Controller of internal combustion engine and method for detecting abnormality due to misfire in internal combustion engine

Abstract

To early detect an abnormality due to misfire caused by a stuck fuel injection valve.SOLUTION: A misfire determination unit 110 determines the presence / absence of misfire in a cylinder. A counter unit 120 increments a counter value C1 when the presence / absence of misfire has determined, and increments a counter value C2 when it is determined misfire has occurred. When it is determined that misfire has occurred, a misfire rail pressure difference calculation unit 130 acquires a misfire rail pressure difference ΔPF, which is a difference in fuel pressure in a common rail before and after fuel injection, and calculates an average value ΔPFav of the misfire rail pressure difference ΔPF to update the misfire rail pressure difference ΔPF. The abnormality determination unit 140 determines that an abnormality due to misfire has occurred when a value C1 is equal to or larger than a predetermined value A, a value C2 is equal to or larger than a predetermined value B, and the average value ΔPFa is equal to or larger than a threshold value C. When the value C1 is equal to or larger than the predetermined value A, the value C2 is equal to or larger than the predetermined value B, and the average value ΔPFa is less than the threshold value C, it determines that an abnormality due to misfire and a stuck injector have occurred.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to a control device for an internal combustion engine and a method for detecting a misfire abnormality in an internal combustion engine. [Background technology]

[0002] Japanese Patent Laid-Open No. 2008-297954 (Patent Document 1) detects a misfire state of an internal combustion engine by using an ignition determination means that determines whether or not ignition has occurred in a cylinder of the internal combustion engine. The ignition determination means determines that ignition has not occurred (misfire has occurred) when the increase in the rotation speed of the internal combustion engine synchronized with an injection command to a fuel injection valve is smaller than a predetermined value.

[0003] In Patent Document 1, whether a misfire is caused by a fuel injection valve malfunction is determined based on the pressure drop characteristics of the common rail pressure during a misfire. Specifically, in a misfire determination routine, the presence or absence of a misfire is detected using fluctuations in the rotation speed of each cylinder, and when a misfire is detected, an abnormality determination counter Nn is incremented. When the value of the abnormality determination counter Nn exceeds a predetermined value Kn, a misfire flag is turned on. Then, when the misfire flag is turned on, a normal injection determination routine is performed to determine whether the fuel injection valve is injecting fuel normally using the drop characteristics of the common rail pressure of the misfiring cylinder. If the fuel injection valve is not injecting fuel normally, an abnormality determination counter Nf is incremented. When the value of the abnormality determination counter Nf exceeds a predetermined value Kf, an abnormal injection flag is turned on. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-297954 Summary of the Invention [Problem to be solved by the invention]

[0005] In Patent Document 1, when a misfire abnormality occurs (when the misfire flag is turned on), if the abnormal injection flag is on, it can be determined that the misfire is caused by a malfunction of the fuel injector. However, since the normal injection determination routine is executed after the abnormality determination counter Nn exceeds the predetermined value Kn and the misfire flag is turned on, it may take some time to determine that the misfire is caused by a malfunction of the fuel injector.

[0006] An object of the present disclosure is to enable early detection of misfire abnormalities caused by sticking of a fuel injection valve. [Means for solving the problem]

[0007] (1) A control device for an internal combustion engine disclosed herein is a control device for an internal combustion engine equipped with a common rail fuel injection device that injects fuel stored in a common rail into cylinders through fuel injection valves. The control device includes a misfire determination unit that determines misfire in a cylinder of the internal combustion engine, a misfire rail pressure difference calculation unit that acquires a misfire rail pressure difference, which is the difference in fuel pressure in the common rail before and after fuel injection when a misfire is determined, and updates the misfire rail pressure difference, and an abnormality determination unit. The abnormality determination unit determines that a misfire abnormality has occurred when the number of misfires, which is the number of times a misfire has been determined, is equal to or greater than a predetermined value and the misfire rail pressure difference is equal to or greater than a threshold value. The abnormality determination unit determines that a misfire abnormality has occurred due to a stuck fuel injection valve when the number of misfires is equal to or greater than the predetermined value and the misfire rail pressure difference is less than the threshold value.

[0008] According to this configuration, the internal combustion engine is equipped with a common rail fuel injection device. The control device for the internal combustion engine includes a misfire determination unit, a misfire rail pressure difference calculation unit, and an abnormality determination unit. The misfire rail pressure difference calculation unit obtains a misfire rail pressure difference, which is the difference in fuel pressure in the common rail before and after fuel injection, during fuel injection when a misfire is determined to have occurred, and updates the misfire rail pressure difference. The abnormality determination unit determines that a misfire abnormality has occurred if the misfire rail pressure difference is equal to or greater than a threshold value when the number of misfires, which is the number of times a misfire has been determined to have occurred, is equal to or greater than a threshold value, and determines that a misfire abnormality is caused by a stuck fuel injection valve if the misfire rail pressure difference is less than the threshold value.

[0009] The misfire rail pressure difference calculation unit acquires and updates the misfire rail pressure difference each time the misfire determination unit determines a misfire.The abnormality determination unit determines whether the misfire is caused by a stuck fuel injector based on the misfire rail pressure difference when the number of misfires reaches or exceeds a predetermined value.Since it is possible to determine whether the misfire is caused by a stuck fuel injector at the same time as the number of misfires reaches or exceeds the predetermined value and a misfire is detected, misfires caused by a stuck fuel injector can be detected early.

[0010] (2) The misfire rail pressure difference calculation unit may update the misfire rail pressure difference by averaging the misfire rail pressure difference.

[0011] According to this configuration, the average value of the misfire-causing rail pressure difference is compared with the threshold value, so it is possible to determine with comparatively high accuracy whether the misfire abnormality is caused by a stuck fuel injection valve.

[0012] (3) In (1) and (2) above, when the number of misfires in a predetermined period of time exceeds a predetermined value, the abnormality determination unit may determine that a misfire abnormality has occurred if the rail pressure difference at the time of misfire is equal to or greater than the threshold value, or may determine that a misfire abnormality has occurred if the rail pressure difference at the time of misfire is less than the threshold value, and may determine that a misfire abnormality has occurred if the number of misfires in a predetermined period of time is less than the predetermined value.

[0013] According to this configuration, the presence or absence of a misfire abnormality is determined based on the number of misfires within a predetermined period, so it is possible to quickly determine whether a misfire abnormality exists and whether the misfire abnormality is caused by a stuck fuel injection valve.

[0014] (4) In the above (1) to (3), the fuel injection is a multi-stage injection, and the rail pressure difference during misfire may be the difference between the fuel pressure before the start of the multi-stage injection and the fuel pressure after the end of the main injection in the multi-stage injection.

[0015] According to this configuration, even if the fuel injection is a multi-stage injection, it is possible to accurately determine whether or not the misfire abnormality is caused by a stuck fuel injection valve.

[0016] (5) In the above (1) to (4), the misfire determination unit may determine misfire based on fluctuations in the rotation speed of the internal combustion engine.

[0017] According to this configuration, misfire can be determined using the crank angle sensor that detects the rotation speed of the internal combustion engine.

[0018] (6) A misfire detection method for an internal combustion engine according to the present disclosure is a method for detecting a misfire in an internal combustion engine equipped with a common rail fuel injection device that injects fuel pressurized in a common rail into cylinders from fuel injection valves. The misfire detection method includes determining a misfire in a cylinder of the internal combustion engine, acquiring a misfire rail pressure difference, which is the difference in fuel pressure in the common rail before and after fuel injection when a misfire is determined, calculating an average value of the misfire rail pressure difference, counting the number of misfires, which is the number of times a misfire has been determined, and, when the number of misfires is equal to or greater than a predetermined value, determining that a misfire has occurred if the average misfire rail pressure difference is equal to or greater than a threshold value, and determining that a misfire has occurred due to a stuck fuel injection valve if the misfire rail pressure difference is less than the threshold value.

[0019] According to this method, the rail pressure difference at misfire is obtained each time a misfire is determined, and the average value of the rail pressure difference at misfire is calculated. Then, when the number of misfires reaches or exceeds a predetermined value, it is determined whether the misfire is caused by a stuck fuel injector based on the average value of the rail pressure difference at misfire. Because it is possible to determine whether the misfire is caused by a stuck fuel injector at the same time as the number of misfires reaches or exceeds the predetermined value and a misfire is detected, misfires caused by a stuck fuel injector can be detected early.

[0020] (7) In (6) above, the number of misfires may be the number of misfires in a predetermined period.

[0021] According to this method, the presence or absence of a misfire abnormality is determined based on the number of misfires within a predetermined period, allowing for early determination of the presence or absence of a misfire abnormality. Note that the abnormality detection method may further include determining that a misfire abnormality does not exist when the number of misfires is less than a predetermined value. [Effects of the Invention]

[0022] According to the present disclosure, misfire abnormalities caused by sticking of a fuel injection valve can be detected at an early stage. [Brief explanation of the drawings]

[0023] [Figure 1] 1 is a schematic configuration diagram of a control device for an internal combustion engine according to an embodiment of the present invention; [Figure 2] 4 is a flowchart of a misfire abnormality diagnosis process executed in the engine ECU. [Figure 3] FIG. 2 is a functional block diagram for misfire abnormality diagnosis processing configured in the engine ECU. [Figure 4] FIG. 3 is a diagram showing a change in rail pressure (fuel pressure in the common rail) when fuel is injected from an injector. DETAILED DESCRIPTION OF THE INVENTION

[0024] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are designated by the same reference numerals, and description thereof will not be repeated.

[0025] FIG. 1 is a schematic diagram of a control device for an internal combustion engine according to this embodiment. Engine 1 is a multi-cylinder compression ignition internal combustion engine (diesel engine) equipped with a control device (engine ECU (Electronic Control Unit)) 100. In this embodiment, engine 1 is used as a drive source for a vehicle and is mounted on the vehicle. Engine 1 is an internal combustion engine that performs compression autoignition by injecting fuel from fuel injection valves (injectors) 14 into combustion chambers formed in cylinders 12 of an engine body 10. In this embodiment, engine 1 is a four-cylinder compression ignition internal combustion engine and is equipped with four cylinders 12, numbered first (#1) to fourth (#4). An injector 14 is provided for each cylinder 12. Engine 1 is a four-stroke (four-cycle) diesel engine.

[0026] An air cleaner 22, an intercooler 24, and a throttle valve (diesel throttle valve) 26 are provided in the intake passage 20 of the engine 1. Fresh air, from which foreign matter has been removed by the air cleaner 22, is supercharged (compressed) by a compressor 32 of a turbocharger 30, cooled by the intercooler 24, supplied to an intake manifold 28, and then supplied to each combustion chamber through an intake port.

[0027] Exhaust gases discharged from the combustion chambers are collected in an exhaust manifold 50 and released into the outside air via an exhaust passage 52. A portion of the exhaust gases is returned to the intake manifold 28 via an EGR (Exhaust Gas Recirculation) passage 60. An EGR cooler 62 and an EGR valve 64 are provided in the EGR passage 60.

[0028] The exhaust passage 52 is provided with, from the upstream side, the turbine 34 of the turbocharger 30, a small oxidation catalyst (ATC: After Turbo Catalyst) 70, an oxidation catalyst (DOC: Diesel Oxidation Catalyst) 71, and a DPF (Diesel Particulate Filter) 72. The DPF 72 is a filter that collects particulate matter (PM) in the exhaust gas and purifies the exhaust by appropriately burning and removing the collected PM. Although not shown, a urea addition valve and a selective reduction catalyst may be provided downstream of the DPF 72. Note that a NOx storage-reduction catalyst (NSR (NOx Storage-Reduction) catalyst) may be provided instead of or in addition to the urea addition valve and the selective reduction catalyst.

[0029] The fuel injection system of engine 1 is a common rail type fuel injection system. Fuel is stored in a fuel tank 40. The fuel in fuel tank 40 is supplied to a high-pressure fuel pump 42 by a feed pump 41. High-pressure fuel discharged from high-pressure fuel pump 42 is pumped through a fuel passage 43 to a common rail 44. The high-pressure fuel stored in common rail 44 is injected into the combustion chamber (into the cylinder) from injector 14. Injector 14 is driven by a drive circuit 200, which opens and closes a fuel injection hole (not shown).

[0030] The engine ECU 100, which is a control device, includes a CPU 101, a memory 102 consisting of ROM and RAM, an input / output port (not shown) for inputting and outputting various signals, and executes predetermined calculations based on information stored in the memory 102 and information from various sensors, thereby controlling the injector 14 (drive circuit 200), the throttle valve 26, the high-pressure fuel pump 42, the variable nozzle 34, etc.

[0031] The various sensors that input signals to the engine ECU 100 include, for example, a crank angle sensor 111, a cam angle sensor 112, an accelerator pedal sensor 113, an air flow meter 114, a fuel pressure sensor 115, a water temperature sensor 116, and the like.

[0032] The crank angle sensor 111 is a sensor for determining the crank angle CA, and detects the reference position and rotation angle of the crankshaft of the engine 1. The cam angle sensor 112 is a sensor for cylinder discrimination, and detects the rotation angle (cam position) SA of the camshaft of the engine 1. The accelerator pedal sensor 113 detects the amount of accelerator pedal operation by the user (hereinafter also referred to as "accelerator opening") AP. The air flow meter 114 detects the amount of intake air Ga of the engine 1.

[0033] The fuel pressure sensor 115 detects the fuel pressure Pf in the common rail 44. The water temperature sensor 116 detects the engine 1 cooling water temperature THW.

[0034] In the engine 1 configured as described above, the engine ECU 100 executes fuel injection control, misfire abnormality diagnosis processing, and the like. For example, in fuel injection control, the engine ECU 100 calculates a total fuel injection amount Qa from a fuel injection amount map based on the accelerator opening AP and the engine rotation speed NE. The engine rotation speed NE is calculated based on the rotation angle detected by the crank angle sensor 111. The engine ECU 100 calculates a pilot injection amount Qi, a pre-injection amount Qr, and an after-injection amount Qt based on the engine rotation speed NE and the total fuel injection amount Qa. The engine ECU 100 then calculates a main injection amount Qm by subtracting the pilot injection amount Qi, the pre-injection amount Qr, and the after-injection amount Qt from the total fuel injection amount Qa.

[0035] The engine ECU 100 calculates the main injection timing Itm from an injection timing map based on the engine rotation speed NE and the total fuel injection amount Qa (or the accelerator pedal position AP). Then, based on the engine rotation speed NE and the total fuel injection amount Qa, the engine ECU 100 sets the pilot injection timing Iti, the pre-injection timing Itr, and the after-injection timing Itt with the main injection timing Itm as a reference. The engine ECU 100 calculates the crank angle CA of the engine 1 based on the cam position SA (cylinder discrimination signal) detected by the cam angle sensor 112 and the rotation angle detected by the crank angle sensor 111. When the crank angle CA reaches each injection timing It*, the engine ECU 100 controls (opens) the injector 14 using the drive circuit 200 to inject fuel in the pilot injection amount Qi, the pre-injection amount Qr, the main injection amount Qm, and the after-injection amount Qt. The engine ECU 100 also controls the high-pressure fuel pump 42 so that the fuel pressure Pf in the common rail 44 becomes the target rail pressure Pt.

[0036] The engine ECU 100 executes a misfire abnormality diagnosis process. FIG. 2 is a flowchart of the misfire abnormality diagnosis process executed by the engine ECU 100. This flowchart is initiated when an ignition switch (not shown) is turned on, the engine 1 is started, and the coolant temperature THW reaches a predetermined temperature or higher, completing the warm-up of the engine 1. An initialization process is executed simultaneously with the ignition switch being turned on, resetting a counter C1, a counter C2, and an average value ΔPFav of the misfire-time rail pressure difference ΔPF, which will be described later, to 0. This flowchart is executed for each cylinder (#1 to #4), and an interrupt process is executed for each cylinder every cycle (720° CA). In this embodiment, the ignition order of the engine 1 is #1 → #3 → #4 → #2, so the engine ECU 100 executes the process in the order #1 → #3 → #4 → #2 every 180° CA.

[0037] In step (hereinafter, step will be abbreviated as "S") 10, the counter C1 is incremented, and then the process proceeds to S12, where it is determined whether or not a misfire has occurred.

[0038] Misfire is determined based on fluctuations in the engine speed NE of the cylinder in question. In this embodiment, if the difference ΔNE (=NEb-NEa) between the engine speed NEb at the time of fuel injection (ignition) of the cylinder that received fuel injection immediately before the cylinder in question and the engine speed NEa at the time of fuel injection (ignition) of the cylinder in question is greater than a set value, it is determined that misfire has occurred in the cylinder in question. Note that, as described in Patent Document 1, misfire may also be determined by comparing a fluctuation value, which is the range between the minimum and maximum values ​​of rotational speed fluctuation of the cylinder in question, with a predetermined value.

[0039] If misfire is determined in S12, the process proceeds to S14, where counter C2 is incremented, and then the process proceeds to S16. If misfire is not determined in S12, the process proceeds to S20.

[0040] In S16, a misfire-time rail pressure difference ΔPF is calculated. The misfire-time rail pressure difference ΔPF is the absolute value of the difference between the post-fuel injection fuel pressure Pfa and the pre-fuel injection fuel pressure Pfb in the cylinder in question (ΔPF=|Pfa-Pfb|). In this embodiment, the fuel pressure Pfb is the fuel pressure Pf detected by fuel pressure sensor 115 at a predetermined crank angle advance side from the pilot injection timing Iti. The fuel pressure Pfa is the fuel pressure Pf detected by fuel pressure sensor 115 at a predetermined crank angle retard side from the end of the after-injection. When after-injection is not performed (when the after-injection amount Qt is 0), the fuel pressure Pf may be the fuel pressure Pf detected by fuel pressure sensor 115 at a predetermined crank angle retard side from the end of the main injection.

[0041] In S18, the average value ΔPFav of the misfire-time rail pressure difference ΔPF is calculated, and then the process proceeds to S20. For example, the average value ΔPFav is calculated as ΔPFav=((previous ΔPFav*(C2-1)+ΔPF)) / C2), where C2 is the current value of counter C2.

[0042] In S20, it is determined whether the value C1 of the counter C1 is equal to or greater than a predetermined value A. If C1 is less than the predetermined value A, a negative determination is made and the current routine is terminated. If C1 is equal to or greater than the predetermined value A, the routine proceeds to S22. The predetermined value A may be, for example, "250." The period until the value C1 of the counter C1 reaches the predetermined value A corresponds to an example of the "predetermined period" of the present disclosure.

[0043] In S22, it is determined whether the value C2 of counter C2 is equal to or greater than a predetermined value B. If C2 is less than the predetermined value B, the program proceeds to S24, where it is determined that there is no misfire abnormality, and the current routine is terminated. If C2 is equal to or greater than the predetermined value B, a positive determination is made in S22, and the program proceeds to S26. The predetermined value B is a value smaller than the predetermined value A, and may be, for example, "200." The value C2 of counter C2 corresponds to an example of the "number of misfires" in this disclosure.

[0044] In S26, it is determined whether the average value ΔPFav of the misfire-time rail pressure difference ΔPF is equal to or greater than a threshold value C. If the average value ΔPFav is less than the threshold value C, the program proceeds to S28, where it is determined that the cylinder in question has a misfire abnormality and that the injector 14 for that cylinder is stuck (stuck closed), and the current routine is terminated. This determines that a misfire abnormality caused by the stuck injector 14 has occurred.

[0045] In S26, if the average value ΔPFav is equal to or greater than the threshold value C, an affirmative determination is made and the routine proceeds to S30. In S30, it is determined that a misfire abnormality has occurred in the cylinder, and the current routine ends. Note that in S30, a determination as to whether the injector 14 is stuck is not made.

[0046] Once S24, S28, and S30 have been processed, the misfire abnormality diagnosis process for that cylinder will not be executed until the next time the ignition switch is turned ON. When S28 and S30 have been processed, engine ECU 100 turns on MIL (Malfunction Indicator Lamp) 300 provided on the vehicle's instrument panel and writes a fault diagnosis code indicating a misfire abnormality into the nonvolatile memory included in memory 102. Furthermore, when S28 has been processed, engine ECU 100 writes a fault diagnosis code indicating that the injector 14 is stuck (stuck closed) into the nonvolatile memory included in memory 102. The fault diagnosis code may include information (cylinder number information) about the cylinder in which the misfire abnormality has occurred and the cylinder in which the injector 14 is stuck.

[0047] 3 is a functional block diagram for misfire abnormality diagnosis processing configured in engine ECU 100. This functional block is configured by the hardware and software (program) of engine ECU 100 working together.

[0048] The misfire determination unit 110 calculates the difference ΔNE between the engine speed NEb at the time of fuel injection into the cylinder that received fuel injection immediately before the cylinder in question and the engine speed NEa at the time of fuel injection (ignition) into the cylinder in question, based on the crank angle CA and the engine speed NE. If ΔNE is greater than a set value, it is determined that a misfire has occurred in the cylinder in question. The misfire determination unit 110 corresponds to the process of S12 (FIG. 2).

[0049] The counting unit 120 increments the value C1 of the counter C1 each time the misfire determination unit 110 performs processing, and increments the value C2 of the counter C2 each time the misfire determination unit 110 determines that a misfire has occurred. The counting unit 120 corresponds to the processing of S10 and S14.

[0050] The misfire rail pressure difference calculation unit 130 corresponds to the processing of S16 and S18, and an acquisition unit 130a calculates the misfire rail pressure difference ΔPF using the crank angle CA and the fuel pressure Pf every time a misfire is determined by the misfire determination unit 110. Furthermore, an update unit 130b calculates the average value ΔPFav of the misfire rail pressure difference ΔPF.

[0051] The abnormality determination unit 140 corresponds to the processing of S22 to S30, and determines whether there is "no misfire abnormality," "misfire abnormality and injector stuck," or "misfire abnormality (no injector stuck)" based on the value C1 of the counter C1, the value C2 of the counter C2, and the average value ΔPFav.

[0052] FIG. 4 is a diagram showing changes in fuel pressure Pf (rail pressure: fuel pressure in the common rail 44) when fuel is injected from the injector 14. In FIG. 4, the vertical axis represents fuel pressure Pf, and the horizontal axis represents crank angle CA. When fuel is normally injected from the injector 14, the fuel pressure Pf decreases with fuel injection, as indicated by the black circles and solid line in FIG. 4. Therefore, the fuel pressure Pfa after fuel injection is smaller than the fuel pressure Pfb before fuel injection, and the misfire rail pressure difference ΔPF (=|Pfa−Pfb|) calculated by misfire rail pressure difference calculation unit 130 (calculated in S16) increases.

[0053] If the injector 14 is stuck (stuck closed), fuel injection is not performed even if a command to open the injector 14 is issued at the fuel injection timing, and therefore the fuel pressure Pf does not decrease, as indicated by the squares and dashed line in Figure 4. Therefore, when the injector 14 is stuck, the misfire-time rail pressure difference ΔPF calculated by the misfire-time rail pressure difference calculation unit 130 (calculated in S16) is approximately zero.

[0054] In this embodiment, when misfire determination section 110 determines that a misfire has occurred (positive determination in S12), misfire-time rail pressure difference calculation section 130 acquires the misfire-time rail pressure difference ΔPF (S16), calculates the average value ΔPFav of the misfire-time rail pressure difference ΔPF, and updates the misfire-time rail pressure difference ΔPF. Then, when the number of misfires (value C2 of counter C2) is equal to or greater than predetermined value B (positive determination in S22), and the average value ΔPFav is equal to or greater than threshold value C (positive determination in S26), it is determined that a misfire abnormality has occurred. On the other hand, when the average value ΔPFav is less than threshold value C (negative determination in S26), it is determined that a misfire abnormality has occurred and that the injector 14 is stuck, and it is thus determined that a misfire abnormality has occurred due to the injector 14 being stuck (stuck closed).

[0055] In this embodiment, the average value ΔFPav is updated each time a misfire is determined. When the number of misfires (value C2 of counter C2) reaches or exceeds a predetermined value B, the average value ΔFPav is used to determine whether the misfire is due to a stuck injector 14. When the number of misfires reaches or exceeds the predetermined value B and a misfire is detected, it is simultaneously possible to determine whether the misfire is due to a stuck injector 14, allowing for early detection of a misfire due to a stuck injector 14.

[0056] In this embodiment, the number of times a misfire has been determined (the number of processes) is counted by a counter C1. When the number of processes for determining whether or not a misfire has occurred reaches or exceeds a predetermined value A (when a positive determination is made in S20), it is determined whether or not the number of misfires has reached or exceeds a predetermined value B (S22) to determine whether or not a misfire abnormality has occurred. Therefore, since the presence or absence of a misfire abnormality is determined based on the number of misfires during a predetermined period (the period until the value C1 of the counter C1 reaches the predetermined value A), it is possible to quickly determine whether or not a misfire abnormality has occurred and whether or not the misfire abnormality is caused by a stuck injector 14.

[0057] In this embodiment, when S28 (FIG. 2) is processed, a diagnostic fault code indicating a misfire abnormality and a diagnostic fault code indicating that the injector 14 is stuck (stuck closed) are written to the non-volatile memory included in the memory 102. Therefore, by checking these diagnostic fault codes with a diagnostic fault tool (diagnostic scan tool), the fault in the injector 14 can be identified and repaired promptly.

[0058] In the above embodiment, misfire is determined based on fluctuations in engine speed NE. However, the determination (detection) of misfire is not limited to this. For example, misfire may be detected based on the detection signal of an ignition sensor provided in each cylinder. Also, misfire may be determined based on the signal of an in-cylinder pressure sensor provided in each cylinder.

[0059] In the above embodiment, the misfire-induced rail pressure difference ΔPF is updated by calculating the average value ΔPFav of the misfire-induced rail pressure difference ΔPF (S18). However, in S18, the misfire-induced rail pressure difference ΔPF may be updated by calculating the median value of the misfire-induced rail pressure difference ΔPF. Alternatively, the misfire-induced rail pressure difference ΔPF may be updated by excluding the minimum and maximum values ​​of the misfire-induced rail pressure difference ΔPF from the calculated average value ΔPFav.

[0060] In the above embodiment, the misfire abnormality diagnosis process flowchart in Fig. 2 is executed when the warm-up of the engine 1 is completed. However, the misfire abnormality diagnosis process may be executed when the warm-up of the engine 1 is completed and the total fuel injection amount Qa is equal to or greater than a predetermined value. This increases the misfire rail pressure difference ΔPF when fuel injection is performed normally, making it possible to more appropriately determine whether the injector 14 is stuck (stuck closed).

[0061] Note that post-injection may be performed when PM accumulates in the DPF 72 and regeneration control of the DPF 72 is performed. The post-injection is performed during the expansion stroke of the engine 1 and does not contribute to the output of the engine 1. If a misfire is determined to have occurred while post-injection is being performed (a positive determination is made in S12 of FIG. 2), the fuel pressure Pf detected by the fuel pressure sensor 115 at a crank angle that is a predetermined crank angle retarded from the time when the after-injection ended and before the post-injection started may be used as the fuel pressure Pfa. Furthermore, if after-injection is not being performed (when the after-injection amount Qt is 0), the fuel pressure Pf detected by the fuel pressure sensor 115 at a crank angle that is a predetermined crank angle retarded from the time when the main injection ended and before the post-injection started may be used as the fuel pressure Pfa.

[0062] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims, not by the description of the above embodiments, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0063] 1 engine, 10 engine body, 12 cylinder, 14 fuel injection valve (injector), 20 intake passage, 22 air cleaner, 24 intercooler, 26 throttle valve (diesel throttle valve), 28 intake manifold, 30 turbocharger, 32 compressor, 34 turbine, 40 fuel tank, 41 feed pump, 42 high-pressure fuel pump, 43 fuel passage, 44 common rail, 50 exhaust manifold, 52 exhaust passage, 60 EGR passage, 62 EGR cooler, 64 EGR valve, 70 ATC, 71 DOC, 72 DPF, 100 engine ECU, 101 CPU, 102 memory, 110 misfire detection unit, 111 crank angle sensor, 112 cam angle sensor, 113 accelerator pedal sensor, 114 air flow meter, 115 fuel pressure sensor, 116 Water temperature sensor, 120 counting unit, 130 rail pressure difference calculation unit at misfire, 140 abnormality determination unit, 200 drive circuit, 300 MIL.

Claims

1. A control device for an internal combustion engine equipped with a common rail fuel injection device that injects fuel pressurized in a common rail into cylinders from fuel injection valves, a misfire determination unit that determines a misfire in the cylinder of the internal combustion engine; a misfire-time rail pressure difference calculation unit that acquires a misfire-time rail pressure difference, which is a difference in fuel pressure in the common rail before and after fuel injection when it is determined that a misfire has occurred, and updates the misfire-time rail pressure difference; an abnormality determination unit, The abnormality determination unit When the number of misfires, which is the number of times that the misfire is determined to have occurred, is equal to or greater than a predetermined value, When the misfire-time rail pressure difference is equal to or greater than a threshold value, it is determined that a misfire abnormality has occurred, A control device for an internal combustion engine that determines that a misfire abnormality is caused by sticking of the fuel injection valve when the misfire-time rail pressure difference is less than the threshold value.

2. 2. The control device for an internal combustion engine according to claim 1, wherein the misfire-time rail pressure difference calculation unit updates the misfire-time rail pressure difference by averaging the misfire-time rail pressure difference.

3. The abnormality determination unit When the number of misfires in a predetermined period of time is equal to or greater than the predetermined value, When the misfire-time rail pressure difference is equal to or greater than the threshold value, it is determined that a misfire abnormality has occurred, When the misfire-time rail pressure difference is less than the threshold value, it is determined that the misfire abnormality is caused by sticking of the fuel injection valve, and When the number of misfires in the predetermined period is less than the predetermined value, 3. The control device for an internal combustion engine according to claim 1, wherein it is determined that the misfire abnormality does not exist.

4. the fuel injection is a multi-stage injection, 3. The control device for an internal combustion engine according to claim 1, wherein the rail pressure difference during misfire is a difference between a fuel pressure before the start of the multi-stage injection and a fuel pressure after the end of a main injection in the multi-stage injection.

5. 3. The control device for an internal combustion engine according to claim 1, wherein the misfire determination unit determines the misfire based on fluctuations in the rotation speed of the internal combustion engine.

6. A misfire abnormality detection method for an internal combustion engine equipped with a common rail fuel injection device that injects fuel pressurized in a common rail into a cylinder from a fuel injection valve, comprising: determining a misfire in the cylinder of the internal combustion engine; In the fuel injection when it is determined that a misfire has occurred, a rail pressure difference at the time of misfire is acquired, which is a difference in fuel pressure in the common rail before and after the fuel injection; Calculating an average value of the misfire-time rail pressure difference; Counting the number of misfires, which is the number of times that the misfire has been determined; When the number of misfires reaches or exceeds a predetermined value, determining that a misfire abnormality has occurred if the average value of the rail pressure difference at the time of misfire is equal to or greater than a threshold value, and determining that a misfire abnormality has occurred due to sticking of the fuel injection valve if the rail pressure difference at the time of misfire is less than the threshold value.

7. 7. The method for detecting a misfire abnormality in an internal combustion engine according to claim 6, wherein the number of misfires is the number of misfires in a predetermined period.

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