JP4417000B2 - Abnormality diagnosis device for internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an abnormality diagnosis apparatus for an internal combustion engine that performs a predetermined abnormality diagnosis based on an output of a sensor that detects information related to an operating state of the internal combustion engine.
[0002]
[Prior art]
In recent years, electronically controlled internal combustion engines are equipped with various sensors that detect various information related to operating conditions (for example, intake air amount, intake pipe pressure, rotational speed, air-fuel ratio, etc.), and based on the outputs of these various sensors. Thus, the fuel injection amount (air-fuel ratio), ignition timing, and the like are controlled, and various abnormality diagnoses are performed using the outputs of these various sensors. For example, as described in Patent Document 1 (Japanese Patent Application Laid-Open No. 9-166669), the presence or absence of abnormality of the air-fuel ratio sensor is determined based on the output of the air-fuel ratio sensor that detects the air-fuel ratio of the exhaust gas of the internal combustion engine. There is something to be diagnosed.
[0003]
[Patent Document 1]
Japanese Patent Laid-Open No. 9-166669 (second page, etc.)
[0004]
[Problems to be solved by the invention]
However, in an internal combustion engine having a plurality of cylinders, the operating state of each cylinder may vary due to individual differences (parts tolerance, assembly tolerance, etc.), aging, etc. of each cylinder. For this reason, when various abnormality diagnosis is performed based on the output of a sensor that detects information related to the operating state of the internal combustion engine (for example, intake air amount, intake pipe pressure, rotational speed, air-fuel ratio, etc.), the operating state between the cylinders If the variation of the sensor is large, the fluctuation in the sensor output in the cycle becomes large due to the influence, and it may be erroneously diagnosed as abnormal even though the abnormality diagnosis target is normal.
[0005]
The present invention has been made in consideration of such circumstances. Therefore, the object of the present invention is to prevent misdiagnosis of sensor output disturbance caused by variation between cylinders as an abnormality to be diagnosed. An object of the present invention is to provide a control device for an internal combustion engine capable of improving diagnosis accuracy.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, an abnormality diagnosis apparatus for an internal combustion engine according to claim 1 of the present invention performs a predetermined abnormality diagnosis based on an output of a sensor that detects information related to an operating state of an internal combustion engine having a plurality of cylinders. An abnormality diagnosis apparatus for an internal combustion engine having an abnormality diagnosis means, wherein an inter-cylinder variation detection means for obtaining a variation value between cylinders representing a variation in operating state between cylinders of the internal combustion engine, and the internal combustion engine based on the variation value between cylinders Of operating conditions among cylinders The operating state between the cylinders of the internal combustion engine is reduced so that the When the inter-cylinder variation correction unit for correcting the inter-cylinder variation correction unit and the inter-cylinder variation correction unit are not completed, the abnormality diagnosis unit prohibits the abnormality diagnosis or relaxes the abnormality determination criterion, and the cylinder The apparatus is provided with a misdiagnosis prevention means for continuing prohibition of abnormality diagnosis or relaxation of abnormality determination criteria until a predetermined period elapses after the completion of correction of variation in intervals.
[0007]
As in the present invention, the variation in the operating state between the cylinders of the internal combustion engine based on the variation value between the cylinders. The operating state between the cylinders of the internal combustion engine is reduced so that the In the case of a system provided with a correction means for correcting variation among cylinders, since the variation between cylinders is still large until the correction for variations between cylinders is completed, the disturbance of the sensor output may exceed the normal abnormality determination level. is there.
[0008]
Therefore, In the present invention When the inter-cylinder variation correction has not been completed, prohibit abnormality diagnosis or relax abnormality criterion Have . In this way, it is possible to prevent misdiagnosis of sensor output disturbances as abnormalities to be diagnosed when the variation between cylinders is still large before completion of variation correction between cylinders, and improve abnormality diagnosis accuracy. Can do.
[0009]
In addition, since it may take some time for the variation between cylinders to become sufficiently small after executing the variation correction between cylinders, In the present invention The abnormality diagnosis is prohibited or the abnormality determination criteria are relaxed until a predetermined period has elapsed even after the correction of variation among cylinders is completed. Have . In this way, immediately after completion of the inter-cylinder variation correction, the abnormality diagnosis is prohibited or the abnormality determination criteria are relaxed even during a period when the variation between the cylinders may not be sufficiently small, so that the erroneous diagnosis can be performed more reliably. Can be prevented.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
<< Embodiment (1) >>
Hereinafter, an embodiment (1) of the present invention will be described with reference to FIGS. First, a schematic configuration of the entire engine control system will be described with reference to FIG. For example, a four-cylinder engine 11 that is an internal combustion engine has four cylinders, a first cylinder # 1 to a fourth cylinder # 4, and an air cleaner 13 is provided at the most upstream portion of the intake pipe 12 of the engine 11. An air flow meter 14 for detecting the intake air amount is provided on the downstream side of the air cleaner 13. On the downstream side of the air flow meter 14, a throttle valve 15 whose opening is adjusted by a DC motor or the like and a throttle opening sensor 16 for detecting the throttle opening are provided.
[0011]
A surge tank 17 is provided downstream of the throttle valve 15, and an intake pipe pressure sensor 18 that detects the intake pipe pressure is provided in the surge tank 17. The surge tank 17 is provided with an intake manifold 19 for introducing air into each cylinder of the engine 11, and a fuel injection valve 20 for injecting fuel is attached in the vicinity of the intake port of the intake manifold 19 of each cylinder. Yes. A spark plug 21 is attached to each cylinder of the engine 11 for each cylinder, and the air-fuel mixture in the cylinder is ignited by spark discharge of each spark plug 21.
[0012]
On the other hand, the exhaust pipe 22 of the engine 11 is provided with a catalyst 23 such as a three-way catalyst for purifying CO, HC, NOx and the like in the exhaust gas, and the exhaust gas air-fuel ratio or lean is provided upstream of the catalyst 23. / An exhaust gas sensor 24 (air-fuel ratio sensor, oxygen sensor, etc.) for detecting rich or the like is provided. Further, a water temperature sensor 25 that detects the coolant temperature and a crank angle sensor 26 that outputs a pulse signal each time the crankshaft of the engine 11 rotates by a certain crank angle (for example, 30 ° C. A) are attached to the cylinder block of the engine 11. It has been. Based on the output signal of the crank angle sensor 26, the crank angle and the engine speed are detected.
[0013]
Outputs of the various sensors described above are input to an engine control circuit (hereinafter referred to as “ECU”) 27. The ECU 27 is mainly composed of a microcomputer, and executes various engine control programs stored in a built-in ROM (storage medium) to thereby determine the fuel injection amount of the fuel injection valve 20 according to the engine operating state. The ignition timing of the spark plug 21 is controlled.
[0014]
At that time, the ECU 27 executes an air-fuel ratio feedback control program (not shown) to calculate the air-fuel ratio correction coefficient FAF so that the air-fuel ratio λs of the exhaust gas detected by the exhaust gas sensor 24 matches the target air-fuel ratio λtg, The fuel injection amount is calculated using the air-fuel ratio correction coefficient FAF.
[0015]
Further, the ECU 27 executes an exhaust gas sensor abnormality diagnosis program shown in FIG. 2 to be described later, so that when the target air-fuel ratio λtg changes, the change amount Δλtg of the target air-fuel ratio λtg and the change amount ΔFAF of the air-fuel ratio correction coefficient FAF Whether or not the exhaust gas sensor 24 is abnormal (failure, deterioration, etc.) is diagnosed based on whether or not the ratio (ΔFAF / Δλtg) is within a predetermined range (KCGL to KCGH).
[0016]
However, if the variation in the operation state between the cylinders is large, the fluctuation in the cycle of the output of the exhaust gas sensor 24 is affected and the abnormality diagnosis parameter (for example, ΔFAF / Δλtg) becomes an abnormality determination value (for example, a lower limit value of a predetermined range). KCGL or the upper limit value KCGH) may be exceeded, and the exhaust gas sensor 24 may be normal but may be erroneously diagnosed as being abnormal.
[0017]
Therefore, the ECU 27 executes an inter-cylinder variation detection program shown in FIG. 3 and FIG. 4 to be described later, thereby calculating an inter-cylinder variation value DEV that represents the variation in the operating state between the cylinders of the engine 11. By executing the inter-cylinder variation correction program shown in FIG. 4, the variation in the operating state between the cylinders of the engine 11 is corrected based on the inter-cylinder variation value DEV.
[0018]
Then, by executing a misdiagnosis prevention program shown in FIG. 7 to be described later, when the inter-cylinder variation value DEV exceeds a predetermined range, or when the inter-cylinder variation correction is not completed, the exhaust gas sensor 24 The abnormality diagnosis is prohibited to prevent the output gas sensor 24 from being disturbed due to the variation among cylinders from being erroneously diagnosed as being abnormal in the exhaust gas sensor 24. Hereinafter, processing contents of each program executed by the ECU 27 will be described.
[0019]
[Exhaust gas sensor abnormality diagnosis program]
The exhaust gas sensor abnormality diagnosis program shown in FIG. 2 is executed at each fuel injection timing, for example, and serves as abnormality diagnosis means in the claims. When this program is started, first, in step 101, whether or not the absolute value of the difference between the current target air-fuel ratio λtg and the previous target air-fuel ratio λtg (i-1) is equal to or greater than a predetermined determination value Kλtg. Determine. If | λtg−λtg (i−1) | <Kλtg, it is determined that the target air-fuel ratio λtg has not changed, and the routine proceeds to step 105 where the target air-fuel ratio change flag X changes the target air-fuel ratio λtg. It is determined whether or not it is set to “1” meaning already detected. If the target air-fuel ratio change flag X is not set to “1”, this program is terminated without performing the subsequent processing.
[0020]
Thereafter, when | λtg−λtg (i−1) | ≧ Kλtg, it is determined that the target air-fuel ratio λtg has changed, and the routine proceeds to step 102 where the target air-fuel ratio change flag X is set to “1”. Thereafter, the process proceeds to step 103, where the target air-fuel ratio λtg (i-1) one time before is subtracted from the current target air-fuel ratio λtg to calculate the change amount Δλtg of the target air-fuel ratio λtg.
Δλtg = λtg−λtg (i-1)
[0021]
Thereafter, the routine proceeds to step 104, where the air-fuel ratio correction coefficient FAF at that time is stored in the memory (not shown) of the ECU 27 as the air-fuel ratio correction coefficient FAFBF before the change, and this program ends.
[0022]
Then, every time this program is started after the change of the target air-fuel ratio λtg, it is determined as “No” in step 101 and proceeds to step 105, and if the target air-fuel ratio change flag X is set to “1”. In step 106, the difference between the current target air-fuel ratio λtg and the previous target air-fuel ratio λtg (i-1) is added to the previous Δλtg to update the stored value of Δλtg.
Δλtg = Δλtg + {λtg−λtg (i−1)}
[0023]
Thereafter, the routine proceeds to step 107, where it is determined whether or not the absolute value of the difference between the current air-fuel ratio correction coefficient FAF and the previous air-fuel ratio correction coefficient FAF (i-1) has become equal to or less than a predetermined value KFAF. When | FAF−FAF (i−1) | ≦ KFAF, that is, when the air-fuel ratio correction coefficient FAF has converged to a predetermined value, the routine proceeds to step 108 where the current air-fuel ratio correction coefficient FAF is calculated from the current air-fuel ratio correction coefficient FAF. The change amount ΔFAF of the air-fuel ratio correction coefficient FAF is calculated by subtracting the air-fuel ratio correction coefficient FAFBF before change stored in step 104.
ΔFAF = FAF-FAFBF
[0024]
Thereafter, the process proceeds to step 109, the target air-fuel ratio change flag X is reset to “0”, and then the process proceeds to step 110, where the ratio between the absolute value of ΔFAF and the absolute value of Δλtg is within a predetermined range (KCGL ≦ | ΔFAF | / | Δλtg | ≦ KCGH) is determined (for example, KCGL = 0.9, KCGH = 1.1).
[0025]
As a result, when it is determined that the ratio between the absolute value of ΔFAF and the absolute value of Δλtg is within the predetermined range, the process proceeds to step 111, where it is determined that the exhaust gas sensor 24 is not abnormal (normal), and this program Exit.
[0026]
On the other hand, if it is determined that the ratio between the absolute value of ΔFAF and the absolute value of Δλtg is out of the predetermined range, the routine proceeds to step 112, where it is determined that the exhaust gas sensor 24 is abnormal (failure, deterioration, etc.). A warning lamp (not shown) provided on the instrument panel of the seat is turned on, or a warning is displayed on a warning display (not shown) to warn the driver, and the abnormality information (abnormal code) is sent to the ECU 27. Is stored in a backup RAM (not shown) and the program is terminated.
[0027]
[Cylinder variation detection program]
The inter-cylinder variation detection program shown in FIGS. 3 and 4 is executed, for example, in a predetermined cycle after an ignition switch (not shown) is turned on, and serves as the inter-cylinder variation detecting means in the claims.
[0028]
Here, as shown in FIG. 5, the waveform of the intake pipe pressure detected by the intake pipe pressure sensor 18 is a pulsation waveform reflecting the operation state (intake air amount, combustion state, air-fuel ratio, etc.) of each cylinder. Therefore, by calculating characteristic values such as the minimum value, maximum value, average value, amplitude value, area, and trajectory length of the intake pipe pressure detected by the intake pipe pressure sensor 18 for each crank angle range in which the influence of each cylinder appears. Since the characteristic value of the pulsation waveform reflecting the operating state of each cylinder can be calculated, the variation value between cylinders reflecting the variation of the operating state of each cylinder can be calculated using this characteristic value.
[0029]
In this program, since the inter-cylinder variation value is calculated by using the minimum value of the intake pipe pressure, as shown in FIG. ˜ It is set to include a region where the intake pipe pressure becomes a minimum value due to the influence of the fourth cylinder.
[0030]
When this program is started, first, in step 201, it is determined whether or not an execution condition for detecting variation among cylinders is satisfied, for example, whether or not it is in a steady state (not in a transient state). If it is determined that the execution condition for detecting variation among cylinders is not satisfied, the present program is terminated without performing the subsequent processing.
[0031]
On the other hand, if it is determined in step 201 that the condition for detecting the variation among cylinders is satisfied, the process proceeds to step 202 where the crank angle detected based on the output signal of the crank angle sensor 26 is the first. It is determined whether or not the crank angle is within a crank angle range (a crank angle range including a region where the intake pipe pressure has a minimum value due to the influence of the first cylinder # 1). As a result, if it is determined that it is within the first crank angle range, the routine proceeds to step 203, where the minimum value PMmin of the intake pipe pressure within the first crank angle range is set to the intake pipe pressure minimum of the first cylinder # 1. Calculated as the value PMmin (# 1).
[0032]
On the other hand, if it is determined in step 202 that the crank angle is not within the first crank angle range, the routine proceeds to step 204, where the crank angle is within the second crank angle range (due to the influence of the second cylinder # 2). It is determined whether or not the intake pipe pressure is within a crank angle range including a region where the intake pipe pressure becomes a minimum value. As a result, if it is determined that it is within the second crank angle range, the routine proceeds to step 205, where the minimum value PMmin of the intake pipe pressure within the second crank angle range is set to the minimum intake pipe pressure of the second cylinder # 2. Calculated as the value PMmin (# 2).
[0033]
If it is determined in step 204 that the crank angle is not within the second crank angle range, the routine proceeds to step 206, where the crank angle is in the third crank angle range (due to the influence of the third cylinder # 3). It is determined whether or not the intake pipe pressure is within a crank angle range including a region where the intake pipe pressure becomes a minimum value. As a result, if it is determined that it is within the third crank angle range, the routine proceeds to step 207, where the minimum value PMmin of the intake pipe pressure within the third crank angle range is set to the minimum intake pipe pressure of the third cylinder # 3. Calculated as the value PMmin (# 3).
[0034]
If it is determined in step 206 that the crank angle is not within the third crank angle range, the crank angle is within the fourth crank angle range (the intake pipe pressure is minimized due to the influence of the fourth cylinder # 4). And the routine proceeds to step 208, where the minimum value PMmin of the intake pipe pressure within the fourth crank angle range is set to the minimum value of the intake pipe pressure of the fourth cylinder # 4. Calculated as the value PMmin (# 4).
[0035]
Thereafter, the process proceeds to step 209 in FIG. 4 to calculate an average value AVEPMmin of the intake pipe pressure minimum values PMmin (# 1) to PMmin (# 4) of all cylinders.
AVEPMmin = {PMmin (# 1) + …… + PMmin (# 4)} / 4
[0036]
Thereafter, the process proceeds to step 210, and the inter-cylinder variation value DEV (#i) of each cylinder is calculated by the following equation using the intake pipe pressure minimum value PMmin (#i) and the average value AVEPMmin of each cylinder. Here, # i = # 1 to # 4.
DEV (#i) = PMmin (#i) -AVEPMmin
[0037]
Thereafter, the process proceeds to step 211, in which it is determined whether or not the inter-cylinder variation value DEV (#i) of each cylinder is within a predetermined range (K1 ≦ DEV (#i) ≦ K2). As a result, if it is determined that one of all the inter-cylinder variation values DEV (# 1) to DEV (# 4) is out of the predetermined range, the process proceeds to step 212 and the inter-cylinder variation flag XDEV is set. Set to “1”, which means that the variation between cylinders is large, and the program ends.
[0038]
On the other hand, if it is determined that all the inter-cylinder variation values DEV (# 1) to DEV (# 4) are within the predetermined range, the process proceeds to step 213, and the inter-cylinder variation flag XDEV is set so that the inter-cylinder variation is small. Is reset to “0”, meaning that this program is terminated.
[0039]
[Cylinder variation correction program]
The inter-cylinder variation correction program shown in FIG. 6 is executed at a predetermined cycle after the ignition switch is turned on, for example, and serves as inter-cylinder variation correction means in the claims. When this program is started, first, in step 301, the inter-cylinder variation value DEV (#i) of each cylinder is read, and then the process proceeds to step 302, where the inter-cylinder variation value DEV (#i) of each cylinder is used. Thus, the fuel injection time correction coefficient FTAU (#i) of each cylinder is calculated by the following equation.
FTAU (#i) = DEV (#i) +1
[0040]
Thereafter, the routine proceeds to step 303, where the average fuel injection time TAU of all cylinders before correction is multiplied by the fuel injection time correction coefficient FTAU (#i) of each cylinder, and the final fuel injection time TAU (#i) of each cylinder is obtained. Ask for.
TAU (#i) = TAU × FTAU (#i)
Through the above processing, the fuel injection amount of each cylinder is corrected according to the inter-cylinder variation value DEV (#i) of each cylinder, thereby reducing the air-fuel ratio variation between the cylinders.
[0041]
[Misdiagnostic prevention program]
The misdiagnosis prevention program shown in FIG. 7 is executed, for example, in a predetermined cycle after the ignition switch is turned on, and serves as a misdiagnosis prevention means in the claims. When this program is started, first, in step 401, it is determined whether or not (1) variation between cylinders is small (inter-cylinder variation flag XDEV = 0), and (2) variation correction between cylinders is completed. It is determined whether or not a predetermined period (predetermined time, predetermined crank angle, etc.) has elapsed.
[0042]
As a result, when it is determined that the cylinder-to-cylinder variation is large (inter-cylinder variation flag XDEV = 1), or when it is determined that the predetermined period has not elapsed since the completion of the cylinder-to-cylinder variation correction, Therefore, the output of the exhaust gas sensor 24 is disturbed and the abnormality diagnosis parameter (for example, ΔFAF / Δλtg) is determined to be out of the normal range (KCGL to KCGH). To do. This prevents the output disturbance of the exhaust gas sensor 24 caused by the variation between cylinders from being erroneously diagnosed as an abnormality of the exhaust gas sensor 24.
[0043]
On the other hand, if it is determined in step 401 that the inter-cylinder variation is small, or if it is determined that the predetermined period has elapsed since the correction of variation between cylinders is completed, the process proceeds to step 403 and the exhaust gas sensor 24 is processed. Allow diagnosis of abnormalities.
[0044]
In the present embodiment (1) described above, since the abnormality diagnosis of the exhaust gas sensor 24 is prohibited when the variation between cylinders is large, the disturbance in the output of the exhaust gas sensor 24 caused by the variation between cylinders is detected. Therefore, it is possible to prevent the abnormality diagnosis of the exhaust gas sensor 24 from being mistakenly diagnosed.
[0045]
Further, in the present embodiment (1), in consideration of the fact that it may take some time after the cylinder-to-cylinder variation correction is actually performed until the cylinder-to-cylinder variation is sufficiently reduced, Since the prohibition of abnormality diagnosis of the exhaust gas sensor 24 is continued until a predetermined period elapses even after the completion, the inter-cylinder variation may not be sufficiently small immediately after the completion of the inter-cylinder variation correction. However, abnormality diagnosis can be prohibited, and erroneous diagnosis can be prevented more reliably.
[0047]
<< Embodiment (2) >>
Next, Embodiment (2) of this invention is demonstrated using FIG. 8 thru | or FIG.
In the embodiment (1), the inter-cylinder variation value is calculated using the minimum value of the intake pipe pressure, but in the present embodiment (2), the inter-cylinder variation detection program shown in FIGS. 8 and 9 described later is executed. Thus, the inter-cylinder variation value is calculated using the maximum value of the intake pipe pressure.
[0048]
Further, in the embodiment (1), abnormality diagnosis of the exhaust gas sensor 24 is prohibited to prevent erroneous diagnosis, but in this embodiment (2), a misdiagnosis prevention program shown in FIG. 10 described later is executed. By doing so, the abnormality determination criteria of the exhaust gas sensor 24 are relaxed to prevent erroneous diagnosis.
[0049]
[Cylinder variation detection program]
Since the inter-cylinder variation detection program shown in FIGS. 8 and 9 calculates the inter-cylinder variation value using the maximum value of the intake pipe pressure, as shown in FIG. The crank angle range is set so as to include a region where the intake pipe pressure becomes a maximum value due to the influence of the first to fourth cylinders.
[0050]
In this program, if it is determined in step 501 that the condition for detecting the variation between cylinders is satisfied, the crank angle is within the first crank angle range (the influence of the first cylinder # 1 causes the intake pipe pressure to reach the maximum value). The maximum value PMmax of the intake pipe pressure within the first crank angle range is calculated as the intake pipe pressure maximum value PMmax (# 1) of the first cylinder # 1. (Steps 502 and 503).
[0051]
On the other hand, when the crank angle is within the second crank angle range (the crank angle range including the region where the intake pipe pressure becomes maximum due to the influence of the second cylinder # 2), the intake air within the second crank angle range The maximum value PMmax of the pipe pressure is calculated as the intake pipe pressure maximum value PMmax (# 2) of the second cylinder # 2 (steps 504 and 505).
[0052]
Further, when the crank angle is within the third crank angle range (a crank angle range including a region where the intake pipe pressure becomes a maximum value due to the influence of the third cylinder # 3), the intake air within the third crank angle range. The maximum value PMmax of the pipe pressure is calculated as the intake pipe pressure maximum value PMmax (# 3) of the third cylinder # 3 (steps 506 and 507).
[0053]
Further, when the crank angle is within the fourth crank angle range (the crank angle range including the region where the intake pipe pressure becomes maximum due to the influence of the fourth cylinder # 4), the intake air within the fourth crank angle range The maximum value PMmax of the pipe pressure is calculated as the intake pipe pressure maximum value PMmax (# 4) of the fourth cylinder # 4 (step 508).
[0054]
Thereafter, the process proceeds to step 509 in FIG. 9, and an average value AVEPMmax of the intake pipe pressure maximum values PMmax (# 1) to PMmax (# 4) of all cylinders is calculated.
AVEPMmax = {PMmax (# 1) + ...... + PMmax (# 4)} / 4
[0055]
Thereafter, the process proceeds to step 510, and the inter-cylinder variation value DEV (#i) of each cylinder is calculated by the following equation using the intake pipe pressure maximum value PMmax (#i) and the average value AVEPMmax of each cylinder.
DEV (#i) = PMmax (#i) -AVEPMmax
[0056]
Thereafter, the process proceeds to step 511, where it is determined whether or not the inter-cylinder variation value DEV (#i) of each cylinder is within a predetermined range (K1 to K2), and all the inter-cylinder variation values DEV (# 1) are determined. ) To DEV (# 4), if it is determined that the predetermined range is exceeded, the routine proceeds to step 512, where the inter-cylinder variation flag XDEV is set to "1" and all the inter-cylinder variation values are set. If it is determined that DEV (# 1) to DEV (# 4) are within the predetermined range, the process proceeds to step 513, and the inter-cylinder variation flag XDEV is reset to “0”.
[0057]
[Misdiagnostic prevention program]
In the misdiagnosis prevention program shown in FIG. 10, first, in step 601, it is determined whether or not (1) variation between cylinders is small (inter-cylinder variation flag XDEV = 0), and (2) variation correction between cylinders is performed. Determine if completed.
[0058]
As a result, when it is determined that the variation between the cylinders is large (inter-cylinder variation flag XDEV = 1), or when it is determined that the correction between the variations among the cylinders is not completed, the exhaust gas sensor 24 may It is determined that there is a possibility that the output is disturbed and the abnormality diagnosis parameter (for example, ΔFAF / Δλtg) may be out of the normal range (lower limit value KCGL to upper limit value KCGH). Value) is changed to the lower limit value (KCGL-α) for preventing misdiagnosis, and the upper limit value KCGH (abnormality judgment value) is changed to the upper limit value (KCGH + β) for preventing misdiagnosis to widen the range of the normal range. Relax the abnormality criteria. Thus, it is possible to prevent the output gas sensor 24 from being disturbed due to the variation between cylinders from being erroneously diagnosed as being abnormal in the exhaust gas sensor 24.
[0059]
On the other hand, if it is determined in step 601 that the variation between the cylinders is small, or if it is determined that the variation correction between the cylinders is completed, the process proceeds to step 603, where the lower limit value (abnormality determination value) of the normal range is reached. The upper limit value (abnormality determination value) is returned to the normal values KCGL and KCGH.
[0060]
In the embodiment (2) described above, when the variation between cylinders is large or when the variation correction between cylinders is not completed, the normal range is widened to relax the abnormality determination criteria. Therefore, it is possible to prevent the output disturbance of the exhaust gas sensor 24 from being erroneously diagnosed as an abnormality of the exhaust gas sensor 24, and to improve the abnormality diagnosis accuracy of the exhaust gas sensor 24.
[0061]
In this embodiment (2), the abnormality determination value (the lower limit value and the upper limit value of the normal range) is changed in order to relax the abnormality determination criteria, but the abnormality diagnosis parameter (for example, ΔFAF / Δλtg) is corrected. It is also possible to change other abnormality determination conditions such as correcting the output of the exhaust gas sensor 24.
[0062]
In the present embodiment (2), as in the above embodiment (1), the relaxation of the abnormality determination criteria may be continued until a predetermined period elapses after completion of the inter-cylinder variation correction.
[0063]
Further, in each of the above embodiments (1) and (2), the present invention is applied to the abnormality diagnosis of the exhaust gas sensor 24. However, the present invention is not limited to this, for example, catalyst deterioration using the output of the exhaust gas sensor 24. Diagnosis, abnormality diagnosis of the air flow meter 14 using the output of the air flow meter 14, abnormality diagnosis of the intake pipe pressure sensor 18 using the output of the intake pipe pressure sensor 18, the air flow meter 14, the intake pipe pressure sensor 18, and the exhaust gas sensor 24. The present invention can be applied to various abnormality diagnoses affected by variations among cylinders, such as abnormality diagnosis of a catalyst early warm-up system using at least one of these outputs and abnormality diagnosis of an air-fuel ratio control system.
[0064]
Further, in each of the above embodiments (1) and (2), the inter-cylinder variation value is calculated based on the maximum value or the minimum value for each predetermined period of the intake pipe pressure, but the calculation method of the inter-cylinder variation value is appropriately changed. For example, the inter-cylinder variation value may be calculated based on the average value, amplitude value, area, locus length, etc. of the intake pipe pressure for each predetermined period. Further, instead of the intake pipe pressure, the inter-cylinder variation value may be calculated based on the intake air amount, the in-cylinder pressure, the rotational speed, the ion current, the air-fuel ratio, and the like.
[0065]
In each of the above embodiments (1) and (2), the variation between cylinders is corrected by correcting the fuel injection amount for each cylinder. However, the correction method for the variation between cylinders may be changed as appropriate, for example, The ignition timing may be corrected for each cylinder, or the intake air amount may be corrected for each cylinder to correct the variation between cylinders.
[0066]
In addition, the application range of the present invention is not limited to a four-cylinder engine, and the present invention may be applied to a multi-cylinder engine having five or more cylinders or three or less cylinders.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of an entire engine control system according to an embodiment (1) of the present invention.
FIG. 2 is a flowchart showing a processing flow of an exhaust gas sensor abnormality diagnosis program according to the embodiment (1).
FIG. 3 is a flowchart (part 1) showing a flow of processing of a cylinder-to-cylinder variation detection program of the embodiment (1).
FIG. 4 is a flowchart (part 2) showing the flow of processing of the inter-cylinder variation detection program of the embodiment (1).
FIG. 5 is a time chart showing the behavior of intake pipe pressure.
FIG. 6 is a flowchart showing a flow of processing of the inter-cylinder variation correction program of the embodiment (1).
FIG. 7 is a flowchart showing a flow of processing of the misdiagnosis prevention program of the embodiment (1).
FIG. 8 is a flowchart (part 1) showing the flow of processing of a cylinder-to-cylinder variation detection program according to the embodiment (2).
FIG. 9 is a flowchart (part 2) showing the flow of processing of the inter-cylinder variation detection program of the embodiment (2).
FIG. 10 is a flowchart showing a flow of processing of a misdiagnosis prevention program according to the embodiment (2).
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 11 ... Engine (internal combustion engine), 12 ... Intake pipe, 14 ... Air flow meter, 15 ... Throttle valve, 18 ... Intake pipe pressure sensor, 20 ... Fuel injection valve, 21 ... Spark plug, 22 ... Exhaust pipe, 24 ... Exhaust gas sensor , 26 ... crank angle sensor, 27 ... ECU (abnormality diagnosis means, inter-cylinder variation detection means, inter-cylinder variation correction means, erroneous diagnosis prevention means).

Claims (1)

In the internal combustion engine abnormality diagnosis device comprising abnormality diagnosis means for performing a predetermined abnormality diagnosis based on an output of a sensor that detects information about an operating state of an internal combustion engine having a plurality of cylinders,
Inter-cylinder variation detecting means for obtaining a variation value between cylinders representing variation in operating state between cylinders of the internal combustion engine;
Inter-cylinder variation correcting means for correcting the operation state between the cylinders of the internal combustion engine so as to reduce the variation of the operation state between the cylinders of the internal combustion engine based on the inter-cylinder variation value;
When the inter-cylinder variation correction means by the inter-cylinder variation correction means is not completed, the abnormality diagnosis means prohibits the abnormality diagnosis or relaxes the abnormality determination standard, and also after the completion of the inter-cylinder variation correction, An abnormality diagnosis device for an internal combustion engine, comprising: an erroneous diagnosis prevention means for continuing prohibition of abnormality diagnosis or relaxation of abnormality determination criteria until a period of time elapses.

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