Internal combustion engine control device

Abstract

To suppress the deterioration of fuel efficiency in internal combustion engines by performing filter regeneration processing at the appropriate time. [Solution] The internal combustion engine 10 is equipped with a filter 19 that collects PM contained in the exhaust gas flowing through the exhaust passage 16. The CPU 41 of the control device 40 performs a calculation process to calculate the amount of PM accumulated in the filter 19, which is the amount of PM collected in the filter 19, based on the operating conditions of the internal combustion engine 10 and the alcohol content of the fuel supplied to the cylinder 11, and a regeneration process to burn the PM collected in the filter 19 when the amount of PM accumulated exceeds a specified amount.

Description

Technical Field

[0001] The present invention relates to an internal combustion engine control device applied to an internal combustion engine in which a filter is installed in an exhaust passage.

Background Art

[0002] Patent Document 1 discloses a control device applied to an internal combustion engine in which a filter is installed in an exhaust passage. The control device executes a calculation process for calculating a PM deposition amount, which is the amount of particulate matter collected by the filter, and a regeneration process for burning the particulate matter collected by the filter when the PM deposition amount exceeds a specified amount.

[0003] In the above calculation process, the control device calculates the PM deposition amount based on operating conditions including the intake air amount and fuel injection amount of the internal combustion engine.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] When using a fuel containing alcohol as the fuel of the internal combustion engine, the amount of particulate matter generated in the internal combustion engine varies depending on the alcohol content in the fuel. Therefore, when the above control device is applied to an internal combustion engine using a fuel containing alcohol, there is a risk of deterioration in the fuel consumption of the internal combustion engine due to the control device being unable to execute the regeneration process of the filter at an appropriate time. [[ID=4,0]]

Means for Solving the Problems

[0006] An internal combustion engine control device for solving the above problems is applied to an internal combustion engine comprising a cylinder, an exhaust passage through which exhaust gas discharged from the cylinder flows, and a filter for collecting particulate matter contained in the exhaust gas flowing through the exhaust passage. The internal combustion engine control device includes a processing circuit. The processing circuit performs a calculation process to calculate the PM accumulation amount, which is the amount of particulate matter collected by the filter, based on the operating conditions of the internal combustion engine and the alcohol content of the fuel supplied to the cylinder, and a regeneration process to burn the particulate matter collected by the filter when the PM accumulation amount exceeds a specified amount. [Effects of the Invention]

[0007] The above-mentioned internal combustion engine control device has the effect of suppressing the deterioration of fuel efficiency of the internal combustion engine by performing filter regeneration processing at the appropriate time. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a schematic diagram showing a control device, which is one embodiment of an internal combustion engine control device, and an internal combustion engine to which the control device is applied. [Figure 2] Figure 2 is a block diagram showing the calculation process performed by the control device in Figure 1. [Figure 3] Figure 3 is a flowchart showing the process for calculating the amount of production shown in Figure 2. [Figure 4] Figure 4 is a flowchart showing the series of processes that occur when the regeneration process is executed in the control device shown in Figure 1. [Modes for carrying out the invention]

[0009] One embodiment of an internal combustion engine control device will be described with reference to Figures 1 to 4. Figure 1 shows a control device 40, which is an example of an internal combustion engine control device, and an internal combustion engine 10 to which the control device 40 is applied. The internal combustion engine 10 is mounted on a vehicle.

[0010] <Configuration of an internal combustion engine> The internal combustion engine 10 is an internal combustion engine capable of operating using alcohol-containing fuel. The internal combustion engine 10 comprises a plurality of cylinders 11, a crankshaft 12, an intake passage 13, a plurality of fuel injectors 14, a plurality of spark plugs 15, and an exhaust passage 16. The intake passage 13 is a passage through which air flows to be introduced into the plurality of cylinders 11. A throttle valve 17 that operates to adjust the amount of intake air is installed in the intake passage 13. The fuel injectors 14 inject fuel to be supplied to the corresponding cylinders 11. In the plurality of cylinders 11, a mixture of air and fuel is burned by the spark discharge of the corresponding spark plugs 15. This causes the crankshaft 12 to rotate. Also, exhaust gas is generated in the plurality of cylinders 11 as the mixture is burned. The exhaust gas discharged from the plurality of cylinders 11 flows through the exhaust passage 16.

[0011] The internal combustion engine 10 is equipped with a three-way catalytic converter 18 and a filter 19 installed in the exhaust passage 16. The three-way catalytic converter 18 is located upstream of the filter 19 in the exhaust passage 16. The three-way catalytic converter 18 purifies the exhaust gas flowing through the exhaust passage 16. Specifically, the three-way catalytic converter 18 purifies hydrocarbons, carbon monoxide, and nitrogen oxides in the exhaust gas. The filter 19 collects particulate matter contained in the exhaust gas flowing through the exhaust passage 16. Hereafter, particulate matter will be referred to as "PM". "PM" is an abbreviation for "Particulate Matter".

[0012] <Sensor> The control device 40 receives detection signals from multiple sensors. These multiple sensors include a crank angle sensor 31, an air flow meter 32, an air-fuel ratio sensor 33, an exhaust temperature sensor 34, and an alcohol concentration sensor 35.

[0013] The crank angle sensor 31 detects the rotation angle of the crankshaft 12. The rotational speed of the crankshaft 12 based on the detection signal from the crank angle sensor 31 is referred to as "engine rotational speed NE". The airflow meter 32 detects the airflow rate in the intake passage 13. The airflow rate based on the detection signal from the airflow meter 32 is referred to as "intake air volume GA".

[0014] The air-fuel ratio sensor 33 is disposed at a portion upstream of the three-way catalyst 18 in the exhaust passage 16. The air-fuel ratio sensor 33 detects the oxygen concentration of the exhaust flowing through the exhaust passage 16. That is, the air-fuel ratio sensor 33 can detect the air-fuel ratio of the air-fuel mixture. The air-fuel ratio of the exhaust based on the detection signal of the air-fuel ratio sensor 33 is referred to as "air-fuel ratio AF".

[0015] The exhaust temperature sensor 34 is disposed at a portion between the three-way catalyst 18 and the filter 19 in the exhaust passage 16. The exhaust temperature sensor 34 detects the temperature of the exhaust flowing into the filter 19. The temperature of the exhaust based on the detection signal of the exhaust temperature sensor 34 is referred to as "exhaust temperature TO".

[0016] The alcohol concentration sensor 35 detects the alcohol content in the fuel supplied to the plurality of cylinders 11. The alcohol content based on the detection result of the alcohol concentration sensor 35 is referred to as "alcohol content Ra".

[0017] <Control device> An example of the control device 40 is an electronic control unit. In this case, the control device 40 includes a CPU 41, a first memory 42, and a second memory 43. The first memory 42 stores a control program executed by the CPU 41. The calculation result of the CPU 41 is stored in the second memory 43. In the present embodiment, the CPU 41 corresponds to the "processing circuit". By the CPU 41 executing the control program of the first memory 42, the CPU 41 can control the operation of the internal combustion engine 10.

[0018] The CPU 41 executes a calculation process for calculating the PM deposition amount Qdp, which is the amount of PM collected by the filter 19, and a regeneration process for burning the PM collected by the filter 19 when the PM deposition amount Qdp exceeds a specified amount Th.

[0019] <Calculation process> Referring to FIGS. 2 and 3, an example of the calculation process will be described in detail. The calculation process M10 is a process of calculating the PM deposition amount Qdp based on the operating conditions of the internal combustion engine 10 and the alcohol content Ra. The calculation process M10 includes a generation amount calculation process M11, a regeneration amount calculation process M13, a difference calculation process M15, and an integration process M17.

[0020] The CPU 41 repeatedly executes the generation amount calculation process M11 at every predetermined calculation cycle. In the generation amount calculation process M11, the CPU 41 calculates the PM generation amount Qgn, which is the sum of the amounts of PM generated in the plurality of cylinders 11 within a unit time. The "unit time" referred to here is the length of the time of the calculation cycle.

[0021] As shown in FIG. 3, in the generation amount calculation process M11, the CPU 41 calculates a PM generation amount reference value QgnB, which is a PM generation amount based on the operating conditions of the internal combustion engine 10 (S11). The PM generation amount reference value QgnB is a PM generation amount on the premise that the fuel injected by the plurality of fuel injection valves 14 does not contain alcohol. The CPU derives the PM generation amount reference value QgnB based on the intake air amount GA, the fuel injection amount Qf, and the like.

[0022] Subsequently, the CPU 41 calculates the PM generation amount Qgn by correcting the PM generation amount reference value QgnB based on the alcohol content Ra (S13). For example, the CPU 41 calculates the product of the PM generation amount reference value QgnB and a correction coefficient α corresponding to the alcohol content Ra as the PM generation amount Qgn.

[0023] The correction coefficient α is a value that is 0 (zero) or more and 1 or less. The higher the alcohol content Ra, the less likely PM is to be generated. Therefore, the CPU 41 sets the correction coefficient α so that the value becomes smaller as the alcohol content Ra increases. Thereby, the CPU 41 can reduce the PM generation amount Qgn as the alcohol content Ra increases.

[0024] Returning to Figure 2, the CPU 41 repeatedly executes the regeneration amount calculation process M13 at each of the above calculation cycles. In the regeneration amount calculation process, the CPU 41 calculates the PM regeneration amount Qrp, which is the amount of PM burned by the filter 19 within a unit time.

[0025] The higher the temperature of the exhaust gas flowing into filter 19, the higher the temperature of filter 19. The higher the temperature of filter 19, the greater the amount of PM that burns in filter 19. Also, the greater the amount of oxygen flowing into filter 19, the greater the amount of PM that burns in filter 19.

[0026] Therefore, in the regeneration amount calculation process M13, the CPU 41 derives the PM generation amount based on the temperature of the filter 19 and the amount of oxygen in the exhaust gas flowing into the filter 19. For example, the CPU 41 can estimate the temperature of the filter 19 based on the exhaust gas temperature TO, the flow rate of the exhaust gas flowing into the filter 19, and the ambient temperature. The CPU 41 can also estimate the amount of oxygen in the exhaust gas flowing into the filter 19 based on the air-fuel ratio AF, the intake air volume GA, and the fuel injection volume Qf.

[0027] CPU41 repeatedly executes the difference calculation process M15 at each of the above calculation cycles. In the difference calculation process M15, CPU41 calculates the difference ΔQ by subtracting the PM regeneration amount Qrp from the PM generation amount Qgn.

[0028] The CPU 41 executes the integration process M17 each time the difference ΔQ is calculated by the difference calculation process M15. In the integration process M17, the CPU 41 calculates the sum of the previous value of PM deposition amount Qdp and the difference ΔQ as the latest value of PM deposition amount Qdp. In other words, the CPU 41 calculates the integrated value of the difference ΔQ as the PM deposition amount Qdp.

[0029] <Playback process> Referring to Figure 4, the timing and content of the playback process will be explained. The CPU 41 repeatedly executes the series of processes shown in Figure 4.

[0030] In step S21, the CPU 41 determines whether the PM accumulation amount Qdp calculated in calculation process M10 is greater than a specified amount Th. The specified amount Th is the criterion for determining whether or not regeneration of the filter 19 is necessary. If the PM accumulation amount Qdp is greater than the specified amount Th (S21: YES), the CPU 41 proceeds to step S23. On the other hand, if the PM accumulation amount Qdp is less than or equal to the specified amount Th (S21: NO), the CPU 41 terminates the series of processes shown in Figure 4.

[0031] In step S23, the CPU 41 determines whether the conditions for executing the regeneration process are met. As will be explained in more detail later, the regeneration process stops the combustion of the air-fuel mixture in the cylinder 11. Therefore, if it is possible to rotate the crankshaft 12 by external power to the internal combustion engine 10, the execution conditions can be considered to be met. For example, when a vehicle is coasting, the crankshaft 12 rotates due to power transmission from the wheels. Also, for example, if the vehicle is a hybrid vehicle in which an electric motor is connected to the crankshaft 12, the crankshaft 12 can rotate due to the drive of the electric motor.

[0032] In step S23, if the CPU 41 determines that the execution condition is met (S23:YES), the CPU 41 proceeds to step S25. On the other hand, if the CPU 41 determines that the execution condition is not met (S23:NO), the CPU 41 terminates the series of processes shown in Figure 4.

[0033] In step S25, the CPU 41 performs a regeneration process. In the regeneration process, the CPU 41 stops the spark discharge of the spark plug 15 and causes the fuel injector 14 to inject fuel, thereby raising the temperature of the filter 19 to above the ignition point of PM.

[0034] When the spark discharge from the spark plug 15 stops, unburned fuel injected from the fuel injector 14 flows out of the cylinder 11 into the exhaust passage 16. This unburned fuel is supplied to the three-way catalytic converter 18 along with air. As a result, the unburned fuel burns in the three-way catalytic converter 18, causing its temperature to rise. At this time, because the crankshaft 12 is rotating, the heat from the three-way catalytic converter 18 is transferred to the filter 19 by the gas flow that passes through the three-way catalytic converter 18 towards the filter 19. As a result, when the temperature of the filter 19 rises above the ignition point of PM, the PM burns in the filter 19.

[0035] When the CPU 41 has elapsed a predetermined time for the playback process to complete, it terminates the playback process. Then, the CPU 41 temporarily terminates the series of processes shown in Figure 4. When CPU41 performs the regeneration process in this manner, for example, CPU41 resets the PM accumulation amount Qdp to a predetermined value. One example of a predetermined value is 0 (zero).

[0036] <Operation and Effects of This Embodiment> (1) The rate at which the amount of PM adhering to the filter 19 increases depends on the alcohol content Ra of the fuel supplied to the cylinder 11.

[0037] Therefore, the CPU 41 calculates the PM accumulation amount Qdp by considering the alcohol content Ra in addition to the operating conditions of the internal combustion engine 10. As a result, even when the internal combustion engine 10 is operated using fuel containing alcohol, the CPU 41 can accurately estimate the amount of PM accumulated in the filter 19.

[0038] The CPU 41 performs regeneration processing when the PM accumulation amount Qdp calculated as described above exceeds a specified amount Th. Therefore, the CPU 41 can suppress the deterioration of the fuel efficiency of the internal combustion engine 10 by performing regeneration processing at the appropriate time.

[0039] (2) The CPU 41 calculates the PM accumulation amount Qdp by integrating the difference ΔQ between the PM generation amount Qgn and the PM regeneration amount Qrp. Here, the amount of PM generated in cylinder 11 varies depending on the alcohol content Ra of the fuel, while the combustion rate of PM in filter 19 is not significantly affected by the alcohol content Ra.

[0040] Therefore, the CPU 41 calculates the PM generation amount Qgn by correcting the PM generation amount standard value QgnB, which is calculated based on the operating conditions of the internal combustion engine 10, based on the alcohol content Ra. Then, the CPU 41 calculates the PM accumulation amount Qdp by integrating the difference ΔQ between this PM generation amount Qgn and the PM regeneration amount Qrp. Thus, the CPU 41 can accurately estimate the amount of PM accumulated in the filter 19.

[0041] (Example of change) 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.

[0042] The CPU 41 may calculate the PM generation amount Qgn without considering the alcohol content Ra, provided that the operating conditions of the internal combustion engine 10 are taken into account. In this case, the CPU 41 may correct the difference ΔQ between the PM generation amount Qgn and the PM regeneration amount Qrp based on the alcohol content Ra. In this case, the CPU 41 calculates the PM accumulation amount Qdp by integrating the corrected difference ΔQ.

[0043] The regeneration process may be different from the process described in the above embodiment, as long as it can raise the temperature of the filter 19. For example, the regeneration process may include at least one of the following: dithering control for each cylinder 11, fuel cut control for some of the cylinders 11 of the plurality of 11, and control to retard the ignition timing.

[0044] The CPU41 may also estimate the alcohol content using the air-fuel ratio AF or the like. In this case, the CPU41 may use the estimated alcohol content to calculate the PM deposit amount Qdp.

[0045] The internal combustion engine to which the control device 40 is applied only needs to have one or more cylinders 11. The control device 40 is not limited to one that includes a CPU and ROM and performs software processing. In other words, the control device 40 may have any of the following configurations: (a), (b), and (c).

[0046] (a) The control device 40 comprises one or more processors that perform various processes according to a computer program. The processors include a CPU and memory such as RAM and ROM. The memory stores program code or instructions configured to cause the CPU to perform processes. The memory, i.e., computer-readable media, includes any available media that can be accessed by a general-purpose or dedicated computer.

[0047] (b) The control device 40 includes one or more dedicated hardware circuits that perform various processes. Examples of dedicated hardware circuits include application-specific integrated circuits, i.e., ASICs or FPGAs. ASIC is an abbreviation for "Application Specific Integrated Circuit," and FPGA is an abbreviation for "Field Programmable Gate Array."

[0048] (c) The control device 40 comprises one or more processors that execute a portion of the various processes according to a computer program, and one or more dedicated hardware circuits that execute the remaining processes of the various processes.

[0049] In this specification, the expression "at least one" means "one or more" of the desired options. For example, if there are two options, the expression "at least one" means "only one option" or "both of the two options." As another example, if there are three or more options, the expression "at least one" means "only one option" or "a combination of two or more arbitrary options." [Explanation of Symbols]

[0050] 10...Internal combustion engine, 11...Cylinder, 16...Exhaust passage, 18...Three-way catalytic converter, 19...Filter, 40...Control device, 41...CPU.

Claims

1. This invention is applied to an internal combustion engine comprising a cylinder, an exhaust passage through which exhaust gas discharged from the cylinder flows, and a filter for collecting particulate matter contained in the exhaust gas flowing through the exhaust passage. Equipped with a processing circuit, The aforementioned processing circuit is A calculation process for calculating the PM deposit amount, which is the amount of particulate matter collected by the filter, based on the operating conditions of the internal combustion engine and the alcohol content of the fuel supplied to the cylinder, If the amount of PM accumulation exceeds a specified amount, a regeneration process is performed in which the particulate matter collected in the filter is burned. Internal combustion engine control device.

2. The processing circuit, in the calculation process, Based on the operating conditions of the internal combustion engine and the alcohol content of the fuel, the difference between the amount of particulate matter generated in the cylinder (PM generation amount) and the amount of particulate matter burned in the filter (PM regeneration amount) is calculated at predetermined calculation cycles. The cumulative value of the difference is calculated as the PM accumulation amount. The processing circuit calculates the PM generation amount such that the value decreases as the alcohol content in the fuel increases. The internal combustion engine control device according to claim 1.

Images