Control device for internal combustion engine

Abstract

To provide a control device for an internal combustion engine capable of suppressing a blockage of a PM collection action due to adhesion of condensation water to a filter.SOLUTION: A control device for an internal combustion engine is applied to the internal combustion engine mounted to a vehicle in which a filter for collecting PMs is disposed in an exhaust passage. The control device for the internal combustion engine executes temperature rise processing for raising an upstream side exhaust temperature that is a temperature of exhaust gas upstream of the filter in the exhaust passage until condensation water of the filter reaches a vaporized state after start of the internal combustion engine.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a control device for an internal combustion engine. [Background technology]

[0002] An internal combustion engine is known in which a filter is installed in the exhaust passage. The filter substrate has pores that trap PM. The pores trap PM in the exhaust, thereby purifying the exhaust gas that passes through the filter.

[0003] Because moisture is present in the exhaust gas of an internal combustion engine, condensation of the moisture in the exhaust gas occurs in the exhaust passage. As an example, condensed water, which is the condensed water of the exhaust gas, may remain on the filter after the internal combustion engine is stopped. If the condensed water is left adhering to the filter, the condensed water may freeze and damage the filter. The exhaust gas purification device described in Patent Document 1 raises the temperature of the filter to a temperature higher than the evaporation temperature of water when the filter temperature is below a predetermined temperature when the internal combustion engine is stopped, so as to evaporate the condensed water adhering to the filter. By evaporating the condensed water on the filter when the internal combustion engine is stopped in this way, damage to the filter due to frozen condensed water is prevented. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-190341 Summary of the Invention [Problem to be solved by the invention]

[0005] Even if the condensed water on the filter is evaporated when the internal combustion engine is stopped as in Patent Document 1, when the internal combustion engine is restarted, condensed water formed from the moisture in the exhaust gas may adhere to the filter until the exhaust passage and filter are sufficiently warmed up. When condensed water is adsorbed into the pores of the filter, the pores become less able to trap PM in the exhaust gas, impeding the filter's ability to capture PM. [Means for solving the problem]

[0006] The internal combustion engine for solving the above problem is a control device for an internal combustion engine mounted on a vehicle and having a filter for trapping PM disposed in an exhaust passage. After starting the internal combustion engine, the control device for the internal combustion engine executes a temperature increase process to increase an upstream exhaust gas temperature, which is the temperature of the exhaust gas upstream of the filter in the exhaust passage, until condensed water on the filter reaches a vaporized state. [Effects of the Invention]

[0007] According to the above configuration, the condensed water on the filter can be quickly vaporized, thereby preventing the PM trapping function from being hindered by the condensed water adhering to the filter. [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 one embodiment and an internal combustion engine to which this control device is applied. [Figure 2] FIG. 2 is a timing chart showing the transition of the state at the start of an internal combustion engine to which a conventional control device is applied, where (a) shows the state of the ignition switch, (b) shows the engine speed, (c) shows the upstream exhaust temperature, (d) shows the filter bed temperature, (e) shows the downstream exhaust temperature, (f) shows the amount of condensed water on the filter, (g) shows the filter collection rate, and (h) shows the state of the catalyst warm-up process. [Figure 3] FIG. 3 is a flowchart showing the flow of processing executed in the control device according to the first embodiment. [Figure 4]FIG. 4 is a timing chart showing the transition of the state at the start of an internal combustion engine to which the control device of the first embodiment is applied, where (a) shows the state of the ignition switch, (b) shows the rotation speed of the internal combustion engine, (c) shows the upstream exhaust temperature, (d) shows the filter bed temperature, (e) shows the downstream exhaust temperature, (f) shows the amount of condensed water on the filter, (g) shows the filter collection rate, (h) shows the state of the catalyst warm-up process, and (i) shows the state of the bed temperature process. [Figure 5] FIG. 5 is a flowchart showing the flow of processing executed by the control device according to the second embodiment. [Figure 6] FIG. 6 is a flowchart showing the flow of processing executed in the control device according to the third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] First Embodiment A first embodiment of a control device for an internal combustion engine will be described below with reference to FIGS. 1 to 4. FIG.

[0010] 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 the first embodiment. 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 filter 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 11 having a plurality of cylinders.

[0011] The engine body 11 generates power for driving a vehicle, for example, by combusting fuel injected from the fuel injection valves 12 inside each cylinder. The fuel injection method is not limited to direct injection into the cylinder, and may be port injection. In FIG. 1, the cylinders, intake system, spark plugs, etc. are not shown. An exhaust passage 20 is connected to the engine body 11 so that exhaust gas generated inside each cylinder is discharged to the outside air.

[0012] The filter 30 captures particulate matter (hereinafter referred to as PM) contained in the exhaust gas. The filter 30 is a gasoline particulate filter. The filter 30 is, for example, a wall-flow type filter. The filter 30 is held in a filter casing 31 connected to the exhaust pipe 21 of the exhaust passage 20.

[0013] An exhaust temperature sensor 32 is provided in the exhaust passage 20. The exhaust temperature sensor 32 acquires a downstream exhaust temperature Tout. The downstream exhaust temperature Tout is the temperature of the exhaust gas downstream of the filter 30 in the exhaust passage 20. The exhaust temperature sensor 32 outputs an output signal related to the acquired downstream exhaust temperature Tout to the control device 100.

[0014] An electrically heated catalyst (hereinafter referred to as EHC) 40 is provided in the exhaust passage 20 to purify the exhaust gas upstream of the filter 30. The EHC 40 generates heat when energized. The EHC 40 includes a catalyst casing 41 connected to the exhaust pipe 21 of the exhaust passage 20. The catalyst casing 41 holds a catalyst carrier for the EHC 40.

[0015] <About the control device> The control device 100 controls the internal combustion engine 10 by controlling the fuel injection valve 12, the intake system, the spark plugs, etc. The intake system is, for example, a throttle valve. The control device 100 includes a CPU 110 that executes various processes according to a program. The control device 100 is provided with a memory 120 that stores programs and the like that the CPU 110 uses to execute various processes. The control device 100 acquires information about the internal combustion engine 10, such as the engine speed and load factor, from the internal combustion engine 10. The engine speed is the number of revolutions per unit time of the output shaft of the internal combustion engine 10.

[0016] The control device 100 receives output signals from sensors such as an ignition sensor 200, a water temperature sensor 300, an A / F sensor 400, and an outside air temperature sensor 500. The ignition sensor 200 acquires the on / off operation of an ignition switch (hereinafter referred to as IGSW) of a vehicle equipped with an internal combustion engine 10. The water temperature sensor 300 acquires the coolant temperature of the internal combustion engine 10. The A / F sensor 400 acquires the air-fuel ratio of the internal combustion engine 10. The outside air temperature sensor 500 acquires the outside air temperature.

[0017] The control device 100 executes a catalyst warm-up process to promote warm-up of the EHC 40, for example, during a cold start of the internal combustion engine 10. A cold start refers to starting the internal combustion engine 10 from a state in which the internal combustion engine 10 has cooled to a temperature equivalent to the ambient temperature. The control device 100 determines whether the EHC 40 is in an unwarmed state based on the coolant temperature of the internal combustion engine 10, etc. Then, if the control device 100 determines that the EHC 40 is in an unwarmed state, it executes the catalyst warm-up process. By executing the catalyst warm-up process, exhaust emissions can be reduced when the internal combustion engine 10 is started and immediately after it is started.

[0018] The catalyst warm-up process is performed by at least one of a first warm-up method and a second warm-up method. The first warm-up method is a method of increasing the temperature of the exhaust gas flowing into the EHC 40. In the first warm-up method, the control device 100 performs ignition retard, which sets the ignition timing of the internal combustion engine 10 to a timing later than normal. When the warm-up of the EHC 40 is completed, the control device 100 stops the ignition retard, thereby ending the catalyst warm-up process. The second warm-up method is a method of applying a voltage to the EHC 40. In the second warm-up method, the control device 100 applies a voltage to the EHC 40, causing the EHC 40 to generate heat.

[0019] <Regarding conventional internal combustion engine starting> With reference to FIG. 2, the transition of the state of the internal combustion engine 10 during startup under conventional control will be described. As shown in FIG. 2(a), when the IGSW is turned on at time t10, the internal combustion engine 10 starts to operate at time t11. As the internal combustion engine 10 starts, the rotation speed of the internal combustion engine 10 increases, as shown in FIG. 2(b). In the example of FIG. 2, as shown in FIG. 2(h), catalyst warm-up processing starts at time t11. Thereafter, the catalyst warm-up processing continues until time t12, when warm-up of the EHC 40 is completed. Time t12 is the time when the temperature of the EHC 40 has risen sufficiently.

[0020] Between time t11 and time t12, the execution of the catalyst warm-up process causes an upstream exhaust gas temperature Tin, which is the temperature of the exhaust gas upstream of the filter 30 in the exhaust passage 20, to rise, as shown in FIG. 2(c). For example, the upstream exhaust gas temperature Tin is the temperature of the exhaust gas between the EHC 40 and the filter 30 in the exhaust passage 20. As the temperature of the exhaust gas flowing into the filter 30 rises, the bed temperature Tf of the filter 30 also rises, as shown in FIG. 2(d). As the bed temperature Tf of the filter 30 rises, the downstream exhaust gas temperature Tout also rises, as shown in FIG. 2(e).

[0021] Here, as shown in FIG. 2(d), the increase in the bed temperature Tf of the filter 30 stagnates at the dew point. This is because the thermal energy of the exhaust gas is used to vaporize the condensed water on the filter 30. The condensed water on the filter 30 is generated when moisture in the exhaust gas from the internal combustion engine 10 condenses after the internal combustion engine 10 starts. The condensed water on the filter 30 includes at least one of water that flows into the filter 30 after moisture in the exhaust gas condenses in the exhaust pipe 21, and water that is generated when moisture in the exhaust gas condenses inside the filter 30. The bed temperature Tf of the filter 30 stagnates at the dew point until the condensed water on the filter 30 is vaporized.

[0022] The bed temperature Tf of the filter 30 is lowest when the internal combustion engine 10 is started, and therefore the amount of condensed water Mw generated on the filter 30 after the internal combustion engine 10 is started varies depending on the bed temperature Tf of the filter 30 at the start of the internal combustion engine 10. The amount of condensed water generated on the filter 30 at the start of the internal combustion engine 10 decreases over time, as shown in FIG. 2(f).

[0023] When the catalyst warm-up process ends at time t12, the upstream exhaust temperature Tin drops, as shown in FIG. 2(c). If the catalyst warm-up process ends with condensed water remaining on the filter 30 as shown in FIG. 2, the upstream exhaust temperature Tin drops as the catalyst warm-up process ends, and the rate of decrease per unit time of the condensed water on the filter 30 decreases, as shown in FIG. 2(f). Time t20 is the time when the downstream exhaust temperature Tout reaches a first temperature T1, as shown in FIG. 2(e). The first temperature T1 is a temperature higher than the dew point. In the example of FIG. 2, all of the condensed water on the filter 30 evaporates at time t20.

[0024] However, when water adheres to the filter 30, the water enters the pores that trap PM, reducing the filter 30's collection efficiency. Therefore, if condensed water adheres to the filter 30 when the internal combustion engine 10 is started, the filter 30's inherent ability to capture PM is hindered. As shown in FIG. 2(g), when condensed water adheres to the filter 30, the collection efficiency of the filter 30 increases as the amount of condensed water decreases. If the catalyst warm-up process is terminated while condensed water remains on the filter 30, the upstream exhaust temperature Tin decreases, delaying the evaporation of all the condensed water from the filter 30. As a result, the filter 30's ability to capture PM may be hindered when the internal combustion engine 10 is started.

[0025] <About temperature rise treatment> The control device 100 executes a temperature increase process after starting the internal combustion engine 10. The temperature increase process is a process for increasing the upstream exhaust temperature Tin until the condensed water on the filter 30 reaches a vaporized state. The control device 100 continues to execute the temperature increase process after executing the catalyst warm-up process. More specifically, by executing the temperature increase process, the upstream exhaust temperature Tin is maintained at the same level as during the catalyst warm-up process after executing the catalyst warm-up process. Note that the "state in which the condensed water on the filter 30 has vaporized" may be a state in which all of the condensed water on the filter 30 has vaporized, or a state in which enough condensed water remains on the filter 30 that all of the condensed water is quickly vaporized after the temperature increase process is completed.

[0026] The control device 100 acquires the downstream exhaust temperature Tout from the exhaust temperature sensor 32. The control device 100 executes a temperature increase process until the downstream exhaust temperature Tout becomes equal to or higher than the first temperature T1, which indicates that the condensed water on the filter 30 is vaporizing. As described above, the first temperature T1 is a temperature higher than the dew point. The first temperature T1 may be the dew point. The first temperature T1 is set to a temperature that can determine that the bed temperature Tf of the filter 30 is a predetermined temperature, depending on the characteristics of the filter 30. The predetermined temperature is, for example, 100 degrees, at which the condensed water vaporizes.

[0027] The control device 100 performs temperature rise processing using at least one of a first temperature rise method and a second temperature rise method. The first temperature rise method is a method of raising the temperature of the exhaust gas flowing out from the internal combustion engine 10. In the first temperature rise method, the control device 100 raises the upstream exhaust gas temperature Tin by implementing ignition retardation. The second temperature rise method is a method of applying a voltage to the EHC 40. In the second temperature rise method, the control device 100 causes the EHC 40 to generate heat by applying a voltage to the EHC 40. As the EHC 40 generates heat, the temperature of the exhaust gas flowing out from the EHC 40 rises, and therefore the upstream exhaust gas temperature Tin rises. The temperature rise processing maintains the upstream exhaust gas temperature Tin at the same level as during catalyst warm-up processing.

[0028] <Temperature increase process flow> 3 shows the flow of a series of processes related to the temperature increase process executed in the first embodiment. The control device 100 repeatedly executes the process of FIG.

[0029] The control device 100 determines whether a first precondition is met (S101). A predetermined condition is set as the first precondition. Examples of the first precondition include the following.

[0030] - There are no abnormalities in the sensors required for the temperature rise process. The filter 30 is in a state where it needs to be heated. The condition in which the temperature increase process of the filter 30 is not required is, for example, a condition in which condensed water is unlikely to occur on the filter 30, such as when the outside air temperature is sufficiently high or the bed temperature Tf of the filter 30 is sufficiently high.

[0031] If the first precondition is not met (S101: NO), the control device 100 ends the processing of FIG. 3. If the first precondition is met (S101: YES), the control device 100 determines whether or not catalyst warm-up processing is being performed (S102). Information for determining whether or not catalyst warm-up processing is being performed is stored, for example, in the memory 120 of the control device 100. If catalyst warm-up processing is being performed (S102: YES), the control device 100 ends the processing of FIG. 3.

[0032] If the catalyst warm-up process is not being performed (S102: NO), the control device 100 determines whether the downstream exhaust temperature Tout is lower than the first temperature T1 (S103). If the downstream exhaust temperature Tout is lower than the first temperature T1 (S103: YES), the control device 100 performs the temperature increase process (S104). After starting the temperature increase process, the control device 100 temporarily ends the process of FIG. 3. If the downstream exhaust temperature Tout is equal to or higher than the first temperature T1 (S103: NO), the control device 100 ends the process of FIG. 3. As a result, the control device 100 repeatedly performs the series of processes of FIG. 3 while the internal combustion engine 10 is operating, and continues the temperature increase process until the downstream exhaust temperature Tout becomes equal to or higher than the first temperature T1 (S103: NO).

[0033] <Starting the internal combustion engine when performing temperature increase processing> The transition of the state at the start of the internal combustion engine 10 when the temperature increase process is executed will be described with reference to Fig. 4. Note that the transition of the state up to time t12 is similar to the transition of the state in Fig. 2, and therefore a common description will be omitted.

[0034] As shown in FIG. 4(i), the control device 100 executes the temperature increase process from time t12. The temperature increase process maintains the upstream exhaust temperature Tin from time t12 onward at a temperature equivalent to that during the catalyst warm-up process. Therefore, as shown in FIG. 4(f), the rate of decrease per unit time of the condensed water in the filter 30 from time t12 onward is maintained equivalent to that during the catalyst warm-up process, compared to the case of FIG. 2. Time t13 is the time at which the downstream exhaust temperature Tout reaches the first temperature T1 in the example of FIG. 4. As shown in FIG. 4(f), all of the condensed water in the filter 30 evaporates at time t13, which is earlier than time t20. By evaporating the condensed water in the filter 30 early in this way, the period during which the PM trapping function of the filter 30 is impaired due to the adhesion of condensed water can be shortened, as shown in FIG. 4(g). Therefore, PM emissions during travel of a vehicle equipped with the internal combustion engine 10 can be reduced.

[0035] <Actions and Effects of the First Embodiment> (1-1) According to the control device 100 described above, after the internal combustion engine 10 is started, the temperature raising process is executed until the condensed water on the filter 30 reaches a vaporized state. Therefore, the condensed water on the filter 30 can be quickly vaporized. Therefore, it is possible to suppress the PM trapping action of the filter 30 from being hindered by the adhesion of the condensed water to the filter 30.

[0036] (1-2) The control device 100 described above acquires the downstream exhaust temperature Tout from the exhaust temperature sensor 32. It is possible to determine whether the moisture in the filter 30 has evaporated based on the downstream exhaust temperature Tout, and therefore it is possible to determine from the downstream exhaust temperature Tout that the condensed water in the filter 30 has reached a state of evaporation.

[0037] Second Embodiment A second embodiment of a control device for an internal combustion engine will be described with reference to Figures 1 and 5. The second embodiment differs from the first embodiment in part of the temperature increase process. 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.

[0038] The control device 100 of the second embodiment executes the temperature increase process until the input energy amount Eact reaches the target energy amount Etag. The input energy amount Eact is the total amount of energy input to the filter 30 after the internal combustion engine 10 is started. The target energy amount Etag is the amount of energy required to vaporize condensed water estimated to occur on the filter 30. The control device 100 continues to execute the temperature increase process after executing the catalyst warm-up process until the input energy amount Eact reaches the target energy amount Etag. More specifically, by executing the temperature increase process, the upstream exhaust temperature Tin is maintained at the same level as the exhaust temperature during the catalyst warm-up process until the input energy amount Eact reaches the target energy amount Etag after executing the catalyst warm-up process.

[0039] The control device 100 calculates the amount of condensed water Mw in the filter 30, and calculates the target energy amount Etag from the amount of condensed water Mw. The amount of condensed water Mw generated in the filter 30 is calculated from the bed temperature Tf of the filter 30. The control device 100 stores first map information relating to the relationship between the bed temperature Tf of the filter 30 at the start of the internal combustion engine 10 and the amount of condensed water Mw of the filter 30. The control device 100 calculates the amount of condensed water Mw of the filter 30 based on the first map information from the bed temperature Tf of the filter 30 at the start of the internal combustion engine 10.

[0040] Here, the bed temperature Tf of the filter 30 is calculated by subtracting the current outside air temperature from the bed temperature Tf of the filter 30 when the internal combustion engine 10 was last stopped, multiplying this value by a correction coefficient related to the soak time, and adding the result to the current outside air temperature. The correction coefficient is a coefficient of 1 or less that decreases as the soak time becomes longer. If the internal combustion engine 10 continues to be stopped, the bed temperature Tf will eventually become equal to the outside air temperature. Therefore, the correction coefficient is set to 0 if the soak time is equal to or longer than a predetermined time.

[0041] The amount of condensed water Mw of the filter 30 is calculated by multiplying the difference between the absolute humidity of the exhaust gas temperature at the start of the internal combustion engine 10 and the absolute humidity of the bed temperature Tf of the filter 30 by the surface area of ​​the substrate of the filter 30, and then multiplying this by a predetermined correction coefficient. The absolute humidity of the exhaust gas temperature and the absolute humidity of the bed temperature Tf of the filter 30 can be calculated from the outside air temperature, the air-fuel ratio, the properties of the fuel, the bed temperature Tf of the filter 30, etc. In calculating the actual amount of condensed water Mw, the bed temperature Tf of the filter 30 at the start of the internal combustion engine 10 is dominant, and therefore the calculation process can be simplified by storing in advance the relationship between the bed temperature Tf of the filter 30 and the amount of condensed water Mw as first map information.

[0042] The control device 100 stores second map information relating to the relationship between the amount of condensed water Mw and the amount of energy required to vaporize all of the amount of condensed water Mw. The second map information is set based on the size of the substrate of the filter 30, the characteristics of the internal combustion engine 10, etc. The control device 100 calculates the target amount of energy Etag from the amount of condensed water Mw in the filter 30 based on the second map information. The control device 100 may also store third map information relating to the relationship between the bed temperature Tf of the filter 30 at the start of the internal combustion engine 10 and the amount of energy required to vaporize all of the amount of condensed water Mw generated at the bed temperature Tf of the filter 30. The third map information is map information that combines the first map information and the second map information.

[0043] When the temperature rise process is performed using the first temperature rise method, the input energy amount Eact is calculated based on the amount of retardation of the ignition timing in the internal combustion engine 10. When the temperature rise process is performed using the first temperature rise method, the input energy amount Eact may be calculated from the displacement of the internal combustion engine 10, etc. When the temperature rise process is performed using the second temperature rise method, the input energy amount Eact is calculated based on the power consumption of the EHC 40. The power consumption of the EHC 40 is calculated based on the voltage applied to the EHC 40.

[0044] 5 shows a flow of a series of processes relating to the temperature increase process executed in the second embodiment. The control device 100 repeatedly executes the process of FIG. The control device 100 determines whether or not a first precondition is met (S201). The content of the first precondition is the same as that of the first embodiment. If the first precondition is not met (S201: NO), the control device 100 calculates the input energy amount Eact as described above (S208) and temporarily ends the processing of FIG. 5. If the first precondition is met (S201: YES), the control device 100 determines whether or not the target energy amount Etag has not been calculated (S202).

[0045] If the target energy amount Etag has not been calculated (S202: YES), the control device 100 calculates the amount of condensed water Mw generated in the filter 30 (S203). The control device 100 calculates the amount of condensed water Mw from the bed temperature Tf of the filter 30 based on first map information. The control device 100 calculates the target energy amount Etag from the amount of condensed water Mw (S204). The control device 100 calculates the target energy amount Etag from the amount of condensed water Mw calculated in S203 based on second map information. The calculated target energy amount Etag is stored in the memory 120 of the control device 100. If the target energy amount Etag has not been calculated (S202: NO), the control device 100 acquires the target energy amount Etag (S205).

[0046] The control device 100 acquires the input energy amount Eact (S206). The input energy amount Eact is stored in the memory 120 of the control device 100 so that it can be updated, for example, as needed. The input energy amount Eact is set to 0 (zero) for the first time, for example, when the process of FIG. 5 is executed at the start of the internal combustion engine 10. The control device 100 determines whether or not catalyst warm-up processing is being executed (S207). If catalyst warm-up processing is being executed (S207: YES), the control device 100 calculates the input energy amount Eact (S208) and temporarily ends the process of FIG. 5.

[0047] If the catalyst warm-up process is not being performed (S207: NO), the control device 100 determines whether the input energy amount Eact is smaller than the target energy amount Etag (S209). If the input energy amount Eact is smaller than the target energy amount Etag (S209: YES), the control device 100 executes the temperature increase process (S210). After starting the temperature increase process, the control device 100 calculates the input energy amount Eact (S208) and temporarily ends the process of FIG. 5. If the input energy amount Eact is equal to or greater than the target energy amount Etag (S209: NO), the control device 100 calculates the input energy amount Eact (S208) and temporarily ends the process of FIG. 5.

[0048] <Actions and Effects of Second Embodiment> (2) The filter 30 is heated by the energy input to the filter 30 after the internal combustion engine 10 is started. The amount of input energy Eact input to the filter 30 after the internal combustion engine 10 is started can be calculated from the amount of retardation of the ignition timing in the internal combustion engine 10, the voltage applied to the EHC 40, and the like. According to the control device 100 described above, the temperature raising process is executed until the amount of input energy Eact input to the filter 30 after the internal combustion engine 10 is started reaches the target amount of energy Etag required to vaporize the condensed water. By executing the temperature raising process based on the amount of input energy Eact and the target amount of energy Etag, it is not necessary to obtain the exhaust temperature in the exhaust passage 20, and therefore the configuration of the internal combustion engine 10 can be simplified.

[0049] Third Embodiment A third embodiment of a control device for an internal combustion engine will be described with reference to Figures 1 and 6. In the third embodiment, the conditions under which the temperature increase process is performed are different from those in the first embodiment. 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.

[0050] The control device 100 does not need to execute the temperature increase process under predetermined conditions. By not executing the temperature increase process under predetermined conditions, fuel consumption or electricity consumption related to the temperature increase process can be reduced. The predetermined conditions include a first condition and a second condition.

[0051] The first condition is a condition related to the PM accumulation amount Ms, which indicates the amount of PM accumulated on the filter 30. The control device 100 calculates the amount of PM accumulated on the filter 30 per unit time based on the rotation speed and load factor of the internal combustion engine 10, the bed temperature Tf of the filter 30, and the like. The control device 100 then calculates the PM accumulation amount Ms by integrating the amount of PM accumulated on the filter 30 per unit time. As another example, the control device 100 may calculate the accumulation amount based on the difference between the pressure upstream and downstream of the filter 30 in the exhaust passage 20 and the intake air amount. Specifically, the greater the pressure difference, the greater the calculated PM accumulation amount Ms, and the smaller the intake air amount.

[0052] When the internal combustion engine 10 is started, the control device 100 does not execute the temperature increase process if the PM accumulation amount Ms on the filter 30 is equal to or greater than the threshold value Mthr. As the PM accumulation amount Ms increases, the pores of the filter 30 become filled with PM, and even if condensed water adheres to the filter 30, the condensed water cannot enter the pores of the filter 30. As such, as the PM accumulation amount Ms increases, a decrease in the collection efficiency of the filter 30 due to the adhesion of condensed water becomes less likely to occur. The threshold value Mthr is set to a value that determines whether a decrease in the collection efficiency of the filter 30 due to the adhesion of condensed water will not occur or whether the decrease in the collection efficiency of the filter 30 due to the adhesion of condensed water can be ignored. The threshold value Mthr is set depending on the shape, type, etc. of the substrate of the filter 30.

[0053] The second condition may be a condition related to the bed temperature Tf of the filter 30 when the internal combustion engine 10 is started. When the bed temperature Tf of the filter 30 when the internal combustion engine 10 is started is equal to or higher than a second temperature T2 indicating that condensed water on the filter 30 has evaporated, the control device 100 does not execute the temperature increase process. The second temperature T2 is the dew point. The second temperature T2 may be a temperature higher than the dew point. The control device 100 calculates the current bed temperature Tf of the filter 30. The bed temperature Tf of the filter 30 is calculated by the calculation method exemplified in the second embodiment.

[0054] If the bed temperature Tf of the filter 30 is higher than the second temperature T2 when the internal combustion engine 10 is started, the filter 30 is sufficiently warmed, and condensation is unlikely to occur on the filter 30. Examples of cases in which the bed temperature Tf of the filter 30 is higher than the second temperature T2 when the internal combustion engine 10 is started include when the internal combustion engine 10 is operating intermittently and when the soak time of the internal combustion engine 10 is short.

[0055] Fig. 6 shows the flow of a series of processes for determining whether or not it is necessary to perform a temperature increase process. As in the first embodiment, the control device 100 repeatedly executes the series of processes described with reference to Fig. 3 while the internal combustion engine 10 is operating. Alternatively, as in the second embodiment, the control device 100 repeatedly executes the series of processes described with reference to Fig. 5 while the internal combustion engine 10 is operating. The control device 100 executes the process of Fig. 6 when the internal combustion engine 10 is started.

[0056] The control device 100 determines whether a second precondition is met (S301). A predetermined condition is set as the second precondition. Examples of the second precondition include the following.

[0057] - There are no abnormalities in the sensors required for the temperature rise process. The control device 100 acquires the bed temperature Tf of the filter 30 (S302). The control device 100 acquires the bed temperature Tf by calculating the bed temperature Tf based on the values ​​of various sensors. The control device 100 may acquire the bed temperature Tf stored in the memory 120 of the control device 100 for processing other than the temperature increase processing. If the bed temperature Tf is equal to or higher than the second temperature T2 (S303: YES), the control device 100 prohibits the temperature increase processing (S304) and ends the processing of FIG. 6. If the bed temperature Tf is equal to or higher than the second temperature T2, the temperature increase processing is prohibited, and therefore the temperature increase processing is not performed. Even if the control device 100 proceeds to the processing for performing the temperature increase processing (S104) through the series of processing described with reference to FIG. 3, it does not perform the temperature increase processing. Alternatively, even if the control device 100 proceeds to the processing for performing the temperature increase processing (S210) through the series of processing described with reference to FIG. 5, it does not perform the temperature increase processing.

[0058] If the bed temperature Tf of the filter 30 is not equal to or higher than the second temperature T2 (S303: NO), the control device 100 acquires the PM accumulation amount Ms of the filter 30 (S305). The PM accumulation amount Ms is stored, for example, in the memory 120 of the control device 100. If the PM accumulation amount Ms is equal to or higher than the threshold value Mthr (S306: YES), the control device 100 prohibits the temperature increase process (S304) and ends the process of FIG. 6. If the PM accumulation amount Ms is equal to or higher than the threshold value Mthr, the temperature increase process is prohibited. Therefore, the temperature increase process is not executed in this case either.

[0059] If the PM accumulation amount Ms is not equal to or greater than the threshold value Mthr (S306: NO), the control device 100 ends the processing of FIG. <Actions and Effects of the Third Embodiment> (3-1) PM collected from exhaust gas accumulates on the filter 30 in the exhaust passage 20. When PM accumulates on the filter 30, the pores of the filter 30 are filled with PM. By filling the pores, the PM trapping function is less likely to be hindered by adsorption of condensed water into the pores. The control device 100 described above does not perform a temperature increase process when the amount of PM accumulated on the filter 30, Ms, is equal to or greater than the threshold value, Mthr, and therefore can avoid unnecessary temperature increase process execution.

[0060] (3-2) When the internal combustion engine 10 is started, if the bed temperature Tf of the filter 30 is equal to or higher than the temperature indicating that the condensed water on the filter 30 has evaporated, the moisture in the exhaust gas is less likely to condense on the filter 30. In other words, condensed water is less likely to adhere to the filter 30. The control device 100 described above prohibits the execution of the temperature increase process when the bed temperature Tf of the filter 30 is equal to or higher than the second temperature T2 indicating that the condensed water on the filter 30 has evaporated, and therefore, it is possible to avoid the execution of unnecessary temperature increase processes.

[0061] <Example of change> The above-described embodiments can be modified as follows: The embodiments and the following modifications can be combined with each other to the extent that no technical contradiction occurs.

[0062] Alcohol fuel may be used as the fuel for the internal combustion engine 10. In this modified example, in the calculation of the target energy amount Etag in the second embodiment, the amount of condensed water Mw of the filter 30 may be calculated based on the alcohol concentration of the alcohol fuel.

[0063] The temperature increase process may be performed in an internal combustion engine that does not have a catalyst warm-up function. The EHC 40 may be omitted from the exhaust passage 20. Instead of the EHC 40, an exhaust purification catalyst that does not have a function of generating heat when energized may be disposed in the exhaust passage 20.

[0064] The temperature increase process may be performed even when the catalyst warm-up process is not performed. In this modified example, if the first precondition is met (S101: YES) in the series of processes in Figure 3, the process proceeds to S103.

[0065] A temperature sensor that acquires the bed temperature Tf may be provided in the filter 30. The control device 100 may acquire the bed temperature Tf of the filter 30 from the temperature sensor that acquires the bed temperature Tf. The control device 100 may be configured to prohibit the temperature increase process when the first condition is met, even if the second condition is not met. That is, in this case, when the amount of PM accumulation Ms of the filter 30 is equal to or greater than the threshold value Mthr at the start of the internal combustion engine 10, the control device 100 does not execute the temperature increase process regardless of the bed temperature Tf of the filter 30. For example, the control device 100 may omit the determination regarding the second condition. The control device 100 may prohibit the temperature increase process when either the first condition or the second condition is met.

[0066] The control device 100 may omit the determination of the first condition and may prohibit the temperature increase process when the second condition is met. [Explanation of symbols]

[0067] 10...Internal combustion engine 11...Engine body 12...Fuel injection valve 20...Exhaust passage 21...Exhaust pipe 30...Filter 31...Filter casing 32...Exhaust gas temperature sensor 40...Electrically heated catalyst 41...Catalyst casing 100...Control device 110...CPU 120...Memory 200...Ignition sensor 300...Water temperature sensor 400...A / F sensor 500...Outside air 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 filter that captures PM is disposed in an exhaust passage, After the internal combustion engine is started, a temperature raising process is performed to raise an upstream exhaust gas temperature, which is the temperature of the exhaust gas upstream of the filter in the exhaust passage, until the condensed water on the filter is vaporized. Control device for internal combustion engines.

2. a downstream exhaust temperature is acquired from an exhaust temperature sensor that acquires a downstream exhaust temperature, which is the temperature of exhaust downstream of the filter in the exhaust passage; The temperature increasing process is performed until the downstream exhaust temperature becomes equal to or higher than a first temperature indicating that condensed water on the filter is vaporized. The control device for an internal combustion engine according to claim 1.

3. The temperature raising process is performed until an amount of energy input to the filter after the internal combustion engine is started reaches a target amount of energy required to vaporize condensed water estimated to be generated on the filter. The control device for an internal combustion engine according to claim 1.

4. When the amount of PM accumulated in the filter is equal to or greater than a threshold value at the time of starting the internal combustion engine, the temperature increase process is not executed. The control device for an internal combustion engine according to any one of claims 1 to 3.

5. When the bed temperature of the filter is equal to or higher than a second temperature indicating that condensed water on the filter has evaporated at the time of starting the internal combustion engine, the temperature increase process is not executed. The control device for an internal combustion engine according to any one of claims 1 to 3.

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