JP2018135793A - Spark ignition type internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a spark ignition type internal combustion engine for suppressing the worsening of a torque fluctuation without reducing thermal efficiency by simply specifying a factor for the torque fluctuation and performing processing according to the factor.SOLUTION: When the torque fluctuation is in the state of a torque fluctuation limit greater than a predetermined fluctuation amount (S104: Yes) and in the state of strong knock generation where strong knock is generated (S106: Yes), a determination is made that the spark of a spark plug of the internal combustion engine blows off (S108) and blow-off suppression control is performed to suppress the blow-off of the spark (S112). When the torque fluctuation is in the state of the torque fluctuation limit (S104: Yes) and not in the state of the strong knock generation (S106: No), a determination is made that a combustion period for the internal combustion engine is longer (S110) and combustion period shortening control is performed to shorten the combustion period (S114).SELECTED DRAWING: Figure 6

Description

  The present invention relates to control of a spark ignition type internal combustion engine.

  It is known that a spark-ignition internal combustion engine that performs combustion at a high A / F (air-fuel ratio) or high EGR (exhaust gas recirculation) rate has a large combustion fluctuation. As the combustion fluctuation increases (deteriorates), the torque fluctuation increases (deteriorates). Conventionally, in that case, it is known that it can be suppressed by reducing A / F or reducing the EGR rate.

  One of the causes of combustion fluctuation is misfire due to the blowout of sparks. As a method of determining the presence or absence of misfire, a method of determining based on the rotational speed fluctuation amount of an internal combustion engine is known (see, for example, Patent Documents 1 and 2).

Japanese Patent No. 2982381 JP 2009-138663 A

  By the way, even if the factor of the combustion fluctuation (the factor of the torque fluctuation) is not specified, the deterioration of the combustion fluctuation can be suppressed by uniformly reducing the A / F or the EGR rate. However, there is a problem that the thermal efficiency is lowered in the countermeasure.

  Accordingly, an object of the present invention is to easily identify a factor of combustion variation (factor of torque variation) and perform a process corresponding to the factor, thereby deteriorating combustion variation without deteriorating thermal efficiency (deteriorating torque variation). ).

  The spark ignition internal combustion engine according to the present invention employs the following means in order to achieve the above object.

  A spark ignition type internal combustion engine according to the present invention is a spark ignition type internal combustion engine, and includes torque fluctuation detection means for detecting torque fluctuation in the internal combustion engine, and knock detection means for detecting occurrence of knock in the internal combustion engine. And control means for controlling the torque fluctuation in the internal combustion engine, wherein the control means is in a torque fluctuation worsening state where the torque fluctuation is greater than a predetermined fluctuation amount, and the knock occurs. When the knock occurrence state is being performed, blowout suppression control is performed to suppress the spark of the internal combustion engine from blowing off, and when the torque fluctuation is in a deteriorated state and not in the knock occurrence state The gist is that the combustion period shortening control is performed to shorten the combustion period of the internal combustion engine.

  In one aspect of the present invention, it is preferable that the knock detection unit detects the occurrence of the knock for each cylinder, and the control unit performs the blow-off suppression control according to the knock occurrence state for each cylinder. It is.

  In one aspect of the present invention, the knock detecting means is an in-cylinder pressure sensor that detects a pressure in the cylinder, and the control means is configured such that a high-frequency pressure vibration component extracted from the pressure in the cylinder is the internal combustion engine. It is preferable that the knock occurrence state is determined when a predetermined value is exceeded according to at least one of the rotation speed and the torque.

  In one aspect of the present invention, the knock detection means is a knock sensor that detects the strength of the knock, and the control means determines whether the knock intensity is at least one of a rotational speed and torque of the internal combustion engine. It is preferable that the knocking state is determined when the predetermined strength is exceeded.

  In one aspect of the present invention, it is preferable that the control means performs the blow-off suppression control by controlling an airflow adjustment valve so as to reduce the airflow in the cylinder.

  In one aspect of the present invention, it is preferable that the control means performs the combustion period shortening control by controlling an airflow adjustment valve so as to increase the airflow in the cylinder.

  In one aspect of the present invention, it is preferable that the control means performs the combustion period shortening control by controlling the timing of the intake valve so as to raise the gas temperature in the cylinder.

  The spark ignition type internal combustion engine according to the present invention is a spark ignition type internal combustion engine, a torque fluctuation detecting means for detecting a fluctuation in torque in the internal combustion engine, and a pressure for detecting a pressure in a cylinder of the internal combustion engine. Detecting means, and control means for performing control for suppressing fluctuation of the torque in the internal combustion engine, wherein the control means is in a torque fluctuation deterioration state in which the torque fluctuation is larger than a predetermined fluctuation amount, and When the maximum pressure in the cylinder of the internal combustion engine is in a high pressure state exceeding a predetermined pressure, blowout suppression control is performed to suppress blowout of the spark of the internal combustion engine, and the torque fluctuation The gist is to perform combustion period shortening control for shortening the combustion period of the internal combustion engine when the engine is in a deteriorated state and not in the high pressure state.

  According to the present invention, it is possible to easily identify the cause of torque fluctuation from the occurrence of knocking or the maximum pressure in the cylinder, and processing is performed according to the factor, so torque fluctuation without reducing thermal efficiency. Can be prevented.

It is a schematic sectional drawing which shows an example of the cylinder of the spark ignition type internal combustion engine in embodiment of this invention. It is a schematic sectional drawing which shows an example of piping around each cylinder of the spark ignition internal combustion engine in embodiment of this invention. It is a figure which shows an example of the in-cylinder pressure log | history of the multiple cycles at the time of the combustion fluctuation deterioration by spark blow-out (misfire) occurrence. It is a figure which shows the time change of the cylinder pressure of the multiple cycles of FIG. It is a figure which shows an example of the in-cylinder pressure log | history of the multiple cycles at the time of the combustion fluctuation deterioration by extension of a combustion period. It is a flowchart which shows the flow of control which suppresses the deterioration of the torque fluctuation in embodiment of this invention. It is a flowchart which shows the flow of control which suppresses the deterioration of the torque fluctuation in other embodiment of this invention. It is a flowchart which shows the flow of control which suppresses the deterioration of the torque fluctuation in other embodiment of this invention.

  Hereinafter, embodiments of a spark ignition type internal combustion engine of the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic cross-sectional view showing an example of a cylinder of a spark ignition type internal combustion engine 100 in the present embodiment. The spark ignition internal combustion engine 100 of this embodiment is a four-cylinder engine composed of four cylinders. However, the spark ignition internal combustion engine 100 may be a six-cylinder engine or the like, and the number of cylinders is not limited to four. Hereinafter, the spark ignition internal combustion engine 100 will be simply referred to as the internal combustion engine 100 as appropriate.

  As shown in FIG. 1, the internal combustion engine 100 includes a cylinder 42 including a cylinder block 40 and a cylinder head 41 fixed to the upper portion of the cylinder block 40, and the cylinder 42 forms four cylinders 10. Has been. In FIG. 1, one of the four cylinders is shown.

  A piston 50 is accommodated in the cylinder 10 so as to be able to reciprocate, and a combustion chamber 43 of each cylinder 10 is formed by the cylinder block 40, the cylinder head 41, and the piston 50. The internal combustion engine 100 performs a series of four strokes including an intake stroke, a compression stroke, a combustion stroke, and an exhaust stroke while the piston 50 reciprocates twice. One cycle is constituted by a series of four strokes.

  The piston 50 housed in the cylinder 10 is connected to a crankshaft (not shown) via a connecting rod 51. The connecting rod 51 converts the reciprocating motion of the piston 50 into the rotational motion of the crankshaft.

  As shown in FIG. 1, the cylinder head 41 is formed with an intake port 60 that communicates with the combustion chamber 43 and an exhaust port 62 that communicates with the combustion chamber 43. Further, an intake valve 64 that opens and closes the boundary between the intake port 60 and the combustion chamber 43 and an exhaust valve 66 that opens and closes the boundary between the exhaust port 62 and the combustion chamber 43 are provided. The intake port 60 is provided with an injector 56 and an airflow adjustment valve 58. The injector 56 injects fuel (for example, hydrocarbon fuel such as gasoline). The airflow adjustment valve 58 is a swirl control valve or a tumble control valve, and can adjust the strength of the airflow. Fuel is injected from the injector 56 into the intake port 60, and a mixture of fuel and air is introduced into the combustion chamber 43 during the intake stroke.

  An ignition plug 46 is disposed in the cylinder head 41 with its spark discharge portion facing the combustion chamber 43, and the mixture in the combustion chamber 43 is ignited by the spark discharge of the ignition plug 46 at the ignition timing. Thus, the air-fuel mixture in the combustion chamber 43 is burnt and burned. Thereby, the piston 50 is reciprocated, and the crankshaft is rotated via the connecting rod 51. The combustion gas in the combustion chamber 43 is discharged to the exhaust port 62 in the exhaust stroke.

  The internal combustion engine 100 includes an ECU 90, a torque sensor 30 that detects the torque of the internal combustion engine 100, and an in-cylinder pressure sensor 34 that detects the pressure in the cylinder 10 (combustion chamber 43). The in-cylinder pressure sensor 34 is provided for each cylinder 10 and detects the pressure in each cylinder 10. The ECU 90 controls the spark plug 46, the injector 56, the airflow adjustment valve 58, the intake valve 64, the exhaust valve 66, and the like. Detection values of the torque sensor 30 and the in-cylinder pressure sensor 34 are input to the ECU 90.

  FIG. 2 is a schematic cross-sectional view showing an example of piping around each cylinder of the internal combustion engine 100 in the present embodiment. As shown in FIG. 2, the internal combustion engine 100 includes an intake pipe 13 through which air flowing from outside the vehicle is guided, and an intake manifold 15 that connects the intake pipe 13 and the intake ports 60 of the cylinders 10-1 to 10-4. The exhaust manifold 18 that connects the exhaust port 62 and the exhaust pipe 19 of each cylinder 10-1 to 10-4, and the exhaust pipe 19 that exhausts exhaust gas to the outside of the vehicle are provided.

  The intake pipe 13 is connected to the intake manifold 15, and the intake manifold 15 is connected to the intake ports 60 of the cylinders 10-1 to 10-4. 4 intake ports 60. The exhaust port 62 of each cylinder 10-1 to 10-4 is connected to the exhaust manifold 18, and the exhaust manifold 18 is connected to the exhaust pipe 19, so that the inside of the combustion chamber of each cylinder 10-1 to 10-4. The exhaust gas generated by the combustion of the air-fuel mixture is discharged from the exhaust port 62 of each cylinder 10-1 to 10-4 through the exhaust pipe 19 to the outside of the vehicle.

  The intake pipe 13 is provided with a throttle valve 12 for adjusting the flow rate of air introduced into the combustion chamber of each cylinder 10. The throttle valve 12 can be controlled by the ECU 90. The exhaust pipe 19 is provided with an air-fuel ratio sensor 36 and a catalyst 20. The air-fuel ratio sensor 36 detects an air-fuel ratio (A / F) that represents a ratio of the amount of air to the amount of fuel in the air-fuel mixture in the combustion chamber of each cylinder 10. The catalyst 20 is for redox purification of harmful substances in the exhaust gas. The detection value of the air-fuel ratio sensor 36 is input to the ECU 90. The ECU 90 feeds back the air-fuel ratio in each cylinder 10 by controlling the fuel injection amount of the injector 56 of each cylinder 10, the throttle valve 12, and the like so that the detection value of the air-fuel ratio sensor 36 becomes the target value. Control.

  The internal combustion engine 100 includes an EGR (exhaust gas recirculation) device 21 for returning a part of the exhaust gas flowing in the exhaust pipe 19 into the intake pipe 13 and supplying it to the combustion chamber of each cylinder 10. . The EGR device 21 includes an EGR pipe 22 that connects the intake pipe 13 and the exhaust pipe 19 and has an EGR passage 25 formed therein. The EGR pipe 22 is provided with an EGR cooler 23 for cooling the exhaust gas (EGR gas) flowing through the EGR passage 25 and an EGR valve 24. The EGR valve 24 can be controlled by the ECU 90. The ECU 90 adjusts the amount of EGR gas introduced into the intake manifold 15 by controlling the EGR valve 24.

  The internal combustion engine 100 is provided with a torque sensor 30 and a knock sensor 32 that detects the strength of knock generated in the internal combustion engine 100. Those detected values are input to the ECU 90.

  In the spark ignition type internal combustion engine 100 of the present embodiment, the ECU 90 operates at a high air-fuel ratio (A / F) by controlling the fuel injection amount of the injector 56 of each cylinder 10, the throttle valve 12, etc., or the ECU 90 Operation is performed at a high EGR rate by controlling the EGR valve 24 and the like. Thus, by operating at a high A / F or high EGR rate, the thermal efficiency can be increased and the fuel efficiency is improved. Moreover, generation | occurrence | production of harmful substances, such as NOx (nitrogen oxide), can be reduced.

  On the other hand, when the internal combustion engine 100 is operated at a high A / F or a high EGR rate, the combustion fluctuation increases and the torque fluctuation increases (the combustion fluctuation deteriorates and the torque fluctuation worsens). The deterioration of the combustion fluctuation can be suppressed by reducing the A / F or the EGR rate uniformly without specifying the factor. However, in that case, the thermal efficiency is lowered. In addition, the effect of reducing the generation of harmful substances is reduced. Therefore, the internal combustion engine 100 according to the present embodiment identifies a factor of deterioration of combustion fluctuation (torque fluctuation) and performs processing according to the factor to suppress the deterioration of combustion fluctuation without reducing thermal efficiency.

  There are two main reasons for the deterioration of combustion fluctuations. One factor is that combustion at high A / F and high EGR rate results in a decrease in combustion speed and a prolonged combustion period, resulting in variations in combustion in each cycle and an increase in combustion fluctuations. In order to increase the combustion speed, a high air flow such as a high swirl or a high tumble is performed by the air flow adjustment valve 58, but the combustion speed is still low and the combustion period may be prolonged. Another factor is that, as a result of the high air flow, the spark fluctuation of the spark plug 46 is blown off by the air flow (misfire), and the combustion fluctuation increases.

  When the spark of the spark plug 46 is blown off by the air flow and misfire occurs, unburned gas remains as a residual gas in the cylinder (combustion chamber 43) of the cylinder 10, so that in the next cycle Since the amount of fuel present in the cylinder increases and the amount of dilution with burned gas decreases, strong knocks are likely to occur.

  FIG. 3 is a diagram showing an example of in-cylinder pressure histories of a plurality of cycles at the time of combustion fluctuation deterioration due to occurrence of spark blowout (misfire). FIG. 3 shows the in-cylinder pressure at the crank angle from the compression stroke to the expansion stroke in one cycle. As shown in FIG. 3, in addition to a cycle in which misfire has occurred due to blow-off (cycle in which the in-cylinder pressure is significantly reduced near the expansion stroke), a cycle in which strong knock is occurring (in-cylinder pressure is There are cycles that are significantly higher). FIG. 4 is a diagram showing the change over time of the in-cylinder pressure in a plurality of cycles of FIG. FIG. 4 shows the in-cylinder pressure (cylinder pressure for one cycle) at the crank angle in a series of four strokes (intake, compression, expansion, and exhaust) for only eight cycles. As shown in FIG. 4, knocking occurs in the next cycle in which blowout (misfire) has occurred. Then, after repeating blowout and knocking several times, it returns to normal combustion. When blow-off occurs, the gas in the cylinder hardly burns and a part of the unburned gas remains in the cylinder until the next cycle, and the amount of fuel in the cylinder increases in the next cycle. In addition, since the burned gas is hardly included in the gas remaining in the cylinder until the next cycle, the amount of dilution gas is reduced. Therefore, a strong knock occurs in the next cycle.

  In this way, when the combustion fluctuation is worsened by the occurrence of spark blowout (misfire), a strong knock is generated. From this, when a strong knock occurs when the combustion fluctuation is worsening, it can be determined that the spark of the spark plug 46 has been blown out by the airflow. That is, when a strong knock occurs when the combustion fluctuation is worsening, it is possible to specify that the cause of the worsening of the combustion fluctuation is “misfire”.

  On the other hand, when the combustion period is prolonged, although the variation between cycles is large, a part of the gas in the cylinder 10 (combustion chamber 43) is combusted, so that the remaining fuel for the next cycle Because the amount is small and there is burnt gas, knocks such as blowout of sparks (misfire) are unlikely to occur. FIG. 5 is a diagram showing an example of a plurality of in-cylinder pressure histories at the time of deterioration of combustion fluctuation due to a prolonged combustion period. FIG. 5 shows the in-cylinder pressure at the crank angle from the compression stroke to the expansion stroke in one cycle. As shown in FIG. 5, when the combustion fluctuation worsens due to the prolonged combustion period, there is a difference in the pressure history in each cycle, but there is a cycle in which a complete misfire occurs (the in-cylinder pressure is significantly reduced near the expansion stroke. There is no cycle). Further, since there is little unburned gas remaining until the next cycle and there is much remaining burned gas, no knock is generated (there is no cycle in which the in-cylinder pressure is extremely high).

  Thus, when the combustion fluctuation is worsening due to the prolonged combustion period, strong knock does not occur. From this, it can be determined that the combustion period is prolonged if strong knocking does not occur when the combustion fluctuation is worsening. That is, when strong knock does not occur when the combustion fluctuation is worsening, it can be specified that the cause of the worsening of the combustion fluctuation is “prolongation of the combustion period”.

  The internal combustion engine 100 according to the present embodiment identifies a factor of deterioration of combustion fluctuation (torque fluctuation) depending on whether or not the strong knock described above has occurred, and performs processing according to the factor to thereby reduce the combustion fluctuation. Suppresses deterioration.

  Next, specific processing for suppressing deterioration of combustion fluctuation (torque fluctuation) in the internal combustion engine 100 of the present embodiment will be described. FIG. 6 is a flowchart showing a flow of control for suppressing deterioration of torque fluctuation in the internal combustion engine 100 of the present embodiment. The flow in FIG. 6 is executed by the ECU 90 (control means). The flow in FIG. 6 is executed at a timing when the accelerator opening, the rotational speed of the internal combustion engine 100, and the like are changed.

  As shown in FIG. 6, first, in S100, information such as the accelerator opening and the rotational speed of the internal combustion engine 100 is input to the ECU 90. In S102, the ECU 90 determines the ignition timing of the spark plug 46, the fuel injection amount of the injector 56, the intake valve 64, and the exhaust valve based on information such as the accelerator opening and the rotational speed of the internal combustion engine 100 input in S100. The internal combustion engine 100 is operated by adjusting the opening / closing timing of 66.

  Next, in S104, the ECU 90 checks whether the torque fluctuation limit of the internal combustion engine 100 is greater than a predetermined fluctuation amount (predetermined fluctuation amount). The “torque fluctuation limit state” can also be referred to as a “torque fluctuation worsening state”. Here, the means (torque fluctuation detecting means) for detecting the torque fluctuation is, for example, the torque sensor 30. The torque value of each cycle is acquired by the torque sensor 30, and the difference in torque value between cycles can be defined as “torque fluctuation (amount)” (for example, 10 torques of 10 consecutive cycles by the torque sensor 30). The torque value is acquired, and the difference between the minimum torque value and the maximum torque value among them can be defined as “torque fluctuation (amount)”. The in-cylinder pressure sensor 34 provided in the cylinder 10 acquires the in-cylinder pressure of each cycle, and estimates the difference in torque value between cycles from the difference in in-cylinder pressure between cycles. May be detected. That is, the in-cylinder pressure sensor 34 may be used as the torque fluctuation detection means. The ECU 90 compares the torque fluctuation (amount) with a predetermined fluctuation amount to confirm whether the torque fluctuation limit is reached.

  If the torque fluctuation is equal to or smaller than a predetermined fluctuation amount in S104, that is, if the torque fluctuation limit is not reached (S104: No), the flow of FIG. On the other hand, when the torque fluctuation is larger than the predetermined fluctuation amount, that is, when the torque fluctuation limit is reached (S104: Yes), the process proceeds to S106.

  In S106, the ECU 90 confirms whether or not a strong knock has been generated. The “strong knock occurrence state” can be simply referred to as a “knock occurrence state”. The means (knock detection means) for detecting the occurrence of knock is, for example, the knock sensor 32. Knock sensor 32 detects the strength of the knock and outputs the detected value to ECU 90. The ECU 90 determines that a strong knock has occurred when the input knock strength exceeds a predetermined strength. Here, the predetermined strength may be changed based on the rotational speed and / or torque of the internal combustion engine 100 or both of them. For example, a table in which a higher strength is set in advance as the rotational speed and torque are higher is prepared in advance, and the strength corresponding to the rotational speed and torque at the time of S106 is read from the table, and the “predetermined strength” Is used.

  If it is determined in step S106 that a strong knock has occurred (S106: Yes), the ECU 90 determines that the spark of the spark plug 46 has been blown out (misfired) (S108). That is, the cause of deterioration of torque fluctuation (combustion fluctuation) is identified as “misfire”. In S112, the ECU 90 performs blow-off suppression control that suppresses sparks from being blown off. “Blow-off suppression control” can also be referred to as “blow-off prevention control”. In the blow-off suppression control, for example, the ECU 90 controls the air flow adjustment valve 58 (a swirl control valve or a tumble control valve) so as to reduce the air flow in the cylinder 10. Further, when the hydraulic intake valve 64 is used in the internal combustion engine 100, the open / close period of the intake valve 64 can be changed. Therefore, the blow-off suppression control is performed when the ECU 90 closes the intake valve 64. The intake valve 64 may be controlled so as to lengthen the period of time. Thereby, the amount of airflow into the cylinder 10 per unit time can be reduced, and the airflow in the cylinder 10 can be reduced.

  On the other hand, when it is not in the state of strong knock occurrence in S106 (S106: No), the ECU 90 determines that the combustion period is prolonged (S110). That is, the cause of the deterioration of torque fluctuation (combustion fluctuation) is specified as “prolonging the combustion period”. In S114, the ECU 90 performs combustion period shortening control for shortening the combustion period. In the combustion period shortening control, for example, the ECU 90 controls the airflow adjustment valve 58 so as to increase the airflow in the cylinder 10. The combustion period shortening control may be one in which the ECU 90 controls the timing of the intake valve 64 so as to increase the gas temperature in the cylinder 10. Specifically, the ECU 90 performs control so that the timing for opening the intake valve 64 is advanced (the timing for introducing gas into the cylinder is advanced).

  After performing the blowout suppression control in S112 or the combustion period shortening control in S114, the process returns to S104 again to check whether the torque fluctuation of the internal combustion engine 100 is still in the torque fluctuation limit state. And when it is in the state of a torque fluctuation limit (S104: Yes), the process after S106 is performed again. That is, the blow-off suppression control (S112) or the combustion period shortening control (S114) is continued until the deterioration of torque fluctuation is suppressed.

  According to the spark ignition type internal combustion engine 100 of the present embodiment described above, whether the cause of torque fluctuation (combustion fluctuation) is “misfire” or “longer combustion period” depending on whether or not a strong knock has occurred. Can be easily identified. And since the process according to the factor is performed, the deterioration of a torque fluctuation can be suppressed exactly. Moreover, in order to suppress torque fluctuations (combustion fluctuations), the A / F is not lowered and the EGR rate is not lowered, so that the thermal efficiency is not lowered. In the internal combustion engine 100 of the present embodiment described above, it is determined whether or not “strong knock has occurred”, but control is performed simply by determining whether or not “knock has occurred”. It may be a thing.

  In the internal combustion engine 100 according to the embodiment described above, the knock sensor 32 as a whole checks the presence or absence of strong knocking in the plurality of cylinders 10 collectively, and performs blowout suppression control in the plurality of cylinders 10 collectively. It was. However, it is also possible to check whether or not a strong knock has occurred for each cylinder 10 and perform blow-off suppression control for each cylinder 10. FIG. 7 is a flowchart showing a flow of control for suppressing deterioration of torque fluctuation in that case. Of the steps in the flow of FIG. 7, the steps different from the steps of the flow of FIG. 6 are S206, S208, and S212. Therefore, those steps will be mainly described, and description of the other steps will be omitted. Or, it will not be described in detail.

  As shown in FIG. 7, in S206, the ECU 90 confirms whether a strong knock has occurred for each cylinder 10 (whether a strong knock has occurred). The means (knock detection means) for detecting the occurrence of knocking in S206 is, for example, an in-cylinder pressure sensor 34 provided for each cylinder 10. The in-cylinder pressure sensor 34 of each cylinder 10 detects the pressure in the cylinder 10 and outputs the detected value to the ECU 90. The ECU 90 extracts a high-frequency pressure vibration component from the input pressure value of each cylinder 10 using a high-pass filter or the like. If the high-frequency pressure vibration component exceeds a predetermined value, it is determined that a strong knock has occurred. The ECU 90 performs this for each pressure of each cylinder 10. Here, the predetermined value may be changed based on the rotational speed or torque of the internal combustion engine 100, or both of them. For example, a table in which a higher value is set in advance as the rotation speed and torque increase is prepared in advance, and values corresponding to the rotation speed and torque at the time of S206 are read from the table, and the values are set to “predetermined values”. Is used.

  In S206, when there is even one cylinder 10 in which strong knock has occurred (S206: Yes), the process proceeds to S208. In S208, the ECU 90 determines that the spark of the spark plug 46 has blown out (misfired) in the cylinder 10 in the strong knock occurrence state. In S212, the ECU 90 performs blow-off suppression control that suppresses the blow-off of the spark only for the cylinder 10 in a state where a strong knock has occurred. That is, for example, the ECU 90 controls the airflow adjustment valve 58 of the cylinder 10 in which a strong knock is generated so as to reduce the airflow in the cylinder 10. On the other hand, when there is no strong knock occurrence cylinder 10 (S206: No), the process proceeds to S210. In S210, the ECU 90 determines that the combustion period has become longer, and in S214, the ECU 90 performs combustion period shortening control to shorten the combustion period.

  As described above, if the presence or absence of strong knocking is detected for each cylinder 10 using the in-cylinder pressure sensor 34, it is possible to determine whether misfire has occurred for each cylinder 10, and for the cylinder 10 in which misfire has occurred. Only blowout suppression control can be performed. When the presence / absence of misfire is determined based on the rotational speed fluctuation amount of the internal combustion engine as in Patent Documents 1 and 2, which are the prior art, there is a problem in the misfire detection accuracy depending on the operating state of the internal combustion engine. It cannot be determined whether a misfire has occurred in the cylinder, and it is impossible to control each cylinder. However, according to the embodiment described above, it is possible to accurately detect misfire, to specify the presence or absence of misfire for each cylinder 10, and to control for each cylinder 10.

  In the internal combustion engine 100 of the embodiment described above, the cause of torque fluctuation is specified by the presence or absence of strong knock. However, as can be seen from FIG. 3 and FIG. 4, the maximum pressure in the cylinder 10 becomes high when knocking occurs, and therefore the cause of torque fluctuation is specified using the value of the maximum pressure instead of whether knocking occurs or not. May be. FIG. 8 is a flowchart showing a flow of control for suppressing deterioration of torque fluctuation in that case. Of the steps in the flow of FIG. 8, the difference from the steps of the flow of FIG. 6 is S306. Therefore, the steps will be mainly described, and description of the other steps will be omitted or detailed. I do not explain.

  As shown in FIG. 8, in S306, the ECU 90 confirms whether or not the maximum pressure in the cylinder 10 is in a high pressure state exceeding a predetermined pressure (specified value). The pressure in the cylinder 10 is acquired by, for example, the in-cylinder pressure sensor 34 (the pressure detecting means is the in-cylinder pressure sensor 34). The maximum pressure in the cylinder 10 can be, for example, the maximum pressure value in the cylinder 10 in 10 consecutive cycles. When there are a plurality of cylinders 10, the maximum value among the maximum pressures for each cylinder 10 may be used as the maximum pressure in S306.

  If it is determined in S306 that the maximum pressure in the cylinder 10 exceeds the predetermined pressure (S306: Yes), the process proceeds to S308. In S308, the ECU 90 determines that the spark of the spark plug 46 has been blown off (misfired), and in S312, the ECU 90 performs blow-off suppression control. On the other hand, in S306, when the maximum pressure in the cylinder 10 does not exceed a predetermined pressure (not in a high pressure state) (S306: No), the process proceeds to S310. In S310, the ECU 90 determines that the combustion period has become longer, and in S314, the ECU 90 performs combustion period shortening control.

  In S306, the ECU 90 is in a high pressure state in which the maximum pressure in the cylinder 10 exceeds a predetermined pressure for each cylinder 10 using the in-cylinder pressure sensor 34 provided for each cylinder 10. You may check. In S308, the ECU 90 determines that the spark of the spark plug 46 has blown out (misfired) in the cylinder 10 in the high pressure state, and in S312, the ECU 90 determines that only the cylinder 10 in the high pressure state. In contrast, blow-off suppression control may be performed.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to such embodiment at all, Of course, in the range which does not deviate from the summary of this invention, it can implement with a various form. .

10, 10-1, 10-2, 10-3, 10-4 cylinder, 12 throttle valve, 13 intake pipe, 15 intake manifold, 18 exhaust manifold, 19 exhaust pipe, 20 catalyst, 21 EGR device, 22 EGR pipe, 23 EGR cooler, 24 EGR valve, 25 EGR passage, 30 torque sensor, 32 knock sensor, 34 in-cylinder pressure sensor, 36 air-fuel ratio sensor, 40 cylinder block, 41 cylinder head, 42 cylinder, 43 combustion chamber, 46 spark plug, 50 Piston, 51 Connecting rod, 56 Injector, 58 Air flow regulating valve, 60 Intake port, 62 Exhaust port, 64 Intake valve, 66 Exhaust valve, 90 ECU, 100 Spark ignition internal combustion engine.

Claims (8)

A spark ignition internal combustion engine,
Torque fluctuation detecting means for detecting torque fluctuation in the internal combustion engine;
Knock detecting means for detecting occurrence of knock in the internal combustion engine;
Control means for controlling the torque fluctuation in the internal combustion engine,
The control means includes
Blow-out suppression that suppresses the blow-off of the spark of the internal combustion engine when the torque fluctuation is in a state of worsening torque fluctuation that is greater than a predetermined fluctuation amount and is in a knock-generating state in which the knock has occurred. Control
A spark ignition type internal combustion engine that performs combustion period shortening control for shortening a combustion period of the internal combustion engine when the torque fluctuation is in a deteriorated state and is not in the knocking state. The spark ignition internal combustion engine according to claim 1,
The knock detection means detects the occurrence of the knock for each cylinder,
The spark-ignition internal combustion engine, wherein the control means performs the blow-out suppression control in accordance with the knock occurrence state for each cylinder. The spark ignition internal combustion engine according to claim 1 or 2,
The knock detection means is an in-cylinder pressure sensor that detects a pressure in the cylinder,
The control means, when the high-frequency pressure vibration component extracted from the pressure in the cylinder exceeds a predetermined value according to at least one of the rotational speed and torque of the internal combustion engine, A spark ignition type internal combustion engine that judges that a knock has occurred. The spark ignition internal combustion engine according to claim 1,
The knock detection means is a knock sensor that detects the strength of the knock,
The spark-ignition internal combustion engine determines that the knock has occurred when the knock exceeds a predetermined strength according to at least one of the rotational speed and torque of the internal combustion engine. organ. The spark ignition internal combustion engine according to any one of claims 1 to 4,
The spark-ignition internal combustion engine, wherein the control means performs the blow-off suppression control by controlling an airflow adjustment valve so as to reduce an airflow in the cylinder. The spark ignition internal combustion engine according to any one of claims 1 to 5,
The spark ignition type internal combustion engine, wherein the control means performs the combustion period shortening control by controlling an airflow adjustment valve so as to increase the airflow in the cylinder. The spark ignition internal combustion engine according to any one of claims 1 to 5,
The spark ignition type internal combustion engine, wherein the control means performs the combustion period shortening control by controlling a timing of an intake valve so as to increase a gas temperature in a cylinder. A spark ignition internal combustion engine,
Torque fluctuation detecting means for detecting torque fluctuation in the internal combustion engine;
Pressure detecting means for detecting a pressure in a cylinder of the internal combustion engine;
Control means for controlling the torque fluctuation in the internal combustion engine,
The control means includes
When the torque fluctuation is in a torque fluctuation worsening state larger than a predetermined fluctuation amount, and the maximum pressure in the cylinder in the internal combustion engine is a high pressure state exceeding a predetermined pressure, the internal combustion engine Blow-out suppression control that suppresses the sparks of the engine from blowing out,
A spark ignition internal combustion engine that performs combustion period shortening control for shortening the combustion period of the internal combustion engine when the torque fluctuation is in a deteriorated state and not in the high pressure state.