Internal combustion engine fault diagnosis device

Abstract

An internal combustion engine malfunction diagnostic device performs a stop process that stops fuel supply to at least one of a plurality of cylinders and supplies fuel to the remaining cylinders. It also performs a catalytic converter malfunction diagnostic process that diagnoses an exhaust gas purification system malfunction based on a first misfire count, representing the number of misfires detected during a predetermined period of operation of the internal combustion engine. In the catalytic converter malfunction diagnostic process, if the stop process is performed during a predetermined period of operation of the internal combustion engine, the malfunction diagnostic device diagnoses an exhaust gas purification system malfunction when the first misfire count is lower than when the stop process is not performed.

Description

Technical Field

[0001] This invention relates to a diagnostic device for internal combustion engines. Background Technology

[0002] Japanese Patent Application Publication No. 2021-60027 discloses a hybrid vehicle that includes an engine with multiple cylinders and an electric generator. The hybrid vehicle is equipped with an exhaust purification device for purifying exhaust gases emitted from the multiple cylinders. The catalyst in the exhaust purification device exerts its exhaust purification capability at an activation temperature. Therefore, in the hybrid vehicle disclosed in Japanese Patent Application Publication No. 2021-60027, catalyst preheating is performed to raise the catalyst to its activation temperature when the catalyst temperature is low.

[0003] The control device disclosed in Japanese Patent Application Publication No. 2021-60027, when catalyst preheating is required, performs a stop process that stops the fuel supply to a portion of the cylinders in an engine and supplies fuel to the remaining cylinders. As a result, oxygen is supplied to the exhaust gas purification device through the cylinders whose fuel supply has been stopped. Furthermore, the oxidation reaction in the catalyst is promoted, and the catalyst temperature rises. In this way, the control device can promote catalyst preheating by performing the stop process.

[0004] The internal combustion engine's fault diagnosis device detects misfires in each cylinder based on information about changes in engine speed. Furthermore, the device determines whether the frequency of misfires exceeds a threshold whenever the crankshaft rotates a predetermined number of times. If the frequency of misfires exceeds the threshold, the device diagnoses a combustion abnormality.

[0005] Japanese Patent Application Publication No. 2000-73850 discloses an abnormality diagnostic device that, when performing the aforementioned stop process, stops misfire detection for cylinders where fuel supply has stopped, and only performs misfire detection for the remaining cylinders. Summary of the Invention

[0006] When a misfire occurs, the air-fuel mixture after the cylinder is introduced into the exhaust gas purification system. This causes an oxidation reaction, resulting in an excessive temperature rise in the exhaust gas purification system. Therefore, the anomaly diagnostic device, as a diagnostic tool for anomalies in the exhaust gas purification system, diagnoses accumulated damage in the system based on the frequency of misfires. In addition to diagnosing the aforementioned combustion anomalies, the anomaly diagnostic device also performs anomaly diagnosis of the exhaust gas purification system.

[0007] Furthermore, when the shutdown process is performed as described above, the temperature of the exhaust gas purification device rises further due to the introduction of air through the shutdown cylinder. To accurately diagnose any malfunctions in the exhaust gas purification device, the effects of this shutdown process must also be reflected in the diagnostic process.

[0008] The technical solutions used to solve the above problems and their effects are described below.

[0009] An abnormality diagnostic device for an internal combustion engine, designed to address the aforementioned issues, is applicable to internal combustion engines having multiple cylinders. Sometimes, in order to supply oxygen to an exhaust gas purification device, a stop process is performed to stop the fuel supply to at least one of the multiple cylinders and supply fuel to the remaining cylinders (there are cases where this stop process is performed to supply oxygen to the exhaust gas purification device). The abnormality diagnostic device performs: a misfire detection process, detecting the occurrence of misfires in each cylinder based on information about changes in the internal combustion engine speed; a counting process, calculating a misfire count representing the number of misfires detected by the misfire detection process; and a catalyst abnormality diagnostic process, making a diagnosis that an abnormality has occurred in the exhaust gas purification device based on the misfire count representing the number of misfires detected during a predetermined period of engine operation. The catalyst malfunction diagnosis process, when the stop process is performed during the predetermined period of operation of the internal combustion engine, makes a diagnosis that an malfunction has occurred in the exhaust purification device when the misfire count is low, compared to when the stop process is not performed during the predetermined period of operation of the internal combustion engine.

[0010] When a shutdown procedure is performed, the temperature of the exhaust gas purification unit rises due to oxidation caused by the introduction of air through the shut-off cylinder. Therefore, compared to a situation where a shutdown procedure is not performed, even if fewer misfires occur, damage caused by overheating accumulates in the exhaust gas purification unit.

[0011] The aforementioned anomaly diagnostic device, when a stop procedure has been performed, diagnoses an anomaly in the exhaust gas purification system with a lower misfire count compared to when no stop procedure has been performed. In other words, the aforementioned anomaly diagnostic device can detect catalyst anomalies by reflecting overheating damage caused by the stop procedure.

[0012] One aspect of an internal combustion engine anomaly diagnostic device involves, when the stop process is performed during a predetermined period of engine operation, implementing a correction to exclude the number of times fuel supply was stopped due to the stop process from the misfire count, which represents the number of misfires detected during the predetermined period of engine operation. Furthermore, an anomaly determination threshold is calculated such that the more times fuel supply is stopped due to the stop process during the predetermined period of operation, the lower the anomaly determination threshold. Moreover, in the catalyst anomaly diagnostic process, if the corrected misfire count is higher than the anomaly determination threshold, this anomaly diagnostic device diagnoses an anomaly in the exhaust gas purification system.

[0013] The aforementioned anomaly diagnosis device diagnoses an anomaly in the exhaust gas purification system when the misfire count, representing the number of misfires during the combustion cycle accompanied by fuel supply, is greater than an anomaly determination threshold. In a given set of operations, the more times fuel supply is stopped through a shutdown process, the more damage accumulates in the exhaust gas purification system. Therefore, the aforementioned anomaly diagnosis device calculates the anomaly determination threshold such that the more times fuel supply is stopped, the lower the anomaly determination threshold becomes. Thus, the aforementioned anomaly diagnosis device can perform catalyst anomaly diagnosis processing that reflects the accumulation of damage corresponding to the number of times combustion supply is stopped.

[0014] Furthermore, as a scheme to calculate the anomaly determination threshold in the manner of "the more times the fuel supply is stopped by the stop treatment during a predetermined amount of operation, the smaller the anomaly determination threshold will be", the following scheme can be adopted: The anomaly determination threshold is a value obtained by multiplying the average permissible misfire rate by the number of combustion strokes during the predetermined amount of operation in which fuel is supplied. The average permissible misfire rate is obtained by averaging the permissible misfire rate calculated based on the internal combustion engine load rate and the internal combustion engine speed each time the internal combustion engine reaches the compression top dead center during the predetermined period of operation. When the stop treatment is performed, the permissible misfire rate calculated based on the internal combustion engine load rate and the internal combustion engine speed is reduced compared to the case where the stop treatment is not performed.

[0015] One embodiment of an internal combustion engine anomaly diagnostic device, in addition to the catalyst anomaly diagnostic processing, also performs misfire anomaly diagnostic processing. This misfire anomaly diagnostic processing diagnoses a misfire anomaly if the misfire count (i.e., the second misfire count, representing the number of misfires detected during a second predetermined period of engine operation) is greater than a misfire determination threshold. Furthermore, in the misfire anomaly diagnostic processing, if the stop processing is performed during the second predetermined period of engine operation, this anomaly diagnostic device performs a correction to exclude the number of times fuel supply was stopped due to the stop processing from the second misfire count. It also performs a correction to multiply the misfire determination threshold by the proportion of the number of times fuel supply was performed during the second predetermined period of operation to the sum of the number of times the compression top dead center of all cylinders arrived. If the corrected second misfire count is greater than the corrected misfire determination threshold, the misfire anomaly is diagnosed.

[0016] The aforementioned anomaly diagnosis device performs misfire anomaly diagnosis in addition to catalyst anomaly diagnosis. When a stop operation is performed, there is a possibility of erroneous misfire detection occurring in cylinders where fuel supply has stopped. As a result, it may be misdiagnosed as a misfire anomaly due to a high frequency of misfires. In contrast, the aforementioned anomaly diagnosis device, when a stop operation is performed, performs a correction in the misfire anomaly diagnosis process by excluding the number of times fuel supply was stopped from the second misfire count obtained through counting, and further corrects the misfire determination threshold to match the proportion of actual fuel supply. Therefore, the aforementioned anomaly diagnosis device can accurately diagnose misfire anomalies reflecting the presence of cylinders where fuel supply has stopped.

[0017] In one embodiment of an abnormality diagnosis device for an internal combustion engine, when the abnormality determination threshold for the case where the stop process is not performed is set as a first abnormality determination threshold, and the abnormality determination threshold for the case where the stop process is performed is set as a second abnormality determination threshold, and when the misfire determination threshold for the case where the stop process is not performed is set as the first misfire determination threshold, and the misfire determination threshold for the case where the stop process is performed is set as the second misfire determination threshold, the quotient obtained by dividing the second abnormality determination threshold by the first abnormality determination threshold is smaller than the quotient obtained by dividing the second misfire determination threshold by the first misfire determination threshold.

[0018] In misfire diagnosis and handling, the misfire anomaly can be diagnosed by eliminating cylinders that have stopped fuel supply from the list of misfire detection targets. On the other hand, in catalyst anomaly diagnosis and handling, it is not only necessary to eliminate cylinders that have stopped fuel supply from the list of misfire detection targets, but also to reflect the cumulative damage to the exhaust purification device caused by the heat generated from supplying oxygen to cylinders that have stopped fuel supply.

[0019] The statement "The quotient obtained by dividing the second anomaly determination threshold by the first anomaly determination threshold is smaller than the quotient obtained by dividing the second fire determination threshold by the first fire determination threshold" means that "when a stop process is executed, the anomaly determination threshold decreases more than the fire determination threshold when a stop process is not executed."

[0020] That is, in the above-mentioned anomaly diagnosis device, when a stop process is performed, the degree to which the anomaly determination threshold decreases is greater than the degree to which the misfire determination threshold decreases. Therefore, it is possible to not only exclude cylinders that have stopped fuel supply from the misfire detection targets, but also to reflect the accumulation of catalyst anomaly diagnosis that reflects the damage to the exhaust purification device caused by the heat generated from supplying oxygen to cylinders that have stopped fuel supply. Attached Figure Description

[0021] Hereinafter, with reference to the accompanying drawings, the features, advantages, and technical and industrial significance of exemplary embodiments of the present invention will be described, in which the same reference numerals denote the same elements, and wherein:

[0022] Figure 1 This is a schematic diagram showing the configuration of a hybrid vehicle equipped with an engine control unit as one embodiment of an abnormality diagnostic device.

[0023] Figure 2 This is a schematic diagram illustrating the crankshaft angle signal.

[0024] Figure 3 This is a flowchart illustrating the process flow in the routines involved in the regeneration process.

[0025] Figure 4 This is a flowchart illustrating the process flow in the routines involved in fire detection and handling.

[0026] Figure 5 This is a flowchart illustrating the process flow in the routines involved in fire anomaly diagnosis and handling.

[0027] Figure 6 This is a flowchart illustrating the process of handling routines involved in catalyst anomaly diagnosis and treatment.

[0028] Figure 7This is an explanatory diagram of the permissible fire rate mapping data referenced when no stop procedure is performed.

[0029] Figure 8 This is an explanatory diagram of the permissible fire rate mapping data referenced when a stop procedure is executed.

[0030] Figure 9 This is a flowchart illustrating the process of handling catalyst anomaly diagnosis. Detailed Implementation

[0031] The following is for reference Figures 1-9 An engine control unit 300, which is an embodiment of an abnormality diagnosis device for an internal combustion engine, will be described.

[0032] <Regarding the composition of vehicle 10>

[0033] like Figure 1 As shown, vehicle 10 is equipped with engine 50. Figure 1 As shown, engine 50 is a 6-cylinder engine with six cylinders, #1 to #6. Furthermore, engine 50 is equipped with a port injection valve for injecting fuel into the intake port and an in-cylinder injection valve for injecting fuel into the combustion chamber. Additionally, the air-fuel mixture in the combustion chamber is supplied for combustion via a spark plug. The combustion energy generated is converted into rotational energy of the crankshaft 59, which serves as the output shaft of engine 50. The air-fuel mixture supplied for combustion in the combustion chamber is discharged into the exhaust passage. The exhaust passage is equipped with a three-way catalytic converter with oxygen-absorbing capabilities and a gasoline particulate filter (hereinafter referred to as GPF). The GPF is a device that carries the three-way catalytic converter in a filter for capturing particulate matter (PM).

[0034] In addition, the vehicle 10 is equipped with a battery 30 for storing electricity. Furthermore, the vehicle 10 is equipped with a first electric generator 11 and a second electric generator 12. The aforementioned first electric generator 11 and second electric generator 12 are motors that generate driving force in response to the power supplied from the battery 30, and also function as generators that receive power from external sources and generate electricity to charge the battery 30.

[0035] Furthermore, the vehicle 10 is equipped with a planetary gear mechanism 13 having three rotating elements: a sun gear 14, a planet carrier 15, and a ring gear 16. A crankshaft 59 is connected to the planet carrier 15 of the planetary gear mechanism 13. A first input shaft 25, which is connected to the rotating shaft of the first electric generator 11, is connected to the sun gear 14 of the planetary gear mechanism 13. Additionally, a secondary drive gear 17 is integrally provided on the ring gear 16 of the planetary gear mechanism 13. A secondary driven gear 18 meshes with the secondary drive gear 17. A reduction gear 19 meshes with the secondary driven gear 18. A second input shaft 26, which is connected to the rotating shaft of the second electric generator 12, is connected to the reduction gear 19.

[0036] Furthermore, the driven gear 18 is connected to the final drive gear 20 in a manner that allows it to rotate as a single unit. The driven gear 21 meshes with the final drive gear 20. Moreover, the drive shaft 24 of the drive wheel 23 is connected to the driven gear 21 via the differential mechanism 22.

[0037] <About System Control Unit 100>

[0038] The system control unit 100 includes a storage device storing programs and processing circuitry that executes the programs stored in the storage device to perform various controls. The system control unit 100 is connected to the power control unit 200 and the engine control unit 300.

[0039] <About Power Control Unit 200>

[0040] The first electric generator 11 and the second electric generator 12 are connected to the battery 30 via a power control unit 200. The power control unit 200 includes a control circuit, a converter, and a converter. The power control unit 200 operates based on commands from the system control unit 100. Furthermore, the power control unit 200 adjusts the power supply from the battery 30 to the first electric generator 11 and the second electric generator 12, and the charging amount from the first electric generator 11 and the second electric generator 12 to the battery 30. In addition, the vehicle 10 is provided with a connector 31 that can be connected to an external power source 40. Therefore, the battery 30 can also be charged using power supplied from the external power source 40. That is, the vehicle 10 is a plug-in hybrid electric vehicle.

[0041] <About Engine Control Unit 300>

[0042] The engine control unit 300 controls the engine 50 based on instructions from the system control unit 100. The engine control unit 300 includes a storage device storing programs and processing circuitry that executes the programs stored in the storage device to perform various controls.

[0043] The engine control unit 300 receives detection signals from various sensors that detect the operating status of the engine 50. Among the sensors that receive detection signals from the engine control unit 300 is the crankshaft position sensor 134, which detects the rotation angle of the crankshaft 59.

[0044] like Figure 2 As shown, a crankshaft rotor 58 is mounted on a crankshaft 59. The crankshaft rotor 58 has 34 teeth 56 spaced at equal intervals, but includes a gap 57 where the spacing between adjacent teeth 56 is widened. A crankshaft position sensor 134 is positioned facing the periphery of the crankshaft rotor 58, opposite the teeth 56.

[0045] The crankshaft position sensor 134 is a magnetoresistive element type sensor composed of a sensor circuit that incorporates a magnet and a magnetoresistive element (magnetoresistive effect element). When the crankshaft rotor 58 rotates along with the crankshaft 59, the teeth 56 of the crankshaft rotor 58 approach and then separate from the crankshaft position sensor 134. This causes a change in the direction of the magnetic field applied to the magnetoresistive element within the crankshaft position sensor 134, resulting in a change in the internal resistance of the magnetoresistive element. The sensor circuit compares the waveform obtained by converting this resistance change into a voltage with a threshold value and shapes the waveform into a rectangular wave based on Lo and Hi signals, which is then output as the crankshaft angle signal Scr.

[0046] like Figure 2 Specifically, the crankshaft position sensor 134 outputs a Lo signal when it is aligned with tooth 56. Furthermore, the crankshaft position sensor 134 outputs a Hi signal when it is aligned with the gap between teeth 56. Therefore, when a Hi signal corresponding to the missing tooth portion 57 is detected, a Lo signal corresponding to tooth 56 is subsequently detected. And thereafter, a Lo signal corresponding to tooth 56 is detected every 10°CA. After detecting 34 Lo signals in this manner, a Hi signal corresponding to the missing tooth portion 57 is detected again. Therefore, the crankshaft angle from the detection of the Lo signal corresponding to the next tooth 56 after the Hi signal corresponding to the missing tooth portion 57 is 30°CA.

[0047] Furthermore, the interval from the detection of the Lo signal corresponding to tooth 56 after the Hi signal corresponding to tooth 57 until the next detection of the Lo signal after the Hi signal corresponding to tooth 57 is 360°CA as the crankshaft angle.

[0048] The engine control unit 300 calculates the crankshaft angle based on the crankshaft angle signal Scr. In addition, the engine control unit 300 calculates T30, which is the time required for a certain amount of crankshaft angle change, as an index value for the amount of rotational variation of the crankshaft 59. Figure 2 The middle diagram shows the period corresponding to T30. T30 is the time required for the crankshaft angle to change by 30°CA.

[0049] The engine control unit 300 calculates the internal combustion engine speed NE, which is the rotational speed of the crankshaft 59, based on the crankshaft angle signal Scr input from the crankshaft position sensor 134.

[0050] Additionally, an airflow meter 135 is connected to the engine control unit 300 to detect the intake air volume Ga and intake air temperature THA of the engine 50. Furthermore, a water temperature sensor 136 is also connected to the engine control unit 300 to detect the water temperature THW, which is the temperature of the coolant used in the engine 50. Additionally, an exhaust pressure sensor 137 is connected to the engine control unit 300 to detect the pressure Pex of the exhaust gas flowing into the GPF.

[0051] like Figure 1 As shown, a main switch 130 is connected to the system control unit 100, allowing the driver of the vehicle 10 to switch between starting and stopping the vehicle 10's systems. Additionally, an accelerator position sensor 131 and a brake sensor 132, which detect the amount of accelerator operation, are connected to the system control unit 100. Furthermore, a vehicle speed sensor 133, which detects the speed of the vehicle 10, is connected to the system control unit 100.

[0052] In addition, the current, voltage, and temperature of the battery 30 are input to the power control unit 200. Based on the aforementioned current, voltage, and temperature, the power control unit 200 calculates the state of charge (SOC) value, which is the ratio of the battery 30's charge margin to its charge capacity.

[0053] The engine control unit 300 and the power control unit 200 are respectively connected to the system control unit 100. Furthermore, the system control unit 100, the power control unit 200, and the engine control unit 300 exchange and share information based on the detection signals input from the sensors and the information calculated therefrom.

[0054] Based on this information, the system control unit 100 outputs commands to the engine control unit 300, thereby controlling the engine 50. Additionally, based on this information, the system control unit 100 outputs commands to the power control unit 200. Thus, the system control unit 100 controls the first electric generator 11 and the second electric generator 12, and controls the charging of the battery 30, through the power control unit 200. In this way, the system control unit 100 controls the vehicle 10 by outputting commands to the power control unit 200 and the engine control unit 300.

[0055] <Control of Vehicle 10>

[0056] Next, the control of the vehicle 10 by such a system control unit 100 will be described in more detail.

[0057] The system control unit 100 calculates the required output value as the output of the vehicle 10 based on the accelerator operation amount and vehicle speed. Then, the system control unit 100 determines the torque distribution of the engine 50, the first electric generator 11, and the second electric generator 12 according to the required output, the state of charge (SOC) index value of the battery 30, etc. Then, it controls the output of the engine 50 and the power operation / regeneration based on the first electric generator 11 and the second electric generator 12. In addition, the system control unit 100 switches the driving mode of the vehicle 10 according to the magnitude of the SOC index value.

[0058] When the State of Charge (SOC) value exceeds a certain level, the system control unit 100 selects a motor driving mode that utilizes the driving force based on the second electric generator 12 and the first electric generator 11 instead of the engine 50. In other words, the system control unit 100 selects the motor driving mode when the battery 30 has sufficient charge reserve.

[0059] On the other hand, when the State of Charge (SOC) value falls below a certain level, the system control unit 100 selects a hybrid driving mode that uses the engine 50 for driving, in addition to the first electric generator 11 and the second electric generator 12.

[0060] Furthermore, even when the State of Charge (SOC) value exceeds a certain level, the system control unit 100 will select hybrid driving mode under the following circumstances.

[0061] • When the vehicle speed exceeds the maximum speed limit of the motor driving mode.

[0062] • When a large output is temporarily required, such as during rapid acceleration with a large amount of accelerator operation.

[0063] • When the engine needs to be started at 50°C.

[0064] When the system control unit 100 starts the engine 50 in hybrid driving mode, it enables the first electric generator 11 to function as a starter motor. Specifically, the system control unit 100 starts the engine 50 by using the first electric generator 11 to rotate the sun gear 14, thereby rotating the crankshaft 59.

[0065] Furthermore, when the hybrid driving mode is selected, the system control unit 100 switches the control during parking based on the state of charge (SOC) value. Specifically, when the SOC value is above a threshold, the system control unit 100 stops the engine 50 and also stops driving the first electric generator 11 and the second electric generator 12. That is, the system control unit 100 stops the engine 50 and suppresses idling when parking. Conversely, when the SOC value of the battery 30 is below a threshold, the system control unit 100 starts the engine 50. Then, the output of the engine 50 drives the first electric generator 11, enabling the first electric generator 11 to function as a generator.

[0066] When the hybrid driving mode is selected, the system control unit 100 switches control based on the State of Charge (SOC) value during driving. During start-up and light-load driving, if the SOC value of the battery 30 is above a threshold, the system control unit 100 uses only the driving force of the second electric generator 12 to start and drive the vehicle 10. In this case, the engine 50 stops, and no power generation is performed based on the first electric generator 11. On the other hand, during start-up and light-load driving, if the SOC value of the battery 30 is below a threshold, the system control unit 100 starts the engine 50 and uses the first electric generator 11 to generate electricity, charging the battery 30. At this time, the vehicle 10 uses a portion of the driving force of the engine 50 and the driving force of the second electric generator 12 to drive. During stable driving, if the SOC value of the battery 30 is above a threshold, the system control unit 100 operates the engine 50 in a high-efficiency state, primarily using the output of the engine 50 to drive the vehicle 10. At this time, the power of engine 50 is split between the drive wheel 23 and the first electric generator 11 via planetary gear mechanism 13. Thus, vehicle 10 drives while generating electricity using the first electric generator 11. Furthermore, system control unit 100 uses the generated electricity to drive second electric generator 12, and the power of second electric generator 12 assists the power of engine 50. On the other hand, during stable driving, when the state of charge (SOC) of battery 30 is less than a threshold, system control unit 100 increases the internal combustion engine speed NE. The electricity generated by the first electric generator 11 is used to drive the second electric generator 12, and the remaining electricity is used to charge battery 30. Furthermore, during acceleration, system control unit 100 increases the internal combustion engine speed NE and uses the electricity generated by the first electric generator 11 to drive the second electric generator 12. Thus, vehicle 10 accelerates using the power of engine 50 and the power of second electric generator 12. And, during deceleration, system control unit 100 stops the operation of engine 50. Furthermore, the system control unit 100 enables the second electric generator 12 to function as a generator, supplying the generated electricity to the battery 30. In the vehicle 10, the resistance generated by this electricity generation is used for braking. This control of electricity generation during deceleration is called regenerative control.

[0067] <About Recycling Process>

[0068] Figure 3 The diagram shows the processing steps in the routine involved in the regeneration process performed by the engine control unit 300. Figure 3The example shown is implemented by repeatedly executing a program stored in the storage device of the engine control unit 300 at predetermined cycles through the processing circuit of the engine control unit 300. Furthermore, the step numbers of each process will be indicated below using numbers prefixed with "S".

[0069] exist Figure 3 In the illustrated routine, the engine control unit 300 first obtains the internal combustion engine speed NE, the internal combustion engine load rate KL, and the coolant temperature THW (S10). The internal combustion engine load rate KL is calculated by the engine control unit 300 based on the intake air volume Ga and the internal combustion engine speed NE. Next, the engine control unit 300 calculates the updated amount ΔDPM of the accumulated amount DPM based on the internal combustion engine speed NE, the internal combustion engine load rate KL, and the coolant temperature THW (S12). Here, the accumulated amount DPM is the amount of PM captured by the GPF. Specifically, the engine control unit 300 calculates the amount of PM in the exhaust gas discharged into the exhaust passage based on the internal combustion engine speed NE, the internal combustion engine load rate KL, and the coolant temperature THW. In addition, the engine control unit 300 calculates the temperature of the GPF based on the internal combustion engine speed NE and the internal combustion engine load rate KL. Then, the engine control unit 300 calculates the updated amount ΔDPM based on the amount of PM in the exhaust gas and the temperature of the GPF.

[0070] Next, the engine control unit 300 sets the sum obtained by adding the update amount ΔDPM to the accumulated amount DPM as the new accumulated amount DPM. This update of the accumulated amount DPM is performed (S14). Next, the engine control unit 300 determines whether the flag F is "1" (S16). If the flag F is "1", it indicates that a regeneration process for burning and removing PM from the GPF is performed. On the other hand, if the flag F is "0", it indicates that no regeneration process is performed. If the engine control unit 300 determines that the flag F is "0" (S16: No), it determines whether the accumulated amount DPM is above the regeneration execution value DPMH (S18). The regeneration execution value DPMH is a threshold used to determine whether a state requiring PM removal is reached based on "the accumulated amount DPM being above the regeneration execution value DPMH".

[0071] If the engine control unit 300 determines that the regeneration execution value DPMH is above (S18: Yes), it determines whether the execution condition for the regeneration process is met (S20). Here, the execution condition can be set as the condition that the logical product of the following conditions (i) to conditions (iii) is true.

[0072] Condition (i): The internal combustion engine torque command value Te*, which is the command value for the torque of engine 50, means that the predetermined value Teth is greater than or equal to the command value Te*.

[0073] Condition (ii): The internal combustion engine speed NE is above the predetermined speed.

[0074] Condition (iii): The condition under which the torque compensation process of S24 can be performed.

[0075] When the engine control unit 300 determines that the logic product is true (S20: Yes), it performs a regeneration process and sets "1" to the flag F (S22). That is, the engine control unit 300 stops fuel injection from the port injection valves and in-cylinder injection valves of cylinders #2 and #5. Furthermore, the engine control unit 300 makes the air-fuel ratio of the air-fuel mixture in the combustion chambers of cylinders #1, #3, #4, and #6 richer than the stoichiometric air-fuel ratio. In other words, the regeneration process stops fuel supply to a portion of the cylinders and supplies fuel to the remaining cylinders. In this engine 50, fuel supply to two cylinders is stopped. This regeneration process is used to burn off PM trapped in the GPF by increasing the temperature of the GPF by discharging oxygen and unburned fuel into the exhaust passage. This stop process is performed to supply oxygen to the three-way catalytic converter and the GPF, which serve as exhaust purification devices. The engine control unit 300 increases the exhaust temperature by discharging oxygen and unburned fuel into the exhaust passage, thereby burning the unburned fuel in a three-way catalytic converter or similar source. This, in turn, raises the temperature of the GPF (Gas Propellant Fluid). Furthermore, by supplying oxygen to the GPF, PM (particulate matter) trapped in the GPF can be burned and removed.

[0076] Furthermore, the cylinders that stop the fuel supply are not limited to cylinders #2 and #5. For example, the cylinders that stop the fuel supply can be switched sequentially to avoid bias in the number of times the fuel supply is stopped.

[0077] The engine control unit 300 performs a process (S24) to compensate for torque variations in the crankshaft 59 of the engine 50 caused by the cessation of combustion control in cylinders #2 and #5. In this process, the engine control unit 300 outputs an instruction to the power control unit 200. Upon receiving this instruction, the power control unit 200 adds a compensation torque to the required torque for driving relative to the second electric generator 12. Then, the power control unit 200 operates the converter based on the required torque with the compensation torque added.

[0078] Furthermore, the conditions under which this torque compensation process can be performed are, for example, "no abnormality occurs in the second electric generator 12" and "the battery 30 has the power required to perform the torque compensation process".

[0079] On the other hand, when the engine control unit 300 determines that the flag F is "1" (S16: Yes), it determines whether the accumulation amount DPM is below the stop threshold DPML (S26). The stop threshold DPML is a threshold used to determine whether the regeneration process can be stopped based on the accumulation amount DPM being below the stop threshold DPML. When the accumulation amount DPM is below the stop threshold DPML (S26: Yes), the engine control unit 300 stops the regeneration process and sets the flag F to "0" (S28).

[0080] Furthermore, if the engine control unit 300 has completed the processing of S24 and S28, and has made a negative determination in the processing of S18 and S20, it will temporarily terminate the process. Figure 3 The example shown.

[0081] <Regarding Fire Detection and Handling>

[0082] Figure 4 The diagram shows the processing steps in the routine involved in the misfire detection process performed by the engine control unit 300. Figure 4 The example shown is implemented by repeatedly executing the program stored in the storage device of the engine control unit 300 at predetermined cycles through the processing circuit of the engine control unit 300.

[0083] exist Figure 4 In the series of processes shown, the engine control unit 300 first obtains T30 (S30), which is the time required for the crankshaft 59 to rotate 30°CA. T30 is calculated by the engine control unit 300 based on the crankshaft angle signal Scr to measure the time required for the crankshaft 59 to rotate 30°CA. Next, the engine control unit 300 sets "m = 0, 1, 2, 3, ...", substitutes T30[m] into T30[m+1], and substitutes the newly obtained T30 in the process of S30 into T30[0], and stores them in the storage device (S32). This process is used to make the variable in parentheses after T30 "the more past, the larger the number". Through this process, the value of the variable in parentheses is larger than T30 before 30°CA.

[0084] Next, the engine control unit 300 determines whether the current rotation angle of the crankshaft 59 is ATDC90°CA based on the compression top dead center of any one of the cylinders #1 to #6 (S34). If the engine control unit 300 determines that it is ATDC90°CA (S34: Yes), it takes any one of the aforementioned cylinders as the object of the misfire determination and calculates the rotational variation ΔT30[0] of the cylinder that is the object of the determination (S38). In detail, the engine control unit 300 subtracts T30[2] from the latest T30[0]. Here, T30[0] is the time required for the cylinder that is the object of the determination to rotate 30°CA from ATDC60°CA. Therefore, if no misfire occurs, T30[0] is smaller than T30[2], so the rotational variation ΔT30[0] is negative. In contrast, if a misfire occurs, the rotational variation ΔT30[0] becomes positive.

[0085] The engine control unit 300 determines whether the rotational variation ΔT30[0] is greater than or equal to the variation threshold Δth (S40). The rotational variation ΔT30[0] is information about the variation of the internal combustion engine speed NE. The processing in S40 is a misfire detection process that determines whether a misfire has occurred in the cylinder being judged based on the information about the variation of the internal combustion engine speed NE. For example, the engine control unit 300 can also variably set the variation threshold Δth according to the internal combustion engine speed NE and the internal combustion engine load rate KL.

[0086] When the engine control unit 300 determines that the rotational variation ΔT30[0] is greater than or equal to the variation threshold Δth (S40: Yes), it determines that a misfire has occurred and increases the misfire count (S44). Furthermore, the misfire count is a value obtained by counting the number of misfires detected through the misfire detection process. That is, the process in S44 is a counting process that counts the number of misfires detected through the misfire detection process. In the process in S44, as the misfire count, the engine control unit 300 increases the first misfire count Cmf1 and the second misfire count Cmf2. The first misfire count Cmf1 is the misfire count referenced in the catalyst anomaly diagnosis process described later. The second misfire count Cmf2 is the misfire count referenced in the misfire anomaly diagnosis process described later.

[0087] Furthermore, if the engine control unit 300 has completed the processing of S44, or made a negative determination in the processing of S34 and S40, it will temporarily terminate the process. Figure 4 The series of processes shown.

[0088] <Regarding the Diagnosis and Handling of Abnormalities>

[0089] The engine control unit 300 performs anomaly diagnosis processing to diagnose abnormalities caused by misfires in the engine 50. As part of the anomaly diagnosis processing, the engine control unit 300 performs misfire anomaly diagnosis processing and catalyst anomaly diagnosis processing. The misfire anomaly diagnosis processing diagnoses misfire anomalies based on the second misfire count Cmf2. Furthermore, here, a misfire anomaly is defined as an anomaly where the frequency of misfires in the engine 50 exceeds the permissible range. The catalyst anomaly diagnosis processing diagnoses catalyst anomalies based on the first misfire count Cmf1. When the temperature of the exhaust gas purification device rises excessively, damage accumulates in the exhaust gas purification device. Here, a catalyst anomaly is defined as a state where damage caused by overheating accumulates in the exhaust gas purification device beyond the permissible range.

[0090] <Regarding the Diagnosis and Handling of Abnormal Fire Incidents>

[0091] Figure 5 The diagram shows the processing steps in the routine involved in the fire anomaly diagnosis and treatment of this embodiment. Figure 5 The processing shown is achieved by repeatedly executing the program stored in the engine control unit 300 at predetermined cycles through the processing circuit of the engine control unit 300.

[0092] exist Figure 5 In the series of processes shown, the engine control unit 300 first determines whether it is at the compression top dead center (TDC) of any one of the cylinders #1 to #6 (S50). If the engine control unit 300 determines that it is at the compression top dead center of any one of the cylinders (S50: Yes), it increments the second monitoring count Ctdc2 (S52).

[0093] After executing the process in S52, the engine control unit 300 determines whether the second monitoring count Ctdc2 is greater than or equal to the second predetermined value Ceth2 (S54). The second predetermined value Ceth2 is a threshold used to determine that the engine 50 has operated a second predetermined amount based on the fact that "the second monitoring count Ctdc2 has become greater than or equal to the second predetermined value Ceth2".

[0094] If the engine control unit 300 makes a positive determination in the processing of S54 (S54: Yes), it determines whether a stop process has been performed (S56). Here, it determines whether a stop process was performed during the second predetermined period of engine 50 operation. That is, regarding the processing of S56, a positive determination is made as long as there is even a part of the most recent second predetermined period of operation during which a stop process was performed.

[0095] If the engine control unit 300 makes a negative determination in the processing of S56 (S56: No), it determines whether the second misfire count Cmf2 is greater than the misfire determination threshold Cmfth2 (S64). Here, the misfire determination threshold Cmfth2 is set based on the lower limit of the number of misfires that have occurred during the period up to the second predetermined value Ceth2 during which the number of executions of combustion control with fuel supply reaches the second predetermined value.

[0096] If the engine control unit 300 determines that the second misfire count Cmf2 is greater than the misfire determination threshold Cmfth2 (S64: Yes), it performs a misfire anomaly determination (S66). The misfire anomaly determination in S66 is a diagnostic process indicating that a misfire anomaly has occurred in the engine 50. Then, the engine control unit 300 executes a notification process (S68). In the notification process of S68, the engine control unit 300 outputs an instruction to the system control unit 100. The system control unit 100, having received the instruction, operates... Figure 1 The warning light 150 indicates that "an abnormal fire has been diagnosed".

[0097] On the other hand, if the engine control unit 300 determines that the second misfire count Cmf2 is below the misfire determination threshold Cmfth2 (S64: No), the process proceeds to S69. Then, the engine control unit 300 resets the second misfire count Cmf2, the second monitoring count Ctdc2 and the second stop count Cfc2 (described later) to "0" (S69).

[0098] Furthermore, the engine control unit 300 temporarily terminates the process after completing steps S68 and S69 and after making a negative determination in steps S50 and S54. Figure 5 The series of processes shown.

[0099] If the engine control unit 300 makes a positive determination in the process of S56 (S56: Yes), it calculates the second stop count Cfc2 (S58). The second stop count Cfc2 is a value representing the number of times the fuel supply has been stopped by the stop process during the most recent second predetermined operating period. As described above, the fuel supply to two of the six cylinders is stopped during the stop process. Therefore, in the process of S58, the second stop count Cfc2 is calculated by dividing the number of times the compression top dead center arrives during the period of performing the stop process by 3. Then, the engine control unit 300 moves to the process of S60.

[0100] In the processing of S60, the engine control unit 300 substitutes the product obtained by multiplying the misfire determination threshold Cmfth2 by "(Ctdc2-Cfc2) / Ctdc2" into the misfire determination threshold Cmfth2 (S60). Then, the engine control unit 300 moves to the processing of S62. In addition, the processing of S60 is a process of correcting the misfire determination threshold Cmfth2 by "multiplying it by the proportion of the number of times fuel was supplied (Ctdc2-Cfc2) in the second predetermined amount of operation to the sum of the number of times the compression top dead center of all cylinders (Ctdc2) is reached".

[0101] In process S62, the engine control unit 300 substitutes the difference obtained by subtracting the second stop count Cfc2 from the second misfire count Cmf2 into the second misfire count Cmf2 (S62). Then, the engine control unit 300 moves to process S64. Furthermore, the process in S62 is a correction process that "excludes from the number of times fuel supply is stopped by the stop process (second stop count Cfc2) from the number of times the counting process (second misfire count Cmf2) is performed during the second predetermined period of engine 50 operation".

[0102] Figure 5 The routine shown is a misfire anomaly diagnosis process that makes a diagnosis that a misfire anomaly has occurred in engine 50 when the second misfire count Cmf2, which is the number of times a misfire is detected during the second predetermined period of engine 50 operation, is greater than the misfire determination threshold Cmfth2.

[0103] For reference Figure 5 As explained, in this embodiment, when a stop process is performed during the second predetermined period of engine 50 operation (S56: Yes), the second misfire count Cmf2 and the misfire determination threshold Cmfth2 are corrected (S60, S62). Furthermore, if the corrected second misfire count Cmf2 is greater than the corrected misfire determination threshold Cmfth2 (S64: Yes), a misfire anomaly is diagnosed in engine 50 (S66).

[0104] That is, when the engine control unit 300, which is an anomaly diagnosis device, performs a stop operation, it corrects the second misfire count Cmf2 during the misfire anomaly diagnosis process by excluding the number of times fuel supply was stopped. Furthermore, the engine control unit 300 corrects the misfire determination threshold Cmfth2 to match the actual proportion of fuel supply.

[0105] <Regarding Catalyst Abnormality Diagnosis and Handling>

[0106] Figure 6The diagram shows the processing steps in the routine involved in the catalyst abnormality diagnosis and treatment of this embodiment. Figure 6 The processing shown is achieved by repeatedly executing the program stored in the engine control unit 300 at predetermined cycles through the processing circuit of the engine control unit 300.

[0107] exist Figure 6 In the series of processes shown, the engine control unit 300 first determines whether it is at the compression top dead center (TDC) of any one of cylinders #1 to #6 (S70). If the engine control unit 300 determines that it is at the compression top dead center of any cylinder (S70: Yes), it increments the first monitoring count Ctdc1 (S72).

[0108] Next, the engine control unit 300 calculates the permissible misfire rate Rmf. The permissible misfire rate Rmf is the upper limit of the range of misfire rates that do not occur in the exhaust gas purification system due to catalyst abnormalities caused by heating. The engine control unit 300 calculates the permissible misfire rate Rmf based on the internal combustion engine speed NE and the internal combustion engine load rate KL.

[0109] The engine control unit 300 stores mapping data in its storage device, with the internal combustion engine load rate KL and internal combustion engine speed NE as input variables and the allowable misfire rate Rmf as the output variable. The engine control unit 300 uses this mapping data to calculate the allowable misfire rate Rmf. Furthermore, the mapping data is a data set consisting of "discrete values ​​of the input variables" and "values ​​of the output variables corresponding to the values ​​of the input variables." Regarding the mapping operation, for example, if the value of an input variable matches any one of the input variables in the mapping data, the value of the corresponding output variable in the mapping data is used as the operation result. Conversely, if the value of an input variable does not match any one of the input variables in the mapping data, the result is obtained by interpolation of the values ​​of the multiple output variables contained in the mapping data.

[0110] Here, refer to Figure 7 and Figure 8 The mapping data is explained below. The engine control unit 300 stores first mapping data referenced when no stop processing is performed and second mapping data referenced when stop processing is performed.

[0111] like Figure 7 As shown, the first mapping data stores the permissible misfire rate Rmf corresponding to the combination of the internal combustion engine load rate KL and the internal combustion engine speed NE. Furthermore, in Figure 7In the example shown, the engine load rate KL and the permissible misfire rate Rmf are expressed as percentages (%). The permissible misfire rate Rmf calculated using this mapping data is the permissible misfire rate when the engine load rate KL and engine speed NE remain unchanged and the engine operates stably at 50 rpm. This mapping data is created by adapting the values ​​of the output variables for each input variable based on the results of prior experiments and simulations in a model library.

[0112] like Figure 8 As shown, similar to the first mapping data, the second mapping data also stores the permissible misfire rate Rmf corresponding to the combination of the internal combustion engine load rate KL and the internal combustion engine speed NE. The second mapping data stores a value smaller than the permissible misfire rate Rmf in the first mapping data as an output variable. Specifically, the second mapping data is obtained by subtracting "33 (%)" from the output variable in the first mapping data, making the output variable smaller than that in the first mapping data. This is because, during the shutdown process, the cylinders where fuel supply has stopped are considered equivalent to misfired cylinders when calculating the permissible misfire rate Rmf. During the shutdown process, air is introduced into the exhaust purification device from the cylinders where fuel supply has stopped. Therefore, similar to the case of misfire, the temperature of the exhaust purification device rises. As described above, in engine 50, fuel supply to two of the six cylinders is stopped during the shutdown process. Therefore, in this embodiment, the two cylinders where fuel supply has stopped are considered equivalent to misfire cylinders, and the output variable is reduced by subtracting "33 (%)" (equivalent to two-sixths) from the output variable in the first mapping data. Furthermore, Figure 8 The values ​​of the shaded areas are all set to "5 (%)". Therefore, in the second mapping data, the lower limit of the output variable is set to "5 (%)". For example, if the allowable misfire rate Rmf were set too low, like "0 (%)", it would lead to excessively frequent diagnoses of catalyst anomalies during catalyst anomaly diagnosis. The reason for setting the lower limit of the output variable to "5 (%)" is to avoid this situation.

[0113] After selecting either the first or second mapping data based on whether a stop process is performed and calculating the permissible misfire rate Rmf, the engine control unit 300 calculates the cumulative permissible misfire rate ΣRmf (S76). Specifically, the engine control unit 300 adds the permissible misfire rate Rmf calculated in the S74 process to the cumulative permissible misfire rate ΣRmf. Then, the engine control unit 300 stores this sum as a new cumulative permissible misfire rate ΣRmf in a storage device. Furthermore, the cumulative permissible misfire rate ΣRmf is a value used to calculate the average permissible misfire rate Rmf_ave in the processes described later in S84 or S87. The cumulative permissible misfire rate ΣRmf is reset to "0" whenever the average permissible misfire rate Rmf_ave is calculated in the processes of S84 or S87.

[0114] After calculating the cumulative permissible misfire rate ΣRmf (S76), the engine control unit 300 then determines whether the first monitoring count Ctdc1 is greater than or equal to the first predetermined value Ceth1 (S78). The first predetermined value Ceth1 is a threshold used to determine that the engine 50 has operated for a first predetermined quantity based on the first monitoring count Ctdc1 being greater than or equal to the first predetermined value Ceth1. Furthermore, the first predetermined value Ceth1 is smaller than the second predetermined value Ceth2. That is, the first predetermined quantity is less than the second predetermined quantity.

[0115] If the engine control unit 300 makes a positive determination in the processing of S78 (S78: Yes), it performs catalyst abnormality diagnosis processing (S80).

[0116] like Figure 9 As shown, after the catalyst malfunction diagnosis process begins, the engine control unit 300 determines whether a stop process has been performed (S81). Here, it is determined whether a stop process was performed during the first predetermined period of engine 50 operation. That is, in the process of S81, if there is even a part of the most recent first predetermined period of operation during which a stop process was performed, an affirmative determination is made.

[0117] If the engine control unit 300 makes a negative determination in process S81 (S91: No), it calculates the average permissible misfire rate Rmf_ave (S87). Specifically, the engine control unit 300 calculates the average permissible misfire rate Rmf_ave by dividing the cumulative permissible misfire rate ΣRmf stored in the storage device by a first predetermined value Ceth1. That is, the average permissible misfire rate Rmf_ave is the quotient obtained by dividing the cumulative permissible misfire rate ΣRmf by the first predetermined value Ceth1. After calculating the average permissible misfire rate Rmf_ave as described above, the engine control unit 300 sets the cumulative permissible misfire rate ΣRmf to "0".

[0118] Next, the engine control unit 300 calculates the anomaly determination threshold Cmfth1 (S88). Specifically, the engine control unit 300 calculates the anomaly determination threshold Cmfth1 by dividing the product obtained by multiplying the first predetermined value Ceth1 by the average permissible misfire rate Rmf_ave by 100. The calculated value is obtained by multiplying the average permissible misfire rate Rmf_ave by the number of combustion strokes in which fuel is supplied during a predetermined amount of operation. That is, this is a process of converting the average permissible misfire rate Rmf_ave into the permissible number of misfires during the first predetermined amount of operation.

[0119] Then, the engine control unit 300 determines whether the first misfire count Cmf1 is greater than the anomaly determination threshold Cmfth1 (S89). If the engine control unit 300 determines that the first misfire count Cmf1 is greater than the anomaly determination threshold Cmfth1 (S89: Yes), it performs a catalyst anomaly determination (S90). The catalyst anomaly determination in S90 is a diagnostic process that indicates that a catalyst anomaly has occurred in the engine 50. Then, the engine control unit 300 executes a notification process (S91). In the notification process in S91, the engine control unit 300 outputs an instruction to the system control unit 100. The system control unit 100, having received the instruction, operates... Figure 1 The warning light 150 shown indicates that a catalyst malfunction has been diagnosed.

[0120] On the other hand, if the engine control unit 300 determines that the first misfire count Cmf1 is below the abnormality determination threshold Cmfth1 (S89: No), the process proceeds to S92. Then, the engine control unit 300 resets the first misfire count Cmf1, the first monitoring count Ctdc1, and the first stop count Cfc1 (described later) to "0" (S92).

[0121] Furthermore, after completing the processing of S91 and S92, the engine control unit 300 terminates the catalyst anomaly diagnosis process. Then, it temporarily ends. Figure 6 The series of processes shown. Additionally, in Figure 6 If a negative decision is made in the processing of S70 and S78 shown, the process will temporarily end. Figure 6 The series of processes shown.

[0122] If the engine control unit 300 makes a positive determination in the process of S81 (S81: Yes), it calculates the first stop count Cfc1 (S82). The first stop count Cfc1 is a value representing the number of times the fuel supply has been stopped by the stop process during the most recent first predetermined operating period. As described above, during the stop process, the fuel supply to 2 out of 6 cylinders is stopped. Therefore, in the process of S82, the first stop count Cfc1 is calculated by dividing the number of times the compression top dead center arrives during the period when the stop process is performed by 3. Then, the engine control unit 300 moves to the process of S83.

[0123] In the processing of S83, the engine control unit 300 substitutes the differential first misfire count Cmf1 obtained by subtracting the first stop count Cfc1 from the first misfire count Cmf1 into the input (S83).

[0124] Next, the engine control unit 300 calculates the average permissible misfire rate Rmf_ave (S84). The process in S84 is the same as that in S87. However, "performing the process in S84" occurs when a stop process is performed during the first predetermined operating period. Therefore, the cumulative permissible misfire rate ΣRmf used in the process in S84 includes the reference... Figure 8 The permissible fire rate Rmf is calculated from the mapped data as explained. Therefore, the average permissible fire rate Rmf_ave calculated by the process of S84 is likely to be smaller than the average permissible fire rate Rmf_ave calculated by the process of S87.

[0125] Next, the engine control unit 300 calculates the anomaly determination threshold Cmfth1 (S85). Specifically, in the processing of S85, the engine control unit 300 calculates the anomaly determination threshold Cmfth1 by multiplying the difference obtained by subtracting the first stop count Cfc1 from the first predetermined value Ceth1 by the average permissible misfire rate Rmf_ave and dividing the product by 100.

[0126] Then, the engine control unit 300 substitutes the product obtained by multiplying the anomaly determination threshold Cmfth1 by "(Ctdc1-Cfc1) / Ctdc1" into the anomaly determination threshold Cmfth1 (S86). Then, the engine control unit 300 moves to the processing of S89. In addition, the processing of S86 is a process of performing a correction on the anomaly determination threshold Cmfth1 by "multiplying it by the proportion of the number of times fuel was supplied (Ctdc1-Cfc1) in the first predetermined amount of operation to the sum of the number of times the compression top dead center of all cylinders (Ctdc1) is reached".

[0127] Then, the engine control unit 300 moves the processing to S89.

[0128] <The function of this implementation method>

[0129] Figure 9 The routine shown is a catalyst anomaly diagnosis process that makes a diagnosis that a catalyst anomaly has occurred in engine 50 when the first misfire count Cmf1, which represents the number of misfires detected during the first predetermined period of engine 50 operation, is greater than the anomaly determination threshold Cmfth1.

[0130] For reference Figure 9As explained above, in this embodiment of the catalyst malfunction diagnosis process, if a stop process is performed during the first predetermined period of engine 50 operation (S81: Yes), the first misfire count Cmf1 and the malfunction determination threshold Cmfth1 are corrected (S83, S86). Then, if the corrected first misfire count Cmf1 is greater than the corrected malfunction determination threshold Cmfth1 (S89: Yes), a catalyst malfunction is diagnosed in engine 50 (S90).

[0131] That is, the engine control unit 300, which is an anomaly diagnosis device, performs a correction to exclude the number of times fuel supply was stopped during catalyst anomaly diagnosis when a stop process is executed. Furthermore, the anomaly determination threshold Cmfth1 is corrected to match the proportion of fuel supply that actually occurred.

[0132] Furthermore, when a stop procedure is performed, the correction is applied by multiplying the number of times fuel is supplied during a given period of operation by the proportion of the total number of times the compression top dead center arrives in all cylinders. This is common in both the S86 and S60 processes of the misfire anomaly diagnosis process. However, in the case of catalyst anomaly diagnosis, when calculating the permissible misfire rate Rmf (S74) used in calculating the anomaly determination threshold Cmfth1 before the correction is performed, a second mapping data with a smaller output variable than the first mapping data is used. Therefore, when a stop procedure is performed, the anomaly determination threshold Cmfth1 before the correction is performed is smaller than when no stop procedure is performed.

[0133] Therefore, when the engine control unit 300 performs a stop process during the first predetermined period of engine 50 operation, it diagnoses a catalyst malfunction when the first misfire count Cmf1 is smaller, compared to the case where no stop process is performed.

[0134] Furthermore, as mentioned above, in catalyst anomaly diagnosis and handling, when a stop procedure is performed, the anomaly detection threshold Cmfth1 before correction is smaller compared to the case where no stop procedure is performed. For the anomaly detection threshold Cmfth1, which is smaller than the case where no stop procedure is performed, a further correction is applied by multiplying it by the proportion of the number of times fuel is supplied during a given amount of operation to the sum of the number of times the compression top dead center arrives in all cylinders. Therefore, when a stop procedure is performed, the anomaly detection threshold Cmfth1 decreases more significantly than the misfire detection threshold Cmfth2 compared to the case where no stop procedure is performed.

[0135] Here, the anomaly determination threshold Cmfth1 for the case where no stop processing is performed is set as the first anomaly determination threshold, and the anomaly determination threshold Cmfth1 for the case where stop processing is performed is set as the second anomaly determination threshold. Furthermore, the fire ignition determination threshold Cmfth2 for the case where no stop processing is performed is set as the first fire ignition determination threshold, and the fire ignition determination threshold Cmfth2 for the case where stop processing is performed is set as the second fire ignition determination threshold. In this case, the quotient obtained by dividing the second anomaly determination threshold by the first anomaly determination threshold is smaller than the quotient obtained by dividing the second fire ignition threshold by the first fire ignition threshold.

[0136] <Effects of this implementation method>

[0137] (1) When the stop procedure is performed, air is introduced into the cylinder by stopping the cylinder, so the temperature of the exhaust gas purification device rises due to oxidation. Therefore, compared with the case where the stop procedure is not performed, even if fewer misfires occur, damage caused by overheating accumulates in the exhaust gas purification device.

[0138] The aforementioned engine control unit 300, when performing a stop-fire procedure, diagnoses an abnormality in the exhaust gas purification system when the first misfire count Cmf1 is lower than when no stop-fire procedure is performed. In other words, the engine control unit 300 can reflect overheating damage caused by the stop-fire procedure and perform catalyst abnormality diagnosis and treatment.

[0139] (2) The more times the fuel supply is stopped by stopping the treatment during the first fixed amount of operation, the more damage accumulates in the exhaust purification device.

[0140] Therefore, when a shutdown process is performed, the engine control unit 300 uses the second mapping data to calculate the permissible misfire rate Rmf. Thus, the engine control unit 300 calculates the anomaly determination threshold Cmfth1 in such a way that the more times the fuel supply is stopped, the smaller the anomaly determination threshold Cmfth1 becomes. Therefore, the engine control unit 300 can perform catalyst anomaly diagnosis processing that reflects the accumulation of damage corresponding to the number of times the combustion supply is stopped.

[0141] (3) In addition to catalyst malfunction diagnosis, the engine control unit 300 also performs misfire malfunction diagnosis processing. When a stop process is performed, there is a possibility of performing a false misfire detection, indicating that a misfire has occurred in a cylinder where fuel supply has been stopped. As a result, it may be judged as having a high frequency of misfires and misdiagnosed as a misfire malfunction. In contrast, when the stop process is performed, the engine control unit 300 performs a correction in the misfire malfunction diagnosis processing to exclude the number of times fuel supply has been stopped from the second misfire count Cmf2 obtained by the counting process. In addition, the engine control unit 300 makes a correction to reduce the misfire determination threshold Cmfth2 in proportion to the proportion of fuel supply that has actually been provided. Thus, the engine control unit 300 can reliably diagnose misfire malfunctions by reflecting that "there is a cylinder where fuel supply has been stopped".

[0142] (4) In the diagnosis and treatment of misfire anomalies, the misfire anomaly can be diagnosed by excluding the cylinders that have stopped fuel supply from the misfire detection targets. On the other hand, in the diagnosis and treatment of catalyst anomalies, it is not only necessary to exclude the cylinders that have stopped fuel supply from the misfire detection targets, but also to reflect the accumulation of damage to the exhaust purification device caused by the heat generated by supplying oxygen from the cylinders that have stopped fuel supply.

[0143] In the aforementioned engine control unit 300, when a stop process is performed, the decrease in the anomaly determination threshold Cmfth1 is greater than the decrease in the misfire determination threshold Cmfth2. Therefore, it is possible to not only exclude cylinders from the misfire detection pool but also to detect catalyst anomalies that reflect the accumulated damage to the exhaust purification device caused by the heat generated from supplying oxygen to cylinders from which fuel supply has ceased.

[0144] <Example of Change>

[0145] This embodiment can be implemented with the following modifications. This embodiment and the following modifications can be combined with each other within the scope of technical inconsistency.

[0146] The above embodiment illustrates a 6-cylinder engine, but the applicability of the fault diagnosis device is not limited to 6-cylinder engines. Furthermore, the number of cylinders whose fuel supply is stopped during the stop process is not limited to two. For example, in a 4-cylinder engine, when performing a stop process to stop the fuel supply to one of the four cylinders, a second mapping data is prepared by subtracting a quarter of "25 (%)" from the output variable of the mapping data corresponding to the first mapping data. The permissible misfire rate Rmf is then calculated using this second mapping data when the stop process is performed. Additionally, when performing a stop process to stop the fuel supply to two of the four cylinders, a second mapping data is prepared by subtracting two-quarters of "50 (%)" from the output variable of the mapping data corresponding to the first mapping data. Furthermore, if the number of cylinders whose fuel supply is stopped during the stop process changes, mapping data is prepared corresponding to the number of stopped cylinders, and the permissible misfire rate Rmf is calculated using the mapping data corresponding to the number of stopped cylinders at that time.

[0147] The scheme for calculating the anomaly threshold Cmfth1 is not limited to the scheme shown in the above embodiments, but is not limited to the scheme shown in the first embodiment. Any scheme that can calculate the anomaly threshold Cmfth1 in a manner that reduces the anomaly threshold Cmfth1 as the number of times the fuel supply is stopped by stopping the process during the first predetermined operation is acceptable.

[0148] In the above embodiment, the rotational variation ΔT30 is set as the value obtained by subtracting the T30[2] required for rotation in the range from ATDC60°CA to ATDC90°CA from the T30[0] required for rotation in the range from TDC to ATDC30°CA. The rotational variation ΔT30 is not limited to this. For example, it can also be set as the value obtained by subtracting the T30 required for rotation in the range from TDC to ATDC30°CA of the cylinder that is the target of misfire determination from the T30 required for rotation in the range from TDC to ATDC30°CA of the previous cylinder that has reached the top dead center of compression.

[0149] In the above embodiment, the change in the rotational speed of the crankshaft 59 within the rotational angle interval below the interval of the occurrence of the compression top dead center, i.e., the rotational change, is quantified by the difference between the time required for rotation within the same rotational angle interval. However, it is not limited to this; it can also be quantified by the ratio between the time required for rotation within the same rotational angle interval.

[0150] In the above embodiment, the instantaneous speed variable, which represents the rotational speed of the crankshaft 59 within the rotational angle interval below the interval at which the compression top dead center occurs to determine the amount of rotational variation, is quantified using the time required for rotation within the same rotational angle interval. However, it is not limited to this; the instantaneous speed variable can also be quantified using speed.

[0151] • The predetermined conditions for allowing the regeneration process to proceed are not limited to those exemplified in the above embodiments. For example, regarding the three conditions (i) to (iii) above, only two of them may be included, or only one of them may be included, for example. Furthermore, the predetermined conditions may include conditions other than the three conditions mentioned above, or none of the three conditions may be included.

[0152] • The stopping process is not limited to regeneration. For example, it could be a process of stopping the fuel supply to a portion of the cylinders to adjust the output of engine 50. Additionally, it could be a process of stopping combustion control in a cylinder when an abnormality occurs. Furthermore, it could be a process of stopping combustion control in only a portion of the cylinders when the oxygen uptake of the three-way catalytic converter falls below a predetermined value, thereby maintaining the air-fuel ratio of the mixture in the remaining cylinders at the stoichiometric air-fuel ratio.

[0153] • In the above embodiment, when an abnormality is diagnosed, a notification process using the warning light 150 is performed. However, the notification process is not limited to the process of using a device that outputs visual information as the operation object. For example, it may also be the process of using a device that outputs auditory information as the operation object.

[0154] • It is not necessary to use the results of the abnormality diagnosis process for the notification process itself. For example, if a misfire abnormality is diagnosed, it is also possible to perform a process to change the control of engine 50 to an operating state that makes it difficult to misfire.

[0155] The estimation of the build-up amount (DPM) is not limited to the embodiments illustrated above. For example, the build-up amount (DPM) can also be estimated based on the pressure difference between the upstream and downstream sides of the GPF and the intake air volume Ga. Specifically, when the pressure difference is large, the build-up amount (DPM) is estimated to be a larger value compared to when it is small; even if the pressure difference is the same, when the intake air volume Ga is small, the build-up amount (DPM) is estimated to be a larger value compared to when it is large. Here, if the pressure on the downstream side of the GPF is considered a constant value, the aforementioned pressure Pex can be used instead of the differential pressure.

[0156] • The GPF is not limited to a filter carrying a three-way catalyst; it can be a filter alone. Furthermore, the GPF is not limited to being located downstream of the three-way catalyst in the exhaust passage. Additionally, the presence of a GPF is not necessary for the exhaust purification device. For example, even if the exhaust purification device consists only of a three-way catalyst, heating of the exhaust purification device is still required. Therefore, performing the processes illustrated in the above embodiments and their modifications is effective.

[0157] The example shown illustrates how an anomaly is diagnosed when the fire count, which is above a predetermined value, exceeds a judgment threshold. Alternatively, the fire rate can be calculated by dividing the fire count when the monitoring count exceeds the judgment threshold by the judgment threshold. In other words, an anomaly can also be diagnosed based on the fire rate exceeding a threshold (fire rate).

[0158] • Vehicle 10 is not limited to a plug-in hybrid electric vehicle. It may also be a hybrid electric vehicle without a configuration for external charging. It is not limited to a series-parallel hybrid electric vehicle; for example, it may also be a parallel hybrid electric vehicle or a series hybrid electric vehicle. Of course, it is not limited to hybrid electric vehicles; for example, it may also be a vehicle in which the power generation device of vehicle 10 is only an engine 50.

[0159] • Alternatively, catalyst anomaly diagnosis and misfire anomaly diagnosis can be performed in the system control unit 100 to diagnose anomalies. In this case, the system control unit 100 becomes an anomaly diagnosis device.

[0160] In the above embodiment, the engine control unit 300, serving as an anomaly diagnostic device, performs software processing. However, this is merely an example. For instance, the anomaly diagnostic device may also include dedicated hardware circuitry (e.g., an ASIC) that executes at least a portion of the software processing performed in the above embodiment. That is, the anomaly diagnostic device can be configured as any of the following (a) to (c): (a) The anomaly diagnostic device includes a processing circuitry that executes all processing according to a program and a storage device for storing the program. That is, the anomaly diagnostic device includes a software execution device. (b) The anomaly diagnostic device includes a processing circuitry that executes a portion of the processing according to a program and a storage device. Furthermore, the anomaly diagnostic device includes dedicated hardware circuitry that executes the remaining processing. (c) The anomaly diagnostic device includes dedicated hardware circuitry that executes all processing. Here, there may be multiple software execution devices and / or dedicated hardware circuitry. That is, the above processing can be executed by a processing circuitry that includes at least one of one or more software execution devices and one or more dedicated hardware circuitry. The storage device for storing the program, i.e., the computer-readable medium, includes all available media that can be accessed using a general-purpose or special-purpose computer.

[0161] The expression "at least one" as used in this specification means "more than one" of the desired options. For example, if there are two options, "at least one" means "only one option" or "both options". As another example, if there are three or more options, "at least one" means "only one option" or "any combination of two or more options".

Claims

1. An abnormality diagnosis device for an internal combustion engine, applicable to the following internal combustion engines: The internal combustion engine has multiple cylinders, and sometimes, in order to supply oxygen to the exhaust purification device, a process is performed to stop the fuel supply to at least one of the multiple cylinders and stop the fuel supply to the remaining cylinders. The abnormality diagnostic device performs: misfire detection processing, detecting the occurrence of misfires in each cylinder based on information about changes in internal combustion engine speed; counting processing, calculating a misfire count representing the number of misfires detected by the misfire detection processing; and catalyst abnormality diagnostic processing, making a diagnosis that an abnormality has occurred in the exhaust purification device based on the misfire count representing the number of misfires detected during a predetermined period of operation of the internal combustion engine. The catalyst malfunction diagnosis process, when the stop procedure is performed during the predetermined period of engine operation, makes a diagnosis that an malfunction has occurred in the exhaust gas purification device when the misfire count is low, compared to when the stop procedure is not performed during the predetermined period of engine operation. If the stop process is performed during the predetermined period of operation of the internal combustion engine, a correction is implemented to exclude the number of times the fuel supply was stopped due to the stop process from the misfire count, which represents the number of times misfires were detected during the predetermined period of operation of the internal combustion engine. Furthermore, an anomaly determination threshold is calculated such that the more times the fuel supply is stopped due to the stop process during the predetermined period of operation, the smaller the anomaly determination threshold becomes. The catalyst anomaly diagnosis process makes a diagnosis that an anomaly has occurred in the exhaust purification device if the corrected misfire count is greater than the anomaly determination threshold.

2. The fault diagnosis device for an internal combustion engine according to claim 1, The anomaly determination threshold is a value obtained by multiplying the average permissible misfire rate by the number of combustion strokes in which fuel is supplied during the predetermined amount of operation. The average permissible misfire rate is obtained by averaging the permissible misfire rate calculated based on the engine load rate and engine speed each time the internal combustion engine reaches top dead center during the predetermined period of operation. When the stop process is performed, the permissible misfire rate calculated based on the internal combustion engine load rate and internal combustion engine speed is reduced compared to when the stop process is not performed.

3. The fault diagnosis device for an internal combustion engine according to claim 1, In addition to the catalyst anomaly diagnosis and treatment, the anomaly diagnosis device also performs fire malfunction anomaly diagnosis and treatment. The misfire anomaly diagnosis process is a process that diagnoses a misfire anomaly when the misfire count (i.e., the second misfire count, which represents the number of misfires detected during a second predetermined period of operation of the internal combustion engine) is greater than a misfire determination threshold. The aforementioned fire anomaly diagnosis and treatment If the stop process is performed during the second predetermined period of operation of the internal combustion engine, a correction is implemented to exclude the number of times fuel supply was stopped due to the stop process from the second misfire count. Furthermore, a correction is implemented to multiply the misfire determination threshold by the proportion of the number of times fuel supply was performed during the second predetermined period of operation to the sum of the number of times the compression top dead center of all cylinders was reached. If the corrected second misfire count is greater than the corrected misfire determination threshold, the misfire anomaly is diagnosed.

4. The abnormality diagnosis device for an internal combustion engine according to claim 3, The anomaly determination threshold for cases where the stop process is not executed is set as the first anomaly determination threshold, and the anomaly determination threshold for cases where the stop process is executed is set as the second anomaly determination threshold. When the fire detection threshold is set as the first fire detection threshold if the stop process is not executed, and the fire detection threshold is set as the second fire detection threshold if the stop process is executed, then... The quotient obtained by dividing the second anomaly determination threshold by the first anomaly determination threshold is smaller than the quotient obtained by dividing the second fire determination threshold by the first fire determination threshold.

Images