JP2012145040A - Control device of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently suppress pre-ignition in an internal combustion engine with a supercharger.SOLUTION: An engine 10 includes an intake variable valve train 34, an exhaust variable valve train 36, the supercharger 38, an intake pressure sensor 44, an exhaust pressure sensor 46, a cylinder pressure sensor 48 and the like. When the pre-ignition is detected in any cylinder and the intake pressure is higher than the exhaust pressure, an ECU 50 enlarges an overlap period of an intake valve 30 and an exhaust valve 32, for example, in a cylinder which reaches an exhaust stroke at first after the pre-ignition is detected. As a result, the intake air smoothly flows out from the cylinder to an exhaust system using boost pressure. The exhaust gas flowing backward into the cylinder to become an ignition source is therefore efficiently discharged and the chain generation of the pre-ignition is suppressed.

Description

  The present invention relates to an internal combustion engine control apparatus, and more particularly, to an internal combustion engine control apparatus that executes control corresponding to pre-ignition (self-ignition before ignition).

  As a conventional technique, for example, as disclosed in Patent Document 1 (Japanese Patent Laid-Open No. 2000-97061), when the occurrence of pre-ignition is detected, the overlap period of the intake valve and the exhaust valve is reduced. A control device for an internal combustion engine is known. In the prior art, by reducing the overlap period, the blowback of the exhaust gas that flows backward from the exhaust passage into the cylinder is reduced, and the pre-ignition generated by using the blowback as an ignition source is suppressed.

JP 2000-97061 A JP-A-6-2558 JP 2007-113440 A

  By the way, in the above-described prior art, when the occurrence of pre-ignition is detected, the overlap period of the valve is reduced to reduce the exhaust gas blow-back, but this control is performed for an internal combustion engine having no supercharger. It is assumed. On the other hand, even in an internal combustion engine with a supercharger, there is a request to suppress pre-ignition, but when the above control is applied to an internal combustion engine with a supercharger, a presupposed intake pressure (supercharging pressure) Since the behavior of the exhaust pressure is different, there is a problem that pre-ignition cannot be efficiently suppressed.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to control an internal combustion engine capable of efficiently suppressing preignition in an internal combustion engine with a supercharger. Is to provide.

The first invention includes an overlap variable mechanism capable of variably setting an overlap period during which the intake valve and the exhaust valve are opened together,
A supercharger that supercharges intake air using the exhaust pressure or power of the internal combustion engine;
Pressure detecting means for detecting the intake pressure and the exhaust pressure,
Pre-ignition detection means for detecting these conditions as pre-ignition when pre-ignition occurs in the combustion chamber or when a situation that easily induces pre-ignition occurs,
And an overlap expansion control means for driving the overlap variable mechanism and expanding the overlap period when the pre-ignition is detected and the intake pressure is higher than the exhaust pressure. And

  According to a second aspect of the invention, the overlap expansion control means is configured to detect the intake air when the pre-ignition is detected and the intake pressure is higher than the exhaust pressure and the differential pressure between the two is equal to or greater than a predetermined value. Exhaust valve control means for extending the overlap period by retarding the closing timing of the exhaust valve while keeping the valve opening timing constant.

  According to a third aspect of the present invention, the overlap expansion control means is configured to detect the intake air when the pre-ignition is detected and the intake pressure is higher than the exhaust pressure and the differential pressure between the two is less than a predetermined value. Intake / exhaust valve control means is provided for extending the overlap period by advancing the valve opening timing and retarding the exhaust valve closing timing.

  4th invention is provided with the overlap expansion amount variable means which enlarges the expansion amount of the said overlap period, so that the cylinder pressure of the cylinder in which the said pre-ignition was detected is high.

  According to a fifth aspect of the present invention, there is provided an overlap reduction control means for driving the overlap variable mechanism to reduce the overlap period when the pre-ignition is detected and the intake pressure is lower than the exhaust pressure. Prepare.

  6th invention is provided with the overlap expansion amount variable means which enlarges the reduction amount of the said overlap period, so that the cylinder pressure of the cylinder in which the said pre-ignition was detected is high.

  7th invention is provided with the deposit corresponding | compatible control means which enlarges the reduction amount of the said overlap period, so that there are many deposits accumulated in the said combustion chamber.

  According to the eighth invention, the deposit correspondence control means calculates the amount of change in the inter-cylinder air amount imbalance from the initial state as an index corresponding to the deposit accumulation amount, and the larger the calculated value, The reduction amount of the overlap period is increased.

  According to the first invention, when the pre-ignition is detected and the intake pressure is higher than the exhaust pressure, such as during supercharging, the intake air is exhausted from the cylinder using the supercharging pressure. Can flow smoothly into the system. As a result, exhaust gas that flows back into the cylinder from the exhaust system can be discharged efficiently, so that the ignition source of pre-ignition can be reduced and the occurrence of the chain can be suppressed. Also, by improving the air blow-through from the inside of the cylinder to the exhaust system, the temperature inside the cylinder can be lowered and pre-ignition can be made more difficult to occur.

  According to the second invention, when the differential pressure between the intake pressure and the exhaust pressure is relatively large, the overlap period is expanded in order to use this differential pressure, and the exhaust gas flowing back into the cylinder is efficiently discharged. Can be discharged. Further, since the opening timing of the intake valve is kept constant, fluctuations in the intake air amount can be suppressed and torque can be stabilized.

  According to the third invention, when the differential pressure between the intake pressure and the exhaust pressure is relatively small, the phase delay angle of the intake valve and the phase advance angle of the exhaust valve are executed together, and the overlap period is further increased. Can be greatly enlarged. Thereby, even when the differential pressure is small, air can be sufficiently blown from the cylinder to the exhaust system. Therefore, exhaust and cooling in the cylinder can be performed efficiently, and pre-ignition can be effectively suppressed.

  According to the fourth invention, when the in-cylinder pressure is high, the amount of enlargement of the overlap period can be increased by the amount that pre-ignition is likely to occur. Thereby, since exhaust and cooling in a cylinder can be performed efficiently, even when the in-cylinder pressure is high, preignition can be stably suppressed.

  According to the fifth invention, when the pre-ignition is detected, if the intake pressure is lower than the exhaust pressure, considering that the exhaust gas easily flows back into the cylinder during the overlap period, The overlap period can be reduced. As a result, the amount of exhaust gas that flows back into the cylinder from the exhaust system can be reduced, and pre-ignition can be effectively suppressed.

  According to the sixth invention, when the in-cylinder pressure is high, the reduction amount of the overlap period can be increased by the amount that pre-ignition is likely to occur. As a result, the amount of exhaust gas flowing back into the cylinder from the exhaust system can be sufficiently reduced, so that pre-ignition can be stably suppressed even when the in-cylinder pressure is high.

  According to the seventh aspect of the invention, when the amount of deposit accumulation is large at the time when pre-ignition is detected, the deposit peeled off due to the impact at the time of occurrence of pre-ignition tends to become an ignition source in other cylinders. On the other hand, the larger the deposit amount, the greater the reduction amount of the overlap period, thereby preventing the peeled deposit from flowing backward from the exhaust system to the other cylinders. Therefore, generation of secondary pre-ignition in other cylinders can be suppressed.

  According to the eighth aspect, the deposit amount in the cylinder can be easily calculated as the amount of change in the inter-cylinder air amount imbalance.

It is a block diagram for demonstrating the system configuration | structure of Embodiment 1 of this invention. It is explanatory drawing which shows the state which expanded the overlap period of the valve | bulb by overlap expansion control. It is explanatory drawing which shows the state which reduced the overlap period of the valve | bulb by overlap reduction control. In Embodiment 1 of this invention, it is a flowchart of the control performed by ECU. In Embodiment 2 of this invention, it is explanatory drawing which shows the state which expanded the overlap period of the valve | bulb by 2nd overlap expansion control. In Embodiment 2 of this invention, it is a flowchart of the control performed by ECU. In Embodiment 3 of this invention, it is explanatory drawing which shows typically the data for calculating a pre-ignition chain | strand risk. It is explanatory drawing which shows the state which eliminated the overlap period of the valve | bulb by 2nd overlap reduction control. It is explanatory drawing which shows the valve timing set by the overlap reduction control between cylinders. It is explanatory drawing which shows the state which eliminated the overlap of the exhaust stroke between cylinders by the overlap reduction control between cylinders. In Embodiment 3 of this invention, it is a flowchart of the control performed by ECU.

Embodiment 1 FIG.
[Configuration of Embodiment 1]
The first embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a configuration diagram for explaining a system configuration according to the first embodiment of the present invention. The system according to the present embodiment includes an engine 10 as a multi-cylinder internal combustion engine. In FIG. 1, only one cylinder of the engine 10 is illustrated. Each cylinder of the engine 10 has a combustion chamber 14 defined by a piston 12, and the piston 12 is connected to a crankshaft 16 of the engine. The engine 10 also includes an intake passage 18 that sucks intake air into each cylinder, and an exhaust passage 20 through which exhaust gas is discharged from each cylinder.

  The intake passage 18 is provided with an electronically controlled throttle valve 22 that adjusts the intake air amount based on the accelerator opening and the like. On the other hand, the exhaust passage 20 is provided with a catalyst 24 such as a three-way catalyst for purifying exhaust gas. Each cylinder has a fuel injection valve 26 for injecting fuel into the intake port, a spark plug 28 for igniting an air-fuel mixture in the combustion chamber 14 (in-cylinder), and an intake port opened and closed with respect to the cylinder. An intake valve 30 that opens and an exhaust valve 32 that opens and closes the exhaust port with respect to the inside of the cylinder are provided.

  The engine 10 also includes an intake variable valve mechanism 34 that changes the opening / closing timing of the intake valve 30 for each cylinder, and an exhaust variable valve mechanism 36 that changes the opening / closing timing of the exhaust valve 32 for each cylinder. The intake variable valve mechanism 34 includes, for example, a VVT (Variable Valve Timing system) as disclosed in Japanese Unexamined Patent Publication No. 2000-87769, and an arm swing type as disclosed in Japanese Unexamined Patent Publication No. 2007-132326. It is comprised by either of these variable valve mechanisms, or it is comprised by combining both. Thus, the intake variable valve mechanism 34 can advance and retard the opening / closing timing and phase of the intake valve 30.

  The exhaust variable valve mechanism 36 has a known configuration that is substantially the same as that of the intake variable valve mechanism 34, and can advance and retard the opening / closing timing and phase of the exhaust valve 32. These variable valve mechanisms 34 and 36 constitute an overlap variable mechanism that can variably set an overlap period during which the valves 30 and 32 are opened together. In addition, as an overlap variable mechanism, instead of the variable valve mechanisms 34 and 36, for example, an electromagnetically driven valve mechanism as described in Japanese Patent Application Laid-Open No. 2007-16710 may be used.

  Further, the engine 10 includes a known supercharger (turbocharger) 38 that supercharges intake air using exhaust pressure. The supercharger 38 includes a turbine 38a that operates by receiving exhaust pressure, and a compressor 38b that is driven by the turbine 38a and supercharges intake air. In the present embodiment, a system equipped with a turbocharger has been exemplified. However, the present invention is not limited to this. For example, the present invention is also applied to a supercharger (supercharger) that mechanically drives a compressor by engine power. Can be applied.

  On the other hand, the system of the present embodiment includes a sensor system including a crank angle sensor 40, an air flow sensor 42, an intake pressure sensor 44, an exhaust pressure sensor 46, an in-cylinder pressure sensor 48, etc., and an ECU ( Electronic Control Unit) 50. The crank angle sensor 40 outputs a signal synchronized with the rotation of the crankshaft 16, and the air flow sensor 42 detects the intake air amount. The intake pressure sensor 44 detects intake pressure (supercharging pressure), and the exhaust pressure sensor 46 detects exhaust pressure. These sensors 44 and 46 constitute the pressure detection means of the present embodiment. ing. The in-cylinder pressure sensor 48 detects the pressure in the combustion chamber 14 (in-cylinder pressure), and constitutes the pre-ignition detection means of the present embodiment. The ECU 50 detects the occurrence of pre-ignition in the cylinder based on the output waveform of the in-cylinder pressure sensor 48.

  In addition to this, the sensor system includes various sensors necessary for controlling the engine 10 and a vehicle on which the engine 10 is mounted. An example of the sensor is a water temperature sensor that detects the cooling water temperature of the engine, an accelerator opening sensor that detects the accelerator opening, an air-fuel ratio sensor that detects the exhaust air-fuel ratio, and the like. These sensors are connected to the input side of the ECU 50. Various actuators including the throttle valve 22, the fuel injection valve 26, the spark plug 28, the variable valve mechanisms 34 and 36 are connected to the output side of the ECU 50.

  Then, the ECU 50 drives each actuator while detecting operation information of the engine using a sensor system, and executes operation control. Specifically, the engine speed and the crank angle are detected based on the output of the crank angle sensor 40, and the intake air amount is calculated based on the output of the air flow sensor 42. Further, the engine load is calculated based on the intake air amount, the engine speed, and the like. Then, the fuel injection timing and ignition timing are determined based on the crank angle, and when these timings arrive, the fuel injection valve 26 and the spark plug 28 are driven. Thereby, the air-fuel mixture is combusted in the cylinder, and the engine can be operated. In addition, the ECU 50 controls the valve timing control for controlling the phase and opening / closing timing of the valves 30 and 32 by the variable valve mechanisms 34 and 36 according to the operating state of the engine, and drives a known waste gate valve. Supercharging control for changing the operating state (supercharging pressure) of the feeder 38 is executed.

[Features of Embodiment 1]
In the present embodiment, when a pre-ignition occurs in the combustion chamber 14 or a situation in which pre-ignition is likely to occur is generated, these states are detected as pre-ignition. And when preignition is detected, it is set as the structure which performs either the below-mentioned overlap expansion control or overlap reduction control according to the magnitude relationship between intake pressure and exhaust pressure.

  The occurrence of pre-ignition can be detected for each cylinder by a known detection method based on, for example, the in-cylinder pressure, the ion current flowing between the electrodes of the spark plug 28, the knocking vibration frequency, and the like. That is, when pre-ignition occurs, the in-cylinder pressure and ion current increase before ignition, or a specific vibration frequency increases when knocking occurs. Therefore, the ECU 50 detects the occurrence of pre-ignition based on these phenomena. . Further, as is generally known, preignition is likely to occur when the gas temperature in the cylinder rises greatly. The ECU 50 can detect such an operating state as a situation where pre-ignition is likely to occur based on the output of the sensor system.

(Overlap expansion control)
The pre-ignition tends to be generated by using a component (solid or liquid containing deposit) in the exhaust gas existing in the cylinder as an ignition source. In addition, when pre-ignition occurs in some cylinders, the deposit in the cylinder is easily peeled and discharged due to the impact at the time of occurrence, but this deposit is caused by the reverse flow of the exhaust gas and the reverse flow to the other cylinders. This causes a secondary pre-ignition in the cylinders.

  For this reason, in the overlap expansion control, when the control condition “pre-ignition is detected and the intake pressure is higher than the exhaust pressure” is satisfied, the overlap period of the valves 30 and 32 is not satisfied. It expands compared to the time, so that the exhaust gas in the cylinder is discharged efficiently. In this case, as a cylinder (cylinder to be controlled) that performs overlap expansion control, for example, a cylinder that first reaches the exhaust stroke after detecting pre-ignition, a cylinder that easily generates secondary pre-ignition, or the like is selected. Is done. In addition, the cylinder in which secondary pre-ignition is likely to occur is a cylinder in which the exhaust gas in the cylinder in which pre-ignition has occurred is likely to flow backward, and is specified according to the ignition sequence, the structure of the exhaust system, etc. It is.

  Therefore, in the overlap expansion control, when the control condition is satisfied, the overlap period is expanded only for the cylinder to be controlled, and in other cylinders, the overlap period is set to the normal size (the control condition is not satisfied). The size of the case). The normal overlap period is set shorter than when the overlap enlargement control is executed. In the present invention, when performing overlap expansion control, all cylinders may be controlled cylinders. For example, in a V-type engine or the like, all cylinders belonging to the bank on which pre-ignition has occurred may be set as control target cylinders.

  Next, a specific method for expanding the overlap period is illustrated. FIG. 2 is an explanatory diagram showing a state in which the overlap period of the valve is enlarged by the overlap enlargement control. As shown in this figure, in the overlap expansion control, the overlap period is expanded by driving the exhaust variable valve mechanism 36 and retarding the phase of the exhaust valve 32 in the cylinder to be controlled. At this time, the intake valve 30 is preferably kept in a constant phase in order to suppress fluctuations in the intake air amount.

  According to the overlap expansion control, when the pre-ignition is detected and the intake pressure is higher than the exhaust pressure, such as during supercharging, the intake air using the supercharging pressure is used in the control target cylinder. Can smoothly flow out of the cylinder into the exhaust system. As a result, exhaust gas that flows back into the cylinder from the exhaust system can be discharged efficiently, so that the ignition source of pre-ignition can be reduced and the occurrence of the chain can be suppressed. Also, by improving the air blow-through from the inside of the cylinder to the exhaust system, the temperature inside the cylinder can be lowered and pre-ignition can be made more difficult to occur.

(Overlap reduction control)
When the pre-ignition is detected, if the intake pressure is lower than the exhaust pressure (such as when supercharging is not performed), overlap reduction control is executed. FIG. 3 is an explanatory view showing a state in which the overlap period of the valve is reduced by the overlap reduction control. As shown in this figure, in the overlap reduction control, the overlap period is compared with the normal time (when the overlap reduction control is not executed) by advancing the phase of the exhaust valve 32 in the cylinder to be controlled. to shrink.

  When the intake pressure is lower than the exhaust pressure, the exhaust gas easily flows back into the cylinder during the overlap period. In this case, according to the overlap reduction control, it is possible to reduce the amount of exhaust gas that flows back from the exhaust system into the cylinder by reducing the overlap period of the cylinders to be controlled. Can be suppressed. Note that the control target cylinder of the overlap reduction control is set in the same manner as in the overlap enlargement control.

[Specific Processing for Realizing Embodiment 1]
Next, a specific process for realizing the above-described control will be described with reference to FIG. FIG. 4 is a flowchart of control executed by the ECU in the first embodiment of the present invention. The routine shown in this figure is repeatedly executed while the engine is operating. In the routine shown in FIG. 4, first, in step 100, it is determined whether or not pre-ignition is detected. If pre-ignition is not detected, normal control is executed in step 102.

  If pre-ignition is detected, the intake pressure and exhaust pressure are read by the sensors 44 and 46 in step 104 to determine whether the exhaust pressure is higher than the exhaust pressure. If the exhaust pressure is higher than the intake pressure, the overlap reduction control is executed in step 106 by advancing the phase of the exhaust valve 32 of the cylinder to be controlled. Further, when the intake pressure is higher than the exhaust pressure, in step 108, the overlap expansion control is executed by retarding the phase of the exhaust valve 32 of the cylinder to be controlled.

  As described above in detail, according to the present embodiment, the overlap expansion control and the overlap reduction control can be properly used according to the magnitude relationship between the intake pressure and the exhaust pressure. That is, when detecting pre-ignition, the exhaust gas in the cylinder can be efficiently discharged from the cylinder to be controlled, regardless of whether the intake pressure or the exhaust pressure is high. Therefore, in an engine with a supercharger, it is possible to prevent pre-ignition from occurring in a chain and improve drivability. Further, in the present embodiment, as shown in FIGS. 2 and 3, the phase (opening / closing timing) of the intake valve 30 is kept constant in both the overlap enlargement control and the overlap reduction control. Therefore, fluctuations in the intake air amount can be suppressed during the execution of the control, and the torque can be stabilized.

  In the first embodiment, step 108 in FIG. 4 shows a specific example of the overlap enlargement control means in claim 1, and step 106 shows a specific example of the overlap reduction control means in claim 5. . In the first embodiment, when the intake pressure and the exhaust pressure are equal, either the overlap expansion control or the overlap reduction control may be executed.

Embodiment 2. FIG.
Next, a second embodiment of the present invention will be described with reference to FIGS. In the present embodiment, in the configuration and control substantially the same as in the first embodiment, overlap expansion control is performed in two types according to the differential pressure between the intake pressure and the exhaust pressure (hereinafter referred to as intake / exhaust differential pressure). It is characterized by being divided into control. In the present embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

[Features of Embodiment 2]
In the present embodiment, in the same manner as in the first embodiment, overlap enlargement control is executed when the control condition is satisfied. However, the overlap expansion control is executed when the intake / exhaust differential pressure (= intake pressure−exhaust pressure) is equal to or higher than the predetermined value Pc and when the intake / exhaust differential pressure is less than the predetermined value Pc. Second overlap enlargement control. The control target cylinders of the first and second overlap expansion controls are set in the same manner as in the overlap expansion control described in the first embodiment.

(First overlap expansion control)
This control is described as overlap enlargement control (FIG. 2) in the first embodiment. That is, in the first overlap expansion control, when the control condition is satisfied and the intake / exhaust differential pressure is equal to or larger than the predetermined value Pc, the phase of the intake valve 30 is kept constant in the cylinder to be controlled. The phase of the exhaust valve 32 is retarded and the overlap period is expanded.

(Second overlap enlargement control)
FIG. 5 is an explanatory diagram showing a state where the overlap period of the valve is enlarged by the second overlap enlargement control in the second embodiment of the present invention. As shown in this figure, in the second overlap expansion control, the phase of the intake valve 30 is advanced in the controlled cylinder when the control condition is satisfied and the intake / exhaust differential pressure is less than a predetermined value Pc. The phase of the exhaust valve 32 is retarded and the overlap period is greatly expanded.

  Here, when the suction / exhaust pressure difference is small, even if the overlap period is extended, it is relatively difficult for air to blow out from the cylinder to the exhaust system. For this reason, in the second overlap expansion control, the phase advance angle of the intake valve 30 and the phase delay angle of the exhaust valve 32 are executed together, and the overlap period is longer than that during the execution of the first overlap expansion control. Expand further. As a result, even when the suction / exhaust pressure difference is small, air can be sufficiently blown out from the cylinder to the exhaust system, and the exhaust and cooling in the cylinder can be performed efficiently. The overlap described in the first embodiment The effect of enlargement control can be exhibited stably.

  When the second overlap expansion control is executed, the intake air amount changes by advancing the phase of the intake valve 30, and the torque changes accordingly. There is a risk that a torque difference (torque step) may occur. For this reason, it is preferable to execute torque step reduction control in the cylinder to be controlled. In torque step reduction control, the amount of change in torque is calculated based on the amount of advancement of the intake valve phase (the amount of change in intake air), and the fuel injection amount in the control target cylinder is corrected so as to cancel this amount of change in torque. To do. On the other hand, when the second overlap expansion control is executed, it is preferable to appropriately control the fuel injection timing and the like so that the air-fuel mixture does not blow through the exhaust system due to an extremely wide overlap period.

  In addition, the predetermined value Pc for determining the switching between the first and second overlap expansion controls described above is the minimum at which the first overlap expansion control functions effectively, for example (the air blows out sufficiently by the control). It is set corresponding to the intake / exhaust differential pressure. That is, when the suction / exhaust differential pressure is less than the predetermined value Pc, the second overlap expansion control is executed because air blow-off does not occur sufficiently even if the first overlap expansion control is executed. Further, the predetermined value Pc may be variably set according to the intake air temperature, for example.

[Specific Processing for Realizing Embodiment 2]
Next, specific processing for realizing the above-described control will be described with reference to FIG. FIG. 6 is a flowchart of control executed by the ECU in the second embodiment of the present invention. The routine shown in this figure is repeatedly executed while the engine is operating. In the routine shown in FIG. 6, first, in steps 200 to 206, processing similar to that in steps 100 to 106 in the first embodiment (FIG. 4) is executed.

  Next, in step 208, when the intake pressure is higher than the exhaust pressure, it is determined whether the intake / exhaust differential pressure is less than a predetermined value Pc. If the intake / exhaust differential pressure is equal to or greater than the predetermined value Pc, in step 210, the phase of the exhaust valve 32 of the cylinder is retarded while the phase of the intake valve 30 of the cylinder to be controlled is kept constant. First overlap enlargement control is executed. On the other hand, if the intake / exhaust differential pressure is less than the predetermined value Pc, in step 212, the phase advance angle of the intake valve 30 and the phase retard angle of the exhaust valve 32 of the cylinder to be controlled are performed together. Execute lap enlargement control. In step 214, the torque step reduction control described above is executed.

  In the second embodiment, steps 210 and 212 in FIG. 6 show a specific example of the overlap enlargement control means in claim 1. Of these, step 210 is the exhaust valve control means in claim 2. A specific example, step 212 shows a specific example of the intake / exhaust valve control means in claim 3 respectively. Step 206 shows a specific example of the overlap reduction control means in claim 5.

Embodiment 3 FIG.
Next, Embodiment 3 of the present invention will be described with reference to FIGS. The present embodiment is characterized in that the enlargement amount and reduction amount of the overlap period are variably set in the configuration and control substantially the same as those of the first embodiment. In the present embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

[Features of Embodiment 3]
As described above, when pre-ignition occurs in some cylinders, the ignition source such as deposits exhausted from the cylinders flows back to the other cylinders and causes secondary pre-ignition in other cylinders. Become. For this reason, in the present embodiment, “pre-ignition chain risk” is calculated as an index indicating the likelihood of secondary pre-ignition, and control is switched based on the calculated value.

  FIG. 7 is an explanatory diagram schematically showing data for calculating the pre-ignition chain risk, and this data is stored in advance in the ECU 50 as a data map or the like. As shown in FIG. 7, the pre-ignition chain risk is calculated based on the maximum value of the in-cylinder pressure in the cylinder where pre-ignition first occurs and the deposit accumulation index. The deposit accumulation index is an index that increases in accordance with the amount of deposit accumulated in the cylinder, and a calculation method thereof will be described later.

  In the cylinder where the pre-ignition first occurs (primary cylinder), the greater the maximum value of the in-cylinder pressure and the greater the amount of deposit accumulated, the greater the amount of deposits peeled off due to the impact when pre-ignition occurs. Then, it is considered that secondary pre-ignition is more likely to occur as the amount of deposit discharged from the primary cylinder increases. For this reason, the pre-ignition chain risk data shown in FIG. 7 is set so that the pre-ignition chain risk increases as the maximum value of the in-cylinder pressure in the primary cylinder increases or as the deposit accumulation index increases. Yes.

  In the present embodiment, when the control condition that “pre-ignition is detected and the intake pressure is lower than the exhaust pressure” is satisfied, the pre-ignition chain risk is calculated based on the data of FIG. Depending on the calculated value, one of the following three types of overlap reduction control is executed. That is, the present embodiment is characterized in that the overlap reduction control of the first and second embodiments is divided into three types of control according to the pre-ignition chain risk. The control target cylinders for these three types of overlap reduction control are set in the same manner as in the overlap enlargement control described in the first embodiment. In FIG. 7, the pre-ignition chain risk has three kinds of values of “large”, “medium”, and “small”, and these values are divided into three levels according to the in-cylinder pressure and the deposit accumulation index. The case of changing to is illustrated. However, the present invention is not limited to this, and the types of values that can be taken by the pre-ignition chain risk and the number of stages of change may be arbitrarily set.

(First overlap reduction control)
This control is executed, for example, when the pre-ignition chain risk is “low”, and the control content is described as overlap reduction control (FIG. 3) in the first embodiment. That is, the first overlap reduction control reduces the overlap period by advancing the phase of the exhaust valve 32 while keeping the phase of the intake valve 30 constant in the cylinder to be controlled.

  According to the first overlap reduction control, in the state where the intake pressure is lower than the exhaust pressure, when the secondary pre-ignition is slightly likely to occur, the overlap period of the control target cylinder is reduced to some extent, The amount of exhaust gas flowing back into the inside can be appropriately reduced. Accordingly, it is possible to suppress the deposits and the like discharged from the primary cylinder from flowing back to the other cylinders as an ignition source and inducing secondary pre-ignition.

(Second overlap reduction control)
This control is executed when the pre-ignition chain risk is “medium”. FIG. 8 is an explanatory view showing a state in which the overlap period of the valve is eliminated by the second overlap reduction control. As shown in this figure, in the second overlap reduction control, the overlap period is set to the first overlap reduction control by retarding the intake valve 30 and advancing the exhaust valve 32 in the cylinder to be controlled. Or, preferably, the state in which the overlap period is almost eliminated.

  According to the second overlap reduction control, when secondary pre-ignition is relatively likely to occur, the overlap period of the control target cylinder is greatly reduced, and the amount of exhaust gas flowing back into the cylinder is sufficiently large. Can be reduced. Thereby, compared with 1st overlap reduction control, generation | occurrence | production of secondary pre-ignition can be suppressed effectively. Further, by increasing the reduction amount of the overlap period, the intake air amount is reduced and the actual compression ratio is lowered, so that the ease of occurrence of pre-ignition can be further reduced.

(Cylinder overlap reduction control)
This control is executed when the pre-ignition chain risk is “high”. FIG. 9 is an explanatory diagram showing valve timings set by the overlap reduction control between cylinders, and FIG. 10 is an explanatory diagram showing a state in which the overlap of the exhaust stroke is eliminated between the cylinders by the overlap reduction control between cylinders. It is. As shown in FIG. 9, the overlap reduction control between cylinders maintains the state in which the overlap period is almost eliminated by retarding both the intake valve 30 and the exhaust valve 32 in the cylinder to be controlled. Further, by delaying the valve opening period (exhaust stroke) of the exhaust valve 32, as shown in FIG. 10, the exhaust stroke of the cylinder to be controlled does not overlap the exhaust stroke of the primary cylinder.

  According to the overlap reduction control between cylinders, when secondary pre-ignition is extremely likely to occur, the overlap period of the cylinder to be controlled is greatly reduced, and the amount of exhaust gas flowing back into the cylinder is sufficiently reduced. Can be reduced. In addition, since the overlap of the exhaust stroke with respect to the primary cylinder is eliminated, it is possible to more reliably prevent an ignition source such as deposit discharged from the primary cylinder from flowing into the control target cylinder. Therefore, even in a situation where secondary pre-ignition is extremely likely to occur, this can be reliably suppressed.

  As described above, in the present embodiment, as the maximum value of the in-cylinder pressure in the primary cylinder is larger and as the deposit accumulation index is larger (the deposit accumulation amount is larger), the overlap period of the control target cylinder is reduced. The amount is increased. Thereby, the overlap period can be appropriately reduced according to the ease of occurrence of secondary pre-ignition. Therefore, adverse effects (insufficient internal EGR, deteriorated drivability, etc.) caused by reducing the overlap period can be avoided as much as possible while stably suppressing the occurrence of pre-ignition chain.

  In the second overlap reduction control and the inter-cylinder overlap reduction control, there is a possibility that a torque step may be generated between the control target cylinder and the other cylinders by changing the phase of the intake valve 30. As described in the second embodiment, it is preferable to execute the torque step reduction control.

(Deposit accumulation index)
In the present embodiment, as the deposit accumulation index, for example, a change amount in which the inter-cylinder air amount imbalance is changed from the initial state is used. The inter-cylinder air amount imbalance is, for example, how much the intake air amount in a cylinder deviates from the intake air amount in other cylinders when only one cylinder out of all cylinders has a difference in intake air amount. This is expressed as a percentage. The inter-cylinder air amount imbalance tends to increase from the initial state (the state at the time of engine shipment, etc.) as the amount of deposit accumulated in the cylinder increases.

  For this reason, the ECU 50 calculates the amount of change in the inter-cylinder air amount imbalance from the initial state as a deposit accumulation index. Then, the pre-ignition chain risk is calculated by referring to the data map of FIG. 7 based on the deposit accumulation index and the maximum value of the in-cylinder pressure. As a result, the deposit amount in the cylinder can be easily calculated as the change amount of the inter-cylinder air amount imbalance.

[Specific Processing for Realizing Embodiment 3]
Next, specific processing for realizing the above-described control will be described with reference to FIG. FIG. 11 is a flowchart of control executed by the ECU in the third embodiment of the present invention. The routine shown in this figure is executed in place of step 106 in the first embodiment (FIG. 4) or step 206 in the second embodiment (FIG. 6). In the routine shown in FIG. 11, first, in step 300, it is determined whether or not the pre-ignition chain risk is “small”. If this determination is satisfied, in step 302, the first overlap reduction is performed. Execute control.

  If the determination in step 300 is not established, it is determined in step 304 whether or not the pre-ignition chain risk is “medium”. Execute overlap reduction control. If the determination in step 304 is not established, the pre-ignition chain risk is “high”, and therefore, inter-cylinder overlap reduction control is executed in step 308.

  In the third embodiment, steps 302, 306, and 308 in FIG. 11 show a specific example of the overlap reduction control means in claim 5, and among these, steps 302 and 306 are over-states in claim 6. Specific examples of the wrap enlargement amount varying means and the deposit correspondence control means in claim 7 are shown.

(Application to overlap expansion control)
Further, in the third embodiment, when the pre-ignition is detected and the intake pressure is lower than the exhaust pressure, the cylinder to be controlled increases as the maximum value of the in-cylinder pressure in the primary cylinder from which the pre-ignition is first detected is larger. The amount of reduction in the overlap period was increased. On the other hand, in the present invention, the same configuration can be adopted in the overlap enlargement control described in the first and second embodiments. That is, in the present invention, when pre-ignition is detected and the intake pressure is higher than the exhaust pressure, the enlargement amount of the overlap period may be increased as the maximum value of the in-cylinder pressure in the primary cylinder is larger. .

  According to this configuration, the following effects can be obtained. Secondary pre-ignition tends to occur as the maximum value of the in-cylinder pressure increases, so if the maximum value of the in-cylinder pressure is large, the amount of increase in the overlap period is increased accordingly and the boost pressure is increased. The exhaust and cooling in the used cylinder can be performed efficiently. That is, the overlap period can be appropriately extended according to the ease of occurrence of secondary pre-ignition. Therefore, the adverse effects (excessive internal EGR, deterioration of drivability, etc.) caused by extending the overlap period can be avoided as much as possible while stably suppressing the occurrence of chain pre-ignition. In addition, the said structure has shown the specific example of the overlap expansion amount variable means in Claim 4.

  In the first to third embodiments, various configurations are individually illustrated. However, the present invention is not limited to the individual implementation. That is, a specific configuration included in the present invention may be realized by combining any of a plurality of configurations of Embodiments 1 to 3 within a feasible range. For example, the configuration of the third embodiment may be combined with the configuration of the second embodiment.

10 Engine (Internal combustion engine)
12 piston 14 combustion chamber 16 crankshaft 18 intake passage 20 exhaust passage 22 throttle valve 24 catalyst 26 fuel injection valve 28 spark plug 30 intake valve 32 exhaust valve 34 variable intake valve mechanism (overlapping variable mechanism)
36 Exhaust variable valve mechanism (overlapping variable mechanism)
38 Supercharger 38a Turbine 38b Compressor 40 Crank angle sensor 42 Air flow sensor 44 Intake pressure sensor (pressure detection means)
46 Exhaust pressure sensor (pressure detection means)
48 In-cylinder pressure sensor (pre-ignition detection means)
50 ECU

Claims (8)

An overlap variable mechanism capable of variably setting an overlap period in which the intake valve and the exhaust valve are opened together;
A supercharger that supercharges intake air using the exhaust pressure or power of the internal combustion engine;
Pressure detecting means for detecting the intake pressure and the exhaust pressure,
Pre-ignition detection means for detecting these conditions as pre-ignition when pre-ignition occurs in the combustion chamber or when a situation that easily induces pre-ignition occurs,
An overlap expansion control means for driving the overlap variable mechanism to expand the overlap period when the pre-ignition is detected and the intake pressure is higher than the exhaust pressure;
A control device for an internal combustion engine, comprising:   When the pre-ignition is detected and the intake pressure is higher than the exhaust pressure and the differential pressure between the two is greater than or equal to a predetermined value, the overlap expansion control means keeps the opening timing of the intake valve constant 2. The control apparatus for an internal combustion engine according to claim 1, further comprising exhaust valve control means for extending the overlap period by delaying a closing timing of the exhaust valve in a state where the exhaust valve is held.   The overlap expansion control means advances the opening timing of the intake valve when the pre-ignition is detected and the intake pressure is higher than the exhaust pressure and the differential pressure between the two is less than a predetermined value. The control apparatus for an internal combustion engine according to claim 1 or 2, further comprising intake / exhaust valve control means for extending the overlap period by retarding the valve closing timing of the exhaust valve.   4. The internal combustion engine according to claim 1, further comprising an overlap expansion amount varying unit configured to increase an expansion amount of the overlap period as the in-cylinder pressure of the cylinder in which the pre-ignition is detected is higher. Engine control device.   2. An overlap reduction control unit that drives the overlap variable mechanism to reduce the overlap period when the pre-ignition is detected and the intake pressure is lower than the exhaust pressure. 5. The control device for an internal combustion engine according to any one of items 4 to 4.   The control apparatus for an internal combustion engine according to claim 5, further comprising an overlap expansion amount varying unit that increases a reduction amount of the overlap period as the in-cylinder pressure of the cylinder in which the pre-ignition is detected is higher.   The control apparatus for an internal combustion engine according to claim 5 or 6, further comprising deposit control means for increasing the reduction amount of the overlap period as the amount of deposit accumulated in the combustion chamber increases.   The deposit correspondence control means calculates an amount of change of the inter-cylinder air amount imbalance from the initial state as an index corresponding to the deposit amount, and the larger the calculated value, the smaller the amount of reduction of the overlap period. The control apparatus for an internal combustion engine according to claim 7, wherein the control apparatus is configured to increase

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