JP5772531B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to an internal combustion engine control device, and more particularly to an internal combustion engine control device equipped with an in-cylinder pressure sensor.

Conventionally, for example, in Japanese Patent Application Laid-Open No. 2007-146785, the amount of air taken into a combustion chamber is calculated using a detection value of an in-cylinder pressure sensor (hereinafter also referred to as “CPS”), and ignition is performed using this air amount. Control devices that optimally determine timing have been proposed. The CPS detects the in-cylinder pressure as a relative pressure with respect to the intake pipe pressure. For this reason, in order to use the detected value of CPS in various controls, it is necessary to correct this detected value to an absolute pressure. In the above-described conventional control device, the fact that the PV ^κ value (κ is the specific heat ratio) during the compression stroke after the intake bottom dead center is theoretically constant is used, and the Poisson relational expression that holds in that case is used. The error (absolute pressure correction value Pr) with respect to the absolute pressure of the CPS detection value is calculated by the following equation (1). In the following equation (1), Pc (θ _a ) and Pc (θ _b ) are CPS detection values at two predetermined crank angles θ _a and θ _b during the compression stroke, and V (θ _a ) And V (θ _b ) indicate in-cylinder (combustion chamber) volumes when Pc (θ _a ) and Pc (θ _b ) are detected.
Absolute pressure correction value Pr = (Pc (θ _b ) · V ^κ (θ _b ) −Pc (θ _a ) · V ^κ (θ _a )) / (V ^κ (θ _a ) −V ^κ (θ _b )) (1)

JP 2007-146785 A

In the above equation (1), the absolute pressure correction value is calculated using the detected values of the two CPSs during the adiabatic compression stroke period. For this reason, for example, when the closing timing (IVC) of the intake valve is delayed, two CPS detection values Pc (θ _a ) and Pc (θ _b ) are detected within a short adiabatic compression stroke period. The difference in the in-cylinder volume (V ^κ (θ _a ) −V ^κ (θ _b )) may be extremely small. In this case, since the denominator of the above equation (1) approaches zero, the absolute pressure correction value varies greatly. Thus, under operating conditions in which the adiabatic compression stroke period of the internal combustion engine is shortened, there is a possibility that the absolute pressure correction value cannot be calculated with high accuracy, and improvement has been desired.

  The present invention has been made to solve the above-described problems, and is a control device for an internal combustion engine capable of improving the accuracy of absolute pressure correction for correcting an in-cylinder pressure detection value by an in-cylinder pressure sensor to an absolute pressure. The purpose is to provide.

In order to achieve the above object, a first invention is a control device for an internal combustion engine,
An in-cylinder pressure sensor for outputting an in-cylinder pressure detection value of a predetermined cylinder of the internal combustion engine;
A specifying means for specifying a plurality of combinations of two arbitrary crank angles θ ₁ and θ ₂ during an adiabatic period from IVC to ignition timing of the predetermined cylinder;
In-cylinder pressure detection means for detecting in-cylinder pressure detection values P ₁ and P ₂ at the specified crank angles θ ₁ and θ ₂ using the in-cylinder pressure sensor,
When the cylinder volume of the predetermined cylinder at the crank angle θ ₁ is V ₁ , the cylinder volume of the predetermined cylinder at the crank angle θ ₂ is V ₂ , and the specific heat ratio of the cylinder gas of the predetermined cylinder is κ, the value _P 2 _{V 2} ^kappa from the value obtained by dividing the _{(V 1} ^κ -V ₂ ^κ) to the value obtained by subtracting the value _{P 1 V} 1 ^κ of PV ^kappa in the crank angle theta ₁ of PV ^kappa at the crank angle theta ₂ ( Hereinafter, absolute pressure correction value calculation means for calculating an absolute pressure correction value) for each combination of a plurality of crank angles θ ₁ and θ ₂ specified by the specifying means,
Average value acquisition means for acquiring an average value of a plurality of absolute pressure correction values calculated by the absolute pressure correction value calculation means;
Absolute pressure correction means for correcting the in-cylinder pressure detection value using the average value ,
The specifying means, the crank angle difference of the crank angle theta ₁ and the crank angle theta ₂ is more specific to combinations of the crank angle theta _1, theta ₂ which is a predetermined crank angle period,
An ignition delay period acquisition means for specifying an ignition delay period from the ignition timing of the predetermined cylinder until the air-fuel mixture in the predetermined cylinder is actually ignited;
A heat insulation period changing means for expanding the heat insulation period by the ignition delay period when a heat insulation period from IVC to the ignition timing is smaller than the predetermined crank angle period;
It is characterized by having.

According to a second invention, in the first invention,
In the adiabatic period expanded by the adiabatic period changing means, when the number of combinations of the crank angles θ ₁ and θ _{2 that} can be specified by the specifying means is smaller than a predetermined number, the IVC advance operation and the ignition timing delay It is further characterized by further comprising second adiabatic period changing means for executing at least one of the angular operations.

According to a third invention, in the first or second invention,
A combustion gravity center position calculating means for calculating a combustion gravity center position using the in-cylinder pressure detection value corrected by the absolute pressure correction means;
Crank angle specifying means for specifying a crank angle θ _{Pmax at} which the in-cylinder pressure of the predetermined cylinder is maximized based on the in-cylinder pressure detection value;
And estimating means based on the rules that govern the relationship between the crank angle theta _Pmax and combustion center position, to estimate the combustion centroid position corresponding to the crank angle theta _Pmax,
Determination means for determining whether or not the correction accuracy of the in-cylinder pressure detection value by the absolute pressure correction means is included in a predetermined reference range;
When the correction accuracy is included in the predetermined reference range by the determination unit, the combustion gravity center position is calculated by the combustion gravity center position calculation unit, and when the correction accuracy is not included in the predetermined reference range, Control means for calculating the combustion gravity center position by the estimation means;
Is further provided.

  According to the first aspect of the present invention, in the control device for an internal combustion engine that corrects the in-cylinder pressure detection value detected by the in-cylinder pressure sensor (CPS) using the absolute pressure correction value, the valve closing timing ( A plurality of absolute pressure correction values are calculated during the adiabatic period from IVC) to ignition timing (SA), and the in-cylinder pressure detection value is absolute pressure corrected using the average value. For this reason, according to the present invention, variations in the absolute pressure correction value can be suppressed, so that the correction accuracy of the in-cylinder pressure detection value can be effectively increased.

Further , according to the first invention, a plurality of combinations of the crank angles θ ₁ and θ ₂ are specified in which the crank angle difference between the crank angle θ ₁ and the crank angle θ ₂ is a predetermined crank angle period. As the predetermined crank angle period increases, the variation in the absolute pressure correction value decreases. For this reason, according to the present invention, it is possible to suppress variation in the absolute pressure correction value within a desired range by appropriately setting the predetermined crank angle period.

Further, according to the first aspect of the invention, in the control device for an internal combustion engine that corrects the in-cylinder pressure detection value detected by the in-cylinder pressure sensor (CPS) using the absolute pressure correction value, the intake valve closing of the predetermined cylinder is closed. When the heat insulation period from the timing (IVC) to the ignition timing (SA) is shorter than the predetermined crank angle period, the heat insulation period is expanded by the ignition delay period. There is virtually no problem even if the ignition delay period is included in the thermal insulation period. Therefore, according to the present invention, since the heat insulation period can be effectively extended without impairing drivability, the number of combinations of the crank angles θ ₁ and θ ₂ is increased, and the accuracy of the average value of the absolute pressure correction value is increased. Can be improved.

According to the second invention, when the number of combinations of the crank angles θ ₁ and θ ₂ is smaller than the predetermined number, at least one of the IVC advance operation and the ignition timing retard operation is executed. Is done. For this reason, according to the present invention, the number of combinations of the crank angles θ ₁ and θ ₂ can be increased by forcibly extending the heat insulation period, thereby effectively improving the accuracy of the average value of the absolute pressure correction values. be able to.

According to the third invention, in the calculation of the combustion gravity center position (CA50), when the accuracy of absolute pressure correction of the detected cylinder pressure value can be ensured, the calculation of the combustion gravity center position is performed using the cylinder pressure after the absolute pressure correction. When the absolute pressure correction accuracy cannot be ensured, the combustion gravity center position (CA50) is estimated using the crank angle θ _Pmax specified from the in-cylinder pressure detection value. For this reason, according to the present invention, it is possible to effectively avoid the deterioration of fuel consumption caused by the use of the in-cylinder pressure value with low correction accuracy by the absolute pressure correction for the calculation of the combustion gravity center position (CA50).

It is a schematic block diagram for demonstrating the system configuration | structure as Embodiment 1 of this invention. It is the figure which showed the change of the cylinder internal pressure P, the cylinder internal volume V, and PV ( ^kappa) value in the compression stroke of an internal combustion engine. And spacing of the crank angle _CA 1, _{CA 2,} a diagram showing the relationship between the right side of the above equation (3). It is a flowchart which shows the routine performed in Embodiment 1 of this invention. It is a figure for demonstrating the method of specifying crank angle difference (DELTA) CAb. It is a figure for demonstrating the calculation method of the frequency | count Nc which can be calculated. It is a figure which shows the relationship between the average frequency | count of an absolute pressure correction value, and the variation of an absolute pressure correction value. It is a flowchart which shows the routine performed in Embodiment 2 of this invention. It is a figure which shows the relationship between a crank angle period and the variation of an absolute pressure correction value. It is a figure which shows the relationship between the calculation frequency of the absolute pressure correction value Pr, and the variation of an absolute pressure correction value. It is a figure for demonstrating the calculation method of the frequency | count Nc2 which can be calculated. It is a figure which shows the relationship between ₍ theta) _Pmax and CA50. It is a figure which shows the in-cylinder pressure change with respect to a crank angle. It is a flowchart which shows the routine performed in Embodiment 3 of this invention.

  Embodiments of the present invention will be described below 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. The present invention is not limited to the following embodiments.

Embodiment 1 FIG.
[Configuration of Embodiment 1]
FIG. 1 is a schematic configuration diagram for explaining a system configuration as a first embodiment of the present invention. As shown in FIG. 1, the system according to the present embodiment includes an internal combustion engine 10. The internal combustion engine 10 is configured as a spark ignition type multi-cylinder engine using gasoline as fuel. A piston 12 that reciprocates inside the cylinder of the internal combustion engine 10 is provided. Further, the internal combustion engine 10 includes a cylinder head 14. A combustion chamber 16 is formed between the piston 12 and the cylinder head 14. One end of an intake passage 18 and an exhaust passage 20 communicates with the combustion chamber 16. An intake valve 22 and an exhaust valve 24 are disposed at a communication portion between the intake passage 18 and the exhaust passage 20 and the combustion chamber 16, respectively.

  The intake valve 22 is provided with an intake valve timing control device 36 that variably controls the valve timing. In the present embodiment, as the intake valve timing control device 36, a variable valve timing mechanism that advances or retards the opening / closing timing while keeping the operating angle constant by changing the phase angle of the camshaft (not shown) with respect to the crankshaft. It is assumed that (VVT) is used. Hereinafter, the intake valve timing control device 36 is referred to as “VVT 36”.

  An air cleaner 26 is attached to the inlet of the intake passage 18. A throttle valve 28 is disposed downstream of the air cleaner 26. The throttle valve 28 is an electronically controlled valve that is driven by a throttle motor based on the accelerator opening.

  A spark plug 30 is attached to the cylinder head 14 so as to protrude into the combustion chamber 16 from the top of the combustion chamber 16. The cylinder head 14 is provided with a fuel injection valve 32 for injecting fuel into the cylinder. Furthermore, the cylinder head 14 incorporates an in-cylinder pressure sensor (CPS) 34 for detecting the in-cylinder pressure of each cylinder.

  The system according to the present embodiment includes an ECU (Electronic Control Unit) 40 as shown in FIG. In addition to the in-cylinder pressure sensor 34 described above, various sensors such as a crank angle sensor 42 for detecting the rotational position of the crankshaft are connected to the input portion of the ECU 40. Further, various actuators such as the throttle valve 28, the spark plug 30, and the fuel injection valve 32 described above are connected to the output portion of the ECU 40. The ECU 40 controls the operating state of the internal combustion engine 10 based on various types of input information.

[Operation of Embodiment 1]
(Basic operation of absolute pressure correction)
The CPS 34 is a very effective sensor in that it can directly detect the combustion state in the cylinder. Therefore, the output of the CPS 34 is used as a control parameter for various controls of the internal combustion engine 10. For example, the detected in-cylinder pressure is used for calculation of the amount of intake air taken into the cylinder, calculation of fluctuations in the indicated torque, calculation of calorific value ^PVκ and MFB (combustion mass ratio), and the like. These are used for misfire detection and optimal ignition timing control.

  However, the CPS 34 detects the in-cylinder pressure as a relative pressure with respect to the intake pipe pressure. For this reason, in order to use the detected value of the CPS 34 in various controls, it is necessary to perform absolute pressure correction for correcting the detected value to an absolute pressure. Hereinafter, the basic operation of the absolute pressure correction will be described with reference to FIG.

FIG. 2 is a diagram showing changes in the in-cylinder pressure P, the in-cylinder (combustion chamber 16) volume V, and the PV ^κ value (κ is a specific heat ratio) in the compression stroke of the internal combustion engine 10. 2 is based on the assumption that the intake valve 22 is closed after intake bottom dead center.

As shown in FIG. 2, after IVC, the in-cylinder pressure P increases as the piston 12 rises, and the in-cylinder volume V decreases as the piston 12 rises. In this process, the CPS 34 detects a relative pressure based on the intake pipe pressure. For this reason, the CPS detection value P _CPSDV indicated by the broken line in FIG. 2 deviates from the true value P _TV (solid line) of the in-cylinder pressure indicated by the solid line in the drawing by an amount corresponding to the error Pr.

Between the true value _{P TV} and the detected value _{P CPSDV,} relationship is established in the following equation (2). Therefore, the ECU 40 executes absolute pressure correction for removing the error Pr corresponding to this deviation from the detected value P _CPSDV . Specifically, the PV ^κ value in the adiabatic compression stroke period from IVC to ignition timing (SA) is theoretically constant, and the Poisson that holds in that case is utilized by utilizing the relationship shown in the following equation (2). The error Pr is calculated as the absolute pressure correction value Pr by the following expression (3) using the relational expression: In the following equation (3), P ₁ and P ₂ are detected values of the CPS 34 at two predetermined crank angles during the compression stroke, and V ₁ and V ₂ are values at the time of detecting P ₁ and P ₂ . The in-cylinder volume is shown.
P _TV = P _CPSDV + Pr (2)
^{_{Pr = (P 2 V 2 κ}} -P 1 V 1 κ) / (V 1 κ -V 2 κ) ··· (3)

By using the above equations (2) and (3), the detected value P _CPSDV can be corrected to an absolute pressure without having a configuration for detecting the intake pipe pressure. When the number of cylinders of the internal combustion engine 10 is n (n represents an integer equal to or greater than 2; the same applies hereinafter), the adiabatic compression stroke period of the target cylinder for absolute pressure correction is 1 / n cycle than that of the target cylinder. (720 ° / n) Generally coincides with the adiabatic compression stroke period of the preceding cylinder. Therefore, when the above equation (3) is used, if the detection value P _CPSDV of the cylinder that precedes the target cylinder by 1 / n cycles is applied to P ₁ and P ₂ , the absolute pressure correction of the target cylinder for the absolute pressure correction The value Pr can be estimated with high accuracy.

_Also, if _CA 1 _P 1, P ₂ crank angle at the time of detection, _{respectively, CA 2 (CA 2> CA} 1), CA 2 is the advance side is preferably as close as possible to the ignition timing of the target cylinder, CA ₁ is The retard angle side as close as possible to IVC is preferable. Thus, the spacing of CA _1, CA ₂ and can be expanded to the maximum, it is possible to improve the calculation accuracy of the absolute pressure correction value Pr.

(Characteristic operation of this embodiment)
Next, characteristic operations of the present embodiment will be described with reference to FIGS. During the low load operation of the internal combustion engine 10, the crank angle period from IVC to SA, that is, the adiabatic compression stroke period may be shortened. In this case, as a result, the interval between the crank angles CA ₁ and CA ₂ for detecting the in-cylinder pressures P ₁ and P ₂ is narrowed.

FIG. 3 is a diagram showing the relationship between the interval between the crank angles CA ₁ and CA ₂ and the right side of the above equation (3). As shown in this figure, when the detection interval (CA ₁ -CA ₂ ) is sufficiently long, both (P ₂ V ₂ ^κ− P ₁ V ₁ ^κ ) and (V ₁ ^κ− V ₂ ^κ ) take large values. Therefore, the variation in the calculated value of the absolute pressure correction value Pr is small. However, as (CA ₁ -CA ₂ ) becomes shorter, (P ₂ V ₂ ^κ -P ₁ V ₁ ^κ ) and (V ₁ ^κ -V ₂ ^κ ) also become smaller accordingly, so the absolute pressure correction value Pr The variation of the calculated value gradually increases.

Further, according to the absolute pressure correction operation, the CPS detection values P ₁ and P _{2 at} the two predetermined crank angles CA ₁ and CA ₂ during the compression stroke from IVC to the ignition timing are used. For this reason, in the case where noise is superimposed during detection of P ₁ and P ₂ at these two points, there is a possibility that the absolute pressure correction value Pr is erroneously calculated.

  Therefore, in the system of the present embodiment, in order to suppress the variation in the absolute pressure correction value Pr, the absolute pressure correction value Pr is calculated in a plurality of different periods in the adiabatic compression stroke period from IVC to SA. Absolute pressure correction is performed using the average value. Hereinafter, specific processing of the absolute pressure correction operation will be described in detail with reference to a flowchart.

FIG. 4 is a flowchart showing a routine executed by the ECU 40 in the first embodiment. In the routine shown in FIG. 4, first, a necessary crank angle difference ΔCAb is specified (step 100). FIG. 5 is a diagram for explaining a method of specifying the crank angle difference ΔCAb. As shown in this figure, the variation in the absolute pressure correction value Pr is large in the region where the distance between the crank angles CA ₁ and CA ₂ (CA ₁ -CA ₂ ) is small. Therefore, in the system according to the present embodiment, the crank angle difference ΔCAb in which the variation in the absolute pressure correction value Pr falls within a predetermined range is specified based on the operating condition of the internal combustion engine 10.

Next, the number of possible calculations Nc is calculated (step 102). FIG. 6 is a diagram for explaining a method of calculating the number of possible calculations Nc. As shown in this figure, the number Nc that can be calculated is the maximum that can be calculated in the adiabatic compression stroke period from IVC to SA when the absolute pressure correction value Pr is calculated a plurality of times by advancing the crank angle difference ΔCAb by ΔCA. It is the number of times and can be calculated by the following equation (4) using IVC, SA, ΔCAb, ΔCA. Note that ΔCA is a crank angle measurement resolution (for example, every 10 ° CA), and is a value determined by the specifications of the crank angle sensor 42 and the system.
(IVC−ΔCAb−SA) / ΔCA = Nc (4)

Next, an in-cycle average value Pr _{ave of} the absolute pressure correction value Pr is calculated (step 104). Specifically, Pr ₁ to Pr _{Nc + 1} are calculated as absolute pressure correction values for each ΔCA in the adiabatic compression stroke period from IVC to SA in one cycle. Next, an average value of these (Nc + 1) absolute pressure correction values is calculated as an in-cycle average value Pr _ave of the absolute pressure correction values Pr. FIG. 7 is a diagram illustrating the relationship between the average number of absolute pressure correction values and variations in absolute pressure correction values. Here, the average number of times indicates the number of absolute pressure correction values used to calculate the in-cycle average value Pr _ave . As shown in this figure, the variation in the absolute pressure correction value decreases as the average number increases. For this reason, according to the system of the present embodiment, the calculation accuracy of the absolute pressure correction value can be effectively increased as the number of possible calculations Nc increases.

Next, various combustion state quantities are calculated (step 106). Here, specifically, by using the above equation (2), the true value P _TV of the in-cylinder pressure is calculated. Then, the calculated true value P _TV, change in calculated and indicated torque of the intake air quantity sucked into the cylinder, used for calculations, and the like heating value PV ^kappa and MFB (combustion mass proportion).

  As described above, according to the system of the present embodiment, the correction accuracy can be effectively increased in the absolute pressure correction in which the detected value of the in-cylinder pressure by the CPS 34 is corrected to a true value. Thereby, since a combustion state can be grasped | ascertained correctly, the improvement of the fuel consumption by stable combustion can be anticipated.

  By the way, in the system of the first embodiment described above, the maximum number that can be calculated within the adiabatic compression stroke period from one cycle IVC to SA is calculated as the number Nc that can be calculated. Using the relationship between the average number of pressure correction values and the variation in absolute pressure correction values, the minimum number of times that the variation in absolute pressure correction values falls within a desired range may be used as the number of possible calculations Nc. As a result, it is possible to minimize the calculation load while ensuring the required accuracy of the absolute pressure correction value.

In the first embodiment described above, the crank angle difference ΔCAb corresponds to the “predetermined crank angle period” of the first invention, and the ECU 40 executes the processing of step 100 described above. The “specifying means” in the first invention executes the process of step 104, and the “average value acquisition means” in the first invention executes the process of step 106, thereby The “absolute pressure correcting means” according to the first aspect of the invention executes the processing of step 106 or 116, thereby realizing the “adiabatic period changing means” according to the first aspect of the invention.

Embodiment 2. FIG.
[Features of Embodiment 2]
Next, a second embodiment of the present invention will be described with reference to FIGS. The system of the second embodiment can be realized by executing a routine shown in FIG. 8 described later using the hardware configuration shown in FIG.

  In the system of the first embodiment described above, the crank angle difference ΔCAb specified according to the noise level is smaller than the adiabatic compression stroke period (IVC−SA) from IVC to SA, that is, the starting crank angle of the crank angle difference ΔCAb. The absolute pressure correction is performed on the assumption that both the end crank angle is in the period of the adiabatic compression stroke. However, depending on the operating conditions of the internal combustion engine 10, a situation in which the specified crank angle difference ΔCAb is larger than the adiabatic compression stroke period (IVC−SA) is also assumed.

  Therefore, in the system according to the second embodiment of the present invention, when the crank angle difference ΔCAb is larger than (IVC−SA), the period that can be regarded as the adiabatic compression stroke is considered in consideration of the ignition delay period after ignition. The absolute pressure correction operation is performed to the maximum. Hereinafter, specific processing of the absolute pressure correction operation will be described in detail with reference to a flowchart.

  FIG. 8 is a flowchart showing a routine that the ECU 40 executes in the second embodiment. In the routine shown in FIG. 8, first, a necessary crank angle difference ΔCAb is specified (step 200). Here, specifically, the same processing as the processing in step 100 is executed. Next, it is determined whether or not the adiabatic compression stroke period (IVC-SA) from IVC to SA is greater than or equal to the crank angle difference ΔCAb specified in step 200 (step 202). As a result, when it is recognized that (IVC−SA) ≧ ΔCAb is established, it can be determined that the highly accurate absolute pressure correction value Pr can be calculated within the period of (IVC−SA). . In this case, the process proceeds to the next step, and the processes of steps 102 to 106 are executed (step 204).

On the other hand, if the establishment of (IVC−SA) ≧ ΔCAb is not recognized in step 202, the absolute pressure correction value Pr using the crank angle difference ΔCAb can be calculated within the period of (IVC−SA). It can be judged that it is not possible. In this case, the process proceeds to the next step, and when ΔCA _P2−P1 = (IVC−SA), the absolute pressure correction value Pr calculation count Nth is calculated so that the average value of the absolute pressure correction value Pr becomes the required accuracy. (Step 206). FIG. 9 is a diagram showing the relationship between the crank angle period and the variation in the absolute pressure correction value. As shown in this figure, the variation in the absolute pressure correction value when the crank angle period ΔCA _P2-P1 is (IVC-SA) is larger than that when the crank angle period ΔCA _P2-P1 is ΔCAb. End up. FIG. 10 is a diagram illustrating the relationship between the number of times the absolute pressure correction value Pr is calculated and the variation in the absolute pressure correction value. As shown in this figure, the variation in the absolute pressure correction value decreases as the number of calculations increases. That is, according to such a relationship, the number of calculation times at which the variation in absolute pressure correction value is at a level that can ensure the required accuracy exists. Here, the number of calculations for ensuring the necessary accuracy is specified in accordance with the relationship.

Next, the number of calculations Nc2 is calculated (step 208). Here, when the absolute pressure correction value Pr is calculated a plurality of times by shifting the crank angle difference ΔCA _P2−P1 (= IVC−SA) by ΔCA and calculating the absolute pressure correction value Pr a plurality of times, the number of calculations Nc2 can be calculated from IVC to the actual ignition crank angle CA _Qsta . The maximum number of times that the absolute pressure correction value Pr can be calculated in the adiabatic compression stroke period is shown. FIG. 11 is a diagram for explaining a method of calculating the number of possible calculations Nc2. As shown in this figure, an ignition delay period exists after the ignition timing SA of the internal combustion engine 10. This ignition delay period can be included in the adiabatic compression stroke period. Therefore, in this step, the number of calculations Nc2 is calculated using the following equation (5) using IVC, SA, IVC-SA (= ΔCA _P2-P1 ), and ΔCA. Note that the actual ignition crank angle CA _Qsta can be specified, for example, as the time when the amount of change dQ / dθ in the heat generation amount exceeds a predetermined value, as shown in FIG.
(IVC− (IVC−SA) _{−CA Qsta} ) / ΔCA = Nc2 (5)

Next, it is determined whether or not the number of calculations NC2 + 1 specified in step 208 is greater than or equal to the number of calculations Nth specified in step 206 (step 210). As a result, if the establishment of Nc2 + 1 ≧ Nth is not recognized, it is determined that the calculated number Nth cannot be realized in the adiabatic compression stroke period from IVC to the actual ignition crank angle CA _Qsta, and the process _proceeds to the next step. IVC advance angle control and / or ignition timing SA delay angle control using the VVT 36 are executed in order to forcibly extend the period from SA to SA to a period in which the calculated number Nth can be realized (step 212).

On the other hand, if it is determined in step 210 that Nc2 + 1 ≧ Nth is satisfied, or after the processing in step 212, it is determined that the number of times of calculation Nth is feasible, and the process proceeds to the next step and absolute pressure correction is performed. The in-cycle average value is calculated (step 214). Here, specifically, during the adiabatic compression stroke period from IVC to the actual ignition crank angle CA _Qsta in one cycle, Pr ₁ to Pr Nc _{2 + 1} are calculated as absolute pressure correction values for each _ΔCA . Next, an average value of these (Nc2 + 1) absolute pressure correction values is calculated as an in-cycle average value Pr _ave of the absolute pressure correction value Pr.

Next, various combustion state quantities are calculated (step 216). Here, specifically, by using the above equation (2), the true value P _TV of the in-cylinder pressure is calculated. Then, as a control parameter to true values P _TV according variation calculation and indicated torque of the intake air quantity sucked into the cylinder, the heating value PV ^kappa and MFB (combustion mass proportion), combustion center position (CA50) operations such as Is done. These various combustion state quantities are used for misfire detection and optimal ignition timing control.

  As described above, according to the system of the present embodiment, in the absolute pressure correction in which the detected value of the in-cylinder pressure by the CPS 34 is corrected to a true value, even if the operating condition has a short (IVC-SA) period, the correction is performed. The accuracy can be increased effectively. Thereby, since a combustion state can be grasped | ascertained correctly, the improvement of the fuel consumption by stable combustion can be anticipated.

In the second embodiment described above, the ECU 40 executes the process of step 208, so that the “ignition delay period acquisition means” in the first invention executes the process of step 214. The “second heat insulation period changing means” in the second invention is realized by executing the process of step 212 by the “heat insulation period changing means” in the first invention.

Embodiment 3 FIG.
[Features of Embodiment 3]
Next, Embodiment 3 of the present invention will be described with reference to FIGS. The system of the third embodiment can be realized by executing a routine shown in FIG. 14 described later using the hardware configuration shown in FIG.

  In the system of the first or second embodiment described above, the true value of the in-cylinder pressure is calculated with high accuracy by absolute pressure correction, and is used for calculation of various combustion state quantities. However, it is also assumed that the absolute pressure correction accuracy cannot be ensured during low load operation where the adiabatic compression stroke period from IVC to SA is short, when the noise level deteriorates, or when the sensor gain of CPS 34 is reduced. Is done. In such a case, the calculation accuracy of the combustion center-of-gravity position (CA50) cannot be ensured, and there is a possibility that the fuel efficiency is reduced and the drivability is deteriorated due to the deterioration of the driving conditions.

Therefore, in the system of the third embodiment, when the CA50 cannot be calculated with high accuracy by the in-cylinder pressure after the absolute pressure correction, the CA50 using the crank angle θ _Pmax at the time when the in-cylinder pressure peaks. Will be specified. Specifically, and when the gain of CPS34 is not within a predetermined allowable range, when the variation of the absolute pressure correction value is equal to or higher than the predetermined allowable value, CA50 is estimated based on the theta _Pmax. Figure 12 is a diagram showing a relationship between theta _Pmax and CA50. As shown in this figure, there is a correlation between θ _Pmax and CA50. Therefore, if θ _Pmax can be specified, CA50 can be estimated with high accuracy.

Depending on the operating conditions of the internal combustion engine 10, a plurality of in-cylinder pressure peaks may appear. FIG. 13 is a diagram illustrating a change in in-cylinder pressure with respect to a crank angle. As shown in this figure, when the load factor is high or when the ignition timing is retarded, the peak of the in-cylinder pressure may appear at two locations, that is, when the cylinder is mechanically compressed and when it is burned. In such a case, the crank angle corresponding to the peak of the in-cylinder pressure at the time of combustion is specified as θ _Pmax .

[Specific processing of the third embodiment]
Next, specific processing of the system according to the third embodiment will be described with reference to FIG. FIG. 14 is a flowchart showing a routine that the ECU 40 executes in the third embodiment. In the routine shown in FIG. 14, first, it is determined whether or not the gain of the CPS 34 is within an allowable range (step 300). As a result, when the gain of CPS34 is not within the allowable range, the calculation of CA50 based on the heating value is determined and can not be performed with high accuracy, the process proceeds to the next step, the CA50 based on theta _Pmax Estimated (step 302). Specifically, the crank angle θ _Pmax at which the in-cylinder pressure during combustion peaks is specified based on the detected value of the CPS 34. Next, the CA 50 corresponding to θ _Pmax is specified according to the relationship shown in FIG.

On the other hand, when the gain of the CPS 34 is within the allowable range in the process of step 300, the process proceeds to the next step, and whether or not the variation (for example, the standard deviation σ) of the absolute pressure correction value is smaller than the allowable value. Is determined (step 304). As a result, if the variation in the absolute pressure correction value is greater than or equal to the allowable value, it is determined that the calculation of CA50 based on the heat generation amount cannot be performed with high accuracy, and the routine proceeds to step 302 above and θ _Pmax is reached. CA50 is estimated based on this. On the other hand, if the variation in the absolute pressure correction value is smaller than the allowable value in the process of step 304, it is determined that the CA50 can be calculated with high accuracy based on the calorific value, and the process proceeds to the next step. Then, CA50 is calculated based on the calorific value (step 306). Specifically, the calorific value is calculated using the true value of the in-cylinder pressure subjected to absolute pressure correction, and CA50 is calculated using the calorific value.

As described above, according to the system of this embodiment, when it is not possible to calculate the CA50 using the calorific value with high accuracy, estimation of CA50 using theta _Pmax is performed. Thereby, even if the accuracy of the absolute pressure correction is low, the CA50 can be calculated with high accuracy.

In the third embodiment described above, the ECU 40 executes the process of step 306, so that the “combustion gravity center position calculating means” in the third aspect of the invention executes the process of step 302. the third "crank angle specifying device" and the "estimating means" in the invention of, by executing the process of step 300 or 304, the "determination unit" and "control means" according to the third aspect of the present invention, Each is realized.

DESCRIPTION OF SYMBOLS 10 Internal combustion engine 12 Piston 14 Cylinder head 16 Combustion chamber 18 Intake passage 20 Exhaust passage 22 Intake valve 24 Exhaust valve 26 Air cleaner 28 Throttle valve 30 Spark plug 32 Fuel injection valve 34 Cylinder pressure sensor (CPS)
36 Intake valve timing control device (VVT)
40 ECU (Electronic Control Unit)
42 Crank angle sensor

Claims (3)

An in-cylinder pressure sensor for outputting an in-cylinder pressure detection value of a predetermined cylinder of the internal combustion engine;
A specifying means for specifying a plurality of combinations of two arbitrary crank angles θ ₁ and θ ₂ during an adiabatic period from IVC to ignition timing of the predetermined cylinder;
In-cylinder pressure detection means for detecting in-cylinder pressure detection values P ₁ and P ₂ at the specified crank angles θ ₁ and θ ₂ using the in-cylinder pressure sensor,
When the cylinder volume of the predetermined cylinder at the crank angle θ ₁ is V ₁ , the cylinder volume of the predetermined cylinder at the crank angle θ ₂ is V ₂ , and the specific heat ratio of the cylinder gas of the predetermined cylinder is κ, the value _P 2 _{V 2} ^kappa from the value obtained by dividing the _{(V 1} ^κ -V ₂ ^κ) to the value obtained by subtracting the value _{P 1 V} 1 ^κ of PV ^kappa in the crank angle theta ₁ of PV ^kappa at the crank angle theta ₂ ( Hereinafter, absolute pressure correction value calculation means for calculating an absolute pressure correction value) for each combination of a plurality of crank angles θ ₁ and θ ₂ specified by the specifying means,
Average value acquisition means for acquiring an average value of a plurality of absolute pressure correction values calculated by the absolute pressure correction value calculation means;
Absolute pressure correction means for correcting the in-cylinder pressure detection value using the average value ,
The specifying means, the crank angle difference of the crank angle theta ₁ and the crank angle theta ₂ is more specific to combinations of the crank angle theta _1, theta ₂ which is a predetermined crank angle period,
An ignition delay period acquisition means for specifying an ignition delay period from the ignition timing of the predetermined cylinder until the air-fuel mixture in the predetermined cylinder is actually ignited;
A heat insulation period changing means for expanding the heat insulation period by the ignition delay period when a heat insulation period from IVC to the ignition timing is smaller than the predetermined crank angle period;
A control device for an internal combustion engine, comprising: In the adiabatic period expanded by the adiabatic period changing means, when the number of combinations of the crank angles θ ₁ and θ _{2 that} can be specified by the specifying means is smaller than a predetermined number, the IVC advance operation and the ignition timing delay control apparatus for an internal combustion engine according to claim 1, further comprising a second insulation period changing means for performing at least one operation of the angular behavior. A combustion gravity center position calculating means for calculating a combustion gravity center position using the in-cylinder pressure detection value corrected by the absolute pressure correction means;
Crank angle specifying means for specifying a crank angle θ _{Pmax at} which the in-cylinder pressure of the predetermined cylinder is maximized based on the in-cylinder pressure detection value;
And estimating means based on the rules that govern the relationship between the crank angle theta _Pmax and combustion center position, to estimate the combustion centroid position corresponding to the crank angle theta _Pmax,
Determination means for determining whether or not the correction accuracy of the in-cylinder pressure detection value by the absolute pressure correction means is included in a predetermined reference range;
When the correction accuracy is included in the predetermined reference range by the determination unit, the combustion gravity center position is calculated by the combustion gravity center position calculation unit, and when the correction accuracy is not included in the predetermined reference range, Control means for calculating the combustion gravity center position by the estimation means;
Control apparatus for an internal combustion engine according to claim 1, wherein further comprising a.

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