KR101637521B1 - Misfire judging method to prevent mis-detection of fire of engine - Google Patents

Abstract

An object of the present invention is to provide a misfire judgment method for preventing false misdetection which can prevent erroneous detection on misdetection detection which is likely to occur in an idle section immediately after cold start of an internal combustion engine by an easy method, And it is an object of the present invention to provide a misfire detection method capable of reliably discriminating a specific operation state of an internal combustion engine and thus capable of properly detecting misfire. To this end, according to the present invention, there is provided a method of determining a misfire by using a misfire detection rate within a predetermined number of ignition times based on misfire information of a cylinder after an ignition stroke, comprising the steps of: reaching a counter for misfire judgment And the ignition timing retarding function is released before the split injection of the fuel and the ignition timing delay function are performed.

Description

[0001] The present invention relates to a misfire judging method for preventing misfire detection of an engine,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a misfire judgment method for an internal combustion engine, and more particularly to a misfire judgment method capable of preventing misfire detection in a gasoline direct injection internal combustion engine.

Recently, a gasoline direct injection (GDI) engine, which directly injects fuel into the combustion chamber, is widely used and developed as a vehicle engine.

In the GDI engine, when the intake valve is opened, air is sucked into the combustion chamber from the intake port and compressed by the piston, and fuel is directly injected from the engine to the high-pressure air. Using such a GDI engine, Since the fuel-air mixture layer is formed by spraying, the concentrated mixture can be obtained by concentrating the air and the fuel around the spark plug, so that the engine can be operated even at a very low air-fuel ratio and the wall wetting is advantageous compared to the conventional intake port injection. The GDI engine has been used in recent years because it enables precise control of the amount of fuel and thus improves fuel efficiency and performance.

That is, in the combustion chamber, the high-pressure air and the fuel in the spray state are mixed, the mixture reaches the spark plug and is ignited and ignited to obtain the driving force, and the exhaust gas burned when the exhaust valve is opened is discharged to the exhaust port , This GDI engine enables homogeneous combustion in which fuel is injected into the combustion chamber during the intake stroke to form a homogeneous mixture, thereby enabling ultra-lean burn operation.

In addition, it has the advantage of improving the fuel efficiency of the engine and reducing the emission of CO2.

In the GDI engine having such advantages, when the intake valve is opened in the intake stroke of the piston, air in the intake port is sucked into the combustion chamber and fuel is injected to the intake air. At this time, a mixer dispersed throughout the combustion chamber is formed, the mixer is ignited by the spark plug, and the mixer dispersed throughout the combustion chamber is homogeneously burned.

An injector is installed in such a GDI engine to inject fuel at high pressure into the combustion chamber. The injector of the GDI engine must inject the injected fuel into the combustion chamber without interfering with the peripheral portion, and the injector is installed at the boundary between the lay-out and the combustion chamber.

The injection port, which is opened at the end of the injector and through which the fuel is injected, opens into the combustion chamber. At this time, since high-pressure injection of fuel is essential, it must be injected into the combustion chamber without interference of peripheral parts.

However, because the injection port is forced to be exposed to the combustion chamber, carbon is accumulated or deteriorated in the vicinity of the injection port, because the vicinity of the injection port of the injector is exposed to the combustion gas at high temperature during the interference of the peripheral portion and the operation of the engine. As a result, there arises a problem that the flow rate of the fuel injected from the injector is lowered and the shape of the fuel spray is deteriorated. Therefore, the design shape in which the injector is installed at the combustion chamber interface determines the operating performance of the engine.

The GDI engine has advantages over the existing PFI (Port Fuel Injection) system in terms of output power and fuel efficiency. The GDI engine is improved in charging efficiency and knocking characteristic for the intake cooling effect by direct injection in the cylinder, And the engine performance is improved by about 3% by increasing the compression ratio by improving knock characteristics and increasing the high load efficiency by lowering the exhaust gas temperature. Particularly, in terms of reduction of exhaust gas (EM), the activation time (LOT: Light-Off Time) of the catalyst is reduced by the divided injection, thereby reducing the exhaust gas emissions, reducing the catalyst cost by reducing the exhaust gas, The combustion stability is improved by the stratification of the mixer through the split injection in the idle section immediately after the idle section (CH section: Catalyst Heating section), and thus the ignition timing delay increase (CH function enhancement) becomes possible and the exhaust gas temperature can be raised do.

However, in general, as the ignition timing of the engine is delayed, the exhaust gas temperature rises due to the completion of combustion at a later stage (based on the crank angle). On the other hand, engine anomalies (ER) In particular, the ER is getting worse, and the fact that the difference between the actual ER and the ER in normal combustion is not so large as the erroneous ER is getting worse.

In order to suppress the deterioration of the engine stability (ER), it is necessary to control the air-fuel ratio to be rich. However, since it increases the HC generation amount, it is a concept opposite to the ignition timing delay, Especially when there is a problem that the ER is misleading when the fuel having poor volatility such as High DI (Driveability Index) fuel is used and misfire is detected as misfire .

Since the actual misfire of the engine is an important factor that greatly affects the performance and stability of the engine, in particular, the exhaust gas emission amount and the catalyst damage, many devices and methods for detecting the misfire of the engine have been proposed in the art.

Furthermore, in recent years, the engine electronic control technology has been subject to the OBD II (On Board Diagnosis II) regulation, which requires a computer installed in a vehicle to identify and warn the user of information necessary for fault diagnosis, There is a need for a system and a method for detecting the increase and the possibility of damage to the catalyst.

Accordingly, there has been a demand for an engine misfire detection system and a detection method for determining whether a misfire occurs and a cylinder in which a misfire has occurred when a misfire has occurred in the engine cylinder, and restoring the state of the engine to normal.

When the misfire state in which the combustion in the cylinder is not performed normally due to the failure of the fuel injection device or the like occurs during the operation of the internal combustion engine, the exhaust gas characteristics of the internal combustion engine deteriorate. Accordingly, in Japanese Unexamined Patent Application Publication No. 2-30954, information corresponding to the number of revolutions is calculated based on a cycle for every predetermined crank angle corresponding to each cylinder of the engine, and the amount of change or the rate of change And the misfire state of the engine is detected based on the detected state. This detection method focuses on reducing the rotational speed (angular velocity) of the crankshaft due to the decrease in the torque output of the internal combustion engine when a misfire occurs in the cylinder, The occurrence of misfire is judged when the rotational speed change rate is lower than the discrimination reference value.

Japanese Patent Application Laid-Open No. 2-49955 discloses a method for correcting a deviation between a rotational angular velocity of an internal combustion engine and a rotational angular velocity of a single ignition as a reference angular velocity (discrimination reference value) calculated for each ignition interval in accordance with a combustion stroke in an internal combustion engine, That is, when misfire detection is performed based on the rotational fluctuation, misfire may not be accurately detected when accidental misfire occurs or misfire occurs at a rate of one revolution per several rotations. Therefore, in Japanese Patent Application Laid-Open No. 2-49955, the reference angular velocity, that is, the reference value for discrimination, is updated as necessary. However, when the internal combustion engine is operating in an operating state such as a sudden change in the load on the internal combustion engine, for example, in a decelerating state, or immediately after the ignition key is turned off, the angular acceleration (rate of change in rotational speed) Negative).

Therefore, if the crankshaft angular acceleration is below the discrimination reference value on the misfire detection threshold, the misfire detection is erroneously performed even though the misfire condition has not actually occurred. Further, when the vehicle is traveling on rough roads, the rotation of the output shaft of the internal combustion engine fluctuates, and it is likely to cause misidentification of misfire detection.

As another conventional engine misfire detection system and detection method that has been conventionally performed, there is a method in which, during an operation stroke in which the piston reciprocates between a top dead center (TDC) and a bottom dead center (BDC) The rotation period of the crankshaft is increased due to the reduction of the torque of the crankshaft. Therefore, there is a method of measuring the rotation period to measure whether or not the misfire occurs.

That is, the rotation rate of the crankshaft is used to calculate the variation rate of the engine rotation speed or the engine rotation cycle signal per predetermined crankshaft rotation angle. When the variation rate exceeds the predetermined reference value, it is determined that misfire has occurred.

In this case, the rate of change of the engine rotation period signal is generally expressed by a difference between the current measured value and the previous measured value or by a difference between the present measured value and the moving average value. In this method, the engine rotation period signal is expressed as a function of time There is a problem that it becomes difficult to analyze the variation rate at high speed rotation.

In order to overcome such difficulties, a method of interpreting an engine cycle signal as a frequency component magnitude and a phase angle by a discrete Fourier transform (DFT) instead of a function of time has been studied.

However, in order to adopt this method, a pre-calculated sine and cosine function table must be set and stored in a memory in the engine control device. In order to analyze the frequency components, a multiplication of the number of sensed engine revolutions, And a processing routine for calculation for phase discrimination are required. Therefore, there is a problem that the method is very complicated, the consumption of memory and the processing time of the routine become long.

In sum, all of the above-mentioned prior arts have a problem that when the fuel is poor in volatility such as High DI (Driveability Index) fuel, the ER becomes worse and misfire occurs before the misfire determining device reaches the counter for misfire determination. It is impossible to avoid the problem of misunderstanding.

The present invention has been made in view of the above-mentioned problems, and it is an object of the present invention to provide a fuel injection control device capable of preventing misdetection of misfire detection, which is likely to occur in an idle section immediately after cold start of an internal combustion engine, And to provide a judgment method.

Another object of the present invention is to provide a misfire detection method capable of reliably discriminating a specific operation state of an internal combustion engine that is liable to cause erroneous detection on a misfire detection, and accordingly capable of properly detecting misfire.

In order to achieve the above object, the present invention provides a method for determining a misfire by using a misfire detection rate as a misfire count within a predetermined ignition count based on misfire information of a cylinder after an ignition stroke, And the ignition timing retarding function is released before reaching the counter for the ignition timing.

Further, the release timing of the split injection and ignition timing retarding function (CH function) of the fuel is measured by counting the number of times the combustion instability is detected to be equal to or higher than the reference value by measuring the engine stability (ER) And releases the counter when the counter reaches a predetermined value or more.

The precondition for releasing the CH function by measuring the ER is applied to the case where the engine is restarted after a predetermined time has elapsed after the engine is turned off.

The elapsed time is preferably 6 hours or more.

Another prerequisite for measuring the ER and releasing the CH function is a cold start condition.

The cold start condition is 3 to 30 占 폚 based on the cooling water temperature.

And the cold start condition is within 30 seconds after the start of the engine.

And the arrival at the CH release counter is determined by the following equation.

CNT_CH = CNT_Misfire - reference value

Here, the misfire detection counter CNT_Misfire is an ECU data value set through EM test as a minimum value satisfying the OBD EM standard, and the reference value is a value set in consideration of a period in which the engine stability is secured after CH release.

If it is determined that the CH release counter has been reached, the CH function is canceled and the fuel amount / ignition timing control is executed for each engine RPM and load as set in the ECU data, and the ER is confirmed to be larger than the misfire reference value And if it is determined that the ER is smaller than the misfire detection counter CNT_Misfire, the control returns to the ER confirmation step, and if the ER is confirmed to be smaller than the misfire reference value, the misfire counter CNT Is reset to zero.

The present invention can suppress the occurrence of false alarms due to the use of crude fuel in the situation where the EM target value is achieved without the control of the rich air-fuel ratio causing the increase of EM (exhaust gas) or the reduction of the delay time of the ignition timing, In order to satisfy the regulation, it is impossible to completely secure the stability of the engine under all conditions. Therefore, it is possible to reduce the exhaust gas of the GDI engine through the provision of the control logic for preventing the false alarm even under the worst case.

1 is a flowchart of a misfire judgment method for preventing false misdetection of the GDI engine of the present invention.

A method for determining a misfire with a misfire detection rate within a predetermined number of ignition times based on misfire information of a cylinder after an ignition stroke, the method comprising the steps of: before reaching a counter for misfire judgment in an idle driving section (CH function) of the divided injection and ignition timing retarding function (CH function) of the fuel is controlled so that the engine stability (ER: Engine Roughness), and counts the number of times that the instability of the combustion is detected to be equal to or higher than the reference value, and releases it when the counter reaches a predetermined value or more.

Here, the precondition for releasing the CH function by measuring the ER is applied to the case where the engine is restarted after a certain time has elapsed after the engine is turned off, and the elapsed time is preferably 6 hours or more, Another precondition for measuring and releasing the CH function is preferably a cold start.

The temperature condition of the cold start is preferably 3 to 30 DEG C based on the coolant temperature, and the time period of the cold start is preferably 30 seconds after the start of the engine.

The arrival at the CH release counter is determined by the following equation.

CNT_CH = CNT_Misfire - reference value ------------ (expression)

Here, the misfire detection counter CNT_Misfire is an ECU data value set through EM test as a minimum value satisfying the OBD EM standard, and the reference value is a value set in consideration of a period in which the engine stability is secured after CH release.

If it is determined that the CH release counter has been reached, the CH function is canceled and the fuel amount / ignition timing control is executed for each engine RPM and load as set in the ECU data, and the ER is confirmed to be larger than the misfire reference value And if it is determined that the ER is smaller than the misfire detection counter CNT_Misfire, the control returns to the ER confirmation step, and if the ER is confirmed to be smaller than the misfire reference value, the misfire counter CNT Is reset to zero.

Hereinafter, the operation flow of the present invention will be described in more detail with reference to the flowchart of FIG.

When the engine is started, the ECU confirms whether the step meets the precondition in step 1. It is determined whether there is no ECU-related error and whether or not a predetermined time, for example, 6 hours or more, Based on the input information from the cooling water temperature sensor, it is determined whether the cooling water temperature corresponds to the cold start state between 3 and 30 占 폚. If the three conditions are not satisfied, ER (Engine Stability), and determines whether the ER is larger than the misfire reference value (Step B).

Here, ER is calculated and measured by the ECU using the angular speed difference of the engine, and the actual reference value is determined by using the reference value pre-inputted to the ECU by obtaining the ER in a state in which the actual engine has caused the misfire. If the ER is smaller than the misfire reference value, the normal combustion state is recognized and the counter is maintained. If the ER is larger than the misfire reference value, the misfire counter is incremented (CNT = CNT + 1) (Step D), it is determined whether or not the CH control period is within 30 seconds after the engine is started (step E), and if it is within 30 seconds after the start of the CH control period in the step bar, it is judged whether or not the CH release counter reaches CNT_CH .

Here, CNT_CH = CNT_Misfire-reference value is a value set in the ECU in consideration of a period during which engine stability is secured after CH release, and the misfire detection counter CNT_Misfire is a minimum value satisfying the OBD EM standard Is the ECU data value set by EM test in advance.

If the CH release counter has not reached the CNT_CH in the above step, if the CH release counter reaches the CNT_CH, the control of the fuel amount and the ignition timing set for the engine RPM, the engine load, (Step A), the ER is re-checked in the step, and it is confirmed whether the ER is larger than the misfire reference value (step difference), the misfire counter is reset (CNT = 0) If the ER is larger than the misfire reference value, it is judged that the actual misfire has occurred (stepping), and it is determined whether the misfire counter is larger than the misfire detection counter (CNT_Misfire: data value input to the ECU) If the answer is Yes, the misfire warning lamp is turned on (stepped) to alert the driver of the misfire occurrence and return.

If it is not within 30 seconds after the startup in the step bar, the process proceeds to step S30.

As described above, the present invention monitors the ER in the CH, counts the number of times that this value is sensed above the reference value, and releases the CH function (fuel split injection and ignition timing delay) Similarly, the procedure for determining the misfire is determined by determining the number of times that the ER value is equal to or greater than the reference value, thereby releasing the CH function first before reaching the counter for the misfire determination.

Claims (9)

A method for determining a misfire with a misfire count within a predetermined number of ignition times based on misfire information of a cylinder after an ignition stroke, the method comprising the steps of: And the ignition timing delay function (CH function) is canceled by measuring the engine stability (ER) at the time of cold idling of the engine, Wherein the number of times the instability is detected to be equal to or greater than the reference value is counted and the counter is released when the counter reaches a predetermined value or more. delete 2. The method according to claim 1, wherein the precondition for releasing the CH function by measuring the ER is applied when the engine is restarted after a predetermined period of time has elapsed after the engine is turned off. Misfire determination method. 4. The misfire determining method for preventing false misdirection of an engine according to claim 3, wherein the elapsed time is 6 hours or more. The misfire determination method according to claim 1, wherein the precondition for releasing the CH function by measuring the ER is a cold start state. 6. The misfire determination method according to claim 5, wherein the cold start condition is 3 to 30 占 폚 based on coolant temperature. The misfire determination method for preventing misfire detection of an engine according to claim 5, wherein the cold start condition is within 30 seconds after the engine is started. The misfire determining method according to claim 1, wherein the arrival to the CH release counter is determined by the following equation.
CNT_CH = CNT_Misfire - reference value
Here, the misfire detection counter CNT_Misfire is an ECU data value set through EM test as a minimum value satisfying the OBD EM standard, and the reference value is a value set in consideration of a period in which the engine stability is secured after CH release. 9. The method according to claim 8, wherein when it is determined that the CH release counter has been reached, the CH function is canceled and the engine RPM and the fuel amount / ignition timing control set for each load are executed as set in the ECU data, If it is determined that the count value CNT is larger than the reference value, the control unit 20 determines whether the count value CNT is larger than the misfire detection counter CNT_Misfire. Otherwise, it returns to the ER confirmation step. If Yes, the misfire warning light is turned on. And when it is detected, the misfire counter (CNT) is reset to zero.

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