JP6446341B2 - Control device for internal combustion engine - Google Patents

Description

The present invention relates to an abnormality detection device for a fuel cut function during fail-safe operation of an internal combustion engine.

  In general, when a control device for an internal combustion engine detects a component affecting torque or a control abnormality / failure, it notifies the driver of the abnormality of the internal combustion engine with a warning lamp, fixes the throttle opening, and cuts the fuel. It is known to perform a fail-safe function such as ignition cut. However, when the fail-safe function does not normally operate, it is not confirmed that the fail-safe function operates normally, and when the vehicle falls into the fail-safe state with the fail-safe function broken, an abnormally high torque It is important to confirm that the fail-safe function operates normally.

  Conventionally, as a technique for detecting the abnormality of the fuel cut function at the time of fail-safe described above, a period for diagnosing the fuel cut function at the time of fail-safe while the operation of the internal combustion engine is stopped (for example, before starting the internal combustion engine) A method of performing abnormality diagnosis of the fuel cut function at the time of failsafe by providing a fuel cut function at the time of failsafe and monitoring the output level of the output port of the fuel injection device driver is known (for example, patent document) 1).

JP 2009-127574 A

  However, although the configuration of Patent Document 1 includes a normal fuel cut function and a fail-safe fuel cut function, it may not be possible to determine which function is faulty. Further, since the fail-safe fuel cut function is diagnosed before the internal combustion engine is started, the failure of the fail-safe fuel cut function cannot be detected during operation of a vehicle that is highly likely to actually fail. Further, the diagnosis method only monitors the output level of the output port of the fuel injector driver described above. For example, when the function of monitoring the output level of the output port fails, the failure may not be detected correctly.

  The present invention has been made in view of such problems, and the object of the present invention is to diagnose that the fail-safe fuel cut function is operating correctly before falling into fail-safe. In addition, it is possible to determine whether the fuel cut function during normal operation or the fuel cut function during fail safe is an abnormality or failure, and further it is possible to detect a failure during operation. To provide an apparatus.

  In order to achieve the above object, the internal combustion engine is provided with a normal fuel cut function and a fail safe fuel cut function that operates when an abnormality occurs, and is mounted to detect an operating state and a control state of the internal combustion engine. When a fuel cut determination for forcibly stopping fuel injection is made based on the various sensors, a normal fuel cut diagnosis unit for diagnosing the normal fuel cut function is provided, and this normal fuel cut is determined to be normal. In this case, a test determination unit for determining whether or not to perform the fail-safe fuel cut diagnosis from the results of the fuel cut determination and the normal fuel cut diagnosis is provided. When the test execution determination is made, the fail-safe fuel cut execution unit is forcibly operated, and the diagnosis of the fail-safe fuel cut function is output from the drive voltage of the fuel injection device and the A / F sensor or O2 sensor. And / or a voltage output from the knock sensor. As a result, it is possible to detect a failure in the normal fuel cut function and the fail-safe fuel cut function.

  According to the present invention, it is possible to confirm that the fuel cut function at the time of fail safe operates normally before the vehicle falls into fail safe.

The example of whole structure of the internal combustion engine by which the control apparatus of this invention is mounted. An example of a control block diagram of the present invention. The flowchart example which showed the timing which implements fuel cut function diagnosis at the time of fail safe. Timing chart example showing that the fuel cut function diagnosis is performed at the time of key safe when fail-safe. An example of the circuit diagram which showed the means to detect a drive voltage. The timing chart example which showed the voltage characteristic of the drive voltage at the time of energization of a fuel-injection apparatus, and the voltage characteristic at the time of interruption | blocking. The timing chart example which showed the sensor value of the A / F sensor, and the sensor value of the A / F sensor during fuel cut. The flowchart example which showed the diagnostic method by the A / F sensor of the fuel cut function at the time of a fail safe. The timing chart example which showed the sensor value of the knock sensor and the sensor value of the knock sensor during fuel cut. The flowchart example which showed the diagnostic method by the knock sensor of the fuel cut function at the time of a fail safe.

  Embodiments according to the present invention will be described below with reference to the drawings.

  FIG. 1 shows an overall configuration of a control system for an internal combustion engine 101 according to the present embodiment. In the general system, the opening degree of the intake valve 123 is controlled in accordance with the input parameters of the ECU 111 such as the driver's accelerator operation signal 118 and the brake operation signal 119, so that the air is drawn into the cylinder 107 through the collector 120 and the intake pipe 106. The intake air amount is controlled, the intake air amount is measured by the airflow sensor 122, and the intake air amount is output to the ECU 111.

  In addition, a fuel injection device 102 that directly injects fuel into the cylinder and an ignition device 103 that performs ignition are provided. By opening the intake valve 105 with a cam 104, the air taken into the cylinder 107 from the intake pipe 106 and the above-mentioned The mixed air mixed with the fuel injected from the fuel injection device 102 is ignited by the ignition device 103 to cause an explosion in the cylinder 107 and output torque to the crankshaft as the driving force of the vehicle.

  At this time, the fuel to be injected is subjected to fuel injection control by the ECU 111 from the fuel injection device 102 and injected at a controlled amount and timing, and the injected fuel is similarly subjected to ignition control by the ECU 111 and controlled. Is ignited by the ignition device 103 at the determined timing.

  The ECU 111 includes a driver's accelerator operation signal 118, a brake operation signal 119, a cam angle sensor 114 attached to detect the angle of the cam 104, and a crank angle attached to detect the rotational speed of the internal combustion engine. A sensor 115, a water temperature sensor 101 attached to the cylinder 107 or the like for detecting the cooling water temperature of the internal combustion engine, a knock sensor 113 attached to the cylinder 107 or the like for detecting knocking due to abnormal combustion, The fuel injection control and the ignition control of the internal combustion engine are performed based on other input parameters.

  The exhaust gas after the explosion passes through the exhaust pipe 109 after the exhaust valve 108 is opened, and is exhausted outside the vehicle after removing harmful gas in the exhaust gas by the catalyst 110. At this time, the harmful gas in the exhaust gas is detected by the A / F sensor 116 and the O2 sensor 117 attached to the front and rear of the catalyst 110, and the detection signal is output to the ECU 111.

  FIG. 2 shows an embodiment of the control block diagram of the present invention. In the present invention, a CPU 209, a ROM 213, and a RAM 214 are provided in the ECU 111. The ROM 213 is a nonvolatile memory that stores in advance a control program for the internal combustion engine executed by the CPU 209 and various setting data. The RAM 214 is a volatile memory that temporarily stores data when the CPU 209 executes a program of the internal combustion engine to perform various operations. The CPU 209 executes a program of the internal combustion engine stored in the ROM 213, and the above-described fuel injection control and ignition control output an ignition control signal to the ignition circuit 211 based on various sensor values received from the input circuit 210. This is realized by outputting a fuel injection control signal to the fuel injection device drive circuit 212.

  Further, the CPU 209 is provided with a normal fuel cut request calculation unit 205 that sets the fuel injection amount to 0 when there is a need to cut the fuel according to a request from the driver or the vehicle (fuel cut request). A normal fuel cut request is output to the fuel injection amount calculation unit 207 that determines the fuel injection amount based on the operation signal 118, the brake operation signal 119, and other input parameters from the input circuit 210. When there is a normal fuel cut request, the fuel injection control signal calculated by the fuel injection amount calculation unit 207 is output as 0 to the fuel injection device drive circuit 212, thereby realizing normal fuel cut.

  On the other hand, the CPU 209 is provided with an abnormality determination unit 203 that determines whether a vehicle control or system abnormality has occurred. When the abnormality determination unit 203 determines that an abnormality has occurred, the fuel injection device is forcibly stopped. A fail-safe fuel cut execution unit 202 for calculating a signal is provided. When vehicle control or system abnormality occurs, the fuel injection drive circuit 212 is forcibly turned off from the fuel cut execution unit 202 at the time of fail safe, thereby realizing fuel cut at the time of fail safe.

  Then, the CPU 209 correctly executes the normal fuel cut diagnosis unit 206 for confirming whether the above-described normal fuel cut request calculation unit 205 performs the calculation and the fail safe fuel cut execution unit 202 described above. A fail-safe fuel cut diagnosis unit 201 for checking whether or not a fail-safe fuel cut diagnosis execution determination unit 204 for determining whether or not to perform a fail-safe fuel cut diagnosis is provided.

  When there is a normal fuel cut request, the normal fuel cut diagnosis is performed, and the normal fuel cut request and the normal fuel cut diagnosis result are output to the fail-safe fuel cut diagnosis execution determination unit 204. The normal fuel cut function (normal fuel cut means) may be diagnosed by a diagnostic method shown in FIGS. As a result of the normal fuel cut diagnosis, when the fail-safe fuel cut diagnosis execution determination unit 204 determines that the fail-safe fuel cut diagnosis is to be performed, switching to the fuel cut by the fail-safe fuel cut execution unit 202 is preferentially switched. (At this time, the normal fuel cut request calculation is not performed), and the fuel cut diagnosis at the time of fail-safe is performed.

  The fuel-safe diagnosis at the time of fail-safe is performed by an abnormality detection method using a drive voltage 208 of a fuel injection device, which will be described later with reference to FIG. This method is realized by a method and an abnormality detection method using a voltage from the knock sensor 113 described later with reference to FIG.

  FIG. 3 is an example of a flowchart illustrating the execution timing of the fail-safe fuel cut diagnosis. In S101, it is determined whether there is a fuel cut request. After determining that the normal fuel cut flag is ON, in S102, the normal fuel cut flag is set to ON (normal fuel cut request calculation unit 205), and in S103. A normal fuel cut is performed (fuel injection amount calculation unit 207), and a normal fuel cut diagnosis (normal fuel cut diagnosis unit 206) is performed in S104. Even if it is determined in S101 that there is no fuel cut request, if it is determined in S115 that there is a key-off time, the normal fuel cut is forcibly executed and the normal fuel cut diagnosis is performed. Although not particularly described in the present invention, the normal fuel cut diagnosis in S103 may be performed by an abnormality detection method described later with reference to FIGS. After the normal fuel cut function (normal fuel cut means) is determined to be abnormal in S105, it is switched to the fail safe fuel cut function (fail safe fuel cut means) to warn the driver of the abnormality. An hour fuel cut abnormality process S112 is performed.

  If it is determined normal in S105, the normal fuel cut flag is turned OFF in S106, the fail safe fuel cut flag is turned ON in S107, and the fuel is switched to fail safe fuel cut in S108. Subsequently, in S109, the fail-safe fuel cut diagnosis is performed using an abnormality detection method described later with reference to FIGS. If it is determined in S110 that the fail-safe fuel cut function (fail-safe fuel cut means) is abnormal in S109, the fail-safe fuel cut is stopped in S111, the fuel cut is switched to the normal fuel cut, and a warning light is displayed in S110. The driver is notified of the abnormality by turning on.

  Switching between the normal fuel cut diagnosis and the fail safe fuel cut diagnosis in this way is performed after the ECU determines the abnormality of the basic configuration of the ECU, and then performs the newly provided fail safe fuel cut diagnosis. It is possible to determine which of the function (normal fuel cut means) and the fail safe fuel cut function (fail safe fuel cut means) is failed. Further, since the fuel cut means at the time of fail-safe is diagnosed when there is a fuel cut request, it is possible to make a diagnosis without affecting the drivability without being noticed by the driver.

  In addition, the diagnosis result is stored in, for example, a nonvolatile ROM, and after it is determined as NG in both the normal and fail-safe diagnoses, it is determined that the vehicle drivability is significantly affected, and the intake valve is immediately Fail safe S112 which closes 123 is implemented and a vehicle is stopped safely.

  FIG. 4 shows an example of a timing chart regarding the execution timing of the fail-safe fuel cut diagnosis at the time of key-off according to claim 4. At timing a when it is determined that the key has been turned off, the normal fuel cut flag is turned ON, and the process proceeds to the flowchart of FIG. After it is determined that the normal fuel cut is normal at the timing b shown in the figure, the F / S fuel cut diagnosis execution determination unit 204 switches the fail-safe fuel cut flag to ON, and the fail-safe fuel cut diagnosis 201. I do. At this time, the determination result of the fail-safe fuel cut diagnosis 201 is stored in, for example, a nonvolatile ROM, and the result is referred to at the next operation. In this way, even if there is no opportunity to cut fuel while driving, a diagnosis will always be made once when the vehicle stops, so the fuel cut function at the time of fail-safe (fail-safe time) It is possible to inform the driver of the failure of the fuel cut means.

  Next, the fail-safe fuel cut diagnosis method using the drive voltage of the fuel injection device will be described with reference to FIGS.

FIG. 5 shows an embodiment of a simple circuit configuration diagram of the present invention. The ECU 111 includes a voltage detection unit 303 that detects a drive voltage of the fuel injection device 102 . It actuates the fuel injection device 102 in the driving circuit 212 by the microcomputer 301, detects the driving voltage of the fuel injector 102 by the voltage detection unit 303.

Next, FIG. 6 shows a timing chart example of the drive voltage 208 of the fuel injection device that can be detected by the circuit configuration described above. The upper part of FIG. 6 shows the response of the drive voltage 208 of the fuel injection device when the fuel injection command is issued. First, after the injection command pulse 12a rises at the timing a, the drive voltage 208 of the fuel injection device approaches the GND side. After the injection command pulse 12a falls at the timing b, the back electromotive force is caused to the timing c until the magnetic flux is not lost by the self-induction action of the fuel injection device 102 .

  On the other hand, the lower part of FIG. 6 shows the response of the fuel injection device drive voltage when the fuel cut flag 11a which is a fuel cut request is ON by the normal fuel injection amount calculation unit 205. Compared to the upper diagram, the fuel injection is being cut and the injection command pulse 11a does not rise. Therefore, the drive voltage 208 of the fuel injection device always shows a constant value.

  When an abnormality occurs during the fuel cut, it is considered that the drive voltage 208 of the fuel injection device described above varies. Therefore, when the drive voltage 208 of the fuel injection device exceeds the threshold value A at the timing b, for example, the fuel injection device drive voltage for a predetermined time (for example, a section from b to c) is sampled, and the average value of the voltage values is predetermined. If it is equal to or greater than the value, it can be determined that the fuel has been injected, so an abnormality is determined.

  Next, the fail-safe fuel cut diagnosis method using the A / F sensor according to claim 7 will be described with reference to FIGS.

  FIG. 7 shows a timing chart example of the A / F sensor value at the normal time and the A / F sensor value at the time of fuel cut. The upper part of FIG. 7 shows the response of the A / F sensor value after the catalyst is activated except when the fuel is cut. In an internal combustion engine, the fuel injection amount is normally controlled so that A / F becomes the stoichiometric air-fuel ratio.

  On the other hand, the lower part of FIG. 7 shows the response of the A / F sensor value during fuel cut. It is known that the A / F sensor value shifts to the lean side after the fuel cut flag 11a rises at the timing a as compared to the upper diagram. After sticking to the upper limit of the A / F sensor value from the section b and then canceling the fuel cut request, it shifts to the rich side in order to burn the fuel.

  FIG. 8 shows a flowchart example of the fuel cut diagnosis at the time of fail-safe using the characteristics of FIG. 7 described above. First, in S201, A / F sensor activation determination is performed. If it is not activated, diagnosis is not performed even during fuel cut and the routine is exited. After determining that it is activated, ST initialization processing is performed in S202, and ignition control is started in S203. Next, in S204, it is determined whether a predetermined time has elapsed. If not, the A / F sensor value is read in S205 (that is, the A / F sensor value is sampled for a certain time). Subsequently, the average value of the read A / F sensor values S is calculated in S206, and it is determined whether ST has elapsed in S204. After the timer ST has passed a predetermined time, the average value calculation of the A / F sensor value S is terminated, and it is determined in S208 whether the average value is equal to or greater than a predetermined value. At this time, if the average value S is larger than the predetermined value, it can be determined that the A / F sensor has fallen to the lean side, so that it is determined in S209 that no fuel is injected and the fuel cut function is operating normally. . If it is determined in S208 that the average value of the A / F sensor is equal to or less than the predetermined value, it can be determined that fuel has been injected due to some failure / abnormality and has been ignited by the ignition control. Is determined to be abnormal. Finally, in S210, it is determined whether diagnosis has been performed for all cylinders. If diagnosis for all cylinders has not been completed, diagnosis is performed again from S202.

  Although not described in the example of the flowchart of FIG. 8, when the fuel cut flag falls during the main diagnosis, the diagnosis is immediately stopped.

Next, with reference to FIG. 9 and 1 0, and claim 5 using a knock sensor according to claim 6, illustrating a fuel cut diagnostic method when the fail-safe.

  FIG. 9 shows a timing chart example of each vibration (sound) during normal combustion and each vibration (sound) during fuel cut, which can be detected by the knock sensor. In the upper diagram of FIG. 9, after the fuel injection command pulse rises, the valve opening sound of the fuel injection device is detected by the knock sensor, and after the fuel injection command pulse falls, the valve closing sound of the fuel injection device is detected by the knock sensor. Is detected. Further, it is known that a knock sensor detects ignition noise that performs ignition in a compression process after valve closing, knocking noise that is abnormal combustion, and valve opening and closing sound that sucks and exhausts air in the cylinder.

  On the other hand, the lower part of FIG. 9 shows the response of the knock signal during the fuel cut. Since the fuel is being cut as compared with the upper diagram, the above-described opening / closing valve sound, ignition noise, and knocking sound of the fuel injection device are not detected, but only the valve opening / closing valve sound is detected. Here, since it is known that knocking and various noises are basically different from each other although the frequency band partially overlaps, section knocking in the period ab in which normal fuel is injected from the timing a when the fuel cut flag rises is known. Sampling the signal, analyzing the frequency of the sampled signal result, and comparing the frequency analysis result with the frequency intensity of the opening / closing valve sound of the fuel injection device stored in advance, thereby opening and closing the fuel injection device during fuel cut It is possible to confirm whether or not a valve sound has occurred, and to detect an abnormality in the fuel cut function.

  FIG. 10 shows a flowchart example of the fuel cut diagnosis at the time of fail-safe using the characteristics of FIG. 9 described above. First, in step S301, the timer ST is initialized. Thereafter, the value of the knock signal is sampled in S302, and after it is determined in S303 that the timer ST has passed a predetermined time, frequency analysis is performed in S304. At this time, as described above, during the fuel cut, only the valve opening / closing valve sound is generated, and the frequency band is partially overlapped but is basically different. A plurality of intensities at frequencies in the frequency band f1 to f8 of the opening / closing valve sound of the fuel injection device are extracted, and it is determined at S305 whether or not the valve is opened / closed during the knock sensor signal sampling process from the signal of the crank angle sensor 115 at S306. If it is determined that the valve is opened / closed, the valve opening / closing frequency intensity stored in advance in the frequency band f1 to f8 in S307 is removed from the frequency intensity of the fuel injection device analyzed in S304 as noise. To do. After that, when the difference between the frequency intensity of the fuel injection device stored in advance in S308 is larger than a predetermined value, it is determined that the fuel is not injected, and it is determined that the fuel cut is normally performed. Finally, it is determined in S311 whether or not all cylinders have been diagnosed. If all the cylinders have not been diagnosed, the diagnosis is performed again from S301.

Hereinafter , an example of a flowchart of the fuel cut diagnosis at the time of fail-safe is shown. First, in step S301, the timer ST1 is initialized. Thereafter, the value S of the knock signal is read in S302, and it is determined whether the knock sensor value S is larger than the threshold A in S303. If it is determined in S305 that the knock sensor value is smaller than the threshold A until the timer ST1 elapses for a predetermined time, there is no valve opening or closing sound of the fuel injection device described above, and fuel is not being injected, It is determined that the fuel cut function is normal.

  On the other hand, if knock sensor value S exceeds threshold value A in S303, it is determined that there is a possibility that noise due to the above-described combustion operation has occurred, timer ST2 is initialized in S304, and then timer ST2 passes until a predetermined time elapses. In step S307, the knock sensor value S is sampled. If the integration value ΣS of the knock sensor is larger than the predetermined value B in S310 when the integration is completed after the predetermined time has elapsed after the timer ST2 has elapsed in S308 during the sampling period, Therefore, it can be determined that a failure / abnormality has occurred in the fail-safe fuel cut function. Finally, in S312, it is determined whether diagnosis has been performed for all cylinders. If diagnosis for all cylinders has not been completed, diagnosis is performed again from S301.

DESCRIPTION OF SYMBOLS 101 Internal combustion engine 102 Fuel injection apparatus 103 Ignition apparatus 106 Intake pipe 107 Cylinder 109 Exhaust pipe 111 Engine control unit (ECU)
113 Knock sensor 114 Cam angle sensor 115 Crank angle sensor 116 A / F sensor 117 O2 sensor 118 Accelerator 119 Brake 120 Collector

Claims (7)

A normal fuel cut means for setting the fuel injection amount by the fuel injection device to zero when the output torque of the internal combustion engine is not required, such as when a deceleration operation by the vehicle or the driver is performed,
Fail-safe fuel cut means for performing fail-safe for forcibly stopping the fuel injection device when an abnormality occurs in a vehicle device or system; and
A normal fuel cut diagnosis means for detecting a failure of the normal fuel cut means;
After the normal fuel cut diagnostic means has confirmed that the normal fuel cut means is normal, and during the fail safe diagnosis possible period when fuel injection by the fuel injection device is not required, the fail safe When the fuel injection detecting means that activates the fuel cut means and detects whether or not the fuel is supplied from the fuel injection device is determined that the fuel has been supplied, the fail-safe fuel cut means has failed. A control device for an internal combustion engine, comprising fail-safe function diagnosis means for determining Control apparatus for an internal combustion engine according to claim 1, wherein the said failsafe function diagnosis means after the passing constantly fuel cut, characterized in that for diagnosing a failure of the fuel cut means when the fail-safe. After said key Ofu failsafe function diagnosis means control apparatus for an internal combustion engine according to claim 1, wherein the diagnosing faults in a fuel cut means when the fail-safe. Drive voltage measuring means for measuring the drive voltage of the fuel injection device;
The fuel injection detecting means samples the drive voltage measured by the drive voltage measuring means for a predetermined time at the time of fail-safe function diagnosis, and if the average value obtained by the sampling is equal to or greater than a predetermined value 2. The control apparatus for an internal combustion engine according to claim 1, wherein it is determined that fuel is being injected. The internal combustion engine includes a knock sensor capable of detecting vibration such as knocking generated in the internal combustion engine,
The fuel injection detection means samples the detection value of the knock sensor in a predetermined operation state for a predetermined time, and then calculates a plurality of valve opening sounds and valve closing sounds of the fuel injection device from the values obtained by the sampling. Frequency comparison means that extracts the frequency intensity of the frequency band and compares it with the frequency intensity of the injection device stored in advance during normal fuel injection, and injects fuel if the frequency comparison result is within a predetermined range The control apparatus for an internal combustion engine according to claim 1, further comprising:   If the valve opening / closing determination is made during the sampling, the frequency comparing means removes the frequency intensity of the valve opening / closing noise stored in advance in a plurality of frequency bands from the frequency intensity of the fuel injection device at the time of fuel injection. The control apparatus for an internal combustion engine according to claim 5. The internal combustion engine includes an ignition device that performs ignition, and an A / F detection unit that detects an air-fuel ratio,
The fuel injection detection means performs ignition by the ignition device, and samples the A / F value detected by the A / F detection means for a predetermined time, and the value obtained by the sampling is equal to or less than a predetermined value. 2. The control apparatus for an internal combustion engine according to claim 1, wherein it is determined that fuel is being injected.

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