Control device for internal combustion engines

Abstract

To adequately prevent the filter from overheating during fuel cut-off. [Solution] The internal combustion engine 10 is equipped with a GPF 18 provided in the exhaust passage 15 to collect particulate matter in the exhaust. The control device 100 performs a calculation process to calculate the estimated amount of particulate matter deposited in each of the multiple sub-regions divided along the exhaust flow direction in the GPF 18. The control device 100 performs a modification process and a determination process when fuel cut is performed in the internal combustion engine 10. The modification process is a process to change the sub-regions for which the estimated amount of deposit is updated according to the temperature of the GPF 18. The determination process is a process to determine the risk of overheating of the GPF 18 based on the estimated amount of deposit in the downstream sub-region located downstream among the multiple sub-regions and the temperature of the GPF 18. If the control device 100 determines in the determination process that there is a risk of overheating of the GPF 18, it performs a protection process to suppress overheating of the GPF 18.

Description

Technical Field

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

Background Art

[0002] In the exhaust gas purification system of an internal combustion engine described in Patent Document 1, in a filter provided in an exhaust passage for collecting particulate matter in exhaust gas, the deposition amount of particulate matter is estimated for each of a plurality of sub-regions divided along the exhaust gas flow direction. And when performing a regeneration process for oxidizing and removing the particulate matter deposited in regions other than the sub-region located on the most upstream side, the supply heat amount required is adjusted as follows. That is, in the temperature rising process, the supply heat amount is adjusted in consideration of the deposition amount of particulate matter in the sub-region located upstream of the region where the particulate matter is oxidized and removed. And the adjustment of the supply heat amount is performed by adjusting the supply power to a heater arranged adjacent to the upstream front end of the filter.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When oxygen inflow into the filter due to fuel cut occurs while the filter is in a high temperature state, the particulate matter is oxidized and removed, and the regeneration of the filter is performed. In the regeneration of the filter performed by fuel cut at such a high temperature of the filter, it is difficult to adjust the temperature rise amount and the oxygen inflow amount according to the operating state of the internal combustion engine, so there is a possibility that it becomes difficult to suppress overheating of the filter.

Means for Solving the Problems

[0005] The control device for an internal combustion engine that solves the above problems is applied to an internal combustion engine equipped with a filter in the exhaust passage for collecting particulate matter in the exhaust. The control device performs a calculation process to calculate the estimated amount of particulate matter deposited in each of a plurality of sub-regions divided along the direction of exhaust flow in the filter. The control device performs a modification process and a determination process when fuel cut is performed in the internal combustion engine. The modification process is a process of changing the sub-regions in which the estimated amount of deposit is updated according to the temperature of the filter, and the determination process is a process of determining the risk of overheating of the filter based on the estimated amount of deposit in the downstream sub-region located downstream of the plurality of sub-regions and the temperature of the filter. If the control device determines in the determination process that there is a risk of overheating of the filter, it performs a protection process to suppress overheating of the filter. [Effects of the Invention]

[0006] According to this invention, it is possible to appropriately suppress the overheating of the filter during fuel cut-off. [Brief explanation of the drawing]

[0007] [Figure 1] Figure 1 is a schematic diagram of an internal combustion engine to which one embodiment of the control device is applied. [Figure 2] Figure 2 is a flowchart showing the procedure of processing performed by the control device of the same embodiment. [Modes for carrying out the invention]

[0008] Hereinafter, an embodiment of the control device for an internal combustion engine will be described with reference to Figures 1 and 2. In this embodiment, the upstream side in the exhaust flow direction is referred to as "upstream," and the downstream side in the same exhaust flow direction is referred to as "downstream."

[0009] <Configuration of an internal combustion engine> As shown in Figure 1, the internal combustion engine 10 has multiple cylinders 10a, and an intake passage 13 is connected to the intake port of each cylinder 10a. A throttle valve 14 is provided in the intake passage 13 to adjust the amount of intake air.

[0010] Each cylinder 10a has a combustion chamber equipped with a fuel injection valve 11. In the combustion chamber of each cylinder 10a, a mixture of air drawn in through the intake passage 13 and fuel injected from the fuel injection valve 11 is ignited by a spark discharge and combusted. The exhaust gas produced by the combustion of the mixture in the combustion chamber is discharged into an exhaust passage 15 connected to the exhaust port of the internal combustion engine 10.

[0011] A three-way catalyst 17 is provided in the exhaust passage 15. This three-way catalyst 17 oxidizes hydrocarbons (HC) and carbon monoxide (CO) contained in the exhaust to produce water and carbon dioxide. In addition, the three-way catalyst 17 reduces nitrogen oxides (NOx) contained in the exhaust to produce nitrogen.

[0012] A gasoline particulate filter (hereinafter referred to as GPF) 18 is provided in the exhaust passage 15 downstream of the three-way catalytic converter 17. The GPF 18 is a filter that collects particulate matter (hereinafter referred to as PM) in the exhaust gas, with the three-way catalytic converter supported on top.

[0013] The control device 100 is equipped with a CPU 110, memory 120, etc., and the CPU 110 executes programs stored in the memory 120 to perform various controls on the internal combustion engine 10.

[0014] The control device 100 receives detection signals from various sensors. For example, a crank angle sensor 53 is provided near the crankshaft of the internal combustion engine 10, and the engine rotation speed NE of the internal combustion engine 10 is calculated based on the detection signal from this sensor. The internal combustion engine 10 is also equipped with an air flow meter 54 for detecting the intake air volume GA and a water temperature sensor 55 for detecting the coolant temperature THW of the internal combustion engine 10.

[0015] The control device 100 controls the fuel injection from the fuel injector 11 and the opening degree of the throttle valve 14. In addition, if the output required from the internal combustion engine 10 is "0", the control device 100 performs a fuel cut, stopping fuel injection from the fuel injector 11.

[0016] <Calculation of upstream sediment volume PMf and downstream sediment volume PMr> As shown in Figure 1, in this embodiment, the estimated amount of PM deposited is calculated for each of the two sub-regions divided along the exhaust flow direction in the GPF18. The uppermost sub-region, which is located furthest upstream of the two sub-regions, is designated as the first sub-region A. The downstream sub-region, which is located downstream of the two sub-regions, is designated as the second sub-region B. The control device 100 then calculates the upstream deposit amount PMf, which is the estimated amount of PM deposited in the first sub-region A, and the downstream deposit amount PMr, which is the estimated amount of PM deposited in the second sub-region B, through a calculation process.

[0017] For example, the control device 100 calculates the PM emission amount PA, which is the amount of PM discharged from the internal combustion engine 10 into the exhaust passage 15 per unit time. Then, it calculates the upstream collection amount PAf, which is the amount of PM collected in the first sub-region A per unit time from the PM emission amount PA. The upstream collection amount PAf is, for example, the value obtained by multiplying the above PM emission amount PA by a suitability coefficient.

[0018] Furthermore, the control device 100 calculates the GPF temperature T, which is the temperature of the GPF 18, based on the engine rotational speed NE and the charging efficiency η. In particular, it is preferable that the GPF temperature T calculated at this time be the temperature of the first sub-region A. Then, the control device 100 calculates the upstream combustion amount PBf, which is the amount of PM burned per unit time in the first sub-region A, based on the GPF temperature T, the intake air amount GA, and the currently calculated upstream deposit amount PMf.

[0019] The control device 100 substitutes the value obtained by subtracting the upstream combustion amount PBf from the upstream collection amount PAf into the upstream update amount ΔPMf. Therefore, when the upstream collection amount PAf is greater than the upstream combustion amount PBf, the upstream update amount ΔPMf becomes a positive value, and when the upstream combustion amount PBf is greater than the upstream collection amount PAf, the upstream update amount ΔPMf becomes a negative value.

[0020] The control device 100 updates the upstream deposition amount PMf by adding the upstream update amount ΔPMf to the currently calculated upstream deposition amount PMf. Therefore, when the upstream collection amount PAf is greater than the upstream combustion amount PBf, the value of the upstream deposition amount PMf increases, while when the upstream combustion amount PBf is greater than the upstream collection amount PAf, the value of the upstream deposition amount PMf decreases.

[0021] Similarly, the control device 100 calculates a downstream collection amount PAr, which is the amount of PM collected per unit time in the second partial region B among the PM emissions PA. Note that the downstream collection amount PAr is, for example, the value obtained by subtracting the upstream collection amount PAf from the PM emissions PA.

[0022] Further, the control device 100 calculates a downstream combustion amount PBr, which is the amount of PM burned per unit time in the second partial region B, based on the GPF temperature T, the intake air amount GA, and the currently calculated downstream deposition amount PMr. Note that the GPF temperature T at this time is preferably strictly the temperature of the second partial region B.

[0023] The control device 100 substitutes the value obtained by subtracting the downstream combustion amount PBr from the downstream collection amount PAr into the downstream update amount ΔPMr. Therefore, when the downstream collection amount PAr is greater than the downstream combustion amount PBr, the downstream update amount ΔPMr becomes a positive value, and when the downstream combustion amount PBr is greater than the downstream collection amount PAr, the downstream update amount ΔPMr becomes a negative value.

[0024] The control device 100 updates the downstream deposit amount PMr by adding the downstream update amount ΔPMr to the currently calculated downstream deposit amount PMr. Therefore, if the downstream collection amount PAr is greater than the downstream combustion amount PBr, the value of the downstream deposit amount PMr increases, while if the downstream combustion amount PBr is greater than the downstream collection amount PAr, the value of the downstream deposit amount PMr decreases.

[0025] <Modification and judgment processes when fuel cut is executed> Figure 2 shows the procedure for the processing performed by the control device 100. The series of processes shown in Figure 2 are realized by the CPU 110 executing a program stored in the control device 100's memory 120 at predetermined intervals. Furthermore, in the following, step numbers are represented by numbers preceded by "S".

[0026] In the series of processes shown in Figure 2, the control device 100 determines whether or not fuel cut is currently being performed (S100). If it is determined that fuel cut is being performed (S100: YES), the control device 100 executes the process in S110.

[0027] In the process of S110, the control device 100 determines whether the GPF temperature T is equal to or greater than a predetermined temperature Tref (S110). The predetermined temperature Tref is set in advance to a temperature at which the combustion of PM in the first sub-region A progresses due to the supply of oxygen to the GPF 18, while the combustion of PM in the second sub-region B becomes less likely to progress. For example, it is generally known that the temperature required for the combustion of PM is around 600°, but the above predetermined temperature Tref is higher than 600°.

[0028] Then, in the process of S110, if it is determined that the GPF temperature T is equal to or greater than the predetermined temperature Tref (S110: YES), the control device 100 executes the process of S120. In the S120 process, the control device 100 updates only the upstream deposit amount PMf and does not update the downstream deposit amount PMr. When the S120 process is executed, fuel cut is performed. Therefore, no PM is emitted into the exhaust passage 15 due to the combustion of fuel in the internal combustion engine 10, and the above PM emission PA becomes "0". On the other hand, the upstream combustion amount PBf is set to a value corresponding to the combustion of PM in the first sub-region A. Therefore, the value of the upstream deposit amount PMf decreases, while the value of the downstream deposit amount PMr is not updated and remains at its current value. The S120 process corresponds to updating the estimated deposit amount of the uppermost sub-region, which is the uppermost of the multiple sub-regions.

[0029] On the other hand, in the process of S110, if it is determined that the GPF temperature T is not equal to or greater than the default temperature Tref (S110:NO), that is, if the GPF temperature T is less than the default temperature Tref (S110:NO), the control device 100 executes the process of S130.

[0030] In the S130 process, the control device 100 updates the upstream deposit amount PMf and the downstream deposit amount PMr. Fuel cut is also performed when the S130 process is executed. Therefore, no PM is emitted into the exhaust passage 15 due to the combustion of fuel in the internal combustion engine 10, and the above PM emission amount PA becomes "0". On the other hand, the upstream combustion amount PBf is set to a value corresponding to the combustion of PM in the first sub-region A. Similarly, the downstream combustion amount PBr is set to a value corresponding to the combustion of PM in the second sub-region B. Therefore, both the upstream deposit amount PMf and the downstream deposit amount PMr decrease. The S130 process corresponds to updating the estimated deposit amount in all sub-regions. Furthermore, the S110, S120, and S130 processes correspond to modification processes that change the sub-regions in which the estimated deposit amount of particulate matter is updated according to the filter temperature.

[0031] When either process S120 or process S130 is executed, the control device 100 executes process S140. In the process of S140, the control device 100 performs a determination process to determine whether or not there is a risk of overheating of the GPF18. In the process of S140, the control device 100 determines the risk of overheating of the GPF18 based on the downstream sediment amount PMr, which is the estimated sediment amount of the second sub-region B located downstream of the first sub-region A, and the GPF temperature T. For example, if the downstream sediment amount PMr is greater than or equal to a preset determination value PMrref, and the GPF temperature T is greater than or equal to a preset determination value OTref, the control device 100 determines that there is a risk of overheating occurring in the GPF18.

[0032] If, during the process in S140, it is determined that there is a risk of the GPF18 overheating (S140: YES), the control device 100 performs a protective process to suppress the overheating of the GPF18 (S150). An example of a protective process performed in the process in S150 is to stop the execution of fuel cut by restarting fuel injection from the fuel injection valve 11.

[0033] Then, if the process in S150 is completed, or if a negative result is obtained in the process in S100, or if a negative result is obtained in the process in S140, the control device 100 terminates the execution of this process for the current cycle.

[0034] <Operation and Effects of This Embodiment> (1) The control device 100 of the internal combustion engine 10, which is equipped with a GPF 18 for collecting PM in the exhaust gas in the exhaust passage 15, performs a calculation process to calculate the estimated amount of PM deposited in each of the two sub-regions divided along the direction of exhaust gas flow in the GPF 18. The control device 100 performs a modification process and a determination process when fuel cut is performed in the internal combustion engine 10. The modification process is a process to change the sub-region for which the estimated amount of deposited PM is updated according to the GPF temperature T. The determination process is a process to determine the risk of overheating of the GPF 18 based on the downstream amount PMr, which is the estimated amount of deposited PM in the downstream sub-region located downstream of the two sub-regions, and the GPF temperature T. If the determination process determines that there is a risk of overheating of the GPF 18, the control device 100 performs a protection process to suppress overheating of the GPF 18.

[0035] When oxygen supply is initiated to the high-temperature GPF18 by fuel cut, PM burns upstream of GPF18. On the other hand, because oxygen is consumed by this upstream combustion, PM combustion does not proceed easily downstream of GPF18.

[0036] Thus, when fuel cut is performed while the GPF18 is at a high temperature, PM does not burn uniformly in the direction of exhaust flow within the GPF18. Therefore, the amount of PM accumulated in the second sub-region B, which is the downstream sub-region, may be greater than the amount of PM accumulated in the first sub-region A, which is the upstream sub-region located upstream of the downstream sub-region.

[0037] In this embodiment, when fuel cut is performed, the sub-regions for updating the estimated accumulation amount are changed according to the GPF temperature T. Therefore, even if PM does not burn uniformly in the exhaust flow direction, i.e., burns unevenly, the estimated accumulation amount of PM for each sub-region is appropriately calculated.

[0038] Furthermore, the greater the amount of PM accumulated, the faster the combustion rate when the PM burns, making it more likely for the GPF18 to overheat. In this embodiment, the risk of overheating of the GPF18 is determined based on the downstream accumulation amount PMr, which is the estimated accumulation amount in the downstream sub-region (second sub-region B), and the GPF temperature T. Here, the downstream accumulation amount PMr is the estimated accumulation amount in the downstream sub-region (second sub-region B), where the combustion of PM is less likely to proceed and the accumulation amount is likely to increase when fuel cut is performed when the GPF18 is at a high temperature. Therefore, the risk of overheating of the GPF18 can be appropriately determined.

[0039] Furthermore, if a risk of GPF18 overheating is determined, protective measures are taken to suppress overheating of GPF18, thereby appropriately preventing overheating of GPF18 during fuel cut-off.

[0040] (2) The above modification process includes updating the upstream sediment amount PMf, which is the estimated sediment amount of the uppermost subregion located furthest upstream of the two subregions, if the GPF temperature T is equal to or greater than the default temperature Tref.

[0041] As mentioned above, if fuel cut is implemented when GPF18 is at a high temperature, PM will burn upstream of GPF18, while PM combustion will not proceed as easily downstream of GPF18. Therefore, the amount of PM accumulation will decrease and change upstream of GPF18, while the amount of PM accumulation will not change significantly downstream of GPF18.

[0042] Therefore, in this embodiment, when the GPF temperature T is equal to or higher than the predetermined temperature Tref, only the upstream deposit amount PMf is updated. Consequently, the estimated deposit amount in the subregion where PM burns when the GPF temperature T is higher than or equal to the predetermined temperature Tref can be appropriately updated.

[0043] (3) The above modification process includes updating the estimated sediment amounts for all sub-regions by updating both the upstream sediment amount PMf and the downstream sediment amount PMr when the GPF temperature T is less than the predetermined temperature Tref.

[0044] If fuel cut is implemented when the GPF18 is not at a very high temperature, the combustion of PM upstream of the GPF18 will be suppressed compared to when the GPF18 is at a high temperature, resulting in less oxygen consumption upstream. Consequently, oxygen will be supplied downstream of the GPF18, and PM will burn downstream of the GPF18 as well. In other words, if fuel cut is implemented when the GPF18 is not at a very high temperature, PM combustion will occur in all regions of the GPF18, although the amount of combustion will differ.

[0045] Therefore, in this embodiment, if the GPF temperature T is below the predetermined temperature Tref, the estimated deposit amount for all subregions is updated. Consequently, when the GPF temperature T is below the predetermined temperature Tref, the estimated deposit amount for the subregions where PM burns can be appropriately updated.

[0046] (4) The above protective treatment is a process that stops the execution of fuel cut. When the execution of fuel cut is stopped, the supply of oxygen to GPF18 is cut off, so the combustion of PM is delayed. As a result, the overheating of GPF18 due to the combustion of accumulated PM is suppressed.

[0047] <Example of changes> This embodiment can be implemented with the following modifications. This embodiment and the following modifications can be combined with each other to the extent that they do not contradict each other technically.

[0048] • The number of subregions for which estimated sediment amounts are calculated individually in GPF18 may be two or more. The method for calculating the upstream sediment volume PMf and the downstream sediment volume PMr described in the above embodiment is just one example, and the method for calculating the estimated sediment volume in a sub-region can be modified as appropriate.

[0049] As a protective measure, we decided to stop the fuel cut-off, but other measures may be taken if they can prevent the GPF18 from overheating. The placement position of the GPF18 in the exhaust passage 15 can be changed as appropriate.

[0050] • GPF18 may be a filter that does not support a three-way catalyst. The control device 100 is not limited to one that includes a CPU and memory and performs software processing. For example, the control device 100 may include a dedicated hardware circuit, such as an ASIC, that performs hardware processing for at least a portion of what is processed by software in the above embodiment. That is, the control device 100 may include a processing circuit having any of the following configurations (a) to (c): (a) A processing circuit comprising one or more processing units that perform all of the above processing according to a program, and one or more program storage devices such as ROMs that store the program. (b) A processing circuit comprising one or more processing units and one or more program storage devices that perform a portion of the above processing according to a program, and one or more dedicated hardware circuits that perform the remaining processing. (c) A processing circuit comprising one or more dedicated hardware circuits that perform all of the above processing. The program storage device, i.e., computer-readable medium, includes any available medium that can be accessed by a general-purpose or dedicated computer. [Explanation of Symbols]

[0051] 10...Internal combustion engine 10a...Cylinder 11...Fuel injection valve 13...Intake passage 14...Throttle valve 15...Exhaust passage 17...Through catalytic converter 18...GPF 18...Gasoline particulate filter 53...Crank angle sensor 54...Air flow meter 55...Water temperature sensor 100...Control unit 110...CPU 120...Memory

Claims

1. A control device for an internal combustion engine equipped with a filter in the exhaust passage for collecting particulate matter in the exhaust, In the filter, a calculation process is performed to calculate the estimated amount of particulate matter deposited in each of the multiple sub-regions divided along the direction of exhaust flow. When fuel cut is performed in the aforementioned internal combustion engine, a modification process and a determination process are executed. The modification process is a process of modifying the partial region that updates the estimated deposit amount according to the temperature of the filter, The aforementioned determination process is a process that determines the risk of overheating of the filter based on the estimated amount of sediment in the downstream sub-region located downstream among the plurality of sub-regions and the temperature of the filter. If the determination process determines that there is a risk of the filter overheating, a protective process to suppress the overheating of the filter will be executed. Control device for internal combustion engines.

2. The modification process includes updating the estimated sediment amount of the uppermost subregion, which is the most upstream of the multiple subregions, if the temperature of the filter is above a predetermined temperature. A control device for an internal combustion engine according to claim 1.

3. The modification process includes updating the estimated deposit amount for all of the sub-regions if the temperature of the filter is below a predetermined temperature. A control device for an internal combustion engine according to claim 1.

4. The aforementioned protection process is a process that cancels the execution of the fuel cut. A control device for an internal combustion engine according to claim 1.

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