JP2907001B2 - Lean combustion control and failure determination device for 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 lean burn control and failure determination system for an internal combustion engine, and more particularly to a device capable of operating the engine stably in a lean air-fuel ratio region and specially detecting a failure in an engine fuel supply system and an ignition system. The present invention relates to a lean-burn control and a failure determination device capable of making a quick and reliable determination without using any failure determination means.

[0002]

2. Description of the Related Art In recent years, in gasoline engines for automobiles and the like, the fuel is leaner than the stoichiometric air-fuel ratio (14.7).
The engine is operated in the air-fuel ratio region on the side to reduce toxic components such as nitrogen oxides contained in exhaust gas and improve fuel efficiency. The emission amount of nitrogen oxides decreases as the air-fuel ratio increases on the fuel-lean side from the vicinity of the air-fuel ratio 16. On the other hand, if the air-fuel ratio is burned in an ultra-lean air-fuel ratio region (stable combustion limit region) where the air-fuel ratio is 20 or more, the combustion is not stabilized and torque fluctuations are likely to occur.

[0003] In order to obtain stable combustion, stratified intake is performed so that the air-fuel mixture flowing near the spark plug has an air-fuel ratio richer than that of the surroundings, thereby improving the ignition performance of the air-fuel mixture. It is effective to generate a strong swirling flow (swirl, tumble) in the air-fuel mixture sucked into the combustion chamber, for example, by devising the shape of the combustion chamber. However, even when such measures are taken, it is difficult to obtain stable combustion in a region where the air-fuel ratio exceeds the value of 22 to 23.

[0004]

Accordingly, in a lean burn engine, the air-fuel ratio is feedback-controlled to a target air-fuel ratio within a narrow range of the air-fuel ratios 22 to 23 corresponding to the stable combustion limit. The challenge is to pursue exhaust gas purification and fuel efficiency to the utmost. However, the linear air-fuel ratio sensor usually used for detecting the actual air-fuel ratio in the air-fuel ratio feedback control may have lower detection accuracy when the air-fuel ratio shifts to the lean side. For this reason, when the target air-fuel ratio is set near the stable combustion limit, abnormalities in combustion of the air-fuel mixture and intermittent misfires may occur due to fluctuations in the outside air temperature, humidity, and the like. When such poor combustion occurs, fuel economy is deteriorated and harmful exhaust gas is increased, and engine vibrations and torque fluctuations occur frequently, which causes discomfort to the occupant.

Conventionally, therefore, the target air-fuel ratio has to be set relatively high in order to provide a margin for poor combustion or misfire, and the reduction of nitrogen oxide emissions and the improvement of fuel efficiency have been reduced to the utmost. Could not pursue. Also, during operation of the engine in the lean air-fuel ratio region, particularly in the ultra-lean air-fuel ratio region, a failure of the fuel supply system or the ignition system of the engine, such as a decrease in the fuel supply amount due to clogging of the fuel injection valve or a combustion impossible state due to poor ignition. If this occurs, the driving feeling is significantly impaired compared to the case where a similar failure occurs during operation of the engine in the stoichiometric air-fuel ratio range. Therefore, it is desirable that the cause of this kind of failure be investigated as soon as possible.

Accordingly, the present invention provides a lean combustion control and control system for an internal combustion engine that enables stable engine operation in a lean air-fuel ratio region and also enables reliable determination of engine fuel supply system and ignition system failures. An object of the present invention is to provide a failure determination device.

[0007]

According to a first aspect of the present invention, there is provided a lean burn control and failure determination device for an internal combustion engine, comprising: a rotation information detection unit for detecting rotation information of the internal combustion engine; and a rotation information detection unit. A combustion state determination unit for determining a variation amount of the rotation information for each cylinder based on the detected rotation information, comparing the variation amount of the rotation information with a threshold, and repeatedly determining whether the combustion state is good or bad in each cylinder; Each time it is determined by the combustion state determination means that the combustion state is good, the air-fuel ratio of the air-fuel mixture supplied to the cylinder according to this determination is changed to the fuel lean side, while the combustion state is poor. Each time the determination is made, the air-fuel ratio changing means for changing the air-fuel ratio to the fuel-rich side and the air-fuel ratio changing to the fuel-rich side by the air-fuel ratio changing means are continuously performed a predetermined number of times for the same cylinder. When Characterized in that it comprises a failure determining means for determining that a failure has occurred in the fuel supply system or an ignition system associated with the cylinder.

According to the second aspect of the invention, the rotation information detecting means detects the rotation angular acceleration of the crankshaft of the internal combustion engine as rotation information. According to the third aspect of the present invention, the present apparatus further includes control changing means for changing the control content of the internal combustion engine according to the failure determination by the failure determination means. In the third aspect of the present invention,
In other words, the control changing means stops the supply of fuel to the cylinder determined to have failed. According to this preferred aspect, the failure is determined.
Engine emissions caused by continued fuel supply to cylinders
It is possible to prevent deterioration of air characteristics and fuel consumption characteristics.

In the invention according to claim 3, it is preferable that
The control change means changes the air-fuel ratio of the air-fuel mixture supplied to the cylinders other than the cylinder determined to be faulty from the lean air-fuel ratio to the stoichiometric air-fuel ratio or an air-fuel ratio near the stoichiometric air-fuel ratio. This preferred embodiment
According to the above, it is possible to suppress engine torque fluctuations when a failure occurs.
You. In the invention according to claim 1, the failure determination means includes:
It is preferable to store the failure determination result in a nonvolatile manner. This good
According to a suitable mode, a failure diagnosis device usually mounted on a vehicle
In the pursuit of the cause of failure, it becomes possible to identify the failure part more
It is convenient.

[0010] In the first aspect of the present invention, preferably
Means that the air-fuel ratio changing means changes the air-fuel ratio toward the fuel-lean side by a first predetermined value, and changes the air-fuel ratio toward the fuel-rich side by a second predetermined value larger than the first predetermined value. . This good
According to a suitable embodiment, stable combustion can be obtained at the stable combustion limit.
To pursue exhaust and fuel efficiency to the utmost
And the fuel becomes lean over the stable combustion limit.
In this case, a stable combustion state can be achieved immediately. Claim
In the invention as set forth in claim 1, preferably, the combustion state determining means includes a variation amount of the rotation information based on a rotation variation instantaneous value in a combustion stroke of each cylinder obtained from the rotation information and an average value of the rotation variation instantaneous value. Ask for. According to this preferred embodiment
For example, it is necessary to find the fluctuation amount that reflects the engine rotation fluctuation well.
And the amount of variation between cylinders and cycles
Fluctuations can be eliminated, and therefore lean burn control and
Can be performed properly.

In the first aspect of the present invention, preferably
When the combustion state determination means determines that the number of times the fluctuation amount of the rotation information exceeds the threshold value within a predetermined period is equal to or greater than a first predetermined number, it is determined that the combustion state in the cylinder related to this determination is poor. On the other hand, when it is determined that the number of times is less than the second predetermined number of times, which is smaller than the first predetermined number of times, it is determined that the combustion state in the cylinder related to this determination is good. This good
According to the appropriate aspect, the quality of the combustion state can be properly determined,
Thin combustion control and failure determination can be suitably performed.

More preferably, when the combustion state determination means determines that the number of times that the fluctuation amount of the rotation information exceeds the threshold value within the predetermined period is equal to or more than the second predetermined number and less than the first predetermined number, The fuel ratio changing means maintains the air-fuel ratio of the air-fuel mixture supplied to the cylinder according to the determination. This preferred embodiment
According to this, the stable combustion limit state can be continued.

[0013]

During operation of the internal combustion engine, rotation information of the engine, for example, a rotation angular acceleration of the crankshaft, is detected by rotation information detection means. Required every time. Then, the combustion state determination means compares the fluctuation amount of the rotation information with the threshold value and repeatedly determines the quality of the combustion state in each cylinder.

[0014] Preferably, the combustion state determination means obtains the fluctuation amount of the rotation information based on the rotation fluctuation instantaneous value in the combustion stroke of each cylinder obtained from the rotation information and the average value of the rotation fluctuation instantaneous value. Further, when the combustion state determination means determines that the number of times that the fluctuation amount of the rotation information exceeds the threshold value within a predetermined period is equal to or greater than a first predetermined number, the combustion state in the determined cylinder is determined to be defective. While the number of times is the first
When it is determined that the number is less than the second predetermined number, which is smaller than the predetermined number, it is determined that the combustion state in the cylinder related to the determination is good.

As described above, when the combustion state determining means determines that the combustion state is good, the air-fuel ratio changing means determines the air-fuel ratio of the air-fuel mixture supplied to the cylinder according to this determination as fuel-lean. Change to the side. Preferably, the change of the air-fuel ratio to the lean side is performed by a first predetermined value. As a result, as long as a favorable combustion state continues, the air-fuel ratio is gradually made lean, the emission of nitrogen oxides from the engine is reduced, and the fuel efficiency is improved. On the other hand, when it is determined that the combustion state is poor, the air-fuel ratio is changed to the fuel rich side, preferably by a second predetermined value larger than the first predetermined value, whereby the combustion state is improved and the torque fluctuation is improved. Is prevented. Therefore, stable combustion is achieved even in the lean air-fuel ratio region or the ultra-lean air-fuel ratio region.

When the air-fuel ratio is changed to the fuel rich side in accordance with the determination of the poor combustion state, usually, the poor combustion state is promptly improved to a good combustion state. Nevertheless, when the air-fuel ratio is changed to the rich side continuously for the same cylinder a predetermined number of times, the failure determination means determines that a failure has occurred in the fuel supply system or the ignition system. The reason why the poor combustion state continues even though the air-fuel ratio is changed to the fuel rich side is that the possibility of failure of the fuel supply system or the ignition system is extremely high.

Preferably, when the combustion state determining means determines that the number of times the fluctuation amount of the rotation information exceeds the threshold value within a predetermined period is equal to or greater than a second predetermined number and less than the first predetermined number, the air-fuel ratio The changing means maintains the air-fuel ratio of the air-fuel mixture supplied to the cylinder according to the determination. As a result, if the engine operation at the ultra-lean air-fuel ratio, that is, the stable combustion limit state has been achieved, such a combustion state is maintained.

More preferably, the control content of the engine is changed by the control change means in accordance with the failure determination. For example, the supply of fuel to the cylinder determined to have failed is stopped, or the air-fuel ratio of the air-fuel mixture supplied to the other cylinders is changed from the lean air-fuel ratio to the stoichiometric air-fuel ratio or an air-fuel ratio near the stoichiometric air-fuel ratio. . As a result, the adverse effect on the engine operation due to the failure of the fuel supply system or the ignition system is reduced. Also,
The failure determination result is stored in a nonvolatile manner, thereby facilitating the investigation of the cause of the failure.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1, reference numeral 1 denotes an internal combustion engine for a vehicle, for example, an in-line four-cylinder gasoline engine.
In this engine, a combustion chamber, an intake system, an ignition system, and the like are designed for lean burn. An air cleaner 5, an air flow sensor 6, a throttle valve 7, an ISC (idle speed) is provided to an intake port 2 of the engine 1 through an intake manifold 4 in which a fuel injection valve 3 constituting a main part of a fuel supply system is attached to each cylinder. Control) valve 8
And the like are connected. The exhaust port 10 is connected via an exhaust manifold 11 to an exhaust pipe 14 having a linear air-fuel ratio sensor 12, a three-way catalyst 13, and a muffler (not shown).

The engine 1 has an ignition plug 16 disposed in a combustion chamber 15 and a crank angle sensor 18 for detecting rotation of a rotor plate 17 to which a crankshaft 25 is directly attached. The crank angle sensor 18 functions as rotation information detecting means for detecting the rotation angular acceleration of the crankshaft 25 as rotation information of the engine 1. For example, a light emitting unit and a light receiving unit that face each other with the rotor plate 17 interposed therebetween. And As shown in FIG. 2, two vanes 17 a and 17 b having an angular width of 70 degrees are formed on the rotor plate 17 at intervals of 180 degrees.

The vanes 17 of the rotor plate 17
a or 17b is facing the crank angle sensor 18, that is, the rotational position of the crankshaft 25 is 110 degrees (BTD) including the top dead center (TDC) of each cylinder.
(C5 degrees to ATDC 105 degrees) during the first crank angle section α, the output of the crank angle sensor 18 is turned off, and one of the vanes is turned off by the crank angle sensor 1.
8, the rotation position of the crankshaft 25 is 70 degrees (ATD) following the first crank angle section α.
The output of the crank angle sensor 18 is turned on during the second crank angle section β of C105 degrees to ATDC 175 degrees (see FIG. 3).

In FIG. 1, reference numeral 19 denotes a throttle sensor for detecting the 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 Pa. And 22 represent an intake air temperature sensor for detecting the intake air temperature Ta. An ECU (Electronic Control Unit) 23, which includes an input / output device (not shown), a storage device containing a large number of control programs, a central processing unit, a timer counter, and the like, and performs overall control of the engine 1 is installed in the vehicle interior. Have been. The detection information from the various sensors described above is input to the input side of the ECU 23, and the ECU 23 calculates the optimum values such as the combustion injection amount and the ignition timing from the detection information, and obtains the fuel injection valve 3, the ignition plug 16 and the like. Drive.

In FIG. 1, reference numeral 24 denotes an ignition unit which outputs a high voltage to the ignition plug 16 in response to a command from the ECU 23.
Together, they constitute an ignition system. In addition, the ECU 23 includes:
The cylinder identification sensor 26 and the fail indication lamp 27 are connected. The cylinder identification sensor 26 identifies one of the four cylinders of the engine 1 in, for example, a combustion stroke, and is disposed facing a camshaft (not shown).
While the crankshaft 25 makes two rotations and the camshaft makes one rotation, a pulse output is generated each time the camshaft takes a specific rotation position corresponding to one cylinder. The fail indicator lamp 27 is for notifying a driver of the occurrence of a failure in the fuel supply system or the ignition system of the engine 1 when the failure is determined by the ECU 23 as described later. It is arranged on the instrument panel.

As will be apparent from the operation description below,
The ECU 23 determines a combustion state of each cylinder of the engine 1 based on a fluctuation amount of the rotation information obtained from the output of the crank angle sensor as the rotation information. Air-fuel ratio changing means for changing the engine, failure determining means for determining a failure of the fuel supply system or the ignition system of the engine 1, and control changing means for changing the control content of the engine 1 according to the failure determination And cooperates with the crank angle sensor 18 and the like as rotation information detecting means to constitute a lean burn control and failure determination device.

Hereinafter, the operation of the lean burn control and failure determination device having the above-described configuration will be described. When the driver turns on the ignition key and engine 1 starts, the ECU
23 starts the fuel injection control subroutine shown in FIG. In this subroutine, the ECU 23 reads various sensor outputs as engine operation information and stores them in a memory (step S1), and the air flow sensor output, that is, the intake air amount A per intake stroke calculated from the intake air amount and the engine speed Ne. / N is atmospheric pressure Pa, intake air temperature T
The volume efficiency Ev is obtained by correcting according to a and the like. Next, the ECU 23 determines whether or not the engine 1 is operating in the feedback control range based on the throttle opening θTH, the rate of time change of the throttle opening, the volumetric efficiency Ev, the elapsed time after starting the engine, the cooling water temperature TW, and the like. Is determined (step S2).

If the determination result in step S2 is affirmative, the ECU 23 determines the volumetric efficiency Ev and the engine speed Ne.
Based on the above, it is further determined whether or not the engine 1 is operating in a predetermined lean burn control region corresponding to an idle operation region, a constant speed operation region, or the like where the required torque is small (step S3). If the determination result in step S3 is affirmative, the ECU 23 sets the target air-fuel ratio OAF based on the volume efficiency Ev and the engine speed Ne with reference to the lean air-fuel ratio map shown in FIG. 8 ( Step S4), a lean burn control and a failure determination subroutine described later are executed (step S5).

On the other hand, if it is determined in step S3 that the engine 1 is not operating in the lean burn control range, the target is set in accordance with the stoichiometric / rich air-fuel ratio map shown in FIG. 9 based on the volume efficiency Ev and the engine speed Ne. Air-fuel ratio O
AF is set (step S6), and the valve opening time TINJ of the fuel injection valve 3, that is, the fuel injection amount is feedback-controlled so that the actual air-fuel ratio represented by the output of the air-fuel ratio sensor 12 becomes the target air-fuel ratio (step S6). S7).

If it is determined in step S2 that the engine 1 is not operating in the feedback control range, the target air-fuel ratio O is determined based on the stoichiometric / rich air-fuel ratio map.
AF is set (step S8), and the target air-fuel ratio OA
The basic injection amount TINJB calculated from F and the intake air amount A / N is subjected to correction such as increase during acceleration and increase during cold operation (step S9), and the fuel injection valve 3 is opened with the corrected injection amount as a target value. The valve time is controlled by open loop.

The above-described lean combustion control and failure determination subroutine (step S5 in FIG. 4) is executed each time a crank interrupt signal is generated. Referring to FIG. 5 to FIG. 7, in this subroutine, the ECU 23 controls the current cycle based on the output from the cylinder identification sensor 26.
The cylinder to be determined is identified (step S20).
Next, the ECU 23 determines the m-th one identified in step S20.
It is determined whether or not the m-th cylinder fail flag indicating the occurrence of a failure in the fuel injection valve or the ignition system for the number-th cylinder (m = 1, 2, 3, or 4) is set (step S).
21).

Normally, since the fuel injection valve and the ignition system have not failed, the result of the determination in step S21 is negative. In this case, the ECU 23 determines whether or not the engine 1 is operating in the air-fuel ratio learning region shown by cross-hatching the lean air-fuel ratio map in FIG.
It is further determined whether the volumetric efficiency Ev is in the range from EvA to EvB and the engine speed Ne is in the range from NeA to NeB (step S22).

If the result of this determination is negative, the ECU 23
Indicates whether or not the engine 1 is operated within the air-fuel ratio correction region indicated by hatching in FIG. 8, that is, the volume efficiency Ev is within the range from EvC to EvD, and the engine speed Ne is NeC. Then, it is further determined whether or not it is in the range from to NeD (step S34). As shown in FIG. 8, the correction area is set to include the learning area. This is because there is no risk of misfiring in a region outside the correction region, and no learning correction is required.

If it is determined in step S34 that the engine 1 is not operating within the correction range, the ECU 1
23 sets the target air-fuel ratio basic value OAFB retrieved from the lean air-fuel ratio map as the target air-fuel ratio OAF (step S36), and calculates the actual air-fuel ratio RAF from the output signal of the linear air-fuel ratio sensor 12 (step S41). Next, E
The CU 23 calculates a deviation ΔAF between the target air-fuel ratio OAF and the actual air-fuel ratio RAF (Step S42), and calculates the deviation ΔAF.
From the feedback correction coefficient KFB (step S
43) Further, the set air-fuel ratio SAF is calculated according to the formula SAF = OAF. (1 + KFB) (step S44).

Next, the ECU 23 calculates the equation TB = KINJ · Ev
The basic injection time TB of the fuel injection valve 3 is calculated according to 14.7 / SAF (step S45). In the equation, the symbol KI
NJ and Ev represent the fuel injector gain and volumetric efficiency, respectively, and the numerical value 14.7 is the stoichiometric air-fuel ratio (stoichio). Further, the valve opening time TINJ of the fuel injection valve 3 is calculated according to the equation TINJ = KDT · TB + TD (step S4).
6). In the equation, the symbol KDT represents the cooling water temperature Tw and the atmospheric pressure P.
a, the air-fuel ratio correction coefficient set according to the intake air temperature Ta, etc., and the symbol TD represents the invalid injection time. Next, the fuel injection valve 3 is driven to open for the valve opening time TINJ (step S47), and the processing after step S1 of the fuel injection control subroutine shown in FIG. 4 is executed again. Then, as long as it is determined in step S3 of the subroutine that the engine is operating in the lean burn control range, the above-described lean burn control and failure determination subroutine is continuously executed.

If the engine operation in the learning area is started during execution of this subroutine and the result of the determination in step S22 becomes affirmative, the ECU 23 sets the initial value TCDX (for example, 256) at the start of this subroutine. “1” is subtracted from the current value TCD of the count timer (step S23), and then the equation Vmn = (β / α−Tβ / T
According to α) · K, the instantaneous rotation fluctuation value Vmn in the n-th combustion stroke of the m-th cylinder is calculated and stored in the memory (step S24).

In the above equation, the symbols α and β are
The first crank angle section in which the output of the crank angle sensor 18 is turned off and the second crank angle section in which the output of the sensor is turned on, respectively, are represented by Tα and Tβ. , Β, respectively. The symbol K (> 0) represents a correction coefficient obtained from a map set in advance using the volumetric efficiency Ev and the engine speed Ne as parameters.

The first crank angle section α corresponds to a crankshaft rotation angle area of 110 ° including the compression top dead center, that is, the first half of the combustion stroke. In this section, combustion is still insufficient and the crankshaft 25 The rotation speed becomes relatively slow. On the other hand, the second crank angle section β corresponds to a crankshaft rotation angle area of 70 ° following the first crank angle section α, that is, the latter half of the combustion stroke. Normally, combustion in this section is completely performed, and The shaft rotation speed becomes relatively high. However, when a misfire (more generally, abnormal combustion) occurs, the negative pressure in the combustion chamber increases as the piston descends, so that the rotation speed of the crankshaft 25 in the second crank angle section β gradually decreases. Become.

Therefore, if combustion is normal, β / α> T
When the relationship β / Tα is established and the instantaneous rotational fluctuation value Vmn becomes a positive value, if a misfire occurs, the relationship β / α <Tβ / Tα is established and the instantaneous rotational fluctuation value Vmn becomes a negative value. Become. In the next step S25, the ECU 23 performs a low-pass filter process on the instantaneous rotational fluctuation value Vmn calculated in step S23 to obtain an average value Emn of the instantaneous rotational fluctuation value.
Store in memory. For example, the following equation is used for the low-pass filter processing.

Emn = KF · Em, n-1 + (1−KF) · Vmn Here, the symbol Em, n-1 is the instant of rotation fluctuation up to the (n-1) th combustion stroke of the m-th cylinder. Represents the average of the values, K
F represents a filter coefficient. The filter coefficient KF is set to, for example, a value of 0.95. Next, the ECU 23 calculates the cylinder-by-cylinder rotation fluctuation index ΔVmn according to the following equation in order to eliminate the fluctuation of the rotation fluctuation instantaneous value between cylinders and between cycles.

ΔVmn = (Vmn−Emn) − (Vm−1, n−Em−1, n) Here, the symbol Vm−1, n denotes the (n) th combustion stroke during the previous cycle execution. m-1) represents the instantaneous rotational fluctuation value of the cylinder # 1, and Em-1, n represents the average value of the rotational fluctuation instantaneous values of the (m-1) th cylinder up to the n-th combustion stroke. In step S26, the ECU 23 determines in step S2
The cylinder-by-cylinder rotation fluctuation index ΔV for the m-th cylinder calculated in 5
It is determined whether or not mn is smaller than a predetermined threshold value ΔVx set sufficiently smaller than a value representing a rotation fluctuation accompanying normal combustion.

If this determination is negative, that is, if it is determined that combustion in the m-th cylinder is normally performed, the ECU 23
Determines whether the current value TCD of the down count timer is "0", that is, after the engine starts in the learning region, the control cycle determines whether the initial value TCD of the down count timer
It is further determined whether or not the process has been executed the same number of times as CDX (step S29). Immediately after the start of the engine operation in the learning area, the determination result is negative. In this case, in the above-described step S34, it is determined whether or not the engine is operating in the correction region. However, since the engine 1 is operating in the learning region, the determination result in step S34 is affirmative. Become.

Therefore, the ECU 23 searches the lean air-fuel ratio map for the target air-fuel ratio basic value OAFB.
The target air-fuel ratio OAF is calculated according to AF = OAFB · (1 + ΣKL / N) (step S35). In the equation, the symbol N represents the number of cylinders of the engine 1, and in this embodiment, N = 4. The symbol ΣKL represents the sum of the cylinder-by-cylinder fuel correction coefficients KLm for the four cylinders.

Further, the ECU 23 performs the above-described air-fuel ratio feedback control (steps S41 to S47) so that the target air-fuel ratio OAF calculated in step S35 is achieved.
Execute As described above, while the engine is operating in the learning region included in the lean burn control region,
The occurrence of misfire is determined in step S26, and the process proceeds to step S2.
If the determination result in step 6 is affirmative, the ECU 23 adds the value "1" to the stored value CMF of the misfire counter (step S27), and calculates the integrated value ΣΔVm of the cylinder-specific rotation fluctuation index in step S25 of the current cycle. The cylinder-by-cylinder rotation fluctuation index ΔVmn is added (step S28). Once the engine operation in the learning region is interrupted, the misfire counter value CMF, the cylinder-by-cylinder variation integrated value ΣΔVm, and the countdown timer value TCD are stored in the memory, and after the engine operation in the learning region is restarted. These values are updated as needed.

Thereafter, when it is determined in step S29 that the control cycle in the learning region has been executed TCDX times since the start of the engine operation in the learning region, the process proceeds to step E29.
The CU 23 determines whether or not the stored value CMF of the misfire counter exceeds a second threshold CMFX2 (for example, "1") (Step S30). If the result of this determination is negative, that is, if it is determined in step S30 that no misfire has occurred during the execution of the control cycle of TCDX times in the learning region, the ECU 23 determines
It is determined that the air-fuel ratio of the air-fuel mixture supplied to the cylinder according to this determination is still on the rich side with respect to the stable combustion limit (air-fuel ratio 22 to 23), and the fuel correction coefficient for each cylinder according to the equation KLm = KLm-KD. KLm is updated to a value smaller than the current value by a reduction correction value KD (for example, 0.2%) and stored in the nonvolatile memory of the ECU 23 (step S31). This correction coefficient KLm is set, for example, to a value within the range of 0 to 10%.
Next, the ECU 23 determines the storage value N of the increase correction number counter.
F is reset to "0" (step S32). Further, as shown in FIG. 10, an initial value TCDX is set in a countdown timer TCD, and at the same time, a misfire count counter value CMF
And the cylinder-specific variation calculation value ΣΔVm is reset to “0” (step S33). Then, the engine operation in the correction region is determined in the next step S34, and the above-described air-fuel ratio feedback control is performed in and after step 35. As a result, when the target air-fuel ratio OAF is too rich during the operation of the engine in the correction region, the air-fuel ratio is gradually made leaner every TCDX cycle and approaches the stable combustion limit.

If the result of the determination in step S30 is affirmative, that is, if it is determined in step S30 that the stored value CMF of the misfire counter has exceeded the second threshold value CMFX2, the ECU 23 determines the stored value of the misfire counter. First threshold value CMFX1 (for example, 2) in which CMF is larger than second threshold value CMFX2
Is determined (step S37). Then, the result of this determination is negative, that is, T in the learning area.
If it is determined in steps S30 and S37 that a misfire has occurred, for example, once or twice during execution of the control cycle of CDX times, the ECU 23 determines that the air-fuel ratio related to the cylinder related to this determination is at the stable combustion limit. Then, the process of step S33 is executed. As a result, the current cylinder-specific fuel correction coefficient KLm is maintained, and the engine operation at the stable combustion limit is continued.

On the other hand, the result of determination in step S37 is affirmative, that is, the stored value CMF of the misfire counter exceeds the first threshold value CMFX1, and therefore, for example, three or more misfires have occurred during the execution of the control cycle TCDX times. To step S
When the determination at 37 is made, the ECU 23 determines that the air-fuel ratio of the cylinder related to this determination has already entered the lean side beyond the stable combustion limit, and enriches the air-fuel ratio. For this reason, the cylinder-by-cylinder increase correction value Kam corresponding to the cylinder-by-cylinder variation integrated value ΣVm is obtained from the map of FIG.
The cylinder-by-cylinder fuel correction coefficient KLm is updated according to KLm + Kam (step S38). Then, “1” is added to the storage value NF of the increase correction number counter (step S39),
It is determined whether or not the increase correction number NF exceeds a threshold value NFX (for example, 3) (step S40). As shown in FIG. 11, the cylinder-by-cylinder increase correction value Kam is a cylinder-by-cylinder variation integrated value ΣΔV
It is set to increase linearly as m increases. For this reason, when the vehicle enters the lean side beyond the stable combustion limit, the target air-fuel ratio OAF is enriched at once, and the misfire is usually immediately eliminated. Therefore, normally, the number of times of increase correction NF does not exceed, for example, three times, and the determination result in step S40 is negative. In this case, the processes after step S33 are sequentially executed.

As described above, when the engine 1 is operated in the correction region within the lean burn control region, the air-fuel ratio feedback control is performed so that the air-fuel ratio is always near the stable combustion limit, thereby improving the fuel efficiency. In addition, the amount of nitrogen oxide emission can be reduced. Moreover, by performing the processing in the lean burn control and the failure determination subroutine for each cylinder,
The influence of the variation in the combustion state between the individual cylinders in the vicinity of the stable combustion limit is eliminated.

However, a failure may occur in the fuel supply system and the ignition system of the engine 1 during the operation of the engine. For example, clogging of the fuel injection valve 3 or ignition plug 1
6 or the ignition unit 24 may be damaged. If the fuel supply amount is reduced due to the clogging of the fuel injection valve 3 or if a combustion failure state occurs due to poor ignition caused by a failure in the ignition systems 16 and 24, the increase correction is performed in step S35 of the lean burn control and failure determination subroutine. Even if the air-fuel ratio feedback control is performed in steps S41 to S47 so as to reach the target air-fuel ratio OAF, the target air-fuel ratio OA
F cannot be achieved, resulting in poor combustion. In particular, when such a combustion failure occurs in the lean air-fuel ratio region or the ultra-lean air-fuel ratio (stable combustion limit) region, the operation fee is lower than when a similar failure occurs during engine operation in the stoichiometric air-fuel ratio region. The ring is severely damaged.

Therefore, in the present embodiment, when a combustion failure occurs due to a failure in the fuel supply system or the ignition system, this is detected quickly and accurately and notified to the driver. As described above, in the present embodiment, during engine operation in the learning region within the lean burn control region, the cylinder-specific fuel correction coefficient KLm and, consequently, the air-fuel ratio are increased or decreased in accordance with the quality of the combustion state in each cylinder to thereby achieve a stable combustion limit. While maintaining the state, if it enters the lean side beyond the stable combustion limit, the air-fuel ratio is enriched and the poor combustion is immediately eliminated, so
Normally, the increase correction step S38 is not continuously executed for the same cylinder over the number of times exceeding the threshold value NFX. Therefore, when the number of times of increase correction NF exceeds the threshold value NFX, it is highly probable that a failure has occurred in the fuel supply system or the ignition system. Is determined to have occurred.

That is, in step S40 of the lean burn control and failure determination subroutine, if the number of increase corrections NF exceeds a threshold value NFX (for example, three times), the ECU 23 supplies fuel to the cylinder (mth cylinder) related to this determination. When it is determined that a failure has occurred in the system or the ignition system, the m-th cylinder fail flag is set (step S48), and the driving of the fuel injection valve 3 of the m-th cylinder is stopped (step S49). As a result, the supply of fuel to the cylinders that have suffered combustion failure due to the failure of the fuel supply system or the ignition system is stopped, and the exhaust gas characteristics and the exhaust gas characteristics that may occur when the fuel is continuously supplied to the cylinders in which combustion has not been performed normally. Fuel efficiency is prevented from deteriorating. Further, in the next step S50, the ECU 23 operates the failure indication lamp 2 provided on the instrument panel.
7 is turned on to notify the driver of the occurrence of the failure, thereby urging the driver to repair the failed part.

When the lean burn control and the failure determination subroutine are executed again in the next and subsequent control cycles, it is determined in step S21 that the mth cylinder failure flag is set. In this case, the subroutine program immediately proceeds to step S49, and the driving of the fuel injection valve 3 is stopped. The fail flag is
Since it is stored in the nonvolatile memory of the ECU 23 in a nonvolatile manner,
As long as the failure of the fuel supply system or ignition system is neglected,
When the lean burn control and the failure determination subroutine are executed, the failure display lamp 27 is turned on to notify the occurrence of a failure.

The present invention is not limited to the above embodiment but can be variously modified. For example, in the embodiment, the case where the present invention is applied to an in-line four-cylinder engine has been described. However, the present invention is also applicable to other types of engines such as a V-type six-cylinder engine. Further, in the embodiment, the drive of the fuel injection valve 3 of this cylinder is simply stopped when a failure occurs in the fuel supply system or the ignition system related to one cylinder. However, the drive of the fuel injection valve 3 is stopped and other operations are performed. The target air-fuel ratio related to the cylinder may be set to, for example, a stoichiometric air-fuel ratio or an air-fuel ratio near the stoichiometric air-fuel ratio.

Further, in the embodiment, when a failure occurs in the fuel supply system or the ignition system, the failure indication lamp is turned on to notify the driver of the occurrence of the failure. However, the failure occurrence is notified by means other than the lamp lighting, for example, a buzzer. Alternatively, the occurrence of a failure need not be notified. This is because even when the driver is not notified of the occurrence of the failure, the failure flag is stored in a nonvolatile manner, so that the failure occurrence part can be specified by the failure diagnosis device usually provided in the vehicle.
Instead of setting the fail flag, a coded specific pattern signal indicating a failure of the fuel supply system or the ignition system may be provided to the failure diagnosis device.

Further, values such as various threshold values and initial values in the embodiment are merely examples, and these values can be changed as appropriate.

[0054]

As described above, the lean burn control and failure determination device for an internal combustion engine according to the first aspect of the present invention includes a rotation information detection unit for detecting rotation information of an internal combustion engine, and a rotation information detection unit. Combustion state determining means for determining the fluctuation amount of the rotation information for each cylinder based on the rotation information detected by the method, comparing the fluctuation amount of the rotation information with a threshold value, and repeatedly determining whether the combustion state is good or bad in each cylinder. Every time it is determined by the combustion state determination means that the combustion state is good, the air-fuel ratio of the air-fuel mixture supplied to the cylinder according to this determination is changed to the fuel lean side, while the combustion state is poor. The air-fuel ratio changing means for changing the air-fuel ratio to the fuel-rich side each time it is determined, and the air-fuel ratio changing to the fuel-rich side by the air-fuel ratio changing means are continuously performed a predetermined number of times for the same cylinder. When Since a failure determination unit for determining that a failure has occurred in the fuel supply system or the ignition system related to the cylinder is provided, the engine can be stably operated in the lean air-fuel ratio region, and a special failure determination device is provided. Without using it, it is possible to reliably determine the failure of the fuel supply system and the ignition system of the engine. It is also possible to notify the driver of the occurrence of a failure at the time of failure determination to prompt the driver for repair.

According to the second aspect of the present invention, the rotation information detecting means detects the rotation angular acceleration of the crankshaft of the internal combustion engine as the rotation information. Combustion control and failure determination can be performed properly. According to the third aspect of the present invention, the present apparatus further includes control change means for changing the control content of the internal combustion engine according to the failure determination by the failure determination means. Can be eased.

[0056]

[0057]

[0058]

[0059]

[0060]

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an engine equipped with a lean burn control and failure determination device according to one embodiment of the present invention.

FIG. 2 is a schematic perspective view showing the crank angle sensor shown in FIG. 1 together with its peripheral elements.

FIG. 3 is a graph showing a relationship between a crank angle and an output of a crank angle sensor.

FIG. 4 is a flowchart showing a fuel injection control subroutine executed by the electronic control unit shown in FIG. 1;

FIG. 5 is a flowchart showing a part of a lean burn control and a failure determination subroutine included in a fuel injection control subroutine.

FIG. 6 shows a lean burn control and a failure determination subroutine.
6 is a flowchart showing a part following FIG. 5;

FIG. 7 shows a lean burn control and a failure determination subroutine.
FIG. 7 is a flowchart showing a part following FIG. 5 and FIG. 6.

FIG. 8 is a graph showing a lean air-fuel ratio map used in a fuel injection control subroutine together with an air-fuel ratio learning and correction area.

FIG. 9 is a stoichiometric / rich air-fuel ratio map used in a fuel injection control subroutine.

FIG. 10 is a graph illustrating changes in various control parameters accompanying engine rotation fluctuation during lean burn control.

FIG. 11 is a map of a variation integrated value ΔVm and an increase correction value Kam used in the lean burn control and the failure determination subroutine.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Internal combustion engine 3 Fuel injection valve 12 Linear air-fuel ratio sensor 16 Spark plug 17 Rotor plate 18 Crank angle sensor 23 Electronic control unit 24 Ignition unit 25 Crankshaft 26 Cylinder identification sensor 27 Fail indicator lamp

──────────────────────────────────────────────────の Continuation of the front page (51) Int.Cl. ⁶ Identification code FI F02D 45/00 362 F02D 45/00 362J F02P 5/15 F02P 5/15 L (56) References JP-A-5-248281 (JP) JP-A-6-307285 (JP, A) JP-A-1-237339 (JP, A) JP-A-1-290946 (JP, A) JP-A-6-101564 (JP, A) JP-A-3-225050 (JP, A) JP-A-6-17690 (JP, A) JP-A-5-231210 (JP, A) JP-A-4-232363 (JP, A) A) Fully open sho 63-202751 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) F02D 41/22 F02D 41/02 F02D 41/04 F02D 45/00 F02P 5/15

Claims (3)

(57) [Claims] A rotation information detection unit for detecting rotation information of an internal combustion engine; and a variation amount of the rotation information for each cylinder based on the rotation information detected by the rotation information detection unit. A combustion state determination unit for repeatedly determining whether the combustion state is good or bad in each cylinder by comparing the amount of variation with a threshold value, and each time the combustion state determination unit determines that the combustion state is good, While the air-fuel ratio of the air-fuel mixture supplied to the cylinder according to this determination is changed to the fuel-lean side, the air-fuel ratio is changed to change the air-fuel ratio to the fuel-rich side each time the combustion state is determined to be poor. Means, when the air-fuel ratio change to the fuel-rich side by the air-fuel ratio changing means is continuously performed a predetermined number of times for the same cylinder, when a failure has occurred in the fuel supply system or the ignition system related to this cylinder. judge Characterized in that it comprises a fit of failure determining means, lean-burn control and failure determination device for an internal combustion engine. 2. The apparatus according to claim 1, wherein the rotation information detection means detects a rotation angular acceleration of a crankshaft of the internal combustion engine as the rotation information. 3. The internal combustion engine according to claim 1, further comprising control change means for changing the control content of the internal combustion engine in accordance with the failure determination by the failure determination means. Judgment device.