Controller of internal combustion engine

Abstract

To stabilize noise generated in exhaust sound control.SOLUTION: A controller 100 executes exhaust sound control when an accelerator is shifted from ON to OFF. As the exhaust sound control, the control device 100 alternates between combustion of an air-fuel mixture by performing ignition and combustion stop of the air-fuel mixture by stopping ignition in a combustion cycle.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] For example, the internal combustion engine described in Patent Document 1 executes exhaust sound control to ensure a good sporty sound. The exhaust sound control described in the document is a control that significantly retards the ignition timing to after the top dead center of compression when the accelerator is switched from on to off so that the mixture continues to burn until the exhaust valve starts to open. If a semi-misfire state is created by significantly retarding the ignition timing in this way, the unburned gas will burn in the exhaust passage, generating an explosion sound, which is a type of sporty sound. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2022-74885 Summary of the Invention [Problem to be solved by the invention]

[0004] In the above exhaust noise control, the ignition timing is significantly retarded to create an unstable combustion state known as a semi-misfire state. Since the combustion state in the semi-misfire state changes due to individual differences in internal combustion engines and aging, the volume and quality of the sound generated by the exhaust noise control may become unstable. [Means for solving the problem]

[0005] The control device for an internal combustion engine to solve the above problem is a control device for an internal combustion engine that executes exhaust noise control when transitioning from accelerator on to accelerator off, and as the exhaust noise control, alternates between burning the mixture by ignition and stopping the combustion of the mixture by stopping ignition within the combustion cycle. Effect of the Invention

[0006] This internal combustion engine control device can stabilize the sounds generated by exhaust sound control. [Brief description of the drawings]

[0007] [Figure 1] 1 is a schematic diagram showing a configuration of an internal combustion engine and a control device according to an embodiment; [Diagram 2] 4 is a flowchart showing a procedure of a process executed by the control device of the embodiment. [Diagram 3] 1 is a graph showing the relationship between the volume and quality of bubbling noise and the air excess ratio. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Hereinafter, a specific embodiment of a control device for an internal combustion engine mounted on a vehicle will be described with reference to Figs. 1 to 3. <Configuration of the internal combustion engine and control device> 1, an internal combustion engine 10 has a plurality of cylinders 11 that combust an air-fuel mixture. The internal combustion engine 10 of this embodiment is, for example, an in-line four-cylinder internal combustion engine.

[0009] The internal combustion engine 10 is provided with an intake passage 15 which serves as a passage for introducing air to each cylinder 11 . A throttle valve 16 that adjusts the amount of intake air is provided in the intake passage 15. The portion of the intake passage 15 downstream of the throttle valve 16 branches off for each cylinder. The portions of the intake passage 15 that branch off for each cylinder are connected to intake ports provided for each cylinder. Each intake port is provided with a fuel injection valve 17 for port injection.

[0010] Each cylinder 11 is provided with an ignition plug 19 that ignites the air-fuel mixture introduced into the cylinder 11 by spark discharge. The internal combustion engine 10 is provided with an exhaust passage 21 which serves as a discharge path for exhaust gas generated by combustion of an air-fuel mixture in each cylinder 11. An upstream portion of the exhaust passage 21 is branched off for each cylinder. The portions of the exhaust passage 21 which are branched off for each cylinder are connected to exhaust ports provided for each cylinder.

[0011] A catalyst 22 for purifying the exhaust gas is provided in the exhaust passage 21 . An air-fuel mixture containing fuel injected by a fuel injection valve 17 is introduced into each cylinder 11 of the internal combustion engine 10. When an ignition plug 19 ignites the air-fuel mixture, combustion takes place in the cylinder 11. Exhaust gas generated by the combustion is discharged from inside the cylinder 11 into an exhaust passage 21 and purified by a catalyst 22.

[0012] The control device 100 includes a CPU 110 and a memory 120 in which control programs and data are stored. The CPU 110 executes the programs stored in the memory 120, thereby carrying out various engine controls.

[0013] An air flow meter 81, which is an intake air amount sensor that detects an intake air amount GA, and a water temperature sensor 82 that detects a coolant temperature THW, which is the temperature of the coolant for the internal combustion engine 10, are connected to the control device 100, and output signals from these various sensors are input to the control device 100. A crank angle sensor 83 that detects a rotation angle of a crankshaft, and an accelerator sensor 84 that detects an accelerator operation amount ACCP, which is an operation amount of an accelerator pedal, are also connected to the control device 100, and output signals from these various sensors are input to the control device 100. A vehicle speed sensor 85 that detects a vehicle speed SP of the vehicle equipped with the internal combustion engine 10 is also connected to the control device 100, and an output signal from this sensor is input to the control device 100.

[0014] The control device 100 calculates the engine speed NE based on the output signal Scr of the crank angle sensor 83. The control device 100 also calculates an engine load factor KL based on the engine speed NE and the intake air amount GA. The engine load factor KL represents the ratio of the current cylinder inflow air amount to the cylinder inflow air amount when the internal combustion engine 10 is steadily operated with the throttle valve 16 fully open at the current engine speed NE. The cylinder inflow air amount is the amount of air that flows into each cylinder 11 during the intake stroke.

[0015] Based on output signals from the various sensors described above, the control device 100 executes various engine controls, such as fuel injection control by the fuel injection valve 17, intake air amount control by the throttle valve 16, and ignition control by the spark plug 19.

[0016] <About exhaust noise control> The control device 100 executes the following exhaust sound control to ensure a good sporty sound.

[0017] Figure 2 shows the procedure for exhaust sound control. The series of processes shown in Figure 2 starts when the accelerator pedal state changes from accelerator on to accelerator off. The accelerator pedal state is determined based on the accelerator operation amount ACCP. In the following, step numbers are represented by numbers preceded by "S."

[0018] When this process starts, the control device 100 first determines whether or not the execution conditions for exhaust sound control are met (S100). The execution conditions for exhaust sound control are set, for example, as the following condition (a) and condition (b), and when both condition (a) and condition (b) are met, the control device 100 determines that the execution conditions for exhaust sound control are met.

[0019] (a): The temperature of the catalyst 22 is within a predetermined range. For example, if the temperature of the catalyst 22 exceeds this range and is high, executing exhaust noise control may cause the temperature of the catalyst 22 to become excessively high. Condition (a) is set to prevent such an excessive rise in temperature of the catalyst 22. The temperature of the catalyst 22 may be either a value detected by a sensor or a value estimated by calculation.

[0020] (b): The engine speed NE is within a predetermined range. For example, when the engine speed NE is low, executing exhaust sound control may cause discomfort to vehicle occupants. Then, when it is determined that the conditions for executing the exhaust sound control are met (S100: YES), the control device 100 executes the exhaust sound control (S110).

[0021] The control device 100 executes the following process as exhaust noise control (S110). That is, the combustion of the air-fuel mixture by ignition and the stop of the combustion of the air-fuel mixture by stopping ignition are alternately performed in the combustion cycle. For example, in an in-line four-cylinder engine, when the cylinders are called the first cylinder, the second cylinder, the third cylinder, and the fourth cylinder in the order of the cylinders, the ignition order is the first cylinder, the third cylinder, the fourth cylinder, and the second cylinder. In this case, although fuel injection is performed in each cylinder, the air-fuel mixture is ignited only in the first and fourth cylinders. Or, the air-fuel mixture is ignited only in the third and second cylinders.

[0022] By performing such exhaust sound control, high-temperature combustion gas is sent from the cylinders that burn the air-fuel mixture to the exhaust passage 21. In addition, unburned gas containing air is sent from the cylinders that stop burning the air-fuel mixture to the exhaust passage 21. When the unburned gas is burned by the high-temperature combustion gas in the exhaust passage 21, a bubbling sound, which is a type of sports sound, is generated from within the exhaust passage 21.

[0023] FIG. 3 shows the relationship between the volume and sound quality of the bubbling sound and the excess air ratio λ of the mixture. The solid line L1 in FIG. 3 shows the relationship between the volume and excess air ratio λ of the bubbling sound. The dashed-dotted line L2 in FIG. 3 shows the relationship between the sound quality of the bubbling sound and the excess air ratio λ. The excess air ratio λ is equal to the value obtained by dividing the air-fuel ratio by the stoichiometric air-fuel ratio. When the air-fuel ratio matches the stoichiometric air-fuel ratio, the excess air ratio λ is "1", and when the excess air ratio λ is greater than "1", it indicates that the air-fuel ratio is leaner than the stoichiometric air-fuel ratio.

[0024] Moreover, the louder the volume of the bubbling sound, the more preferable it is. Moreover, the quality of the bubbling sound is preferably a bursting sound rather than a muffled sound. As shown in Fig. 3, the sound volume does not change significantly when the air excess ratio λ is in the range from "1" to "λb" which is greater than "1". When the air excess ratio λ becomes greater than "λb", the sound volume drops rapidly.

[0025] On the other hand, the sound quality gradually changes from a muffled sound to a more explosive sound as the air excess ratio λ increases from "1". Then, when the air excess ratio λ becomes larger than "λb", the sound quality remains closer to the explosive sound without any significant change.

[0026] Therefore, it is desirable that the excess air ratio λ of the mixture when exhaust noise control is being performed is within a range from the above "λb" to "λa" which is smaller than "λb" and larger than "1". In this embodiment, as an example, the target air-fuel ratio of the mixture is set so that the excess air ratio λ of the mixture when exhaust noise control is being performed is the above "λb". In addition, as an example, the target intake air amount when exhaust noise control is being performed is set to a value equivalent to the target intake air amount during idle operation. In addition, as an example, the ignition timing of the cylinder that performs ignition to burn the mixture is set to a value equivalent to the target ignition timing during idle operation.

[0027] Once exhaust sound control has been executed in this manner, the control device 100 then determines whether the duration Td is equal to or greater than the execution time T (S120). The duration Td is the time that has elapsed since the start of exhaust sound control. The execution time T is a value calculated by the control device 100 based on, for example, the engine speed NE and the engine load factor KL. The execution time T is the time during which the temperature of the catalyst 22 can be kept below the allowable upper limit temperature even when exhaust sound control is executed. For example, the higher the engine speed NE or the greater the engine load factor KL, the higher the temperature of the catalyst 22. Therefore, the higher the engine speed NE or the greater the engine load factor KL, the shorter the execution time T is set. Note that, Then, until it is determined in the process of S120 that the duration Td is equal to or greater than the execution time T, the control device 100 repeatedly executes the process of S110 and the process of S120.

[0028] On the other hand, when it is determined in the process of S120 that the duration Td is equal to or longer than the execution time T (S120: YES), the control device 100 ends the exhaust sound control (S130). When the exhaust sound control is ended in S130, the control device 100 performs fuel cut control or idle operation control according to the engine operating state at that time.

[0029] Then, when the process of S130 has been executed, or when a negative determination is made in the process of S100, the control device 100 ends this process. <Action and Effects> The operation and effects of this embodiment will be described.

[0030] As exhaust noise control, the combustion of the air-fuel mixture by ignition and the cessation of the combustion of the air-fuel mixture by stopping the ignition are alternately performed within the combustion cycle. Therefore, the combustion of the air-fuel mixture by ignition allows high-temperature combustion gas to be stably sent to the exhaust passage 21. Also, the cessation of the combustion of the air-fuel mixture by stopping the ignition allows unburned gas to be stably sent to the exhaust passage 21. Since the high-temperature combustion gas and unburned gas are stably sent to the exhaust passage 21 without variation, the bubbling sound generated by the combustion of the unburned gas is stably generated. Therefore, the volume and quality of the sound generated by the exhaust noise control are stabilized.

[0031] <Example of change> The above embodiment can be modified as follows: The above embodiment and the following modifications can be combined with each other to the extent that no technical contradiction occurs.

[0032] The cylinder for which the combustion of the air-fuel mixture is stopped by stopping ignition does not necessarily have to be fixed to a predetermined cylinder. For example, the cylinder for which the combustion of the air-fuel mixture is stopped by stopping ignition may be changed for each combustion cycle.

[0033] The number of cylinders in which the combustion of the air-fuel mixture is stopped by stopping ignition in one combustion cycle may be changed as desired within the range of "1" to "total number of cylinders - 1". The above-described exhaust noise control may be implemented in an internal combustion engine having a number or arrangement of cylinders other than an in-line four-cylinder engine.

[0034] The internal combustion engine 10 may be provided with a turbocharger in the exhaust passage 21. In this case, exhaust noise control is executed during deceleration to combust unburned gas, thereby suppressing a decrease in the rotation speed of the turbocharger. Therefore, turbo lag when transitioning from accelerator off to accelerator on can be suppressed.

[0035] The control device 100 includes a CPU 110 and a memory 120, and is not limited to executing software processing. For example, it may include a dedicated hardware circuit (e.g., ASIC, etc.) that processes at least a part of the software processing executed in each of the above embodiments. That is, the control device 100 may have any of the following configurations (a) to (c). (a) It includes a processing device that executes all of the above processing according to a program, and a program storage device such as a memory that stores the program. (b) It includes a processing device and a program storage device that executes part of the above processing according to a program, and a dedicated hardware circuit that executes the remaining processing. (c) It includes a dedicated hardware circuit that executes all of the above processing. Here, the software processing circuit including the processing device and the program storage device and the dedicated hardware circuit may be multiple. That is, the above processing may be executed by a processing circuit that includes at least one of one or more software processing circuits and one or more dedicated hardware circuits. [Explanation of symbols]

[0036] 10. Internal combustion engine 11…Cylinder 15…Intake passage 16...Throttle valve 17...Fuel injector 19…Spark plug 21...Exhaust passage 22...Catalyst 81...Air flow meter 82...Water temperature sensor 83...Crank angle sensor 84...Accelerator sensor 85...Vehicle speed sensor 100...Control device 110…CPU 120…Memory

Claims

[Claim 1] A control device for an internal combustion engine that executes exhaust noise control when an accelerator pedal transitions from on to off, The exhaust noise control is performed by alternately igniting the mixture and stopping the mixture from burning by stopping the ignition during the combustion cycle. A control device for an internal combustion engine.

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