JPH04318249A - Self-diagnostic device fuel supplier for internal combustion engine - Google Patents

Abstract

PURPOSE:To diagnose worsening of air-fuel ratio controllability correlatively to a discharge amount of an exhaust harmful component. CONSTITUTION:An air-fuel ratio feedback correction coefficient LMD for correcting a basic fuel injection amount Tp so that actual air-fuel ratio is obtained to approximate a target is set. Based on a correction coefficient Qhos set increased in accordance with a change width(a-b) and control time tm further increase of an intake air amount Q of the correction coefficient LMD in an air-fuel ratio rich or lean condition up to the preceding time, parameters(SUMR, SUML) corresponding to a control amount by the correction coefficient LMD are set(S11). Here, when these parameters(SUMR, SUML) exceed a predetermined value, an exhaust amount of an exhaust harmful component is judged increased to alarm a result thus judged.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a self-diagnosis device for a fuel supply system for an internal combustion engine, and more specifically, it is designed to feedback-correct the fuel supply amount so that the air-fuel ratio of the intake air-fuel mixture in the internal combustion engine approaches a target air-fuel ratio. This invention relates to self-diagnosis of a constructed fuel supply system.

0002

2. Description of the Related Art Conventionally, there has been an electronically controlled fuel injection system having an air-fuel ratio feedback control function, as disclosed in Japanese Patent Laid-Open Nos. 60-90944 and 61-190142. The air-fuel ratio feedback correction control detects the rich/lean actual air-fuel ratio with respect to the stoichiometric air-fuel ratio (target air-fuel ratio) through the oxygen concentration in the exhaust gas detected by an oxygen sensor installed in the exhaust system. The air-fuel ratio feedback correction coefficient LMD for correcting the fuel injection amount Tp is changed in a direction in which the actual air-fuel ratio approaches the target based on the rich/lean detection.

As described above, by feedback controlling the actual air-fuel ratio to the stoichiometric air-fuel ratio, NO in the three-way catalyst can be reduced.
The conversion efficiency of reduction and oxidation of x, HC, and CO is achieved at a high level, and the three-way catalyst works effectively.

0004

[Problem to be Solved by the Invention] By the way, if there are variations in characteristics or deterioration during production of parts of the fuel supply system such as the air flow meter that detects the intake air flow rate and fuel injection valves, the base will have different characteristics depending on the operating conditions. An error in air-fuel ratio occurs. For example, if an error occurs in the detected value of the intake air flow rate depending on the operating conditions as shown in FIG. 8 due to deterioration of the air flow meter, when the operating condition moves from point A to point B in FIG. Since the detection error at point B is different from the detection error at point B, and the requirements for the correction coefficient LMD to obtain the target air-fuel ratio are different at point A and point B, the correction coefficient L
As shown in Fig. 9, until MD reaches the level corresponding to point A from the level corresponding to point B, the air-fuel ratio deviates from the target and harmful components in the exhaust (in the case shown in Fig. 9, the air-fuel ratio There has been a problem in that leaner fuel consumption increases the amount of NOx emissions.

Therefore, the present applicant has previously proposed a self-diagnosis device for self-diagnosing the deterioration of the air-fuel ratio controllability as described above based on the increase/decrease change in the air-fuel ratio feedback correction coefficient LMD (Patent Application No. -325606). That is,
By detecting at least one of the magnitude of the increase/decrease change in the air-fuel ratio feedback correction coefficient LMD and the control time for increasing/decreasing the fuel injection amount by the correction coefficient LMD, it is possible to detect a state in which a larger correction is required by the air-fuel ratio feedback correction coefficient LMD, in other words. For example, a state in which the base air-fuel ratio deviates significantly from the target is detected, and a warning is issued that the air-fuel ratio controllability (exhaust quality) is deteriorating due to some kind of defect in the fuel supply system.

However, even if the magnitude of change in the correction coefficient LMD and the control time are at the same level, the amount of harmful components (NOx, HC, CO) emitted differs depending on the intake air flow rate at that time (Fig. (Refer to 10), a warning is issued when the amount of harmful components emitted is low, or conversely, no warning is given for deterioration in air-fuel ratio controllability (exhaust properties) even though the amount of harmful components emitted is far above the regulatory level. There are cases,
There has been a problem in that it is not possible to accurately diagnose deterioration in air-fuel ratio controllability in response to the amount of exhaust harmful component emissions.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to make it possible to accurately diagnose a state in which the air-fuel ratio controllability is deteriorated in accordance with the amount of harmful exhaust gas emissions. do.

[0008]

[Means for Solving the Problems] Therefore, a self-diagnosis device for a fuel supply system for an internal combustion engine according to the present invention is shown in FIG.
It is configured as shown in . In FIG. 1, the operating condition detecting means detects the engine operating condition including at least an operating parameter related to the amount of air taken into the engine, and the basic fuel supply amount setting means detects the engine operating condition based on the detected engine operating condition. Set the basic fuel supply amount.

The air-fuel ratio feedback correction value setting means compares the air-fuel ratio of the engine intake air-fuel mixture detected by the air-fuel ratio detection means with a target air-fuel ratio so as to bring the actual air-fuel ratio closer to the target air-fuel ratio. An air-fuel ratio feedback correction value for correcting the basic fuel supply amount is set in . The fuel supply amount setting means sets the final fuel supply amount based on the set basic fuel supply amount and the air-fuel ratio feedback correction value, and the fuel supply control means adjusts the set fuel supply amount to the final fuel supply amount. Based on this, the fuel supply means is driven and controlled.

[0010] Here, the diagnostic means determines at least the magnitude of change in the air-fuel ratio feedback correction value set by the air-fuel ratio feedback correction value setting means and the increase/decrease control time of the basic fuel supply amount by the air-fuel ratio feedback correction value. On the other hand, deterioration of the air-fuel ratio control state in the fuel supply device is diagnosed based on the intake air flow rate of the engine. Here, as shown by the dotted line in FIG. 1, the average value of the intake air flow rate during the rich-lean reversal period of the actual air-fuel ratio with respect to the target air-fuel ratio is calculated, and the average value is used for diagnosis by the diagnostic means. It is preferable to provide an average flow rate calculation means for setting the intake air flow rate as the intake air flow rate.

[0011]

[Operation] In other words, the change in the air-fuel ratio feedback correction value (the magnitude of the change, the increase/decrease control time) indicates the change in the base air-fuel ratio, but as shown in FIG. Even if the changes are the same, the harmful components (CO, HC) emitted depending on the intake air flow rate at that time
, NOx), so by diagnosing not only the change in the air-fuel ratio feedback correction value but also the intake air flow rate at that time, it is possible to perform self-diagnosis that correlates with the amount of harmful exhaust component emissions. did.

0012

[Examples] Examples of the present invention will be described below. In FIG. 2 showing one embodiment, air is taken into an internal combustion engine 1 from an air cleaner 2 via an intake duct 3, a throttle valve 4, and an intake manifold 5. As shown in FIG. Each branch of the intake manifold 5 is provided with a fuel injection valve 6 as a fuel supply means for each cylinder. The fuel injection valve 6 is an electromagnetic fuel injection valve that opens when the solenoid is energized and closes when the energization is stopped, and opens when the solenoid is energized by a drive pulse signal from the control unit 12,
The engine 1 is intermittently injected with fuel that is pressure-fed from a fuel pump (not shown) and adjusted to a predetermined pressure by a pressure regulator.

Each combustion chamber of the engine 1 is provided with a spark plug 7, which ignites a spark to ignite and burn the air-fuel mixture. Then, exhaust gas is discharged from the engine 1 via an exhaust manifold 8, an exhaust duct 9, a three-way catalyst 10, and a muffler 11. The control unit 12 includes a CPU,
Equipped with a microcomputer including ROM, RAM, A/D converter, input/output interface, etc.
It receives input signals from various sensors, performs arithmetic processing as described below, and controls the operation of the fuel injection valve 6.

The various sensors mentioned above include the intake duct 3
An air flow meter 13 such as a hot wire type is provided therein, and outputs a signal corresponding to the intake air flow rate Q of the engine 1. In addition, a crank angle sensor 14 is provided, and in the case of the four-cylinder engine of this embodiment, a reference signal R is provided for every 180 degrees of crank angle.
EF and a unit signal POS every 1° or 2° of crank angle are output. Here, the period of the reference signal REF, or
The engine rotation speed N can be calculated by measuring the number of unit signals POS generated within a predetermined period of time.

A water temperature sensor 15 is also provided to detect the temperature Tw of cooling water in the water jacket of the engine 1. Here, the air flow meter 13, crank angle sensor 14, water temperature sensor 15, etc. correspond to the operating condition detection means in this embodiment, and the operating parameters related to the amount of air taken into the engine are These are the air flow rate Q and the engine rotation speed N.

Further, an oxygen sensor 16 as an air-fuel ratio detecting means is provided at the gathering part of the exhaust manifold 8, and detects the air-fuel ratio of the intake air-fuel mixture via the oxygen concentration in the exhaust gas. The oxygen sensor 16 detects that the oxygen concentration in the exhaust gas is at the stoichiometric air-fuel ratio (
This is a known method that detects whether the actual air-fuel ratio is rich or lean with respect to the stoichiometric air-fuel ratio by utilizing sudden changes after the target air-fuel ratio (in this example). A relatively high voltage signal is output when the air-fuel ratio is rich, and 0V when the air-fuel ratio is lean.
It shall output a nearby low voltage signal.

[0017] Here, the control unit 12
The CPU of the microcomputer built into the
Performs arithmetic processing according to the programs on the ROM shown in the flowchart of FIG. 7, sets the fuel injection amount Ti while executing air-fuel ratio correction control, controls the fuel supply to the engine 1, and self-diagnoses the fuel supply system. I do. In this embodiment, the functions as the basic fuel supply amount setting means, the fuel supply amount setting means, the fuel supply control means, the air-fuel ratio feedback correction value setting means, the diagnosis means, and the average flow rate calculation means are as shown in FIGS. As shown in the flowchart No. 7, the control unit 12 is equipped with software.

The program shown in the flowchart of FIG. 3 calculates the air-fuel ratio feedback correction coefficient LMD (air-fuel ratio feedback correction value) multiplied by the basic fuel injection amount (basic fuel supply amount) Tp so that the actual air-fuel ratio is the target air-fuel ratio. This is a program that uses proportional/integral control to move closer to the stoichiometric air-fuel ratio (stoichiometric air-fuel ratio), and is executed every revolution (1 rev) of the engine 1.

First, in step 1 (indicated as S1 in the figure; the same applies hereinafter), a voltage signal output from the oxygen sensor (O2/S) 16 in accordance with the oxygen concentration in the exhaust gas is read. Then, in the next step 2, the voltage signal from the oxygen sensor 16 read in step 1 and the stoichiometric air-fuel ratio (
slice level (for example, 500 mV) equivalent to the target air-fuel ratio
).

When the voltage signal from the oxygen sensor 16 is greater than the slice level and it is determined that the air-fuel ratio is richer than the stoichiometric air-fuel ratio, the process proceeds to step 3, where it is determined whether or not this rich determination is the first time. Discern. When rich determination is performed for the first time, the process proceeds to step 4, where the previously set air-fuel ratio feedback correction coefficient LMD is set to the maximum value a, and in the next step 5, a predetermined proportion is set from the previous correction coefficient LMD. The correction coefficient LMD is controlled to decrease by subtracting the constant P.

In the next step 6, control is performed using the air-fuel ratio feedback correction coefficient LMD used to enrich the air-fuel ratio in a state where the actual air-fuel ratio is determined to be lean with respect to the target. A parameter SUMR indicating the sum of amounts (total rich control amount) is updated and set according to the following formula. SUMR←SUMR+{(a-b)×tm×Q
hos /KREF-1.0 }The above rich control total amount S
In the UMR calculation formula, (a-b) is the range of change in which the air-fuel ratio feedback correction coefficient LMD was changed in order to enrich the air-fuel ratio in the previous air-fuel ratio lean state, and tm is the change range in which the air-fuel ratio feedback correction coefficient LMD was changed in the previous air-fuel ratio lean state. KREF is the time during which enrichment control is performed in the fuel ratio lean state, and KREF is the time when the enrichment control is performed in the fuel ratio lean state, and KREF is the time when the basic fuel injection amount T
KREF is a correction coefficient that is set based on P and the engine rotational speed N, and the shorter the standard cycle of air-fuel ratio feedback control, the smaller this KREF is set. Furthermore, Qhos is a correction coefficient that is set to increase in accordance with an increase in the intake air flow rate Q detected by the air flow meter 13, and as will be described later, Qhos is a correction coefficient that is set to increase according to an increase in the intake air flow rate Q detected by the air flow meter 13. Value Qav
It is set as a value obtained by dividing Qref by a fixed value Qref.

That is, the rich control total amount SUMR is set to be increased as the time required to invert the air-fuel ratio to rich compared to the standard control cycle is increased, and the air-fuel ratio feedback correction coefficient LMD is set to be increased. Even when it is changed, it is set to be increased accordingly, and the value takes into account both the air-fuel ratio enrichment control time and the increase control amount of the correction coefficient LMD. Furthermore, the richer the intake air flow rate Q at that time, the higher the rich control total amount SUMR is set. When the amount of emissions (emissions) is large, the setting is made to increase.

On the other hand, if it is determined in step 3 that the rich determination is not the first time, the process advances to step 7. In step 7, the value obtained by multiplying the integral constant I by the latest fuel injection amount Ti (final fuel supply amount) is added to the previous correction coefficient L.
The correction coefficient LMD is updated by subtracting it from MD. Furthermore, when it is determined in step 2 that the actual air-fuel ratio is lean relative to the target air-fuel ratio, the correction coefficient LMD is proportionally and integrally controlled in the same manner as in the rich determination (steps 10 and 12). , At the first lean determination, the correction coefficient LMD at that time is set to the minimum value b. Furthermore, at the first lean determination, the lean control total amount SUML is calculated in the same manner as the calculation of the rich control total amount SUMR in step 6.
is calculated according to the following formula.

SUML←SUML+{(a-b)×tm
×Qhos /KREF-1.0 } When the total control amounts SUMR and SUML are calculated in step 6 or step 11, the process proceeds to step 13, where the counter for measuring the rich control time or lean control time is used. There is t
Reset m to zero. In addition, in step 14, the value Qsum, which is the sum of the detected values of the intake air flow rate Q for each unit time between the rich and lean reversals of the air-fuel ratio, is divided by the cumulative number Z, and the intake air flow rate during the rich and lean reversals of the air-fuel ratio is The average value Qav of the air flow rate Q is calculated.

After calculating the average value Qav of the intake air flow rate Q during the recent rich-lean reversal, in the next step 15, the integrated value Qsum and the integrated number Z are reset to zero, and The average value Qav of the intake air flow rate Q at is newly determined. As described above, the integrated value Qsum and integrated number Z, which are reset to zero each time the air-fuel ratio is reversed between rich and lean, are integrated at predetermined time intervals until the air-fuel ratio is next reversed according to the flowchart of FIG. It has become so.

The program shown in the flowchart of FIG. 7 is executed at predetermined minute intervals (for example, 4 ms). First, in step 41, the latest accumulated value Qsum detected by the air flow meter 13 is added to the previous integrated value Qsum. , and set the addition result to a new integrated value Qsum. Further, in the next step 42, the counter Z is incremented by 1 in order to count the number of times of integration.

[0027] Returning to the flowchart of FIG. 3,
In step 16, the air-fuel ratio learning correction coefficient K for each operating region is
Perform air-fuel ratio learning to correct and rewrite BLRC. That is, a learning map is set in which operating regions are divided into a plurality of regions in advance based on the basic fuel injection amount Tp and the engine rotational speed N, and the learning correction coefficient KBLRC is stored in an updatable manner for each operating region. 14, the learning correction coefficient KBLRC corresponding to the operating range to which the current basic fuel injection amount Tp and engine rotational speed N correspond is read from the learning map, and the read learning correction coefficient KBLRC is corrected according to the following formula, Learning correction coefficient KBL after the correction
The learning map is rewritten using RC as new data in the corresponding area.

[0028] KBLRC←KBLRC +X・{(a+b)/2−
1.0 } According to the above calculation formula for the learning correction coefficient KBLRC, a predetermined ratio of the deviation of the average value of the air-fuel ratio feedback correction coefficient LMD from the target convergence value (initial value = 1.0) is added to the learning correction coefficient KBLRC up to that point. The learning correction coefficient KBLRC is gradually corrected so that the target air-fuel ratio can be obtained without correction by the air-fuel ratio feedback correction coefficient LMD.

The program shown in the flowchart of FIG. 4 is a program for calculating the basic fuel injection amount Tp and the final fuel injection amount Ti.
s) is executed every time. First, in step 21, the intake air flow rate Q of the engine detected by the air flow meter 13, the engine rotation speed N calculated based on the detection signal from the crank angle sensor 14, etc. are input.

In the next step 22, the basic fuel injection amount Tp←K×Q/N (K is a constant) corresponding to the cylinder intake air amount is calculated based on the intake air flow rate Q and the engine rotational speed N. . In step 23, the air-fuel ratio feedback correction coefficient LMD and the learning correction coefficient K for each driving region are set by the program shown in the flowchart of FIG.
BLRC, various correction coefficients COEF that are set including a basic correction coefficient, a transient correction coefficient, etc. based on the cooling water temperature Tw detected by the water temperature sensor 15, and the effective opening of the fuel injection valve 6 due to changes in battery voltage. The basic fuel injection amount Tp is corrected based on the correction amount Ts for correcting the change in valve time, etc., and the correction result is set as the final fuel injection amount Ti.

When the predetermined injection timing is reached, the control unit 12 outputs a drive pulse signal with a pulse width corresponding to the fuel injection amount Ti most recently set in step 23 to the fuel injection valve 6, and supplies fuel to the engine 1. is injected intermittently. In the next step 24, the counter tm, which is reset to zero each time the correction coefficient LMD is proportionally controlled, in other words, each time the air-fuel ratio is reversed between rich and lean, is incremented by 1 according to the program shown in the flowchart of FIG. The counter tm is set every time the program shown in FIG. 4 is executed (every 10 ms) from when the air-fuel ratio is inverted to rich/lean until the next rich/lean inversion. is incremented by 1 to measure the lean control time or rich control time.

In the program shown in the flowchart of FIG. 5, in step 31, the engine rotational speed N
and the basic fuel injection amount Tp, the control total amount SUM
Correction coefficient KREF used when calculating R, SUML
is set, and in the next step 32, the average value Qav of the intake air flow rate Q calculated each time the rich/lean reversal is performed in step 14 of the flowchart of FIG. 3 is divided by a preset fixed value Qref. , the total control amount SUMR
, the correction coefficient Qhos used when calculating SUML
Set.

The correction coefficient Qhos is set to increase as the intake air flow rate Q increases, so that the total control amount S
Since UMR and SUML are corrected in an increasing direction that makes it easier to diagnose deterioration of the air-fuel ratio, even if the concentration of harmful components is the same, the higher the intake air flow rate Q and the higher the exhaust amount, the worse the air-fuel ratio controllability becomes. It is now easier to diagnose. As mentioned above, the correction coefficient Q is calculated using the instantaneous value of the intake air flow rate Q.
If instead of setting hos, the average value Qav of the intake air flow rate Q during the air-fuel ratio reversal is used,
For example, the intake air flow rate Q related to the amount of exhaust harmful components discharged can be accurately captured without being affected by fluctuations in the intake air flow rate Q during transient operation.

The self-diagnosis program shown in the flow chart of FIG. 6 is executed at predetermined intervals (for example, every 5 minutes). Total control amount SU
MR is compared with a slice level SL1 that is preset for determining the rich control total amount SUMR. Here, the rich control total amount SUMR is set to increase when the range of increase in the air-fuel ratio feedback correction coefficient LMD is large and when the time for increasing the correction coefficient LMD by integral control is long, so the rich control total amount SUMR increases. shows a lean tendency of the air-fuel ratio, but at the same time, the rich control total amount SUMR is set to increase in accordance with an increase in the intake air flow rate Q.

Therefore, even if the lean tendency is relatively small, the slice level SL1 will be exceeded when the intake air flow rate Q is large and the amount of NOx discharged is large. If the NOx concentration increases and the exhaust amount increases, the rich control total amount SUMR will be corrected by a correction coefficient Qhos corresponding to the intake air flow rate Q. It is now possible to make a diagnosis by correlating the amount of harmful components released.

Therefore, when it is determined in step 51 that the rich control total amount SUMR exceeds the slice level SL1, the process proceeds to step 52, and a display installed near the driver's seat, for example, indicates that the NOx emission amount is increasing. Warn the driver using a device (warning lamp), etc. On the other hand, if it is determined in step 51 that the rich control total amount SUMR is less than the slice level SL1, NO
Assuming that there is no abnormal increase in x emissions, step 52
Jump to step 53.

In step 53, in the same way as step 51, the total lean control amount SUML set in step 11 of the flowchart of FIG. 3 and the total lean control amount S are calculated.
It is compared with a slice level SL2 preset for UML determination. Here, the total amount of lean control SUM
When L exceeds the slice level SL2, it is determined that the amount of HC and CO emissions in the exhaust gas is increasing due to the tendency of the air-fuel ratio to become richer, and in step 54, the amount of CO and H
Warn the driver that C emissions are increasing.

On the other hand, in step 53, the lean control total amount S
When it is determined that the UML is below the slice level SL2, it is determined that there is no noticeable increase in the amount of CO and HC discharged, and the process skips step 54 and proceeds to step 55. In step 55, the average value SUM of the rich control total amount SUMR and the lean control total amount SUML is calculated.

Then, in step 56, the average value S
By comparing UM with a preset slice level SL3, it is determined whether the change width and period of the correction coefficient LMD are abnormally small. If SUM<SL3, the process proceeds to step 57 to determine NOx, HC, A warning is issued if there is an abnormality in any of the CO emissions. For example, if only one specific cylinder out of four or six cylinders becomes lean due to clogging of a fuel injection valve, the output of the oxygen sensor 16 temporarily decreases when exhaust from the lean cylinder is detected. At this time, such a temporary lean change is also regarded as a reversal of the air-fuel ratio, and proportional control is added, and the control period of the correction coefficient LMD becomes shorter than in normal times, so that the average value SUM becomes smaller.

As mentioned above, when only the air-fuel ratio of one specific cylinder becomes lean, the average air-fuel ratio obtained as a result of the air-fuel ratio feedback correction control also becomes lean;
If only the air-fuel ratio of the cylinder becomes rich, the average air-fuel ratio obtained as a result of the air-fuel ratio feedback correction control also becomes rich. Therefore, when the average value SUM is less than the slice level SL3, it is presumed that the air-fuel ratio of only the specific cylinder is deviating to the rich or lean side, but the direction of the deviation cannot be specified, so step 57 , an abnormality in the amount of exhaust harmful components (NOx, CO, HC) is displayed.

As described above, the rich control total amount SUM
After diagnosing the deterioration of the air-fuel ratio control state in the fuel supply control system based on R and the total lean control amount SUML, in the next step 58, the total control amounts SUMR and SUML are reset to zero, as shown in the flowchart of FIG. Until the program is executed next time, the control total amounts SUMR and SUML are updated every time the air-fuel ratio is reversed, according to the flowchart of FIG.

In this embodiment, the total control amounts SUMR and SUML, which incorporate the three elements of the change width of the air-fuel ratio feedback correction coefficient LMD, the control time, and the intake air flow rate Q, are compared with the predetermined slice level SL. Although the deterioration of the air-fuel ratio control condition is diagnosed, for example, the total control amount SUM
Instead of removing the correction coefficient Qhos from the calculation formula of R, SUML, the slice level SL is calculated by using the intake air flow rate Q at that time.
The diagnosis method using the diagnostic parameters such as the range of change in the air-fuel ratio feedback correction coefficient LMD, the control time, and the intake air flow rate Q is not limited to this embodiment.

Furthermore, although the diagnostic performance is degraded, only one of the variation width of the air-fuel ratio feedback correction coefficient LMD and the control time may be used for diagnosis. Furthermore, the intake air flow rate Q does not need to be directly detected by the air flow meter 13; for example, a sensor that detects the intake negative pressure may be provided instead of the air flow meter 13, and the sensor may be connected to the detected intake negative pressure. Based on the basic fuel injection amount T
In the fuel supply system in which p is calculated, the intake air flow rate may be determined by calculation from the basic fuel injection amount Tp (cylinder intake air amount) based on the intake negative pressure and the engine rotation speed.

[0044]

As explained above, according to the present invention, at least one of the magnitude of change in the air-fuel ratio feedback correction value and the control time for increasing/decreasing the basic fuel supply amount by the air-fuel ratio feedback correction value, and the intake air flow rate of the engine. Since the deterioration of the air-fuel ratio control state is diagnosed based on the above, there is an effect that the air-fuel ratio control state can be diagnosed with high accuracy by correlating it with the amount of exhaust harmful component emissions.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the basic configuration of the present invention.

FIG. 2 is a system schematic diagram showing an embodiment of the present invention.

FIG. 3 is a flowchart showing air-fuel ratio feedback control.

FIG. 4 is a flowchart showing fuel injection amount setting control.

FIG. 5 is a flowchart showing control of setting various correction coefficients.

FIG. 6 is a flowchart showing self-diagnosis control.

FIG. 7 is a flowchart for determining the integrated value of the intake air flow rate Q.

FIG. 8 is a diagram showing an example of detection errors due to air flow meter deterioration.

FIG. 9 is a time chart showing the state of air-fuel ratio deviation when air flow meter deterioration occurs.

FIG. 10 is a time chart showing differences in the amount of harmful components discharged due to differences in intake air flow rate (rotational speed).

[Explanation of symbols]

1. Institution 6 Fuel injection valve 12 Control unit 13 Air flow meter 14 Crank angle sensor 15 Water temperature sensor 16 Oxygen sensor

Claims (2)

[Claims] 1. Operating condition detection means for detecting engine operating conditions including at least operating parameters related to the amount of air taken into the engine; and basic fuel supply based on the engine operating conditions detected by the operating condition detection means. A basic fuel supply amount setting means for setting the amount of fuel supply, an air-fuel ratio detection means for detecting the air-fuel ratio of the engine intake air-fuel mixture, and an air-fuel ratio detected by the air-fuel ratio detection means and a target air-fuel ratio are compared to determine the actual air-fuel ratio. an air-fuel ratio feedback correction value setting means for setting an air-fuel ratio feedback correction value for correcting the basic fuel supply amount so that the air-fuel ratio approaches the target air-fuel ratio; a fuel supply amount setting means for setting a final fuel supply amount based on the fuel supply amount setting means; and a fuel supply control means for driving and controlling the fuel supply means based on the fuel supply amount set by the fuel supply amount setting means. In the fuel supply system for an internal combustion engine configured, the magnitude of change in the air-fuel ratio feedback correction value set by the air-fuel ratio feedback correction value setting means and the increase/decrease control time of the basic fuel supply amount by the air-fuel ratio feedback correction value are controlled. A self-diagnosis device for a fuel supply system for an internal combustion engine, characterized in that it is configured to include a diagnostic means for diagnosing deterioration of the air-fuel ratio control state in the fuel supply system based on at least one side and an intake air flow rate of the engine. . 2. Calculating the average value of the intake air flow rate during the rich/lean inversion period of the actual air-fuel ratio with respect to the target air-fuel ratio, and setting the average value as the intake air flow rate of the engine used for diagnosis in the diagnostic means. 2. A self-diagnosis device for a fuel supply system for an internal combustion engine according to claim 1, further comprising an average flow rate calculation means.