Control device for v-type internal combustion engine

Abstract

To inhibit unburned fuel, which does not contribute to the generation of bubbling noise, from being discharged into an exhaust passage.SOLUTION: An internal combustion engine 1 is an eight-cylinder V-type internal combustion engine in which the ignition order of cylinders is set to be unevenly spaced. A control device 100 executes bubbling control when an accelerator is shifted from ON to OFF. This control device 100 prohibits the supply of fuel during execution of the bubbling control to the cylinder in which an intake air amount becomes the largest among all the cylinders and to the cylinder in which an intake air amount becomes the smallest.SELECTED DRAWING: Figure 2

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 with a V-type cylinder arrangement is known. Also, as described in Patent Document 2, an internal combustion engine that performs bubbling control to ensure a good sports sound is known. Bubbling control is a control that continues the combustion of the air-fuel mixture in a state where the ignition timing is significantly retarded without performing fuel cut when shifting from accelerator on to accelerator off. By thus significantly retarding the ignition timing to create a semi-misfire state, unburned gas burns in the exhaust passage, generating a popping sound, which is a type of sports sound.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, in an 8-cylinder V-type internal combustion engine with an unequal ignition order of cylinders, when the above bubbling control is executed, there is a possibility that unburned fuel that does not contribute to the generation of bubbling sound is discharged into the exhaust passage.

Means for Solving the Problems

[0005] The control device for a V-type internal combustion engine for solving the above problems is applied to an 8-cylinder V-type internal combustion engine whose ignition order of cylinders is set to be unevenly spaced, and is a control device that executes bubbling control when shifting from accelerator on to accelerator off. This control device prohibits the supply of fuel during the execution of the bubbling control in the cylinder with the largest intake air amount and the cylinder with the smallest intake air amount among all cylinders.

Effect of the Invention

[0006] This control device for a V-type internal combustion engine can suppress the discharge of unburned fuel that does not contribute to the generation of bubbling noise into the exhaust passage.

Brief Description of the Drawings

[0007]

Figure 1

Figure 2

Figure 3

Embodiment for Carrying Out the Invention

[0008] Hereinafter, an embodiment of a control device for a V-type internal combustion engine will be described with reference to the drawings. <Cylinder Arrangement of Internal Combustion Engine> As shown in FIG. 1, the internal combustion engine 1 is a V-type internal combustion engine having eight cylinders.

[0009] In the first bank 1A of the internal combustion engine 1, four cylinders such as cylinder No. 1, cylinder No. 3, cylinder No. 5, and cylinder No. 7 are arranged in series in order. In the second bank 1B of the internal combustion engine 1, four cylinders such as cylinder No. 2, cylinder No. 4, cylinder No. 6, and cylinder No. 8 are arranged in series in order.

[0010] <Configuration of Internal Combustion Engine and Control Device> As shown in FIG. 2, in each cylinder of the internal combustion engine 1 (only one cylinder is shown in FIG. 2), air is inhaled into the combustion chamber 2 through an intake port 3a connected to the intake passage 3, and fuel injected from a fuel injection valve 4 is supplied to the combustion chamber 2. When the air-fuel mixture composed of air and fuel is ignited by a spark plug 5, the air-fuel mixture burns and the piston 6 reciprocates, causing the crankshaft 7, which is the output shaft of the internal combustion engine 1, to rotate. The shape of the crankshaft 7 in the present embodiment is a cross-plane. In an eight-cylinder V-type internal combustion engine equipped with this cross-plane crankshaft 7, the ignition order of the cylinders is set to be unevenly spaced. That is, in the internal combustion engine 1, the ignition order of the cylinders is in the order of cylinder No. 1, cylinder No. 8, cylinder No. 7, cylinder No. 2, cylinder No. 4, cylinder No. 3, cylinder No. 6, and cylinder No. 5.

[0011] The air-fuel mixture after burning in the combustion chamber 2 is discharged as exhaust into the exhaust passage 8. A catalyst 15 for purifying the exhaust is provided in the exhaust passage 8. An intake passage 3 of the internal combustion engine 1 is provided with a throttle valve 29 for measuring the intake air amount. The opening degree of this throttle valve 29 is adjusted by an electric motor.

[0012] An intake valve 9 is provided at the intake port 3a connected to the intake passage 3. An exhaust valve 10 is provided at the exhaust port 8a 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 spark plug 5, in order to control torque, exhaust component ratio, etc. as control amounts. In FIG. 1, the operation signals MS1 to MS3 of the throttle valve 29, the fuel injection valve 4, and the spark plug 5 are described respectively.

[0013] The control device 100 includes a CPU 120 and a memory 130 composed of a ROM and a RAM, etc. By the CPU 120 executing the program stored in the memory 130, various controls are implemented.

[0014] When implementing various controls, the control device 100 refers to the output signal of the accelerator position sensor 28 that detects the accelerator operation amount ACCP, which is the operation amount of the accelerator pedal 27 operated by the driver of the vehicle equipped with the internal combustion engine 1. Also, the control device 100 refers to the throttle opening TA, which is the opening of the throttle valve 29 detected by the throttle sensor 30, and the intake air amount GA detected by the air flow meter 31. Further, the control device 100 refers to the coolant temperature THW detected by the coolant temperature sensor 33 and the engine rotational speed NE calculated from the output signal Scr of the crank angle sensor 34. Additionally, the control device 100 refers to the signal of the vehicle speed sensor 38 that detects the vehicle speed SP of the vehicle equipped with the internal combustion engine 1.

[0015] Based on the 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 4, intake air amount control by the throttle valve 29, and ignition control by the ignition plug 5.

[0016] <Bubbling control> The control device 100 executes bubbling control to ensure a good sports sound.

[0017] Bubbling control is a control that is executed when the state of the accelerator pedal 27 transitions from accelerator on to accelerator off. When the state of the accelerator pedal 27 transitions to accelerator 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, the fuel injection from the fuel injection valve 4 and the ignition of the air-fuel mixture by the ignition plug 5 are continued. By thus significantly retarding the ignition timing and burning the air-fuel mixture in a semi-misfire state, a bubbling sound (explosion sound), which is a type of sports sound, is generated from the exhaust passage 8 and the like.

[0018] During the execution of the bubbling control, the fuel injection amount is, for example, equal to or less than the amount of fuel injected during idling operation. Further, the air-fuel ratio of the air-fuel mixture is controlled to be leaner than the stoichiometric air-fuel ratio.

[0019] The bubbling control ends when a predetermined time has elapsed. After the bubbling control ends, fuel cut control or idling operation control is performed according to the engine operating state at that time.

[0020] Note that, as preconditions for permitting the execution of the bubbling control, for example, the following conditions (a) and (b) are set, and when both conditions (a) and (b) are satisfied, the control device 100 performs 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 extremely high beyond this range, the temperature of the catalyst 15 may become excessively high. Condition (a) is set to suppress such an over-temperature 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] Fig. 3 shows, for each cylinder, the relationship between the air-fuel ratio of the air-fuel mixture during the execution of the bubbling control and the number of occurrences of the bubbling combustion. The number of occurrences of the bubbling combustion is the number of combustions in which the bubbling sound has occurred within a predetermined period, and is shown as a bar graph in Fig. 3. Further, the values indicated by the open circles in Fig. 3 are the average air-fuel ratios of the air-fuel mixtures in the respective cylinders during the execution of the bubbling control. Also, the appropriate range AFb shown in this figure is the range of the air-fuel ratio in which the combustion generating the bubbling sound is likely to occur.

[0024] As shown in FIG. 3, an internal combustion engine 1, which is an eight-cylinder V-type internal combustion engine with an unequal ignition order for cylinders, has a large variation in the intake air amount among the cylinders. Therefore, there is a tendency for the variation in the air-fuel ratio of the air-fuel mixture among the cylinders to increase. Further, during the execution of the bubbling control, the combustion of the air-fuel mixture becomes unstable, so the above-mentioned appropriate range AFb is in a relatively narrow range. Here, in the No. 3 cylinder #3 where the intake air amount is the largest among all the cylinders, the air-fuel ratio of the air-fuel mixture becomes the leanest and may deviate significantly from the appropriate range AFb. Also, in the No. 5 cylinder #5 where the intake air amount is the smallest among all the cylinders, the air-fuel ratio of the air-fuel mixture becomes the richest, and in this case too, there is a possibility of deviating significantly from the appropriate range AFb. When the air-fuel ratio of the air-fuel mixture becomes lean or rich in this way and deviates from the appropriate range AFb, in the No. 3 cylinder #3 where the intake air amount is the largest and the No. 5 cylinder #5 where the intake air amount is the smallest, the combustion that generates bubbling noise is less likely to occur, and misfire is more likely to occur. Therefore, there is a possibility that the fuel supplied to such No. 3 cylinder #3 and No. 5 cylinder #5 is discharged into the exhaust passage 8 without being burned.

[0025] Therefore, the control device 100 prohibits the supply of fuel to the No. 3 cylinder #3 and the No. 5 cylinder #5 by stopping the fuel injection from the fuel injection valve 4 during the execution of the bubbling control in the No. 3 cylinder #3 where the intake air amount is the largest among all the cylinders and the No. 5 cylinder #5 where the intake air amount is the smallest among all the cylinders.

[0026] Note that the cylinder with the largest intake air amount among all the cylinders and the cylinder with the smallest intake air amount among all the cylinders are always the same cylinders in an eight-cylinder V-type internal combustion engine with an unequal ignition order for cylinders and do not change depending on the engine operating state or the like. Therefore, in the present embodiment, the cylinder with the largest intake air amount among all the cylinders and the cylinder with the smallest intake air amount among all the cylinders are grasped through preliminary experiments or the like. Then, in the grasped No. 3 cylinder #3 and No. 5 cylinder #5, the supply of fuel is prohibited during the execution of the bubbling control.

[0027] <Actions and Effects of the Present Embodiment> In an internal combustion engine 1 in which the ignition order of cylinders is unevenly spaced, in the third cylinder #3 where the intake air amount is the largest among all cylinders and the fifth cylinder #5 where the intake air amount is the smallest among all cylinders, fuel supply during the execution of bubbling control is prohibited. Therefore, it is possible to suppress unburned fuel that does not contribute to the generation of bubbling noise from being discharged into the exhaust passage 8.

[0028] <Modified Example> Note that the above embodiment can be modified and implemented as follows. The above embodiment and the following modified examples can be implemented in combination with each other within a technically non - conflicting range.

[0029] · In an internal combustion engine 1 in which the ignition order of cylinders is unevenly spaced, the cylinders in which fuel supply is prohibited during the execution of bubbling control are not limited to the third cylinder #3 and the fifth cylinder #5. That is, the cylinder with the largest intake air amount among all cylinders and the cylinder with the smallest intake air amount among all cylinders are grasped through preliminary experiments or the like. Then, in the grasped cylinders, fuel supply may be prohibited during the execution of bubbling control.

[0030] · 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 (such as an 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 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 a plurality of software processing circuits including a processing device and a program storage device, and a plurality of dedicated hardware circuits. That is, the above processing may be executed by a processing circuit including at least one of one or more software processing circuits and one or more dedicated hardware circuits.

Explanation of Signs

[0031] 1…Internal combustion engine 1A…First bank 1B…Second bank 2…Combustion chamber 3…Intake passage 3a…Intake port 4…Fuel injection valve 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

[Claim 1] A control device that is applied to an eight-cylinder V-type internal combustion engine in which the ignition order of the cylinders is set to be unevenly spaced, and that executes bubbling control when the engine transitions from accelerator-on to accelerator-off, The supply of fuel during execution of the bubbling control is prohibited in the cylinder with the largest intake air amount and the cylinder with the smallest intake air amount among all the cylinders. A control device for a V-type internal combustion engine.

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