JP2007032407A - Combustion diagnostic method and apparatus for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately detect the occurrence of pre-ignition from in-cylinder pressure detection signals, to avoid misdiagnosis due to pre-ignition causes in sensor abnormality determination, and to detect in-cylinder pressure accompanying such misdiagnosis. Provided are an internal combustion engine combustion diagnostic method and a combustion diagnostic apparatus capable of preventing the occurrence of an error in a combustion diagnostic result based on a value.
A combustion diagnostic method for an internal combustion engine (engine) for diagnosing a combustion state in a cylinder based on a cylinder pressure detection value detected by a cylinder pressure detector, and determining whether or not pre-ignition has occurred. Next, an abnormality determination of the in-cylinder pressure detector is performed, and pre-ignition occurs when the in-cylinder pressure detection value exceeds a threshold value of the in-cylinder pressure set based on the corrected moving average value of the in-cylinder pressure change. And the progress of the abnormality determination logic of the in-cylinder pressure detector is stopped. When the in-cylinder pressure detection value is less than or equal to the threshold value of the in-cylinder pressure, it is determined that pre-ignition does not occur and the cylinder The abnormality determination logic of the internal pressure detector is advanced.
[Selection] Figure 1

Description

  The present invention relates to a combustion diagnostic method and combustion diagnostic apparatus for an internal combustion engine including a gas engine and a diesel engine, and more particularly to a combustion diagnostic method and combustion diagnostic apparatus for an internal combustion engine that can detect the occurrence of premature ignition in a cylinder. .

  In an internal combustion engine, particularly a gas engine whose main fuel is clean gas such as city gas, it is essential to detect and diagnose the combustion state in the combustion chamber, and to control the fuel ignition timing and the fuel injection amount suitable for the combustion diagnosis result. At the same time, it reliably detects malfunction phenomena related to combustion such as occurrence of knocking due to misfire or extinguishing in the combustion chamber and non-uniformity of the air-fuel mixture concentration and premature ignition due to residual unburned fuel in the cylinder. It is required to take corrective action.

As a combustion diagnostic apparatus for detecting and diagnosing the combustion state in the combustion chamber of the engine, techniques such as Patent Document 1 (Japanese Patent Laid-Open No. 2000-110652) and Patent Document 2 (Japanese Patent Laid-Open No. 9-42040) are provided. .
In the technique of Patent Document 1 (Japanese Patent Laid-Open No. 2000-110652), the extraction frequency band in the in-cylinder pressure detection signal from the in-cylinder pressure detector is set according to the current value of the operating parameter of the internal combustion engine, and the cylinder The signal component in the extraction frequency band set from the internal pressure detection signal is extracted by the filter means, and the occurrence of knocking is determined when the extracted component is equal to or greater than the threshold value.
In the technique of Patent Document 2 (Japanese Patent Laid-Open No. 9-42040), three high-pass filters having different cut-off frequencies are used to perform accurate feedback control of the air-fuel ratio or EGR amount even during non-steady operation. It is possible.

Japanese Unexamined Patent Publication No. 2000-110652 Japanese Patent Laid-Open No. 9-42040

  In such a combustion diagnostic apparatus for an internal combustion engine, in-cylinder pressure detectors for detecting the in-cylinder pressure of the engine (internal combustion engine) are judged to be able to cope with sudden changes in the load and the rotational speed in order to cope with sudden changes in the load and rotation speed. When the variation in pressure (Pval) at a specific crank angle is evaluated with the standard deviation value, and the absolute pressure of the in-cylinder pressure detector varies with temperature due to temperature drift characteristics, instead of absolute pressure (Pval) Means for using the relative pressure ΔPval from the bottom dead center Pbd is proposed by the present inventors.

However, if an unburned ignition source such as high-temperature soot remains in the cylinder, it will be ignited earlier than the original combustion in the next cycle, that is, pre-ignition. There are things to do.
When such pre-ignition occurs, as shown in FIG. 6, the pressure variation is high and large such as A1, B1, C1, and D1 with respect to normal in-cylinder pressure changes indicated by A, B, C, and D. The in-cylinder pressure changes, and the value of the pressure (Pval) at the specific crank angle before the ignition point F used for the sensor abnormality determination increases rapidly. For this reason, the variation of the standard deviation value at the time of sensor abnormality determination becomes large, and as a result, it is often misdiagnosed as “sensor abnormality”, which causes an error in the combustion diagnosis result based on the in-cylinder pressure detection value. It becomes.
However, no means for solving such a problem has been proposed in the technique of Patent Document 1 (Japanese Patent Laid-Open No. 2000-110652) or Patent Document 2 (Japanese Patent Laid-Open No. 9-42040).

  Therefore, in view of the problems of the prior art, the present invention makes it possible to accurately detect the occurrence of pre-ignition from the in-cylinder pressure detection signal, avoids misdiagnosis due to pre-ignition cause mixing at the time of sensor abnormality determination, and An object of the present invention is to provide a combustion diagnostic method and a combustion diagnostic device for an internal combustion engine that can prevent the occurrence of an error in the combustion diagnostic result based on the in-cylinder pressure detection value that accompanies a misdiagnosis.

  The present invention achieves such an object, and is a combustion diagnosis method for an internal combustion engine (engine) for diagnosing a combustion state in a cylinder based on a detected value of a cylinder pressure detected by a cylinder pressure detector. In-cylinder pressure threshold value is set based on the corrected moving average value of the in-cylinder pressure change after the sensor abnormality determination of the in-cylinder pressure detector is performed following the determination of the occurrence of pre-ignition. When pre-ignition occurs, the pre-ignition occurrence is determined and the progress of the sensor abnormality determination logic of the in-cylinder pressure detector is stopped. When the in-cylinder pressure detection value is less than the in-cylinder pressure threshold, pre-ignition It is determined that there is no occurrence, and a sensor abnormality determination logic of the in-cylinder pressure detector is advanced.

In this invention, specifically, the following configuration is preferable.
(1) A corrected moving average value (Pavg) of in-cylinder pressure change is calculated from the in-cylinder pressure detection value, and a corrected moving average in which the current value (Pval) of the in-cylinder pressure detection value corresponds to the current value (Pval) When the sum of the value (Pavg) and the pre-ignition threshold value (δ1) set in advance is exceeded (Pval> Pavg + δ1), the pre-ignition occurrence is judged and the sensor abnormality judgment logic of the in-cylinder pressure detector proceeds. And the current value (Pval) of the in-cylinder pressure detection value is equal to or less than the sum of the corrected moving average value (Pavg) and the pre-ignition threshold value (δ1) (Pval ≦ Pavg + δ1). And the abnormality determination logic of the in-cylinder pressure detector is advanced.

  (2) The pre-ignition corrected moving average value (Pmem) at the time of determination of the occurrence of pre-ignition of the corrected moving average value (Pavg) is stored, and the current value of the in-cylinder pressure detection value for each subsequent cycle ( Pval) and the difference (Pval−Pavg) between the corrected moving average value (Pavg) corresponding to the current value (Pval) becomes smaller than a preset noise level threshold (δ2) (| Pval −Pavg | <δ2), the corrected moving average value (Pavg) is updated using the stored value of the pre-ignition corrected moving average value (Pmem) (Pavg → Pmem), and the determination of the occurrence of pre-ignition is ( Pval> Pmem + δ1).

The invention of a combustion diagnostic apparatus for carrying out the combustion diagnostic method for an internal combustion engine includes:
In a combustion diagnostic apparatus for an internal combustion engine (engine) configured to diagnose a combustion state in a cylinder based on a cylinder pressure detection value detected by a cylinder pressure detector, a cylinder from the cylinder pressure detector is used. Pre-ignition determination means for determining whether or not pre-ignition has occurred based on the detected internal pressure value and in-cylinder pressure sensor abnormality determination means for determining whether or not the in-cylinder pressure detector is abnormal. The pre-ignition determination means includes means for calculating a corrected moving average value (Pavg) of the in-cylinder pressure change based on the in-cylinder pressure detection value, and the current value (Pval) of the in-cylinder pressure detection value is the current value (Pval ) Exceeds the sum of the corrected moving average value (Pavg) corresponding to the pre-ignition threshold value (δ1) (Pval> Pavg + δ1) and the in-cylinder pressure sensor determines whether pre-ignition has occurred. The progress of the abnormality determination logic of the abnormality determination means is stopped, and the current value (Pval) of the in-cylinder pressure detection value is equal to or less than the sum of the corrected moving average value (Pavg) and the pre-ignition threshold value (δ1). (Pval.ltoreq.Pavg + .delta.1) characterized in that it is configured to determine whether or not premature ignition has occurred and to advance the abnormality determination logic of the cylinder pressure sensor abnormality determination unit.

  In addition to the invention of the combustion diagnostic device, the pre-ignition determination means stores means for the pre-ignition corrected moving average value (Pmem) at the time of determination of the pre-ignition occurrence of the corrected moving average value (Pavg). And a difference (Pval-Pavg) between the current value (Pval) of the in-cylinder pressure detection value for each cycle after the storage and the corrected moving average value (Pavg) corresponding to the current value (Pval) is preset. When the noise level is smaller than the threshold value (δ2) (| Pval−Pavg | <δ2), the stored value of the pre-ignition corrected moving average value (Pmem) is used as the corrected moving average value (Pavg). And updating means (Pavg → Pmem) and adding means for determining the occurrence of premature ignition.

According to the present invention, determination of the presence or absence of premature ignition occurrence and abnormality determination of the in-cylinder pressure detector based on the result,
(1) A corrected moving average value (Pavg) of in-cylinder pressure change is calculated from the in-cylinder pressure detection value, and a corrected moving average value corresponding to the current value (Pval) of the in-cylinder pressure detection value is calculated. When the sum of (Pavg) and a preset pre-ignition threshold value (δ1) is exceeded (Pval> Pavg + δ1), the pre-ignition occurrence is determined and the progress of the abnormality determination logic of the in-cylinder pressure detector is stopped. To do.
(2) When the current value (Pval) of the in-cylinder pressure detection value is less than or equal to the sum of the corrected moving average value (Pavg) and the pre-ignition threshold value (δ1) (Pval ≦ Pavg + δ1) It is determined that there is no occurrence and the abnormality determination logic of the in-cylinder pressure detector is advanced.
By performing this procedure, it is possible to accurately detect premature ignition, and avoid erroneously determining premature ignition as a sensor abnormality when determining sensor abnormality of the in-cylinder pressure detector of the engine. .
As a result, it is possible to appropriately take measures such as dealing with abnormal combustion in the cylinder, that is, emergency stop of the engine, avoidance of melting damage of the combustion chamber components due to stop of fuel supply only to the pre-ignited cylinder. it can.

In addition, prior to determining the sensor abnormality of the in-cylinder pressure detector, priority is given to determining whether pre-ignition has occurred or not. Such a malfunction of diagnosis can be avoided by determining whether or not premature ignition is performed in a continuous cycle by redundant determination.
Further, according to the present invention, there is no possibility that it is determined that pre-ignition is caused by noise superimposed on the in-cylinder pressure detector, and the occurrence of such a misjudgment can be avoided, and the in-cylinder pressure accompanying the misdiagnosis can be avoided. Generation of an error in the combustion diagnosis result based on the detected value can be prevented.
Further, according to the present invention, pre-ignition is a state in which a specific cylinder is temporarily overheated and is not an abnormality in the mechanism of the engine. Thus, by stopping the main fuel for a certain period, the occurrence of flue explosion in the exhaust system can be avoided.

  Hereinafter, the present invention will be described in detail with reference to the embodiments shown in the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the component parts described in this example are not intended to limit the scope of the present invention only to specific examples unless otherwise specified. Only.

FIG. 3 is an overall configuration diagram showing the overall configuration of the combustion diagnosis and combustion control device of the gas engine according to the embodiment of the present invention.
In FIG. 3, 20 is an engine body of a gas engine, 45 is a piston, 46 is a crankshaft, 44 is a combustion chamber, 41 is an intake valve, 42 is an exhaust valve, and 43 is an exhaust pipe. Reference numeral 9 denotes an intake pipe that communicates with the intake valve 41, and a gas injection device 10 that injects fuel gas into the air (intake air) flowing through the intake pipe 9 is provided in the middle of the pipe of the intake pipe 9. ing. Reference numeral 8 denotes a gas supply pipe that connects a fuel gas tank (not shown) that stores fuel gas and the gas injection device 10.

Reference numeral 7 denotes a gas supply electromagnetic valve provided at the inlet of the gas injection device 10 of the gas supply pipe 8. The gas supply electromagnetic valve 7 is controlled to open and close by a control signal from a fuel control device 200 to be described later. The area is adjusted.
Reference numeral 11 denotes an ignition device for accelerating combustion of a lean mixed gas on the main combustion chamber side by injecting pilot fuel from a pilot fuel injection valve into a sub chamber (not shown) and starting torch ignition when the gas engine is started. .

  When the gas engine having such a configuration is operated, the ignition device 11 performs torch ignition, and when a gas valve (not shown) is opened, the fuel gas in the fuel gas tank (not shown) is changed to a gas pressure adjusting device (not shown). ), The pressure is adjusted and supplied to the gas injection device 10, and the gas supply electromagnetic valve 7 is opened to be injected into the air in the intake pipe 9 and mixed with the air. Then, the air-fuel mixture from the gas injection device 10 is introduced into the combustion chamber 44 that is pre-combusted by the jet flame from the ignition device 11 together with the opening of the intake valve 41 and burns, and a predetermined combustion cycle is achieved. Made.

Reference numeral 1 denotes an in-cylinder pressure detector that detects a gas pressure in the combustion chamber 44 of the gas engine, that is, an in-cylinder pressure. Reference numeral 2 denotes a crank angle detector that detects a crank angle of the crankshaft 46.
Reference numeral 100 denotes a combustion diagnostic apparatus, which includes pre-ignition determination means 3, in-cylinder pressure sensor abnormality determination means 4, and a combustion diagnosis unit 5, which will be described in detail later.
The combustion diagnosing unit 5 determines the presence or absence of abnormality of the in-cylinder pressure detector 1 by the pre-ignition determination unit 3 and the subsequent in-cylinder pressure sensor abnormality determination unit 4, thereby detecting the in-cylinder pressure detection value. Based on the above, the crank angle detection signal from the crank angle detector 2 is supplementarily used to diagnose the combustion state in the combustion chamber 44.

  Reference numeral 200 denotes a combustion control device, which receives a diagnosis result signal from the combustion diagnosis unit 5 and controls the operation of the ignition device 11 while shutting off or opening the gas supply electromagnetic valve 7 based on the diagnosis result signal. Is. Reference numeral 6 denotes a display device for displaying a diagnosis result in the combustion diagnosis unit 5. Note that an alarm device that transmits an alarm based on the result of combustion diagnosis may be connected to the combustion diagnosis device 100.

Next, the pre-ignition determination operation by the pre-ignition determination means 3 will be described with reference to FIGS.
1 is a control flowchart of pre-ignition determination means in the gas engine combustion diagnostic apparatus 100, FIG. 2 is a control flowchart of initialization of the pre-ignition determination means, and FIG. 4 is a diagram for explaining the pre-ignition occurrence state. FIG. 5 is a control flowchart when the pre-ignition determination is combined with another combustion diagnosis.

A control flow of the pre-ignition determination means 3 will be described with reference to FIG.
Step (1): From the in-cylinder pressure detection value detected by the in-cylinder pressure detector 1, from the bottom dead center
In-cylinder pressure at a specific crank angle up to the ignition point F (see FIG. 6)
The current value Pval is measured (detected).
Step (2): Corrected moving average value Pavg of in-cylinder pressure change based on the current value Pval
Is calculated.
Step (3): Was the previous cycle in an appropriate combustion state (the number of pre-ignitions was 0 (zero)
))) Or not.
YES: The last time, it is determined that there is no premature ignition, and the process proceeds to step (4).
N O: Pre-ignition occurred last time, and it is determined that there is a possibility of continuous pre-ignition.
Go to (11).
Step (4): Whether the in-cylinder pressure detection value Pval is prematurely ignited or not is determined.
al, the corrected moving average value Pavg, and the pre-ignition threshold set in advance
Judgment is made by comparing with the sum of the value δ1.
That is, it is determined whether or not Pval> Pavg + δ1 is satisfied.
YES: First premature ignition, go to step (5).
N O: This time is also in an appropriate state, so go to step (6).
Step (5): It is determined that pre-ignition is performed, and the process proceeds to Step (7).
Step (7): Set 1 to the number of pre-ignitions and go to RETURN.
Step (6): It is determined that the combustion state is appropriate, and the process proceeds to Step (8).
Step (8): Pre-ignition number of times 1 is cleared and pre-ignition number of times = 0 is set to step (9)
What.
Step (9): The difference between the current value Pval of the in-cylinder pressure and the corrected moving average value Pavg is completely eliminated.
The counter value is within a preset noise level threshold δ2, that is, allowable.
Determine whether it is within range.
That is, it is determined whether or not | Pval−Pavg | <δ2.
YES: It is determined that the value is within the allowable range (within the threshold value δ2), and the process proceeds to step (10).
N O: It is judged that it is out of the permissible range (exceeds the threshold value δ2), and RETURN is entered.
Step (10): This corrected moving average value Pavg is used as a corrected moving average for the next time (next cycle).
The set value Pmem of the average value Pavg (Pavg → Pmem), RE
Go to TURN.
Step (11): Whether pre-ignition has been completed (that is, Pval <Pmem + δ2)
).
YES: It is determined that premature ignition has ended and the state has returned to the appropriate state, and step (13
)What.
NO: It is determined that pre-ignition is occurring again this time, and the process proceeds to step (12).
Step (12): It is determined that the combustion state is premature ignition, and the process proceeds to Step (14).
Step (14): Add 1 to the number of pre-ignitions and return to RETURN.
Step (13): It is determined that the combustion state is appropriate without premature ignition, and the process proceeds to Step (15).
Step (15): The number of pre-ignitions is cleared to 0 and the process proceeds to Step (16).
Step (16): The difference between the current value Pval of the in-cylinder pressure and the corrected moving average value Pavg
The absolute value is within a preset noise level threshold δ2, that is,
It is determined whether it is within the allowable range.
That is, it is determined whether or not | Pval−Pavg | <δ2.
.
YES: It is determined that the value is within the allowable range (within the threshold value δ2), and the process proceeds to step (17).
N O: It is judged that it is out of the permissible range (exceeds the threshold value δ2), and RETURN is entered.
Step (17): This corrected moving average value Pavg is used as a corrected moving average for the next time (next cycle).
The set value Pmem of the average value Pavg (Pavg → Pmem), RE
Go to TURN.

In the control flow described above, the relationship between the threshold value δ1 for the pre-ignition start and the threshold value δ2 for the pre-ignition end is set to δ1 ≧ δ2> 0, so that hysteresis is provided. The ignition judgment is stabilized.
In steps (4) to (7), the combustion state is determined to be either proper combustion or pre-ignition, and if pre-ignition, the number of pre-ignitions is added, and if pre-ignition is present, pre-ignition is performed. Clear the count.
In steps (9) to (10), when the corrected moving average value Pavg approaches within the set δ2, it is updated to the set value Pmem of the next (next cycle) corrected moving average value Pavg.

Next, an initialization control flow that is a base of the control flow will be described with reference to FIG.
Step (1): From the in-cylinder pressure detection value detected by the in-cylinder pressure detector 1, from the bottom dead center
The current value Pval of the in-cylinder pressure up to the ignition point F (see FIG. 6)
measure.
Step (2): The present value Pval of the in-cylinder pressure is changed to an initial set value Pme of the corrected moving average value.
m.
Step (3): Set the number of pre-ignition times to zero.
Step (4): Pre-ignition judgment threshold values δ1, δ2 are set, and the flow returns to RETURN.

Next, based on FIG. 5, a combination flow from the pre-ignition determination to the in-cylinder pressure sensor abnormality determination of the in-cylinder pressure detector 1 and other combustion diagnosis will be described.
Step (1): Pre-ignition determination is performed according to the flow of FIG.
Step (2): It is determined whether or not the pre-ignition determination is completed.
YES: It is determined that pre-ignition has ended, and the process proceeds to step (5).
N O: It is determined that pre-ignition has not ended, and the standard deviation follows the pre-ignition determination.
In-cylinder pressure sensor abnormality determination is performed according to step (3).
Step (3): Following the pre-ignition judgment, the cylinder pressure sensor abnormality judgment based on the standard deviation is made.
Go to step (4).
Step (4): Determination result of presence or absence of abnormality in the in-cylinder pressure sensor
YES: Return to RETURN due to in-cylinder pressure sensor abnormality.
NO: Go to step (5) without in-cylinder pressure sensor abnormality.
Step (5): Shift to other combustion diagnosis determination.

According to the above control flow, the current value Pval in-cylinder pressure, modified movement when the average value the threshold value [delta] ₁ or even greater than Pavg is determined to sensor abnormality determining that pre-ignition occurs The logic is not allowed to pass (the progress of the abnormality determination logic is stopped), and the corrected moving average value Pavg at this time is stored and used as the pre-ignition corrected moving average value Pmem.
Thereafter, when the difference between the current value Pval of the in-cylinder pressure measured for each cycle and the corrected moving average value Pavg becomes equal to or less than the noise level threshold δ ₂ , the pre-ignition corrected moving average value Pmem By updating the stored value to the corrected moving average value Pavg, it is possible to perform appropriate evaluation based on the value Pmem immediately before pre-ignition.
Here, δ1 is a threshold value that can detect pre-ignition without causing a sensor abnormality of the in-cylinder pressure detector 1, and δ2 is a threshold value for an allowable variation in the unburned region during normal combustion. There is a relationship of δ1 ≧ δ2> 0 as described above.

FIG. 4 shows the result of simulation calculation according to the control flowchart of FIG.
In FIG. 4, when the current value Pval of the in-cylinder pressure indicated by A exceeds Pmem + δ1 indicated by D (one-dot chain line), pre-ignition is determined, and the corrected moving average value B enters the region of Pmem + δ2 indicated by E (dashed line). And determined to be in an appropriate combustion state. In FIG. 4, C represents the set value of Pmem, and F represents the value of Pmem−δ2.

Further, since the pre-ignition determination in this embodiment has priority over the sensor abnormality determination of the in-cylinder pressure detector 1, the in-cylinder pressure detector in the case where sudden noise is superimposed on the in-cylinder pressure detector 1 or the like. Although there is a possibility that premature ignition is erroneously determined when 1 is abnormal, the control flow in FIG. 1 is a determination result for one cycle, and when multiple premature ignitions occur multiple times. Since redundancy is provided so that an avoidance operation corresponding to premature ignition is performed for the first time, an erroneous determination due to noise in one cycle does not affect the determination result.

  According to the present invention, it is possible to accurately detect the occurrence of premature ignition from the in-cylinder pressure detection signal, and it is possible to avoid a misdiagnosis due to premature ignition cause mixing at the time of sensor abnormality determination, and a cylinder associated with such a misdiagnosis. It is possible to provide a combustion diagnostic method and a combustion diagnostic device for an internal combustion engine that can prevent the occurrence of an error in the combustion diagnostic result based on the detected internal pressure value.

It is a control flowchart of the pre-ignition determination means in the combustion diagnosis apparatus of the gas engine which concerns on the Example of this invention. It is a control flowchart of initialization of the pre-ignition determination means in the embodiment. 1 is an overall configuration diagram illustrating an overall configuration of a combustion diagnosis and combustion control device for a gas engine according to an embodiment of the present invention. It is a diagram for explanation of the pre-ignition occurrence state in the embodiment. It is a control flowchart at the time of combining the pre-ignition determination and other combustion diagnosis in the said Example. It is a diagram for explanation of premature ignition occurrence of a gas engine.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 In-cylinder pressure detector 2 Crank angle detector 3 Premature ignition determination means 4 In-cylinder pressure sensor abnormality determination means 5 Combustion diagnosis part 6 Display apparatus 20 Engine 44 Combustion chamber 100 Combustion diagnosis apparatus 200 Combustion control apparatus

Claims (5)

  A combustion diagnosis method for an internal combustion engine (engine) for diagnosing a combustion state in a cylinder based on a detected value of a cylinder pressure detected by a cylinder pressure detector, wherein the cylinder is subsequent to determination of the occurrence of pre-ignition. An internal pressure detector sensor abnormality determination is performed, and when the in-cylinder pressure detection value exceeds a threshold value of the in-cylinder pressure set based on the corrected moving average value of the in-cylinder pressure change, it is determined whether pre-ignition has occurred. At the same time, the progress of the sensor abnormality determination logic of the in-cylinder pressure detector is stopped, and when the in-cylinder pressure detection value is less than or equal to the threshold value of the in-cylinder pressure, it is determined that pre-ignition does not occur and the in-cylinder pressure A combustion diagnostic method for an internal combustion engine, comprising advancing sensor abnormality determination logic of a detector.   The corrected moving average value (Pavg) of the in-cylinder pressure change is calculated from the in-cylinder pressure detection value, and the corrected moving average value (Pavg) corresponding to the current value (Pval) of the current value (Pval) of the in-cylinder pressure detection value is calculated. ) And a pre-ignition threshold value (δ1) set in advance (Pval> Pavg + δ1), the pre-ignition occurrence is determined and the progress of the sensor abnormality determination logic of the in-cylinder pressure detector is stopped. When the current value (Pval) of the in-cylinder pressure detection value is equal to or less than the sum of the corrected moving average value (Pavg) and the pre-ignition threshold value (δ1) (Pval ≦ Pavg + δ1), no pre-ignition occurs 2. The combustion diagnosis method for an internal combustion engine according to claim 1, wherein a determination of whether the in-cylinder pressure is detected or not is advanced.   The pre-ignition corrected moving average value (Pmem) at the time of determination of the pre-ignition occurrence of the corrected moving average value (Pavg) is stored, and the current value (Pval) of the in-cylinder pressure detection value for each subsequent cycle is stored. When the difference (Pval-Pavg) from the corrected moving average value (Pavg) corresponding to the current value (Pval) becomes smaller than a preset noise level threshold value (δ2) (| Pval-Pavg | <Δ2), the corrected moving average value (Pavg) is updated using the stored value of the pre-ignition corrected moving average value (Pmem) (Pavg → Pmem), and the determination of the pre-ignition occurrence is (Pval> Pmem + δ1). 3. A combustion diagnosis method for an internal combustion engine according to claim 2, wherein   In a combustion diagnostic apparatus for an internal combustion engine (engine) configured to diagnose a combustion state in a cylinder based on a cylinder pressure detection value detected by a cylinder pressure detector, a cylinder from the cylinder pressure detector is used. Pre-ignition determination means for determining the presence or absence of pre-ignition based on the detected internal pressure value, and in-cylinder pressure sensor abnormality determination means for determining the presence or absence of sensor abnormality of the in-cylinder pressure detector, The pre-ignition determination means includes a means for calculating a corrected moving average value (Pavg) of the in-cylinder pressure change based on the in-cylinder pressure detection value, and a current value (Pval) of the in-cylinder pressure detection value is the current value ( When the sum of the corrected moving average value (Pavg) corresponding to Pval) and a pre-ignition threshold value (δ1) set in advance is exceeded (Pval> Pavg + δ1), the occurrence of pre-ignition is determined and the in-cylinder pressure is determined. The progress of the abnormality determination logic of the sensor abnormality determination means is stopped, and the current value (Pval) of the in-cylinder pressure detection value is less than the sum of the corrected moving average value (Pavg) and the pre-ignition threshold value (δ1). (Pval.ltoreq.Pavg + .delta.1) Combustion diagnostic apparatus for an internal combustion engine, comprising: means for determining whether pre-ignition has occurred, and for advancing an abnormality determination logic of the in-cylinder pressure sensor abnormality determining means. . The pre-ignition determination means stores means for pre-ignition correction moving average value (Pmem) at the time of determination of the pre-ignition occurrence of the corrected moving average value (Pavg), and a cylinder for each cycle after the storage The difference (Pval-Pavg) between the current value (Pval) of the internal pressure detection value and the corrected moving average value (Pavg) corresponding to the current value (Pval) is determined from a preset threshold (δ2) of the noise level. Is also reduced (| Pval−Pavg | <δ2), the modified moving average value (Pavg) is updated using the stored value of the pre-ignition corrected moving average value (Pmem) (Pavg → Pmem), 5. A combustion diagnostic apparatus for an internal combustion engine according to claim 4, further comprising means for determining whether or not premature ignition has occurred.

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