JP2011236826A - Device for control of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a device for control of an internal combustion engine provided with a structure capable of coping with decline in a compression pressure in a cylinder when the decline arises.SOLUTION: An arithmetic processing device stores a PVcalculation processing for calculating a heat generation amount correlation parameter PV. During fuel-cut of an internal combustion engine, an in-cylinder pressure P is calculated on the basis of an in-cylinder pressure sensor output immediately after an intake valve is closed. An in-cylinder volume V immediately after the intake valve is closed is calculated. The PVimmediately after the intake valve is closed is denoted as "PV". During the fuel-cut of the internal combustion engine, the in-cylinder pressure P is calculated on the basis of the in-cylinder pressure sensor output at a prescribed crank angle θ in a period immediately after the intake valve is closed to the opening of an exhaust valve. The in-cylinder volume V at the prescribed crank angle θ is calculated. The PVat the prescribed crank angle θ is denoted as "PV". A compression pressure reduction rate is calculated on the basis of PV/PV.

Description

  The present invention relates to a control device for an internal combustion engine.

  Conventionally, as disclosed in, for example, Japanese Patent Application Laid-Open No. 2008-291679, a technique for accurately detecting an in-cylinder pressure in a compression stroke is known in order to grasp a combustion state of an internal combustion engine. Yes. Knowing the combustion pressure of the internal combustion engine accurately is important for accurately grasping and judging the combustion state of the internal combustion engine. According to the above conventional technique, the motoring pressure is estimated in consideration of the purge amount in addition to the intake air amount, and the output correction of the in-cylinder pressure sensor is performed based on the estimated value of the motoring pressure. ing. As a result, it is possible to detect the cylinder pressure with high accuracy and thus to grasp the combustion state.

JP 2008-291679 A JP 2007-290663 A

  There is a problem that the pressure (compression pressure) in the cylinder in the compression stroke is reduced (decompressed) due to aged deterioration of the piston ring and the cylinder bore. When such a loss of compression pressure occurs, the air sucked into the cylinder before the compression stroke, that is, until the intake valve is closed, is released with the progress of the compression stroke after the intake valve is closed. End up. Such a loss of compression pressure may adversely affect the control of the internal combustion engine. For example, accurate air-fuel ratio control may be hindered due to changes in the intake air amount.

  The present invention has been made to solve the above-described problems, and provides an internal combustion engine control device having a configuration capable of coping with the occurrence of a loss of compression pressure in a cylinder. Objective.

In order to achieve the above object, a first invention is a control device for an internal combustion engine,
In-cylinder pressure detecting means for detecting the in-cylinder pressure of the internal combustion engine;
In-cylinder volume calculating means for calculating the in-cylinder volume of the internal combustion engine;
The in-cylinder pressure and the in-cylinder volume at the closing timing of the intake valve of the internal combustion engine during the fuel cut of the internal combustion engine, and after the closing timing of the intake valve of the internal combustion engine during the fuel cut of the internal combustion engine, and A reduction rate calculating means for calculating a compression pressure reduction rate in the cylinder of the internal combustion engine based on the in-cylinder pressure and the in-cylinder volume before opening the exhaust valve of the internal combustion engine;
Control means for controlling the internal combustion engine using the compression pressure reduction rate calculated by the reduction rate calculation means;
It is characterized by providing.

The second invention is the first invention, wherein
The decrease rate calculating means includes:
Using the in-cylinder pressure and the in-cylinder volume at the closing timing of the intake valve of the internal combustion engine during the fuel cut of the internal combustion engine, the in-cylinder pressure is P, the in-cylinder volume is V, and the specific heat ratio is κ. First calculating means for calculating a value of P × ^Vκ ;
Using the in-cylinder pressure and the in-cylinder volume at at least one time after the closing timing of the intake valve of the internal combustion engine and before the opening of the exhaust valve of the internal combustion engine during the fuel cut of the internal combustion engine, A second calculating means for calculating a value of P × V ^κ when the internal pressure is P, the in-cylinder volume is V, and the specific heat ratio is κ;
Third calculation means for calculating the compression pressure drop rate based on the ratio of the value of P × ^Vκ determined by the first calculation means and the value of P × ^Vκ determined by the second calculation means;
It is characterized by including.

The third invention is the first or second invention, wherein
The internal combustion engine includes a plurality of cylinders,
The decrease rate calculating means includes:
First obtaining means for obtaining the in-cylinder pressure and the in-cylinder volume at the closing timing of the intake valve of the internal combustion engine during a fuel cut of the internal combustion engine for one of the plurality of cylinders;
For the one cylinder, the in-cylinder pressure and the in-cylinder volume after the closing timing of the intake valve of the internal combustion engine during the fuel cut of the internal combustion engine and before the opening of the exhaust valve of the internal combustion engine are acquired. 2 acquisition means;
Means for calculating a compression pressure reduction rate of the one cylinder based on the in-cylinder pressure and the in-cylinder volume respectively acquired by the first acquisition means and the second acquisition means;
It is characterized by including.

According to a fourth invention, in any one of the first to third inventions,
The control means includes
Estimating means for estimating the in-cylinder pressure of the internal combustion engine based on the in-cylinder pressure detected by the in-cylinder pressure detecting means and the compression pressure reduction rate calculated by the reduction rate calculating means;
Means for controlling the internal combustion engine using the in-cylinder pressure estimated by the estimating means;
It is characterized by including.

Moreover, 5th invention is set in any one of 1st thru | or 4th invention,
The control means includes
An injection amount correction unit that corrects a fuel injection amount of the internal combustion engine based on the compression pressure reduction rate calculated by the reduction rate calculation unit;
Injection amount control means for controlling a fuel injection valve of the internal combustion engine based on the fuel injection amount corrected by the injection amount correction means;
It is characterized by including.

According to a sixth invention, in any one of the first to fifth inventions,
The control means includes
A calorific value calculation means for calculating a calorific value of the internal combustion engine based on an in-cylinder pressure of the internal combustion engine;
A calorific value correction means for correcting the calorific value calculated by the calorific value calculation means based on the compression pressure reduction rate calculated by the reduction rate calculation means;
It is characterized by including.

  According to the first invention, a decrease in the compression pressure in the cylinder can be reflected in the control of the internal combustion engine, and this can be dealt with when a loss of the compression pressure in the cylinder occurs.

According to the second invention, it is possible to calculate the compression pressure reduction rate by utilizing the property that P × V ^κ during fuel cut originally takes a constant value.

  According to the third aspect of the invention, the compression pressure reduction rate can be obtained from the change in the cylinder pressure of a specific cylinder. As a result, when the degree of loss of compression pressure differs among a plurality of cylinders, it is possible to take an appropriate measure for each cylinder.

  According to the fourth aspect of the invention, it is possible to estimate the in-cylinder pressure more accurately by reflecting the loss of the compression pressure, and to control the internal combustion engine.

  According to the fifth aspect, the compression pressure reduction rate can be reflected in the fuel injection amount.

  According to the sixth aspect of the invention, the compression pressure reduction rate can be reflected in the calculation of the calorific value.

It is a figure for demonstrating the detection method of the compression pressure loss in the control apparatus of the internal combustion engine concerning Embodiment 1 of this invention. 7 shows a flowchart of a routine executed by an arithmetic processing unit in the control apparatus for an internal combustion engine according to the second embodiment of the present invention. 7 shows a flowchart of a subroutine executed by an arithmetic processing unit in the control apparatus for an internal combustion engine according to the second embodiment of the present invention.

Embodiment 1 FIG.
The control device according to the first embodiment is suitable as a control device for a vehicle internal combustion engine. The control apparatus according to the first embodiment is used for an internal combustion engine including a plurality of cylinders. This internal combustion engine includes an in-cylinder pressure sensor in each of a plurality of cylinders.

  In the first embodiment, it is assumed that a crank angle sensor that outputs a signal according to the rotation angle of the crankshaft is attached to the internal combustion engine. From the crank angle sensor signal CA, the in-cylinder volume V determined by the engine speed (the number of revolutions per unit time) and the position of the piston can be calculated.

In Embodiment 1, it is assumed that the internal combustion engine is provided with an arithmetic processing unit. This arithmetic processing unit stores processing for analog / digital conversion (AD conversion) in synchronization with the output signal of the in-cylinder pressure sensor in synchronization with the crank angle. By executing this process, the value of the in-cylinder pressure at a desired timing can be detected.
In addition, this arithmetic processing unit stores a PV ^κ calculation process for calculating a parameter PV ^κ that correlates with the heat generation amount. This processing is performed using the in-cylinder pressure P (θ) for each crank angle, the in-cylinder volume V (θ) for each crank angle, and the specific heat ratio κ according to the crank angle θ, and P (θ) × V (θ). ^κ can be calculated.

  The internal combustion engine has other configurations such as various sensors (for example, an engine water temperature sensor), a fuel injection valve, an intake valve, an exhaust valve, and a mechanism for driving these valves (a variable valve mechanism may be used). Is provided. The exhaust system is provided with an exhaust manifold, an exhaust catalyst, an exhaust gas sensor, and the like, and the intake system is provided with various components such as a surge tank, a throttle, and an air cleaner. The arithmetic processing unit processes signals from the sensors and reflects the processing results on the operations of the actuators of the components of the internal combustion engine.

FIG. 1 is a diagram for explaining a method for detecting a compression pressure loss in the control apparatus for an internal combustion engine according to the first embodiment of the present invention. FIG. 1 shows the behavior of a plurality of PV ^κ under different conditions. The PV ^κ behavior during normal combustion is shown at the top of FIG. The waveform of the characteristic 10 has a correlation with the heat generation amount. On the other hand, during fuel cut, since the state is close to the adiabatic compression / expansion stroke, the relationship that PV ^κ takes a constant value holds. Therefore, as in the characteristic 12 in FIG. 1, PV ^κ does not change from the closing of the intake valve (IN valve closing) to the opening of the exhaust valve (EX valve opening). However, when a compression pressure loss due to blow-by occurs, the number of moles of gas in the cylinder decreases. From this, PV ^kappa falls according to the amount of blow-by gas like the characteristic 14 of FIG.

In the first embodiment, first, the cylinder pressure P is calculated based on the cylinder pressure sensor output immediately after the intake valve is closed during the fuel cut of the internal combustion engine. Further, the cylinder volume V immediately after the intake valve is closed is calculated. Hereinafter, PV ^κ immediately after the intake valve is closed calculated based on these values is referred to as “PV ^κ ₁ ”. Further, during the fuel cut of the internal combustion engine, the in-cylinder pressure P is calculated based on the in-cylinder pressure sensor output at a predetermined crank angle θ during the period from when the intake valve is closed to when the exhaust valve is opened. Further, the in-cylinder volume V at the predetermined crank angle θ is calculated. Hereinafter, PV ^κ at a predetermined crank angle θ calculated based on these values is referred to as “PV ^κ _θ ”. The crank angle _θ for calculating PV ^κ _θ is arbitrary.

Next, the compression pressure drop rate is calculated based on the following formula.
Compression pressure drop rate = PV ^κ _θ / PV ^κ ₁ (1)
In the first embodiment, “PV ^κ ₁ ” and “PV ^κ _θ ” are calculated from the in-cylinder pressure sensor output and the in-cylinder volume in the same cylinder.

Focusing on PV ^kappa _theta, gas amount at this time, it is considered to be equivalent to "gas amounts when PV ^kappa upon closing of the intake valve when there is no loss compression pressure is PV ^kappa _theta" it can. That is, a virtual pressure (hereinafter also referred to as “P _m ”) when it is assumed that there is no compression pressure loss when viewed at the closing timing of the intake valve can be expressed by the following equation (2). .
P _m = PV ^κ _θ / V ^κ ₁ (2)

Then, the following equation is established with the actually detected in-cylinder pressure as _PIN .
P _m / P _IN = PV ^κ _θ / PV ^κ ₁ (3)
Since the compression pressure and the intake air amount are in a proportional relationship, the air amount or charging efficiency at the timing of the crank angle θ decreases by PV ^κ _θ / PV ^κ ₁ . The reduction in the air amount causes an influence on the control of the internal combustion engine such as a torque reduction.

  Therefore, for example, when the compression pressure reduction rate obtained by the above equation (1) is equal to or less than a predetermined value, the internal combustion engine is controlled using an in-cylinder pressure sensor that generates an output that is the basis of calculation. You may ban. For example, when the sensitivity correction of the in-cylinder pressure sensor is performed, there is a possibility that erroneous correction is caused under a situation where the compression pressure loss is large. In addition to this, various adverse effects are assumed by continuing the control of the internal combustion engine without considering the compression pressure loss. This is because such harmful effects can be prevented. Alternatively, the user may be notified that an abnormality has occurred in the internal combustion engine. For example, it is possible to notify the user of an abnormality when it is determined that the torque drop is large to some extent in terms of quality, or when it is determined that the risk of start-up deterioration is high.

  As described above, according to the first embodiment, it is possible to reflect the decrease in the compression pressure in the cylinder in the control of the internal combustion engine, and to deal with the case where the compression pressure in the cylinder is lost. Can do.

Further, according to the first embodiment, the compression pressure reduction rate can be calculated using the property that P × V ^κ during fuel cut originally takes a constant value.
For example, Japanese Patent Application Laid-Open No. 2007-290663 discloses a technique for detecting a compression pressure loss by comparing a maximum pressure value Pmax detected by an in-cylinder pressure sensor during a fuel cut among a plurality of cylinders. However, such a technique may be affected by other tolerances related to the compression pressure, such as variations in the compression ratio and phase shift of the variable valve mechanism (VVT).
On the other hand, PV ^κ during closing of the intake valve and the exhaust valve under the fuel cut condition is constant as long as there is no decrease in the compression pressure even if variations occur. Therefore, according to the method according to the first embodiment focusing on the P × V ^kappa during fuel cut, it has the advantage of avoiding the influence of the various variations, such as compression ratio.

Further, according to the first embodiment, the compression pressure reduction rate can be obtained from the change in the cylinder pressure of a specific cylinder. As a result, when the degree of loss of compression pressure differs among a plurality of cylinders, it is possible to take an appropriate measure for each cylinder.
For example, Japanese Patent Application Laid-Open No. 2007-290663 discloses a technique of comparing a maximum pressure value Pmax detected by an in-cylinder pressure sensor during a fuel cut between a plurality of cylinders to detect a compression pressure loss. However, in such a technique, when a compression pressure drop occurs in each of a plurality of cylinders to be compared, even if the relative in-cylinder pressure difference can be specified from the difference in Pmax, the absolute decrease amount Cannot be detected.
On the other hand, the method according to the first embodiment only needs to acquire the sensor value from the cylinder that is the detection target of the compression pressure loss. Since the method according to the first embodiment is a detection method completed in its own cylinder, it is possible to detect the presence or absence of compression pressure loss for a certain cylinder without being affected by the loss of compression pressure of other cylinders.

  In the first embodiment, when the compression pressure drop rate is equal to or less than a predetermined value, it is prohibited to control the internal combustion engine using an in-cylinder pressure sensor that generates an output that is the basis of calculation, Although the user is notified that an abnormality has occurred in the engine, the present invention is not limited to this. The value of the compression pressure drop rate can be used for various purposes in the control of the internal combustion engine. For example, when the in-cylinder pressure is detected based on the output of the in-cylinder pressure sensor, the estimated value of the in-cylinder pressure can be calculated with a higher accuracy by adding the value of the compression pressure drop rate as a correction amount. Good. Thus, the internal combustion engine can be controlled by estimating the more accurate in-cylinder pressure by reflecting the loss of the compression pressure.

Embodiment 2. FIG.
The control device for an internal combustion engine according to the second embodiment is assumed to have a hardware configuration basically similar to that of the first embodiment. However, the second embodiment further includes an EGR (Exhaust Gas Recirculation) device.

When the compression pressure is lost, an error occurs in the in-cylinder pressure during the compression stroke. In determining the basic fuel injection amount (hereinafter referred to as “basic injection amount”) based on the pressure during the compression stroke, it is necessary to correct such an error. Therefore, in the second embodiment, the basic injection amount qb is corrected by the following equation.
After correction qb = PV ^κ ₁ / PV ^κ ₂ × qb before correction (4)
Here, PV ^κ ₂ is P × V ^κ during the compression stroke (for example, BTDC60CA). PV ^κ ₁ is the same as the value acquired in the first embodiment. By performing such correction, an accurate basic injection amount can be set even when a compression pressure loss occurs. As a result, benefits such as suppression of emission deterioration can be enjoyed.

  FIG. 2 shows a flowchart of a routine executed by the arithmetic processing unit in the control apparatus for an internal combustion engine according to the second embodiment of the present invention. According to the routine of FIG. 2, the fuel injection amount control can be performed based on the heat generation amount detected by the in-cylinder pressure sensor. FIG. 3 shows a flowchart of a subroutine executed by the arithmetic processing unit in the control apparatus for an internal combustion engine according to the second embodiment of the present invention. This subroutine represents the processing contents in steps S110 and S112 of the routine of FIG.

  In the routine of FIG. 2, first, processing for detecting the amount of fresh air and EGR introduced into the cylinder is executed (step S100).

Next, a process for calculating the previous heat generation amount Qd is executed (step S102). Further, a process for calculating the basic injection amount qb from the engine speed (Eng speed), the fresh air amount and the target A / F is executed (step S104). In this step, first, the basic injection amount qb before correction is obtained from the engine speed (Eng speed), the fresh air amount and the target A / F. Next, the corrected basic injection amount qb is calculated according to the equation (4).
As described above, the amount of air sealed in the combustion chamber immediately after the intake valve is closed decreases by PV ^κ _θ / PV ^κ _{1 at} the crank angle θ. Here, when detecting the amount of fresh air, it is assumed that a method for detecting the amount of fresh air based on the compression pressure at a predetermined crank angle θ ₂ during the compression stroke is assumed. Crank angle theta ₂ is, for example BTDC60CA. When missing compression pressure is generated, assuming that determines the basic injection quantity qb detects the fresh air amount based on the compression pressure detected at a crank angle theta _2, underestimate compared to that of the original gas volume It will be. Due to this influence, the injection amount becomes insufficient and lean combustion occurs. Therefore, in the second embodiment, such a decrease in the air amount is corrected using the above-described equation (4).

  Subsequent to step S102, no misfire determination is performed (step S106). In this step, it is determined whether or not the heat generation amount Qd is greater than a predetermined value α. When the heat generation amount Qd is larger than the predetermined value α, the following steps S108 to S114 are executed. When the calorific value Qd is less than or equal to the predetermined value α, the subsequent steps S108 to S114 are not performed, and the process proceeds to step S116.

  If it is determined in step S106 that the heat generation amount Qd is greater than the predetermined value α, feedback to the injection amount based on the heat generation amount is performed (step S108).

Next, an ideal heat generation amount Qt at the time of previous combustion is calculated (step S110), and an ignition timing influence correction to the heat generation amount Qd at the time of previous combustion (step S112) is performed.
Here, the processing contents in steps S110 and S112 will be described with reference to FIG. First, the ideal heat generation amount Qt is calculated from the previous engine speed and the fresh air amount (step S200). This ideal heat generation amount Qt is the target heat generation amount. Next, a process for correcting Qt based on the target A / F value (step S202), a process for correcting Qt based on the engine water temperature (step S204), and Qt based on the deviation between the MBT 50% combustion point and the target 50% combustion point. A process of correcting (step S206) and a process of correcting Qt based on the detected EGR rate (step S212) are executed. The ideal heat generation amount Qt (target heat generation amount) is calculated by the processes in steps S200 to S212.
Next, based on the deviation between the previous target 50% combustion point and the detected 50% combustion point, the calorific value Qd at the previous combustion is corrected (step S214).
With the above processing, the ideal heat generation amount Qt (target heat generation amount) is calculated and the previous combustion heat generation amount Qd is corrected.

  Next, a fuel injection amount correction amount qh is calculated based on the deviation between Qt and Qd (step S114).

  Thereafter, a final value of fuel injection is calculated by obtaining a total value of the basic injection amount qb obtained in step S104 and the correction amount qh obtained in step S114 (step S116). Thereafter, the current routine ends.

Embodiment 3 FIG.
The control device for an internal combustion engine according to the third embodiment is assumed to have a hardware configuration basically similar to that of the second embodiment.

When compression pressure loss occurs, the amount of heat generated during combustion decreases. In consideration of the decrease in the heat generation amount, the ideal heat generation amount when performing feedback correction of the fuel injection amount is corrected. That is, using the P × V ^kappa immediately before the opening of the exhaust valve, according to the following formula (5), it was decided to correct the Qt.
After correction Qt = PV ^κ ₃ / PV ^κ ₂ × Qt before correction (5)
Here, PV ^κ ₃ is the amount of heat generated immediately before the exhaust valve is opened. In the third embodiment, specifically, the crank angle θ ₃ for detecting the in-cylinder pressure for calculating the calorific value is ATDC60CA, and the value of P × V ^κ applied to the crank angle θ ₃ is PV ^κ ₃ . . As a result, even when a compression pressure loss occurs, a target heat generation amount (ideal heat generation amount) can be set in consideration of a decrease in the heat generation amount due to blow-by, and accurate fuel injection amount control can be performed. As a result, benefits such as suppression of emission deterioration can be enjoyed.

  Hereinafter, the specific process according to the third embodiment will be described with reference to FIGS. 2 and 3 according to the specific process according to the second embodiment. The routine executed by the arithmetic processing unit of the internal combustion engine in the third embodiment is basically the same as that in the second embodiment. However, the content of the process in step S200 in FIG. 3 is different between the second embodiment and the third embodiment.

  Also in the third embodiment, the arithmetic processing unit executes the process of step S100 transition shown in FIG. Here, in the processing relating to steps S110 and S112, the contents of the subroutine relating to FIG. 3 are executed.

  In step S200 in FIG. 3, in the third embodiment, first, the ideal heat generation amount Qt before correction is calculated from the previous engine speed and the fresh air amount. Next, the calculation of the above equation (5) is performed on the uncorrected ideal heat generation amount Qt to calculate the corrected ideal heat generation amount Qt.

As described above, the amount of air sealed in the combustion chamber immediately after the intake valve is closed decreases by PV ^κ _θ / PV ^κ _{1 at} the crank angle θ. Here, when detecting the amount of fresh air, it is assumed that a method for detecting the amount of fresh air based on the compression pressure at a predetermined crank angle θ ₂ during the compression stroke is assumed. Crank angle theta ₂ is, for example BTDC60CA. When missing compression pressure is generated, assuming that determines the ideal heating value Qt detects the fresh air amount based on the compression pressure detected at a crank angle theta _2, underestimate compared to that of the original gas volume It will be. Due to this influence, the injection amount becomes insufficient and lean combustion occurs. Considering this point, in calculating the ideal heat generation amount, it is conceivable to correct the air amount decrease by the following equation (6).
Qt after correction = PV ^κ ₁ / PV ^κ ₂ × Qt before correction (6)
On the other hand, the amount of heat generated after the combustion is also reduced by blow-by. If the crank angle for detecting the amount of heat generated after the end of combustion is θ ₃ , the amount of heat detected by the in-cylinder pressure sensor is also reduced by the following equation (7).
Rate of decrease in calorific value = PV ^κ ₃ / PV ^κ ₁ (7)
In consideration of this point, it is preferable to correct the ideal heat generation amount Qt, which is a target value. Therefore, in the third embodiment, the correction is performed by the following equation (8) in consideration of both the equations (6) and (7).
After correction Qt = (PV ^κ ₁ / PV ^κ ₂ ) × (PV ^κ ₃ / PV ^κ ₁ ) × Qt before correction
= PV ^κ ₃ / PV ^κ ₂ × Qt before correction (8)
The above-described equation (5) is the same as this equation (8).

  In step S200, the corrected Qt calculated according to the above equation (5) is further corrected by the processes in steps S202 to S212. As a result, the ideal heat generation amount Qt according to the third embodiment is calculated.

  Thereafter, in the same manner as in the second embodiment, in step S214, a process for correcting the heat generation amount Qd at the previous combustion is executed, and the routine of FIG. 3 ends. Thereafter, the routine of FIG. 2 is executed as in the second embodiment.

  In the third embodiment, the correction of the basic injection amount qb described in the second embodiment may not be performed in the process of step S104 according to the flowchart of FIG. That is, only the calorific value Qt correction method according to the third embodiment may be performed alone.

10 Usually PV ^kappa behavioral characteristics qb basic injection quantity Qd calorific value at PV ^kappa behavior characteristics 12 of the fuel-cut time and normal PV ^kappa behavioral characteristics 14 fuel cut time and loss compression pressure during combustion qh correction amount Qt ideal heating value

Claims (6)

In-cylinder pressure detecting means for detecting the in-cylinder pressure of the internal combustion engine;
In-cylinder volume calculating means for calculating the in-cylinder volume of the internal combustion engine;
The in-cylinder pressure and the in-cylinder volume at the closing timing of the intake valve of the internal combustion engine during the fuel cut of the internal combustion engine, and after the closing timing of the intake valve of the internal combustion engine during the fuel cut of the internal combustion engine, and A reduction rate calculating means for calculating a compression pressure reduction rate in the cylinder of the internal combustion engine based on the in-cylinder pressure and the in-cylinder volume before opening the exhaust valve of the internal combustion engine;
Control means for controlling the internal combustion engine using the compression pressure reduction rate calculated by the reduction rate calculation means;
A control device for an internal combustion engine, comprising: The decrease rate calculating means includes:
Using the in-cylinder pressure and the in-cylinder volume at the closing timing of the intake valve of the internal combustion engine during the fuel cut of the internal combustion engine, the in-cylinder pressure is P, the in-cylinder volume is V, and the specific heat ratio is κ. First calculating means for calculating a value of P × ^Vκ ;
Using the in-cylinder pressure and the in-cylinder volume at at least one time after the closing timing of the intake valve of the internal combustion engine and before the opening of the exhaust valve of the internal combustion engine during the fuel cut of the internal combustion engine, A second calculating means for calculating a value of P × V ^κ when the internal pressure is P, the in-cylinder volume is V, and the specific heat ratio is κ;
Third calculation means for calculating the compression pressure drop rate based on the ratio of the value of P × ^Vκ determined by the first calculation means and the value of P × ^Vκ determined by the second calculation means;
The control apparatus for an internal combustion engine according to claim 1, comprising: The internal combustion engine includes a plurality of cylinders,
The decrease rate calculating means includes:
First obtaining means for obtaining the in-cylinder pressure and the in-cylinder volume at the closing timing of the intake valve of the internal combustion engine during a fuel cut of the internal combustion engine for one of the plurality of cylinders;
For the one cylinder, the in-cylinder pressure and the in-cylinder volume after the closing timing of the intake valve of the internal combustion engine during the fuel cut of the internal combustion engine and before the opening of the exhaust valve of the internal combustion engine are acquired. 2 acquisition means;
Means for calculating a compression pressure reduction rate of the one cylinder based on the in-cylinder pressure and the in-cylinder volume respectively acquired by the first acquisition means and the second acquisition means;
The control apparatus for an internal combustion engine according to claim 1 or 2, characterized by comprising: The control means includes
Estimating means for estimating the in-cylinder pressure of the internal combustion engine based on the in-cylinder pressure detected by the in-cylinder pressure detecting means and the compression pressure reduction rate calculated by the reduction rate calculating means;
Means for controlling the internal combustion engine using the in-cylinder pressure estimated by the estimating means;
The control device for an internal combustion engine according to any one of claims 1 to 3, wherein The control means includes
An injection amount correction unit that corrects a fuel injection amount of the internal combustion engine based on the compression pressure reduction rate calculated by the reduction rate calculation unit;
Injection amount control means for controlling a fuel injection valve of the internal combustion engine based on the fuel injection amount corrected by the injection amount correction means;
The control apparatus for an internal combustion engine according to any one of claims 1 to 4, further comprising: The control means includes
A calorific value calculation means for calculating a calorific value of the internal combustion engine based on an in-cylinder pressure of the internal combustion engine;
A calorific value correction means for correcting the calorific value calculated by the calorific value calculation means based on the compression pressure reduction rate calculated by the reduction rate calculation means;
The control apparatus for an internal combustion engine according to claim 1, comprising:

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