Internal combustion engine control device

Abstract

To suppress variations in the air-fuel ratio of the fuel-air mixture burned within each cylinder. [Solution] The control device 60 is applied to an internal combustion engine 10 that can use fuel containing ethanol. The internal combustion engine 10 is equipped with a plurality of cylinders 11, a plurality of fuel injectors 15, an intake passage 13, and a purge port 33. The purge port 33 releases purge gas containing fuel vapor generated in the fuel tank 21 into the intake passage 13. The processing circuit 61 of the control device 60 individually corrects the fuel injection amounts of the plurality of fuel injectors 15 so that the fuel injection amount of the fuel injector 15 corresponding to the cylinder with a large amount of purge gas introduced is less than the fuel injection amount of the fuel injector 15 corresponding to the cylinder with a small amount of purge gas introduced.

Description

Technical Field

[0001] The present invention relates to an internal combustion engine control device applied to an internal combustion engine capable of using fuel containing ethanol.

Background Art

[0002] Patent Document 1 discloses an internal combustion engine capable of using fuel containing alcohol and a control device applied to the internal combustion engine. The internal combustion engine includes a plurality of cylinders, a plurality of fuel injection valves corresponding to each of the plurality of cylinders, and a purge processing device that discharges purge gas containing fuel vapor generated in a fuel tank into an intake passage.

[0003] The above control device calculates a learning value for compensating for a deviation between a detected value and a target value of an air-fuel ratio caused by the purge processing device discharging purge gas into the intake passage. Then, the control device corrects the fuel injection amounts of the plurality of fuel injection valves according to the learning value.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The above purge processing device discharges purge gas into the intake passage through a purge port connected to the intake passage. The purge gas thus discharged into the intake passage is introduced into a plurality of cylinders. However, there is variation in the amount of purge gas introduced into the plurality of cylinders. Therefore, when the purge gas is discharged into the intake passage, the air-fuel ratio of the air-fuel mixture burned in the cylinders may vary from cylinder to cylinder due to the variation in the amount of purge gas introduced into the plurality of cylinders.

Means for Solving the Problems

[0006] The internal combustion engine control device for solving the above problems is applicable to an internal combustion engine that can use fuel containing ethanol and comprises a plurality of cylinders, a plurality of fuel injectors corresponding to each of the plurality of cylinders, an intake passage through which air introduced into the plurality of cylinders flows, and a purge port for releasing purge gas containing fuel vapor generated in the fuel tank into the intake passage. The internal combustion engine control device includes a processing circuit for controlling the fuel injection amount of the plurality of fuel injectors. The processing circuit performs cylinder-specific correction processing to individually correct the fuel injection amount of the plurality of fuel injectors so that the fuel injection amount of the fuel injector corresponding to the cylinder with a large amount of purge gas introduced is less than the fuel injection amount of the fuel injector corresponding to the cylinder with a small amount of purge gas introduced. [Effects of the Invention]

[0007] The above-mentioned internal combustion engine control device has the effect of suppressing variations in the air-fuel ratio of the fuel-air mixture burned in each cylinder. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 shows a schematic configuration of a control device, which is one embodiment of an internal combustion engine control device, and a schematic configuration of an internal combustion engine controlled by the control device. [Figure 2] Figure 2 is a schematic diagram showing how the purge gas released from the purge port into the intake passage moves towards the cylinder. [Figure 3] Figure 3 is a block diagram showing the multiple processes performed by the processing circuit of the control device in Figure 1. [Figure 4] Figure 4 is a flowchart showing an example of the concentration estimation process in Figure 3. [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 illustrates an internal combustion engine 10 and a control device 60 applied to the internal combustion engine 10. The control device 60 corresponds to the "internal combustion engine control device".

[0010] <Configuration of internal combustion engine 10> The internal combustion engine 10 is an internal combustion engine that can use fuel containing ethanol. This fuel, for example, contains at least ethanol from gasoline. Of course, the internal combustion engine 10 can also use fuel containing only gasoline from gasoline.

[0011] The internal combustion engine 10 comprises a plurality of cylinders 11, a crankshaft 12, an intake passage 13, a plurality of fuel injectors 15, a plurality of spark plugs 16, and an exhaust passage 17. The plurality of cylinders 11 include a first cylinder #1, a second cylinder #2, a third cylinder #3, and a fourth cylinder #4, which are arranged in order in the direction in which the crankshaft 12 extends.

[0012] The intake passage 13 is a passage through which air flows to be introduced into multiple cylinders 11. A throttle valve 14 is installed in the intake passage 13 to adjust the amount of intake air. The fuel injector 15 injects fuel into the corresponding cylinder 11. In the multiple cylinders 11, a mixture of air and fuel is burned by the spark discharge of the corresponding spark plug 16. This causes the crankshaft 12 to rotate. Also, exhaust gas is generated in the multiple cylinders 11 as the mixture burns. The exhaust gas discharged from the multiple cylinders 11 then flows through the exhaust passage 17.

[0013] The internal combustion engine 10 is equipped with a fuel supply device 20. The fuel supply device 20 supplies fuel stored in the fuel tank 21 to a plurality of fuel injection valves 15. The fuel supply device 20 includes a delivery pipe 23 and a fuel supply passage 22. The delivery pipe 23 temporarily stores the fuel to be supplied to the plurality of fuel injection valves 15. The fuel supply passage 22 is a fuel passage that supplies fuel from the fuel tank 21 to the delivery pipe 23.

[0014] The internal combustion engine 10 is equipped with a purge treatment device 30. The purge treatment device 30 is a device that releases purge gas containing fuel vapor generated in the fuel tank 21 into the intake passage 13. The purge treatment device 30 has a canister 31, a purge passage 32, a purge port 33, and a purge valve 34. The canister 31 adsorbs fuel vapor generated in the fuel tank 21. The purge passage 32 is a passage through which the purge gas containing fuel vapor adsorbed by the canister 31 flows toward the intake passage 13. The purge port 33 is connected to the end of the purge passage 32. The purge port 33 releases the purge gas flowing through the purge passage 32 to the portion of the intake passage 13 downstream of the throttle valve 14. The purge valve 34 is an electronically driven valve installed in the middle of the purge passage 32. By controlling the opening degree of the purge valve 34, the flow rate of purge gas flowing through the purge passage 32 can be adjusted.

[0015] <Sensors for internal combustion engine 10> The internal combustion engine 10 is equipped with multiple sensors that output signals to the control device 60 according to the detection results. The multiple sensors include an air flow meter 41, a water temperature sensor 42, an air-fuel ratio sensor 43, and a concentration sensor 44. The air flow meter 41 detects the flow rate of air flowing through the intake passage 13. The water temperature sensor 42 detects the temperature of the coolant circulating inside the internal combustion engine 10. The air-fuel ratio sensor 43 detects the air-fuel ratio of the mixture burned in the multiple cylinders 11. The concentration sensor 44 detects the ethanol concentration of the fuel stored in the fuel tank 21.

[0016] Hereafter, the airflow rate based on the detection signal from the air flow meter 41 will be referred to as "intake air volume GA". The coolant temperature based on the detection signal from the water temperature sensor 42 will be referred to as "coolant temperature TPw". The air-fuel ratio based on the detection signal from the air-fuel ratio sensor 43 will be referred to as "air-fuel ratio detection value AF". The ethanol concentration based on the detection signal from the concentration sensor 44 will be referred to as "ethanol concentration detection value CET".

[0017] <Control device 60> The control device 60 includes a processing circuit 61 that controls the operation of the internal combustion engine 10. An example of the processing circuit 61 is an electronic control unit. In this case, the processing circuit 61 has a CPU 62, a first memory 63, and a second memory 64. The first memory 63 stores various control programs executed by the CPU 62. The operation results of the CPU 62 are stored in the second memory 64. By the CPU 62 executing the control programs in the first memory 63, the processing circuit 61 can control the fuel injection amounts of the plurality of fuel injection valves 15, the opening degree of the throttle valve 14, and the opening degree of the purge valve 34.

[0018] <Variation in the amount of purge gas introduced into cylinder 11> Referring to FIG. 2, the variation in the amount of purge gas introduced into cylinder 11 will be described. In FIG. 2, the solid arrow Y1 indicates the flow of the ethanol component contained in the purge gas, while the dashed arrow Y2 indicates the flow of the gasoline component contained in the purge gas.

[0019] The specific gravity of ethanol is smaller than that of gasoline. Therefore, the ethanol component contained in the fuel discharged from the purge port 33 to the intake passage 13 is likely to be introduced into the cylinder located at a position away from the purge port 33 among the plurality of cylinders #1, #2, #3, #4, as shown by the arrow Y1 in FIG. 2. That is, among the plurality of cylinders #1 to #4, the amount of introduction of the ethanol component into the fourth cylinder #4 located farthest from the purge port 33 is the largest. On the other hand, among the plurality of cylinders #1 to #4, the amount of introduction of the ethanol component into the first cylinder #1 located closest to the purge port 33 is the smallest.

[0020] The gasoline component contained in the fuel discharged from the purge port 33 into the intake passage 13 is likely to be introduced into the cylinder located near the purge port 33 among the plurality of cylinders #1 to #4, as shown by the arrow Y2 in FIG. 2. That is, among the plurality of cylinders #1 to #4, the introduction amount of the gasoline component into the first cylinder #1 located closest to the purge port 33 is the largest. On the other hand, among the plurality of cylinders #1 to #4, the introduction amount of the gasoline component into the fourth cylinder #4 located farthest from the purge port 33 is the smallest.

[0021] Therefore, the introduction amount of the purge gas into the cylinders varies for each of the cylinders #1 to #4. Also, when the ethanol concentration of the purge gas discharged from the purge port 33 into the intake passage 13 changes, the introduction amount of the purge gas into the plurality of cylinders #1 to #4 changes. The ethanol concentration of the purge gas discharged from the purge port 33 into the intake passage 13 is described as "ethanol concentration CEtR". For example, when the ethanol concentration CEtR increases, the introduction amount of the purge gas into the cylinders located away from the purge port 33 among the plurality of cylinders #1 to #4 tends to increase, while the introduction amount of the purge gas into the cylinders located near the purge port 33 tends to decrease. Conversely, when the ethanol concentration CEtR decreases, the introduction amount of the purge gas into the cylinders located near the purge port 33 among the plurality of cylinders #1 to #4 tends to increase, while the introduction amount of the purge gas into the cylinders located away from the purge port 33 tends to decrease.

[0022] When the introduction amount of the purge gas into the plurality of cylinders #1 to #4 varies in this way, the air-fuel ratio of the air-fuel mixture burned in the plurality of cylinders #1 to #4 varies. <Various processes executed by the processing circuit 61> Referring to FIG. 3, various processes executed by the processing circuit 61 to adjust the fuel injection amounts of the plurality of fuel injection valves 15 so as to suppress the variation in the air-fuel ratio of the air-fuel mixture burned in the plurality of cylinders #1 to #4 will be described.

[0023] The processing circuit 61 performs the following: reference injection amount calculation process M11, air-fuel ratio feedback process M12, common correction process M13, concentration estimation process M14, injection amount estimation process M15, cylinder-specific correction process M16, and injection process M17. Hereafter, the air-fuel ratio feedback process M12 will be referred to as "air-fuel ratio F / B process M12".

[0024] The reference injection amount calculation process M11 is a process for calculating the base injection amount QfB, which is the base value of the fuel injection amount of the fuel injection valve 15. In the reference injection amount calculation process M11, the processing circuit 61 calculates the base injection amount QfB based on the required torque TqR, which is the required value of the output torque of the internal combustion engine 10. For example, the processing circuit 61 calculates the base injection amount QfB such that the value increases as the required torque TqR increases.

[0025] The air-fuel ratio F / B processing M12 is a process that calculates the corrected injection amount ΔQf, which is the amount of fuel injection correction to correct the discrepancy between the target air-fuel ratio AFTr, which is the target value of the air-fuel ratio, and the detected air-fuel ratio AF. In the air-fuel ratio F / B processing M12, the processing circuit 61 calculates the corrected injection amount ΔQf by feedback control that takes the deviation between the target air-fuel ratio AFTr and the detected air-fuel ratio AF as input.

[0026] The common correction process M13 is a process that calculates the target injection amount QfTr, which is the target value of the fuel injection amount, by correcting the base injection amount QfB with the corrected injection amount ΔQf. In the common correction process M13, the processing circuit 61 calculates the target injection amount QfTr as the sum of the base injection amount QfB and the corrected injection amount ΔQf.

[0027] The concentration estimation process M14 is a process that estimates the ethanol concentration CEtR of the purge gas released from the purge port 33 into the intake passage 13. Hereafter, the ethanol concentration estimated by the concentration estimation process M14 will be referred to as the "estimated concentration value CEtRe". The specific details of the concentration estimation process M14 will be described later.

[0028] The injection amount estimation process M15 is a process that estimates the amount of purge gas to be introduced into multiple cylinders #1 to #4. Hereafter, the estimated amount of purge gas introduced into cylinder #n will be referred to as "Estimated Injection Amount Qpge(n)". "n" is replaced with the cylinder number. Therefore, the estimated injection amount Qpge for cylinder #1 will be referred to as "Estimated Injection Amount Qpge(1)".

[0029] In the intake amount estimation process M15, the processing circuit 61 calculates the intake amount estimation values ​​Qpge(1), Qpge(2), Qpge(3), and Qpge(4) for multiple cylinders #1 to #4 based on the concentration estimation value CEtRe calculated in the concentration estimation process M14 and the opening degree of the purge valve 34.

[0030] An example of the introduction amount estimation process M15 is described below. The processing circuit 61 calculates the estimated discharge amount RLpg, which is an estimated value of the amount of purge gas discharged from the purge port 33 to the intake passage 13, based on the opening degree Vpg of the purge valve 34. For example, the processing circuit 61 calculates the estimated discharge amount RLpg such that the value increases as the opening degree Vpg increases.

[0031] The processing circuit 61 then calculates multiple estimated intake values ​​Qpge(1) to Qpge(4) by allocating the estimated discharge amount RLpg to multiple cylinders #1 to #4 based on the estimated concentration value CEtRe. For example, when the estimated concentration value CEtRe is relatively high, the processing circuit 61 calculates multiple estimated intake values ​​Qpge(1) to Qpge(4) such that the allocation of estimated discharge amount RLpg to cylinders farther away from the purge port 33 is large, and the allocation of estimated discharge amount RLpg to cylinders closer to the purge port 33 is small. On the other hand, when the estimated concentration value CEtRe is relatively low, the processing circuit 61 calculates multiple estimated intake values ​​Qpge(1) to Qpge(4) such that the allocation of estimated discharge amount RLpg to cylinders farther away from the purge port 33 is small, and the allocation of estimated discharge amount RLpg to cylinders closer to the purge port 33 is large.

[0032] As a result, when the concentration estimate CEtRe is high, the processing circuit 61 can increase the estimated intake amount Qpge(4) for cylinder #4, which is the furthest from the purge port 33 among the multiple cylinders #1 to #4, compared to when the concentration estimate CEtRe is low. Also, the processing circuit 61 can decrease the estimated intake amount Qpge(1) for cylinder #1, which is the closest to the purge port 33.

[0033] The cylinder-specific correction process M16 individually corrects the target injection amounts of multiple fuel injectors 15 so that the fuel injection amount of the fuel injector 15 corresponding to the cylinder with a large estimated intake amount Qpge among multiple cylinders #1 to #4 is less than the fuel injection amount of the fuel injector 15 corresponding to the cylinder with a small estimated intake amount Qpge.

[0034] In the cylinder-specific correction process M16, the processing circuit 61 calculates the reduction correction amount dQf(n) for each cylinder #1 to #4. The cylinder number is substituted for "n". Therefore, the reduction correction amount dQf for the fuel injection amount of the fuel injector 15 corresponding to cylinder #1 is written as "reduction correction amount dQf(1)". Furthermore, hereafter, the reduction correction amount dQf(n) for the fuel injector 15 corresponding to cylinder #n will be written as "reduction correction amount dQf(n) for cylinder #n".

[0035] An example of a method for calculating the reduction correction amount dQf(1) for cylinder #1 is described below. The processing circuit 61 calculates the reduction correction amount dQf(1) based on the estimated intake amount Qpge(1) for cylinder #1. For example, the processing circuit 61 calculates the reduction correction amount dQf(1) such that the value increases as the estimated intake amount Qpge(1) increases.

[0036] The calculation method for the reduction correction amounts dQf(2), dQf(3), and dQf(4) of cylinders #2, #3, and #4 (excluding cylinder #1) is the same as the calculation method for the reduction correction amount dQf(1). Therefore, the explanation of the calculation methods for reduction correction amounts dQf(2) to dQf(4) will be omitted.

[0037] Then, the processing circuit 61 sets the value obtained by subtracting the reduction correction amount dQf(1) from the target injection amount QfTr as the target injection amount QfTr for the fuel injector 15 corresponding to cylinder #1. The processing circuit 61 sets the value obtained by subtracting the reduction correction amount dQf(2) from the target injection amount QfTr as the target injection amount QfTr for the fuel injector 15 corresponding to cylinder #2 as the target injection amount QfTr(2). The processing circuit 61 sets the value obtained by subtracting the reduction correction amount dQf(3) from the target injection amount QfTr as the target injection amount QfTr for the fuel injector 15 corresponding to cylinder #3 as the target injection amount QfTr(3). The processing circuit 61 sets the value obtained by subtracting the reduction correction amount dQf(4) from the target injection amount QfTr as the target injection amount QfTr for the fuel injector 15 corresponding to cylinder #4 as the target injection amount QfTr(4).

[0038] Injection process M17 is a process that controls the injection of fuel from multiple fuel injectors 15 by adjusting the energization supplied to multiple fuel injectors 15. In injection process M17, the processing circuit 61 operates the fuel injector 15 corresponding to cylinder #1 based on the target injection amount QfTr(1). The processing circuit 61 operates the fuel injector 15 corresponding to cylinder #2 based on the target injection amount QfTr(2). The processing circuit 61 operates the fuel injector 15 corresponding to cylinder #3 based on the target injection amount QfTr(3). The processing circuit 61 operates the fuel injector 15 corresponding to cylinder #4 based on the target injection amount QfTr(4).

[0039] <Concentration estimation process M14> Referring to Figure 4, an example of a series of processes showing the concentration estimation process M14 will be explained. The processing circuit 61 repeatedly executes the concentration estimation process M14 at predetermined control cycles.

[0040] In step S11, the processing circuit 61 obtains an ethanol concentration detection value CEt, which is the detected value of the ethanol concentration of the fuel stored in the fuel tank 21. In the following step S13, the processing circuit 61 calculates a concentration estimate value CEtRe, which is the estimated value of the ethanol concentration CEtR of the purge gas released from the purge port 33 into the intake passage 13. For example, the processing circuit 61 calculates the concentration estimate value CEtRe from the ethanol concentration detection value CEt obtained in step S11. Then, the processing circuit 61 proceeds to step S15.

[0041] Here, the volatility of gasoline does not depend much on temperature. On the other hand, the volatility of ethanol does change with temperature. When the temperature of ethanol exceeds a specified temperature, the amount of ethanol that volatilizes increases sharply compared to when the temperature of ethanol is below the specified temperature. In other words, even if the ethanol concentration of the fuel stored in the fuel tank 21 is the same, the ethanol concentration CEtR of the purge gas released from the purge port 33 to the intake passage 13 may change depending on whether the temperature of the fuel is higher than the specified temperature.

[0042] Therefore, in step S15, the processing circuit 61 obtains the fuel temperature TPf, which is the temperature of the fuel stored in the fuel tank 21. For example, the processing circuit 61 obtains an estimated value of the fuel temperature based on the water temperature TPw as the fuel temperature TPf. In this case, the processing circuit 61 may calculate the estimated value of the fuel temperature such that the value increases as the water temperature TPw increases. Alternatively, the processing circuit 61 may obtain an estimated value of the fuel temperature based on the temperature of the oil circulating in the internal combustion engine 10 as the fuel temperature TPf. Furthermore, if a sensor for detecting the temperature inside the fuel tank 21 is provided, the processing circuit 61 may obtain the value detected by the sensor as the fuel temperature TPf.

[0043] In the following step S17, the processing circuit 61 determines whether the fuel temperature TPf obtained in step S15 is equal to or greater than a predetermined temperature TPfth. The predetermined temperature TPfth is a criterion for determining whether or not ethanol is at a temperature at which it is easily volatile. For example, the predetermined temperature TPfth is set to the specified temperature mentioned above, or a temperature corresponding to that specified temperature. If the fuel temperature TPf is equal to or greater than the predetermined temperature TPfth (S17: YES), the processing circuit 61 proceeds to step S19. If the fuel temperature TPf is less than the predetermined temperature TPfth (S17: NO), the processing circuit 61 terminates the concentration estimation process M14 without executing the process in step S19.

[0044] In step S19, the processing circuit 61 increases the concentration estimate CEtRe obtained in step S13. For example, the processing circuit 61 calculates the product of the concentration estimate CEtRe obtained in step S13 and the correction gain Gn as the corrected concentration estimate CEtRe. The correction gain Gn is a value greater than 1. That is, when the fuel temperature TPf is above a predetermined temperature TPfth, the processing circuit 61 can make the concentration estimate CEtRe larger compared to when the fuel temperature TPf is below the predetermined temperature TPfth. Then, the processing circuit 61 terminates the concentration estimation process M14.

[0045] <Operation and Effects of This Embodiment> (1) When purge gas is released from the purge port 33 into the intake passage 13 during the operation of the internal combustion engine 10, the processing circuit 61 individually corrects the fuel injection amounts of multiple fuel injectors 15 corresponding to multiple cylinders #1 to #4 by executing cylinder-specific correction processing M16. Specifically, the processing circuit 61 sets target injection amounts QfTr(1) to QfTr(4) such that the fuel injection amount of the fuel injector 15 corresponding to the cylinder with a large amount of purge gas introduced is less than the fuel injection amount of the fuel injector 15 corresponding to the cylinder with a small amount of purge gas introduced. Then, the processing circuit 61 operates the multiple fuel injectors 15 based on the target injection amounts QfTr(1) to QfTr(4).

[0046] As a result, the control device 60 can suppress variations in the sum of the fuel injection amount from the fuel injection valve 15 and the amount of purge gas introduced for each cylinder #1 to #4. Therefore, the control device 60 can suppress variations in the air-fuel ratio of the fuel mixture burned in each cylinder #1 to #4.

[0047] (2) The ethanol component of the purge gas released from the purge port 33 into the intake passage 13 is more likely to be directed to the cylinders #1 to #4 that are located further away from the purge port 33. The gasoline component of the purge gas is more likely to be directed to the cylinders #1 to #4 that are located closer to the purge port 33.

[0048] Therefore, the processing circuit 61 calculates the estimated concentration value CEtRe, which is an estimated value of the ethanol concentration of the purge gas released from the purge port 33 into the intake passage 13, by executing the concentration estimation process M14. Then, in the introduction amount estimation process M15, the processing circuit 61 estimates that if the estimated concentration value CEtRe is large, compared to when the estimated concentration value CEtRe is small, the amount of purge gas introduced into cylinder #4, which is the furthest from the purge port 33 among the multiple cylinders #1 to #4, is large, and the amount of purge gas introduced into cylinder #1, which is the closest to the purge port 33, is small.

[0049] The processing circuit 61 sets target injection amounts QfTr(1) to QfTr(4) based on the results of the injection amount estimation process M15. Then, the processing circuit 61 operates the multiple fuel injectors 15 based on these target injection amounts QfTr(1) to QfTr(4). This allows the processing circuit 61 to individually adjust the fuel injection amounts of the multiple fuel injectors 15, taking into account the amount of purge gas introduced into multiple cylinders #1 to #4.

[0050] (3) The processing circuit 61 calculates the concentration estimate CEtRe based on whether the fuel temperature TPf, which is the temperature of the fuel stored in the fuel tank 21, is equal to or greater than a predetermined temperature TPfth. In other words, the processing circuit 61 can calculate the concentration estimate CEtRe by taking into account the volatility of ethanol. Therefore, the processing circuit 61 can accurately estimate the ethanol concentration of the purge gas released from the purge port 33 into the intake passage 13.

[0051] <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.

[0052] Even if the amount of purge gas introduced into multiple cylinders #1 to #4 is roughly the same, variations in the air-fuel ratio of the mixture burned in multiple cylinders #1 to #4 may occur. The combustion characteristics of ethanol are different from those of gasoline. Therefore, variations in the ethanol concentration in the purge gas introduced into multiple cylinders #1 to #4 may cause variations in the air-fuel ratio of the mixture burned in multiple cylinders #1 to #4.

[0053] Therefore, the processing circuit 61 estimates the ethanol concentration of the purge gas introduced into the cylinder from the intake passage 13 for each cylinder #1 to #4. The processing circuit 61 may then individually correct the fuel injection amounts of multiple fuel injectors 15 so that when the ethanol concentration of the purge gas introduced into the cylinder from the intake passage 13 is high, the fuel injection amount of the fuel injector 15 corresponding to that cylinder is higher compared to when the ethanol concentration is low. This allows the processing circuit 61 to more effectively suppress variations in the air-fuel ratio of the fuel mixture burned in each cylinder #1 to #4.

[0054] When the ethanol concentration of the fuel supplied to the multiple fuel injectors 15 by the fuel supply device 20 changes, the air-fuel ratio detection value AF changes. Therefore, the processing circuit 61 may estimate the ethanol concentration stored in the fuel tank 21 based on the air-fuel ratio detection value AF.

[0055] The processing circuit 61 may calculate the concentration estimate CEtRe without considering whether the fuel temperature TPf, which is the temperature of the fuel stored in the fuel tank 21, is equal to or greater than a predetermined temperature TPfth. In this case, the concentration estimation process may omit the processes in steps S15, S17, and S19 in Figure 4.

[0056] The internal combustion engine to which the control device 60 is applied may have a configuration different from the internal combustion engine 10 shown in Figure 1, as long as it has two or more cylinders arranged in the direction in which the crankshaft 12 extends. For example, the internal combustion engine may have three cylinders arranged in the direction in which the crankshaft 12 extends.

[0057] The processing circuit 61 is not limited to one that includes a CPU and ROM and performs software processing. In other words, the control device 60 may have any of the following configurations: (a), (b), and (c).

[0058] (a) The processing circuit 61 includes one or more processors that perform various processes according to a computer program. The processor includes a CPU and memory such as RAM and ROM. The memory stores program code or instructions configured to cause the CPU to perform the processes. The memory, i.e., computer-readable media, includes any available media that can be accessed by a general-purpose or dedicated computer.

[0059] (b) The processing circuit 61 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."

[0060] (c) The processing circuit 61 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.

[0061] 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]

[0062] 10...Internal combustion engine, 11, #1~#4...Cylinders, 13...Intake passage, 15...Fuel injector, 21...Fuel tank, 33...Purge port, 60...Control device, 61...Processing circuit.

Claims

1. This invention relates to an internal combustion engine capable of using fuel containing ethanol, and comprising: a plurality of cylinders; a plurality of fuel injectors corresponding to each of the plurality of cylinders; an intake passage through which air is introduced into the plurality of cylinders; and a purge port for releasing purge gas containing fuel vapor generated in the fuel tank into the intake passage. The system includes a processing circuit that controls the fuel injection amount of the plurality of fuel injectors, The processing circuit performs cylinder-specific correction processing to individually adjust the fuel injection amounts of the multiple fuel injectors so that the fuel injection amount of the fuel injector corresponding to the cylinder with a large amount of purge gas introduced is less than the fuel injection amount of the fuel injector corresponding to the cylinder with a small amount of purge gas introduced. Internal combustion engine control device.

2. The aforementioned processing circuit is A concentration estimation process for estimating the ethanol concentration of the purge gas released from the purge port into the intake passage, If the ethanol concentration of the purge gas is high, the amount of purge gas introduced into the cylinder furthest from the purge port is estimated to be higher than when the ethanol concentration is low, and the amount of purge gas introduced into the cylinder closest to the purge port is estimated to be lower. This process is performed to estimate the amount of purge gas introduced into the cylinder furthest from the purge port. The internal combustion engine control device according to claim 1.

3. The processing circuit, in the concentration estimation process, Determine whether the temperature of the fuel stored in the fuel tank is above a predetermined temperature. If it is determined that the temperature of the fuel stored in the fuel tank is above the predetermined temperature, it is inferred that the ethanol concentration of the purge gas is higher compared to when it is determined that the temperature is below the predetermined temperature. The internal combustion engine control device according to claim 2.

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