Control device for an internal combustion engine

Abstract

The present application aims to appropriately suppress excessive warming of a trap in execution of fuel cut. An internal combustion engine is provided with a GPF that traps particulate matter in exhaust gas, provided in an exhaust passage. A control device executes a calculation process in which, for each of a plurality of local regions divided in a flow direction of the exhaust gas in the GPF, an estimated accumulation amount of the particulate matter is calculated. When the internal combustion engine is in execution of fuel cut, the control device executes a change process and a determination process. The change process is a process of changing the local region in which the estimated accumulation amount is updated, in accordance with the temperature of the GPF. The determination process is a process of determining a risk of excessive warming of the GPF, in accordance with the estimated accumulation amount of a downstream-side local region located downstream among the plurality of local regions and the temperature of the GPF. When it is determined in the determination process that there is a risk of excessive warming of the GPF, the control device executes a protection process of suppressing the excessive warming of the GPF.

Description

Technical Field

[0001] This invention relates to a control device for an internal combustion engine. Background Technology

[0002] Patent Document 1 describes an exhaust gas purification system for an internal combustion engine. For each of the multiple localized regions divided along the exhaust flow direction in a trap located in the exhaust passage and trapping particulate matter in the exhaust, the amount of particulate matter accumulated is estimated. Furthermore, the heat supply required for performing a regeneration process to oxidize and remove particulate matter accumulated in regions other than the upstream localized region is adjusted as follows: During heating, the heat supply is adjusted considering the amount of particulate matter accumulated in localized regions located upstream of the region where particulate matter is oxidized and removed. This adjustment of the heat supply is achieved by adjusting the power supplied to a heater positioned adjacent to the upstream front end of the trap.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2016-223356 Summary of the Invention

[0004] When the filter is at a high temperature, if oxygen flows into the filter due to fuel cut-off, particulate matter is oxidized and removed, thus regenerating the filter. In this type of filter regeneration via fuel cut-off at high temperatures, it may be difficult to suppress excessive temperature rise of the filter because it is difficult to adjust the temperature rise or oxygen flow based on the operating state of the internal combustion engine.

[0005] The control device for an internal combustion engine that solves the above-mentioned problems is applicable to internal combustion engines equipped with a trap in the exhaust passage to trap particulate matter in the exhaust gas. The control device performs a calculation process in which an estimated accumulation amount of the particulate matter is calculated for each of a plurality of local regions divided along the exhaust flow direction in the trap. When the internal combustion engine is in the process of fuel cut-off, the control device performs a modification process and a determination process. The modification process involves modifying the local region where the estimated accumulation amount is updated based on the temperature of the trap, and the determination process involves determining the risk of excessive heating of the trap based on the estimated accumulation amount of the downstream local region among the plurality of local regions and the temperature of the trap. If the determination process determines that there is a risk of excessive heating of the trap, the control device performs a protection process to suppress excessive heating of the trap.

[0006] Invention Effects

[0007] According to the invention, excessive heating of the trap during fuel cut-off can be appropriately suppressed. Attached Figure Description

[0008] Figure 1 This is a schematic diagram of an embodiment of the control device applied to an internal combustion engine.

[0009] Figure 2 This is a flowchart illustrating the processing steps performed by the control device in the same embodiment. Detailed Implementation

[0010] The following is for reference. Figures 1 to 2 An embodiment of the control device for an internal combustion engine will be described.

[0011] In addition, in this embodiment, the upstream side in the flow direction of the exhaust gas is referred to as "upstream", and the downstream side in the flow direction of the same exhaust gas is referred to as "downstream".

[0012] <Structure of an Internal Combustion Engine>

[0013] like Figure 1 As shown, the internal combustion engine 10 has multiple cylinders 10a, and the intake port of each cylinder 10a is connected to an intake passage 13. A throttle valve 14 for adjusting the intake air volume is provided in the intake passage 13.

[0014] Each cylinder 10a has a fuel injection valve 11 installed in its combustion chamber. Furthermore, in each cylinder 10a's combustion chamber, 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 burned. The exhaust gas generated from burning the mixture in the combustion chamber is discharged to an exhaust passage 15 connected to the exhaust port of the internal combustion engine 10.

[0015] A three-way catalyst 17 is installed in the exhaust passage 15. The three-way catalyst 17 oxidizes hydrocarbons (HC) or carbon monoxide (CO) contained in the exhaust gas to produce water or carbon dioxide. In addition, the three-way catalyst 17 reduces nitrogen oxides (NOx) contained in the exhaust gas to produce nitrogen.

[0016] A gasoline particulate filter (hereinafter referred to as GPF) 18 is provided in the exhaust passage 15, which is located further downstream of the three-way catalyst 17. In addition, the GPF 18 is a filter that carries the three-way catalyst on the filter for capturing particulate matter (hereinafter referred to as PM) in the exhaust.

[0017] The control device 100 includes a CPU 110, a memory 120, etc. The CPU 110 implements various controls of the internal combustion engine 10 by executing the program stored in the memory 120.

[0018] The control device 100 receives detection signals from various sensors. For example, a crankshaft angle sensor 53 is installed near the crankshaft of the internal combustion engine 10, and the engine speed NE of the internal combustion engine 10 is calculated based on the detection signal from this crankshaft angle sensor 53. Furthermore, the internal combustion engine 10 also includes an air flow meter 54 for detecting the intake air volume GA and a water temperature sensor 55 for detecting the temperature of the cooling water in the internal combustion engine 10, i.e., the cooling water temperature THW.

[0019] The control device 100 controls the fuel injection of the fuel injection valve 11 and the opening of the throttle valve 14. Furthermore, when the output required by the internal combustion engine 10 is "0", the control device 100 performs fuel cut-off to stop fuel injection from the fuel injection valve 11.

[0020] <Calculation of upstream accumulation volume PMf and downstream accumulation volume PMr>

[0021] like Figure 1 As shown, in this embodiment, the estimated accumulation amount of PM is calculated for each of the two local regions divided along the exhaust flow direction in the GPF18. The upstreammost local region among the two local regions is designated as the first local region A. The downstream local region among the two local regions is designated as the second local region B. Furthermore, the control device 100 calculates, through calculation processing, the upstream accumulation amount PMf, which is the estimated accumulation amount of PM in the first local region A, and the downstream accumulation amount PMr, which is the estimated accumulation amount of PM in the second local region B.

[0022] For example, the control device 100 calculates the amount of PM discharged from the internal combustion engine 10 to the exhaust passage 15 per unit time, i.e., the PM emission amount PA. Furthermore, it calculates the amount of PM captured in the first local region A per unit time within this PM emission amount PA, i.e., the upstream capture amount PAf. Additionally, the upstream capture amount PAf is, for example, a value obtained by multiplying a fitness factor by the aforementioned PM emission amount PA.

[0023] Furthermore, the control device 100 calculates the GPF temperature T, which is the temperature of GPF18, based on the internal combustion engine speed NE and the filling efficiency η. Strictly speaking, the GPF temperature T calculated at this time is preferably set to the temperature of the first local region A. Furthermore, the control device 100 calculates the amount of PM burned per unit time in the first local region A, i.e., the upstream combustion amount PBf, based on the GPF temperature T, the intake air volume GA, and the currently calculated upstream accumulation amount PMf.

[0024] The control device 100 substitutes the value obtained by subtracting the upstream combustion amount PBf from the upstream trapping amount PAf into the upstream renewal amount ΔPMf. Therefore, when the upstream trapping amount PAf is greater than the upstream combustion amount PBf, the upstream renewal amount ΔPMf becomes a positive value, and when the upstream combustion amount PBf is greater than the upstream trapping amount PAf, the upstream renewal amount ΔPMf becomes a negative value.

[0025] The control device 100 updates the upstream accumulation amount PMf by adding the currently calculated upstream accumulation amount PMf to the upstream update amount ΔPMf. Therefore, when the upstream capture amount PAf is greater than the upstream combustion amount PBf, the value of the upstream accumulation amount PMf increases; on the other hand, when the upstream combustion amount PBf is greater than the upstream capture amount PAf, the value of the upstream accumulation amount PMf decreases.

[0026] Similarly, the control device 100 calculates the amount of PM captured per unit time in the second local region B within the aforementioned PM emission amount PA, i.e., the downstream capture amount PAr. Furthermore, the downstream capture amount PAr is, for example, a value obtained by subtracting the upstream capture amount PAf from the PM emission amount PA.

[0027] Furthermore, the control device 100 calculates the amount of PM burned per unit time in the second local region B, i.e., the downstream combustion amount PBr, based on the GPF temperature T, the intake air volume GA, and the currently calculated downstream accumulation amount PMr. Additionally, the GPF temperature T at this time is preferably set to the temperature of the second local region B.

[0028] The control device 100 substitutes the value obtained by subtracting the downstream combustion amount PBr from the downstream trapping amount PAr into the downstream renewal amount ΔPMr. Therefore, when the downstream trapping amount PAr is greater than the downstream combustion amount PBr, the downstream renewal amount ΔPMr becomes a positive value, and when the downstream combustion amount PBr is greater than the downstream trapping amount PAr, the downstream renewal amount ΔPMr becomes a negative value.

[0029] The control device 100 updates the downstream accumulation amount PMr by adding the currently calculated downstream accumulation amount PMr to the downstream update amount ΔPMr. Therefore, when the downstream trapping amount PAr is greater than the downstream combustion amount PBr, the value of the downstream accumulation amount PMr increases; on the other hand, when the downstream combustion amount PBr is greater than the downstream trapping amount PAr, the value of the downstream accumulation amount PMr decreases.

[0030] <Change handling and judgment handling during fuel cut-off>

[0031] Figure 2 This indicates the steps of the processing performed by the control device 100. Additionally, Figure 2The series of processes shown are implemented by the CPU 110 executing the program stored in the memory 120 of the control device 100 at predetermined cycles. Furthermore, the step numbers are represented below by numbers beginning with "S".

[0032] exist Figure 2 In the series of processes shown, the control device 100 determines whether it is currently in the process of fuel cut-off (S100). If it is determined that it is in the process of fuel cut-off (S100: Yes), the control device 100 executes the process of S110.

[0033] In the process of S110, the control device 100 determines whether the GPF temperature T is above a predetermined temperature Tref (S110). The predetermined temperature Tref is a temperature preset at which combustion of PM in the first local region A occurs when oxygen is supplied to the GPF18, while combustion of PM in the second local region B is difficult to occur. For example, it is known that the temperature required for PM combustion is typically around 600°C, but the predetermined temperature Tref is a temperature higher than 600°C.

[0034] Furthermore, in the process of S110, if it is determined that the GPF temperature T is above the specified temperature Tref (S110: Yes), the control device 100 executes the process of S120.

[0035] In the S120 process, the control device 100 only updates the upstream accumulation amount PMf, and does not update the downstream accumulation amount PMr. When executing the S120 process, fuel cutoff is performed. Therefore, in a state where PM is not discharged into the exhaust passage 15 along with the combustion of fuel in the internal combustion engine 10, the aforementioned PM discharge amount PA becomes "0". On the other hand, regarding the upstream combustion amount PBf, a value corresponding to the combustion of PM in the first local region A is set. Therefore, the value of the upstream accumulation amount PMf decreases, and the value of the downstream accumulation amount PMr remains at its current value and is not updated. Furthermore, the S120 process is equivalent to updating the estimated accumulation amount of the most upstream local region among multiple local regions.

[0036] On the other hand, in the above-mentioned S110 process, if it is determined that the GPF temperature T is not above the specified temperature Tref (S110: No), that is, if the GPF temperature T is below the specified temperature Tref (S110: No), the control device 100 executes the S130 process.

[0037] In the process of S130, the control device 100 updates the upstream accumulation amount PMf and the downstream accumulation amount PMr. Fuel cutoff is also performed during the execution of S130. Therefore, in a state where PM is not discharged into the exhaust passage 15 along with the combustion of fuel in the internal combustion engine 10, the aforementioned PM discharge amount PA becomes "0". On the other hand, regarding the upstream combustion amount PBf, a value corresponding to the combustion of PM in the first local region A is set. Furthermore, regarding the downstream combustion amount PBr, a value corresponding to the combustion of PM in the second local region B is also set. Therefore, the values ​​of both the upstream accumulation amount PMf and the downstream accumulation amount PMr are reduced. Additionally, the process of S130 is equivalent to updating the estimated accumulation amount of all local regions. Furthermore, the processes of S110, S120, and S130 are equivalent to modification processes that change the local regions that update the estimated accumulation amount of particulate matter based on the temperature of the trap.

[0038] If either process S120 or process S130 is executed, then control device 100 executes process S140.

[0039] In the process of S140, the control device 100 performs a determination process to determine whether there is a risk of excessive heating of GPF18. In the process of S140, the control device 100 determines the risk of excessive heating of GPF18 based on the estimated accumulation amount (i.e., downstream accumulation amount PMr) of the second local region B located downstream of the first local region A and the second local region B, and the GPF temperature T.

[0040] For example, if the downstream accumulation amount PMr is above the preset judgment value PMrref and the GPF temperature T is above the preset judgment value OTref, the control device 100 determines that there is a risk of overheating in the GPF18.

[0041] In the process of S140, if it is determined that there is a risk of excessive heating of GPF18 (S140: Yes), the control device 100 performs a protection process to suppress excessive heating of GPF18 (S150). One example of the protection process performed in S150 is to stop the execution of fuel cut-off by resuming fuel injection from fuel injection valve 11.

[0042] Furthermore, if the processing in S150 ends, or if a negative determination is made in the processing in S100, or if a negative determination is made in the processing in S140, the control device 100 terminates the execution of this processing in the current cycle.

[0043] <Function and Effects of This Implementation Method>

[0044] (1) The control device 100 of the internal combustion engine 10, which has a GPF 18 in the exhaust passage 15 for capturing PM in the exhaust, performs a calculation process. In this calculation process, the estimated amount of PM accumulation is calculated for each of the two local regions divided along the exhaust flow direction in the GPF 18. When the internal combustion engine 10 is in the process of fuel cut-off, the control device 100 performs a change process and a determination process. The change process is to change the local region with the updated estimated accumulation based on the GPF temperature T. The determination process is to determine the risk of excessive heating of the GPF 18 based on the estimated accumulation of the downstream local region located downstream of the two local regions, i.e., the downstream accumulation amount PMr, and the GPF temperature T. Furthermore, if the determination process determines that there is a risk of excessive heating of the GPF 18, the control device 100 performs a protection process to suppress excessive heating of the GPF 18.

[0045] If the oxygen supply to the high-temperature GPF18 is cut off based on fuel cutoff, PM combustion occurs upstream of the GPF18. On the other hand, since oxygen is consumed through this upstream combustion, PM combustion is difficult to occur downstream of the GPF18.

[0046] Thus, when fuel cutoff is implemented while GPF18 is at a high temperature, PM will not burn uniformly within GPF18 in the direction of exhaust flow. Consequently, the amount of PM accumulated in the downstream local area, namely the second local area B, will be greater than the amount of PM accumulated in the upstream local area, namely the first local area A, which is located further upstream than the downstream local area.

[0047] To address this, in this embodiment, during fuel cutoff, the estimated accumulation amount of PM in each local area is updated based on the GPF temperature T. Therefore, even in cases where PM burns unevenly in the exhaust flow direction, the estimated accumulation amount of PM in each local area can be appropriately calculated.

[0048] Furthermore, the greater the PM accumulation, the faster the PM combustion rate, thus increasing the likelihood of excessive GPF18 temperature rise. To address this, in this embodiment, the risk of excessive GPF18 temperature rise is determined based on the estimated accumulation amount in the downstream local area (second local area B), i.e., the downstream accumulation amount PMr, and the GPF temperature T. Here, the downstream accumulation amount PMr is the estimated accumulation amount in the downstream local area (second local area B) where PM combustion is difficult and the accumulation amount tends to increase when fuel cutoff is implemented while GPF18 is at a high temperature. Therefore, the risk of excessive GPF18 temperature rise can be appropriately determined.

[0049] Furthermore, if it is determined that there is a risk of excessive heating of GPF18, a protective process to suppress excessive heating of GPF18 is performed, thus appropriately suppressing excessive heating of GPF18 during fuel cut-off.

[0050] (2) The above change processing includes the following processing: when the GPF temperature T is above the specified temperature Tref, update the estimated accumulation amount of the upstreammost local area in the two local areas, i.e., the upstream accumulation amount PMf.

[0051] As described above, when fuel cutoff is implemented while GPF18 is at a high temperature, PM combustion occurs upstream of GPF18, but combustion of PM is difficult to occur downstream of GPF18. Therefore, the amount of PM accumulation upstream of GPF18 decreases and changes, while the amount of PM accumulation downstream of GPF18 is difficult to change.

[0052] Therefore, in this embodiment, when the GPF temperature T is above the predetermined temperature Tref, only the upstream accumulation amount PMf is updated. Thus, the estimated accumulation amount in the localized area of ​​PM combustion at high temperatures (GPF temperature T above the predetermined temperature Tref) can be appropriately updated.

[0053] (3) The above change processing includes the following processing: when the GPF temperature T is lower than the specified temperature Tref, the upstream accumulation amount PMf and the downstream accumulation amount PMr are updated together, thereby updating the estimated accumulation amount of all local areas.

[0054] When fuel cutoff is implemented when GPF18 is not at such a high temperature, PM combustion upstream of GPF18 is suppressed compared to when GPF18 is at a high temperature, thus reducing oxygen consumption upstream. Therefore, oxygen is still supplied downstream of GPF18, and PM also combusts downstream of GPF18. In other words, PM combustion occurs when fuel cutoff is implemented when GPF18 is not at such a high temperature, but the amount of combustion differs across all localized areas of GPF18.

[0055] Therefore, in this embodiment, when the GPF temperature T is lower than the predetermined temperature Tref, the estimated accumulation amount of all local areas is updated. Thus, it is possible to appropriately update the estimated accumulation amount of PM combustion in local areas where the GPF temperature T is lower than the predetermined temperature Tref.

[0056] (4) The above protection process is to stop the execution of fuel cut-off. If the execution of fuel cut-off is stopped, the oxygen supply to GPF18 is cut off, and therefore the combustion of PM becomes unsmooth.

[0057] Therefore, excessive heating of GPF18 caused by the combustion of accumulated PM can be suppressed.

[0058] <Example of Change>

[0059] This embodiment can be modified as follows. This embodiment and the following modifications can be combined with each other within the scope of technical inconsistency.

[0060] • In GPF18, the number of local regions for calculating and estimating the accumulation amount can be more than two.

[0061] The calculation method for the upstream accumulation volume PMf and the downstream accumulation volume PMr described in the above embodiment is an example, and the calculation method for the estimated accumulation volume in local areas can be appropriately changed.

[0062] • Fuel cut-off was implemented as a protective measure, but other measures can be performed as long as excessive heating of GPF18 can be suppressed.

[0063] • The configuration position of GPF18 in exhaust passage 15 can be changed appropriately.

[0064] • GPF18 can be used as a trap for cases where no three-way catalyst is supported.

[0065] The control device 100 is not limited to a device that performs software processing by having a CPU and memory. For example, the control device 100 may have a dedicated hardware circuit, such as an ASIC, that performs hardware processing on at least a portion of the software processing in the above embodiments. That is, the control device 100 may simply include a processing circuit having any of the following structures (a) to (c): (a) A processing circuit having one or more processing devices that execute all of the above processing according to a program and one or more program storage devices, such as a ROM, that stores the program. (b) A processing circuit having one or more processing devices that execute a portion of the above processing according to a program, one or more program storage devices, and one or more dedicated hardware circuits that execute the remaining processing. (c) A processing circuit having one or more dedicated hardware circuits that execute all of the above processing. The program storage device, i.e., the computer-readable medium, includes any usable medium that is generally or specifically computer-accessible.

[0066] Symbol Explanation

[0067] 10-Internal combustion engine, 10a-Cylinder, 11-Fuel injection valve, 13-Intake passage, 14-Throttle valve, 15-Exhaust passage, 17-Three-way catalytic converter, 18-GPF, 18-Gas particulate filter, 53-Crankshaft angle sensor, 54-Air flow meter, 55-Water temperature sensor, 100-Control device, 110-CPU, 120-Memory.

Claims

1. A control device for an internal combustion engine, wherein the internal combustion engine has a trap in the exhaust passage for capturing particulate matter in the exhaust gas. The control device for the internal combustion engine is characterized in that... The calculation process involves calculating the estimated accumulation amount of the particulate matter for each of several local regions defined in the collector along the exhaust flow direction. Furthermore, when the internal combustion engine is in the process of fuel cut-off, the control device of the internal combustion engine performs change processing and decision processing. The change process involves updating the local area containing the estimated accumulation amount based on the temperature of the trap. The determination process involves assessing the risk of excessive temperature rise in the trap based on the estimated accumulation amount in the downstream local area of ​​the multiple local areas and the temperature of the trap. If the determination process determines that there is a risk of excessive temperature rise in the trap, the control device of the internal combustion engine performs a protection process to suppress excessive temperature rise in the trap.

2. The control device for an internal combustion engine according to claim 1, characterized in that, The change processing includes the following process: when the temperature of the trap is above a specified temperature, updating the estimated accumulation amount of the upstreammost upstream local region in the plurality of local regions.

3. The control device for an internal combustion engine according to claim 1, characterized in that, The change processing includes the following steps: if the temperature of the trap is lower than a specified temperature, update the estimated accumulation amount of all the local areas.

4. The control device for an internal combustion engine according to claim 1, characterized in that, The protection process involves suspending the execution of the fuel cut-off.

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