JP5614377B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to an internal combustion engine control apparatus, and more particularly to an internal combustion engine control apparatus suitable for executing control of an internal combustion engine mounted on a vehicle.

  2. Description of the Related Art Conventionally, an internal combustion engine including an in-cylinder pressure sensor and a boost sensor is known as disclosed in, for example, Japanese Patent Application Laid-Open No. 4-314951. This publication also calculates the deviation between the in-cylinder pressure sensor output value during the intake stroke and the in-cylinder pressure sensor output value during the exhaust stroke, and calculates the in-cylinder pressure sensor output value from the ratio between the deviation and the boost sensor output value. A control device that corrects a voltage-pressure coefficient for converting the pressure into the in-cylinder pressure is disclosed. The difference in output characteristics due to individual variations and deterioration with time of the in-cylinder pressure sensor is corrected uniformly throughout the entire process.

JP-A-4-314951 JP 2010-133329 A JP 2007-146785 A Japanese Patent Laid-Open No. 3-037356 JP 2010-071284 A JP 2007-303293 A JP 2008-255932 A

  By the way, in the above-mentioned internal combustion engine, when pre-ignition or excessive knocking occurs, the charge output of the in-cylinder pressure sensor suddenly changes because the combustion pressure becomes very high, and the output voltage after the maximum in-cylinder pressure does not drop properly. Occurs (solid line 60 in FIG. 2). Therefore, there is a difference between the actual in-cylinder pressure and the output voltage in the expansion / exhaust stroke of the cycle in which abnormal combustion occurs. According to the above-described conventional control device, the output voltage is uniformly corrected in the entire stroke by correcting the voltage-pressure coefficient. Such correction may be used after the next cycle, but it is not appropriate for the cycle in which abnormal combustion has occurred because the in-cylinder pressure in the intake stroke may become a negative value (the broken line in FIG. 2). 62). If the in-cylinder pressure waveform can be obtained with high accuracy even in a cycle in which abnormal combustion occurs, it is desirable for various controls using the in-cylinder pressure.

  The present invention has been made to solve the above-described problems, and it is an object of the present invention to provide a control device for an internal combustion engine that can obtain a highly accurate in-cylinder pressure waveform in a cycle in which abnormal combustion occurs. To do.

In order to achieve the above object, a first invention is a control device for an internal combustion engine,
An in-cylinder pressure sensor provided in a cylinder of the internal combustion engine;
Abnormal combustion determining means for determining whether or not abnormal combustion has occurred in the cylinder;
Maximum in-cylinder pressure detection position acquisition means for acquiring a crank angle at which the maximum in-cylinder pressure is detected (hereinafter referred to as a maximum in-cylinder pressure detection crank angle);
Crank angle acquisition means for acquiring a crank angle immediately before an error occurs in the output value of the in-cylinder pressure sensor after the maximum in-cylinder pressure detection crank angle of the cycle in which the abnormal combustion has occurred,
An in-cylinder pressure waveform correcting unit that replaces the in-cylinder pressure waveform after the crank angle immediately before the occurrence of the error with the in-cylinder pressure waveform during normal combustion under the same operating conditions for the cycle in which the abnormal combustion occurs is provided.

The second invention is the first invention, wherein
The crank angle acquisition means includes
A change amount calculating means for sequentially calculating a change amount of the in-cylinder pressure at every predetermined crank angle interval after the maximum in-cylinder pressure detection crank angle of the cycle in which the abnormal combustion has occurred;
Threshold determination means for determining whether or not the change amount is smaller than a threshold;
An acquisition means is provided for acquiring a crank angle immediately before it is determined that the amount of change is smaller than a threshold as a crank angle immediately before the error occurs.

The third invention is the first or second invention, wherein
Determining means for determining whether or not a calculated value obtained by dividing the maximum in-cylinder pressure by the in-cylinder pressure difference between the in-cylinder pressure in the exhaust stroke and the in-cylinder pressure in the intake stroke is equal to or less than a predetermined value;
When the calculated value is larger than the predetermined value, a cylinder pressure waveform uniform correcting means for uniformly correcting the cylinder pressure after the maximum cylinder pressure generating crank angle of the cycle in which the abnormal combustion has occurred with the cylinder pressure difference. Further comprising
The in-cylinder pressure waveform correcting means is executed when the calculated value is not more than the predetermined value.

  According to a fourth aspect of the present invention, in any one of the first to third aspects, the in-cylinder pressure waveform during normal combustion is calculated based on a Wiebe function.

  According to the first or second invention, for the cycle in which abnormal combustion occurs, the in-cylinder pressure waveform after the crank angle immediately before the error occurs in the output value of the in-cylinder pressure sensor is obtained from the in-cylinder pressure during normal combustion under the same operating conditions. It can be replaced with a waveform. Therefore, according to the present invention, a highly accurate in-cylinder pressure waveform can be obtained even when abnormal combustion occurs and a deviation occurs in the output value of the in-cylinder pressure sensor.

  According to the third invention, when the calculated value obtained by dividing the maximum in-cylinder pressure in the cycle in which abnormal combustion occurs by the in-cylinder pressure difference between the in-cylinder pressure in the exhaust stroke and the in-cylinder pressure in the intake stroke is equal to or less than a predetermined value, By correcting the in-cylinder pressure waveform in the first invention, a highly accurate in-cylinder pressure waveform can be obtained. Further, when the calculated value is larger than a predetermined value, the cylinder pressure after the maximum cylinder pressure generating crank angle is uniformly corrected by the cylinder pressure difference, thereby sufficiently reducing the calculation processing amount and sufficiently accurate. A high in-cylinder pressure waveform can be obtained.

It is a figure for demonstrating the system configuration | structure of Embodiment 1 of this invention. It is a figure for demonstrating the shift | offset | difference which arises in the output voltage of an in-cylinder pressure sensor when preignition or excessive knocking arises. It is a figure which shows the relationship between the cylinder pressure P and the crank angle CA in the cycle which abnormal combustion generate | occur | produced. It is a figure which shows PV ( ^kappa) value corresponding to the cylinder pressure of FIG. FIG. 4 is a diagram showing in-cylinder pressure when an offset correction of ΔP is added after the maximum in-cylinder pressure in FIG. 3. FIG. 5 is a diagram showing PV ^κ values when an offset correction of ΔP is added after the maximum in-cylinder pressure in FIG. 4. It is a figure for demonstrating that an offset generate | occur | produces in the output value of the cylinder pressure sensor after the largest cylinder pressure. It is an enlarged view of the cylinder pressure waveform shown in FIG. It is a figure for demonstrating calculation of MFB using a Wiebe function. It is a figure for demonstrating calculation of the cylinder pressure waveform at the time of normal combustion using a Wiebe function. It is a flowchart of the control routine which ECU50 performs in order to implement | achieve the 1st and 2nd characteristic control in Embodiment 1 of this invention. It is a figure for demonstrating the characteristic control in Embodiment 2 of this invention. It is a flowchart of the control routine which ECU50 performs in Embodiment 2 of this invention. It is a figure for demonstrating the characteristic control in Embodiment 2 of this invention. It is a flowchart of the control routine which ECU50 performs in Embodiment 3 of this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In addition, the same code | symbol is attached | subjected to the element which is common in each figure, and the overlapping description is abbreviate | omitted.

Embodiment 1 FIG.
[System Configuration of Embodiment 1]
FIG. 1 is a schematic configuration diagram for explaining a system configuration according to the first embodiment of the present invention. The system shown in FIG. 1 includes an internal combustion engine (hereinafter simply referred to as an engine) 10 that is a four-stroke engine. The engine 10 includes a plurality of (for example, four) cylinders 11, and one cylinder 11 is depicted in FIG. 1. In the present invention, the number of cylinders is not limited to this.

  Each cylinder 11 of the engine 10 has an ignition plug 12 that ignites an air-fuel mixture in the cylinder according to the ignition timing SA, a fuel injection valve 14 that directly injects fuel into the cylinder, and an in-cylinder pressure (combustion pressure) P. An in-cylinder pressure sensor (CPS) 16 for detection is attached. Further, the engine 10 is provided with a crank angle sensor 18 for detecting the rotation angle of the crankshaft (hereinafter referred to as crank angle CA) and a knock sensor 19 for detecting knocking.

  An intake passage 20 connected to each cylinder 11 is provided in the intake system of the engine 10. An air cleaner 22 is provided upstream of the intake passage 20. An air flow meter 24 for detecting a flow rate of air taken into the intake passage 20 (hereinafter referred to as intake air amount GA) is attached downstream of the air cleaner 22. An electronically controlled throttle valve 26 is provided downstream of the air flow meter 24. Near the throttle valve 26, a throttle opening sensor 28 for detecting the opening of the throttle valve 26 (hereinafter referred to as the throttle opening TA) is attached. An intake pressure sensor 30 for detecting the intake pressure Pim is attached downstream of the throttle valve 26. An intake valve 32 that opens and closes between the intake passage 20 and the combustion chamber of the cylinder 11 is provided at the downstream end of the intake passage 20.

  The exhaust system of the engine 10 is provided with an exhaust passage 34 connected to each cylinder. An exhaust valve 35 that opens and closes between the exhaust passage 34 and the combustion chamber of the cylinder 11 is provided at the upstream end of the exhaust passage 34. A catalyst 36 is provided downstream of the exhaust valve 35. For example, a three-way catalyst is used as the catalyst 36. Further, an EGR passage 38 connected to the intake passage 20 is provided in the exhaust passage 34 upstream of the catalyst 36. An EGR cooler 40 is provided in the EGR passage 38. A temperature sensor 42 is provided in the vicinity of the EGR cooler 40. An EGR valve 44 is provided downstream of the EGR cooler 40.

  An ECU (Electronic Control Unit) 50 is provided in the control system of the engine 10. In the input part of the ECU 50, the in-cylinder pressure sensor 16, the crank angle sensor 18, the knock sensor 19, the air flow meter 24, the throttle opening sensor 28, the intake pressure sensor 30, the temperature sensor 42, etc. are detected. Various sensors are connected. The ECU 50 stores in advance the relationship between the output voltage of the in-cylinder pressure sensor 16 and the in-cylinder pressure determined by experiments or the like, and calculates the in-cylinder pressure corresponding to the output voltage from this relationship. The output voltage and the in-cylinder pressure have a proportional relationship, and the output voltage increases as the in-cylinder pressure increases.

  In addition, the output portion of the ECU 50 includes a variable valve for variably controlling the opening / closing timing of the intake valve 32 and the exhaust valve 35 in addition to the ignition plug 12, the fuel injection valve 14, the throttle valve 26, and the EGR valve 44 described above. Various actuators for controlling the operating state of the mechanism (VVT) 52 and the like are connected. The ECU 50 controls the operating state of the engine 10 by operating various actuators according to a predetermined program based on the outputs of the various sensors described above.

[Characteristic Control in Embodiment 1]
In the system described above, abnormal combustion such as pre-ignition or excessive knocking may occur. FIG. 2 is a diagram showing an output voltage of the in-cylinder pressure sensor 16 in a cycle in which abnormal combustion occurs. When abnormal combustion such as pre-ignition or excessive knocking occurs, the combustion pressure becomes very high, so the charge output changes suddenly, and charge remains in the charge amplifier of the in-cylinder pressure sensor 16, or the actual in-cylinder pressure And a difference between the output voltage of the in-cylinder pressure sensor 16 and a certain time. Specifically, as shown in the exhaust stroke of FIG. 2, the output voltage during normal combustion is approximately equal in the intake stroke and the exhaust stroke, but during abnormal combustion, the output voltage in the exhaust stroke drifts upward and shifts. (Solid line 60).

  On the other hand, a method of correcting the entire in-cylinder pressure by using a deviation between the in-cylinder pressure in the intake stroke and the in-cylinder pressure in the exhaust stroke is conceivable. However, as indicated by the broken line 62 in the cycle in which abnormal combustion occurs. In addition, the in-cylinder pressure in the normal part also decreases, and there is a possibility that the in-cylinder pressure waveform in the intake stroke becomes a negative value. Therefore, there is a concern that many combustion state quantities, including the heat generation amount, cannot be calculated correctly.

  FIG. 3 is a diagram showing the relationship between the in-cylinder pressure P and the crank angle CA in a cycle in which abnormal combustion occurs. FIG. 3 is a graph in which the ECU 50 converts the output voltage of the solid line 60 in FIG. 2 into the in-cylinder pressure based on the relationship between the output voltage of the in-cylinder pressure sensor 16 and the in-cylinder pressure. ΔP shown in FIG. 3 is an in-cylinder pressure deviation (in-cylinder pressure difference) calculated from the output voltage in the intake stroke and the exhaust stroke. The actual in-cylinder pressure in the intake stroke and the exhaust stroke substantially coincide with each other. However, if abnormal combustion occurs, the output voltage may be shifted. Therefore, the in-cylinder pressure calculated from the output voltage is shifted by ΔP. ing.

FIG. 4 is a diagram showing PV ^κ values corresponding to the in-cylinder pressure of FIG. 3. Since the in-cylinder pressure drifts upward as shown in FIG. 3, the PV ^κ value, which is an index of the amount of heat generation, rises to the right, and the maximum value of PV ^κ cannot be calculated correctly. Therefore, various controls using the maximum value of PV ^κ cannot be executed correctly. Even in a cycle in which abnormal combustion occurs, various controls can be performed at an early stage if the in-cylinder pressure waveform can be obtained with high accuracy.

(First characteristic control)
Therefore, in the system of the present embodiment, as a first characteristic control, an offset correction of ΔP is performed only for the in-cylinder pressure after the maximum in-cylinder pressure, which is the cause of deviation in the behavior of the in-cylinder pressure, in the cycle in which abnormal combustion occurs. It was decided to. Further, after the next cycle, the offset correction of ΔP is continued in the whole process until a predetermined time elapses.

5 and 6 are diagrams showing the in-cylinder pressure and the PV ^κ value when the offset correction of ΔP is added after the maximum in-cylinder pressure in FIGS. 3 and 4. By applying a uniform correction of ΔP only to the in-cylinder pressure after the maximum in-cylinder pressure, the in-cylinder pressure waveform is corrected so that the in-cylinder pressures in the intake stroke and the exhaust stroke substantially match (FIG. 5). As a result, obtained PV ^kappa waveform as shown in FIG. 6, it is possible to calculate the maximum value of PV ^kappa. Therefore, various controls that require the maximum value of PV ^κ can be suitably executed.

  By the way, in the above-described control, when the drift amount ΔP of the in-cylinder pressure becomes a predetermined value or more, the in-cylinder pressure waveform after the maximum in-cylinder pressure may be corrected too low. This is because it is considered that the in-cylinder pressure sensor 16 is operating normally for a while after the occurrence of abnormal combustion (FIG. 7). The abnormality occurs in the output voltage of the in-cylinder pressure sensor 16 after the electric charge is not lost, and the offset correction amount of ΔP is not necessarily appropriate in the vicinity of the ignition timing. By considering this point, the in-cylinder pressure waveform can be obtained with higher accuracy, and various controls using the in-cylinder pressure can be executed with higher accuracy.

(Second characteristic control)
Therefore, in the system according to the present embodiment, as the second characteristic control, the first characteristic described above is performed only when the influence of the offset correction of ΔP is small as a ratio to the overall in-cylinder pressure, illustrated work, PV ^{κ, and the} like. When characteristic control is executed and the effect of offset correction of ΔP is large, correction is made as follows.

  FIG. 8 is an enlarged view of the in-cylinder pressure waveform shown in FIG. The broken line 70 represents the in-cylinder pressure waveform during normal combustion, and the solid line 72 represents the in-cylinder pressure waveform during abnormal combustion. Region A represents the crank angle section from when abnormal combustion occurs until before drift begins to occur. In the second characteristic control, the in-cylinder pressure waveform after the region A is replaced using an approximate expression calculated from the in-cylinder pressure waveform in the region A. In the determination method of the region A, a change amount of the in-cylinder pressure is calculated at predetermined crank angle intervals after the maximum in-cylinder pressure, and the determination is made based on whether or not this change amount is larger than a threshold value. If it is greater than the threshold value, it is determined that the charge is normally removed and the output voltage of the sensor is still normal. On the other hand, if it is smaller than the threshold value, it is determined that the charge cannot be lost and the sensor output voltage may be shifted. Therefore, the in-cylinder pressure waveform after the region A is replaced with the in-cylinder pressure waveform during normal combustion in the same operation state. This in-cylinder pressure waveform during normal combustion is calculated or stored in advance for each operating condition using an approximate expression. The in-cylinder pressure waveform during normal combustion can be estimated using, for example, the Wiebe function, and the outline is as follows.

Formula (1) is a formula for calculating the combustion ratio MFB using the Wiebe function. The ignition timing θ _i and the combustion speed θ _b in equation (1) are expressed by equations (2) and (3), respectively. In each equation, CA is a crank angle, SA is an ignition timing, KL is a load factor, VVT is a valve timing, and a, b, c, d, and e are adapted values adapted for each engine 10.

As shown in FIG. 9, the combustion rate MFB is calculated by giving the load factor KL, the ignition timing SA, and the valve timing VVT as input parameters to the equation (1) using the Wiebe function. Using equation (1), the relationship between the crank angle and the combustion ratio MFB can be calculated for each operating condition (KL, SA, VVT, etc.) (FIG. 10A). The relationship between the crank angle and the PV ^κ value shown in FIG. 10B can be obtained by applying the PV ^κ values at the combustion ratio of 0% and 100% under the respective operating conditions to the relationship shown in FIG. Further, by dividing PV ^κ in FIG. 10B by V ^κ , an in-cylinder pressure waveform for each operating condition shown in FIG. 10C is obtained. The ECU 50 shall appropriately calculate or store in advance the in-cylinder pressure waveform during normal combustion under each operating condition.

(Control routine)
FIG. 11 is a flowchart of a control routine executed by the ECU 50 in order to realize the first and second characteristic operations described above. The ECU 50 detects and stores the in-cylinder pressure at every predetermined crank angle (for example, every 5 degrees), and executes this routine in the exhaust stroke of each cycle. Prior to the processing in step S100 of this routine, absolute pressure correction is performed from the two in-cylinder pressures of the intake stroke according to PV ^κ = constant relationship.

  In the routine shown in FIG. 11, first, in step S100, it is determined whether or not abnormal combustion due to pre-ignition or excessive knock has occurred. The occurrence of pre-ignition is detected when the output voltage of the in-cylinder pressure sensor 16 exceeds a predetermined value. The occurrence of excessive knock is detected when the output value of knock sensor 19 exceeds a predetermined value.

  If it is determined that abnormal combustion has occurred, it is next determined whether or not ΔP is greater than a predetermined value α (step S110). ΔP is an in-cylinder pressure difference calculated on the basis of the deviation between the output voltage in the intake stroke and the output voltage in the exhaust stroke, and the relationship between the output voltage stored in advance in the ECU 50 and the in-cylinder pressure. Further, the predetermined value α is an allowable value of deviation of the output voltage generated in the in-cylinder pressure sensor 16 and is stored in the ECU 50 in advance. The reason why ΔP and α are compared in this step is because the output value of the in-cylinder pressure sensor 16 does not always shift because of abnormal combustion. If ΔP is less than or equal to α, the process of this routine is terminated.

  On the other hand, when ΔP is larger than the predetermined value α, it can be determined that there is a deviation in the output value of the in-cylinder pressure sensor 16. Therefore, the ECU 50 next acquires the crank angle at which the maximum in-cylinder pressure Pmax is detected in the present cycle in which abnormal combustion has occurred (step S120). Specifically, the ECU 50 acquires the crank angle at which the maximum in-cylinder pressure Pmax is detected from the in-cylinder pressure detected and stored for each predetermined crank angle in this cycle.

Next, it is determined whether or not the maximum in-cylinder pressure Pmax> ΔP × β is satisfied (step S130). β is a predetermined value indicating that the influence of correction of ΔP is small as a ratio to the overall in-cylinder pressure, illustrated work, PV ^{κ, and the} like, and is within an allowable range. β is determined by adaptation for each engine 10 and stored in the ECU 50 in advance.

  If the determination condition is satisfied in step S130, the first characteristic control described above is executed. That is, the ECU 50 uniformly corrects ΔP only for the in-cylinder pressure waveform after the maximum in-cylinder pressure Pmax in this cycle in which abnormal combustion has occurred (step S140). This offset correction of ΔP is continued until a cycle where ΔP <α, and is applied during the entire stroke (intake stroke to exhaust stroke) during that cycle.

  On the other hand, if the determination condition is not satisfied in step S130, the above-described second characteristic control is executed. First, the ECU 50 sequentially calculates the amount of change in the in-cylinder pressure between two points at predetermined crank angle intervals after the maximum in-cylinder pressure Pmax (step S150). Specifically, two cylinders, a crank angle at which the maximum in-cylinder pressure Pmax is first detected (crank angle a) and a crank angle (crank angle b) after a predetermined crank angle from the maximum in-cylinder pressure detection crank angle. A change amount of the internal pressure is calculated. Subsequently, it is determined whether or not the amount of change is smaller than a threshold value γ (step S160). γ is a threshold value indicating that the charge is normally removed, and is determined for each in-cylinder pressure sensor 16 by adaptation and stored in the ECU 50 in advance. If the determination condition of step S160 is not satisfied, the ECU 50 sets the crank angle b as a new crank angle a, sets the crank angle after a predetermined crank angle interval from the new crank angle a as a new crank angle b, and The in-cylinder pressure change amount is sequentially calculated, and the determination process in step S160 is continued.

  The ECU 50 stores the crank angle a when the determination condition of step S160 is first established (step S170). This crank angle a is the crank angle immediately before the occurrence of the sensor error. A region from the crank angle to the crank angle a where the maximum in-cylinder pressure Pmax is detected corresponds to a region A in FIG.

  Subsequently, the in-cylinder pressure waveform after the crank angle a is replaced with the in-cylinder pressure waveform at the time of normal combustion in the same operation state as that in the present cycle in which abnormal combustion has occurred (step S180). The in-cylinder pressure waveform during normal combustion under each operating condition is sequentially calculated based on the above-described equations (1) to (3) or stored in advance. Thereafter, the processing of this routine is terminated. From the next routine onward, the offset correction of ΔP is performed until a cycle in which ΔP <α.

  As described above, according to the routine shown in FIG. 11, when the determination condition (Pmax> ΔP × β) in step S130 is satisfied, it is determined that the offset correction amount by ΔP is appropriate, and the first feature Execute dynamic control. Therefore, it is possible to correct the in-cylinder pressure waveform with sufficiently high accuracy in the abnormal combustion occurrence cycle while suppressing the calculation processing amount. Further, according to this routine, the second characteristic control is executed when the determination process of step S130 is not established. By replacing the in-cylinder pressure waveform immediately after the crank angle a immediately before the error occurs in the output value of the in-cylinder pressure sensor 16 with the in-cylinder pressure waveform during normal combustion calculated by the above approximate expression, the in-cylinder pressure waveform is accurately corrected. can do.

  By the way, in the system of Embodiment 1 mentioned above, when the determination condition of step S130 is not satisfied, the second characteristic control (step S150 to step S180) is executed. By the way, when the calculation processing amount is reduced rather than the accuracy, the second characteristic control can be omitted. That is, the process of step S130 may be omitted, and the process of step S140 may be executed after the process of step S120.

  Further, the engine to which the present invention is applied is not limited to the in-cylinder direct injection engine as in the above-described embodiment. The present invention can also be applied to a port injection type engine.

  In the first embodiment described above, the in-cylinder pressure sensor 16 corresponds to the “in-cylinder pressure sensor” in the first invention. Here, the ECU 50 executes the process of step S100, so that the “abnormal combustion determination means” in the first invention executes the process of step S120, and the “maximum combustion determination unit” in the first invention The “cylinder pressure detection position acquisition means” executes the processing of step S130 to step S170 so that the “crank angle acquisition means” in the first aspect of the invention executes the processing of step S180. The “in-cylinder pressure waveform correcting means” in the invention executes the process in step S150, and the “change amount calculating means” in the second invention executes the process in step S160. The “threshold judging means” in step S170 executes the process of step S170, thereby When the “acquisition means” in step 3 executes the process of step S130, the “determination means” in the third aspect of the invention executes the process of step S140, so that “in-cylinder pressure waveform uniform” in the third aspect of the invention. "Correction means" is realized respectively.

Embodiment 2. FIG.
Next, a second embodiment of the present invention will be described with reference to FIGS. The system of the present embodiment can be realized by causing the ECU 50 to execute the routine of FIG. 13 described later in the configuration shown in FIG.

In the present embodiment, absolute pressure correction is performed by PV ^κ = constant relational expression using the output values of the in-cylinder pressure sensor 16 at two points just before the bottom dead center of the exhaust expansion stroke (FIG. 12). FIG. 13 is a flowchart of a control routine executed by the ECU 50 in the present embodiment. This routine is the same as the routine shown in FIG. 11 except that steps S130 to S180 in FIG. 11 are replaced with the processes in steps S230 to S240.

In the routine shown in FIG. 13, after the process of step S120, the absolute pressure is corrected by PV ^κ = a fixed relational expression using the crank angle at the two points just before the exhaust stroke bottom dead center and the output value of the in-cylinder pressure sensor 16. (Step S230). This offset correction is executed for the in-cylinder pressure after the maximum in-cylinder pressure detection crank angle. Two points immediately before the bottom dead center of the exhaust stroke are crank angles before the exhaust valve 35 is opened. The absolute pressure correction is continued until ΔP <α (step S240).

Embodiment 3 FIG.
Next, a third embodiment of the present invention will be described with reference to FIGS. The system of the present embodiment can be realized by causing the ECU 50 to execute a routine of FIG. 15 described later in the configuration shown in FIG.

  In this embodiment, the in-cylinder pressure of the cycle in which abnormal combustion occurs is replaced with the average value of the other cylinders (FIG. 14). FIG. 15 is a flowchart of a control routine executed by the ECU 50 in the present embodiment. This routine is the same as the routine shown in FIG. 11 except that steps S120 to S180 in FIG. 11 are replaced with the processes in steps S320 to S340.

In the routine shown in FIG. 15, after the process of step S110, an average in-cylinder pressure waveform P _ave of other cylinders other than the cylinder in which abnormal combustion has occurred is calculated (step S320). Next, the in-cylinder pressure waveform of the cylinder where the abnormal combustion has occurred is replaced with the average in-cylinder pressure waveform P _ave of the other cylinders (step S330). This replacement is continued until a cycle in which ΔP <α is satisfied (step S340). Therefore, a highly accurate in-cylinder pressure waveform can be obtained even in a cycle in which abnormal combustion occurs.

10 Engine 11 Cylinder 12 Spark plug 14 Fuel injection valve 16 In-cylinder pressure sensor 18 Crank angle sensor 19 Knock sensor 20 Intake passage 24 Air flow meter 26 Throttle valve 28 Throttle opening sensor 30 Intake pressure sensor 32 Intake valve 34 Exhaust passage 35 Exhaust valve 50 ECU
MFB Combustion ratio CA Crank angle KL Load ratio SA Ignition timing VVT Valve timing

Claims (3)

An in-cylinder pressure sensor provided in a cylinder of the internal combustion engine;
Abnormal combustion determining means for determining whether or not abnormal combustion has occurred in the cylinder;
Maximum in-cylinder pressure detection position acquisition means for acquiring a crank angle at which the maximum in-cylinder pressure is detected (hereinafter referred to as a maximum in-cylinder pressure detection crank angle);
Crank angle acquisition means for acquiring a crank angle immediately before an error occurs in the output value of the in-cylinder pressure sensor after the maximum in-cylinder pressure detection crank angle of the cycle in which the abnormal combustion has occurred,
In-cylinder pressure waveform correcting means for replacing the in-cylinder pressure waveform after the crank angle immediately before the error occurs with the in-cylinder pressure waveform during normal combustion under the same operating conditions for the cycle in which the abnormal combustion has occurred ,
The crank angle acquisition means includes
A change amount calculating means for sequentially calculating a change amount of the in-cylinder pressure at every predetermined crank angle interval after the maximum in-cylinder pressure detection crank angle of the cycle in which the abnormal combustion has occurred;
Threshold determination means for determining whether or not the change amount is smaller than a threshold;
Obtaining means for obtaining a crank angle immediately before the change amount is determined to be smaller than a threshold as a crank angle immediately before the error occurs;
Control apparatus for an internal combustion engine, characterized in that it comprises a. Determining means for determining whether or not a calculated value obtained by dividing the maximum in-cylinder pressure by the in-cylinder pressure difference between the in-cylinder pressure in the exhaust stroke and the in-cylinder pressure in the intake stroke is equal to or less than a predetermined value;
When the calculated value is larger than the predetermined value, a cylinder pressure waveform uniform correcting means for uniformly correcting the cylinder pressure after the maximum cylinder pressure generating crank angle of the cycle in which the abnormal combustion has occurred with the cylinder pressure difference. Further comprising
The cylinder pressure waveform correcting means, a control apparatus for an internal combustion engine according to claim 1, characterized in that, said calculated value is performed when it is less than the predetermined value. 3. The control apparatus for an internal combustion engine according to claim 1, wherein the in-cylinder pressure waveform at the time of normal combustion is calculated based on a Wiebe function.

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