Engine control unit
The engine control device predicts and adjusts engine operation to manage temperature rises in multiple exhaust gas purification devices, preventing excessive heating in non-targeted devices.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- TOYOTA JIDOSHA KK
- Filing Date
- 2024-12-05
- Publication Date
- 2026-06-17
AI Technical Summary
In engines with multiple exhaust gas purification devices, heating treatments can cause excessive temperature rises in non-targeted devices, potentially reducing their durability.
An engine control device that predicts the target temperature of one exhaust gas purification device and adjusts engine operation to prevent excessive temperature rises in other devices by modifying ignition timing or other control parameters.
Prevents excessive temperature increases in non-targeted exhaust gas purification devices during heating processes, ensuring effective and controlled temperature management.
Smart Images
Figure 2026098287000001_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to an engine control device.
Background Art
[0002] As an exhaust gas purification device for purifying exhaust gas discharged from an engine to the outside air, there are a catalyst device carrying a catalyst for exhaust gas purification and a filter for collecting particulate matter in exhaust gas, so-called PM (Particulate Matter). Patent Document 1 describes that in an engine equipped with such a filter, in order to burn PM deposited on the filter, a temperature raising process of the filter is performed by delaying the ignition timing.
Prior Art Documents
Patent Documents
[0003]
Patent Document 1
Summary of the Invention
Problems to be Solved by the Invention
[0004] In order to ensure emission performance immediately after engine startup, there is a device in which a start catalyst is installed in a portion upstream of the filter in the exhaust passage. When the ignition timing is retarded, the start catalyst also heats up together with the filter. If the amount of ignition timing retard is increased to enhance the temperature raising effect of the filter, there is a risk that the temperature of the start catalyst will rise excessively.
[0005] Similarly, in an engine with multiple exhaust gas purification devices installed in the exhaust passage, if a heating treatment is performed on one of the exhaust gas purification devices, the temperature of the other exhaust gas purification devices may rise excessively. Furthermore, heating treatment of exhaust gas purification devices can be performed using methods other than ignition timing retardation. In such cases, the temperature of the other exhaust gas purification devices may also rise in response to the heating treatment. Thus, in an engine with multiple exhaust gas purification devices installed in the exhaust passage, if a heating treatment is performed on one of the exhaust gas purification devices, the temperature of the other exhaust gas purification devices may rise excessively. [Means for solving the problem]
[0006] An engine control device that solves the above problems is an engine control device applied to an engine in which a first exhaust gas purification device and a second exhaust gas purification device are installed in the exhaust passage, and is configured to perform a temperature-raising process that raises the temperature of the second exhaust gas purification device through operation of a predetermined engine operation amount, a prediction process that predicts the target temperature which is the convergence value of the temperature of the first exhaust gas purification device if the engine operation is continued under the current operating conditions while the temperature-raising process is being performed, and an adjustment process that, if the target temperature predicted in the prediction process exceeds a predetermined upper limit temperature, adjusts the predetermined engine operation amount to the side in which the temperature rise of the second exhaust gas purification device is suppressed. [Effects of the Invention]
[0007] The above-described engine control device has the effect of appropriately performing a temperature-raising treatment on one of the multiple exhaust gas purification devices installed in the exhaust passage, without causing the temperature of the other exhaust gas purification devices to rise excessively. [Brief explanation of the drawing]
[0008] [Figure 1] Figure 1 is a schematic diagram showing the configuration of one embodiment of an engine control device. [Figure 2] Figure 2 is a flowchart of the filter heating process performed by the engine control unit shown in Figure 1. [Figure 3]Figure 3 is a time chart showing the following changes during the filter heating process by the engine control device in Figure 1: (A) the change in engine load rate, (B) the change in ignition timing retardation, (C) the change in the predicted temperature reached by the start catalyst, and (D) the change in filter temperature. [Modes for carrying out the invention]
[0009] Hereinafter, one embodiment of the engine control device will be described in detail with reference to Figures 1 to 3. <Engine control system configuration> First, the configuration of the engine control device of this embodiment will be described with reference to Figure 1. The engine control device of this embodiment is applied to the engine 10 mounted on the vehicle.
[0010] The engine 10 comprises a combustion chamber 11 for burning the air-fuel mixture, an intake passage 12 which is the path for introducing intake air into the combustion chamber 11, and an exhaust passage 13 which is the path for discharging exhaust gas from the combustion chamber 11. An airflow meter 14 is installed in the intake passage 12 to detect the intake air volume, which is the flow rate of intake air flowing through the intake passage 12. A throttle valve 15 is also installed in the intake passage 12 to adjust the intake air volume by changing the flow area of the intake air passage 12. A starter catalyst 16 is installed in the exhaust passage 13. A filter 17 for collecting particulate matter in the exhaust gas is installed downstream of the starter catalyst 16 in the exhaust passage 13. A three-way catalytic converter is supported on both the starter catalyst 16 and the filter 17. The engine 10 also comprises an in-cylinder injection valve 19 for injecting fuel into the combustion chamber 11 and an ignition device 20 for igniting the air-fuel mixture in the combustion chamber 11 by spark discharge. In this embodiment, the start catalyst 16 corresponds to the first exhaust gas purification device, and the filter 17 corresponds to the second exhaust gas purification device.
[0011] The engine control device of this embodiment is configured as an electronic control unit 30 comprising an arithmetic processing unit 31 and a storage device 32. The storage device 32 stores programs and data for engine control. The electronic control unit 30 performs various processes for engine control by having the arithmetic processing unit 31 read and execute programs from the storage device 32. In addition to the airflow meter 14 mentioned above, the electronic control unit 30 receives detection signals from various sensors, such as a crank angle sensor 22, an intake air temperature sensor 33, and a water temperature sensor 34. The crank angle sensor 22 is a sensor that detects the crank angle, which is the rotation angle of the crankshaft 21 of the engine 10. The intake air temperature sensor 33 is a sensor that detects the intake air temperature, which is the temperature of the intake air introduced into the intake passage 12. The water temperature sensor 34 is a sensor that detects the coolant temperature, which is the temperature of the coolant in the engine 10. Based on the detection results of these sensors, the electronic control unit 30 determines the control parameters of the engine 10, such as throttle opening, fuel injection amount, fuel injection timing, and ignition timing. The electronic control unit 30 controls the engine by driving actuators of the engine 10, such as the throttle valve 15, the in-cylinder injection valve 19, and the ignition device 20, according to the determined input.
[0012] <Filter heating process> The electronic control unit 30 performs a filter heating process as one of the processes for engine control. The filter heating process is performed to regenerate the filter 17 by burning and purifying the particulate matter accumulated on the filter 17. Based on the operating state of the engine 10, the electronic control unit 30 estimates the amount of PM (particulate matter) accumulated on the filter 17. The electronic control unit 30 then performs the filter heating process when the amount of PM exceeds a certain amount.
[0013] Figure 2 shows a flowchart of the filter heating process performed by the electronic control unit 30. During the filter heating process, the electronic control unit 30 repeatedly executes the process shown in Figure 2 at predetermined control cycles.
[0014] When the process shown in Figure 2 is started, the electronic control unit 30 first calculates the filter temperature and catalyst temperature in step S100. The filter temperature represents the estimated temperature of the filter 17, and the catalyst temperature represents the estimated temperature of the start catalyst 16. The electronic control unit 30 calculates the filter temperature and catalyst temperature based on the operating state of the engine 10. Specifically, the electronic control unit 30 calculates the amount of heat in the exhaust gas discharged from the combustion chamber 11 based on the load factor, rotational speed, air-fuel ratio, ignition timing, etc., of the engine 10. Then, the electronic control unit 30 calculates the filter temperature and catalyst temperature using a heat balance model of the exhaust passage 13, based on the calculated amount of heat in the exhaust gas, intake air temperature, vehicle speed, etc.
[0015] Next, in step S110, the electronic control unit 30 calculates the amount of ignition timing retardation required to raise the filter 17 to a temperature at which particulate matter can be burned, based on the filter temperature.
[0016] Next, in step S120, the electronic control unit 30 calculates the catalyst temperature rise based on the engine load factor, engine speed, and the ignition timing retardation amount calculated in step S110. The catalyst temperature rise represents the rise in catalyst temperature when the engine 10 is operated while maintaining the current engine load factor and engine speed, and retarding the ignition timing according to the retardation amount calculated in step S110. Next, in step S130, the electronic control unit 30 adds the catalyst temperature and the catalyst temperature rise, and calculates the sum of these values as the target temperature. The target temperature represents the converged value of the catalyst temperature when the engine 10 is operated under the current operating conditions.
[0017] Next, in step S140, the electronic control unit 30 determines whether the reached temperature exceeds a preset upper limit temperature. The upper limit temperature is set to be a temperature lower than the catalyst temperature at which the durability of the start catalyst 16 decreases due to overheating by a preset margin. When the electronic control unit 30 determines that the reached temperature is below the upper limit temperature (NO), in step S160, it instructs a retardation of the ignition timing by the retard amount calculated in step S110, and ends the process of FIG. 2 in the current control cycle.
[0018] On the other hand, when the electronic control unit 30 determines that the reached temperature is below the upper limit temperature (S140: YES), in step S150, it decreases the ignition timing retard amount so that the reached temperature becomes below the upper limit temperature. More specifically, in this step S150, the electronic control unit 30 calculates the ignition timing retard amount at which the reached temperature becomes the upper limit temperature at the current engine load factor and engine speed. Then, the electronic control unit 30 resets the calculated value as the value of the ignition timing retard amount to be instructed to the ignition device 20. After that, in step S160, the electronic control unit 30 instructs a retardation of the ignition timing by the retard amount decreased in step S150, and ends the process of FIG. 2 in the current control cycle.
[0019] <Operation of the Embodiment> The electronic control unit 30 performs a filter heating process for heating the filter 17 through a retard operation of the ignition timing in order to purify the particulate matter deposited on the filter 17. When the ignition timing is retarded, the thermal efficiency of the engine 10 decreases and the temperature of the exhaust gas discharged from the combustion chamber 11 rises. When the temperature of the exhaust gas rises, the amount of heat received by the filter 17 from the exhaust gas increases, so the filter temperature rises.
[0020] When the filter temperature increase process is carried out, the temperature of the start catalyst 16 installed upstream of the filter 17, that is, the catalyst temperature also increases. Depending on the operating conditions of the engine 10 and the environmental conditions of the start catalyst 16 during the filter temperature increase process, the catalyst temperature may rise excessively and the durability of the start catalyst 16 may decrease. The environmental conditions of the start catalyst 16 here are, for example, the temperature and flow velocity of the outside air flowing around the start catalyst 16.
[0021] In contrast, the electronic control unit 30 performs a prediction process (S120, S130) for predicting the arrival temperature, which is the convergence value of the catalyst temperature when the engine 10 continues to operate under the current operating conditions during the execution of the filter temperature increase process. Then, when the arrival temperature exceeds the upper limit temperature (S140: YES), the electronic control unit 30 performs an adjustment process (S150) for adjusting the ignition timing retard amount to suppress the temperature increase of the filter 17.
[0022] FIG. 3 shows an example of the implementation mode of the filter temperature increase process in the engine control device of the present embodiment. Note that FIG. 3(A) shows the transition of the engine load rate, FIG. 3(B) shows the transition of the ignition timing retard amount, FIG. 3(C) shows the transition of the predicted value of the arrival temperature, and FIG. 3(D) shows the transition of the filter temperature, respectively.
[0023] In the case of Figure 3, the filter heating process is started at time t1. When the filter regeneration process starts, the electronic control unit 30 retards the ignition timing to raise the filter temperature above the temperature TS required for the combustion of particulate matter. When the ignition timing is retarded, the catalyst temperature also rises. While the filter heating process is being performed, the electronic control unit 30 predicts the target temperature, which is the convergence value of the catalyst temperature if the filter heating process is continued under the current operating conditions of the engine 10. Even if the amount of ignition timing retardation is constant, the target temperature changes depending on the operating conditions of the engine 10 and the environmental conditions of the start catalyst 16. For example, if the engine load rate increases, the target temperature will be higher. In the case of Figure 3, the target temperature exceeds the upper limit temperature due to the increase in the engine load rate from time t2 to time t3. In response to this, the electronic control unit 30 reduces the amount of ignition timing retardation during the period from time t2 to time t3 through adjustment processing so that the target temperature remains below the upper limit temperature. As a result, the rise in catalyst temperature above the upper limit temperature is suppressed.
[0024] <Effects of the Embodiment> The engine control device of this embodiment provides the following effects. (1) While the filter heating process, which heats the filter 17 by retarding the ignition timing, is being performed, the electronic control unit 30 performs a prediction process to predict the target temperature, which is the converged value of the catalyst temperature if the engine 10 continues to operate under the current operating conditions. If the target temperature predicted by the prediction process exceeds a predetermined upper limit temperature, the electronic control unit 30 performs an adjustment process to adjust the amount of ignition timing retardation in the filter heating process to the side where the heating of the filter 17 is suppressed. As a result, the temperature of the start catalyst 16 is prevented from rising too high during the filter heating process. Therefore, the engine control device of this embodiment has the effect of appropriately performing the heating process of the filter 17 so that the temperature of the start catalyst 16, which is an exhaust purification device other than the filter 17 installed in the exhaust passage 13, does not rise too high.
[0025] (2) The engine 10 to which the electronic control unit 30 is applied includes a filter 17 installed in the exhaust passage 13 to collect particulate matter in the exhaust, and a start catalyst 16 installed in the exhaust passage 13 upstream of the filter 17. Because the start catalyst 16 is installed upstream of the filter 17, the temperature of the start catalyst 16, which is susceptible to the effects of the filter heating process, can be prevented from rising too high during the filter heating process.
[0026] (Other embodiments) The above embodiment can be implemented with the following modifications. The above embodiment and the following modifications can be combined with each other to the extent that they do not contradict each other technically.
[0027] <Regarding the engine configuration> The engine control device of the above embodiment was applied to an engine 10 in which a start catalyst 16 and a filter 17 were installed in the exhaust passage 13. In an engine in which multiple exhaust purification devices other than the combination of start catalyst 16 and filter 17 are installed in the exhaust passage, it is conceivable to perform a temperature-raising treatment on any of the exhaust purification devices. In such a case, when the temperature-raising treatment is performed, the temperature of exhaust purification devices other than the one targeted for temperature-raising will also rise. Therefore, by applying the control device of the above embodiment to an engine equipped with multiple exhaust purification devices with a configuration different from that of Figure 1, it is possible to suppress the excessive temperature rise of exhaust purification devices other than the target of the treatment during the temperature-raising treatment of the exhaust purification device. The first exhaust purification catalyst, which is the target of the prediction of the target temperature in the prediction treatment, may be installed in a part of the exhaust passage downstream of the second exhaust purification device, which is the target of temperature-raising in the temperature-raising treatment. In addition, the types of the first exhaust purification catalyst and the second exhaust purification device are arbitrary.
[0028] Other components of the engine 10 besides the exhaust system may be modified as appropriate. For example, the engine 10 may be configured to include port injection valves that inject fuel into the intake port instead of the in-cylinder injection valves 19.
[0029] <About prediction processing> In the above embodiment, the predicted temperature to be reached was calculated based on the engine load factor, engine rotational speed, and ignition timing retardation amount, but other parameters may be used to calculate the predicted value.
[0030] In the above embodiment, the target temperature was predicted based on the operating conditions of the engine 10 before the adjustment process was applied. However, the target temperature may be predicted based on the operating conditions after the adjustment process is applied.
[0031] <Regarding adjustment processing> In the adjustment process of the above embodiment, if the target temperature exceeds the upper limit temperature, the amount of ignition timing retardation required to bring the target temperature below the target temperature is calculated, and the amount of ignition timing retardation instructed to the ignition device 20 is reset to that calculated value. The adjustment process may be carried out in other ways. For example, if the target temperature exceeds the upper limit temperature, the amount of ignition timing retardation may be reduced by a fixed amount, or the amount of reduction in the amount of ignition timing retardation may be determined according to the difference between the target temperature and the upper limit temperature. Alternatively, the adjustment process may be carried out to gradually reduce the amount of ignition timing retardation while the target temperature exceeds the upper limit temperature.
[0032] <Regarding the temperature increase process> In the above embodiment, the heating treatment was performed for the purpose of combustion purification of particulate matter accumulated on the filter 17, but the heating treatment may be performed for other purposes. For example, the heating treatment may be performed for the purpose of recovering from poisoning of the exhaust gas purification device or accelerating the warm-up.
[0033] • The temperature-raising process may be performed by a method other than retarding the ignition timing. In an engine in which multiple exhaust gas purification devices are installed in the exhaust passage, if the temperature-raising process is performed by a method other than retarding the ignition timing, the temperature of exhaust gas purification devices other than the target of the temperature-raising process will also rise. Therefore, even when the temperature-raising process is performed by a method other than retarding the ignition timing, it may be possible to adjust the rate at which the temperature rises of the exhaust gas purification devices is controlled by adjusting some engine control amount. Thus, by performing prediction processing and adjustment processing in the manner described below during the temperature-raising process, it is possible to suppress the temperature of exhaust gas purification devices other than the target of the temperature-raising process from rising excessively. Specifically, in this case, the prediction processing is performed as a process to predict the target temperature of the exhaust gas purification devices other than the target of the temperature-raising process. Furthermore, in this case, the adjustment processing is performed as a process to adjust the engine control amount that can adjust the rate at which the temperature rise is controlled so that the temperature rise of the target exhaust gas purification device is suppressed when the target temperature exceeds the upper limit temperature.
[0034] • The temperature-raising process can be implemented, for example, by dithering control. Dithering control is a control method used in multi-cylinder engines where some cylinders perform rich combustion at an air-fuel ratio richer than the stoichiometric air-fuel ratio, while the remaining cylinders perform lean combustion at an air-fuel ratio leaner than the stoichiometric air-fuel ratio. When dithering control is performed, rich exhaust gas with a large amount of unburned fuel components is discharged from the cylinders performing rich combustion, while lean exhaust gas containing excess oxygen is discharged from the cylinders performing lean combustion. In the exhaust passage at this time, the unburned fuel components in the exhaust gas discharged from the cylinders performing rich combustion are burned using the excess oxygen in the exhaust gas discharged from the cylinders performing lean combustion, so the temperature of the exhaust gas increases. As a result, the amount of heat received by the exhaust gas purification device installed in the exhaust passage increases, and the temperature of the exhaust gas purification device rises. In dithering control, when the difference between the air-fuel ratio of the cylinder performing rich combustion and the air-fuel ratio of the cylinder performing lean combustion becomes large, the amount of unburned fuel components burned in the exhaust passage increases, so the temperature-raising effect of the exhaust gas purification device through the temperature-raising process increases. Therefore, by reducing the engine control amount that determines the difference in air-fuel ratio between cylinders performing lean combustion and cylinders performing rich combustion, for example, by reducing the difference in fuel injection amount between cylinders performing lean combustion and cylinders performing rich combustion, it is possible to suppress the temperature rise of exhaust gas purification devices other than those targeted for temperature-raising treatment. Accordingly, in the adjustment process when performing temperature-raising treatment by dither control, a process can be adopted to adjust the engine control amount to reduce the difference in air-fuel ratio when the target temperature exceeds the upper limit temperature.
[0035] • The temperature increase process can also be carried out by supplying unburned fuel to the exhaust passage through post-injection. In this case, adjustments can be made, for example, by reducing the amount of post-injection when the target temperature exceeds the upper limit temperature.
[0036] In engines equipped with a fuel additive valve that adds fuel to the exhaust gas, it is possible to perform a temperature increase treatment by intermittently adding fuel to the exhaust gas using the fuel additive valve. In this case, adjustment treatments can be employed, for example, by reducing the amount of fuel added to the exhaust gas when the target temperature exceeds the upper limit temperature, or by lengthening the period of fuel addition to the exhaust gas. [Explanation of symbols]
[0037] 10 Engines 11 Combustion chamber 12 Intake passage 13 Exhaust passage 14. Airflow meter 15 Throttle valve 16. Start catalyst (first exhaust gas purification device) 17. Filter (Second Exhaust Gas Purification Device) 19. In-cylinder injection valve 20 Ignition system 21 Crank Axle 22 Crank angle sensor 30. Electronic control unit (engine control device) 31 Arithmetic Processing Unit 32 Storage device
Claims
1. An engine control device applied to an engine in which a first exhaust gas purification device and a second exhaust gas purification device are installed in the exhaust passage, A heating process that raises the temperature of the second exhaust gas purification device through operation of a predetermined engine operating amount, During the aforementioned temperature-raising process, a prediction process is performed to predict the target temperature, which is the convergence value of the temperature of the first exhaust gas purification device if the engine operation is continued under the current operating conditions. If the predicted temperature reached in the prediction process exceeds a predetermined upper limit temperature, an adjustment process is performed to adjust the predetermined engine operation amount to the side that suppresses the temperature rise of the second exhaust gas purification device. An engine control device that performs this function.
2. The engine control device according to claim 1, wherein the predetermined engine operation amount is the amount of ignition timing retardation, and the adjustment process is a process of reducing the amount of retardation when the target temperature exceeds the upper limit temperature.
3. The engine control device according to claim 1, wherein the temperature-raising process is a process of performing dither control in which some of the cylinders of the engine perform rich combustion at an air-fuel ratio richer than the stoichiometric air-fuel ratio, and the remaining cylinders perform lean combustion at an air-fuel ratio leaner than the stoichiometric air-fuel ratio, the predetermined engine operation amount is an engine operation amount that determines the difference in air-fuel ratio between the cylinders performing lean combustion and the cylinders performing rich combustion, and the adjustment process is a process of adjusting the predetermined engine operation amount to reduce the difference in air-fuel ratio when the reached temperature exceeds the upper limit temperature.
4. The engine control device according to claim 1, wherein the second exhaust gas purification device is a filter for capturing particulate matter in the exhaust gas, and the heating treatment is performed to burn and purify the particulate matter accumulated on the filter.
5. The engine control device according to claim 4, wherein the first exhaust purification device is a start catalyst installed in the portion of the exhaust passage upstream of the filter.