Control device for internal combustion engine
The control device improves PM trapping device removal detection by calculating integrated exhaust temperature differences and adjusting thresholds based on air temperature and ignition timing, enhancing accuracy in abnormality diagnosis.
Patent Information
- Application Number
- JP2024063981
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2024-04-11
- Publication Date
- 2025-10-24
AI Technical Summary
Existing control devices for internal combustion engines struggle to accurately determine the removal of PM trapping devices due to variations in exhaust gas temperatures influenced by outside air temperature and ignition timing, especially in low-temperature conditions.
A control device that calculates integrated values of exhaust temperature differences and adjusts determination thresholds based on outside air temperature and ignition timing retard to accurately diagnose PM trapping device removal, incorporating sensors for upstream and downstream exhaust temperatures and a processing circuit for integrated value calculation and abnormality diagnosis.
Enhances the accuracy of abnormality determination by considering outside air temperature and ignition timing influences, ensuring precise detection of PM trapping device status.
Smart Images
Figure 2025161082000001_ABST
Abstract
Description
[Technical Field]
[0001] The present invention relates to a control device for an internal combustion engine. [Background technology]
[0002] A vehicle is known that has a PM trap installed in the exhaust passage of an internal combustion engine to trap particulate matter in the exhaust. The heat of the exhaust gas introduced into the PM trap is consumed through heat exchange with the PM trap. As a result, there is a difference between the change in exhaust gas temperature upstream of the PM trap and the change in exhaust gas temperature downstream of the PM trap in the exhaust passage.
[0003] Patent Document 1 discloses a control device for an internal combustion engine that performs a removal diagnosis to determine whether a PM trapping device has been removed. The control device disclosed in Patent Document 1 calculates an index value that indicates the magnitude of deviation between the upstream exhaust gas temperature and the downstream exhaust gas temperature using the exhaust gas temperature upstream of the PM trapping device and the exhaust gas temperature downstream of the PM trapping device. The control device determines that the PM trapping device has been removed when the index value is smaller than a determination threshold value. [Prior art documents] [Patent documents]
[0004] [Patent Document 1] Japanese Patent Publication No. 2020-172942 Summary of the Invention [Problem to be solved by the invention]
[0005] For example, when the outside air temperature is low, the temperature of the exhaust gas flowing through the exhaust passage and the temperature of the PM trapping device are less likely to rise. Thus, the exhaust gas temperature upstream of the PM trapping device and the exhaust gas temperature downstream of the PM trapping device are affected by the circumstances when the removal decision is made. When determining whether to remove a PM trapping device using an index value that indicates the magnitude of the difference between the upstream exhaust gas temperature and the downstream exhaust gas temperature, it is necessary to set an appropriate decision threshold value according to the circumstances in order to make an accurate decision. [Means for solving the problem]
[0006] The control device for an internal combustion engine for solving the above problems is applied to an internal combustion engine mounted on a vehicle in which a PM trapping device is disposed in an exhaust passage. The control device includes a processing circuit that executes: an upstream-side exhaust temperature indicating the exhaust temperature upstream of the PM trapping device in the exhaust passage; and a downstream-side exhaust temperature indicating the exhaust temperature downstream of the PM trapping device in the exhaust passage; and an integrated value calculation process that calculates an upstream-side integrated value that is an integrated value of the difference between the upstream-side exhaust temperature after start of the internal combustion engine and the upstream-side exhaust temperature at an integration start point; and a downstream-side integrated value that is an integrated value of the difference between the downstream-side exhaust temperature after start of the internal combustion engine and the downstream-side exhaust temperature at the integration start point; an abnormality diagnosis process that executes an abnormality determination that the PM trapping device is in a detached state when, during a determination period after start of the internal combustion engine, a ratio of the upstream-side integrated value to the downstream-side integrated value is smaller than a determination threshold value that is set based on an outside air temperature; and a correction process that corrects the determination threshold value so that the determination threshold value becomes larger as the ignition timing retard amount in the internal combustion engine increases. [Effects of the Invention]
[0007] The control device described above can make an abnormality determination with high accuracy by taking into account not only the influence of the outside air temperature but also the influence of differences in the amount of ignition timing retard. [Brief explanation of the drawings]
[0008] [Figure 1]FIG. 1 is a schematic diagram showing a control device for an internal combustion engine according to a first embodiment and an internal combustion engine to which this control device is applied. [Figure 2] FIG. 2 is a graph showing the transition of the upstream exhaust temperature and the downstream exhaust temperature, where (a) shows the case where the PM trapping device is installed, and (b) shows the case where the PM trapping device is removed. [Figure 3] FIG. 3 is a graph showing the change in the amount of ignition timing retard for each engine water temperature and the change in exhaust temperature, where (a) shows the change in the amount of ignition timing retard, and (b) shows the change in the upstream exhaust temperature and downstream exhaust temperature. [Figure 4] FIG. 4 is a flowchart showing the flow of processing executed in the control device according to the first embodiment. [Figure 5] FIG. 5 is a flowchart showing the flow of processing executed by the control device according to the second embodiment. DETAILED DESCRIPTION OF THE INVENTION
[0009] First Embodiment A first embodiment of a control device for an internal combustion engine will be described with reference to FIGS. <Configuration of an internal combustion engine> FIG. 1 shows a schematic configuration diagram of an internal combustion engine 10 and a control device 100 for the internal combustion engine 10 according to this embodiment.
[0010] The control device 100 is applied to an internal combustion engine 10. The internal combustion engine 10 is mounted on a vehicle in which a PM trapping device 30 is arranged in an exhaust passage 20. The internal combustion engine 10 is a spark-ignition gasoline engine. The internal combustion engine 10 includes an engine body 12 having a plurality of cylinders 11.
[0011] The engine body 12 generates power for driving a vehicle, for example, by combusting fuel injected from a fuel injection valve 13 inside each cylinder 11. The fuel injection method is not limited to direct injection into the cylinder, and may be port injection. In Fig. 1, the illustration of an intake system, spark plugs, etc. is omitted.
[0012] The exhaust passage 20 discharges exhaust gas generated inside each cylinder 11 to the outside air. The exhaust passage 20 is connected to the engine body 12 via an exhaust manifold 21. The exhaust gas generated in each cylinder 11 of the engine body 12 is discharged to the exhaust passage 20 by the exhaust manifold 21.
[0013] The PM trapping device 30 traps particulate matter (hereinafter referred to as PM) contained in the exhaust gas. The PM trapping device 30 is provided midway through the exhaust passage 20. The PM trapping device 30 includes a filter casing 31 and a wall-flow type filter 32 held within the filter casing 31. The filter 32 traps PM in the exhaust gas that is introduced into the PM trapping device 30.
[0014] An upstream exhaust gas temperature sensor 33 and a downstream exhaust gas temperature sensor 34 are provided in the exhaust passage 20. The upstream exhaust gas temperature sensor 33 acquires the upstream exhaust gas temperature Tin. The upstream exhaust gas temperature Tin indicates the exhaust gas temperature upstream of the PM trapping device 30 in the exhaust passage 20. The downstream exhaust gas temperature sensor 34 acquires the downstream exhaust gas temperature Tout. The downstream exhaust gas temperature Tout indicates the exhaust gas temperature downstream of the PM trapping device 30 in the exhaust passage 20.
[0015] An exhaust purification catalyst 40 is provided in the exhaust passage 20 upstream of the PM trapping device 30. A catalyst casing 41 that holds the exhaust purification catalyst 40 is arranged in the exhaust passage 20. The exhaust purification catalyst 40 is provided between the exhaust manifold 21 and the PM trapping device 30. The exhaust purification catalyst 40 is, for example, an oxidation catalyst or a three-way catalyst. In this embodiment, a three-way catalyst is used as the exhaust purification catalyst 40.
[0016] <About the control device> The control device 100 controls the internal combustion engine 10 by controlling an intake device, an ignition plug, a fuel injection valve 13, etc. The intake device is, for example, a throttle valve provided in an intake passage. The control device 100 includes a processing circuit 110 that executes correction processing, integrated value calculation processing, and abnormality diagnosis processing, which will be described later. The processing circuit 110 includes a CPU that executes processing according to a program. The control device 100 includes a memory 120 that stores programs and the like for the processing circuit 110 to execute various processes.
[0017] Output signals from sensors such as an upstream exhaust temperature sensor 33, a downstream exhaust temperature sensor 34, an outside air temperature sensor 200 that detects the outside air temperature, and a water temperature sensor 300 that detects the engine water temperature of the cooling water of the internal combustion engine 10 are input to the control device 100.
[0018] In the internal combustion engine 10, catalyst warm-up control for warming the exhaust purification catalyst 40 to the activation temperature is performed. The catalyst warm-up control is performed by delaying the ignition timing more than during normal engine operation in which the catalyst warm-up control is not being executed in the internal combustion engine 10. The catalyst warm-up control is executed by the control device 100. The control device 100 sets the ignition timing retard amount in the catalyst warm-up control based on the engine water temperature of the internal combustion engine 10 acquired from the water temperature sensor 300. The control device 100 makes the ignition timing retard amount in the catalyst warm-up control smaller as the engine water temperature is lower. Map information regarding the ignition timing retard amount in the catalyst warm-up control for each engine water temperature is set in the memory 120 of the control device 100. In this map information, the ignition timing retard amount for each engine water temperature is set to be smaller as the engine water temperature is lower.
[0019] <Principle for determining removal of PM collection device> If the PM collection device 30 is removed from the exhaust passage 20, it becomes impossible to purify the exhaust. The control device 100 performs an abnormality diagnosis process for detecting that the PM collection device 30 is in a removed state and making an abnormality determination indicating that the PM collection device 30 is removed.
[0020] FIG. 2(a) shows the transitions of the upstream exhaust temperature Tin and the downstream exhaust temperature Tout from time t0, which is the start time of the internal combustion engine 10. In FIG. 2(a), the upstream exhaust temperature Tin and the downstream exhaust temperature Tout obtained at time t0 are each referred to as the starting temperature Ts. The starting temperature Ts for the upstream exhaust temperature Tin is the upstream exhaust temperature Tin obtained at time t0. The starting temperature Ts for the downstream exhaust temperature Tout is the downstream exhaust temperature Tout obtained at time t0. FIG. 2(a) shows the transitions of the upstream exhaust temperature Tin and the downstream exhaust temperature Tout after a cold start in a normal state in which the PM trapping device 30 is installed. A cold start refers to a start in which the internal combustion engine 10 has cooled to a temperature equivalent to the ambient temperature. In this case, as shown in FIG. 2(a), the upstream exhaust temperature Tin rises quickly, while the downstream exhaust temperature Tout rises more slowly than the upstream exhaust temperature Tin. This is because, in a cold state, moisture contained in the exhaust condenses and adheres to the PM trapping device 30. As the internal combustion engine 10 starts operating and the exhaust temperature rises, the upstream exhaust temperature Tin rises. In contrast, until the moisture adhering to the PM trapping device 30 evaporates, the heat of the exhaust passing through the PM trapping device 30 is consumed as the heat of vaporization of the water. Once all the water has evaporated, the temperature of the PM trapping device 30 and the downstream exhaust temperature Tout begin to rise.
[0021] FIG. 2(b) shows the changes in the upstream exhaust temperature Tin and the downstream exhaust temperature Tout after a cold start in an abnormal state in which the PM trapping device 30 is removed. As with FIG. 2(a), FIG. 2(b) also shows the changes in the upstream exhaust temperature Tin, with the upstream exhaust temperature Tin acquired at time t0 as the origin. Also, as with FIG. 2(a), FIG. 2(b) also shows the changes in the downstream exhaust temperature Tout, with the downstream exhaust temperature Tout acquired at time t0 as the origin. The changes in the upstream exhaust temperature Tin in FIG. 2(b) are the same as those in FIG. 2(a). However, as shown in FIG. 2(b), because the PM trapping device 30 is removed in this case, the stagnation of the downstream exhaust temperature Tout that occurs when exhaust gas passes through the PM trapping device 30, as in FIG. 2(a), does not occur. Therefore, the downstream exhaust temperature Tout in FIG. 2(b) begins to rise earlier than in FIG. 2(a). The stagnation of the downstream exhaust temperature Tout that occurs when the PM trapping device 30 is installed is related not only to the heat of vaporization of water but also to the heat capacity of the PM trapping device 30.
[0022] The control device 100 executes an abnormality diagnosis process that utilizes the difference in the transition of the downstream exhaust temperature Tout depending on whether the PM trapping device 30 is present or not to make an abnormality determination that the PM trapping device 30 is removed.
[0023] <Determination method> The processing circuit 110 performs an integrated value calculation process to calculate an upstream integrated value ΣΔTin and a downstream integrated value ΣΔTout. The processing circuit 110 repeatedly acquires the upstream exhaust temperature Tin and the downstream exhaust temperature Tout. The processing circuit 110 calculates the upstream integrated value ΣΔTin and the downstream integrated value ΣΔTout. The processing circuit 110 performs an abnormality determination when the deviation between the upstream integrated value ΣΔTin and the downstream integrated value ΣΔTout during a determination period is smaller than a reference level. The determination period is the period from when the internal combustion engine 10 starts until the downstream exhaust temperature Tout reaches or exceeds a determination temperature Tf. The determination temperature Tf is set to a temperature higher than the dew point. As shown in FIG. 2(b), when the PM trapping device 30 is detached, the downstream exhaust temperature Tout reaches the determination temperature Tf at time t5. In contrast to this, when the PM trapping device 30 is installed as shown in FIG. 2(a), the downstream exhaust temperature Tout reaches the determination temperature Tf at time t10, which is after time t5.
[0024] The upstream-side integrated value ΣΔTin is an integrated value of the difference obtained by subtracting the upstream-side exhaust temperature Tin at the start of integration from the upstream-side exhaust temperature Tin after the start of the internal combustion engine 10. The integration start time is when the internal combustion engine 10 is started. The processing circuit 110 calculates the upstream-side integrated value ΣΔTin by integrating the difference obtained by subtracting the upstream-side exhaust temperature Tin at the start of integration from the upstream-side exhaust temperature Tin during the determination period. The downstream-side integrated value ΣΔTout is an integrated value of the difference obtained by subtracting the downstream-side exhaust temperature Tout at the start of integration from the downstream-side exhaust temperature Tout after the start of the internal combustion engine 10. The processing circuit 110 calculates the downstream-side integrated value ΣΔTout during the determination period by integrating the difference obtained by subtracting the downstream-side exhaust temperature Tout at the start of integration from the downstream-side exhaust temperature Tout. The processing circuit 110 continues to calculate the upstream integrated value ΣΔTin and the downstream integrated value ΣΔTout until the determination period has elapsed.
[0025] In Figures 2(a) and 2(b), the upstream integrated value ΣΔTin corresponds to the area between the start temperature Ts and the upstream exhaust temperature Tin during the determination period. In Figures 2(a) and 2(b), the downstream integrated value ΣΔTout corresponds to the area between the start temperature Ts and the downstream exhaust temperature Tout during the determination period. Comparing Figures 2(a) and 2(b), when the PM trap 30 is removed, the difference between the upstream integrated value ΣΔTin and the downstream integrated value ΣΔTout is smaller than when the PM trap 30 is installed. The magnitude of the difference between the upstream integrated value ΣΔTin and the downstream integrated value ΣΔTout can be obtained by calculating the ratio Ra of the upstream integrated value ΣΔTin to the downstream integrated value ΣΔTout. The ratio Ra is the quotient obtained by dividing the upstream integrated value ΣΔTin by the downstream integrated value ΣΔTout.
[0026] In the abnormality diagnosis process, the control device 100 makes an abnormality diagnosis when the ratio Ra is smaller than the judgment threshold during a judgment period after the start of the internal combustion engine 10. The judgment threshold is set based on the outside air temperature. The lower the outside air temperature at the start of the internal combustion engine 10, the more easily the PM trapping device 30 cools, and therefore the downstream exhaust temperature Tout is less likely to rise. Therefore, the lower the outside air temperature, the larger the ratio Ra. The control device 100 sets the judgment threshold so that the lower the outside air temperature, the larger the judgment threshold. By setting the judgment threshold based on the outside air temperature, it is possible to execute an abnormality diagnosis process that reflects the influence of the outside air temperature.
[0027] When the ignition timing is retarded, the upstream exhaust gas temperature Tin rises. In FIG. 3(a), the amount of ignition timing retard when the engine water temperature is 20 degrees is shown by a solid line, and the amount of ignition timing retard when the engine water temperature is 15 degrees is shown by a dashed line. In catalyst warm-up control, the higher the engine water temperature, the greater the amount of ignition timing retard set. Note that in FIG. 3(a), the graph drops as the amount of ignition timing retard increases.
[0028] In FIG. 3(b), the upstream exhaust temperature Tin and downstream exhaust temperature Tout when the engine water temperature is 20°C are shown by solid lines, and the upstream exhaust temperature Tin and downstream exhaust temperature Tout when the engine water temperature is 15°C are shown by dashed lines. Looking at the trend of the upstream exhaust temperature Tin, the temperature rises faster when the engine water temperature is 20°C than when the engine water temperature is 15°C. On the other hand, looking at the trend of the downstream exhaust temperature Tout, there is no significant difference between when the engine water temperature is 20°C and when the engine water temperature is 15°C. Therefore, the larger the ignition timing retard amount, the faster the upstream exhaust temperature Tin rises, and the larger the ratio Ra. Therefore, the control device 100 performs a correction process to correct the determination threshold so that the larger the ignition timing retard amount in the internal combustion engine 10, the larger the determination threshold becomes. The determination threshold corresponding to the amount of ignition timing retard may be calculated by the processing circuit 110 each time processing is performed, or map information related to the determination threshold corresponding to the amount of ignition timing retard set in the memory 120 may be referenced. When the PM trap 30 is detached, the ratio Ra of the upstream integrated value ΣΔTin to the downstream integrated value ΣΔTout is less affected by the outside temperature, but is affected by the amount of ignition timing retard. Therefore, by correcting the determination threshold based on the amount of ignition timing retard, the determination threshold can be set with an emphasis on the ratio Ra when the PM trap 30 is detached.
[0029] If the retardation of the ignition timing has little effect on the upstream exhaust temperature Tin, the correction process may not be necessary. The control device 100 does not execute the correction process if catalyst warm-up control is not performed after startup.
[0030] <Flow of abnormality diagnosis process> 4 shows a series of steps related to the abnormality diagnosis process in this embodiment. This series of steps is repeatedly executed by the processing circuit 110.
[0031] In S100, the processing circuit 110 determines whether or not the preconditions are met. The preconditions are conditions for determining whether or not the execution of the abnormality diagnosis process is possible or necessary. Examples of the preconditions include that the abnormality diagnosis process for the PM trapping device 30 has not been executed while the internal combustion engine 10 is currently running, and that the various sensors for acquiring parameters necessary for the abnormality diagnosis process are not malfunctioning. If the preconditions are not met (S100: NO), the processing circuit 110 ends the process of FIG. 4.
[0032] If the precondition is met (S100: YES), the processing circuit 110 sets the determination threshold based on the outside air temperature (S110). The processing circuit 110 acquires the outside air temperature from the output signal of the outside air temperature sensor 200 and sets the determination threshold based on the outside air temperature. As described above, the control device 100 sets the determination threshold so that the lower the outside air temperature, the larger the determination threshold. Next, the processing circuit 110 determines whether or not catalyst warm-up control has been executed (S120). Whether or not catalyst warm-up control has been executed is stored in, for example, the memory 120. If catalyst warm-up control has been executed (S120: YES), the processing circuit 110 corrects the determination threshold based on the ignition timing retard amount (S130) and proceeds to S300. As described above, the control device 100 corrects the determination threshold so that the larger the ignition timing retard amount in the internal combustion engine 10, the larger the determination threshold. The processing executed in S130 corresponds to the correction processing described above. If the catalyst warm-up control is not being executed (S120: NO), the processing circuit 110 proceeds to S300 without executing the correction process.
[0033] If the downstream exhaust temperature Tout is equal to or higher than the judgment temperature Tf (S300: YES), the processing circuit 110 calculates the ratio Ra of the upstream integrated value ΣΔTin to the downstream integrated value ΣΔTout (S310). If the downstream exhaust temperature Tout is not equal to or higher than the judgment temperature Tf (S300: NO), the processing circuit 110 repeats the processing of S300. In the processing of S300, the processing circuit 110 continues to calculate the upstream integrated value ΣΔTin and the downstream integrated value ΣΔTout.
[0034] The processing circuit 110 determines whether the ratio Ra of the upstream integrated value ΣΔTin to the downstream integrated value ΣΔTout calculated in S310 is smaller than a determination threshold (S320). If the ratio Ra is smaller than the determination threshold (S320: YES), the processing circuit 110 makes an abnormality determination (S330) and ends the processing of FIG. 4. If the ratio Ra is equal to or greater than the determination threshold (S320: NO), the processing circuit 110 makes a normal determination that the PM trapping device 30 is installed (S340) and ends the processing of FIG. 4. The processing executed from S310 to S340 corresponds to the abnormality diagnosis processing.
[0035] <Actions and Effects of This Embodiment> (1-1) When the PM trapping device 30 is removed, no heat exchange occurs between the exhaust gas introduced into the PM trapping device 30 and the PM trapping device 30. Therefore, the ratio Ra of the upstream integrated value ΣΔTin to the downstream integrated value ΣΔTout becomes smaller than when the PM trapping device 30 is installed.
[0036] When starting the internal combustion engine 10, the lower the outside air temperature, the more difficult it is for the PM trapping device 30 to warm up, and therefore the more difficult it is for the downstream exhaust temperature Tout to rise. Therefore, the lower the outside air temperature, the larger the ratio Ra of the upstream integrated value ΣΔTin to the downstream integrated value ΣΔTout. By setting the determination threshold based on the outside air temperature, it is possible to execute an abnormality diagnosis process that reflects the influence of the outside air temperature.
[0037] Incidentally, the internal combustion engine 10 may perform control to retard the ignition timing of fuel during startup. In such control, the greater the amount of ignition timing retard, the higher the upstream exhaust gas temperature Tin. When the PM trap 30 is installed, even if the upstream exhaust gas temperature Tin is high, the downstream exhaust gas temperature Tout is less likely to rise compared to the upstream integrated value ΣΔTin immediately after startup of the internal combustion engine 10 because the PM trap 30 absorbs exhaust heat. Therefore, the higher the upstream exhaust gas temperature Tin at the start of integration, the greater the ratio Ra of the upstream integrated value ΣΔTin to the downstream integrated value ΣΔTout. In this regard, the control device 100 corrects the determination threshold so that the greater the amount of ignition timing retard of the internal combustion engine 10, the higher the determination threshold. Therefore, by reflecting not only the influence of the outside air temperature but also the influence of differences in the amount of ignition timing retard, abnormality determination can be performed with high accuracy.
[0038] (1-2) The control device 100 described above executes a correction process when catalyst warm-up control by retarding the ignition timing is being performed in the internal combustion engine 10, but does not execute a correction process when catalyst warm-up control is not being performed in the internal combustion engine 10. When catalyst warm-up control by retarding the ignition timing is not being performed, the amount of ignition timing retard is small, or the ignition timing is not retarded. The control device 100 does not execute a correction process when catalyst warm-up control by retarding the ignition timing is not being performed, thereby avoiding the execution of unnecessary processes.
[0039] (1-3) In the above-described control device 100, the determination period is set as the period until the downstream exhaust temperature Tout reaches a determination temperature Tf that is higher than the dew point. By setting the determination period in this manner, if the PM trapping device 30 is installed, the determination period continues until the water present in the PM trapping device 30 evaporates.
[0040] Specifically, when the PM trapping device 30 is installed, heat is taken from the exhaust gas as the heat of vaporization of water present in the PM trapping device 30. Therefore, the downstream exhaust temperature Tout remains below the judgment temperature Tf and the judgment period continues until all the water present in the PM trapping device 30 has evaporated. On the other hand, when the PM trapping device 30 is removed, the water contained in the PM trapping device 30 does not evaporate, so the downstream exhaust temperature Tout does not remain stagnant and the judgment period becomes shorter than when the PM trapping device 30 is installed.
[0041] During the determination period, the upstream-side exhaust temperature Tin is higher than the downstream-side exhaust temperature Tout, so the longer the determination period, the larger the ratio Ra of the upstream-side integrated value ΣΔTin to the downstream-side integrated value ΣΔTout. As described above, when the PM trapping device 30 is installed, the determination period is longer than when the PM trapping device 30 is removed. Therefore, the ratio Ra of the upstream-side integrated value ΣΔTin to the downstream-side integrated value ΣΔTout is likely to be larger than when the PM trapping device 30 is removed. By setting the determination period as described above, the difference between the ratio Ra when the PM trapping device 30 is installed and the ratio Ra when the PM trapping device 30 is removed can be increased. This makes it easier to determine whether the PM trapping device 30 has been removed.
[0042] Second Embodiment A second embodiment of a control device for an internal combustion engine will be described with reference to Figures 1 and 5. Note that the second embodiment differs from the first embodiment in the method of setting the determination threshold value, etc. In the following description, differences from the first embodiment will be mainly described, and the same components as those in the first embodiment will be assigned the same reference numerals and redundant description will be omitted.
[0043] The control device 100 sets the ignition timing retard amount so that the lower the engine water temperature of the internal combustion engine 10, the smaller the ignition timing retard amount. When the engine water temperature is low, the rotation speed of the internal combustion engine 10 does not increase, and misfires are more likely to occur in the internal combustion engine 10. By reducing the ignition timing retard amount when the engine water temperature is low, the ignition timing is brought closer to an ignition timing that is more suitable for combustion, and the occurrence of misfires can be suppressed.
[0044] The processing circuit 110 of this embodiment sets the judgment threshold based on the engine water temperature in the internal combustion engine 10. The processing circuit 110 sets the judgment threshold so that the lower the engine water temperature in the internal combustion engine 10, the smaller the judgment threshold. The greater the amount of ignition timing retard, the higher the upstream exhaust temperature Tin. Because the lower the engine water temperature, the smaller the amount of ignition timing retard is set, the lower the upstream exhaust temperature Tin becomes. In other words, the lower the engine water temperature, the smaller the ratio Ra of the upstream exhaust temperature Tin to the downstream exhaust temperature Tout becomes.
[0045] In this embodiment, the determination threshold is initially set based on the engine water temperature, which is related to the ignition timing retard amount, so correction processing is omitted from the series of processing. Initial setting of the determination threshold based on the engine water temperature is suitable for use when the influence of the engine water temperature on the abnormality diagnosis processing is greater than the influence of the outside air temperature on the abnormality diagnosis processing. Whether the engine water temperature or the outside air temperature has a greater influence depends on, for example, the layout of the exhaust passage 20 of the vehicle in which the internal combustion engine 10 is installed, the type of internal combustion engine 10, the catalyst warm-up retard amount, etc.
[0046] 5 shows a series of steps related to the abnormality diagnosis process in this embodiment. This series of steps is executed by the processing circuit 110. In S100, the processing circuit 110 determines whether the preconditions are met. The preconditions can be the same as those described in the first embodiment. If the preconditions are not met (S100: NO), the processing circuit 110 ends the processing of FIG. 5. If the preconditions are met (S100: YES), the processing circuit 110 sets a determination threshold value based on the engine water temperature (S200). The processing from S300 onwards is the same as the processing of FIG. 4 in the first embodiment, and therefore a description thereof will be omitted.
[0047] <Actions and Effects of This Embodiment> (2) The amount of ignition timing retardation may be set based on the engine water temperature. If the engine water temperature is low, misfires may occur in the internal combustion engine 10. To prevent this, the amount of ignition timing retardation is set to be small. In other words, the lower the engine water temperature, the smaller the amount of ignition timing retardation is set.
[0048] The smaller the amount of ignition timing retard, the lower the upstream exhaust temperature Tin. When the upstream exhaust temperature Tin is low, the temperature difference between the upstream exhaust temperature Tin and the downstream exhaust temperature Tout becomes smaller compared to when the upstream exhaust temperature Tin is high. The ratio Ra of the upstream integrated value ΣΔTin to the downstream integrated value ΣΔTout tends to become smaller the lower the upstream exhaust temperature Tin at the start of integration. In this regard, the above-mentioned control device 100 sets the judgment threshold so that the lower the engine water temperature, the smaller the judgment threshold, and therefore can perform abnormality judgment with high accuracy.
[0049] <Example of change> Each embodiment can be modified as follows: Each embodiment and the following modifications can be combined with each other to the extent that no technical contradiction occurs.
[0050] The ignition timing may be retarded in a control other than the catalyst warm-up control. An example of the control for retarding the ignition timing is control for suppressing the occurrence of knocking in the internal combustion engine 10. In this modification, it may be determined in S120 of FIG. 4 whether the amount of retardation of the ignition timing is equal to or greater than a predetermined amount.
[0051] The control of the internal combustion engine 10 may be performed by a control device other than the control device 100. The control device 100 of this modified example may be configured to obtain the presence or absence of catalyst warm-up control from a control device other than the control device 100 that performs the control of the internal combustion engine 10.
[0052] The determination period may be the period from when the internal combustion engine 10 starts until the upstream exhaust temperature Tin reaches or exceeds a determination temperature that is higher than the dew point. According to this modified example, the downstream exhaust temperature sensor 34 is not required, and therefore the configuration of the internal combustion engine 10 can be simplified.
[0053] The determination period may be a period from when the internal combustion engine is started until a predetermined time has elapsed. According to this modification, the upstream exhaust temperature sensor 33 and the downstream exhaust temperature sensor 34 are not required, which simplifies the configuration of the internal combustion engine 10.
[0054] The exhaust purification catalyst 40 may be omitted from the exhaust passage 20. In this modified example, instead of the exhaust purification catalyst 40, the filter 32 of the PM trapping device 30 may support a three-way catalyst as an exhaust purification catalyst. [Explanation of symbols]
[0055] 10...Internal combustion engine 11...cylinder 12...Engine body 13...Fuel injection valve 20...Exhaust passage 21...Exhaust manifold 30...PM collection device 31...Filter casing 32...Filter 33...Upstream exhaust gas temperature sensor 34...Downstream exhaust gas temperature sensor 40...Exhaust purification catalyst 41...Catalyst casing 100...Control device 110...Processing circuit 120...Memory 200...Outside air temperature sensor 300...Water temperature sensor
Claims
1. A control device for an internal combustion engine that is applied to an internal combustion engine mounted on a vehicle in which a PM trapping device is disposed in an exhaust passage, an integrated value calculation process that repeatedly acquires an upstream exhaust temperature indicating the exhaust temperature upstream of the PM trapping device in the exhaust passage and a downstream exhaust temperature indicating the exhaust temperature downstream of the PM trapping device in the exhaust passage, and calculates an upstream integrated value that is an integrated value of the difference obtained by subtracting the upstream exhaust temperature at an integration start time from the upstream exhaust temperature after the internal combustion engine is started, and a downstream integrated value that is an integrated value of the difference obtained by subtracting the downstream exhaust temperature at the integration start time from the downstream exhaust temperature after the internal combustion engine is started; an abnormality diagnosis process for making an abnormality determination that the PM trapping device is detached when a ratio of the upstream integrated value to the downstream integrated value is smaller than a determination threshold value set based on an outside air temperature during a determination period after the internal combustion engine is started; a processing circuit that executes a correction process to correct the determination threshold value so that the larger the ignition timing retard amount in the internal combustion engine, the larger the determination threshold value. Control device for internal combustion engines.
2. an exhaust gas purification catalyst is provided in the exhaust passage upstream of the PM trapping device; When catalyst warm-up control is being performed by retarding the ignition timing in the internal combustion engine, the correction process is executed, and when catalyst warm-up control is not being performed by retarding the ignition timing in the internal combustion engine, the correction process is not executed. The control device for an internal combustion engine according to claim 1.
3. A control device for an internal combustion engine that is applied to an internal combustion engine mounted on a vehicle in which a PM trapping device is disposed in an exhaust passage, an integrated value calculation process that repeatedly acquires an upstream exhaust temperature indicating the exhaust temperature upstream of the PM trapping device in the exhaust passage and a downstream exhaust temperature indicating the exhaust temperature downstream of the PM trapping device in the exhaust passage, and calculates an upstream integrated value that is an integrated value of the difference obtained by subtracting the upstream exhaust temperature at an integration start time from the upstream exhaust temperature after the internal combustion engine is started, and a downstream integrated value that is an integrated value of the difference obtained by subtracting the downstream exhaust temperature at the integration start time from the downstream exhaust temperature after the internal combustion engine is started; an abnormality diagnosis process that determines that the PM trapping device is detached when the ratio of the upstream integrated value to the downstream integrated value is smaller than a determination threshold during a determination period after the internal combustion engine is started, The processing circuit sets the determination threshold value so that the lower the engine water temperature in the internal combustion engine, the smaller the determination threshold value. Control device for internal combustion engines.
4. The determination period is a period from when the internal combustion engine starts until when the downstream exhaust temperature reaches or exceeds a determination temperature that is higher than the dew point. The control device for an internal combustion engine according to any one of claims 1 to 3.
Citation Information
Patent Citations
Control device for internal combustion engine
JP2020172942A