JP2010112244A - Control device and control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control device and a control method causing misfire only to a cylinder with a defective air-fuel ratio by determining the abnormality of the air-fuel ratio of an internal combustion engine based on the calculated value of an air-fuel ratio F/B control and, when determining that the air-fuel ratio is abnormal, by shortening a fuel injection time for injecting fuel into each cylinder in increments of a predetermined time. <P>SOLUTION: The engine 1 can determine the cylinder with an abnormal air-fuel ratio by an air-fuel ratio abnormality determination treatment and an air-fuel ratio abnormal cylinder specifying treatment and, when determining that the abnormal air-fuel ratio occurs, can specify the cylinder with an abnormal air-fuel ratio by shortening the fuel injection time for injecting fuel into each cylinder in increments of the predetermined time. Since the cylinder of the multi-cylinder engine in which the abnormality of the air-fuel ratio occurs can be quickly specified, the air-fuel ratio can be early corrected to the target air-fuel ratio by correcting the fuel injection amount injected into the cylinder in which an abnormality occurs. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a control device and a control method.

  Feedback for executing combustion by controlling the air-fuel ratio of the internal combustion engine under various load conditions to be close to the target air-fuel ratio for the purpose of improving the fuel efficiency of the vehicle and improving the exhaust emission (hereinafter referred to as F / B). Control) is widely applied.

  In the F / B control, for example, an air-fuel ratio (hereinafter abbreviated as (A / F)) sensor for detecting the air-fuel ratio of exhaust gas discharged from the internal combustion engine and oxygen are provided upstream and downstream of the purification catalyst. A concentration (hereinafter abbreviated as (O2)) sensor is provided (see FIG. 4), and the fuel injection amount is feedback controlled so that the engine ECU (Electronic Control Unit) has a target air-fuel ratio based on these detection results. is doing.

  That is, the air-fuel ratio of the air-fuel mixture in the cylinder is grasped from the detection result of the A / F sensor upstream of the catalyst, and the first correction coefficient for correcting to the air-fuel ratio required in the current load state is calculated, Main air-fuel ratio F / B control for adjusting the fuel injection amount from the injector based on the first correction coefficient is executed. Further, in addition to the main air-fuel ratio F / B control, the second correction coefficient is calculated based on the detection result of the O2 sensor downstream of the catalyst, and the first correction coefficient obtained by the main air-fuel ratio F / B control is corrected. Sub air-fuel ratio F / B control is executed. By executing such sub air-fuel ratio F / B control, the catalyst in which the oxygen concentration is in an equilibrium state by sufficiently stirring the air-fuel ratio error based on the variation in the output characteristics of the A / F sensor upstream of the catalyst. Since the correction can be made based on the air-fuel ratio detected by the O2 sensor from the downstream exhaust gas, the accuracy of the air-fuel ratio control can be further improved.

  However, according to the above F / B control, for example, when the fuel injection amount of an injector of a certain cylinder decreases due to the injection hole clogging, etc., and the air-fuel ratio between the cylinders does not match, that is, an imbalance state occurs. Abnormality occurs in the combustion of the cylinder, and a large amount of hydrogen is discharged as exhaust gas. When the A / F sensor upstream of the catalyst detects this large amount of hydrogen, the A / F sensor detects an air-fuel ratio value that is shifted to a richer side than the actual air-fuel ratio and transmits it to the engine ECU. Therefore, based on the detection result shifted to the rich side from the actual air-fuel ratio, the engine ECU determines that the fuel injection amount into the cylinder is excessive, and decreases the fuel injection amount to bring the air-fuel ratio to the lean side. The main air-fuel ratio F / B control to be controlled is executed. In this case, excessive lean control by the main F / B control works to deteriorate exhaust emission, and a large amount of NOx is discharged as exhaust gas.

  Further, since the hydrogen in the exhaust gas generated in the imbalance state is combusted by the purification catalyst, the O2 sensor downstream of the catalyst moves to the lean side by the correct air-fuel ratio, that is, the main air-fuel ratio F / B control. A controlled air-fuel ratio is detected. Therefore, the engine ECU executes the sub air-fuel ratio F / B control to correct the air-fuel ratio deviated from the target air-fuel ratio to the lean side based on the detection result of the O2 sensor. At this time, the average value of the calculation result of the sub air-fuel ratio F / B control is an abnormally larger value than the normal value (within 2%) in order to correct the air-fuel ratio shifted to the lean side to the target air-fuel ratio. Therefore, it is possible to detect that the air-fuel ratio between the cylinders is in an imbalance state. However, although it can be detected from the calculation result of the sub air-fuel ratio F / B control that the air-fuel ratio between the cylinders is in an imbalance state, it is difficult to identify the cylinder in which the air-fuel ratio is abnormal. is there. Therefore, there is a problem that the air-fuel ratio of the cylinder that causes the imbalance state cannot be corrected quickly.

  In order to solve such a problem, when the misfire is determined based on the exhaust gas temperature or the detection value of the air-fuel ratio sensor, the fuel supply to all the cylinders is cut to suppress the increase in the exhaust gas temperature. On the other hand, Patent Document 1 discloses a technique for identifying a misfired cylinder by sequentially canceling the fuel cut for each cylinder.

  Patent Document 2 discloses a technique for determining combustion abnormality of each cylinder from the degree of change in angular velocity detected by the engine rotation sensor and switching the combustion method to homogeneous combustion only for the cylinder determined to have abnormality in combustion. Yes.

  Further, the exhaust gas temperature from each cylinder is sequentially measured and stored by a temperature sensor, and a cylinder in which a combustion abnormality has occurred is detected based on the difference between the stored exhaust gas temperature data and the current exhaust gas temperature. The technique is disclosed in Patent Document 3.

  Further, based on the detection value of the rear oxygen sensor and the catalyst passing gas flow rate value, it is recognized that an air-fuel ratio deviation has occurred in any of the cylinders, and the time for passing through the compression process of each cylinder is measured to determine the frequency. Patent Document 4 discloses a technique for identifying a cylinder in which an air-fuel ratio shift has occurred by analysis.

JP 2000-248989 A JP 2004-245185 A JP 2005-299449 A JP 2008-005103 A

  However, the technique of Patent Document 1 has a problem that the output of the internal combustion engine is reduced by cutting the fuel injection into the cylinder and detecting the combustion abnormality. Further, the technique of Patent Document 2 has a problem that it is difficult to accurately detect a cylinder in which the air-fuel ratio becomes slightly abnormal. Furthermore, the techniques of Patent Documents 3 and 4 have a problem that it is difficult to quickly determine a cylinder in which the air-fuel ratio is abnormal because various parameters need to be measured for a predetermined time. .

  The present invention has been made in view of the above points, and when the air-fuel ratio abnormality of the internal combustion engine is determined based on the calculated value of the air-fuel ratio F / B control, and when it is determined that there is an air-fuel ratio abnormality, It is an object of the present invention to provide a control device and a control method that can shorten the fuel injection time by a predetermined time period so that only a cylinder that has an air-fuel ratio abnormality can be misfired.

  In order to achieve the above object, a control device of the present invention is a control device that controls an internal combustion engine, and stores upstream of a storage unit that stores control information of the internal combustion engine and a purification catalyst that purifies exhaust gas of the internal combustion engine. The detection result of the upstream air-fuel ratio detection unit that detects the air-fuel ratio of the exhaust gas before passing through the purification catalyst and the detection result of the exhaust gas after passing through the purification catalyst provided on the downstream side of the purification catalyst An air-fuel ratio abnormality determination process for determining whether an abnormality has occurred in the air-fuel ratio of at least one cylinder of the internal combustion engine based on the detection result of the downstream-side air-fuel ratio detection unit that detects the air-fuel ratio; An air-fuel ratio abnormality cylinder specifying process for specifying a cylinder in which an abnormality occurs in the air-fuel ratio, and an air-fuel ratio abnormality determination when it is determined by the determination process that an abnormality occurs in the air-fuel ratio of at least one cylinder of the internal combustion engine; Processing judgment result and It executes a storage process for storing the identification result of the air-fuel ratio abnormal cylinder specifying process in the storage unit, the comprises an execution unit, a (claim 1).

  In particular, in the control device of the present invention, the execution unit misfires during execution of the fuel injection time shortening process for shortening the injection time of the fuel to be injected into each cylinder of the internal combustion engine by a predetermined time and the fuel injection time shortening process. Further, a misfire cylinder detection process for detecting a cylinder is executed, and the cylinder in which the air-fuel ratio abnormality cylinder identification process has detected misfire in the misfire cylinder detection process is identified as a cylinder in which an abnormality occurs in the air-fuel ratio ( Claim 2).

  In the control device of the present invention, the fuel injection time shortening process determines the injection time of fuel to be injected into each cylinder of the internal combustion engine until at least the misfire cylinder detection process detects misfire of any cylinder. Then, each fuel injection cycle of each cylinder is shortened by a predetermined time.

  In the control device according to the present invention, the misfire cylinder detection processing includes a rotation angle sensor that detects the degree of change in the angular velocity of the internal combustion engine, an exhaust temperature sensor that detects the exhaust gas temperature of the internal combustion engine, and each cylinder of the internal combustion engine. On the basis of at least one detection signal of a vibration sensor for detecting the vibration of the engine and a knocking sensor for detecting knocking of each cylinder of the internal combustion engine, a misfire of the cylinder of the internal combustion engine is determined (claim 4).

  Further, the control device according to the present invention provides that when the air-fuel ratio abnormal cylinder specifying process is performed, when the engine speed is equal to or lower than a predetermined speed and the torque is equal to or lower than a predetermined value, an abnormality occurs in the air-fuel ratio. The specified cylinder is identified (Claim 5).

  Further, the control method of the present invention is provided on the upstream side of the purification catalyst that purifies the exhaust gas of the internal combustion engine, and the detection result of the upstream air-fuel ratio detection unit that detects the air-fuel ratio of the exhaust gas before passing through the purification catalyst. And an air-fuel ratio of at least one cylinder of the internal combustion engine based on a detection result of a downstream air-fuel ratio detection unit that is provided downstream of the purification catalyst and detects the air-fuel ratio of the exhaust gas after passing through the purification catalyst An air-fuel ratio abnormality determining step for determining whether an abnormality has occurred in the air-fuel ratio, and an air-fuel ratio abnormality determination step and an air-fuel ratio abnormality determining step, An air-fuel ratio abnormal cylinder specifying step for specifying a cylinder in which an abnormality has occurred, a determination step for the air-fuel ratio abnormality determining step, and a storage step for storing in the storage unit the determination result for the air-fuel ratio abnormal cylinder specifying step are executed. To (claim 6).

  The control method of the present invention includes a fuel injection time shortening step for shortening the injection time of fuel to be injected into each cylinder of the internal combustion engine by a predetermined time, and a misfire for detecting a misfired cylinder during execution of the fuel injection time shortening step. A cylinder detecting step, wherein the cylinder in which the misfire is detected in the misfiring cylinder detecting step is identified as a cylinder in which the air-fuel ratio is anomalous.

  According to the control device and the control method of the present invention, the air-fuel ratio abnormality of the internal combustion engine is determined based on the calculated value of the air-fuel ratio F / B control, and when it is determined that there is an air-fuel ratio abnormality, the fuel to each cylinder is determined. Since the injection time can be shortened by a predetermined time and only the cylinder in which the air-fuel ratio is abnormal can be misfired, the cylinder in which the air-fuel ratio abnormality has occurred in the multi-cylinder engine can be quickly identified. Therefore, the fuel injection amount to the cylinder in which the air-fuel ratio abnormality has occurred can be corrected and quickly corrected to the target air-fuel ratio.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings.

  Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a configuration diagram showing a schematic configuration of an engine 1 incorporating a control device for an internal combustion engine of the present invention. FIG. 1 shows only the configuration of one cylinder of the engine.

  The engine 1 is a multi-cylinder engine mounted on a vehicle, and each cylinder includes a piston that constitutes a combustion chamber 15. The piston of each combustion chamber 15 is connected to the shaft of the crankshaft which is an output shaft through a connecting rod, and the reciprocating motion of each piston is converted into the rotation of the crankshaft by the connecting rod.

  A crank angle sensor 30 is disposed in the vicinity of the crankshaft axis. The crank angle sensor 30 is configured to detect the rotation angle of the crankshaft shaft, and outputs the detection result to the engine ECU 100. Thereby, the engine ECU 100 can acquire information on the crank angle, such as the engine speed during operation. Further, the engine ECU 100 inputs an angular velocity signal detected by the crank angle sensor 30, and obtains a degree of change in angular velocity by differentiating the change in angular velocity. Then, it is determined whether or not the cylinder has misfired based on the degree of change in angular velocity for each cylinder. Thus, engine ECU 100 can identify the misfired cylinder based on the output signal from crank angle sensor 30.

  An intake port 14 that communicates with the combustion chamber 15 and an intake passage 13 that is connected to the intake port 14 and guides intake air to the intake port 14 and the combustion chamber 15 are connected to the combustion chamber 15 of each cylinder. . Further, an exhaust port 16 communicating with the combustion chamber 15 and an exhaust passage 17 for guiding the exhaust gas generated in the combustion chamber 15 to the outside of the engine 1 are connected to each cylinder of the combustion chamber 15. Further, the exhaust passages 17 connected to the cylinders merge on the downstream side to form a single merged exhaust passage 18.

  A plurality of intake valves and exhaust valves are provided corresponding to the intake passage and exhaust passage of the combustion chamber 15 of each cylinder. FIG. 1 shows one intake passage, one exhaust passage, one intake valve, and one exhaust valve. An intake valve and an intake camshaft are arranged in each intake port 14 of the combustion chamber 15. Further, an exhaust valve and an exhaust camshaft are disposed in each exhaust port 16 of the combustion chamber 15. The intake valve and the exhaust valve are opened and closed by the rotation of the intake camshaft and the exhaust camshaft to which the rotation of the crankshaft is transmitted by a coupling mechanism (for example, a timing belt, a timing chain, etc.). Communicate and block The phases of the intake valve and the exhaust valve are expressed with reference to the crank angle.

  An air flow meter 3 that detects the amount of intake air passing through the intake passage 13 is installed in the intake passage 13 of the engine 1. A throttle position sensor 4 and a throttle valve 5 are installed in the intake passage 13. The air flow meter 3 and the throttle position sensor 4 output respective detection results to the engine ECU 100. Accordingly, the engine ECU 100 recognizes the intake air amount sucked into the intake port 14 and the combustion chamber 15 and adjusts the opening degree of the throttle valve 5 to thereby adjust the intake air amount necessary for the operation of the engine 1 to the combustion chamber 15. Can be imported.

  An injector 6 is attached to the intake port 14 of the engine 1. High-pressure fuel supplied through a fuel pipe from a fuel pump (not shown) is injected and supplied into the intake port 14 by the injector 6 according to an instruction from the engine ECU 100. The injector 6 may be provided in each cylinder of the engine 1 so that fuel is directly injected into the combustion chamber 15 of the engine 1. The engine ECU 100 determines the fuel injection amount and the injection timing based on the intake air amount from the air flow meter 3 and the throttle position sensor 4 and the cam shaft rotation phase information from the cam angle sensor 31, and sends a signal to the injector 6. The injector 6 injects fuel into the intake port 14 at a high pressure according to a signal from the engine ECU 100 at the instructed fuel injection amount / injection timing. The high-pressure injected fuel is atomized and mixed with intake air to become a mixed gas suitable for combustion of the engine 1, and is supplied to the combustion chamber 15 by opening the intake valve. The leaked fuel from the injector 6 is returned to the fuel tank (not shown) through the relief pipe.

  Each cylinder combustion chamber 15 is provided with a spark plug 7. The mixed gas flowing in from the intake port 14 is compressed in the combustion chamber 15 by the upward movement of the piston. The engine ECU 100 determines the ignition timing based on the position of the piston from the crank angle sensor 30 and the cam shaft rotation phase information from the cam angle sensor 31 and ignites the spark plug 7 to ignite the compressed mixed gas. Thus, the inside of the combustion chamber 15 is expanded to lower the piston. The engine 1 obtains power by changing this to shaft rotation of the crankshaft via the connecting rod. When the exhaust valve is opened, the exhaust gas after combustion merges in the merged exhaust passage 18 through the exhaust port 16 and the exhaust passage 17, passes through the purification catalyst 20, and is discharged to the outside of the engine 1.

  The exhaust passages 17 of the cylinders merge downstream to form a merged exhaust passage 18, and a purification catalyst 20 is provided at the end of the merged exhaust passage 18. The purification catalyst 20 is used to purify the exhaust gas of the engine 1. For example, a three-way catalyst or a NOx occlusion reduction type catalyst is applied, and these purification catalysts 20 are different depending on the displacement of the engine 1, the use area, and the like. May be installed in combination. The purification catalyst 20 is provided with a catalyst temperature sensor 51. By receiving a signal from the catalyst temperature sensor 51, the engine ECU 100 can recognize the temperature of the purification catalyst 20 and determine whether the purification catalyst 20 is in the active temperature range.

  One exhaust temperature sensor 41 is provided in the exhaust passage 17 of each cylinder. The exhaust temperature sensor 41 detects the temperature of the exhaust gas discharged from each cylinder, and transmits the result to the engine ECU 100. Thereby, engine ECU 100 can acquire exhaust gas temperature information of each cylinder in various load states. Further, the engine ECU 100 determines from the detection result of the exhaust temperature sensor 41 that the cylinder in which the temperature of the exhaust gas has extremely decreased has misfired. As a result, the engine ECU 100 can identify the misfired cylinder based on the output signal from the exhaust temperature sensor 41. One exhaust temperature sensor 41 may be provided in the merged exhaust passage 18.

  An A / F sensor 42 is provided in the merged exhaust passage 18 upstream of the purification catalyst 20. The A / F sensor 42 detects the air-fuel ratio in the engine from the oxygen concentration and the unburned gas concentration in the exhaust gas, and transmits the result to the engine ECU 100. Thus, the engine ECU 100 can acquire engine air-fuel ratio information in various load states. As the A / F sensor 42, a zirconia surface coated with platinum and a diffusion-controlling layer provided on the outer periphery of the outer electrode is often used. When a voltage is applied to the element, the lean side (A / F> 14.7) Thus, an oxygen ion current corresponding to the unburned gas concentration is generated on the rich side (A / F <14.7) with respect to the oxygen concentration in the exhaust gas. In this case, since the output current of the A / F sensor 42 has a positive correlation with the air-fuel ratio, this makes it possible to detect the air-fuel ratio in a wide range. Further, the engine ECU 100 calculates a correction value of the fuel injection amount to the cylinder from the detection result of the A / F sensor 42, and executes main air-fuel ratio F / B control for correcting the air-fuel ratio to a target value.

  An O2 sensor 43 is provided in the merged exhaust passage 18 on the downstream side of the purification catalyst 20. The O2 sensor 43 detects the oxygen concentration remaining in the exhaust gas and transmits the result to the engine ECU 100. Thus, the engine ECU 100 can acquire engine air-fuel ratio information in various load states. As the O2 sensor 43, a structure similar to that of the A / F sensor 42 and having a zirconia surface coated with platinum is often used, and 0.5 [V near the theoretical air-fuel ratio (A / F = 14.7). ], 1 [V] on the rich side (A / F <14.7) and 0 [V] on the lean side (A / F> 14.7). Further, the engine ECU 100 executes the sub air-fuel ratio F / B control for correcting the calculation result by the main air-fuel ratio F / B control based on the detection result of the O2 sensor 43, thereby further improving the accuracy of the air-fuel ratio control. be able to. Further, the engine ECU 100 imbalances the air-fuel ratio between the cylinders when the average value of the sub air-fuel ratio F / B control calculated based on the detection result of the O2 sensor 43 greatly exceeds the normal value (within 2%). Is determined to have occurred. And the process which shortens the fuel injection time to each cylinder by predetermined time is performed, and the cylinder which misfired earliest is identified as the cylinder which the air-fuel ratio imbalance has arisen.

  A vibration sensor 44 is provided in each cylinder of the engine 1. The vibration sensor 44 is a vibration-type angular velocity sensor, and can be applied with a configuration in which Coriolis force is generated when an angular velocity is applied to the vibrating body, and a vibration component based on the generated Coriolis force is detected. . The vibration sensor 44 detects vibration associated with combustion of the engine 1 and transmits the result to the engine ECU 100. Thereby, engine ECU 100 can acquire information on the combustion state of each cylinder in various load states. Further, the engine ECU 100 determines from the detection result of the vibration sensor 44 that the cylinder whose vibration has changed extremely has misfired. As a result, the engine ECU 100 can identify the misfired cylinder based on the output signal from the vibration sensor 44. Note that one vibration sensor 44 may be provided at a predetermined position of the cylinder block of the engine 1.

  A knock sensor 45 is provided in each cylinder of the engine 1. Knock sensor 45 generates an electromotive force in response to a pressure change in the combustion chamber and a knocking vibration frequency, and transmits the signal to engine ECU 100. Thereby, engine ECU 100 recognizes the occurrence of knocking and cancels knocking by delaying the ignition timing. Further, engine ECU 100 determines from the detection result of knocking sensor 45 that the cylinder in which the pressure or vibration frequency in the combustion chamber has changed extremely has misfired. Thereby, engine ECU 100 can identify the cylinder that misfires based on the output signal from knocking sensor 45.

  The engine ECU 100 reads the detection results of the crank angle sensor 30, the cam angle sensor 31, the air flow meter 3, the throttle position sensor 4, the water temperature sensor, etc., and operates the throttle valve 5, the intake valve, the exhaust valve, and the injector 6. The operation of the engine 1 such as the ignition timing of the spark plug 7 is controlled in an integrated manner.

  Further, engine ECU 100 identifies a misfired cylinder based on the detection results of crank angle sensor 30, exhaust temperature sensor 41, vibration sensor 44, and knocking sensor 45. In addition, since the misfire identification method based on the detection result of each sensor was mentioned above, the detailed description is abbreviate | omitted.

  Then, the engine ECU 100 calculates a correction value of the fuel injection amount to the cylinder from the detection result of the A / F sensor 42, and executes main air-fuel ratio F / B control for correcting the air-fuel ratio to the target value. Further, engine ECU 100 executes sub air-fuel ratio F / B control that corrects the calculation result of main air-fuel ratio F / B control based on the detection result of O2 sensor 43. Further, when the average value of the calculated values of the sub air-fuel ratio F / B control based on the detection result of the O2 sensor 43 greatly exceeds the normal value (within 2%) (for example, around 10%), the engine ECU 100 It is determined that an imbalance has occurred in the air-fuel ratio.

  When the engine ECU 100 determines that an imbalance has occurred in the air-fuel ratio between the cylinders, the fuel injection time of the injector 6 of each cylinder is shortened by a predetermined time until one of the cylinders misfires. Execute the process. In many cases, a cylinder in which an abnormality occurs in the air-fuel ratio and combustion is abnormal has a leaner air-fuel ratio than other cylinders due to, for example, clogging of the injector nozzle holes. For this reason, the cylinder having an air-fuel ratio abnormality is misfired earliest when the fuel injection amount is gradually decreased. Therefore, by executing this process, the cylinder in which the air-fuel ratio abnormality has occurred can be specified. . Therefore, it is possible to quickly and accurately identify the cylinder in which the air-fuel ratio is abnormal while suppressing a decrease in engine output to a minimum. Here, as the predetermined time for shortening the fuel injection time, an arbitrary time during which the cylinder in which the air-fuel ratio abnormality has occurred can be quickly misfired is applied, and can be set to 500 [μsec], for example. In this case, the engine ECU 100 shortens the fuel injection time of all cylinders by 500 [μsec] at a time, and detects the presence or absence of misfire in each cylinder. For example, in the case of a four-cylinder engine, the injection time of fuel injected in the order of cylinder 1, cylinder 3, cylinder 4, and cylinder 2 is all shortened by 500 [μsec], and misfire detection is performed on the cylinder into which fuel is injected. When a misfire is detected in any of the cylinders, the imbalance abnormality flag is turned on for the cylinder in which the misfire is detected. If no misfire is detected in any of the cylinders, the engine ECU 100 again reduces the fuel injection time of all the cylinders by 500 [μsec] at once, and detects the presence or absence of misfire in each cylinder. In this manner, the engine ECU 100 detects the presence or absence of misfire in each cylinder by reducing the fuel injection time to each cylinder by a predetermined time until any cylinder misfires. The engine ECU 100 can specify the abnormal air-fuel ratio cylinder without affecting the running of the vehicle by executing the identification of the abnormal air-fuel ratio cylinder during idle operation or motor operation in a hybrid vehicle. it can.

  FIG. 2 shows a hardware configuration of the microcomputer 70 of the engine ECU 100. The microcomputer 70 includes a CPU (Central Processing Unit) 71, a ROM (Read Only Memory) 72, a RAM (Random Access Memory) 73, an NVRAM (Non Volatile RAM) 74, an input / output unit 75, and the like. The CPU 71 reads a program stored in the ROM 72 and performs a calculation according to this program. That is, the CPU 71 reads the program stored in the ROM 72 to control the operation of the engine 1 in an integrated manner. Further, the RAM 73 is written with the data of the calculation results of the main air-fuel ratio F / B control and the sub air-fuel ratio F / B control, and the NVRAM 74 is the data written in the RAM 73 and the air-fuel ratio imbalance between cylinders. Data necessary to be saved is written when the ignition is turned off, such as an abnormal or air-fuel ratio abnormal cylinder identification result. The input unit 75 inputs signals from various sensors such as the crank angle sensor 30, the exhaust temperature sensor 41, the A / F sensor 42, the O2 sensor 43, the vibration sensor 44, and the knocking sensor 45. Engine ECU 100 corresponds to the execution unit of the present invention. The RAM 73 and NVRAM 74 correspond to the storage unit of the present invention.

  Subsequently, the operation of the engine 1 will be described along the control flow of the engine ECU 100. FIG. 3 is a flowchart showing an example of processing of the engine ECU 100. The engine 1 of the present embodiment determines whether or not an abnormality has occurred in the air-fuel ratio of at least one cylinder of the engine 1 by the air-fuel ratio abnormality determination process. Subsequently, the engine 1 executes control for specifying the cylinder in which the air-fuel ratio is abnormal by the air-fuel ratio abnormal cylinder specifying process.

  In addition, the engine 1 of this embodiment has an abnormality in the air-fuel ratio by shortening the injection time of fuel injected into each cylinder of the engine 1 by a predetermined time until the cylinder in which the air-fuel ratio is abnormal misfires. The control which identifies the cylinder which has produced is performed.

  The engine 1 of this embodiment executes control for determining misfire of the cylinder of the engine 1 based on at least one detection signal of the crank angle sensor 30, the exhaust temperature sensor 41, the vibration sensor 44, and the knocking sensor 45. .

  Further, the engine 1 of the present embodiment executes control for specifying a cylinder in which an abnormality occurs in the air-fuel ratio when the rotation speed and torque of the engine 1 are equal to or less than predetermined values.

  The control of the engine ECU 100 starts when an engine start request is made, that is, when the ignition switch is turned on. First, in step S1, engine ECU 100 determines whether the average value of the calculation results of the sub air-fuel ratio F / B control based on the detection result of O2 sensor 43 is equal to or greater than a predetermined value. Here, the predetermined value is an average value of arbitrary calculation results that can be determined that an air-fuel ratio imbalance abnormality has occurred between the cylinders, and may be 2%, for example. If the average value of the calculation results of the sub air-fuel ratio F / B control is greater than or equal to a predetermined value (step S1 / YES), engine ECU 100 proceeds to step S3. If the average value of the calculation results of the sub air-fuel ratio F / B control is not equal to or greater than the predetermined value (step S1 / NO), the engine ECU 100 proceeds to the next step S2, and the air-fuel ratio of each cylinder of the engine 1 is normal. The control process is terminated.

  If the determination in step S1 is yes, engine ECU 100 proceeds to step S3. In step S3, engine ECU 100 determines that an imbalance abnormality has occurred in the air-fuel ratio between the cylinders. Then, in the next step S4, engine ECU 100 determines whether the rotational speed and torque of engine 1 are equal to or less than predetermined values. Here, as the predetermined values of the rotational speed and the torque, any rotational speed and torque that can be determined that the engine 1 is in the idling operation are applied. Further, when the vehicle is a hybrid vehicle, an arbitrary rotation speed and torque that can be determined to be during motor operation are applied. With this process, the cylinder in which the air-fuel ratio is abnormal can be identified without affecting the running of the vehicle. If the rotation speed and torque of engine 1 are not less than or equal to the predetermined values (step S4 / NO), engine ECU 100 ends the control process. If the rotational speed and torque of engine 1 are not more than the predetermined values (step S4 / YES), engine ECU 100 proceeds to the next step S5.

  In step S5, engine ECU 100 determines whether fuel injection to each cylinder has been stopped. When fuel injection to each cylinder is stopped (step S5 / NO), engine ECU 100 ends the control process. If the fuel injection to each cylinder is not stopped (step S5 / YES), the engine ECU 100 proceeds to the next step S6.

  In step S6, the engine ECU 100 executes a process for reducing the fuel injection time of the injectors 6 of all the cylinders of the engine 1 by a predetermined time. Here, since the predetermined time to be shortened has been described above, a detailed description thereof will be omitted. By executing this process, it is possible to first misfire the cylinder in which the air-fuel ratio becomes abnormal and the combustion abnormality occurs. After finishing step S6, engine ECU 100 proceeds to next step S7.

  In step S7, engine ECU 100 detects a misfire in the cylinder into which the fuel has been injected. By this process, it is possible to quickly and accurately identify the cylinder in which the air-fuel ratio is abnormal while suppressing a decrease in engine output to a minimum. After finishing step S7, engine ECU 100 proceeds to next step S8.

  In step S8, engine ECU 100 determines whether or not there has been a misfired cylinder when all the cylinders have misfired. If there is no misfired cylinder (step S8 / NO), the engine ECU 100 returns to step S6 and repeats the above-described processing until a misfire of any cylinder is detected. If there is a misfired cylinder (step S8 / YES), engine ECU 100 proceeds to the next step S9.

  In step S9, the engine ECU 100 turns on the air-fuel ratio abnormality flag of the cylinder that has detected misfire. By executing this process, it is possible to quickly correct the fuel injection amount of the cylinder in which the air-fuel ratio is abnormal, and thus it is possible to quickly improve the exhaust emission deteriorated due to the air-fuel ratio imbalance. When the process of step S9 is completed, the engine ECU 100 proceeds to the next step S10, stores the result in the NVRAM 74, and ends the control process.

  As described above, the engine of this embodiment determines whether or not an abnormality has occurred in the air-fuel ratio of at least one cylinder of the engine by the air-fuel ratio abnormality determining process and the air-fuel ratio abnormal cylinder specifying process, Cylinders in which an abnormality occurs in the air-fuel ratio by shortening the injection time of the fuel injected into each cylinder by a predetermined time until the cylinder in which the air-fuel ratio is abnormal is misfired when it is determined that the balance state is established Can be specified. Therefore, in the multi-cylinder engine, the cylinder in which the air-fuel ratio abnormality has occurred can be quickly identified, and the fuel injection amount to the cylinder in which the air-fuel ratio abnormality has occurred is corrected and quickly corrected to the target air-fuel ratio. Can do.

  Further, the engine of this embodiment can determine misfire of the cylinder of the engine based on at least one detection result of the crank angle sensor, the exhaust temperature sensor, the vibration sensor, and the knocking sensor. Therefore, since the misfire of the cylinder can be detected with high accuracy, the cylinder in which the air-fuel ratio abnormality has occurred can be identified with high accuracy at an early stage.

  Furthermore, the engine of the present embodiment can execute control for specifying a cylinder in which an abnormality occurs in the air-fuel ratio when the engine speed and torque are equal to or less than predetermined values. Therefore, it is possible to identify a cylinder in which an air-fuel ratio abnormality has occurred without affecting the running of the vehicle.

  The above embodiments are merely examples for carrying out the present invention. Therefore, the present invention is not limited to these, and various modifications and changes can be made within the scope of the gist of the present invention described in the claims.

  For example, the shortening time of the fuel injection time in the specific process of the air-fuel ratio abnormal cylinder can be arbitrarily set according to the driving state of the vehicle. If you want to suppress engine output reduction, set a shorter fuel injection time (for example, 250 [μsec]), or if you want to quickly identify an abnormal air-fuel ratio, increase the fuel injection time. (For example, 750 [μsec]). Further, the fuel injection amount to each cylinder may be gradually decreased by gradually decreasing the injection hole opening amount of the injector 6 without changing the fuel injection time.

  Further, the process of shortening the fuel injection time to each cylinder (decreasing the fuel injection amount) may be performed for each cylinder. For example, first, the fuel injection time is shortened by a predetermined time only for the cylinder 1 in the multi-cylinder, and the fuel injection amount when the cylinder 1 misfires is stored. Subsequently, after returning the fuel injection time to the cylinder 1 to the normal time, the fuel injection amount when the cylinder 3 misfires is shortened by a predetermined time only for the other cylinder, for example, only the cylinder 3. Remember. In this way, the fuel injection amount when the cylinder is misfired by shortening the fuel injection time for each cylinder by a predetermined time is memorized, and the fuel injection amount at the time of misfire of all the cylinders is detected and compared. It is also possible to specify the cylinder in which the occurrence of the.

It is the block diagram which showed schematic structure of the engine of the Example. It is the block diagram which showed the hardware constitutions of the microcomputer of engine ECU. The flow of control which engine ECU of an example performs is shown. It is the block diagram which showed the A / F sensor and O2 sensor which are provided in an internal combustion engine.

Explanation of symbols

1 Engine 6 Injector 7 Spark plug 14 Intake port 15 Combustion chamber 16 Exhaust port 17 Exhaust passage 18 Merged exhaust passage 20 Purification catalyst 30 Crank angle sensor 41 Exhaust temperature sensor 42 A / F sensor 43 O2 sensor 44 Vibration sensor 45 Knock sensor 70 Microcomputer 71 CPU
72 ROM
73 RAM (storage unit)
74 NVRAM (storage unit)
100 engine ECU (execution unit)

Claims (7)

A control device for controlling an internal combustion engine,
A storage unit for storing control information of the internal combustion engine;
Provided upstream of the purification catalyst that purifies the exhaust gas of the internal combustion engine, the detection result of the upstream air-fuel ratio detection unit that detects the air-fuel ratio of the exhaust gas before passing through the purification catalyst, and provided downstream of the purification catalyst Whether or not an abnormality has occurred in the air-fuel ratio of at least one cylinder of the internal combustion engine based on the detection result of the downstream air-fuel ratio detection unit that detects the air-fuel ratio of the exhaust gas after passing through the purification catalyst. An air-fuel ratio abnormality determination process for determining;
An air-fuel ratio abnormality cylinder specifying process for specifying a cylinder having an abnormality in the air-fuel ratio when it is determined by the air-fuel ratio abnormality determination process that an abnormality has occurred in the air-fuel ratio of at least one cylinder of the internal combustion engine;
A storage process for storing the determination result of the air-fuel ratio abnormality determination process and the identification result of the air-fuel ratio abnormality cylinder identification process in the storage unit;
An execution unit for executing
A control device comprising: The execution unit is a fuel injection time shortening process for shortening the injection time of fuel to be injected into each cylinder of the internal combustion engine by a predetermined time;
A misfire cylinder detection process for detecting a misfired cylinder during the fuel injection time reduction process,
2. The control device according to claim 1, wherein the air-fuel ratio abnormal cylinder specifying process specifies a cylinder in which the misfire is detected in the misfire cylinder detecting process as a cylinder in which an abnormality occurs in the air-fuel ratio.   In the fuel injection time shortening process, the fuel injection time to be injected into each cylinder of the internal combustion engine is determined for each fuel injection cycle of each cylinder until at least the misfire cylinder detection process detects a misfire of any cylinder. The control device according to claim 2, wherein the control device is shortened by predetermined time.   The misfire cylinder detection processing includes a rotation angle sensor that detects the degree of change in the angular velocity of the internal combustion engine, an exhaust temperature sensor that detects the exhaust gas temperature of the internal combustion engine, a vibration sensor that detects vibration of each cylinder of the internal combustion engine, 4. The control device according to claim 1, wherein misfire of a cylinder of the internal combustion engine is determined based on at least one detection signal with a knocking sensor that detects knocking of each cylinder of the internal combustion engine. 5.   The air-fuel ratio abnormal cylinder specifying process is executed to specify a cylinder in which an abnormality occurs in the air-fuel ratio when the rotation speed of the internal combustion engine is equal to or lower than a predetermined speed and the torque is equal to or lower than a predetermined value. The control device according to any one of 1 to 4. Provided upstream of the purification catalyst that purifies the exhaust gas of the internal combustion engine, the detection result of the upstream air-fuel ratio detection unit that detects the air-fuel ratio of the exhaust gas before passing through the purification catalyst, and provided downstream of the purification catalyst Whether or not an abnormality has occurred in the air-fuel ratio of at least one cylinder of the internal combustion engine based on the detection result of the downstream air-fuel ratio detection unit that detects the air-fuel ratio of the exhaust gas after passing through the purification catalyst. An air-fuel ratio abnormality determination step to determine;
An air-fuel ratio abnormality cylinder specifying step for specifying a cylinder in which an abnormality occurs in the air-fuel ratio when it is determined in the air-fuel ratio abnormality determination step that an abnormality occurs in the air-fuel ratio of at least one cylinder of the internal combustion engine;
A storage step of storing the determination result of the air-fuel ratio abnormality determination step and the specification result of the air-fuel ratio abnormality cylinder specifying step in the storage unit;
Control method to execute. A fuel injection time shortening step for shortening an injection time of fuel to be injected into each cylinder of the internal combustion engine by a predetermined time;
A misfire cylinder detection step for detecting a misfire cylinder during execution of the fuel injection time reduction step,
The control method according to claim 6, wherein in the air-fuel ratio abnormal cylinder specifying step, the cylinder in which the misfire is detected in the misfire cylinder detecting step is specified as a cylinder in which the air-fuel ratio is abnormal.

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