Control device for V-type internal combustion engines

Abstract

You get a good sporty sound when you activate the bubbling control. [Solution] The internal combustion engine 1 is a V-type internal combustion engine in which the firing order of the cylinders is set to be unequal between banks. The control device 100 performs bubbling control when the accelerator is released from on. The range of lean air-fuel ratio in which bubbling sound is produced by the bubbling control is set to an appropriate range. When bubbling control is performed, the control device 100 sets the predetermined fuel injection amount for each cylinder so that the in-cylinder air-fuel ratio is within an appropriate range.

Description

Technical Field

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

Background Art

[0002] For example, as described in Patent Document 1, an internal combustion engine that performs bubbling control to ensure a good sports sound is known. Bubbling control is a control in which when shifting from accelerator on to accelerator off, the combustion of the air-fuel mixture is continued in a state where the ignition timing is significantly retarded without performing fuel cut. By thus significantly retarding the ignition timing to create a semi-misfire state, unburned gas burns in the exhaust passage, generating a bubbling sound (explosion sound), which is a kind of sports sound.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The generation of the bubbling sound by bubbling control is likely to occur when the in-cylinder air-fuel ratio, which is the air-fuel ratio of the air-fuel mixture in the cylinder, is within a predetermined lean air-fuel ratio (an air-fuel ratio leaner than the theoretical air-fuel ratio) suitable for the generation of the bubbling sound.

[0005] Here, in a V-type internal combustion engine where the ignition order of the cylinders is unevenly spaced between banks, variations in the air amount occur between the cylinders. When performing bubbling control in a state where such variations in the air amount occur, there may be a cylinder in which the in-cylinder air-fuel ratio deviates from the range of the lean air-fuel ratio suitable for the generation of the bubbling sound. Therefore, there is a possibility that a cylinder in which the above-described sports sound is not sufficiently generated may occur.

Means for Solving the Problems

[0006] The control device for a V-type internal combustion engine that solves the above problem is applied to a V-type internal combustion engine in which the ignition order of the cylinders is set to be unequal between banks, and performs bubbling control when transitioning from accelerator on to accelerator off. This control device sets the range of lean air-fuel ratio in which bubbling sound is generated by the bubbling control to an appropriate range, and sets the predetermined fuel injection amount for each cylinder so that the in-cylinder air-fuel ratio is within the appropriate range when the bubbling control is executed. [Effects of the Invention]

[0007] The control system for this V-type internal combustion engine can produce a sporty sound when bubbling control is performed. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a schematic diagram showing the cylinder arrangement of an internal combustion engine in one embodiment. [Figure 2] Figure 2 is a schematic diagram showing the configuration of the internal combustion engine and control device in the same embodiment. [Figure 3] Figure 3 is a graph showing the relationship between the cylinder air-fuel ratio and the number of bubbling combustion occurrences for each cylinder in the same embodiment. [Figure 4] Figure 4 is a graph showing the fuel injection amount correction coefficient for each cylinder in the same embodiment. [Figure 5] Figure 5 is a graph showing the cylinder air-fuel ratio before and after correction of the fuel injection amount in the same embodiment. [Modes for carrying out the invention]

[0009] The following describes one embodiment of a control device for a V-type internal combustion engine, with reference to the drawings. <Cylinder arrangement of an internal combustion engine> As shown in Figure 1, the internal combustion engine 1 is a V-type internal combustion engine having eight cylinders.

[0010] The first bank 1A of the internal combustion engine 1 has four cylinders arranged in series in sequence: cylinder #1, cylinder #3, cylinder #5, and cylinder #7. In the second bank 1B of internal combustion engine 1, four cylinders are arranged in series in sequence: cylinder #2, cylinder #4, cylinder #6, and cylinder #8.

[0011] <Configuration of internal combustion engine and control system> As shown in Figure 2, in each cylinder of the internal combustion engine 1 (one cylinder is shown in Figure 2), air is drawn into the combustion chamber 2 through the intake port 3a connected to the intake passage 3, and fuel injected from the fuel injection valve 4 is supplied to the combustion chamber 2. When the spark plug 5 ignites the air-fuel mixture, the mixture burns, causing the piston 6 to reciprocate and the crankshaft 7, which is the output shaft of the internal combustion engine 1, to rotate. The shape of the crankshaft 7 in this embodiment is crossplane. In an 8-cylinder V-type internal combustion engine equipped with this crossplane crankshaft 7, the firing order of the cylinders is set so that they are spaced unequally between banks. That is, in the internal combustion engine 1, the firing order of the cylinders is as follows: cylinder 1 #1, cylinder 8 #8, cylinder 7 #7, cylinder 2 #2, cylinder 4 #4, cylinder 3 #3, cylinder 6 #6, and cylinder 5 #5.

[0012] The fuel-air mixture after combustion in the combustion chamber 2 is discharged as exhaust into the exhaust passage 8. The exhaust passage 8 is equipped with a catalyst 15 for purifying the exhaust. The intake passage 3 of the internal combustion engine 1 is equipped with a throttle valve 29 for regulating the amount of intake air. The opening degree of this throttle valve 29 is adjusted by an electric motor.

[0013] An intake valve 9 is provided in the intake port 3a, which is connected to the intake passage 3. An exhaust valve 10 is provided in the exhaust port 8a, which is connected to the exhaust passage 8. The control device 100 controls the internal combustion engine 1, and operates the operating parts of the internal combustion engine 1 such as the throttle valve 29, the fuel injection valve 4, and the ignition plug 5 in order to control the torque, the exhaust component ratio, etc. as its control quantities. In FIG. 1, the operation signals MS1 to MS3 of the throttle valve 29, the fuel injection valve 4, and the ignition plug 5 are described.

[0014] The control device 100 includes a CPU 120 and a memory 130 composed of a ROM and a RAM, etc. The CPU 120 executes the programs stored in the memory 130 to perform various controls.

[0015] When performing various controls, the control device 100 refers to the output signal of an accelerator position sensor 28 that detects an accelerator operation amount ACCP, which is the operation amount of an accelerator pedal 27 operated by a driver of a vehicle equipped with the internal combustion engine 1. Also, the control device 100 refers to the throttle opening TA, which is the opening degree of the throttle valve 29 detected by a throttle sensor 30, and the intake air amount GA detected by an air flow meter 31. Further, the control device 100 refers to the coolant water temperature THW detected by a water temperature sensor 33 and the engine rotational speed NE calculated from the output signal Scr of a crank angle sensor 34. Also, the control device 100 refers to the signal of a vehicle speed sensor 38 that detects the vehicle speed SP of a vehicle equipped with the internal combustion engine 1.

[0016] Based on the output signals, etc. from the various sensors described above, the control device 100 executes various engine controls such as fuel injection control by the fuel injection valve 4, intake air amount control by the throttle valve 29, and ignition control by the ignition plug 5.

[0017] <Bubbling control> The control device 100 executes bubbling control in order to ensure a good sports sound.

[0018] The bubbling control is a control that is executed when the state of the accelerator pedal 27 shifts from being on to off. When the state of the accelerator pedal 27 shifts to off, the control device 100 does not immediately execute fuel cut control. Instead, as bubbling control, it continues the combustion of the air-fuel mixture in a state where the ignition timing is significantly retarded. That is, it continues the fuel injection from the fuel injection valve 4 and continues the ignition of the air-fuel mixture by the spark plug 5 in a state where the ignition timing is significantly retarded. By thus significantly retarding the ignition timing and burning the air-fuel mixture in a semi-misfire state, a bubbling sound, which is a type of sports sound, is generated from the exhaust passage 8 or the like. Note that the air-fuel ratio of the air-fuel mixture during the execution of the bubbling control is controlled to be a lean air-fuel ratio that is leaner than the theoretical air-fuel ratio.

[0019] The above-described bubbling control ends its execution when a predetermined time has elapsed. After the bubbling control ends, fuel cut control or idle operation control is implemented according to the engine operating state at that time.

[0020] As prerequisite conditions for permitting the execution of the bubbling control, for example, the following conditions (a) and condition (b) are set. When both condition (a) and condition (b) are satisfied, the control device 100 implements the bubbling control.

[0021] (a): The temperature of the catalyst 15 is within a predetermined range. For example, if the bubbling control is executed when the temperature of the catalyst 15 is higher than this range, the temperature of the catalyst 15 may become excessively high. Condition (a) is set to suppress such an excessive temperature rise of the catalyst 15. Note that the temperature of the catalyst 15 may be either a detected value by a sensor or an estimated value by calculation.

[0022] (b): The engine rotational speed NE is within a predetermined range. For example, if the bubbling control is executed when the engine rotational speed NE is low, it may give a sense of discomfort to vehicle occupants or the like.

[0023] Figure 3 shows the relationship between the in-cylinder air-fuel ratio and the number of bubbling combustion occurrences for each cylinder during bubbling control. The in-cylinder air-fuel ratio is the air-fuel ratio of the mixture inside the cylinder. The number of bubbling combustion occurrences is the number of combustions that produced a bubbling sound within a predetermined period, and is shown as a bar graph in Figure 3. The values ​​shown as white circles in Figure 3 are the average values ​​of the in-cylinder air-fuel ratio for each cylinder during bubbling control. The appropriate range AFb shown in Figure 3 is the range of air-fuel ratios in which combustion that produces a bubbling sound is likely to occur, and is a range of lean air-fuel ratios that are leaner than the stoichiometric air-fuel ratio. For example, the appropriate range AFb is an in-cylinder air-fuel ratio in the range of approximately 16 to approximately 19.

[0024] Internal combustion engine 1, an 8-cylinder V-type internal combustion engine in which the firing order of the cylinders is unevenly spaced between banks, experiences variations in intake air volume between cylinders. When bubbling control is performed while such variations in intake air volume are present, some cylinders may experience an in-cylinder air-fuel ratio outside the appropriate range AFb.

[0025] Here, variations in intake air volume between cylinders have a unique tendency in internal combustion engines and can be determined in advance through experiments, etc. Therefore, cylinders whose in-cylinder air-fuel ratio falls outside the above-mentioned appropriate range AFb can be known in advance.

[0026] For example, in the internal combustion engine 1 of this embodiment, if the fuel injection amount during bubbling control is the same for each cylinder, the in-cylinder air-fuel ratios of each cylinder tend to be in the following order from smallest to largest: cylinder 5 #5, cylinder 2 #2, cylinder 4 #4, cylinder 7 #7, cylinder 1 #1, cylinder 6 #6, cylinder 8 #8, and cylinder 3 #3. The in-cylinder air-fuel ratios of cylinder 5 #5, cylinder 2 #2, and cylinder 4 #4 are richer than the appropriate range AFb. The in-cylinder air-fuel ratios of cylinder 7 #7, cylinder 1 #1, and cylinder 6 #6 are within the appropriate range AFb. The in-cylinder air-fuel ratios of cylinder 8 #8 and cylinder 3 #3 are leaner than the appropriate range AFb. Consequently, combustion that produces a bubbling sound becomes less likely in cylinders other than cylinder #7, cylinder #1, and cylinder #6, and misfires become more likely. Furthermore, if a misfire occurs, unburned fuel may be discharged into the exhaust passage 8.

[0027] Therefore, in this embodiment, the fuel injection amount for each cylinder is set in advance so that the in-cylinder air-fuel ratio is within the appropriate range AFb when bubbling control is performed. In other words, during the execution of bubbling control, the control device 100 sets the fuel injection amount Q(n) of the fuel injector 4 provided for each cylinder based on the following equation (1). Herein, "n" indicates the number of each cylinder. In this embodiment, "n" is "1 to 8".

[0028] Fuel injection amount Q(n) = Base value Qb × Correction coefficient K(n) ... (1) The base value Qb is the basic value of the fuel injection amount Q(n) during bubbling control and is preset. For example, the base value Qb is equal to or less than the amount of fuel injected during idle operation.

[0029] The correction coefficient K(n) is a value multiplied by the base value Qb and is preset for each cylinder. This correction coefficient K(n) is a value for setting the fuel injection amount for each cylinder so that the in-cylinder air-fuel ratio falls within the appropriate range AFb during the execution of bubbling control. When the correction coefficient K(n) is greater than 1, the fuel injection amount Q(n) is incrementally corrected with respect to the base value Qb. On the other hand, when the correction coefficient K(n) is less than 1, the fuel injection amount Q(n) is decrementally corrected with respect to the base value Qb.

[0030] Therefore, for cylinders where the in-cylinder air-fuel ratio deviates to the rich side with respect to the appropriate range AFb, the greater the degree of deviation to the rich side of the cylinder, the smaller the value of the correction coefficient K(n) is set so that the decremental correction amount of the fuel injection amount becomes larger. On the other hand, for cylinders where the in-cylinder air-fuel ratio deviates to the lean side with respect to the appropriate range AFb, the greater the degree of deviation to the lean side of the cylinder, the larger the value of the correction coefficient K(n) is set so that the incremental correction amount of the fuel injection amount becomes larger.

[0031] Figure 4 shows the correction coefficient K(n) for each cylinder. The correction coefficients K(n) for each cylinder are in the order from small to large as "K(5) < K(2) < K(4) < K(7) = K(1) = K(6) < K(8) < K(3)". Since the correction coefficients K(7), K(1), and K(6) are all set to "1", the correction of the fuel injection amount is not substantially performed, and the base value Qb is directly set as the fuel injection amount Q(n).

[0032] Since the correction coefficients K(5), K(2), and K(4) are all set to values less than "1", the fuel injection amount Q(n) is decrementally corrected with respect to the base value Qb. Therefore, the in-cylinder air-fuel ratios of cylinder No. 5, cylinder No. 2, and cylinder No. 4 change to the lean side compared to before the correction of the fuel injection amount.

[0033] On the other hand, since both correction coefficients K(8) and K(3) are set to values ​​greater than "1", the fuel injection amount Q(n) is increased relative to the base value Qb. Consequently, the in-cylinder air-fuel ratios of cylinder #8 and cylinder #3 change to a richer state compared to before the fuel injection amount correction.

[0034] <Operation of this embodiment> During bubbling control, the fuel injection amount Q(n) for each cylinder is set by multiplying the base value Qb by the correction coefficient K(n) set for each cylinder. Therefore, the air-fuel ratio for each cylinder is as follows.

[0035] As shown in Figure 5, for cylinders #5, #2, and #4, where the amount of air drawn into the cylinder is small and the cylinder air-fuel ratio tends to deviate from the proper range AFb, the fuel injection amount Q(n) is reduced. As a result, the in-cylinder air-fuel ratios of cylinders #5, #2, and #4 change to a leaner side compared to before the fuel injection amount correction, bringing them within the proper range AFb.

[0036] On the other hand, for cylinders #8 and #3, which tend to have a larger amount of air intake and therefore a leaner air-fuel ratio compared to the proper AFb range, the fuel injection amount Q(n) is increased. As a result, the air-fuel ratios in cylinders #8 and #3 change to a richer side compared to before the fuel injection amount correction, bringing them within the proper AFb range.

[0037] <Effects of this embodiment> (1) When bubbling control is performed, the fuel injection amounts for cylinders #5, #2, #4, #8, and #3 are predetermined to be within the appropriate range AFb for the in-cylinder air-fuel ratio. As a result, a bubbling sound is generated in each cylinder, allowing for a full sporty sound to be obtained when bubbling control is performed.

[0038] (2) A bubbling sound will be generated in each cylinder. As a result, it is possible to suppress the discharge of unburned fuel that does not contribute to the generation of the bubbling sound into the exhaust passage 8. <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.

[0039] The correction factor K(n) was a value multiplied by the base value Qb. Alternatively, the correction factor K(n) may be a value added to or subtracted from the base value Qb. The fuel injection amount Q(n) for each cylinder was set by correcting the base value Qb with a correction coefficient K(n). Alternatively, the fuel injection amount Q(n) for each cylinder may be set individually in advance. In this case, for example, the same value obtained by multiplying the base value Qb by the correction coefficient K(n) may be set in advance as the fuel injection amount Q(n) for each cylinder.

[0040] The control device 100 includes a CPU 120 and a memory 130, and is not limited to executing software processing. For example, it may include a dedicated hardware circuit (e.g., an ASIC) that processes at least a part of the software processing performed 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 unit 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 unit and a program storage device that execute a 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, there may be multiple software processing circuits that include a processing unit and a program storage device, and multiple dedicated hardware circuits. 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]

[0041] 1…Internal combustion engine 1A…Bank 1 1B...Bank 2 2… Combustion chamber 3…Intake passage 3a... Intake port 4…Fuel injector 5... Spark plug 6… Piston 7... Crankshaft 8... Exhaust passage 8a... Exhaust port 9…Intake valve 10… Exhaust valve 15…Catalyst 29... Throttle valve 30…Throttle sensor 31…Air flow meter 33...Water temperature sensor 34... Crank angle sensor 38... Vehicle speed sensor 100...Control device 120...CPU 130...memory

Claims

1. A control device applied to a V-type internal combustion engine in which the ignition order of the cylinders is set to be unequal between banks, which performs bubbling control when transitioning from accelerator on to accelerator off, The range of lean air-fuel ratios in which bubbling noise occurs is set to an appropriate range by the aforementioned bubbling control. When the bubbling control is executed, the fuel injection amount for each cylinder is set in advance so that the in-cylinder air-fuel ratio falls within the appropriate range. Control device for a V-type internal combustion engine.

2. When the bubbling control is executed, the predetermined fuel injection amount for each cylinder is set individually by multiplying a predetermined base value by a correction coefficient set for each cylinder. A control device for a V-type internal combustion engine according to claim 1.

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