pressure, and ignition timing are determined. As the operation parameter determination method itself, a known method can be adopted. The ECU 0 applies various control signals i, j, k corresponding to the operation parameters via the output interface.

  Thus, the ECU 0 of the present embodiment senses a failure or other abnormality of the spark plug 12 using a circuit that detects an ionic current flowing through the electrode of the spark plug 12 during combustion.

  FIGS. 5 to 9 show the time-series transition of the ignition signal i given from the ECU 0 to the igniter 13 and the value of the current signal h acquired by the ECU 0 through the circuit for detecting the ionic current. The current signal h represents the current flowing through the electrode of the spark plug 12 and also represents the magnitude of the resistance between both electrodes of the spark plug 12.

The ECU 0 ignites the semiconductor switch 131 of the igniter 13 prior to the spark ignition and energizes the primary coil of the ignition coil 14. As shown in FIG. 3, the primary current flowing through the primary coil increases after the semiconductor switch 131 is ignited. The ECU ₀ extinguishes the semiconductor switch 131 and cuts off the energization of the primary coil of the ignition coil 14 at a time t ₁ after a predetermined energization time has elapsed from the time t ₀ when the semiconductor switch 131 is ignited. To do. Basically, the transition of the ignition signal i for controlling the ignition / extinction of the semiconductor switch 131 is common to all of FIGS.

FIG. 5 shows the case of normal combustion. The current signal h in the case of normal combustion is noticeable after the time t ₂ when a spark discharge period caused between the two electrodes of the spark plug 12 with the extinction of the semiconductor switch 131 has elapsed. It includes the signal of the ion current generated in More specifically, the signal due to LC resonance appears at time t _2, then the ion current signal due to combustion appears.

Incidentally, at the time t ₀ when the semiconductor switch 131 is ignited, spike noise is generated and superimposed on the current signal h. In addition, the current signal h vibrates immediately before the extinction time t ₁ of the semiconductor switch 131. This vibration suppresses the magnitude of the temporary current flowing on the primary side of the ignition coil 14 to a predetermined value or less. This is due to the function of the control circuit 132 (ON / OFF switching operation of the semiconductor switch 131).

FIG. 6 shows the case where the spark discharge by the spark plug 12 was normal, but the air-fuel mixture in the combustion chamber of the cylinder 1 did not burn well and misfired. The difference from FIG. 5 is that an ionic current signal having a sufficient magnitude and length does not appear in the current signal h after the occurrence of LC resonance at time t ₂ after the spark discharge period.

  7 to 9 are examples in the case where some abnormality exists in the spark plug 12. 7 shows a case where an insulator interposed between the center electrode and the ground electrode of the spark plug 12 is cracked or a hole is opened in a tube that accommodates the spark plug 12. Yes.

In FIG. 5 or FIG. 6, during the period from the ignition time t ₀ to the extinction time t ₁ of the semiconductor switch 131, spike noise substantially at the time t ₀ or the operation of the control circuit 132 immediately before the time t ₁ ( Except for the time when the primary current was saturated, the current signal h was low and stable.

On the other hand, in FIG. 7, when a certain amount of time has elapsed from the ignition time t ₀ of the semiconductor switch 131, a spike-like current signal h that instantaneously increases appears. This is because the ignition switch 12 is ignited by the potential difference between the center electrode side of the spark plug 12 that is gradually boosted as the primary current increases and the ground electrode side of the spark plug 12 that is constantly grounded. A circuit on the secondary side (high voltage system) in which a discharge is generated through a crack in the insulator of the plug 12 or a hole in the tube, or the center electrode of the ignition plug 12 and the secondary coil of the ignition coil 14 are connected. This is because an instantaneous electric leakage occurred at any of the points.

Then, since such discharge or leakage causes loss of electrical energy to be applied to the center electrode of the spark plug 12 at the ignition timing t ₁ , spark discharge in the gap between the center electrode and the ground electrode, and hence mixing The spark ignition to the ki will not work well. Thus, at time t ₂ after the period to be the occurrence of spark discharge, ion current signal of sufficient magnitude and length does not appear in the current signal h. In FIG. 7, the ion current signal h after time t ₂ has become zero.

The above discharge or electric leakage is caused by a potential difference of just over 1 kV, which is lower than that applied to the center electrode during normal spark ignition. As already described, during the period from the ignition time t ₀ of the semiconductor switch 131 to the extinguishing time t ₁ , the current flowing through the primary coil of the ignition coil 14 is excluding the operation timing of the control circuit 132 immediately before the extinction. Increasing. Therefore, an induced voltage of 1 kV to 2 kV is generated in the secondary coil of the ignition coil 14 during the same period.

  Discharge and leakage can occur through a path through which electrons are more likely to pass. In the operation region where the load of the internal combustion engine is relatively low, the amount of intake air charged into the cylinder 1 is small, and the density in the combustion chamber of the cylinder 1 is low. Therefore, it can be said that the discharge is relatively easy between the center electrode of the spark plug 12 and the ground electrode. However, an applied voltage of about 1 kV to 2 kV is not enough to cause a spark discharge in the gap between both electrodes.

  In contrast, in the operation region where the load of the internal combustion engine is relatively high, the amount of intake air charged into the cylinder 1 is large, and the density in the combustion chamber of the cylinder 1 increases. Therefore, it is difficult to discharge between the center electrode of the spark plug 12 and the ground electrode, and it is relatively easy to discharge at a location such as a crack in the insulator or a hole in the tube. Undesirable electric discharge through the crack of the insulator or the hole of the tube or the undesired leakage in the secondary circuit may or may not occur depending on the operating region of the internal combustion engine.

FIG. 8 shows a case where a conductive deposit such as carbon is deposited and deposited on the center electrode and / or the ground electrode of the spark plug 12 and the two electrodes are short-circuited or nearly short-circuited. Since the insulation resistance between the two electrodes is reduced due to the deposit, the leakage current h that is not zero is observed for a relatively long time during the period from the ignition time t ₀ to the extinction time t ₁ of the semiconductor switch 131. appear. The point that the current signal h after time t ₂ is 0 is the same as in the case of FIG.

FIG. 9 shows a case where the center electrode and / or the ground electrode of the spark plug 12 has been worn out and the gap between the two electrodes has expanded beyond an allowable size. Since no discharge or leakage occurred, the current signal h during the period from time t _{0 to} time t ₁ when the semiconductor switch 131 is ignited is the same as in FIG. 5 or FIG.

However, since the insulation resistance of the plug gap is excessive, even if the semiconductor switch 131 is extinguished and a high voltage is applied to the center electrode of the spark plug 12, a current such as noise is applied to the electrode of the spark plug 12. Only intermittently flows, and no spark discharge suitable for ignition is induced. As a result, as shown in FIG. 9, a noise-like waveform appears in the current signal h immediately after the time t ₁ when the semiconductor switch 131 is extinguished. In addition, since the spark discharge itself fails, the ion current signal h becomes 0 after time t ₂ after the original spark discharge period.

  The failure of the spark discharge as shown in FIG. 9 also occurs when an insulating deposit such as silica (silicon dioxide) adheres to and accumulates on the center electrode and / or the ground electrode of the spark plug 12.

The ECU 0 can determine whether the combustion state of the fuel in the cylinder 1 is good or not by referring to the current signal h after the time t ₂ after the spark discharge period. If a sufficiently large and / or long ion current signal h appears after time t _2, it is determined that good combustion has been performed in the cylinder 1. Conversely, if an ion current signal h having a sufficient magnitude and / or length does not appear after time t ₂ , it is determined that misfire has occurred in the cylinder 1 or combustion in the cylinder 1 has been unstable.

In addition, the ECU ₀ of the present embodiment has a period from the ignition time t ₀ of the semiconductor switch 131 to the extinction time t ₁ (more strictly, before the operation of the control circuit 132 accompanying the saturation of the primary current). The magnitude of the secondary current h flowing through the secondary circuit is repeatedly measured, and the electrical resistance value of the secondary circuit including the spark plug 12 is estimated based on the time series of the current value. This electrical resistance is mainly the insulation resistance of the gap between the center electrode of the spark plug 12 and the ground electrode.

The induced voltage V (t) generated in the primary coil during the period from the starting time t ₀ to the extinguishing time t ₁ is the reactance of the primary coil in the time differentiation of the primary current I (t) flowing through the primary coil. V (t) multiplied by L ≒ e- ^{(R / L) t} E
Can be computed as Then, the induced voltage generated in the secondary coil at an arbitrary time t within the same period is obtained from the induced voltage V (t) and the transformation ratio of the ignition coil 14 and the like. The electrical resistance value of the secondary side circuit, that is, the magnitude of the insulation resistance by the spark plug 12, is obtained by dividing the induced voltage generated in the secondary side coil by the measured value of the current h flowing through the secondary side coil. It is done.

  No deposits are attached to the electrodes, and no insulator cracks or tube perforations occur (in other words, an unused normal product) the insulation resistance between the electrodes of the spark plug 12 is about 500 MΩ. .

  When smoldering deposits of carbon or other deposits occur on the electrodes, the insulation resistance between the electrodes of the spark plug 12 decreases. That is, if the current h flowing through the secondary circuit is measured and the electric resistance value is calculated, the electric resistance value can be used as an index value for evaluating the degree of smoldering of the spark plug 12. That is, the lower the electrical resistance value, the more the electrode of the spark plug 12 is soiled by smoldering.

  However, when the insulator of the spark plug 12 is cracked or a hole is formed in the tube and a discharge is caused at that location, or when a leakage occurs in the secondary circuit, the current flowing through the secondary circuit The measured value of h increases in a spike shape. Then, when the discharge or leakage occurs, the electrical resistance value of the secondary side circuit drops momentarily. In order to correctly grasp the state of the spark plug 12 on the basis of the electrical resistance value estimated based on the measured value of the secondary current h, a constant decrease in the electrical resistance value due to smoldering and an instantaneous due to discharge or leakage It is necessary to distinguish from a decrease in electrical resistance.

Therefore, as shown in FIG. 10, the ECU _{0 of} the present embodiment counts the time T _A when the electrical resistance value of the secondary circuit estimated during the period from the ignition time t ₀ to the extinction time t ₁ falls below the threshold value. and, the T _a is in the case of long time of more than a predetermined value, it is determined that the smoldering electrode of the spark plug 12. The threshold is set to 100 MΩ, for example.

  The ECU 0 that has determined that the electrode of the spark plug 12 is smoldering executes a cleaning process for removing carbon or the like deposited on the electrode of the spark plug 12. In the cleaning process, for example, the fuel injection amount is reduced with respect to the intake air amount filled in the cylinder 1 to reduce the air-fuel ratio of the air-fuel mixture, or conversely, the fuel injection amount is increased to enrich the air-fuel ratio of the air-fuel mixture. It is conceivable that spark discharge is generated in the spark plug 12 during the exhaust stroke of the cylinder 1 or during fuel cut (temporary stop of fuel injection). In either case, the carbon or the like adhering to the electrode of the spark plug 12 is promoted to be oxidized and discharged out of the cylinder 1 in the form of carbon dioxide.

  If it is determined that the spark plug 12 is still smoldered even though the cleaning process has been performed a predetermined number of times (one or more times) in one cylinder 1, it indicates that the smolder of the spark plug 12 cannot be removed. The indicated information (diagnosis code) is written in the memory of the ECU 0 and stored and held to assist in the investigation of the cause and the location of the repair in the subsequent repair work. In addition, the presence of abnormality in the internal combustion engine is notified in a manner that appeals to the user's vision or hearing. For example, an engine check lamp (warning light) installed in the cockpit is turned on, a warning is displayed on the display, or a warning sound is output from a buzzer or a speaker.

And, ECU0 of the present embodiment, as shown in FIG. 11, counting the time T _B which electrical resistance of the secondary circuit which is estimated in the period from the firing time t ₀ to the extinguishing time t ₁ is below a threshold and, in that case T _B is less very short time constant, the leakage of the unexpected in any point of cracking and unexpected discharge caused by drilling or the like of the tube or the secondary circuit, the insulator occurs to decide. The threshold value to be compared with the electric resistance value when determining the presence or absence of discharge or electric leakage may be the same value as the threshold value to be compared with the electric resistance value when determining whether or not the electrode of the spark plug 12 is smoldered. Different values may be used. The constant value to be compared with the time T _B may be the same value as the constant value to be compared with the time T _A described above, or may be a different value.

  The ECU 0 that has determined the occurrence of unexpected discharge or electric leakage for a single cylinder 1 a predetermined number of times (one or more times) has information indicating that electric discharge in the spark plug 12 or electric leakage in the secondary circuit has occurred. It is written and stored in the memory of the ECU 0 to help investigate the cause and specify the repair location in the subsequent repair work. In addition, the presence of abnormality in the internal combustion engine is notified in a manner that appeals to the user's vision or hearing. For example, an engine check lamp installed in the cockpit is turned on, a warning is displayed on the display, or a warning sound is output from a buzzer or a speaker.

Further, using the electric resistance value of the secondary circuit estimated during the period from the ignition time t ₀ to the extinction time t ₁ as an index value, the degree of wear of the electrode of the spark plug 12 and an insulating deposit such as silica The degree of adhesion can also be evaluated. In other words, the higher the electric resistance value, the more the electrode of the spark plug 12 is worn and the plug gap is expanded, or the electrode of the spark plug 12 is soiled by an insulating deposit.

When the electrical resistance value of the secondary side circuit estimated during the period from the ignition time t ₀ to the extinguishing time t ₁ exceeds the threshold, the ECU ₀ increases the plug gap beyond the allowable range or performs insulation. It is determined that a sex deposit is deposited. The threshold value here is that no deposit is attached to the electrodes, and there is no cracking of the insulator or perforation of the tube (in other words, the insulation resistance between the electrodes of the spark plug 12 which is an unused normal product). Set to a higher value.

  The ECU 0 that determines the expansion of the plug gap or the deposition of the insulating deposit for a single cylinder 1 a predetermined number of times (one or more times) has worn the electrode of the spark plug 12 or deposited the insulating deposit. Information indicating this is written in the memory of the ECU 0 and stored, which is used to investigate the cause in the subsequent repair work and specify the repair location. In addition, the presence of abnormality in the internal combustion engine is notified in a manner that appeals to the user's vision or hearing. For example, an engine check lamp installed in the cockpit is turned on, a warning is displayed on the display, or a warning sound is output from a buzzer or a speaker.

In the present embodiment, the current state of the spark plug 12 provided in the cylinder 1 of the internal combustion engine is determined, and the primary coil of the ignition coil 14 is energized prior to the spark ignition (point of the igniter 13). During the period from the arc time t ₀ to the extinction time t ₁ , the secondary current h flowing through the secondary circuit connected to the electrode of the spark plug 12 is repeatedly measured, and the current measured during the period is measured. Control of an internal combustion engine, wherein the current state of the spark plug 12 is determined based on the magnitude of the electrical resistance value of the secondary circuit including the electrode of the spark plug 12 obtained from a time series of values Device 0 was configured.

  The present control device 0 is configured so that the electrode of the spark plug 12 is provided on the condition that the electrical resistance value of the secondary side circuit obtained from the current value measured during the energization period of the primary side coil is below the threshold value for a certain time or more. Judge that it is smoldering. Then, a cleaning process for removing the smoldering is executed.

  In addition, the present control device 0 ignites on the condition that the electrical resistance value of the secondary side circuit obtained from the current value measured during the energization period of the primary side coil is below the threshold value for a short period of time less than or equal to a certain value. It is determined that an unexpected discharge in the plug 12 or an unexpected leakage in the circuit has occurred.

  According to the present embodiment, it is possible to easily know the abnormality of the spark plug 12 or the secondary circuit, which is one cause of the malfunction of the internal combustion engine. Not only is the content of the abnormality, for example, a crack in the insulator of the spark plug 12 or a tube perforation, a short circuit between the electrodes due to smoldering, widening of the gap between the electrodes or deposition of silica. It is possible to specify whether it is.

  When misfiring continues in the cylinder 1 of the internal combustion engine, it is possible to identify and identify whether the cause is damage (or wear) of the spark plug 12 or an abnormality of a device other than the spark plug 12. Therefore, it is not necessary to scrutinize each part of the internal combustion engine and the vehicle one by one, leading to reduction in maintenance, inspection and maintenance costs. If the spark plug 12 or the tube is damaged, it is sufficient to replace the spark plug 12 or the tube. If the spark plug 12 or the tube is not damaged, a device such as a fuel system or an intake system may be investigated.

  It is also an advantage that an abnormality of the spark plug 12 can be sensed by utilizing an existing circuit for detecting an ion current signal. There is no need to newly install hardware for constantly monitoring the voltage applied to the center electrode of the spark plug 12 for the purpose of investigating the presence or absence of electric leakage at a location such as an insulator crack.

The present invention is not limited to the embodiment described in detail above. In the above embodiment, during the period from the ignition time t ₀ of the semiconductor switch 131 to the arc extinction time t _1, it flows through the secondary circuit that connects the center electrode of the spark plug 12 and the secondary coil of the ignition coil 14. The current h is measured, and the electrical resistance value of the secondary side circuit is estimated from the measured value to diagnose the presence or absence of the spark plug 12 and the type of abnormality. However, even if the measured value of the current h flowing in the secondary circuit in the period is referred to diagnose the presence / absence of the spark plug 12 and the type of abnormality, the same effects as in the above embodiment can be obtained. obtain.

In that case, as shown in FIG. 12, the ECU 0 as the control device counts the time T _C during which the current value measured in the period exceeds the threshold, and if the T _C is a long time equal to or greater than a certain value, It is determined that the electrode of the plug 12 is smoldering.

  The ECU 0 that has detected the smoldering of the electrode of the spark plug 12 executes a cleaning process for removing the smoldering of the electrode or provides information (diagnosis code) indicating that the electrode is smoldering, as in the above embodiment. It memorize | stores in a memory or alert | reports in the aspect which appeals to a user's vision or hearing.

And, ECU0, as shown in FIG. 13, when the current value measured in the period counted time T _D above a threshold, its T _D the following very short time constant, cracking of the insulator It is determined that an unexpected discharge due to a perforation of the tube or an unexpected electric leakage occurred in any part of the secondary circuit. The threshold value to be compared with the current value when determining the presence or absence of discharge or electric leakage may be the same value as the threshold value to be compared with the current value when determining whether or not the electrode of the spark plug 12 is smoldered. Different values may be used. Constant value is also compared with the time T _D, may be used as the same value as the predetermined value to be compared with the time T _C of the above, the value may be different from this.

  The ECU 0 that has detected the unexpected discharge or leakage stores information indicating that the discharge or leakage has occurred in the memory, and appeals to the user's vision or hearing in the same manner as in the above embodiment. Inform.

  In addition, when the current value measured in the period is lower than the threshold value, it may be determined that the plug gap expands beyond an allowable range or that an insulating deposit is deposited. The threshold value here is the secondary side under the condition that no deposit is attached to the electrode of the spark plug 12 and the insulator is not cracked or the tube is not perforated (or an unused normal product). Set to a value lower than the minimum value of the current flowing through the circuit.

  The ECU 0 that has detected the expansion of the plug gap or the deposition of the insulating deposit stores information indicating that the plug gap is expanded or the insulating deposit is deposited on the electrodes in the memory, as in the above embodiment. This is reported in a manner that appeals to the user's vision or hearing.

  Generally speaking, during the period in which the primary coil of the ignition coil 14 is energized, the measured value of the current h flowing through the secondary circuit connected to the electrode of the spark plug 12 or the secondary side obtained from the measured value. The electric resistance value of the circuit is an index value representing the degree of smoldering of the electrode of the spark plug 12, wear of the electrode, or deposition of silica or the like. Furthermore, when the measured value of the current h flowing through the secondary circuit or the electrical resistance value of the secondary circuit fluctuates for a very short time (instantaneous increase in current h or a decrease in electrical resistance value) during this period. Therefore, it is determined that a discharge or leakage has occurred in any part of the spark plug 12 or the secondary circuit.

  Other specific configurations of each part can be variously modified without departing from the spirit of the present invention.

  The present invention can be applied to control of an internal combustion engine mounted on a vehicle or the like.

0 ... Control unit (ECU)
DESCRIPTION OF SYMBOLS 1 ... Cylinder 12 ... Spark plug 13 ... Igniter 14 ... Ignition coil h ... Current signal

Claims (1)

Determining the current state of a spark plug provided in a cylinder of an internal combustion engine,
During the period in which the primary coil of the ignition coil is energized prior to spark ignition, the current flowing through the circuit connected to the electrode of the spark plug is repeatedly measured,
Based on the magnitude of the time series or electrical resistance of the circuit including the electrode of the spark plug obtained from the time series of the current value, the current value measured in the time period, and to determine the current state of the spark plug ,
The current value measured during the period exceeds the threshold for a short time that is less than or equal to a certain time, or the electrical resistance value of the circuit that includes the electrode of the spark plug obtained from the current value measured during the period is equal to or less than a certain time The control device for an internal combustion engine that determines that an unexpected discharge in the spark plug or an unexpected electric leakage in the circuit occurs when the value is lower than .

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