JPH07286546A - Rotational variation detecting method of internal combustion engine - Google Patents

Abstract

PURPOSE:To provide a rotational variation detecting method by which rotational variation of an internal combustion engine due to abnormal combustion and the like is detected, and operation and the like at the stable combustion limit of the engine is made possible. CONSTITUTION:An ECU 23 computes a rotational variation instantaneous value of each cylinder based on the ratio of rotating speed in combustion stroke of the former term to the latter term by the input signal from a crank angle sensor 18, and thereafter, computes a rotation variation index showing the variation, after correcting dispersion between cylinders and cycles. When the condition of the value over a threshold value is generated at times over prescribed times during a prescribed control period, it is judged that the air-fuel ratio of the cylinder already exceeds a stable combustion limit and runs in the lean side so as to be generating abnormal combustion. In this case, the EUC 23 searches a fuel injection increase quantity factor of each cylinder corresponding to a variation integrated value of each cylinder, and hence computes the opening time of the fuel injection valve 3 of the cylinder.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art In recent years, in automobile gasoline engines and the like, in order to reduce harmful exhaust gas components such as HC and CO and improve fuel efficiency, the air-fuel ratio of the air-fuel mixture is changed to the theoretical air-fuel ratio (14.7).
A much leaner lean burn engine has been proposed. In a lean burn engine, the ignition / combustion performance is improved by stratified charge, which enriches the air-fuel mixture flowing near the spark plug, and swirls, tumble, etc., which strengthen the turbulence of the air-fuel mixture in the combustion chamber. Also, in the lean region, nitrogen oxides (NO _x ) cannot be reduced by the three-way catalyst, and the emission amount becomes maximum near the air-fuel ratio 16 and decreases on the lean side, and the stable combustion limit (air-fuel ratio 22 to 23), the torque fluctuation exceeds the allowable limit on the lean side, so it is necessary to control the air-fuel ratio to a narrow range near the stable combustion limit. Therefore, instead of the O ₂ sensor that uniquely detects the stoichiometric air-fuel ratio, an air-fuel ratio sensor (LAFS: Linear A / F sensor) that can continuously detect the air-fuel ratio is used, and it is determined by the engine speed and the volume efficiency. The fuel injection amount is feedback-controlled so that the target air-fuel ratio is achieved.

[0003]

In the above-mentioned air-fuel ratio feedback control, the air-fuel ratio sensor controls the air-fuel mixture to the target air-fuel ratio, which simply controls the equivalence ratio between the fuel injection amount and the intake air amount. However, it does not control the combustion state of the air-fuel mixture. Further, the air-fuel ratio sensor has a characteristic that the detection accuracy is slightly deteriorated when the air-fuel ratio is largely shifted to the lean side. Therefore, when the target air-fuel ratio is set near the stable combustion limit, an abnormality may occur in the combustion of the air-fuel mixture due to fluctuations in the outside temperature, humidity, etc., leading to intermittent misfires. In this case, as a matter of course, the fuel consumption is deteriorated and the harmful exhaust gas is increased, and the engine vibration and the torque fluctuation are frequently generated, which gives the occupant considerable discomfort. Therefore, conventionally, the target air-fuel ratio must be set to the rich side of the combustion stability limit in order to provide a margin for combustion fluctuations and misfires, and it is possible to pursue reduction of NO _X emissions and improvement of fuel efficiency to the utmost limit. could not.

The present invention has been made in view of the above circumstances,
An object of the present invention is to provide a rotation fluctuation detecting method for detecting a rotation fluctuation of an internal combustion engine due to abnormal combustion or the like, and thereby to enable the engine to operate at a stable combustion limit.

[0005]

Therefore, a rotation fluctuation detecting method according to claim 1 of the present invention is a rotation fluctuation detecting method for detecting a rotation fluctuation in an internal combustion engine from crank rotation information of the internal combustion engine, wherein: The combustion stroke period of the internal combustion engine is 2
To divide and specify the first half of the combustion stroke and the second half of the combustion stroke,
Based on the step of detecting the crank angle signal output at the three crank angle positions and the detected crank angle signal,
A step of calculating an instantaneous value of rotational fluctuation corresponding to the relationship between the rotational speed in the first half of the combustion stroke and the rotational speed in the latter half of the combustion stroke, and it is determined that there is rotational fluctuation in the internal combustion engine based on the calculated instantaneous value of rotational fluctuation. And a step of performing.

Further, a rotation fluctuation detecting method according to a second aspect of the present invention is a rotation fluctuation detecting method for detecting a rotation fluctuation in the internal combustion engine from crank rotation information of the internal combustion engine, wherein the combustion stroke of the internal combustion engine is in the early stage. And a step of detecting a crank angle signal output at a predetermined crank angle position that respectively defines the combustion stroke late stage, and the rotation speed of the combustion stroke early period and the combustion stroke late period based on the detected crank angle signal. And a step of determining that there is a rotation fluctuation in the internal combustion engine based on the calculated rotation fluctuation instantaneous value.

The rotation fluctuation detecting method according to claim 3 of the present invention is the rotation fluctuation detecting method according to claim 1 or 2, wherein the rotation angle in the first half of the combustion stroke is α and the rotation angle in the second half of the combustion stroke is Let β be the time required for the internal combustion engine to rotate in the first half of the combustion stroke, and Tβ be the time required to rotate in the latter half of the combustion stroke.
= Β / α-Tβ / Tα).

A rotation fluctuation detecting method according to a fourth aspect of the present invention is the rotation fluctuation detecting method according to the first to third aspects, wherein the rotation fluctuation instantaneous value of the first cylinder in the multi-cylinder internal combustion engine and the first fluctuation Calculating the rotation fluctuation index, which is the amount of change in the rotation fluctuation instantaneous value, from the deviation from the rotation fluctuation instantaneous value of the second cylinder that was in the combustion stroke immediately before this cylinder, and the internal combustion engine according to the rotation fluctuation index. Determining that rotation fluctuation has occurred in each cylinder of the engine.

A rotation fluctuation detecting method according to a fifth aspect of the present invention is the rotation fluctuation detecting method according to any one of the first to fourth aspects, wherein an instantaneous value of rotation fluctuation of the first cylinder and its average in a multi-cylinder internal combustion engine. Including a step of calculating a rotation fluctuation index which is a change amount of the rotation fluctuation instantaneous value from a deviation from the value, and a step of determining that a rotation fluctuation has occurred in each cylinder of the internal combustion engine according to the rotation fluctuation index. .

Further, a rotation fluctuation detecting method according to a sixth aspect of the present invention is the rotation fluctuation detecting method according to the fourth or fifth aspect, wherein the rotation fluctuation is within a predetermined sampling interval, and the rotation fluctuation index has a predetermined threshold value. It is judged when the number of times exceeds. A rotation fluctuation detecting method according to claim 7 of the present invention is the rotation fluctuation detecting method according to any one of claims 1 to 3.
Rotational fluctuation of each cylinder in the internal combustion engine is detected from crank rotation information of the multi-cylinder internal combustion engine, and the combustion stroke is reached immediately after the end of the latter half of the combustion stroke of the first cylinder and immediately after the first cylinder. It is configured with a crank angle signal that is output so as to define both the start time and the start time of the combustion stroke of the cylinder.

[0011]

In the method for detecting rotational fluctuation according to the first aspect of the present invention, the combustion stroke is calculated from the crank angle signals output at three crank angle positions that divide the combustion stroke period of the internal combustion engine into the combustion stroke early period and the combustion stroke late period. After calculating the rotation fluctuation instantaneous value corresponding to the relationship between the rotation speed in the first half of the stroke and the rotation speed in the latter half of the combustion stroke, it is determined that there is a rotation fluctuation in the internal combustion engine based on this rotation fluctuation instantaneous value. That is, when a combustion abnormality such as combustion fluctuation occurs in a certain cylinder, the relationship between the rotation speed in the first half of the combustion stroke and the rotation speed in the second half of the combustion stroke of that cylinder fluctuates. Fluctuations are detected.

Further, in the rotation fluctuation detecting method according to claim 2,
From the crank angle signal output at a predetermined crank angle position that defines the combustion stroke early period and the combustion stroke late period of the internal combustion engine,
After calculating the rotation fluctuation instantaneous value corresponding to the ratio of the rotation speed in the first half of the combustion stroke to the rotation speed in the second half of the combustion stroke, it is determined that there is rotation fluctuation in the internal combustion engine based on this rotation fluctuation instantaneous value. That is, when combustion abnormality such as combustion fluctuation occurs in a cylinder, the ratio of the rotation speed in the first half of the combustion stroke to the rotation speed in the second half of the combustion stroke of the cylinder fluctuates, and as a result, the instantaneous value of rotation fluctuation also fluctuates. Fluctuations are detected.

Further, according to the rotation fluctuation detecting method of claim 3,
The instantaneous value of the rotational fluctuation is calculated from the deviation between the rotational angle ratio (β / α) and the rotational speed ratio (Tβ / Tα) in the pre- and post-combustion strokes, but combustion is normally performed after the crank angle signal detecting means is assembled. In this case, since the rotation angle ratio (β / α) is always constant, the rotation fluctuation can be detected based on the fluctuation of the rotation speed ratio (Tβ / Tα).

Further, according to the rotation fluctuation detecting method of claim 4,
An instantaneous value of the rotational fluctuation of the first cylinder of the multi-cylinder internal combustion engine;
Since the rotation fluctuation index is calculated from the deviation from the rotation fluctuation instantaneous value of the second cylinder that was in the combustion stroke immediately before the cylinder No., the rotation fluctuation of the cylinder that reaches the combustion stroke immediately after the cylinder in which the rotation fluctuation occurs is detected. In doing so, the effects of the rotational fluctuations are excluded.

Further, according to the rotation fluctuation detecting method of claim 5,
Since the rotational fluctuation index is detected from the deviation between the instantaneous value of rotational fluctuation and the average value of the instantaneous value of rotational fluctuation of that cylinder, the difference in the manufacturing or mounting error of the crank angle position detection means between the cylinders is the detection accuracy. It has no effect. Further, in the rotation fluctuation detecting method according to claim 6, since it is determined that the rotation fluctuation occurs when the rotation fluctuation index exceeds the threshold value a predetermined number of times or more, the rotation fluctuation index or noise, which is equal to or larger than the threshold value, caused by the influence of the change of the road surface. Are removed.

Further, in the rotation fluctuation detecting method according to claim 7,
A multi-cylinder internal combustion engine is provided with a crank angle signal that is output to define both the end point of the latter half of the combustion stroke of the first cylinder and the start time of the first half of the combustion stroke of the cylinder that reaches the combustion stroke after the first cylinder. In, the rotational fluctuation of the front cylinder is detected by detecting a crank angle signal of a number smaller than the number of cylinders times the crank angle signal required for dividing the combustion stroke period of one cylinder into the first period and the second period. .

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a schematic configuration diagram of an engine control system to which a rotation fluctuation detecting method according to the present invention is applied. Figure 1
In the figure, reference numeral 1 denotes an in-line four-cylinder gasoline engine for an automobile (hereinafter, simply referred to as an engine), in which a combustion chamber, an intake system, an ignition system and the like are designed for lean burn. In the intake port 2 of the engine 1, a fuel injection valve 3 is provided for each cylinder.
Via an intake manifold 4 to which an air cleaner 5, an air flow sensor 6, a throttle valve 7, I
An intake pipe 9 including an SC (idle speed controller) 8 and the like is connected. An exhaust pipe 11 including an O ₂ sensor 12, a three-way catalyst 13, and a muffler (not shown) is connected to the exhaust port 10 via an exhaust manifold 11. The engine 1 includes a combustion chamber 15 and a spark plug 1
6 is arranged, and a crank angle sensor 18 for detecting the rotation of the rotor plate 17 directly attached to the crankshaft 25 is attached. As shown in FIG. 2, the rotor plate 17 is provided with two vanes 17a and 17b having an angular width of 70 ° at 180 ° intervals.
As shown in FIG. 3, a section α of 110 ° (BTDC 5 ° to ATDC 105 °) including the top dead center (TDC) of each cylinder.
Followed by 70 ° (ATDC105 ° ~ ATDC1
75 °) section β is detected. In FIG. 1, 19 is a throttle sensor for detecting the opening θTH of the throttle valve 7, 20 is a water temperature sensor for detecting the cooling water temperature TW, 21 is an atmospheric pressure sensor for detecting the atmospheric pressure Ta, and 22 is an intake air temperature T.
It is an intake air temperature sensor that detects a.

An input / output device (not shown) and a storage device (ROM, RA) incorporating a large number of control programs are provided in the passenger compartment.
M, BURAM, etc.), central processing unit (CPU), timer counter, etc., ECU (engine control unit)
23 is installed and controls the engine 1 comprehensively. Detection information from the various sensors described above is input to the input side of the ECU 23. The ECU 23 calculates optimum values such as the fuel injection amount and the ignition timing from these detection information,
The fuel injection valve 3 and the spark plug 16 are driven. 2 in the figure
Reference numeral 4 is an ignition unit that outputs a high voltage to the spark plug 16 in response to a command from the ECU 23.

The control procedure in this embodiment will be described below with reference to the control flowcharts of FIGS. 4 to 6 and the maps and graphs of FIGS. 7 to 10. 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 is started, the ECU 2
First, in step S1, 0 is loaded into the RAM with the driving information from the above-mentioned sensors. Next, in step S2, the ECU 23 determines whether or not feedback control should be performed based on the throttle opening θTH, the time change rate thereof, the volumetric efficiency EV, the elapsed time after engine start, the cooling water temperature TW, and the like.
The volumetric efficiency EV is calculated by calculating the 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 correcting it by the atmospheric pressure Pa, the intake air temperature Ta, etc. Required by If this 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. The lean burn control is performed in an operating region where the required torque is small, such as during idle operation or constant speed running.

If the determination in step S3 is Yes, the ECU 23 determines in step S4 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 of FIG. next,
In step S5, the ECU 23 controls the injection amount (valve opening time TINJ) of the fuel injection valve 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 stoichio / rich air-fuel ratio map of FIG. Set
In step S7, the valve opening time TINJ of the fuel injection valve 3 is feedback-controlled based on the output voltage of the O ₂ sensor 12. If the determination in step S2 is No, E
In step S8, the CU 23 sets the target air-fuel ratio OAF on the basis of the stoichio / rich air-fuel ratio map. next,
After calculating the basic injection amount TINJB from the target air-fuel ratio OAF and the intake air amount A / N in step S9, the ECU 23 corrects the acceleration increase amount, the cold increase amount, etc., and in step S10,
The open time of the fuel injection valve 3 is controlled by open loop.

Now, the above-mentioned stable combustion limit control subroutine is repeatedly executed in the following procedure every time the crank interrupt signal SGT is input. When this subroutine is started, the ECU 23 firstly proceeds to step S20 of FIG.
It is determined whether or not the current driving state is in a predetermined learning area. This determination is made, for example, based on whether or not the current operating state is in the learning region shown by cross-hatching in the lean air-fuel ratio map of FIG. 7. If this determination is No, the step of FIG. In step S36, the following steps are executed to drive and control the fuel injection valve 3. In this embodiment, the volumetric efficiency EV is between EVA and EVB,
Moreover, the range between the engine speed Ne and NeA and NeB is the above-mentioned predetermined learning region.

If the determination in step S20 is Yes, the ECU 23 determines in step S22 the predetermined value TCDX.
After subtracting 1 from the countdown timer TCD whose initial value is (256 in this embodiment), in step S23,
The rotational fluctuation instantaneous value Vmn in the nth combustion stroke of the mth cylinder in the ignition order is calculated by the following formula. In the case of this embodiment, the ignition order of each cylinder is 1-3-4-2.

Vmn = (β / α-Tβ / Tα) · K where α (fixed value) is the crank angle sensor 18 OFF
Is a section (110 ° including the compression top dead center), β (fixed value) is a section in which the crank angle sensor 18 is ON (70 ° following β), and Tα and Tβ are the crankshaft 25.
Is a time required to rotate the sections α and β, and K is a correction coefficient (> 0) set on the basis of a map having the volume efficiency EV and the engine speed Ne as parameters. When the combustion is normally performed, the rotation of the crankshaft 25 is relatively slow in the first half of the combustion stroke (section α) which is affected by the compression stroke and the combustion is still insufficient.
Further, in the latter half of the combustion stroke (section β) where combustion is completely performed, the rotation of the crankshaft 25 is relatively fast, so β
/ Α> Tβ / Tα, and the rotational fluctuation instantaneous value Vmn becomes a positive value. Further, when a misfire occurs, it is necessary to perform the compression work of the other cylinders without the work of combustion, so the rotation of the crankshaft 25 gradually slows down and β / α <T
β / Tα, and the instantaneous value of rotational fluctuation Vmn becomes a negative value.

When the calculation of the instantaneous value of rotational fluctuation Vmn is completed, E
Next, in step S24, the CU 23 eliminates the variation between the cylinders and the variation between the cycles, and in step S24, the rotation variation instantaneous value Vm- of the m-1th cylinder in the previous combustion stroke.
The cylinder-by-cylinder rotational fluctuation index ΔVmn is calculated from the deviation from 1, n. ΔVmn = (Vmn-Emn)-(Vm-1, n-Em-1, n) Here, Emn is a low-pass filter-like average value and is calculated using the following equation. Note that KF in the following equation is a filter coefficient, and is 0.95 in this embodiment.

Emn = KF.Em, n-1 + (1-KF) .Vmn After calculating the cylinder-by-cylinder rotational fluctuation index ΔVmn, the ECU 23
Next, in step S25, the cylinder-by-cylinder rotational fluctuation index ΔVmn
Is below a predetermined threshold value ΔVx, and if the determination is No, the process proceeds to step S30 in FIG. The threshold value ΔVx is set to a value that is sufficiently low with respect to the rotational fluctuation associated with normal combustion so that the cylinder-by-cylinder rotational fluctuation index ΔVmn falls only when misfire occurs.

On the other hand, when the determination in step S25 is Yes, the misfire number counter CMF is set to 1 in step S26.
After adding, the cylinder-by-cylinder variation integrated value Σ
The cylinder-by-cylinder rotational fluctuation index ΔVmn is added to ΔVm, and the process proceeds to step S30 in FIG. The misfire counter CMF
The cylinder-by-cylinder variation integrated value ΣΔVm is reset to the initial value 0 each time the countdown timer TCD is reset to the initial value, as shown in FIG. 9.

The ECU 23, in step S30 of FIG.
It is determined whether or not the countdown timer TCD has become 0, that is, whether or not the operation of the TCDX cycle has been performed within the learning region. If the determination is No, the process proceeds to step S36 described later, and the fuel injection valve 3 To drive. Incidentally, in the present embodiment, even if the operating state is once out of the learning region, the misfire number counter CMF and the cylinder-by-cylinder variation integrated value ΣΔV.
m and the countdown timer value TCD are stored in the RAM, and when the learning area is entered again, the ECU 23 continues to integrate and subtract each value.

When the TCDX cycle is performed in the learning region and the determination in step S30 is Yes, the ECU
23 determines in step S31 whether or not the value of the misfire number counter CMF is 0. Then, if this determination is Yes, the ECU 23 determines that the air-fuel ratio of the cylinder is still on the rich side with respect to the stable combustion limit, and step S32 is performed.
Then, a predetermined weight reduction correction value KD (0.2% in this embodiment)
By using the following formula, the feedback coefficient for each cylinder KmFD
To update. In the case of the present embodiment, the cylinder-by-cylinder feedback coefficient KmFD takes a value in the range of 0% to 10% and B
It is stored in a non-volatile memory such as URAM.

KmFD = KmFD-KD On the other hand, if the determination in step S31 is No, the ECU
23, in step S33, it is determined whether or not the value of the misfire number counter CMF is greater than or equal to the threshold value CMFX (three times in this embodiment). If this determination is No, the ECU
Reference numeral 23 determines that the air-fuel ratio of the cylinder is at the stable combustion limit, holds the cylinder-by-cylinder feedback coefficient KmFD of the fuel injection valve 3 at present, and continues the operation at the stable combustion limit.

When the determination in step S33 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 S34, the cylinder-by-cylinder increase correction value Kam corresponding to the cylinder-by-cylinder fluctuation integrated value ΣΔVm is set based on the map of FIG. 10, and the cylinder-by-cylinder feedback coefficient KmFD is updated by the following equation. The cylinder-by-cylinder increase correction value Kam increases linearly as the cylinder-by-cylinder variation integrated value ΣΔVm increases, as shown in FIG.

KmFD = KmFD + Kam When the cylinder-specific feedback coefficient KmFD is updated in step S32 or step S34, the ECU 23 resets the misfire number counter CMF, the cylinder-specific fluctuation integrated value ΣΔVm, and the countdown timer TCD in step S35. When the resetting of the counters and timers in step S35 is completed, the ECU 23 determines in step S36
Then, it is determined from the lean air-fuel ratio map of FIG. 7 whether or not the current operating state is within the predetermined correction range. In this embodiment, the volumetric efficiency EV is between EVC and EVD, and the engine speed Ne is between NeC and NeD, which is the above-mentioned predetermined correction region. The correction area is set larger than the learning area, and if EVC <EVA <EVB <EVD, N
eC <NeA <NeB <NeD. Then, there is no risk of misfire in a region outside the correction region, and learning correction is not required.

If the determination in step S36 is Yes, the ECU 23 determines in step S37 the fuel correction coefficient KL.
Is calculated by the following formula. If the determination is No, the ECU 23 sets the fuel correction coefficient KL to 1 in step S38. KL = 1 + KmFD When the fuel correction coefficient KL is obtained in step S37 or step S38, the ECU 23 determines in step S39 the opening time of the fuel injection valve 3 of the cylinder based on the target air-fuel ratio OAF and the volumetric efficiency EV by the following equation. TINJ is calculated, and the fuel injection valve 3 is driven in step S40. In the following equation, KT is various correction factors, Vol is cylinder volume, and TD is invalid injection time.

TINJ = KT.multidot.OAF.multidot.EV.multidot.Vol.KL + TD As a result, in the correction region, when the target air-fuel ratio OAF is too rich, it is gradually leaned every TCDX (256) cycles and approaches the stable combustion limit. Go on. Also,
When the fuel enters the lean side beyond the stable combustion limit, the air-fuel ratio of the cylinder is enriched at once, and misfire is immediately eliminated. The control described above is performed for each cylinder,
This is because the air-fuel ratio at the stable combustion limit differs for each cylinder.

Above, the description of the concrete embodiment is finished.
Aspects of the invention are not limited to this example. For example, although the above-described embodiment applies the present invention to an in-line four-cylinder engine, it may be applied to various engines having different numbers of cylinders and their arrangement, such as a single-cylinder engine and a V-type six-cylinder engine. It may be applied to various controls other than lean burn control such as EGR control and ignition timing control.

Further, the initial value of the fuel injection amount in the stable combustion limit control subroutine may be directly searched from the fuel injection amount map instead of being calculated from the target air-fuel ratio searched from the lean air-fuel ratio map. Further, the target air-fuel ratio of the lean air-fuel ratio map may be learned and corrected after correcting the fuel injection amount. Further, in the above embodiment, when the value of the misfire number counter is within the predetermined range (1 and 2), the fuel injection amount is held at present, but it is less than the predetermined value (for example, 3). In some cases, it may be uniformly made lean. Further, each threshold value in the above control, the initial value of the countdown timer, and the like can be appropriately set, and the calculation procedure can be changed without departing from the gist of the present invention.

[0038]

According to the rotation fluctuation detecting method of the first aspect of the present invention, the combustion stroke of the internal combustion engine is divided into the first half and the second half, and the rotation fluctuation instantaneous value is calculated from the difference in the rotation speeds. The rotation fluctuation can be detected only by detecting the crank angle position in the combustion stroke at three points, and the configuration of the crank angle detecting means, the calculating means and the like becomes extremely simple.

According to the method for detecting rotational fluctuation of the present invention, the instantaneous value of rotational fluctuation is calculated based on the ratio of the rotational speed in the first half of the combustion stroke to the rotational speed in the second half of the combustion stroke in the internal combustion engine. When a combustion abnormality such as a fluctuation occurs, the fluctuation of the rotation fluctuation instantaneous value becomes large, and the rotation fluctuation can be easily determined. Further, in the rotation fluctuation detecting method according to the third aspect, the rotation fluctuation instantaneous value is calculated from the deviation between the rotation angle ratio (β / α) and the rotation speed ratio (Tβ / Tα) in the pre- and post-combustion stroke periods. When the combustion is normally performed after the detection means is assembled, the rotation angle ratio (β / α) is always constant. Therefore, when the rotation speed ratio (Tβ / Tα) fluctuates due to combustion abnormality such as combustion fluctuation. The instantaneous value of rotational fluctuation suddenly changes,
Rotational fluctuations can be determined very easily.

Further, in the rotation fluctuation detecting method according to claim 4,
The rotation fluctuation index is calculated from the rotation fluctuation instantaneous value of the first cylinder of the multi-cylinder internal combustion engine and the rotation fluctuation instantaneous value of the second cylinder in the combustion stroke immediately before the first cylinder. When the rotational fluctuation detection of the cylinder that is about to go into the combustion stroke immediately after the occurrence of the cylinder is detected, the influence of the rotational fluctuation is excluded, and more accurate rotational fluctuation can be detected.

Further, according to the rotation fluctuation detecting method of claim 5,
Since the rotational fluctuation index is detected from the difference between the instantaneous value of rotational fluctuation and the average value of the instantaneous value of rotational fluctuation of that cylinder, the mounting error of the crank angle signal detection means between each cylinder can be ignored, and the accuracy of determination of rotational fluctuation is improved. To do. Further, in the rotation fluctuation detecting method according to the sixth aspect, since it is determined that the rotation fluctuation occurs when the rotation fluctuation index exceeds the threshold value a predetermined number of times, the rotation fluctuation index or noise that is equal to or larger than the threshold value caused by the influence of the change of the road surface or the like is detected. As a result, the accuracy of the rotation fluctuation determination is improved.

Further, according to the rotation fluctuation detecting method of claim 7,
In the multi-cylinder internal combustion engine, the crank angle signal is provided to specify both the end of the combustion stroke of the first cylinder and the start of the combustion stroke of the cylinder that reaches the combustion stroke after the first cylinder. Rotational fluctuation can be detected by detecting a crank angle signal of a number smaller than the number of cylinders of the crank angle signal required for dividing the combustion stroke period of one cylinder into the first period and the second period. The configuration of the means and the like becomes simple.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of an engine control system to which a rotation fluctuation detecting 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 lean air-fuel ratio map with volume efficiency and engine speed as parameters.

FIG. 8 is a stoichio / rich air-fuel ratio map with volume efficiency and engine speed as parameters.

FIG. 9 is a graph showing the relationship between rotation fluctuation and fuel injection amount and the like.

FIG. 10 is a graph showing a relationship between a fluctuation integrated value and a fuel injection amount increase coefficient.

[Explanation of symbols]

1 Engine 3 Fuel Injection Valve 12 O ₂ Sensor 17 Rotor Plate 18 Crank Angle Sensor 21 ECU 25 Crank Shaft

Claims (7)

[Claims] 1. A rotation fluctuation detecting method for detecting a rotation fluctuation in an internal combustion engine from crank rotation information of the internal combustion engine, wherein a combustion stroke period of the internal combustion engine is divided into two, a combustion stroke early period and a combustion stroke late period. To detect the crank angle signals output at three crank angle positions, and the relationship between the rotation speed in the first half of the combustion stroke and the rotation speed in the second half of the combustion stroke based on the detected crank angle signals. A method for detecting rotational fluctuation of an internal combustion engine, comprising: a step of calculating a corresponding instantaneous rotational fluctuation value; and a step of determining that the internal combustion engine has rotational fluctuation based on the calculated instantaneous value of rotational fluctuation. 2. A rotation fluctuation detecting method for detecting a rotation fluctuation in the internal combustion engine from crank rotation information of the internal combustion engine, wherein a predetermined crank angle for defining a combustion stroke early period and a combustion stroke late period of the internal combustion engine, respectively. Detecting the crank angle signal output at the position, and calculating the instantaneous value of rotation fluctuation corresponding to the ratio of the rotation speed in the first half of the combustion stroke to the rotation speed in the second half of the combustion stroke based on the detected crank angle signal. A method for detecting a rotational fluctuation of an internal combustion engine, comprising: a step; and a step of determining that the internal combustion engine has a rotational fluctuation based on the calculated instantaneous value of the rotational fluctuation. 3. The rotation angle in the first half of the combustion stroke is α,
When the rotation angle in the latter half of the combustion stroke is β, the time required for the internal combustion engine to rotate in the first half of the combustion stroke is Tα, and the time required for rotation in the second half of the combustion stroke is Tβ, the instantaneous value of the rotational fluctuation Vn
Is calculated based on the formula Vn = β / α-Tβ / Tα.
A method for detecting rotational fluctuation of an internal combustion engine as described. 4. In a multi-cylinder internal combustion engine, the rotational fluctuation instantaneous value is calculated from the deviation between the rotational fluctuation instantaneous value of the first cylinder and the rotational fluctuation instantaneous value of the second cylinder in the combustion stroke immediately before the first cylinder. 2. The method according to claim 1, further comprising: a step of calculating a rotation fluctuation index that is a change amount of a value; and a step of determining that a rotation fluctuation has occurred in each cylinder of the internal combustion engine according to the rotation fluctuation index. 4. A method for detecting fluctuations in rotation of an internal combustion engine according to any one of 3 to 3. 5. In a multi-cylinder internal combustion engine, a step of calculating a rotation fluctuation index, which is a change amount of a rotation fluctuation instantaneous value, from a deviation between a rotation fluctuation instantaneous value of the first cylinder and an average value thereof, 5. The method according to claim 1, further comprising the step of determining that a rotation fluctuation has occurred in each cylinder of the internal combustion engine according to an index. 6. The rotation fluctuation of the internal combustion engine according to claim 4, wherein the rotation fluctuation is determined when the rotation fluctuation index exceeds the threshold value a predetermined number of times or more within a predetermined sampling section. Detection method. 7. A rotation fluctuation detecting method for detecting a rotation fluctuation of each cylinder in the internal combustion engine from crank rotation information of a multi-cylinder internal combustion engine, the method comprising a first cylinder combustion stroke end point and the first cylinder. 4. The internal combustion engine according to claim 1, further comprising a crank angle signal that is output to define both the start time and the start time of the combustion stroke of the cylinder that reaches the combustion stroke immediately after the cylinder. Rotational fluctuation detection method.