JP2010127103A - Control device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control device of an internal combustion engine which can accurately determine the deterioration of a combustion state due to afterburning of the internal combustion engine. <P>SOLUTION: The device includes: an MFB acquiring means for acquiring a ratio (MFB) of total mass of fuel burned during a period from a start crank angle θs before starting normal combustion to a prescribed crank angle θm with respect to a total mass of fuel burned during a period from the start crank angle θs to an end crank angle θe after completing the combustion in a combustion chamber 16 of an internal combustion engine 10, an MFB increase rate acquiring means for acquiring an increase rate (inclination (a)) of MFB in a period when the prescribed crank angle θm is from the end crank angle θe (MFB 100%) onward; and a determination means for determining the deterioration of a combustion state due to afterburning in a combustion chamber 16 when the inclination (a) is larger than a prescribed threshold value. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an internal combustion engine control device, and more particularly to an internal combustion engine control device that determines a combustion state of an internal combustion engine.

  Conventionally, for example, in JP 2007-113396 A, the position of the center of gravity of the total heat generation amount in the combustion section from the start of combustion to the end of combustion of each cylinder is detected, and based on the position of the center of gravity of this total heat generation amount, A combustion state determination device for determining the combustion state of each cylinder is disclosed. In this device, the deviation between the average value of the total heat generation center of gravity position detected in the past predetermined period and the current total heat generation amount center of gravity position is calculated, and the frequency at which this deviation becomes a predetermined value or more is greater than or equal to the predetermined value. When it becomes, it is determined that the combustion state has deteriorated.

JP 2007-113396 A Japanese Unexamined Patent Publication No. 7-180598 JP-A-8-128378 JP 2008-223688 A

  However, the total heat generation amount in the combustion section changes not only when the combustion state deteriorates due to afterburning or the like, but also when, for example, an ignition delay occurs. For this reason, the above-described conventional apparatus that simply determines the deterioration of the combustion state based on the degree of change in the center of gravity of the total heat generation amount cannot distinguish between a simple ignition delay and the deterioration of the combustion state due to afterburning. There was a risk of causing a judgment.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a control device for an internal combustion engine that can accurately determine the deterioration of the combustion state due to the afterburning of the internal combustion engine. .

In order to achieve the above object, a first invention is a control device for an internal combustion engine,
From the start crank angle to the predetermined crank angle with respect to the total mass of fuel burned in the period from the start crank angle before normal combustion starts in the combustion chamber of the internal combustion engine to the end crank angle after the combustion ends. MFB acquisition means for acquiring a ratio (hereinafter referred to as MFB) of the total mass of fuel burned in a period;
MFB increase rate acquisition means for acquiring an increase rate of the MFB in a period in which the predetermined crank angle is after the end crank angle;
Determination means for determining deterioration of combustion in the combustion chamber when the increase rate is greater than a predetermined rate;
It is characterized by providing.

According to a second invention, in the first invention,
The MFB increase rate acquisition means acquires the increase rate of the MFB in a period from the end crank angle to a crank angle immediately before the exhaust valve opens.

According to a third invention, in the first or second invention,
The internal combustion engine is a spark ignition type internal combustion engine provided with a spark plug,
Ignition timing correction means for correcting the ignition timing based on the MFB at the specific crank angle;
Limiting means for limiting, when the determination means determines combustion deterioration in the combustion chamber, MFB at the time of the combustion deterioration is reflected in the ignition timing correction;
It is characterized by including.

A fourth invention is any one of the first to third inventions,
The internal combustion engine is a spark ignition type internal combustion engine provided with a spark plug,
The apparatus further comprises a deterioration determining means for determining whether or not the spark plug is deteriorated based on the rising rate.

A fifth invention is the fourth invention,
The deterioration determination means includes combustion deterioration rate acquisition means for acquiring a rate at which combustion deterioration in the combustion chamber is determined when the determination means is executed a plurality of times, and when the combustion deterioration rate is greater than a predetermined rate, It is determined that the spark plug has deteriorated.

According to a sixth invention, in the fourth invention,
The deterioration determination means includes average value acquisition means for acquiring an average value of the increase ratio when the MFB increase ratio acquisition means is executed a plurality of times, and when the average value is greater than a predetermined value, the spark plug is It is characterized by determining that it has deteriorated.

  The ratio of the total mass of fuel burned during the period up to the predetermined crank angle (MFB: Mass Fraction Burned) to the total mass of fuel burned during the period from the start crank angle to the end crank angle is the combustion state up to the predetermined crank angle. It becomes an index. According to the first invention, when the MFB after the end crank angle, that is, the MFB in the period where the combustion should have ended if it is normal combustion, is rising, the afterburning occurs. Judgment can be made. For this reason, according to the present invention, it is possible to accurately determine the deterioration of combustion due to afterburning based on the rate of increase in MFB after the end crank angle.

  The period from the end crank angle to the crank angle just before the exhaust valve opens belongs to the heat insulation stroke in which the combustion chamber is sealed. For this reason, according to 2nd invention, the raise of MFB resulting from afterburning can be determined accurately.

  According to the third invention, when it is determined that the combustion is deteriorated, it is possible to prevent the MFB at the time of the deterioration of the combustion from being reflected in the ignition timing correction. For this reason, according to the present invention, it is possible to effectively avoid a situation in which the correction value of the subsequent ignition timing is significantly changed due to sudden combustion deterioration due to afterburning.

  When the increase rate of MFB after the end crank angle is large, the deterioration of the spark plug is doubtful. For this reason, according to the fourth aspect of the present invention, it is possible to efficiently detect the deterioration of the spark plug that causes the deterioration of combustion based on the increase rate.

  When it is determined that the combustion is deteriorated, there is a high possibility that the spark plug has deteriorated. For this reason, according to the fifth aspect of the invention, it is possible to accurately determine the deterioration of the spark plug based on the determination rate of the deterioration of combustion.

  When the average value of the rate of increase in MFB after the end crank angle is large, there is a high possibility that the spark plug has deteriorated over time. For this reason, according to the sixth aspect, it is possible to accurately determine the deterioration of the spark plug based on the average value of the increase ratio.

  Several 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 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.

  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. Further, the cylinder head 14 incorporates an in-cylinder pressure sensor 34 for detecting the in-cylinder pressure.

  The system according to the present embodiment includes an ECU (Electronic Control Unit) 40 as shown in FIG. Various sensors such as a crank angle sensor 42 for detecting the rotational position of the crankshaft and the in-cylinder pressure sensor 34 described above 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]
(Optimum ignition timing control using MFB)
In the present embodiment, optimum ignition timing control (hereinafter referred to as “MBT”) using a mass combustion ratio (Mass Fraction Burned, hereinafter referred to as “MFB”), which is the ratio of the fuel burned out of the fuel flowing into the combustion chamber 16. Control). In the MBT control, the ignition timing by the spark plug 30 is controlled in order to optimally control the combustion state in the combustion chamber 16. More specifically, since MFB is a parameter that reflects the combustion state in the combustion chamber 16, by controlling the ignition timing to advance or retard so that this MFB matches the target MFB, the desired combustion state Can be realized.

  FIG. 2 is a characteristic diagram for explaining a change in MFB in the MBT control. As shown in this figure, in the MBT control, a start crank angle θs corresponding to the start of the combustion stroke, an end crank angle θe corresponding to the end of the combustion stroke, and a predetermined crank angle θm in the middle of the combustion stroke are used. . As these crank angles, for example, the start crank angle θs is set to −60 ° CA, the end crank angle θe is set to + 60 ° CA, and the predetermined crank angle θm is set to + 8 ° CA on the basis of the explosion top dead center. Note that the present invention is not limited to these angles, and the crank angles θs, θe, and θm may be appropriately set to other angles.

As can be seen from the definition, MFB is 0% at the start of the combustion stroke of normal combustion (crank angle θs), and 100% at the end of the combustion stroke (crank angle θe). In the MBT control, the combustion state is controlled so that the MFB at the intermediate crank angle θm matches the target MFB (for example, 50 to 60%). Here, MFB can be calculated by the following equation (1) using PV ^κ θs, PV ^κ θe, and PV ^κ θm that are calculated values PV ^κ at the respective crank angles θs, θe, and θm.
^{MFB (%) = (PV κ} θm-PV κ θs) / (PV κ θe-PV κ θs) ··· (1)

  In the above equation (1), P represents the pressure detected by the in-cylinder pressure sensor 34, V represents the in-cylinder volume in the combustion chamber 16, and κ represents the specific heat ratio. The in-cylinder pressure P may be estimated based on the operating state of the internal combustion engine 10 without using the in-cylinder pressure sensor 34. The in-cylinder volume V is uniquely determined according to the crank angle θ, and the relationship between the two is stored in advance in the ECU 40 as map data or a function expression. Furthermore, since the specific heat ratio κ is substantially constant (approximately 1.32) in the stoichiometric gasoline mixture, it is assumed that this value is also stored in the ECU 40 in advance.

  Next, specific processing of MBT control will be described in detail with reference to FIG. FIG. 3 is a flowchart showing a routine for the ECU 40 to execute the MBT control. In the routine shown in FIG. 3, first, the MFB (hereinafter referred to as “MFB8”) when the predetermined crank angle θm is + 8 ° CA is calculated for each cylinder (step 100). Here, specifically, the in-cylinder pressure P detected by the in-cylinder pressure sensor 34 is substituted into the above equation (1), and the MFB 8 is calculated.

  Next, a deviation Δ between MFB8 and the target value of MFB8 is calculated (step 102). Specifically, the deviation between the MFB 8 calculated in step 100 and the target value of MFB 8 stored in the ECU 40 is calculated. As the target value of the MFB 8, a preset value is used as the MFB 8 when optimum combustion is performed in the combustion chamber 16.

  Next, a smoothing process is performed on the deviation Δ (step 104). Specifically, the average value of the deviation Δ of the routine for the past five times is acquired as the deviation Δ after the annealing process.

  Next, in the routine shown in FIG. 3, the ignition timing is corrected (step 106). The ECU 40 stores an ignition timing correction amount corresponding to the deviation Δ. Specifically, the ignition timing correction amount corresponding to the deviation Δ obtained in step 104 is specified and the ignition timing correction is executed.

  As described above, in the MBT control, the ignition timing is controlled so that the MFB 8 coincides with the target value of the MFB 8. Therefore, even when an ignition delay or the like occurs, a good combustion state can be maintained.

(Characteristic operation of this embodiment)
Next, characteristic operations of the present embodiment will be described with reference to FIGS. FIG. 4 is a diagram showing changes in MFB in each combustion state. In this figure, the solid line L1 shows the change in MFB when normal combustion is performed, the alternate long and short dash line L2 shows the change in MFB when ignition delay occurs, and the dotted line L3 shows the combustion state deteriorated by afterburning. The change of MFB in each case is shown. As shown in this figure, when comparing MFB8 in each MFB, MFB8 at the time of ignition delay and MFB8 at the time of deterioration of combustion due to afterburning have the same value. That is, the MFB 8 alone cannot distinguish between ignition delay and combustion deterioration due to afterburning.

  Here, when the ignition delay occurs, it is desirable to execute the MBT control logic and correct the ignition timing to the advance side. On the other hand, when the combustion state suddenly deteriorates due to afterburning, it is desirable not to execute the MBT control logic in order to avoid a situation in which the subsequent ignition timing correction value changes significantly. For this reason, in the said MBT control which cannot distinguish these, there exists a possibility that a combustion state cannot be controlled optimally.

  Therefore, in the present embodiment, focusing on the MFB change after the end crank angle θe, a simple ignition delay is distinguished from combustion deterioration due to afterburning. FIG. 5 is a diagram showing changes in MFB in each combustion state. In this figure, the solid line L1 shows the change in MFB when normal combustion is performed, the alternate long and short dash line L2 shows the change in MFB when ignition delay occurs, and the dotted line L3 shows the combustion state deteriorated by afterburning. The change of MFB in each case is shown.

  As shown in this figure, the MFB in the solid line L1 and the alternate long and short dash line L2 is substantially constant (100%) after the end crank angle θe. This indicates that in the case of normal combustion or combustion due to ignition delay, combustion has substantially ended by the end crank angle θe. On the other hand, as indicated by the dotted line L3, the MFB when the combustion state is deteriorated by the afterburning also increases after the end crank angle θe. This indicates that combustion continues after the end crank angle θe.

  Thus, the MFB after the end crank angle θe is an index of occurrence of combustion deterioration due to afterburning. Therefore, in the present embodiment, the MFB gradient a during the period from the end crank angle θe to the opening of the exhaust valve (crank angle 60 ° to 110 ° in the figure) is calculated, and this gradient a is a predetermined value. When it is larger than the value, the deterioration of combustion due to afterburning is determined. As a result, it is possible to effectively distinguish between simple ignition delay and deterioration of combustion due to afterburning.

  Further, in the system according to the present embodiment, when the combustion deterioration due to afterburning is determined, the ignition timing correction value is not calculated using the MFB 8 at the time of such combustion deterioration, that is, the ignition timing correction value in the previous routine is not calculated. It is assumed that MBT control is executed by using. Thereby, since the situation where the ignition timing correction value of MBT control changes significantly can be avoided, the situation where the precision of MBT control falls can be suppressed.

[Specific Processing in First Embodiment]
Next, specific processing of the first embodiment will be described with reference to FIG. FIG. 6 is a flowchart showing a routine executed by the ECU 40.

In the routine shown in FIG. 6, first, an average value a _AVE and a standard deviation σ of the MFB gradient a after the end crank angle θe (MFB 100%) are calculated (step 200). Specifically, the average value a _AVE and the standard deviation σ are calculated based on the slope a calculated in step 202 of the routine for the past 100 times.

  Next, the inclination a in this routine is calculated (step 202). Specifically, the increase amount per unit crank angle of MFB in the crank angle period from the end crank angle θe (MFB 100%) to immediately before the exhaust valve opens is calculated as the slope a.

Next, it is determined whether or not the slope a is smaller than the average value a _AVE + 3σ (step 204). The region of the average value a _AVE ± 3σ is a region to which 99.74% belongs in the normal distribution. Specifically, it is determined whether or not the current inclination a calculated in step 202 belongs to the 3σ region. As a result, when it is recognized that the inclination a <average value a _AVE + 3σ is established, it is determined that an abnormal increase in the inclination a, that is, combustion deterioration due to afterburning has not occurred, and the process proceeds to the next step. The MBT control logic is executed (step 206). Here, specifically, the same processing as in steps 100 to 106 is executed.

On the other hand, when the establishment of the slope a <average value a _AVE + 3σ is not recognized in the above step 204, it is determined that an abnormal rise in the slope a, that is, combustion deterioration due to afterburning, has occurred. The routine proceeds to step, and the ignition timing correction similar to the MBT control in the previous routine is executed without executing the MBT control logic in this routine (step 208).

  As described above, according to the system of the present embodiment, based on the MFB inclination a after the end crank angle θe (MFB 100%), the combustion state is clearly distinguished from the combustion deterioration caused by afterburning and the ignition delay. Can be determined. As a result, it is possible to effectively avoid the situation where the MBT control logic is not executed for the ignition delay or the situation where the MBT control logic is executed for the deterioration of combustion due to afterburning. Effectively.

  By the way, in the above-described embodiment, the change rate of MFB in the crank angle period from the end crank angle θe to the crank angle immediately before the exhaust valve opens is calculated as the slope a. The method is not limited to this. That is, as long as it is within the crank angle period after the end crank angle θe and immediately before the exhaust valve opens, the change rate of the MFB in different periods may be calculated as the slope a.

In the above-described embodiment, the deterioration of combustion due to afterburning is determined based on whether or not the slope a belongs to the 3σ region of the average value a _AVE , but the determination value is not limited to this. That is, as long as the inclination a when the combustion deterioration due to afterburning occurs can be determined separately from other combustion states, a fixed value set in advance may be used, or another determination value may be used. It is good.

  In the first embodiment described above, the ECU 40 executes the process of step 202, so that the “MFB increase rate acquisition means” in the first invention executes the process of step 204. The “determination means” in the first invention is realized.

  In the first embodiment described above, the ECU 40 executes the process of step 206, so that the “ignition timing correction means” in the third aspect of the invention executes the process of step 208. The “limiter” in the third aspect of the invention is realized.

Embodiment 2. FIG.
[Features of Embodiment 2]
Next, the features of the second embodiment will be described with reference to FIG. The second embodiment can be realized by executing a routine shown in FIG. 7 to be described later using the hardware configuration shown in FIG.

  In the case where combustion deterioration due to afterburning frequently occurs, there is a high possibility that the spark plug 30 has deteriorated. Therefore, in the system of the second embodiment, the deterioration determination of the spark plug 30 is executed based on the MFB gradient a after the end crank angle θe (MFB 100%). More specifically, in the abnormality determination of the first embodiment described above, the case where it is determined that the combustion is deteriorated due to afterburning and the case where it is determined that it is normal are counted, respectively, and the probability of the deterioration of combustion due to afterburning is predetermined. When the threshold value is exceeded, deterioration of the spark plug is determined. Thereby, it is possible to detect deterioration of the spark plug 30 at an early stage without requiring a special configuration.

[Specific Processing of Embodiment 2]
Next, specific processing of the second embodiment will be described with reference to FIG. FIG. 7 is a flowchart illustrating a routine in which the ECU 40 performs the deterioration determination of the spark plug 30.

In the routine shown in FIG. 7, first, an average value a _AVE and standard deviation σ of the MFB gradient a after the end crank angle θe (MFB 100%) and the standard deviation σ are calculated (step 300). Next, the inclination a in this routine is calculated (step 302). Next, it is determined whether or not the slope a is smaller than the average value a _AVE + 3σ (step 304). Specifically, the same processing as in steps 200 to 204 is executed.

If it is determined in step 304 that the inclination a <average value a _AVE + 3σ is established, it is determined that an abnormal increase in the inclination a, that is, combustion deterioration due to afterburning has not occurred, and the next step is performed. Then, the combustion normal counter m is counted up (step 306). Next, MBT control logic is executed (step 308). Here, specifically, the same processing as in step 206 is executed.

On the other hand, in the above-described step 304, when the establishment of the inclination a <average value a _AVE + 3σ is not recognized, it is determined that an abnormal increase in the inclination a, that is, combustion deterioration due to afterburning has occurred. The routine proceeds to step, where the combustion deterioration counter n is counted up (step 310).

In the routine shown in FIG. 7, next, the combustion deterioration probability α is calculated (step 312). Specifically, the normal combustion counter m counted up in step 306 and the combustion deterioration counter n counted up in step 310 are substituted into the following equation (2) to calculate the combustion deterioration probability α. Is done.
α = (n / m) × 100 (2)

  Next, it is determined whether or not the combustion deterioration probability α is smaller than 1 (step 314). Here, the determination value 1 is a value set in advance as a threshold value for determining the deterioration of the spark plug 30. As a result, if it is confirmed that α <1 is established, it is determined that the spark plug 30 has not deteriorated, the process proceeds to the next step, and the MBT control logic is not executed in this routine, and the previous step is performed. The ignition timing correction similar to the MBT control in the routine is executed (step 316). Here, specifically, the same processing as in step 208 is executed.

  On the other hand, if the establishment of α <1 is not recognized in step 314, it is determined that the combustion deterioration probability α is high, and the deterioration of the spark plug 30 is determined (step 318).

  As described above, according to the system of the present embodiment, when the probability of the deterioration of combustion due to the afterburning determined based on the MFB inclination a after the end crank angle θe (MFB100%) is high, the spark plug 30 degradations can be determined. Thereby, it is possible to detect deterioration of the spark plug 30 at an early stage without requiring a special configuration.

  In the above-described embodiment, when the combustion deterioration probability α is greater than 1, the deterioration of the spark plug 30 is determined. However, the threshold value used for the determination is not limited to this, and the spark plug 30 is not limited to this. It is possible to set an optimum value for determining deterioration of the image as appropriate.

  In the second embodiment described above, the ECU 40 executes the process of step 302, so that the “MFB increase rate acquisition means” in the first invention executes the process of step 304. The “determination means” in the first invention is realized.

  In the second embodiment described above, the ECU 40 executes the process of step 308, so that the “ignition timing correction means” in the third aspect of the invention executes the process of step 316. The “restricting means” in the third invention is realized.

  In the second embodiment described above, the “deterioration determination means” according to the fourth aspect of the present invention is implemented when the ECU 40 executes the process of step 318.

  In the second embodiment described above, the ECU 40 executes the process of step 312 so that the “combustion deterioration rate acquisition means” in the fifth aspect of the invention executes the processes of steps 314 and 318. Thus, the “deterioration determination means” in the fifth aspect of the present invention is realized.

Embodiment 3 FIG.
[Features of Embodiment 3]
Next, the features of the third embodiment will be described with reference to FIG. The third embodiment can be realized by executing a routine shown in FIG. 8 to be described later using the hardware configuration shown in FIG.

  In the second embodiment described above, the deterioration determination of the spark plug 30 is performed based on the probability that it is determined that the combustion deteriorates due to afterburning. However, in the second embodiment, since the combustion deterioration determination is executed based on the values obtained in a plurality of past routines, it is difficult to capture the combustion deterioration that changes over a long period of time such as aging deterioration.

Therefore, in the present third embodiment, as a method for determining the aging deterioration of the spark plug 30, the average value a _AVE and standard deviation σ of the MFB slope a after the end crank angle θe (MFB 100%) and the initial values thereof are used. The deterioration of the spark plug 30 is determined by comparison. More specifically, the average value a _AVE0 and standard deviation σ ₀ of the inclination a when the spark plug 30 is new is stored. Then, when the deviation between the average value aAVE and the average value aAVE0 or the deviation between the standard deviation σ and the standard deviation σ0 exceeds a predetermined value, the deterioration of the spark plug 30 is determined. As a result, it is possible to accurately determine aged deterioration occurring in the spark plug 30.

[Specific Processing of Embodiment 3]
Next, specific processing of the third embodiment will be described with reference to FIG. FIG. 8 is a flowchart showing a routine in which the ECU 40 performs the deterioration determination of the spark plug 30.

In the routine shown in FIG. 8, first, the average value a _AVE and standard deviation σ of the MFB gradient a after the end crank angle θe (MFB 100%) and the standard deviation σ are calculated (step 400). Here, specifically, the same processing as in step 200 is executed.

Then, the deviation between the initial value _{a AVE0} average value _{a AVE} and the average value _{a AVE} whether exceeds a predetermined threshold is determined (Step 402). As the initial value a _AVE0 , a value stored in the ECU 40 is used as an average value of the inclination a when the spark plug 30 is new. As the threshold value, a preset value is used as a threshold value for determining the aging deterioration of the spark plug 30. As a result, when it is recognized that a _AVE −a _AVE0 > threshold value is established, the _{process proceeds} to the next step, and aged deterioration of the spark plug 30 is determined (step 404).

On the other hand, if establishment of a _AVE −a _AVE0 > threshold value is not recognized, the _{process proceeds} to the next step, and the deviation between the standard deviation σ and the initial value σ ₀ of the σ exceeds the predetermined threshold value. It is determined whether or not (step 406). As the initial value σ ₀ , a value stored in the ECU 40 is used as the standard deviation of the inclination a when the spark plug 30 is new. As the threshold value, a preset value is used as a threshold value for determining the aging deterioration of the spark plug 30. As a result, when it is recognized that σ−σ ₀ > threshold value is established, the routine proceeds to step 404 where it is determined whether the spark plug 30 has deteriorated over time. On the other hand, when the establishment of σ−σ ₀ > threshold is not recognized, it is determined that the spark plug 30 has not deteriorated, and this routine is immediately terminated.

As described above, according to the system of the present embodiment, by comparing the average value a _AVE and standard deviation σ of the MFB slope a after the end crank angle θe (MFB 100%) with these initial values, ignition is performed. Aging deterioration of the plug 30 can be determined.

  In the third embodiment described above, the “deterioration determination means” in the fourth aspect of the present invention is realized by the ECU 40 executing the process of step 404 described above.

  In the third embodiment described above, the ECU 40 executes the process of step 400, so that the “average value acquisition means” in the sixth aspect of the invention executes the processes of steps 402 and 404. Thus, the “deterioration determination means” in the fifth aspect of the invention is realized.

It is a schematic block diagram for demonstrating the system configuration | structure as Embodiment 1 of this invention. It is a characteristic diagram for demonstrating the change of MFB in MBT control. It is a flowchart which shows the routine for performing MBT control. It is a figure which shows the change of MFB of each combustion state, respectively. It is a figure which shows the change of MFB of each combustion state, respectively. It is a flowchart of the routine performed in Embodiment 1 of the present invention. It is a flowchart of the routine performed in Embodiment 2 of this invention. It is a flowchart of the routine performed in Embodiment 3 of the present invention.

Explanation of symbols

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 In-cylinder pressure sensor 40 ECU (Electronic Control Unit)
42 Crank angle sensor κ Specific heat ratio

Claims (6)

From the start crank angle to the predetermined crank angle with respect to the total mass of fuel burned in the period from the start crank angle before normal combustion starts in the combustion chamber of the internal combustion engine to the end crank angle after the combustion ends. MFB acquisition means for acquiring a ratio (hereinafter referred to as MFB) of the total mass of fuel burned in a period;
MFB increase rate acquisition means for acquiring an increase rate of the MFB in a period in which the predetermined crank angle is after the end crank angle;
Determination means for determining deterioration of combustion in the combustion chamber when the increase rate is greater than a predetermined rate;
A control device for an internal combustion engine, comprising:   2. The control apparatus for an internal combustion engine according to claim 1, wherein the MFB increase rate acquisition means acquires the increase rate of the MFB in a period from the end crank angle to a crank angle immediately before the exhaust valve opens. . The internal combustion engine is a spark ignition type internal combustion engine provided with a spark plug,
Ignition timing correction means for correcting the ignition timing based on the MFB at the specific crank angle;
Limiting means for limiting, when the determination means determines combustion deterioration in the combustion chamber, MFB at the time of the combustion deterioration is reflected in the ignition timing correction;
The control apparatus for an internal combustion engine according to claim 1 or 2, characterized by comprising: The internal combustion engine is a spark ignition type internal combustion engine provided with a spark plug,
The internal combustion engine control device according to any one of claims 1 to 3, further comprising a deterioration determination unit that determines whether or not the spark plug has deteriorated based on the rate of increase.   The deterioration determination means includes combustion deterioration rate acquisition means for acquiring a rate at which combustion deterioration in the combustion chamber is determined when the determination means is executed a plurality of times, and when the combustion deterioration rate is greater than a predetermined rate, 5. The control device for an internal combustion engine according to claim 4, wherein it is determined that the spark plug has deteriorated.   The deterioration determination means includes average value acquisition means for acquiring an average value of the increase ratio when the MFB increase ratio acquisition means is executed a plurality of times, and when the average value is greater than a predetermined value, the spark plug is 5. The control apparatus for an internal combustion engine according to claim 4, wherein it is determined that the engine has deteriorated.

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