JP3231947B2 - Method for detecting abnormal combustion in internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combustion abnormality detecting method used for lean burn control of an internal combustion engine.

[0002]

2. Description of the Related Art In recent years, in gasoline engines for automobiles, the air-fuel ratio of an air-fuel mixture is set to a stoichiometric air-fuel ratio (14.7) in order to reduce harmful exhaust gas components such as HC and CO and improve fuel efficiency.
A much thinner lean burn engine has been proposed. In the lean burn engine, the ignition / combustion performance is improved by layered air supply that enriches the air-fuel mixture flowing near the ignition plug, swirl or tumble that enhances the turbulence of the air-fuel mixture in the combustion chamber. Further, in the lean region, nitrogen oxides (NO _x ) cannot be reduced by the three-way catalyst, and the amount of emission becomes maximum near the air-fuel ratio of 16 and decreases on the lean side, and the stable combustion limit (air-fuel ratio) Since the torque fluctuation exceeds the allowable limit on the lean side (about 22 to 23), it is necessary to control the air-fuel ratio to a narrow range near the stable combustion limit.

Therefore, a lean burn engine uses an air-fuel ratio sensor (LAFS: linear A / F sensor) capable of continuously detecting the air-fuel ratio so that the target air-fuel ratio is determined by the engine speed and volumetric efficiency. What controls the fuel injection amount by feedback is mainly used. However, since the air-fuel ratio feedback control controls the equivalent ratio between the fuel injection amount and the intake air amount, when the target air-fuel ratio is set near the stable combustion limit, the air-fuel Abnormality may occur in the combustion of the oil, leading to intermittent misfires. Therefore, the target air-fuel ratio must be set to a richer side than the combustion stability limit in order to provide a margin for combustion abnormalities and misfires, and it has not been possible to pursue the reduction of NO _X emissions and the improvement of fuel efficiency to the limit. . Therefore, in recent years, lean burn near the stable combustion limit has been further improved by detecting combustion abnormalities such as misfires based on engine rotation fluctuations and controlling the target air-fuel ratio so that abnormal combustion occurs at a very low frequency. Technologies to be realized have also been proposed.

[0004]

As a device for detecting abnormal combustion, Japanese Unexamined Patent Publication (Kokai) No. 4-109062 discloses an apparatus for detecting an angular acceleration of a crankshaft and detecting that the angular acceleration exceeds a predetermined threshold value. Which makes the determination of. In this type of device, a crank angle sensor that outputs a pulse at a predetermined angle is attached to an engine, and an angular acceleration is continuously calculated based on a time interval of the pulse output.
As the crank angle sensor, for example, a plurality of fan-shaped vanes corresponding to the combustion stroke of each cylinder are formed on a detection rotor fixed to a crankshaft or the like, and an end of each vane is an optical sensor or a magnetic sensor. The output signal is switched at the moment when the signal crosses the line.

In the above-described crank angle sensor, when there is a manufacturing error in the angular width of each vane, or when there is a backlash in a mounting portion between the rotor and the crankshaft or the like,
The signal output angle varies among the cylinders. As a result, there is a problem that the evaluation function of the rotation fluctuation becomes unstable, and the abnormal combustion cannot be detected accurately. Therefore, conventionally, it has been necessary to perform so-called segment correction for correcting variations in the detection angle width of the adjacent vanes, and to remove the variations. However, segment correction is
Since the calculation procedure is very complicated, the control program is inevitably complicated, and there is also a problem that a large capacity ROM or the like is required.

[0006] The present invention has been made in view of the above situation,
It is an object of the present invention to provide a combustion abnormality detection method for accurately detecting a combustion abnormality of an internal combustion engine by a relatively simple calculation procedure, thereby enabling the operation of the engine at a stable combustion limit or the like.

[0007]

Accordingly, a first aspect of the present invention provides a method for detecting abnormal combustion in a multi-cylinder internal combustion engine based on crank rotation information of the internal combustion engine. Detecting a crank angle signal output at a crank position; and detecting a crank angle of each cylinder of the internal combustion engine based on the detected crank angle signal.
As well as identifying whether a cylinder, calculating the angular acceleration instantaneous value in the combustion stroke of a predetermined cylinder is the specific, and the current value of the angular acceleration instantaneous value of said predetermined cylinders, each
Of the average angular acceleration calculated and stored independently for each cylinder
Based on the previous value of the angular acceleration average value of the predetermined cylinder of out, calculating a current value of the angular acceleration average value of the cylinder, and the current value of the angular acceleration instantaneous value of the predetermined cylinder, before
With the deviation between the present value of the angular acceleration average value of the serial predetermined cylinder exceeds a predetermined threshold value, the look-containing and determining that there is abnormal combustion in the predetermined cylinder, Germany for each of the respective cylinders
A combustion abnormality detection method for an internal combustion engine that stands and determines a combustion abnormality is proposed.

According to a second aspect of the present invention, in the combustion abnormality detecting method according to the first aspect, a current value of an instantaneous angular acceleration value of the predetermined cylinder, which is multiplied by a weighting constant, and the predetermined value.
A combustion abnormality detection method for an internal combustion engine in which the present value of the average angular acceleration value of the predetermined cylinder is calculated by adding the previous value of the average value of angular acceleration of the cylinder to the previous value is proposed. According to a third aspect, in the method for detecting a combustion abnormality according to the second aspect, the location
A combustion abnormality detection method for an internal combustion engine is proposed in which a value of a weighting constant for multiplying a current value of an instantaneous angular acceleration value of a constant cylinder is larger than a value of a weighting constant for multiplying a previous value of an average value of angular acceleration of the predetermined cylinder .

[0009]

According to the combustion abnormality detecting method of the present invention, when a combustion abnormality such as misfire occurs in a certain cylinder, the instantaneous value of the angular acceleration in the combustion stroke of the cylinder decreases. As a result, its
Cylinders, i.e. the deviation between the angular acceleration instantaneous value and the angular acceleration average value in a predetermined cylinder becomes Rukoto exceeds a predetermined threshold value, its
Combustion abnormality of the cylinder is determined. At this time, the average angular acceleration value is independently calculated and stored for each cylinder , and the deviation is
Calculated based on the average value of angular acceleration for each cylinder
Because it is, even if there is variation among the cylinders in a crank angle sensor, the determination of the abnormal combustion is not affected to it.

Further, in the combustion abnormality detecting method according to the second aspect,
The present value and the each cylinder Ri by that Wasl is multiplied by the respective weighting constant to the previous value of the angular acceleration average value of the angular acceleration instantaneous value
Since the present value of the average value of the angular acceleration for each time is calculated, the average value of the angular acceleration is filtered even if an instantaneous value of the angular acceleration protruding in both the positive and negative directions due to running on a rough road, noise, or the like is detected.

Further, according to the combustion abnormality detecting method of the third aspect,
Since the value of the weighting constant by which the present value of the angular acceleration is multiplied by the present value is made larger than the value of the weighting constant by which the previous value of the average of the angular acceleration is multiplied, the followability of the average value of the angular acceleration with respect to the fluctuation of the angular acceleration becomes better, and Responsiveness is improved.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a schematic configuration diagram of an engine control system to which a combustion abnormality detection method according to the present invention is applied. FIG.
In the drawings, reference numeral 1 denotes a V-type 6-cylinder gasoline engine (hereinafter simply referred to as an engine) for an automobile, and a combustion chamber, an intake system, an ignition system, and the like are designed for lean burn.
In FIG. 1, only one bank of the engine 1 is shown to avoid complicating the drawing. An intake port 2 of the engine 1 is provided with an air cleaner 5, an air flow sensor 6, a throttle valve 7, an ISC (idle speed controller) 8, and the like via an intake manifold 4 provided with a fuel injection valve 3 for each cylinder. Tube 9 is connected. The exhaust port 10 has an exhaust manifold 1.
1, an exhaust pipe 14 including an air-fuel ratio sensor 12, a three-way catalyst 13, and a muffler (not shown) is connected. The engine 1 has a spark plug 16 disposed in a combustion chamber 15 and a crank angle sensor 18 for detecting rotation of a rotor plate 17 directly attached to a crankshaft 25.

As shown in FIG. 2, three vanes 17a, 17b and 17c having a predetermined angular width (40 ° in the present embodiment) are formed on the rotor plate 17 at intervals of 120 °. When the ends of the vanes 17a, 17b, 17c cross the crank angle sensor 18, the crank angle signal SGT is output. The crank angle signal SGT
Are output in synchronization with the stroke of each cylinder, and the output timing in the case of the present embodiment is, as shown in FIG.
5 °. Further, a cylinder discrimination sensor (not shown) that outputs a cylinder discrimination signal SGC is attached to a camshaft or the like that rotates at half the rotation speed of the crankshaft 25, and discriminates which cylinder the crank angle signal SGT belongs to. It has become so. In FIG. 1, reference numeral 19 denotes a throttle sensor for detecting an opening degree .theta.TH of the throttle valve 7, reference numeral 20 denotes a water temperature sensor for detecting a cooling water temperature TW, and reference numeral 21 denotes an atmospheric pressure Ta.
Is an atmospheric pressure sensor that detects the intake air temperature Ta, and 22 is an intake air temperature sensor that detects the intake air temperature Ta.

On the other hand, in a vehicle compartment (not shown), an input / output device and a storage device (RO) containing a large number of control programs are provided.
M, RAM, BURAM, etc.), central processing unit (CP
U), an ECU (engine control unit) 23 having a timer counter and the like is installed, and performs comprehensive control of the engine 1. On the input side of the ECU 23, detection information from the various sensors described above is input. ECU23
Calculates the optimum values such as the fuel injection amount and the ignition timing from the detected information, and drives the fuel injection valve 3, the ignition coil 24 and the like.

The control procedure in this embodiment will be described below with reference to the control flowcharts of FIGS. 4 to 7 and the maps and graphs of FIGS. 8 to 14. When the driver turns on the ignition key and engine 1 starts, EC
U23 repeatedly executes the fuel injection control subroutine shown in the flowchart of FIG.

When this subroutine starts, the ECU 2
3 is a step S1 in which the operation information from each sensor described above is read into the RAM. Next, in step S2, the ECU 23 determines whether or not to perform the feedback control based on the throttle opening θTH, its time rate of change, volumetric efficiency EV, the elapsed time after starting the engine, the cooling water temperature TW, and the like.
The volumetric efficiency EV calculates an intake air amount A / N per intake stroke from the air flow rate detected by the air flow sensor 6 and the engine speed Ne, and corrects the intake air amount A / N based on the atmospheric pressure Pa, the intake air temperature Ta, and the like. It is required by If the determination is affirmative (Yes), the ECU 23
Is the volumetric efficiency EV and the engine speed Ne in step S3.
From the above, it is determined whether or not the current operating state is in a predetermined lean burn control region. Note that the lean burn control is performed in an operation region where the required torque is small, such as during idling operation or constant speed traveling.

If the determination in step S3 is Yes, the ECU 23 determines in step S4 that the volumetric efficiency E
Based on V and the engine speed Ne, the target air-fuel ratio OAF is set based on the lean air-fuel ratio map shown in FIG. next,
In step S5, the ECU 23 controls the injection amount (valve opening time TINJ) of the fuel injector 3 by a stable combustion limit control subroutine described later.

On the other hand, if the determination in step S3 is No, the ECU 23 determines in step S6 the target air-fuel ratio OAF based on the volumetric efficiency EV and the engine speed Ne based on the stoichiometric / rich air-fuel ratio map of FIG. And set
In step S7, the valve opening time TINJ of the fuel injection valve 3 is feedback-controlled based on the output signal of the air-fuel ratio sensor 12. When the determination in step S2 is No,
In step S8, the ECU 23 sets the target air-fuel ratio OAF based on the stoichiometric / rich air-fuel ratio map. Next, the ECU 23 determines in step S9 that the target air-fuel ratio OAF
After the basic injection amount TINJB is calculated from the intake air amount A / N and the intake amount A / N, the increase in the amount of acceleration or the increase in the amount of cold is corrected, and step S10 is performed.
The open time of the fuel injection valve 3 is controlled in an open loop.

The above-described stable combustion limit control subroutine is repeatedly executed in the following procedure every time the crank angle signal SGT is input. When this subroutine is started, the ECU 23 first determines whether or not the current operating state is in a predetermined learning region in step S20 of FIG.
This determination is made based on, for example, whether or not the current operating state is in the learning region indicated by cross-hatching in the lean air-fuel ratio map in FIG. 8. If this determination is No,
Proceeding to step S36 in FIG. 6 described below, the following steps are executed to drive and control the fuel injection valve 3. In the present embodiment, the above-mentioned predetermined learning region is a range in which the volume efficiency EV is between EVA and EVB and the engine speed Ne is between NeA and NeB.

If the determination in step S20 is Yes, the ECU 23 determines in step S21 that the predetermined value TCDX
After subtracting 1 from the countdown timer TCD whose initial value is (128 in this embodiment), in step S22,
The instantaneous angular acceleration value Amn in the n-th combustion stroke of the m-th cylinder in the ignition order is calculated by the following equation. In this embodiment, TCDX (128 cycles) is set as one sampling section, but the value can be set arbitrarily. Also,
In the engine 1 of the present embodiment, the ignition order of each cylinder is 1
-2-3-4-5-6.

Amn = 1 / Tmn · (1 / Tmn−1 / Tm, n−1) where Tmn is the input of the crank angle signal in the n-th combustion stroke of the m-th cylinder and the immediately preceding crank angle. The time interval between input of the signal (ie, crankshaft 2
5 required 120 ° rotation). After completing the calculation of the instantaneous angular acceleration value Amn, the ECU 23 calculates the current cylinder-specific angular acceleration average value Amave using the following equation and the previous cylinder-specific angular acceleration average value Amavela in step S23.

Amave = KF · Amn− (1−KF) · Amavela Here, KF is a filtering constant. In the present embodiment, the weighting of the instantaneous angular acceleration value Amn of this time is determined by averaging the previous angular acceleration for each cylinder. The value Amavela is set to 0.65 so as to be larger than the weight. This allows
At the time of acceleration / deceleration, the followability of the cylinder-specific angular acceleration average value Amavela to the fluctuation of the angular acceleration instantaneous value Amn is improved.

Next, the ECU 23 determines in step S24
The deviation between the instantaneous angular acceleration value Amn and the average angular acceleration value Amave for each cylinder, that is, the angular acceleration change amount ΔAmn is calculated by the following equation. As shown in the graph of FIG. 10, the angular acceleration change amount ΔAmn when one cylinder is completely misfired (of course,
(Negative value), the absolute value increases as the volumetric efficiency EV increases. This is because it is necessary to perform compression work of another cylinder without driving force due to combustion at the time of misfire, and the angular acceleration sharply decreases in a region where the actual compression ratio is high.

ΔAmn = Amn−Amave When the variation of the angular acceleration variation ΔAmn is calculated, the ECU 2
Next, in step S25, a cylinder-by-cylinder acceleration index Imnac is calculated by the following equation using the volume efficiency correction coefficient KEV retrieved from the map of FIG. After calculating the cylinder-by-cylinder acceleration index Imnac, the ECU 23 calculates
Next, in step S26, it is determined whether or not this is below a predetermined threshold value Iacx. If this determination is No, the process proceeds to step S30 in FIG. Incidentally, the cylinder-by-cylinder acceleration index Imnac at the time of misfire is calculated as shown in the graph of FIG.
The value is constant regardless of the engine speed Ne and the volumetric efficiency EV. Therefore, the deterioration of combustion can be determined by providing a predetermined threshold value. Naturally, the threshold value Iacx is set to a sufficiently low value with respect to the angular acceleration variation accompanying normal combustion, so that the cylinder-specific acceleration index Imnac becomes lower only when combustion deterioration of a certain degree or more occurs. I have.

On the other hand, if the determination in step S26 is Yes, the number of misfire counters CMF is set to 1 in step S27.
Is added, and in step S28, the cylinder-by-cylinder variation integrated value Σ
The current cylinder-specific acceleration index Imnac is added to Im, and the process proceeds to step S30 in FIG. As shown in FIG. 13, each time the countdown timer TCD is reset to the initial value, the misfire frequency counter CMF and the cylinder-by-cylinder variation integrated value ΣIm are reset to the initial value 0.

The ECU 23 determines in step S30 in FIG.
It is determined whether or not the countdown timer TCD has become 0, that is, whether or not the operation of TCDX (128) cycles has been performed in the learning area. If the determination is No, the process proceeds to step S36 described later. In the present embodiment, even if the operating state once deviates from the learning region, the misfire counter CMF, the cylinder-by-cylinder variation integrated value ΣIm, and the countdown timer value TCD are stored in the RAM, and the operation enters the learning region again. At this time, the ECU 23 continuously performs integration and subtraction of each value.

If the operation of the TCDX cycle is performed in the learning area and the determination in step S30 is Yes, the ECU
In step S31, it is determined whether or not the value of the misfire counter CMF is 0. If the determination is Yes, the ECU 23 adds 1 to the lean counter CLM in step S32, and then determines whether the value of the lean counter CLM is 2 in step S33. If the determination is No, the process proceeds to step S39 described later to continue the operation. Note that the initial value of the lean counter CLM is 0.

If the determination in step S33 is Yes, that is, if the value of the misfire counter CMF is 0 over two sampling intervals (256 cycles), the ECU 2
No. 3 judges that the air-fuel ratio of the cylinder is still on the rich side with respect to the stable combustion limit. Then, after resetting the lean counter CLM in step S34, step S35
Is a predetermined weight correction value KD (0.2% in this embodiment).
, The cylinder-by-cylinder fuel correction coefficient KLm is corrected to the lean side by the following equation. In the case of this embodiment, the cylinder-by-cylinder fuel correction coefficient KLm takes a value in the range of -10% to 10%,
It is stored in a nonvolatile memory such as a RAM.

KLm = KLm-KD On the other hand, if the determination in step S31 is No, the ECU
In step S36, first, the lean counter CLM is reset. Thus, the above-described correction of the fuel correction coefficient KLm for each cylinder toward the lean side is performed in two sampling intervals (2
56 cycles) The value of the misfire counter CMF is 0 continuously
Is performed only in the case of, and the stability of the air-fuel ratio control is improved. When the reset of the lean counter CLM is completed, the ECU 23 next sets the value of the misfire counter CMF to the threshold CMFX (3 in this embodiment) in step S37.
Times) or not. If this determination is No, the ECU 23 determines that the air-fuel ratio of the cylinder is at the stable combustion limit, holds the cylinder-by-cylinder fuel correction coefficient KLm of the fuel injection valve 3 as it is, and proceeds to step S39. Continue operation at the stable combustion limit.

If the determination in step S37 is Yes, the ECU 23 determines that the air-fuel ratio of the cylinder has already exceeded the stable combustion limit and has entered the lean side. Then, in step S38, the cylinder-by-cylinder increase correction value Kam corresponding to the cylinder-by-cylinder variation integrated value ΣIm is set based on the map of FIG. 14, and the cylinder-by-cylinder fuel correction coefficient KLm is updated to the rich side by the following equation. That is, since the correction to the rich side is performed using the value of the misfire counter CMF in one sampling period (128 cycles), the responsiveness of the air-fuel ratio control to the abnormal combustion is improved. It should be noted that, as shown in FIG. 14, the cylinder-by-cylinder increase correction value Kam increases linearly with an increase in the cylinder-by-cylinder variation integrated value ΔIm. This allows
When a combustion abnormality occurs, the correction to the rich side is performed at once, and the operation state quickly returns to the stable combustion region.

KLm = KLm + Kam When the cylinder-specific fuel correction coefficient KLm is updated in step S35 or step S38, the ECU 23 proceeds to step S3.
9, the misfire counter CMF and the cylinder-by-cylinder variation integrated value ΣIm
And the value of the countdown timer TCD is reset.
When the reset of the counter, the timer, and the like in step S35 ends, in step S40, the ECU 23 determines whether or not the current operation state is in a predetermined correction region from the lean air-fuel ratio map in FIG. In this embodiment, the above-mentioned predetermined correction region is a range where the volumetric efficiency EV is between EVC and EVD and the engine speed Ne is between NeC and NeD. The correction area is set to be larger than the learning area, and EVC <EVA <EVB <EVD, and NeC <NeA <N
eB <NeD. In a region outside the correction region, there is no risk of misfiring, and no learning correction is required.

If the determination in step S40 is Yes, the ECU 23 calculates the target air-fuel ratio OAF from the target air-fuel ratio basic value OAFB retrieved from the lean air-fuel ratio map in step S41 by the following equation. In the following equation,
ΣKL is the sum of the cylinder-by-cylinder fuel correction coefficients KLm of each cylinder, and N is the number of cylinders of the engine 1. OAF = OAFB · (1 + ΣKL / N) On the other hand, if the determination in step S40 is No, E
The CU 23 determines in step S42 that the target air-fuel ratio basic value OAF
B is directly used as the target air-fuel ratio OAF.

After obtaining the target air-fuel ratio OAF in step S41 or S42, the ECU 23 calculates the actual air-fuel ratio RAF from the output signal of the air-fuel ratio sensor 12 in step S43 in FIG. Thereafter, the ECU 23 calculates a deviation ΔAF between the target air-fuel ratio OAF and the actual air-fuel ratio RAF in step S44, and performs a known PID control based on the deviation ΔAF in step S45 to perform a feedback correction coefficient KAF.
Calculate FB. Next, the ECU 23 proceeds to step S46.
Then, the set air-fuel ratio SAF is calculated by the following equation.

SAF = OAF · (1 + KFB) After calculating the set air-fuel ratio SAF, the ECU 23 determines in step S47 the fuel injection valve 3 based on the injector gain α, the volumetric efficiency EV, and the stoichiometric air-fuel ratio (14.7) by the following equation. The basic injection time TB is calculated. After calculating the basic injection time TB, the ECU 23 proceeds to step S48 where the cooling water temperature TW, the atmospheric pressure Ta, and the intake air temperature Ta are calculated.
Using the air-fuel ratio correction coefficient KDT and the invalid injection time TD corresponding to the above, the valve opening time TINJ is calculated by the following equation, and the fuel injection valve 3 is driven in step S49.

TINJ = KDT · TB + TD As described above, the target air-fuel ratio O
If the AF is too rich, two sampling periods (256
Lean gradually in each cycle) and approach the stable combustion limit. Further, when the engine enters the lean side beyond the stable combustion limit, the target air-fuel ratio OAF of the cylinder is enriched in one sampling cycle (128 cycles), and the misfire is immediately eliminated. When the combustion is at the stable combustion limit, neither the lean operation nor the rich operation is performed, and the target air-fuel ratio OA
F is kept as it is. Therefore, in the engine of this embodiment, will be an air-fuel ratio is always controlled to a stable combustion limit vicinity and can achieve significant reduction of the NO _X emissions with improved fuel economy. Note that the above-described control is performed for each cylinder because the air-fuel ratio near the stable combustion limit is different for each cylinder.

Now, the description of the concrete embodiment has been completed.
Embodiments of the present invention are not limited to this embodiment. For example, in the above-described embodiment, the present invention is applied to a V-type six-cylinder engine. However, the present invention may be applied to an engine having a different number of cylinders or cylinder arrangement, such as an in-line four-cylinder engine, or may be applied to EGR control or the like. You may. In addition, the threshold values, the initial values of the counters, and the like in the above control can be appropriately set, and the control procedure may be changed without departing from the gist of the present invention.

[0037]

In the combustion abnormality detecting method according to the first aspect of the present invention, the average angular acceleration is calculated for each cylinder. Not affected by Thus, for example, when applied to a lean burn control and the like, regardless of the complicated segment correction, the fuel injection control in the stable combustion limit becomes possible to perform with high accuracy, the improvement of the reduction and fuel efficiency of the NO _X emissions Can be planned.

Further, in the combustion abnormality detecting method according to the second aspect,
The current value of the angular acceleration instantaneous value and the previous value of the average angular acceleration value are each multiplied by a weighting constant and then summed to calculate the current value of the average angular acceleration value. Even if a prominent instantaneous angular acceleration value is detected, the average angular acceleration value is filtered and stable control can be realized.

According to the third aspect of the present invention, there is provided a method for detecting a combustion abnormality.
Since the value of the weighting constant by which the present value of the angular acceleration is multiplied by the present value is made larger than the value of the weighting constant by which the previous value of the average of the angular acceleration is multiplied, the followability of the average value of the angular acceleration with respect to the fluctuation of the angular acceleration becomes better, and Responsiveness is improved,
Control accuracy can be further improved.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of an engine control system to which a combustion abnormality detection method according to the present invention is applied.

FIG. 2 is a perspective view showing a rotor plate and a crank angle sensor.

FIG. 3 is a graph showing an output signal of a crank angle sensor.

FIG. 4 is a flowchart showing a procedure of a fuel injection control subroutine.

FIG. 5 is a flowchart showing a procedure of a stable combustion limit control subroutine.

FIG. 6 is a flowchart showing a procedure of a stable combustion limit control subroutine.

FIG. 7 is a flowchart showing a procedure of a stable combustion limit control subroutine.

FIG. 8 is a lean air-fuel ratio map using volume efficiency and engine speed as parameters.

FIG. 9 is a stoichiometric / rich air-fuel ratio map using volume efficiency and engine speed as parameters.

FIG. 10 is a graph showing the relationship between the change in angular acceleration and the volumetric efficiency at the time of misfire.

FIG. 11 is a map of a volume efficiency correction coefficient.

FIG. 12 is a graph showing the relationship between cylinder-by-cylinder acceleration index and volumetric efficiency at the time of misfire.

FIG. 13 is a graph showing a relationship between a cylinder-by-cylinder acceleration index, a fuel injection amount, and the like.

FIG. 14 is a graph showing a relationship between a cylinder-by-cylinder variation integrated value and a fuel injection increase coefficient.

[Explanation of symbols]

Reference Signs List 1 engine 3 fuel injection valve 12 O ₂ sensor 17 rotor plate 18 crank angle sensor 21 ECU 25 crankshaft

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Shogo Omori 5-33-8 Shiba, Minato-ku, Tokyo Inside Mitsubishi Motors Corporation (72) Inventor Ryo Hirako 5-33-8 Shiba, Minato-ku, Tokyo (56) References JP-A-4-81548 (JP, A) JP-A-5-340294 (JP, A) JP-A-4-11240 (JP, U)

Claims (3)

(57) [Claims] 1. A combustion abnormality detecting method for detecting a combustion abnormality of an internal combustion engine from crank rotation information of a multi-cylinder internal combustion engine, comprising: detecting a crank angle signal output at a predetermined crank position of the internal combustion engine. , based on the detected crank angle signals, each of the gas of the internal combustion engine
Identify which one of the cylinders
Calculating an angular acceleration instantaneous value in the combustion stroke of a constant, predetermined cylinder, and the current value of the angular acceleration instantaneous value of said predetermined cylinders, wherein each cylinder
Of the angular acceleration average values calculated and stored independently for each
Based on the previous value of the average value of the angular acceleration of the predetermined cylinder,
Calculating a current value of the angular acceleration average value of the cylinder, and the current value of the angular acceleration instantaneous value of the predetermined cylinder, the predetermined gas
With the deviation between the present value of the angular acceleration average value of the cylinder exceeds a predetermined threshold value, the look-containing and determining that there is abnormal combustion in the predetermined cylinder, a combustion anomaly independently the each cylinder A method for detecting a combustion abnormality in an internal combustion engine, wherein the determination is performed . Wherein said plant multiplied by the weighting constant, respectively
By adding the current value of the instantaneous angular acceleration value of the constant cylinder to the previous value of the average angular acceleration value of the predetermined cylinder , the predetermined
2. The method according to claim 1, wherein the current value of the average angular acceleration of the cylinder is calculated. 3. A value of a weighting constant by which a current value of the instantaneous angular acceleration value of the predetermined cylinder is multiplied by a current value is multiplied by a value of a weighting constant by which a previous value of the average angular acceleration value of the predetermined cylinder is multiplied. 3. The method for detecting combustion abnormality of an internal combustion engine according to item 2.