JP2014066170A - Control device of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control device of an internal combustion engine which can narrow the cause of defective start-up when the internal combustion engine cannot start up normally.SOLUTION: In a system capable of measuring an ion current flowing through an electrode of an ignition plug upon combustion, in such a case that the start-up cannot be ended even when a predetermined time elapses from the start-up of an internal combustion engine, a place where abnormality exists is estimated based on the length of a period in which the magnitude of ion current measured when operating the engine just before exceeds a threshold. When the length of the period in which the magnitude of ionic current exceeds the threshold is extremely long, the smoldering of the ignition plug is suspected. On the contrary, when the length of the period is extremely short, an abnormality besides the smoldering of the ignition plug, for example, the failure of a fuel injection system is suspected. When the length of the period is middle, there is such a possibility that a gas mixture leaks during a compression stroke although the combustion itself occurs.

Description

  The present invention relates to a control device for an internal combustion engine, and more particularly to control at engine start.

  When starting an internal combustion engine, it is usual to perform cranking by rotating a crankshaft of the engine by a starter motor (cell motor) which is an electric motor (for example, refer to the following patent document). Cranking ends when the engine starts from the first explosion to the consecutive explosion and the rotational speed of the crankshaft exceeds a determination value determined according to the coolant temperature or the like.

JP 2011-202643 A

  When the internal combustion engine fails to start successfully, there are several possible causes. To enumerate, deposits such as carbon adhere to and accumulate on the electrode of the spark plug, which may interfere with spark ignition, so-called spark plug smoldering, or a sufficient amount of fuel is not injected from the injector, or the compression stroke In FIG. 3, the air-fuel mixture leaks into the intake port or the exhaust port, and although the combustion itself occurs in the expansion stroke, the rotational torque of the crankshaft does not increase.

  Nevertheless, the conventional control device does not consider at all the narrowing down of the cause of the start failure of the internal combustion engine, in other words, the location where the abnormality occurs. Therefore, a considerable amount of labor and time are spent analyzing the cause, such as a serviceman thoroughly checking the entire internal combustion engine.

  An object of the present invention is to make it possible to narrow down the cause of a start failure of an internal combustion engine.

  In order to solve the above-mentioned problems, the present invention provides a control device for an internal combustion engine capable of measuring a current flowing through an electrode through a circuit for detecting an ionic current flowing through the electrode of a spark plug during combustion. The magnitude of the ionic current measured through the circuit when the internal combustion engine was operating immediately before if the engine could not be completed even after a predetermined time had elapsed since the start of the internal combustion engine being stopped The control apparatus for an internal combustion engine is characterized in that the location of an abnormality in the internal combustion engine is estimated based on the length of the period during which the value exceeds the threshold.

  According to the present invention, it is possible to narrow down the cause of the start failure 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 each transition of the combustion pressure and the ionic current in the cylinder of an internal combustion engine. The figure which shows the relationship between the location where abnormality of an internal combustion engine exists, and transition of the detected electric current. The flowchart which shows the example of a procedure of the process which the control apparatus of the embodiment 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 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.

  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.

  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 a coil case together with an igniter 13 that is a semiconductor switching element.

  When the igniter 13 receives an ignition signal i from an ECU (Electronic Control Unit) 0 that is a control device for the internal combustion engine, the igniter 13 is first ignited, and a current flows to the primary side of the ignition coil 14. The igniter 13 is extinguished to interrupt this current. 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. This high induction voltage is applied to the center electrode of the spark plug 12, and spark discharge occurs between the center electrode and the ground electrode.

  The ECU 0 detects an ionic current generated in the combustion chamber of the cylinder 1 at the time of fuel explosive combustion, and refers to the ionic current to determine a combustion state.

  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. 3 exemplifies transitions of the ionic current and the combustion pressure in the cylinder 1 (in-cylinder pressure) in normal combustion. In FIG. 3, the solid line is the ion current, and the broken line is the combustion pressure. 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.

FIG. 4 shows the transition of the current measured via the ion current detection circuit for each location of abnormality in the internal combustion engine. In FIG. 4, the solid line represents the transition of the current measured when the fuel combustion is normal. On the other hand, a broken line is a transition of the current measured when the spark plug 12 is smoldered. When a conductive deposit such as carbon adheres to the smoldering of the spark plug 12, that is, the center electrode and / or the ground electrode of the spark plug 12, the insulation resistance between the two electrodes decreases, and the electrode is correspondingly burned during fuel combustion. The current flowing through increases. For this reason, the length of the period t ₁ in which the current measured at the time of one combustion in the cylinder 1 exceeds the threshold increases.

In FIG. 4, the chain line represents the transition of the current measured when the fuel combustion in the cylinder 1 is unstable or insufficient. If the combustion is unstable or insufficient, the amount of ions generated in the combustion chamber of the cylinder 1 is reduced, so that the current flowing through the electrode of the spark plug 12 is also reduced. Therefore, the length of time t ₂ the current is measured during one combustion in the cylinder 1 is greater than the threshold value is shortening. There are a number of factors that cause unstable or insufficient combustion. In some cases, a sufficient amount of fuel is not injected from the injector 11. In some cases, a problem occurs in the ignition coil 14 and other electrical circuits for spark ignition. In some cases, the spark discharge in the plug 12 is incomplete.

  However, even if the combustion of fuel is normal, it cannot be asserted that there is no abnormality in the internal combustion engine. For example, if the intake valve or the exhaust valve cannot be completely closed due to a foreign object being caught between the valve body of the intake valve or the exhaust valve and the valve seat, a part of the intake air is generated in the cylinder 1 in the compression stroke. Leakage into the intake port or exhaust port causes the intake air to become under-compressed, reducing the pressure in the cylinder 1 at the end of the compression stroke, and thus reducing the effective compression ratio. The reduction in the compression ratio decreases the rotational torque of the crankshaft that occurs in the expansion stroke. If the rotational torque is reduced, the rotation of the crankshaft will not be accelerated sufficiently.

  During the operation of the internal combustion engine, the ECU 0 repeatedly measures the current flowing through the electrode of the spark plug 12 for each cylinder 1 via the ion current detection circuit, and the current value based on the time series sets the threshold value. The length of the period that exceeds is measured. The length of this period is a material for determining whether fuel combustion in the cylinder 1 is normal or defective (including misfire).

  Note that when the ECU 0 stops the internal combustion engine when the ignition switch is turned off or the idle stop condition is satisfied, the magnitude of the current flowing through the electrode of the spark plug 12 is measured immediately before the stop. The length of the period during which the value exceeds the threshold or the time series itself of the measured value of the current flowing through the electrode of the spark plug 12 is stored in the memory and held.

  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 (N signal) b output from an engine rotation sensor that detects the rotation angle of the crankshaft and the engine speed, An accelerator opening signal c output from a sensor that detects the amount of depression of the accelerator pedal or the opening of the throttle valve 32 as an accelerator opening (so-called required load), and a brake that is output from a sensor that detects the amount of depression of the brake pedal Stepping amount signal d, intake air temperature / intake pressure signal e output from a temperature / pressure sensor for detecting intake air temperature and intake pressure in intake passage 3 (especially surge tank 33), water temperature sensor for detecting engine cooling water temperature Output from the cam angle sensor at a plurality of cam angles of the cooling water temperature signal f output from the intake camshaft or exhaust camshaft. A cam angle signal (G signal) g is the ion 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 of the spark plug 12, a fuel injection signal j is output to the injector 11, an opening operation signal k is output to the throttle valve 32, and the like.

  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.

  Further, the ECU 0 inputs a control signal l to a starter motor (cell motor, not shown) when starting the internal combustion engine (a cold start or a return from an idling stop). Cranking is performed by rotating the crankshaft by engaging the pinion gear of the motor with the ring gear on the outer periphery of the flywheel (in the case of MT vehicle) or drive plate (in the case of AT vehicle). Then, from the first explosion to the consecutive explosion, when the engine speed exceeds a determination value determined according to the cooling water temperature or the like, it is considered that the explosion has been completed, and the cranking is finished.

  FIG. 5 shows a procedure example of processing executed by the ECU 0 according to a program when the internal combustion engine is started. The ECU 0 starts cranking of the engine by the starter motor (step S2) when the ignition switch is operated to be turned on or when a condition for ending the idle stop and restarting the engine is established (step S1). At the same time, fuel is injected into each cylinder 1 and the air-fuel mixture is ignited (step S3).

  If the rotational speed of the crankshaft that has been started exceeds the judgment value (step S4), it is considered that the explosion has been completed, and the cranking of the engine is terminated (step S5).

  On the other hand, if the elapsed time from the start of cranking has exceeded a predetermined value without reaching a complete explosion (step S6), the internal combustion engine has failed to start and the starting process is stopped. That is, cranking, fuel injection, and ignition are stopped (step S7). In addition, the cause of the start failure of the internal combustion engine is estimated.

  As already described, the ECU 0 measures the length of the period during which the magnitude of the ionic current flowing through the electrode of the spark plug 12 during combustion exceeds the threshold, as measured during the most recent operation (before stopping) of the internal combustion engine, or The time series itself of the ionic current value flowing through the electrode of the spark plug 12 during combustion is stored and retained. The ECU 0 estimates the cause of the starting failure of the internal combustion engine based on the length of the period in which the ion current signal exceeds the threshold value, which is indicated by the stored information.

  Specifically, if the length of the period in which the ion current signal exceeds the threshold is greater (longer) than the high predetermined value (step S8), both of the spark plugs 12 due to smoldering of the spark plug 12 or the like. It is considered that the spark ignition is poor due to a decrease in resistance between the electrodes or a short circuit (step S9).

  Alternatively, if the length of the period during which the ion current signal exceeds the threshold is smaller (shorter) than the low predetermined value (step S10), it is presumed that it is caused by a cause other than smoldering of the spark plug 12. (Step S11). As a case corresponding to step S11, a necessary and sufficient amount of fuel is not injected from the injector 11, the in-vehicle battery is insufficiently charged, the electrode of the spark plug 12 is worn, and the liquid fuel is a spark plug. Possible problems include the so-called fogging of the plug 12 adhering to the 12 electrodes, or the failure of spark ignition due to the failure of the ignition coil 14 or other electrical circuit for spark ignition.

  If the length of the period during which the ion current signal exceeds the threshold value is smaller than the high predetermined value and larger than the low predetermined value, the combustion of the fuel in the cylinder 1 itself is almost normal. Seem. Nevertheless, it takes time to start the internal combustion engine because the air-fuel mixture leaks to the intake port or exhaust port during the compression stroke, the effective compression ratio decreases, and the rotational torque of the crankshaft is sufficient. It is inferred that it will not increase (step S12).

  Thus, the ECU 0 provides information (diagnosis code) for identifying whether the cause of the start failure of the internal combustion engine corresponds to the above-described steps S9, S11, or S12, the time stamp of the date and time at that time, and the like At the same time, it is written into the memory and stored (step S13). This information will help determine the cause of start-up failures in subsequent inspection and repair operations.

  In addition, the fact that there is a problem that hinders the start of the internal combustion engine is output in a manner appealing to the driver's vision or hearing (step S14). For example, a warning light (engine check lamp) installed in a cockpit of a vehicle is turned on, displayed on a display, or a warning sound is output from a buzzer or a speaker. In step S14, information for identifying the cause of the start failure of the internal combustion engine may be output together.

  In this embodiment, the control device 0 is capable of measuring the current flowing through the electrode via a circuit that detects the ionic current flowing through the electrode of the spark plug 12 during combustion, and starts the internal combustion engine that is stopped. If the start cannot be completed even after a predetermined time has elapsed since the start of the operation, the ion current measured through the circuit when the internal combustion engine was operated immediately before A control device 0 for an internal combustion engine is characterized in that an abnormal location in the internal combustion engine is estimated based on the length, and information indicating the estimation result is stored.

  According to this embodiment, it becomes possible to narrow down the cause of the start failure of the internal combustion engine, and it is possible to reduce the labor and time spent for analyzing the cause and repairing the internal combustion engine.

  In particular, in the case of a start failure of the internal combustion engine, it is easy to isolate and identify the cause of the start failure by estimating the current state of the internal combustion engine based on the latest past measurement results.

  In the case where the internal combustion engine is started and cannot be completed, the estimation process shown in FIG. 5 is also performed for the ion current signal flowing through the electrode of the spark plug 12 during cranking, and the internal combustion engine is operated immediately before. It is also conceivable to make a comprehensive judgment together with the result of the estimation process based on the ion current signal.

  The present invention is not limited to the embodiment described in detail above. For example, steps S8 to S12 are not necessarily performed all. Steps S10 to S12 may be omitted, or steps S8 and S9 may be omitted.

  In addition, the specific configuration of each unit, the processing procedure, and the like 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 15 ... Bias power supply part 16 ... Amplification part

Claims (1)

A control device for an internal combustion engine capable of measuring a current flowing through an electrode via a circuit for detecting an ionic current flowing through the electrode of a spark plug during combustion,
The magnitude of the ionic current measured through the circuit when the internal combustion engine was operating immediately before if the engine could not be completed even after a predetermined time had elapsed since the start of the internal combustion engine being stopped A control device for an internal combustion engine, wherein an abnormality location in the internal combustion engine is estimated based on a length of a period during which the value exceeds a threshold value.

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