Control device for internal combustion engines

Abstract

This design suppresses excessive temperature increases in the filter while promoting filter regeneration. [Solution] The internal combustion engine 10 is equipped with a GPF 18, which is a filter for collecting particulate matter in the exhaust gas, in the exhaust passage 15. The control device 100 has a processing circuit 110. The processing circuit 110 performs an increase in fuel quantity when fuel cut is performed in the internal combustion engine 10. This increase in fuel quantity is a process that increases the amount of intake air compared to when the increase in fuel quantity is not performed. The processing circuit 110 performs a process to continue fuel cut if the amount of intake air is such that the difference between the amount of heat generated in the GPF 18 when fuel cut is performed and the amount of heat removed, which is the amount of heat transferred from the GPF 18 to the air flowing into the GPF 18 when fuel cut is performed, is less than or equal to a predetermined value.

Description

Technical Field

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

Background Art

[0002] For example, the internal combustion engine described in Patent Document 1 includes a filter for trapping particulate matter in exhaust gas in an exhaust passage. When fuel cut is executed in this internal combustion engine, air containing oxygen is supplied to the filter. As a result, the particulate matter deposited on the filter burns and decreases, whereby the filter is regenerated.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of Invention

Problems to be Solved by the Invention

[0004] Increasing the intake air amount during fuel cut increases the amount of oxygen supplied to the filter, so that combustion of the particulate matter deposited on the filter can be promoted. However, for example, when the deposition amount of particulate matter on the filter is excessive, the amount of heat generated by the combustion of the particulate matter increases, which may cause the temperature of the filter to rise excessively. Accordingly, in this case, fuel cut is prohibited, so that it is not possible to increase the intake air amount to promote the combustion of particulate matter.

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 has a processing circuit. The processing circuit performs an increase in fuel quantity when fuel cut is performed in the internal combustion engine, and the increase in fuel quantity is a process that increases the amount of intake air compared to when the increase in fuel quantity is not performed. If the amount of intake air is such that the difference between the amount of heat generated in the filter when fuel cut is performed in the internal combustion engine and the amount of heat removed, which is the amount of heat transferred from the filter to the air flowing into the filter when fuel cut is performed, is less than or equal to a predetermined value, the processing circuit performs a process to continue the fuel cut. [Effects of the Invention]

[0006] This internal combustion engine control system can suppress excessive temperature rises in the filter while promoting filter regeneration. [Brief explanation of the drawing]

[0007] [Figure 1] Figure 1 is a schematic diagram showing the configuration of one embodiment of a control device for an internal combustion engine. [Figure 2] Figure 2 is a graph showing the heat balance in GPF. [Figure 3] Figure 3 is a flowchart showing the procedure of processing performed by the control device of the same embodiment. [Modes for carrying out the invention]

[0008] The following describes one embodiment of a control device for an internal combustion engine with reference to Figures 1 to 3. Note that the internal combustion engine in this embodiment is mounted on a vehicle. <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.

[0009] The internal combustion engine 10 is equipped with a fuel injection valve 11 that supplies fuel into each cylinder 10a. 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 (combustion 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.

[0010] The exhaust passage 15 is equipped with a three-way catalyst (hereinafter referred to as "catalyst") 17, which is an exhaust gas purification component that purifies the exhaust gas. This catalyst 17 purifies the exhaust gas by oxidizing hydrocarbons (HC) and carbon monoxide (CO) contained in the exhaust gas, and also purifies the exhaust gas by reducing nitrogen oxides (NOx) contained in the exhaust gas.

[0011] A GPF (Gasoline Particulate Filter) 18 is provided downstream of the catalyst 17 in the exhaust passage 15. The GPF 18 is an exhaust purification component that cleans the exhaust gas and is a filter that collects particulate matter (hereinafter referred to as PM) in the exhaust gas.

[0012] The control device 100 includes a processing circuit 110. The processing circuit 110 includes a CPU that executes processing according to a program and a ROM in which the program is stored. Various controls of the internal combustion engine 10 are performed by the CPU executing the program stored in the ROM.

[0013] The control device 100 receives detection signals from various sensors. These sensors include, for example, a crank angle sensor 52 that detects the crank angle, which is the rotation angle of the crankshaft of the internal combustion engine 10, and an air flow meter 53 that detects the intake air volume GA. Another sensor is a water temperature sensor 54 that detects the coolant temperature THW, which is the temperature of the coolant in the internal combustion engine 10. Yet another sensor is an intake air temperature sensor 55 that detects the intake air temperature THA, which is the temperature of the air drawn into the internal combustion engine 10. Furthermore, there is an accelerator position sensor 56 that detects the accelerator pedal operation amount ACCP, which is the amount the accelerator pedal is operated, and a vehicle speed sensor 58 that detects the vehicle speed SP, which is the vehicle's travel speed.

[0014] The control device 100 calculates the engine rotation speed NE from the crank angle detection result by the crank angle sensor 52. The control device 100 also calculates the engine load ratio KL based on the engine rotation speed NE and the intake air volume GA.

[0015] The control device 100 calculates the required driving output for the vehicle based on the accelerator pedal input amount ACCP and the vehicle speed SP. The control device 100 then controls the required output Pe of the internal combustion engine 10 to satisfy the driving request output.

[0016] The control device 100 controls the fuel injection from the fuel injector 11 and the opening degree of the throttle valve 14. Furthermore, if the requested output Pe of the internal combustion engine 10 is "0", the control device 100 performs a fuel cut, stopping fuel injection from the fuel injector 11. A situation where the requested output Pe is "0" includes, for example, the accelerator off state where the accelerator pedal operation amount ACCP is "0".

[0017] The control device 100 calculates the filter temperature TF, which is the estimated temperature of the GPF18, based on various engine operating conditions. The control device 100 also calculates the PM accumulation amount Ps, which is the amount of PM accumulated in the GPF18, based on the engine rotational speed NE, engine load factor KL, and filter temperature TF, etc.

[0018] When the PM accumulation amount Ps is equal to or greater than a predetermined amount, the control device 100 executes an increase processing while fuel cut is being performed. This increase processing is processing for increasing the intake air amount GA compared to when the increase processing is not executed. The increase of the intake air amount GA by the increase processing is implemented by increasing the opening degree of the throttle valve 14.

[0019] <Regarding Temperature Rise of GPF18> As shown in Figure 2, when fuel cut is performed in the internal combustion engine 10, a large amount of air containing oxygen is supplied to the GPF18. As a result, PM deposited on the GPF18 burns. The temperature of the GPF18 rises due to the amount of heat generated by the combustion of this PM. On the other hand, when air is supplied to the GPF18 during fuel cut, heat is transferred from the GPF18 to the low-temperature air flowing into the GPF18. This transferred heat amount is hereinafter referred to as heat removal amount. Accordingly, the temperature of the GPF18 during execution of fuel cut rises by the amount of heat reception, which is the difference obtained by subtracting the heat removal amount from the heat generation amount. The upper limit value of the allowable heat reception amount for the temperature rise of the GPF18 is defined as a predetermined value α. When the following expression (1) is satisfied, regeneration of the GPF18 can be promoted while suppressing an excessive temperature rise of the GPF18.

[0020] Heat reception amount ≦ predetermined value α…(1) When expression (1) is modified, the following expression (2) is obtained. Heat removal amount ≧ Heat generation amount - predetermined value α…(2) Here, the heat generation amount can be calculated from a well-known model formula including variables such as engine rotational speed NE, engine load factor KL, fuel cut execution time, and PM accumulation amount Ps.

[0021] The heat removal amount can be obtained from a function formula that uses, for example, the intake air amount GA during fuel cut execution, the temperature difference before and after the GPF18 in the exhaust passage 15 during fuel cut execution, the fuel cut execution time, and the specific heat of air as input values, and outputs the heat removal amount.

[0022] The temperature difference before and after the GPF18 is the difference between the temperature of the air immediately before it enters the GPF18 and the temperature of the air immediately after it enters the GPF18. In this embodiment, such a temperature difference is calculated using a physical model. However, such a temperature difference may also be measured directly with a temperature sensor.

[0023] Furthermore, as the intake air volume GA increases, the amount of heat removed also increases; therefore, there is a positive correlation between the intake air volume GA and the amount of heat removed. Therefore, there is a lower limit to the intake air volume GAfc that satisfies equation (2) above, and when the intake air volume GA is equal to or greater than the lower limit to the intake air volume GAfc, the intake air volume GA satisfies equation (1) above. In other words, the intake air volume is such that the difference between the amount of heat generated by the GPF18 when fuel cut is performed and the amount of heat removed when fuel cut is performed is less than or equal to a predetermined value α.

[0024] Therefore, in this embodiment, if the intake air volume GA during fuel cut-off is equal to or greater than the intake air volume GAfc, the fuel cut-off is continued. Figure 3 shows the procedure for the processing circuit 110 to be executed at predetermined intervals. The processing shown in Figure 3 is initiated when the PM accumulation amount Ps is equal to or greater than the predetermined amount mentioned above. Furthermore, in the following, step numbers are represented by numbers preceded by "S".

[0025] When the process shown in Figure 3 is started, the processing circuit 110 determines whether or not there is a request to execute fuel cut (S100). In the process of S100, the processing circuit 110 determines that there is a request to execute fuel cut if, for example, the request output Pe of the internal combustion engine 10 is "0".

[0026] If it is determined during the S100 process that there is a request to perform a fuel cut, the processing circuit 110 increases the intake air volume by performing the above-described increase processing (S110).

[0027] Next, the processing circuit 110 performs a fuel cut-off by stopping fuel injection from the fuel injection valve 11. Next, the processing circuit 110 calculates the amount of heat generated as described above (S130).

[0028] Next, the processing circuit 110 calculates a value obtained by subtracting the predetermined value α from the amount of heat generated, and then calculates the heat difference ΔCV by substituting this calculated value into the heat difference ΔCV (S140). When setting the predetermined value α, it is desirable to consider the temperature drop of the air flowing through the exhaust passage 15, various response delays of the exhaust system, and the state of PM deposition.

[0029] Next, the processing circuit 110 calculates the amount of air GAfc such that the amount of heat removed is equal to or greater than the heat difference ΔCV, using the function formula described above (S150). In this embodiment, the catalyst 17 is located upstream of the GPF 18. Therefore, oxygen contained in the air flowing through the exhaust passage 15 may be consumed by the catalyst 17, and in this case, the molecular weight of the air flowing into the GPF 18 changes, which may affect the amount of heat removed. Accordingly, it is desirable to take into account the oxygen consumption by the catalyst 17 in the function formula described above.

[0030] Next, the processing circuit 110 determines whether the intake air volume GA is equal to or greater than the above air volume GAfc (S160). In the process of S160, if it is determined that the intake air volume GA is equal to or greater than the air volume GAfc (S160: YES), the processing circuit 110 will execute the processes from S110 onward again and will continue to perform the fuel cut.

[0031] On the other hand, in the process of S160, if it is determined that the intake air volume GA is not equal to or greater than the air volume GAfc (S160: NO), the processing circuit 110 stops the execution of fuel cut (S170).

[0032] Then, if the process in S170 is executed, or if a negative determination is made in the process in S100, the processing circuit 110 terminates this process. <Operation and Effects of This Embodiment> (1) The processing circuit 110 performs an enrichment process when fuel cut is performed in the internal combustion engine 10. The enrichment process is a process that increases the amount of intake air compared to when the enrichment process is not performed. By performing this enrichment process, the combustion of PM accumulated in the GPF 18 is promoted compared to when the enrichment process is not performed.

[0033] The processing circuit 110 executes a process to continue fuel cut if the intake air volume GAfc is such that the difference between the amount of heat generated at the GPF18 when fuel cut is performed and the amount of heat removed when fuel cut is performed is less than or equal to a predetermined value α.

[0034] As the amount of air flowing into the GPF18 increases, the amount of heat removed increases, thus suppressing the temperature rise of the GPF18 due to PM combustion. Therefore, in this embodiment, considering the amount of heat removed and the amount of heat generated in the GPF18 due to PM combustion, fuel cut-off is continued when the intake air volume is such that the temperature of the GPF18 does not rise excessively. As a result, it is possible to promote the regeneration of the GPF18 while suppressing an excessive temperature rise of the GPF18.

[0035] (2) The processing circuit 110 performs a process to calculate the amount of air GAfc based on a function formula that calculates the amount of heat removed based on the amount of intake air during fuel cut execution, the temperature difference before and after GPF18 during fuel cut execution, the execution time of fuel cut, and the specific heat of air.

[0036] Therefore, the above intake air volume can be appropriately calculated such that the difference between the heat generated by the GPF18 and the heat removed by the GPF18 is less than or equal to a predetermined value. (3) The processing circuit 110 performs the above increase processing when the amount of particulate matter deposited on the GPF 18 is equal to or greater than a predetermined amount.

[0037] Therefore, if the amount of particulate matter deposited on GPF18 exceeds a predetermined amount, the combustion of particulate matter can be promoted compared to when it is not. <Example of changes> The above embodiment can be implemented with the following modifications. The above embodiment and the following modifications can be combined with each other to the extent that they do not contradict each other technically.

[0038] The above-mentioned process of increasing the intake air volume may be performed regardless of the amount of particulate matter deposited on the GPF18. The input values ​​for the function formula used to calculate the amount of heat removed may be changed as appropriate.

[0039] 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]

[0040] 10...Internal combustion engine 10a...Cylinder 11...Fuel injector 13...Intake passage 14...Throttle valve 15...Exhaust passage 17...Three-way catalytic converter 18...GPF 52...Crank angle sensor 53...Air flow meter 54...Water temperature sensor 55...Intake air temperature sensor 56...Accelerator position sensor 58...Vehicle speed sensor 100...Control unit 110...Processing circuit

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, It has a processing circuit, The aforementioned processing circuit is In the aforementioned internal combustion engine, when fuel cut is performed, an enrichment process is executed, and this enrichment process increases the amount of intake air compared to when the enrichment process is not performed. If the amount of intake air is such that the difference between the amount of heat generated by the filter when the fuel cut is performed in the internal combustion engine and the amount of heat removed (the amount of heat transferred from the filter to the air flowing into the filter when the fuel cut is performed) is less than or equal to a predetermined value, the process of continuing the fuel cut is executed. Control device for internal combustion engines.

2. The processing circuit performs a process to calculate the intake air amount that is less than or equal to the predetermined value, based on the intake air amount when the fuel cut is performed, the temperature difference before and after the filter in the exhaust passage when the fuel cut is performed, the execution time of the fuel cut, and a function formula that calculates the heat removal amount based on the specific heat of the air. A control device for an internal combustion engine according to claim 1.

3. The processing circuit executes the increase process when the amount of particulate matter deposited on the filter is equal to or greater than a predetermined amount. A control device for an internal combustion engine according to claim 1.

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