JP2681566B2 - Self-diagnosis device in fuel supply control 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 self-diagnosis device in a fuel supply control device for an internal combustion engine, and more particularly, in a fuel supply control device having an air-fuel ratio learning correction function, a fuel is obtained using the result of the air-fuel ratio learning. The present invention relates to a device capable of diagnosing an abnormality in a supply system.

[0002]

2. Description of the Related Art Conventionally, in an electronically controlled fuel injection device for an internal combustion engine having an air-fuel ratio feedback correction control function,
JP-A-60-90944, JP-A-61-1901
As disclosed in Japanese Patent Application Publication No. 42-42, etc., there is one that adopts air-fuel ratio learning control. In the air-fuel ratio feedback correction control, the rich lean of the actual air-fuel ratio with respect to the target air-fuel ratio (for example, the theoretical air-fuel ratio) is discriminated by the oxygen sensor provided in the engine exhaust system, and the air-fuel ratio feedback compensation coefficient LMD is determined based on the discrimination result. The basic fuel injection amount Tp, which is set by proportional / integral control and calculated from the intake air flow rate detected by the air flow meter and the engine rotation speed, is corrected by the air-fuel ratio feedback correction coefficient LMD to obtain an actual air-fuel ratio. The fuel ratio is feedback-controlled to the target air-fuel ratio.

Here, the deviation of the air-fuel ratio feedback correction coefficient LMD from the reference value (target convergence value) is learned for each of a plurality of operating regions, and the air-fuel ratio learning correction coefficient KB
LRC (air-fuel ratio learning correction value) is determined, the basic fuel injection amount Tp is corrected by the learning correction coefficient KBLRC, and the correction coefficient LM
The base air-fuel ratio obtained without D is made to substantially match the target air-fuel ratio, and the air-fuel ratio feedback control is further corrected by the correction coefficient LMD to calculate the fuel injection amount Ti.

[0004] This makes it possible to perform fuel correction corresponding to different correction requests for each operating condition, stabilize the actual air-fuel ratio near the stoichiometric air-fuel ratio, maintain good conversion efficiency in the three-way catalytic converter, and improve the exhaust gas. Harmful component concentration can be controlled to a low level.

[0005]

By the way, when the base air-fuel ratio largely deviates from the target air-fuel ratio due to failure or deterioration of the components of the fuel supply system such as the fuel injection valve, the fuel pump, the pressure regulator and the like. Even if the air-fuel ratio learning progresses and the air-fuel ratio feedback correction coefficient LMD converges to the target on average on the average, it may actually cause deterioration of the exhaust property (increase in concentration of exhaust harmful components). is there. Therefore, the self-diagnosis of changes in the base air-fuel ratio due to such an abnormality in the fuel supply system, and based on the results of this diagnosis, prompt replacement and maintenance of parts at the failure / degradation point in the fuel supply system to achieve the target air-fuel ratio. There has been a demand for early avoidance of operation in the situation where controllability (exhaust properties) has deteriorated.

Here, as a method for diagnosing the fuel supply system, in the fuel supply device having the air-fuel ratio learning correction function as described above, the required correction value for obtaining the target air-fuel ratio is learned for each operating region. When the average value of the learning correction coefficient KBLRC has a deviation more than a predetermined value from the initial value, a large change in the base air-fuel ratio has occurred due to a failure or deterioration of parts in the fuel supply system. I considered how to estimate.

However, in the learning transition state until each of the learning correction coefficients KBLRC (air-fuel ratio learning correction value) for each operating region is learned corresponding to the changed base air-fuel ratio, the learning correction in the unlearned region is performed. Since the coefficient KBLRC does not accurately indicate a change in the base air-fuel ratio, a large change in the base air-fuel ratio can be diagnosed based on the average value of the learning correction coefficient KBLRC until learning is sufficiently advanced. However, there is a problem that the operation is performed with the air-fuel ratio controllability deteriorated until the learning result corresponding to the change of the base air-fuel ratio is updated in each operation region.

[0008] Therefore, the applicant of the present invention, the learning correction coefficient KB
We have previously proposed a device that makes a diagnosis based on the level difference between the operating regions of the LRC (see Japanese Patent Application No. 3-85419). However, since each learning correction coefficient is learned including a supply error amount in a fuel supply system such as a fuel injection valve or a fuel pump, a detection error amount by an air flow meter, and other various variations, it is general. If the operating region with a low intake air flow rate that can be learned and experienced in various operating modes is set as the operating region for obtaining the step, the air flow meter will generate a larger detection error in the region with a lower intake air flow rate (see FIG. 8). There is a problem that the error of the meter has a great influence, and the abnormality of the fuel supply system cannot be accurately diagnosed by being distinguished from the occurrence of the detection error of the air flow meter.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a self-diagnosis apparatus capable of diagnosing an abnormality in a fuel supply system by eliminating the influence of an air flow meter detection error from the result of air-fuel ratio learning. And

[0010]

Therefore, a self-diagnosis device in a fuel supply control device for an internal combustion engine according to the present invention is
It is configured as shown in FIG. In FIG. 1, the flow rate detection means detects the intake air flow rate of the engine, and the rotation speed detection means detects the rotation speed of the engine.

The basic amount setting means sets the basic fuel supply amount based on the intake air flow rate and the engine rotation speed. Further, the feedback correction means compares the air-fuel ratio of the engine intake air-fuel mixture detected by the air-fuel ratio detection means with the target air-fuel ratio, and adjusts the basic fuel supply amount so that the actual air-fuel ratio approaches the target air-fuel ratio. The air-fuel ratio feedback correction value for correction is set.

Further, the storage means rewritably stores an air-fuel ratio learning correction value for correcting the basic fuel supply amount for each of the operating regions divided into a plurality of portions based on the engine load and the engine rotation speed. Further, the air-fuel ratio learning means learns the deviation of the air-fuel ratio feedback correction value from the target convergence value, and reduces the deviation of the air-fuel ratio learning correction value stored in the storage means corresponding to the relevant operating region. Correct the direction and rewrite.

The fuel supply amount setting means sets the final fuel supply amount based on the basic fuel supply amount, the air-fuel ratio feedback correction value, and the air-fuel ratio learning correction value stored in the corresponding operating region in the storage means. Then, the control means drives and controls the fuel supply means based on the fuel supply amount set by the fuel supply amount setting means. On the other hand, the learning deviation calculation means calculates the deviation of the air-fuel ratio learning correction value corresponding to each of the two different representative operation areas having substantially the same intake air flow rate level in the storage means, and the diagnosis means performs the calculation. The abnormality of the fuel supply system is diagnosed based on the absolute value of the deviation.

Here, when the two representative operation regions include a plurality of operation regions in which the air-fuel ratio learning correction values are learned, the air-fuel ratio learning correction values corresponding to each of the two representative operation regions are set. Alternatively, the average value of the air-fuel ratio learning correction values in each representative operation region may be used.

[0015]

With this configuration, when the fuel supply system is diagnosed on the basis of the air-fuel ratio learning correction value learned for each of the operating regions divided into a plurality of sections based on the engine load and the engine rotation speed, the intake air flow rate level is Are compared, and the air-fuel ratio learning correction values in two different representative operation regions are compared. Here, the detection error by the intake air flow rate detection means is approximately the same level if the intake air flow rate level is approximately the same,
In the two representative operation areas, the learning value includes a detection error amount of the intake air flow rate detection means of the same degree.
The deviation of the air-fuel ratio learning correction value between the two representative operation regions is caused by an abnormality in the fuel supply system other than the detection error. Therefore, even if the detection error of the intake air flow rate detection means occurs, the abnormality of the fuel supply system is diagnosed without being affected by the detection error.

[0016]

Embodiments of the present invention will be described below. In FIG. 2 showing one embodiment, air is sucked into an internal combustion engine 1 from an air cleaner 2 through an intake duct 3, a throttle valve 4 and an intake manifold 5. Each branch of the intake manifold 5 is provided with a fuel injection valve 6 as fuel supply means for each cylinder. The fuel injection valve 6 is an electromagnetic fuel injection valve that is energized by a solenoid and opens, and is deenergized and closed by being energized by a drive pulse signal from a control unit 12, which will be described later. Fuel which is pressure-fed from a fuel pump (not shown) and adjusted to a predetermined pressure by a pressure regulator is intermittently injected and supplied to the engine 1.

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

The various sensors include an intake duct 3
An air flow meter 13 as a flow rate detecting means is provided therein and outputs a signal according to the intake air flow rate Q of the engine 1. Further, in the case of the four cylinders of the present embodiment, which is provided with the crank angle sensor 14, the reference signal REF for every 180 ° of crank angle and the unit signal POS for every 1 ° or 2 ° of crank angle.
Is output. Here, the engine speed Ne can be calculated by measuring the period of the reference signal REF or the number of occurrences of the unit signal POS within a predetermined time. Therefore, the crank angle sensor 14 corresponds to the rotation speed detecting means in this embodiment.

A water temperature sensor 15 for detecting a cooling water temperature Tw of the water jacket of the engine 1 is provided.
Further, an oxygen sensor 16 as an air-fuel ratio detecting means is provided at the collecting portion of the exhaust manifold 8 to detect the air-fuel ratio of the intake air-fuel mixture via the oxygen concentration in the exhaust gas. The oxygen sensor 16
Is a known method for detecting the rich lean of the actual air-fuel ratio with respect to the theoretical air-fuel ratio by utilizing the fact that the oxygen concentration in the exhaust gas suddenly changes at the stoichiometric air-fuel ratio (the target air-fuel ratio in this embodiment). is there.

Here, the CPU of the microcomputer incorporated in the control unit 12 performs arithmetic processing according to the programs on the ROM shown in the flow charts of FIGS. 3 to 5, and performs air-fuel ratio feedback correction control and emptying for each operating region. While executing the fuel ratio learning correction control, the fuel injection amount Ti is set and the fuel supply to the engine 1 is controlled, while the self-diagnosis of the fuel supply system including the fuel injection valve 6, the fuel pump, the pressure regulator and the like is performed. To do.

In this embodiment, the basic amount setting means,
As shown in the flow charts of FIGS. 3 to 5, the control unit 12 is provided with software as functions of the feedback correction means, the air-fuel ratio learning means, the fuel supply amount setting means, the control means, the learning deviation calculation means, and the diagnosis means. In addition, as a storage means, the control unit 12
It is assumed that the RAM with a backup function of a microcomputer (not shown) built in is equivalent to the RAM.

The program shown in the flowchart of FIG. 3 is a program for setting the air-fuel ratio feedback correction coefficient LMD (air-fuel ratio feedback correction value) by which the basic fuel injection amount (basic fuel supply amount) Tp is multiplied by proportional / integral control. And is executed every one revolution (1 rev) of the engine 1. First, in step 1 (referred to as S1 in the figure, the same applies hereinafter), a voltage signal output from the oxygen sensor 16 according to the oxygen concentration in the exhaust gas is read.

Then, in the next step 2, step 1
The voltage signal from the oxygen sensor 16 read in step 2 and the slice level (for example, 500 mV) corresponding to the stoichiometric air-fuel ratio (target air-fuel ratio)
Compare with When it is determined that the voltage signal from the oxygen sensor 16 is higher than the slice level and the air-fuel ratio is richer than the stoichiometric air-fuel ratio, the process proceeds to step 3, where it is determined whether the current rich determination is the first time.

When the rich determination is the first time, the routine proceeds to step 4, where the air-fuel ratio feedback correction coefficient LMD set up to the previous time is set to the maximum value a. In the next step 5, the reduction coefficient LMD is controlled by subtracting a predetermined proportionality constant P from the correction coefficient LMD up to the previous time. In step 6, 1 is set to a flag FP indicating that the proportional control has been executed.

On the other hand, when it is judged at step 3 that the rich judgment is not the first time, the routine proceeds to step 7, where a value obtained by multiplying the integration constant I by the latest fuel injection amount Ti is subtracted from the correction coefficient LMD up to the previous time. To update the correction coefficient LMD. When it is determined in step 2 that the air-fuel ratio is lean with respect to the target, similarly to the rich determination, first, in step 8, it is determined whether or not the current lean determination is the first time. If it is the first time, the process proceeds to step 9 and the correction coefficient LMD up to the previous time is set to the minimum value b.

In the next step 10, the proportional constant P is added to the correction coefficient LMD up to the previous time to update it, and in step 11, the flag FP is set to 1. If it is determined in step 8 that the lean determination is not the first time,
Proceeding to 12, the value obtained by multiplying the integration constant I by the latest fuel injection amount Ti is added to the correction coefficient LMD up to the previous time.

The program shown in the flow chart of FIG. 4 is an air-fuel ratio learning program for each operating region, and is executed every predetermined minute time (for example, 10 ms). In step 21, the flag FP is determined. When FP is 1, the process proceeds to step 22 to reset the FP to zero, and then performs various processes according to the present program. When it is zero, the program is terminated as it is.

When the FP is reset to zero in step 22,
In the next step 23, the basic fuel injection amount Tp (= K × Q / N; K is a constant) representing the engine load and the engine rotation speed Ne.
In order to identify the region to which the current operating conditions apply, on the learning map (see Fig. 6) that rewritably stores the air-fuel ratio learning correction coefficient KBLRC for each operating region divided into multiple parameters using The basic fuel injection amount Tp and the engine rotation speed Ne are read respectively.

Then, in the next step 24, step 23
The basic fuel injection amount Tp and the engine speed Ne read by
-Fuel ratio learning correction in the region on the learning map corresponding to
Read the coefficient KBLRC and set it as KBLRC._OLDSet to
You. In step 25, the air-fuel ratio feedback correction
Average value of maximum and minimum values a and b of several LMD (= (a + b) /
2) and the convergence target value (the initial value of the correction coefficient LMD,
In the embodiment, the predetermined ratio X of the deviation from 1.0) is used as the air-fuel ratio.
Learning correction coefficient KBLRC _OLDThe value added to
Tana air-fuel ratio learning correction coefficient KBLRC_NEW(← KBLRC_OLD+ X
・ Set as {(a + b) /2-1.0}).

By this learning, the correction amount by the air-fuel ratio feedback correction coefficient LMD is converted into the air-fuel ratio learning correction coefficient KBLRC for each operation region, and the deviation between the air-fuel ratio feedback correction coefficient LMD and the convergence target value can be reduced. While stabilizing the air-fuel ratio feedback correction coefficient LMD near the target convergence value, it becomes possible to meet different correction requests depending on the operating region.

In step 26, the air-fuel ratio learning correction coefficient
KBLRC _NEW is rewritten as map data as update data corresponding to the corresponding area on the learning map. Furthermore,
In the next step 27, the learning counter for each area corresponding to the area in which the map data has been rewritten in step 26 is incremented so that the number of learning experiences can be determined for each operating area.

As for the final fuel injection amount Ti (fuel supply amount), the basic fuel injection amount Tp is calculated from the intake air flow rate Q and the engine speed Ne, while various values are set according to operating conditions such as the cooling water temperature Tw. A correction coefficient CO is set, and further, the air-fuel ratio feedback correction coefficient LMD and the air-fuel ratio learning correction coefficient KBLRC stored in the corresponding operation area on the learning map are read, and Ti = Tp × CO × LMD ×
It is designed to be calculated as KBLRC. Then, at a predetermined injection timing synchronized with the engine rotation, a drive pulse signal having a pulse width corresponding to the latest calculated fuel injection amount Ti is output to the fuel injection valve 6, thereby controlling the fuel supply to the engine. Is done.

After the learning counter is incremented in step 27, the fuel supply system is diagnosed in step 28 based on the air-fuel ratio learning correction coefficient KBLRC for each operating region stored in the learning map. Details of the diagnosis in step 28 are shown in the flowchart of FIG. In the flowchart of FIG. 5, first, in step 31,
It is determined whether or not the corresponding region in which the learning correction coefficient KBLRC is rewritten this time is one of two different representative operation regions A and B preset on the learning map.

Then, when the learning is performed in the area A when it corresponds to the area A, the process proceeds to step 32, and it is determined whether or not the learning counter corresponding to the area A is a predetermined value or more. If it is recognized that the learning counter is equal to or greater than the predetermined value and the learning is sufficiently advanced (the learning correction coefficient KBLRC represents the correction request of the corresponding region with high accuracy), the process proceeds to step 33 and corresponds to the A region. Learning correction coefficient KBLR stored as
Set C to MA.

Similarly, in steps 34 to 36, the learning counter is discriminated for the other B area of the two different representative operation areas A and B, and when the learning has progressed sufficiently, the area B is dealt with. Set learning correction coefficient KBLRC to MB. In this way, when the learning correction coefficient KBLRC at the stage where the learning has progressed sufficiently in each of the representative operation regions A and B is set to MA and MB, respectively, in the next step 37, the absolute deviation of MA and MB is absolute. The value is compared with the predetermined value ΔL.

When it is determined that the absolute value of the deviation between MA and MB is greater than or equal to the predetermined value ΔL, the routine proceeds to step 38, where the fuel of the system including the fuel injection valve 6 and the fuel pump is used. Diagnose abnormalities in the supply system.
The abnormality diagnosis result may be notified to the driver by, for example, a warning lamp provided near the driver's seat of the vehicle.

Here, the two representative operating areas A and B
As shown in FIG. 6, the level of the intake air flow rate Q is substantially equal (in the equal Q, etc.) in the operation region divided into a plurality with the basic fuel injection amount Tp (engine load) and the engine rotation speed Ne as parameters. 2) are set as two different areas. Therefore, when a detection error occurs in the air flow meter 13 that detects the intake air flow rate Q, which causes an air-fuel ratio deviation, a correction amount for correcting the air-fuel ratio deviation due to the detection error of the intake air flow rate Q is generated. For 2
The learning correction coefficient KBLRC between the two representative operation areas A and B should be learned substantially evenly in the one representative operation area.
If there is a large gap between the two, it can be estimated that the air-fuel ratio deviation has occurred at least due to a factor other than the detection error of the air flow meter 13.

As factors of the air-fuel ratio deviation other than the detection error of the air flow meter 13, abnormalities in the fuel supply system such as clogging of the fuel injection valve 6, leakage and changes in fuel pressure, and other variations are predicted. Since the influence of various factors on the abnormality of the fuel supply system is sufficiently small, if there is a large learning step above a predetermined level between the two representative operation regions, a large air-fuel ratio deviation due to the abnormality of the fuel supply system will occur. Can be regarded as the result of learning, and thus it can be determined that it is due to an abnormality in the fuel supply system.

As described above, according to the present embodiment, the influence of the detection error of the air flow meter 13 can be eliminated and the abnormality of the fuel supply system can be diagnosed with high accuracy, and based on the diagnostic result, it can be swift and reliable. If the maintenance can be promoted, it becomes possible to avoid the operation at an early stage when the air-fuel ratio controllability is deteriorated due to the abnormality of the fuel supply system. In setting the two representative operation areas A and B, the operation areas are not simply equal in intake air flow rate Q level, but are areas that can be experienced in a predetermined operation mode (areas where the intake air flow rate Q is low). However, it is preferable that the correction request levels in the respective driving regions are compared with high accuracy based on rapid learning convergence as a region having many driving opportunities). In the region where the intake air flow rate Q is low, the detection error of the air flow meter 13 is larger than in the region where the intake air flow rate Q is large, but as described above, the two representative operation regions are in the region where the intake air flow rate Q is substantially the same. Since the setting is made, even in the region where the detection error is large, the influence of the detection error can be eliminated and the diagnosis can be performed, and the fuel supply system can be highly accurately diagnosed in the region where the learning is easy.

Further, in the above embodiment, the unit operation area in which the learning correction coefficient KBLRC is stored on the learning map is the representative operation area, but an area in which some unit operation areas in which the learning correction coefficient KBLRC is stored are collected. Is a representative operating area, and learning correction coefficients for a plurality of unit areas included in the representative operating area
The average value of KBLRC may be treated as the learning correction coefficient KBLRC in the representative operation area (see FIG. 7).

That is, in FIG. 7, the learning correction coefficient KBLRC that is learned and updated is stored in each of the operating regions a, b, c, and d included in the region A. Correction coefficient KBLR in each operating region of c, c, and d
The simple average value of C is calculated, and this average value is used as the learning correction coefficient KBLRC for the area A. Similarly, the deviation from the learning correction coefficient KBLRC for the area B, which is obtained as the average value, is calculated, and the absolute value level of this deviation is calculated. The diagnosis is performed based on.

As described above, if the two representative operating regions to be compared are made up of a plurality of unit operating regions, the learning correction coefficient KBLRC of the plurality of unit operating regions is averaged to supply the fuel. The influence of various variations other than system abnormalities is reduced, and the fuel supply system can be diagnosed more accurately.

[0043]

As described above, according to the present invention, in the fuel supply control device having the function of learning and correcting the air-fuel ratio for each operating region, the fuel supply system of the fuel supply system is used by using the air-fuel ratio learning correction value for each operating region. In performing the diagnosis, the influence of the detection error of the intake air flow rate can be eliminated to diagnose the fuel supply system, and even if the detection error of the intake air flow rate occurs,
There is an effect that the fuel supply system can be diagnosed with high accuracy.

[Brief description of the drawings]

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

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

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

FIG. 4 is a flowchart showing air-fuel ratio learning control.

FIG. 5 is a flowchart showing self-diagnosis of a fuel supply system.

FIG. 6 is a diagram showing a state of a learning map in the embodiment.

FIG. 7 is a diagram showing another example of setting a representative operation area.

FIG. 8 is a diagram showing a detection error characteristic of the air flow meter.

[Explanation of symbols]

 1 engine 6 fuel injection valve 12 control unit 13 air flow meter 14 crank angle sensor 16 oxygen sensor

Claims (2)

(57) [Claims] 1. A flow rate detection means for detecting an intake air flow rate of an engine, a rotation speed detection means for detecting a rotation speed of the engine, and a basic fuel supply amount based on the detected intake air flow rate and the engine rotation speed. The air-fuel ratio detecting means for detecting the air-fuel ratio of the engine intake air-fuel mixture, and the actual air-fuel ratio by comparing the air-fuel ratio detected by the air-fuel ratio detecting means with the target air-fuel ratio. Feedback correction means for setting an air-fuel ratio feedback correction value for correcting the basic fuel supply amount so as to approach the target air-fuel ratio, and the basic for each operating region divided into a plurality based on the engine load and the engine speed. Storage means for rewritably storing an air-fuel ratio learning correction value for correcting the fuel supply amount; and a storage means for learning a deviation of the air-fuel ratio feedback correction value from a target convergence value. Air-fuel ratio learning means for correcting and rewriting the air-fuel ratio learning correction value stored corresponding to the relevant operating region in a direction to reduce the deviation, the basic fuel supply amount, the air-fuel ratio feedback correction value, and the storage A fuel supply amount setting means for setting a final fuel supply amount on the basis of the air-fuel ratio learning correction value stored in the operating region, and a fuel supply amount set by the fuel supply amount setting means. A fuel supply control device for an internal combustion engine, comprising: a control unit that drives and controls a fuel supply unit; and a fuel supply control device for an internal combustion engine that corresponds to two different representative operation regions having substantially the same intake air flow rate level in the storage unit. Learning deviation calculation means for calculating the deviation of the air-fuel ratio learning correction value, and abnormality of the fuel supply system based on the absolute value of the deviation calculated by the learning deviation calculation means A self-diagnosis device in a fuel supply control device for an internal combustion engine, comprising: a diagnosis means for diagnosing. 2. The two representative operation regions include a plurality of operation regions in which air-fuel ratio learning correction values are learned, and the air-fuel ratio learning correction values corresponding to the two representative operation regions are The self-diagnosis device in the fuel supply control device for an internal combustion engine according to claim 1, wherein the self-diagnosis device is an average value of the air-fuel ratio learning correction values in the representative operating region.