JP2014043812A - Control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control device for an internal combustion engine which can efficiently perform a pre-ignition suppression control for suppressing the occurrence of a pre-ignition.SOLUTION: The control device for an internal combustion engine performs a predetermined pre-ignition suppression control for suppressing the occurrence of the pre-ignition when a pre-ignition is detected. The pre-ignition suppression control is performed, only when the driving condition of an internal combustion engine reaches such a driving condition that a large pre-ignition in which the maximum cylinder pressure becomes a predetermined value or more possibly occurs when the occurrence frequency of a small pre-ignition in which the maximum cylinder pressure is lower than the predetermined value, reaches a predetermined frequency.

Description

  The present invention relates to an internal combustion engine control apparatus, and more particularly, to an internal combustion engine control apparatus suitable for predicting and preventing the occurrence of sudden pre-ignition with heavy knock.

  Conventionally, for example, Patent Document 1 discloses a control device for an internal combustion engine. In this conventional control device, the pre-ignition is generated when the combustion ratio at the predetermined crank angle is larger than the reference combustion ratio when the normal combustion state is obtained (that is, when there is a possibility of the occurrence of pre-ignition). An increase in the fuel injection amount is performed as a plague suppression control for suppression.

JP-A-9-273436

  There are large and small pre-ignitions. Even so, if the pre-ignition suppression control is always executed under engine operating conditions where there is a possibility of occurrence of pre-ignition regardless of the magnitude, there is a possibility that the pre-ignition suppression control may be executed unnecessarily. is there. In addition, if the pre-ignition suppression control is accompanied by a change in the operating state of the internal combustion engine, the unnecessary pre-ignition suppression control may lead to a decrease in engine performance.

  The present invention was made to solve the above-described problems, and provides a control device for an internal combustion engine that is capable of efficiently performing pre-ignition suppression control for suppressing the occurrence of pre-ignition. Objective.

A first invention is a control device for an internal combustion engine,
Pre-ignition detection means for detecting pre-ignition;
Pre-ignition control execution means for executing predetermined pre-ignition suppression control for suppressing occurrence of pre-ignition when pre-ignition is detected;
With
When the occurrence frequency of a small pre-ignition whose maximum in-cylinder pressure is lower than a predetermined value has reached a predetermined frequency, the pre-ignition suppression control execution means has a large operating condition of the internal combustion engine such that the maximum in-cylinder pressure is greater than or equal to the predetermined value. The pre-ignition suppression control is executed only when an operating condition that may cause pre-ignition is reached.

The second invention is the first invention, wherein
The pre-ignition suppression control is injection of liquid into the combustion chamber,
The liquid injection is performed during a period in which the in-cylinder volume is smaller than a predetermined value in the exhaust stroke, the intake stroke, or both strokes.

The third invention is the second invention, wherein
The liquid is injected separately from the fuel injection that is performed for the internal combustion engine to generate torque during a period in which the cylinder volume is smaller than the predetermined value in the exhaust stroke, the intake stroke, or both strokes. It is an additional fuel injection.

Moreover, 4th invention is 2nd invention.
In the liquid injection, the injection period of the fuel injection performed for the internal combustion engine to generate torque is extended to the advance side so that the in-cylinder volume overlaps the period smaller than the predetermined value in the intake stroke. The fuel injection is carried out in (1).

Moreover, 5th invention is based on any one of 1st-4th invention,
The internal combustion engine is a supercharged internal combustion engine,
The pre-ignition suppression control is characterized in that at the time of supercharging, at least one of the closing timing of the exhaust valve and the opening timing of the intake valve is controlled so that scavenging of the residual gas in the combustion chamber is promoted.

  According to the first aspect of the invention, the pre-ignition suppression control is executed only when it can be determined that there is a high possibility that a large pre-ignition will occur due to the high occurrence frequency of the small pre-ignition. For this reason, it becomes possible to prevent the pre-ignition suppression control from being performed unnecessarily. For this reason, it becomes possible to efficiently implement the pre-ignition suppression control. Moreover, even if the pre-ignition suppression control changes the engine operating state (for example, fuel injection in the following third or fourth invention), the engine performance (for example, , Fuel consumption performance) can be reduced.

  According to the second to fourth inventions, by injecting the liquid when the in-cylinder volume is small, the fuel is surely sprayed to the in-cylinder floating deposit or the like that causes large pre-ignition. Can be cooled. Thereby, generation | occurrence | production of a large preignition can be suppressed reliably.

  According to the fifth aspect, in-cylinder floating deposits or the like can be prevented from remaining after the next cycle more reliably. This makes it possible to more reliably suppress the occurrence of large pre-ignition due to the presence of in-cylinder floating deposits remaining after the next cycle.

It is a figure for demonstrating the system configuration | structure of Embodiment 1 of this invention. It is a figure for demonstrating the generation | occurrence | production mechanism of the pre-ignition resulting from the deposit which exists in a pipe | tube. It is a figure which shows an example of the generation | occurrence | production condition of the pre-ignition within the predetermined time on the same engine operating conditions. It is a flowchart of the routine performed in Embodiment 1 of the present invention. It is a figure for demonstrating the determination method of the preignition using in-cylinder pressure. It is a figure for demonstrating the other determination method of the pre-ignition in this invention. It is a figure for demonstrating preg suppression control in Embodiment 2 of this invention. It is a flowchart of the routine performed in Embodiment 2 of this invention.

Embodiment 1 FIG.
[Description of system configuration]
FIG. 1 is a diagram for explaining a system configuration according to the first embodiment of the present invention.
The system shown in FIG. 1 includes a spark ignition internal combustion engine (a gasoline engine as an example) 10 with a turbocharger 24. A piston 12 is provided in each cylinder of the internal combustion engine 10. A combustion chamber 14 is formed on the top side of the piston 12 in each cylinder. An intake passage 16 and an exhaust passage 18 communicate with the combustion chamber 14.

  An air cleaner 20 is attached to the inlet of the intake passage 16. The air cleaner 20 is provided with an air flow meter 22 that outputs a signal corresponding to the flow rate of air taken into the intake passage 16. A compressor 24 a of the turbocharger 24 is disposed in the intake passage 16 on the downstream side of the air flow meter 22. Further, an electronically controlled throttle valve 26 is provided in the intake passage 16 on the downstream side of the compressor 24a. A turbine 24 b of the turbocharger 24 is disposed in the exhaust passage 18.

  Each cylinder is provided with a fuel injection valve 28 for directly injecting fuel into the combustion chamber 14 (inside the cylinder). Each cylinder is provided with a spark plug 30 for igniting the air-fuel mixture in the combustion chamber 14. The spark plug 30 is connected to the ignition coil 32. Further, each cylinder is provided with an intake valve 34 and an exhaust valve 36 for opening and closing the intake port of the intake passage 16 and the exhaust port of the exhaust passage 18.

  The intake valve 34 and the exhaust valve 36 are driven by an intake variable valve mechanism 38 and an exhaust variable valve mechanism 40, respectively. The variable valve mechanisms 38 and 40 can change the opening / closing timing of the intake valve 34 or the exhaust valve 36 within a predetermined range by changing the rotation phase of each camshaft (not shown) with respect to the rotation phase of the crankshaft 42. Including a variable valve timing mechanism. According to such variable valve mechanisms 38 and 40, it is possible to adjust the valve overlap period in which the valve opening period of the exhaust valve 36 and the valve opening period of the intake valve 34 overlap. A crank angle sensor 44 for detecting the crank angle is disposed in the vicinity of the crankshaft 42.

  The system shown in FIG. 1 includes an ECU (Electronic Control Unit) 46. In addition to the air flow meter 22 and the crank angle sensor 44 described above, an in-cylinder pressure sensor 48 for detecting in-cylinder pressure, an intake cam angle that is a rotation angle of the intake cam shaft and the exhaust cam shaft, Various sensors for detecting the operating state and combustion state of the internal combustion engine 10 such as an intake cam angle sensor 50 and an exhaust cam angle sensor 52 for detecting the exhaust cam angle are connected. Also, various actuators for controlling the operation of the internal combustion engine 10 such as the throttle valve 26, the fuel injection valve 28, the ignition coil 32, and the variable valve mechanisms 38 and 40 are connected to the output portion of the ECU 46. Yes.

[Control for Preignition Suppression in Embodiment 1]
FIG. 2 is a diagram for explaining a pre-ignition generation mechanism caused by deposits existing in the cylinder.
The low-rotation and high-load region of the internal combustion engine 10 is a region where a phenomenon (pre-ignition) in which the air-fuel mixture self-ignites before the normal ignition timing can occur. As one of the causes of the occurrence of such pre-ignition, there is a possibility that high-temperature solid matter floating in the cylinder such as red-hot deposits in the combustion chamber 14 and unburned oil droplets may be an ignition source. I understood that. For example, as shown in FIG. 2A, the deposit attached to the inner wall surface of the cylinder may be peeled off due to the occurrence of knocking or pre-ignition. If the peeled deposit floats in the cylinder while burning and remains until the next cycle and thereafter, the deposit remaining in the cylinder becomes an ignition source as shown in FIG. It became clear that it becomes one of the generation factors. And unlike the preignition that occurs with the hot surface near the spark plug as the ignition source, the preignition due to such a generation factor occurs suddenly regardless of the coolant temperature or the combustion chamber wall temperature. is there.

FIG. 3 is a diagram illustrating an example of a pre-ignition occurrence state within a predetermined time under the same engine operating condition.
In FIG. 3, the prescribed value of the maximum in-cylinder pressure Pmax used in the present embodiment is 9.5 MPa as an example. In the present embodiment, a pre-ignition in which the maximum in-cylinder pressure Pmax is equal to or greater than the specified value is referred to as “large pre-ignition” (hereinafter simply referred to as “large pre-ignition”), and the maximum in-cylinder pressure Pmax is lower than the specified value. The pre-ignition is referred to as “small pre-ignition” (hereinafter simply referred to as “small pre-ignition”). More specifically, the large plague is a large preignition with heavy knock, and the small pregue is a relatively small preignition without heavy knock.

  In the test results shown in FIG. 3, a large plague in which the maximum in-cylinder pressure Pmax is greater than or equal to the specified value occurs once during the test time, while a small pre-ignition in which the maximum in-cylinder pressure Pmax is lower than the specified value is in the same test time. The number of occurrences is greater than the number of occurrences of large plague. Although not shown here, it has been confirmed that there are operating conditions in which only the small pre-ignition is present in the operating conditions in which the supercharging pressure is lower than the engine operating conditions of FIG.

  As described above, it has been found that, under the engine operating conditions in which a large plague can occur, the occurrence of small plague is also mixed, and the occurrence frequency of the small plague is higher than that of the large plague. For this reason, if the occurrence frequency of small plows is high under the engine operating conditions where large prags can occur, deposits etc. that are peeled off from the cylinder inner wall surface due to the occurrence of small plags and floating in the cylinder, etc. It is considered that the possibility of suddenly generating a large plague becomes high as an ignition source.

  As described above, the pre-ignition includes a large plague having a large degree and a small preage having a small degree. Nevertheless, regardless of the magnitude, pre-ignition suppression control (for example, increasing the fuel injection amount) is always performed to suppress pre-ignition under engine operating conditions where pre-ignition may occur. If this is the case, there is a possibility that pre-ignition suppression control will be performed unnecessarily.

  Therefore, in the present embodiment, when the frequency of occurrence of the small plague reaches a predetermined frequency, the operating condition of the internal combustion engine 10 is an operating condition in which a large plague may occur (for example, the operating condition shown in FIG. 3). Only when it becomes, predetermined pre-gage suppression control is executed.

  FIG. 4 is a flowchart showing a control routine executed by the ECU 46 in order to realize characteristic control in the first embodiment of the present invention. This routine is repeatedly executed every predetermined control cycle.

  In the routine shown in FIG. 4, first, it is determined whether or not a below-described small preg frequency determination flag is ON (step 100). As a result, if the small prag frequency determination flag is not ON, the process proceeds to step 102, whereas if the small preg frequency determination flag is ON, the process proceeds to step 114.

  In step 102, it is determined whether or not preignition has occurred for each cylinder of the internal combustion engine 10 for each cycle. FIG. 5 is a diagram for explaining a pre-ignition determination method using in-cylinder pressure. More specifically, the horizontal axis in FIG. 5 is the crank angle, and the vertical axis is the in-cylinder pressure, and shows examples of in-cylinder pressure curves during normal combustion and preignition generation combustion.

  As shown in FIG. 5, when pre-ignition occurs, the in-cylinder pressure at the crank angle position at the ignition timing becomes higher than during normal combustion. Therefore, in the present embodiment, it is determined whether or not pre-ignition has occurred based on whether or not the rise of the in-cylinder pressure at the crank angle position of the ignition timing is earlier than during normal combustion. Specifically, for example, the in-cylinder pressure detected by the in-cylinder pressure sensor 48 at the crank angle position at the ignition timing is a predetermined value than the in-cylinder pressure during normal combustion under the same operating conditions (a value obtained in advance through experiments or the like). If it is greater than the above, it can be determined that the pre-ignition has occurred, with the rise of the in-cylinder pressure at the crank angle position of the ignition timing being earlier than during normal combustion.

  According to this determination method, it is possible to reliably detect the occurrence of pre-ignition. In place of the determination using the in-cylinder pressure itself detected by the in-cylinder pressure sensor 48, the heat generation rate or the combustion mass ratio (already out of the injected fuel) is determined according to a known relational expression using the detected in-cylinder pressure. The ratio of fuel applied to combustion) may be calculated, and whether or not heat generation has started at the crank angle position of the ignition timing may be used as a pre-ignition determination index. Furthermore, the determination of pre-ignition described above is not limited to the crank angle position at the ignition timing, and a crank angle position that is advanced by a predetermined value may be used.

  If it is determined in step 102 that pre-ignition has occurred, it is determined whether or not the maximum in-cylinder pressure Pmax of the current detection target cycle is greater than or equal to a specified value (step 104). As a result, when the determination of step 104 is established, that is, when it can be determined that the pre-ignition determined to have occurred this time is a large pre-ignition, the operating condition in which the current large pre-ignition has occurred is stored in the ECU 46. (Step 106).

  On the other hand, if the determination in step 104 is not established, that is, if it can be determined that the pre-ignition determined to have occurred this time is a small pre-ignition, then the cumulative occurrence of small pre-counts counted for a predetermined determination period. The number of times is incremented by 1 and stored in the ECU 46 (step 108).

  Next, it is determined whether or not the cumulative number of occurrences of small prags in the predetermined determination period has reached a predetermined number, that is, whether or not the occurrence frequency of small plags has reached a predetermined frequency (step 110). As a result, when the determination at step 110 is not established, the processing after step 102 is repeatedly executed. On the other hand, if the determination in step 110 is established, the pre-figure determination loop ends and the small pre-freque frequency determination flag is turned on (step 112). As an example, the small pre-ignition frequency determination flag may be continuously turned on while the operation is continued after being turned on, and turned off when the operation of the internal combustion engine 10 is stopped.

  In step 114, it is determined whether or not the operating condition stored by the processing in step 106 that may cause a large pre-ignition has arrived (step 114). As a result, when the above operating condition has arrived, pre-ignition suppression control (for example, outputting a fuel increase signal to the fuel injection valve 28) is executed (step 116).

  According to the routine shown in FIG. 4 described above, when a pre-ignition is detected, the magnitude (degree) of the pre-ignition is determined, the operating condition in which the large pre-ignition has occurred, and the cumulative number of occurrences of the small pre-ignition. Learning control is executed. When the occurrence frequency of the small plag reaches a predetermined frequency (after reaching), only when the operation condition of the internal combustion engine 10 is an operation condition that may cause a large pre-ignition, the suppression of pragging is performed. Control is executed. Thereby, only when it can be determined that there is a high possibility that a large prag is generated due to the high occurrence frequency of the small prag, the plag suppression control is executed. For this reason, it becomes possible to prevent the pre-ignition suppression control from being performed unnecessarily. Further, even if the pre-ignition suppression control changes the engine operating state (for example, an increase in the fuel injection amount), the engine performance (for example, fuel efficiency) decreases as the pre-ignition suppression control is performed. Opportunities can be reduced.

  By the way, in Embodiment 1 mentioned above, after storing the operating conditions in which the large prag is actually generated, if the occurrence frequency of the small prag reaches a predetermined frequency, the large prag can be generated. The operation condition memorized during operation is referred to as a characteristic operation condition. However, in the present invention, the “operating condition that may cause a large preignition” is not limited to the operating condition acquired during driving based on the actual detection result of the large preignition, and is estimated and stored in advance. The operating conditions that have been set may be used.

  In the above-described first embodiment, the pre-ignition determination method using the in-cylinder pressure has been described as an example with reference to FIG. However, the preignition detection (determination) method in the present invention is not limited to the above, and may be as shown below, for example.

  FIG. 6 is a diagram for explaining another determination method of pre-ignition according to the present invention. The determination method described with reference to FIG. 6 makes it possible to detect post-ignition in addition to pre-ignition at the earliest possible stage. Note that, as shown in FIG. 6A, post-ignition is abnormal combustion that occurs at a timing later than the ignition timing.

  In this determination method, the in-cylinder pressure curve during normal combustion (see FIG. 6B) is set as a reference curve for each engine operating condition based on various parameters such as engine speed, intake air flow rate, air-fuel ratio, ignition timing, and EGR amount. Remember as. Then, during operation of the internal combustion engine 10, an in-cylinder pressure curve during normal combustion corresponding to the current engine operating conditions is estimated and acquired based on the various parameters described above. As the in-cylinder pressure curve (reference) at the time of normal combustion, the in-cylinder pressure curve when abnormal combustion has not occurred in the cycle immediately before the same cylinder (or another cylinder) may be stored and used. May be.

  In this determination method, the in-cylinder pressure detected by the in-cylinder pressure sensor 48 in the detection target cycle is compared with the in-cylinder pressure curve obtained during normal combustion as described above. Specifically, as shown in FIG. 6B, when a pressure difference ΔP1 of the in-cylinder pressure with respect to the in-cylinder pressure at the time of normal combustion becomes equal to or greater than a predetermined value at a certain time T1, it is determined that preignition has occurred. Then, the pre-ignition determination process is terminated.

  Further, according to this determination method, it is possible to determine whether or not post-ignition has occurred by the following processing. Specifically, when the pressure difference ΔP1 is smaller than the specified value, the pressure difference ΔP2 that is the difference between the in-cylinder pressure at time T2 and the in-cylinder pressure at time T1 is calculated. If the calculated pressure difference P2 is greater than or equal to a specified value, it is determined that post-ignition has occurred. However, when the occurrence of knocking is separately detected using a knock sensor (not shown) or the like, it is preferable not to perform post-ignition determination.

  The above times T1 and T2 are values determined on the basis of normal combustion. For example, the time T1 is a crank angle position where the combustion mass ratio is 5%, and the time T2 is a crank where the combustion mass ratio is 30%. It can be an angular position. Further, the prescribed values of the pressure differences ΔP1 and ΔP2 are values determined based on normal combustion, but multiply the prescribed values by taking into account the fluctuations of combustion and the estimation error of the in-cylinder pressure curve (reference). You may do it.

  By using the above determination method, the pre-ignition and the post-ignition can be directly detected using the detected value of the in-cylinder pressure immediately after the rise of the in-cylinder pressure. For this reason, the burden of determination processing can be reduced, and early determination can be performed at a stage where the detection target cycle is not completed.

  Further, during the operation of the internal combustion engine 10, the following additional fuel injection may be performed. That is, in this additional fuel injection, the rising timing (crank angle position) of the in-cylinder pressure due to pre-ignition detected using the pre-ignition determination method shown in FIG. 5 or FIG. 6 reaches the maximum in-cylinder pressure Pmax. This is performed only when the timing (crank angle position) is an advance timing with respect to a predetermined value.

  In order to perform this additional fuel injection, the time (crank angle position) at which the in-cylinder pressure reaches the maximum in-cylinder pressure Pmax when pre-ignition occurs is stored in advance in the ECU 46 as a value corresponding to the engine operating conditions. . The specified value is required from the engine speed and the responsiveness of the fuel injection valve 28 (specifically, from when the ECU 46 determines to perform fuel injection until the fuel injection is actually executed by the fuel injection valve 28). Time). Even if the responsiveness (the above time) of the fuel injection valve 28 is the same, if the engine speed is high, the crank angle base causes the crank to elapse from the determination of fuel injection by the ECU 46 until the actual fuel injection is executed. The corner period is longer. Therefore, the specified value is determined as a crank angle base value based on the response (the time) of the fuel injection valve 28 and the engine speed.

  When the rise of the in-cylinder pressure due to pre-ignition is detected, the ECU 46 determines that the crank angle position at this time is a position more advanced than the specified value with respect to the crank angle position at which the in-cylinder pressure reaches the maximum in-cylinder pressure Pmax. It is determined whether or not. If this determination is true, that is, at the timing when the rising of the in-cylinder pressure due to pre-ignition is detected, it can be determined that the fuel can be injected into the combustion chamber 14 until the in-cylinder pressure reaches the maximum in-cylinder pressure Pmax. In this case, the additional fuel injection is promptly executed so as to interrupt the normal control fuel injection. According to such additional fuel injection, the in-cylinder gas can be cooled. As a result, heavy knock that induces pre-ignition can be avoided, and an excessive increase in in-cylinder pressure can be prevented.

  In the first embodiment described above, the “pre-ignition detection means” in the first invention is realized by the ECU 46 executing the process of step 102, and the ECU 46 determines that the determination of step 114 is satisfied. In addition, by executing the process of step 116, the “pre-gage suppression control execution means” in the first aspect of the present invention is realized.

Embodiment 2. FIG.
Next, a second embodiment of the present invention will be described with reference to FIG. 7 and FIG.

[Pleig Suppression Control in Embodiment 2]
As an example of the system configuration of the present embodiment, the hardware configuration shown in FIG. 1 is used. The present embodiment is characterized in that control by the routine shown in FIG. 8 described later is performed as the pre-ignition suppression control when the ECU 46 executes the routine shown in FIG.

FIG. 7 is a diagram for explaining preg suppression control according to Embodiment 2 of the present invention.
As described above with reference to FIG. 2, high-temperature solids (deposits, unburned oil droplets, etc.) floating in the cylinder remain in the next cycle while maintaining high heat, and become an ignition source. It turns out that it becomes one of the generation factors of pre-ignition.

  Therefore, in the present embodiment, when performing the plague suppression control in the operating condition in which the large plague may occur when the occurrence frequency of the small plague reaches a predetermined frequency by the control of the first embodiment described above, Both of the prag suppression control shown in FIG. 7 (A) and FIG. 7 (B) are carried out over a predetermined cycle (for example, 100 cycles).

  First, in the pre-ignition suppression control shown in FIG. 7 (A), the liquid in the combustion chamber 14 (in this embodiment, in the exhaust stroke, the intake stroke, or both strokes) during a period in which the cylinder volume is smaller than a predetermined value. Fuel). Specific embodiments of the liquid jet include the following.

  In the internal combustion engine 10 including the fuel injection valve 28 that directly injects fuel into the cylinder, the injection timing of normal fuel injection for generating the torque required for the internal combustion engine 10 is an intake stroke or a compression stroke. For this reason, when the fuel injection as the liquid injection is performed during a period in which the in-cylinder volume is smaller than the predetermined value in the “exhaust stroke”, the liquid injection is an additional fuel injection with respect to the normal fuel injection. . On the other hand, when the fuel injection as the liquid injection is performed during a period in which the cylinder volume is smaller than the predetermined value in the “intake stroke”, the liquid injection is an additional fuel injection independent of the normal fuel injection. It may be implemented by expanding the injection period of normal fuel injection to the advance side so that a part of the in-cylinder volume is smaller than the predetermined value in the “intake stroke”. It may be. Furthermore, these liquid jets for the exhaust stroke and the intake stroke may be combined appropriately.

  By performing the above-described liquid injection during a period in the vicinity of the exhaust top dead center where the in-cylinder volume is smaller than a predetermined value, the fuel can be reliably blown to the deposit or the like floating in the combustion chamber 14, and the floating deposit It is possible to take away the ability as an ignition source such as a floating deposit.

  The pre-ignition suppression control shown in FIG. 7B controls at least one of the closing timing of the exhaust valve 36 and the opening timing of the intake valve 34 so that scavenging of the residual gas in the combustion chamber 14 is promoted. . Specifically, under the situation where the valve overlap period has already been set, the control for expanding the valve overlap period using the variable valve mechanisms 38 and 40 is applicable, and the valve overlap period is not set. Under circumstances, the control for setting the valve overlap period is applicable.

  The internal combustion engine 10 is an internal combustion engine with a supercharger, and an operation region in which the occurrence of pre-ignition is a concern is a supercharging region. In such a supercharging region, if the valve overlap period is expanded, the intake pressure is higher than the exhaust pressure. Therefore, as shown in FIG. It is possible to scavenge floating deposits and the like remaining in the interior.

  FIG. 8 is a flowchart showing a control routine executed by the ECU 46 in order to realize the characteristic pre-gage suppression control in the second embodiment of the present invention. This routine is executed in place of the processing of step 116 in the routine shown in FIG.

  In the routine shown in FIG. 8, first, fuel injection performed during the period near the exhaust top dead center is executed as the above-described liquid injection (step 200). This fuel injection is executed over a predetermined number of cycles (for example, 100 cycles).

  Next, in order to extend the valve overlap period, an advance angle of the opening timing of the intake valve 34 (step 202) and a delay angle of the closing timing of the exhaust valve 36 (step 204) are respectively executed. These intake / exhaust valve timing changes are also executed over a predetermined number of cycles (for example, 100 cycles). In this case, in order to extend the valve overlap period, only one of the processes in steps 202 and 204 may be performed.

  According to the routine shown in FIG. 8 described above, the liquid ejection is performed when the in-cylinder volume is small when an operating condition that may cause a large plague has arrived in a situation where the occurrence frequency of the small plague is high. The fuel injection is executed. As a result, the in-cylinder floating deposit or the like, which is a cause of occurrence of a large plague, can be reliably cooled by the fuel. Thereby, generation | occurrence | production of a large plague can be suppressed reliably. In addition, since the opportunity for performing such liquid injection is limited to the time when the above operating condition arrives in a situation where the occurrence frequency of small pre-ignition is high, fuel consumption deterioration due to fuel injection as the liquid injection is minimized. be able to.

  Furthermore, according to the above routine, scavenging of the residual gas in the combustion chamber 14 is promoted when an operating condition that may cause a large plague in a situation where the occurrence frequency of the small plague is high is reached. The valve overlap period is extended. As a result, in-cylinder floating deposits and the like can be more reliably prevented from remaining after the next cycle. Such scavenging can more reliably suppress the occurrence of large plague. Further, since the expansion of the valve overlap period more than necessary is limited to the time when the above operating condition arrives under the condition that the frequency of occurrence of small pre-ignition is high, the fresh air to the exhaust passage 18 due to excessive scavenging Blow-through can be minimized.

  By the way, in Embodiment 2 mentioned above, the liquid injection in the situation where a cylinder volume is small is implement | achieved by the change of the embodiment of the fuel injection using the fuel injection valve 28. FIG. However, the liquid injection in the present invention is not limited to the above-described one. For example, the liquid injection is performed with a configuration capable of injecting liquid other than fuel (for example, water) into the combustion chamber 14. It may be.

  By the way, in Embodiment 1 and 2 mentioned above, the internal combustion engine 10 provided with the turbo supercharger 24 was demonstrated as an example as an internal combustion engine used as the object of this invention. However, the internal combustion engine that is the subject of the present invention is not limited to the above, and may be, for example, an internal combustion engine that includes a turbocharger of a system other than a turbocharger, or a natural engine having a high compression ratio. It may be an intake type internal combustion engine.

DESCRIPTION OF SYMBOLS 10 Internal combustion engine 12 Piston 14 Combustion chamber 16 Intake passage 18 Exhaust passage 20 Air cleaner 22 Air flow meter 24 Turbocharger 24a Turbocharger compressor 24b Turbocharger turbine 26 Throttle valve 28 Fuel injection valve 30 Ignition plug 32 Ignition Coil 34 Intake valve 36 Exhaust valve 38 Intake variable valve mechanism 40 Exhaust variable valve mechanism 42 Crankshaft 44 Crank angle sensor 46 ECU (Electronic Control Unit)
48 In-cylinder pressure sensor 50 Intake cam angle sensor 52 Exhaust cam angle sensor

Claims (5)

Pre-ignition detection means for detecting pre-ignition;
Pre-ignition control execution means for executing predetermined pre-ignition suppression control for suppressing occurrence of pre-ignition when pre-ignition is detected;
With
When the occurrence frequency of a small pre-ignition whose maximum in-cylinder pressure is lower than a predetermined value has reached a predetermined frequency, the pre-ignition suppression control execution means has a large operating condition of the internal combustion engine such that the maximum in-cylinder pressure is greater than or equal to the predetermined value. The control apparatus for an internal combustion engine, wherein the pre-ignition suppression control is executed only when an operating condition that may cause pre-ignition occurs. The pre-ignition suppression control is injection of liquid into the combustion chamber,
2. The control device for an internal combustion engine according to claim 1, wherein the injection of the liquid is executed during a period in which a cylinder volume is smaller than a predetermined value in an exhaust stroke, an intake stroke, or both strokes.   The liquid is injected separately from the fuel injection that is performed for the internal combustion engine to generate torque during a period in which the cylinder volume is smaller than the predetermined value in the exhaust stroke, the intake stroke, or both strokes. The control apparatus for an internal combustion engine according to claim 2, wherein the fuel injection is additional fuel injection.   In the liquid injection, the injection period of the fuel injection performed for the internal combustion engine to generate torque is extended to the advance side so that the in-cylinder volume overlaps the period smaller than the predetermined value in the intake stroke. The control apparatus for an internal combustion engine according to claim 2, wherein the fuel injection is performed in step 1. The internal combustion engine is a supercharged internal combustion engine,
The pre-ignition suppression control controls at least one of a closing timing of the exhaust valve and an opening timing of the intake valve so that scavenging of residual gas in the combustion chamber is promoted during supercharging. The control apparatus of the internal combustion engine as described in any one of 1-4.

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