JPH07310575A - Abnormality judging device and abnormality informing device for internal combustion engine - Google Patents

Abstract

PURPOSE:To precisely detect leakage of exhaust by using a learning value of an air-fuel ratio correction factor. CONSTITUTION:In learning values KGn, each of which is learned in every operation area on the basis of a deviation from a value 1.0 of an air-fuel ratio correction factor FAF, a learning value KG1 in an idling condition is the value for a high air-fuel ratio condition of an air-fuel mixture or more (S140) and leaning values KG3, KG4 learned by a running test in an acceleration area are not deviated from each other, it is determined that exhaust leakage occurs (S170, S180). If exhaust is leaked, new air is sucked by pulsation of a pressure in an exhaust system, so that air-fuel ratio control based on the output of an air-fuel ratio sensor is carried out in the same way as for an excess air condition of an air-fuel mixture. The deviation in the learning value KG by this control is generated greatly only in a low load area, so that existence of exhaust leakage can be precisely detected by determining a dimension of the learning value in the acceleration area additionally.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an O system for outputting a signal corresponding to an air-fuel ratio of an air-fuel mixture drawn into an internal combustion engine to an exhaust system.
The present invention relates to an abnormality determination device and an abnormality notification device for an internal combustion engine that determines exhaust leakage in a device that includes air-fuel ratio detection means such as a sensor and that feeds back the air-fuel ratio of an air-fuel mixture based on the output signal of this sensor.

[0002]

2. Description of the Related Art If exhaust gas leaks from an exhaust pipe upstream of a catalytic converter due to cracks in the exhaust pipe, the exhaust gas that has not been purified by the catalytic converter is directly discharged to the atmosphere, which is a serious problem. There is a risk. Therefore, conventionally, an abnormality determination device for determining the occurrence of exhaust gas leakage has been devised. For example, the applicant of the present application uses the fact that when there is exhaust gas leakage, the output of the catalytic converter or the O2 sensor provided downstream thereof is on the side (lean side) where the air-fuel ratio is large, and the exhaust gas leakage is detected. A determination device has been proposed (JP-A-3-134241). This is because the exhaust has pulsation (pulsation cycle) in synchronism with the explosive combustion of each cylinder in the internal combustion engine, and the outside air is sucked in from the place where the exhaust leaks.

[0003]

The present invention is an excellent one that focuses on the mode of exhaust gas leakage. However, when the exhaust gas leakage is actually detected using the output of the O2 sensor, it depends on the operating condition of the internal combustion engine. Have been found to be difficult to detect. Also, if the output of the O2 sensor deviates to the lean side due to aging, etc.
It may have been difficult to set the detection margin. If the determination conditions are set to be strict so that the false detection of the exhaust gas leakage may occur, the accuracy of the exhaust gas leakage detection may decrease.

The abnormality determination device for an internal combustion engine of the present invention has been made in view of these problems, and an object thereof is to detect exhaust gas leakage accurately and surely.

[0005]

[Means for Solving the Problems] In order to achieve such an object, as a means for solving the above problems, the present invention has the following configurations. A first internal combustion engine abnormality determination device according to the present invention is provided in an exhaust passage of an internal combustion engine, and air-fuel ratio detection means for outputting a signal corresponding to an air-fuel ratio of an air-fuel mixture drawn into the internal combustion engine; Based on the signal from the fuel ratio detection means, feedback control the air-fuel ratio of the air-fuel mixture sucked into the internal combustion engine, at least in the low load region of the internal combustion engine and other than the low load region, based on the feedback value. The learning means for learning the air-fuel ratio correction value and the learned air-fuel ratio correction value in the low load region are values corresponding to the case where the air-fuel ratio of the air-fuel mixture is large,
And, when it is determined that the learned value is a value when the air-fuel ratio of the air-fuel mixture is larger than the learned air-fuel ratio correction value in a region other than the low load region, an exhaust leakage determination means that determines that exhaust leakage exists. The summary is that

A second abnormality determining apparatus for an internal combustion engine according to the present invention is an air-fuel ratio detecting device which is provided in an exhaust passage of the internal combustion engine and outputs a signal corresponding to the air-fuel ratio of the air-fuel mixture drawn into the internal combustion engine. Means and feedback-controlling the air-fuel ratio of the air-fuel mixture drawn into the internal combustion engine based on the signal from the air-fuel ratio detection means, and at least in a low load region of the internal combustion engine and other than the low load region, Learning means for learning an air-fuel ratio correction value based on the feedback value, and an air-fuel ratio correction value at a predetermined time learned by the learning means, at least for a low load region of the internal combustion engine and other than the low load region. Air-fuel ratio correction value storage means for storing, an air-fuel ratio correction value in a low load region learned at a time distant from the predetermined time and an air-fuel ratio correction value other than the low load region and the stored An exhaust gas leakage determination means for comparing the difference with the air-fuel ratio correction value in each corresponding region, and determining that an exhaust gas leak exists when the deviation of the air-fuel ratio correction value in the low load region is larger. That is the summary.

Further, the internal combustion engine abnormality notification device of the present invention includes such an internal combustion engine abnormality determination device. Further, when the internal combustion engine abnormality determination device determines that exhaust gas leakage is present, the determination result is output to the driver. The gist is to provide an informing means for informing.

[0008]

In the abnormality determining apparatus for the internal combustion engine according to the first aspect of the present invention configured as described above, the air-fuel ratio detecting means provided in the exhaust passage of the internal combustion engine detects the air-fuel ratio of the air-fuel mixture drawn into the internal combustion engine. A corresponding signal is output, and based on this signal, the learning means feedback-controls the air-fuel ratio of the air-fuel mixture sucked into the internal combustion engine, and at the same time, feedback is performed at least in the low load region of the internal combustion engine and outside the low load region. Each of the air-fuel ratio correction values is learned based on the value.

When there is a leak in the exhaust system, fresh air is sucked from the location of the exhaust leak due to fluctuations in the exhaust pipe pressure in synchronism with the rotation of the internal combustion engine, but the internal combustion engine is in a low load region such as in an idle operation state. When operated at, the air-fuel ratio detection means is affected by this fresh air sucked into the exhaust system, and the detection state is the same as when the air-fuel ratio of the air-fuel mixture is large. As a result, the learning of the air-fuel ratio correction value deviates toward the value when the air-fuel ratio of the air-fuel mixture is large. On the other hand, when the operating state of the internal combustion engine is not in the low load region but is operating in the acceleration region or the like, the suction frequency (pulsation cycle) is high even when fresh air is sucked in from the location of exhaust leakage, Due to the limit of the responsiveness of the system that controls the air-fuel ratio based on the output signal of the air-fuel ratio detection means, the learning of the air-fuel ratio correction means has a relatively small influence of the intake of fresh air from the exhaust leakage point. Stay on the thing.

Therefore, utilizing the result of this learning, the learned air-fuel ratio correction value in the low load region is a value corresponding to the case where the air-fuel ratio of the air-fuel mixture is large, and the learned low value. If it is determined that the air-fuel ratio of the air-fuel mixture is larger than the air-fuel ratio correction value outside the load region, it can be determined that exhaust gas leakage exists.

Further, in the abnormality determining device for the second internal combustion engine of the present invention, the learning control of the air-fuel ratio detecting means and the learning means is the same as in the abnormality determining device for the first internal combustion engine, and the learned value is used. The judgment method used was different. That is, the air-fuel ratio correction value at the learned predetermined time point, the air-fuel ratio correction value storage means stores at least the low load region of the internal combustion engine and other than this low load region, the exhaust leakage determination means,
The air-fuel ratio correction value in the low load region learned at a time point apart from the predetermined time point and the air-fuel ratio correction value other than the low load region, and the air-fuel ratio correction in each corresponding region stored by the air-fuel ratio correction value storage means. The difference with the value is compared, and when the deviation of the air-fuel ratio correction value in the low load region is larger, it is determined that exhaust gas leakage exists.

The reason why such a method is adopted is as follows. When an exhaust gas leak occurs, the learned value is compared to the learned value when it is confirmed that there is no exhaust gas leakage.
It shifts. On the other hand, the deviation of the learning value also occurs due to the change with time of the air-fuel ratio detecting means and the like. The latter is a deviation that does not depend on the difference in the operating region of the internal combustion engine, whereas the former (deviation due to exhaust gas leakage) is a difference that differs due to the difference in the operating region of the internal combustion engine. That is, when the internal combustion engine is operating in the low load region, the deviation is large, and when operating outside the low load region (for example, in the acceleration region), the deviation is small. Therefore, by comparing these, it becomes possible to accurately detect the exhaust gas leakage.

Here, the exhaust gas leakage determination means of the first and second inventions is provided with an execution command means which is executed when a specific diagnostic command is input to a diagnostic device for diagnosing the control system of the internal combustion engine. It is also possible to do so. It is also desirable to set the low load region as the idle region of the internal combustion engine and the region other than the low load region as the acceleration region in order to facilitate the determination.

Further, as the air-fuel ratio detecting means, a sensor for outputting a signal for reversing the state where the air-fuel mixture is in the stoichiometric state as a threshold value is adopted, and as the learning means, the fuel for the intake air amount until the output signal of the sensor is reversed. A means for repeating the process of increasing / decreasing the amount by a predetermined amount, and a deviation learning means for learning the deviation of the average value of the values corresponding to the increased / decreased fuel amount from the standard value as the learning value of the air-fuel ratio correction value are provided. It is also preferable to have a configuration. Needless to say, a sensor that outputs a signal proportional to the air-fuel ratio may be used.

When such an exhaust leakage of the internal combustion engine is detected, the abnormality informing means notifies the driver of this, so that the occurrence of the exhaust leakage can be dealt with promptly. The driver may be informed by lighting a lamp or ringing a buzzer, or in some cases, by giving a warning when the internal combustion engine is started or by prohibiting the internal combustion engine from starting.

[0016]

Preferred embodiments of the present invention will be described below in order to further clarify the structure and operation of the present invention described above. FIG. 1 is a schematic configuration diagram showing an air-fuel ratio control device incorporating an above-described determination device for an internal combustion engine, which is an embodiment of the present invention, together with an automobile engine 1 and its peripheral devices.

The intake system of the engine 1 is, in order from the upstream,
Air cleaner 2, throttle body 3, surge tank 4
And an intake pipe 5 is provided, and finally connected to an intake port of the engine body 6. The air-fuel mixture introduced from the intake system to the combustion chamber 8 via the intake valve 7 is explosively burned by spark ignition, and then discharged to the exhaust pipe 10 via the exhaust valve 9 and purified by the catalytic converter 11. , Emitted into the atmosphere.

The engine 1 is controlled by the electronic control unit 14.
It is subjected to various controls such as air-fuel ratio control. The electronic control unit 14 receives signals from various sensors for control. As these sensors, an intake air temperature sensor 15 for detecting the intake air temperature THA, an intake pressure sensor 16 for detecting the intake pipe negative pressure, a throttle position sensor 18 for detecting the opening of a throttle valve 17 of the throttle body 3, an engine 1 Water temperature sensor 1 for detecting the temperature THW of the cooling water
9, a rotation speed sensor 21 provided in the distributor 20, and an air-fuel ratio (oxygen concentration) sensor 22 attached to the exhaust pipe 10.

The air-fuel ratio sensor 22 is a sensor in which the output voltage changes in a binary manner depending on the amount of oxygen remaining in the exhaust gas, and the output voltage V1 is the point at which the air-fuel ratio of the air-fuel mixture becomes the stoichiometric air-fuel ratio. At the boundary, the value becomes lower than the determination value VR1 in the lean state and becomes higher than the determination value VR1 in the rich state. The electronic control unit 14 controls the opening and closing of the fuel injection valve 24 mounted toward the combustion chamber 8 in the vicinity of the intake port based on the information from these sensors.

Further, the intake system is provided with a bypass passage 25 that bypasses the throttle valve 17, and connects the upstream side of the throttle valve 17 and the surge tank 4. This bypass passage 25
An on-off valve 26 is provided in the. The on-off valve 26 is connected to a fast idle control device 27, and the fast idle control device 27 has an ignition switch 27.
In response to the input signal from a, the bypass passage 25 is opened at the time of idling when the engine 1 is at a low temperature, the intake air flow rate is increased, and so-called first idle is achieved. Further, the ignition switch 27a of the fuel injection valve 28 for cold start is turned on, and the water temperature switch 29 turns the engine 1 on.
When it is detected that the engine is starting at a low temperature, the fuel as the increased amount is supplied into the surge tank 4 to make the starting smooth.

The fuel injection valve 24 is provided corresponding to each cylinder of the engine 1, and is connected to a common distribution pipe 30 for supplying fuel. The distribution pipe 30 is connected to the fuel tank 33 via a fuel passage 31 and a return passage 32. A fuel filter 34, a fuel pump 35, and a fuel damper 36 are provided in the fuel passage 31 in order from the side closer to the fuel tank 33, and a pressure control valve 37 is provided in the return passage 32.
Is provided. The pressure control valve 37 controls the pressure of the fuel in the distribution pipe 30, and the target value of the pressure control is via the pressure of a spring (not shown) provided in the secondary pressure chamber and the fuel pressure control valve 38. And the air pressure introduced into the secondary pressure chamber of the pressure control valve 37.

Next, the structure and function of the electronic control unit 14 will be described. As shown in FIG. 2, the electronic control unit 14
Is configured as a logical operation circuit centered on a microcomputer, and more specifically, it is necessary for the CPU 70a and the CPU 70a that execute various kinds of arithmetic processing for controlling the engine 1 according to a preset control program to execute various kinds of arithmetic processing. A ROM 70b that stores a control program, control data, and the like in advance, and a RAM that similarly reads and writes various data necessary for the CPU 70a to execute various arithmetic processes.
70c, A / to which the detection signal of each sensor described above is input
D converter 70d, input processing circuit 70e, CPU
An output processing circuit 70f for outputting a drive signal to the igniter 41, the fuel injection valve 24, the fuel pressure control valve 38, etc. according to the calculation result of 70a is provided. Further, the electronic control unit 14 includes a power supply circuit 70g connected to the battery 88, and the power supply circuit 70g receives supply of power necessary for the entire device.

An intake air temperature sensor 15, an intake air pressure sensor 16, a throttle position sensor 18 and a water temperature sensor 19 are connected to the A / D converter 70d, and the CPU 70a.
Therefore, the output values of these sensors can be read as analog signals. Further, the input processing circuit 70e is connected with a rotation speed sensor 21, an air-fuel ratio sensor 22, and an idle switch 80 built in the throttle position sensor 18 as a sensor for detecting the operating state of the engine 1, and the same. The CPU 70a can read the states of these sensors and switches as binary signals.

Various processes executed by the electronic control unit 14 will be sequentially described. The electronic control unit 14 calculates the amount of fuel to be injected into the intake port by the fuel injection valve 24 by a fuel injection control routine executed every predetermined crank angle, for example, every 360 ° CA, and controls the fuel injection valve 24. Execute the process. This process is shown in the flowchart of FIG. When calculating the actual fuel injection amount TAU in this fuel injection control routine, the actual fuel injection amount TAU is calculated using the air-fuel ratio correction coefficient FAF so that the air-fuel ratio of the air-fuel mixture becomes approximately stoichiometric. This air-fuel ratio correction coefficient F
AF is a coefficient determined from the lean / rich state of the air-fuel mixture detected by the air-fuel ratio sensor 22. The air-fuel ratio correction coefficient FAF is gradually increased by the integral operation until the output of the air-fuel ratio sensor 22 reaches a value (V1> VR1) corresponding to the rich state of the air-fuel mixture, and after the rich state, a value corresponding to the lean state. It is gradually reduced by the integral operation until (V1 ≦ VR1). This process is shown in the flowcharts of FIGS.

First, the fuel injection control processing routine executed by the CPU 70a of the ECU 70 will be described with reference to FIG. When the processing is started, the CPU 70a
First, a process of reading the intake pipe negative pressure P stored in the RAM 70c is executed (step S400). Intake pipe negative pressure P
Is determined by another routine not shown in the drawing.
The signal from is converted into a value by A / D conversion by the converter 70d and is stored as the latest data in a predetermined address of the RAM 70c. Next, the engine speed N
Similarly, a process of reading e from the RAM 70c is executed (step S410). As for the rotation speed Ne, the output signal from the rotation speed sensor 21 is read through the input processing circuit 70e so that the RAM can be read by another routine (not shown).
The latest value is stored in a predetermined address of 70c.

Subsequently, the basic fuel injection amount TP is calculated according to the following equation (1) using the intake pipe negative pressure P and the rotational speed Ne read in steps S400 and 410 (step S420). TP ← f (P, Ne) (1)

The actual fuel injection amount TAU is calculated by multiplying the basic fuel injection amount TP thus obtained by various correction coefficients according to the following equation (2) (step S430). TAU ← TP / FAF / KG / FWL / FFC / a / b ... (2)

FAF is an air-fuel ratio correction coefficient,
It is calculated by an air-fuel ratio feedback control processing routine described later. KG is an air-fuel ratio learning value, which is a value learned by a learning control processing routine described later. The air-fuel ratio learning value is learned in each of seven areas divided based on the operating area of the engine 1. In actual calculation, from the learning value KG1 learned in the area having the smallest load, the maximum load area is obtained. Learning values up to the learning value KG7 learned in (WOT area) are used. Therefore, as the learned value KG in the above equation (2), a value KGn that is different for each operating region n of the engine 1 is actually used. FWL is a warm-up increase correction coefficient and takes a value of 1.0 or more while the cooling water temperature THW is 60 ° C. or less. FFC is a correction coefficient at the time of fuel cut, and normally has a value of 1 and has a value of 0 at the time of fuel cut. a and b are other correction factors, such as intake air temperature correction, transient correction,
The correction coefficient related to the power supply voltage correction, etc. is applicable.

When the actual fuel injection amount TAU is calculated in step S430, subsequently, the fuel injection time corresponding to the actual fuel injection amount TAU is set in a counter (not shown) that determines the valve opening time of the fuel injection valve 24 ( Step S44
0), exit to "return" and end the processing. By setting a value in the counter of the circuit that executes fuel injection, the fuel injection valve 24 is opened when a predetermined crank angle is reached, and the fuel injection valve 24 is opened for the valve opening time set in this counter. The valve state is established and a desired amount of fuel is injected.

Next, an air-fuel ratio feedback (hereinafter, feedback will be referred to as F / B) control routine executed by the CPU 70a of the electronic control unit 14 will be described with reference to FIG.
A description will be given based on FIG. Since FIG. 4 and FIG. 5 show the same processing routine in a divided manner, even in the case where the processing covers both figures in the following description, only step S and the number are shown and the instruction of the figure number is omitted. This air-fuel ratio F / B processing routine is interrupted for a predetermined time, for example, 4 msec.
It is executed every time.

When this routine is started, first in step S501, it is determined whether or not the F / B condition is satisfied. For example, the F / B condition is not satisfied when the cooling water temperature THW is equal to or lower than a predetermined value, during engine startup, during startup increase, during warmup increase, or during power increase.
In other cases, the F / B condition is satisfied. When the F / B condition is not satisfied, the routine proceeds to step S500, the air-fuel ratio correction coefficient FAF is set to the value 1, and this routine is once terminated as it is. On the other hand, if the F / B condition is satisfied, step S50.
Go to 2.

In step S502, the air-fuel ratio sensor 22
Output voltage V1 of the A
At 503, the output voltage V1 is the comparison voltage VR1, for example, 0.
It is determined whether it is 45 V or less. That is, if the air-fuel ratio is lean (V1 ≦ VR1), it is determined in step S504 whether the delay counter CDLY is negative, and CDLY>
If it is 0, CDLY is set to 0 in step S505, and the process proceeds to step S506. In step S506, the delay counter CDLY is decremented by 1, and steps S507, 5
At 08, the delay counter CDLY is guarded by the minimum value TDL. In this case, when the delay counter CDLY reaches the minimum value TDL, the air-fuel ratio flag F1 is set to the value 0 (lean) in step S509. The minimum value T
DL is a lean delay time for holding the determination that the state is rich even if there is a change from rich to lean in the output of the air-fuel ratio sensor 22, and is defined as a negative value. On the other hand, if rich (V1> VR1), it is determined in step S510 whether or not the delay counter CDLY is positive, and if CDLY <0, CD is calculated in step S511.
LY is set to the value 0, and the process proceeds to step S512.

In step S512, the delay counter C
DLY is incremented by 1, and the delay counter CDLY is guarded by the maximum value TDR in steps S513 and 514. In this case, when the delay counter CDLY reaches the maximum value TDR, the air-fuel ratio flag F1 is determined in step S515.
Is set to 1 (rich). It should be noted that the maximum value TDR is a rich delay time for holding the determination that the output is the lean state even if the output of the air-fuel ratio sensor 22 changes from lean to rich, and is defined by a positive value. Lean / rich signal from the air-fuel ratio sensor 22 and counter CDL
FIG. 6A shows the relationship between the value of Y and the air-fuel ratio flag F1.
Shown in (B) and (C).

In step S516, the air-fuel ratio flag F1
It is determined whether or not the sign of is inverted, that is, whether or not the air-fuel ratio after the delay processing is inverted. If the air-fuel ratio has been reversed, then in step S517 the air-fuel ratio flag F1
Depending on the value of, it is determined whether the inversion from rich to lean or the inversion of lean to rich.

If it is the reverse from rich to lean, in step S518, FAF ← FAF + RSR (3) is calculated to increase the air-fuel ratio correction coefficient FAF in a skip manner, and conversely, from lean to rich. If it is an inversion, the calculation of FAF ← FAF-RSL (4) is performed in step S519 to decrease the air-fuel ratio correction coefficient FAF in a skip manner. As a result, the air-fuel ratio is subjected to so-called skip processing, and as shown in FIG. 6D, the air-fuel ratio flag F
Every time 1 is inverted, the skip amounts RSR and RSL are increased or decreased.

On the other hand, if the sign of the air-fuel ratio flag F1 is not inverted in step S516, step S520,
Integration processing is performed at 521 and 522. That is, in step S520, it is determined whether or not F1 = “0”, and F1 =
If "0" (lean), in step S521, FAF ← FAF + KIR (5) is calculated to gradually increase the air-fuel ratio correction coefficient FAF. On the other hand, if F1 = "1" (rich), step S
At 522, FAF ← FAF-KIL (6) is calculated to gradually reduce the air-fuel ratio correction coefficient FAF.

Here, the integration constants KIR and KIL are set sufficiently smaller than the skip amounts RSR and RSL,
That is, KIR (KIL) <RSR (RSL).
Therefore, step S521 is in the lean state (F1 =
The fuel injection amount is gradually increased by "0"), and step S5
22 is a rich state (F1 = “1”) and gradually reduces the fuel injection amount. Steps S518, 519, 521, 5
The air-fuel ratio correction coefficient FAF calculated in step 22 is guarded in steps S523 and 524 with a minimum value, for example 0.8, and is guarded with steps S525 and 526 in a maximum value, for example 1.2. . Thus, when the air-fuel ratio correction coefficient FAF becomes too large or too small for some reason, the air-fuel ratio of the engine is controlled by the value to prevent overrich or over lean. The FAF calculated as described above is stored in the RAM 70c, and this routine ends in step S527.

As described above, by using the air-fuel ratio control routine described with reference to FIGS. 4 and 5, while using the air-fuel ratio sensor 22 in which the output voltage changes in a binary manner across the point where the air-fuel ratio is stoichiometric, It is possible to control the intake mixture of No. 1 in a stoichiometric state. Moreover, since the delay counter is used, the air-fuel ratio is not sensitively controlled by a transient change in the air-fuel ratio.

Next, the air-fuel ratio correction value learning processing routine executed by the CPU 70a of the ECU 70 will be described with reference to FIG.
It will be described based on. This learning routine is shown in FIGS.
In the air-fuel ratio control described with reference to step S518, the air-fuel ratio correction coefficient FAF is skipped every time (steps S518, 51).
9) is executed. When this learning routine is started,
First, a process for obtaining the average value FAFAV of the air-fuel ratio correction coefficient FAF is performed (step S600). This is obtained by calculating the addition average of the value FAF0 in which the air-fuel ratio correction coefficient FAF immediately after the previous skip is stored and the current air-fuel ratio correction coefficient FAF. Next, the stored value FAF
0 is set as the air-fuel ratio correction coefficient FAF immediately after this skip
Is stored (step S601).

Next, it is determined to which load region n the current operating state of the engine 1 belongs (step S60).
2). This determination is based on the engine speed Ne of the engine 1, the current intake pipe negative pressure P, or the throttle position sensor 18
It is determined from the opening degree of the. The idle state with the smallest load is set to n = 1, and the throttle position sensor 18 full acceleration state (WOT) with the largest load is set to n = 7.
It is determined which of the seven areas the whole belongs to.

After that, the average value F of the air-fuel ratio correction coefficient FAF
A deviation ΔFAF from the AFAV reference value 1.0 is calculated (step S603), and then it is determined whether or not the deviation ΔFAF is larger than zero (step S604).
Here, the magnitude of the deviation of the average value FAFAV of the air-fuel ratio correction coefficient FAF from the reference value 1.0 is determined, and step S60 is performed.
The processing of 5 or less is performed when the average value FAFAV of the air-fuel ratio correction coefficient FAF, which should be 1.0 when the stoichiometric control is originally performed, deviates from the reference value 1.0.
It is determined that the entire feedback control of the air-fuel ratio is shifted due to changes in the characteristics of the air-fuel ratio sensor 22 and the fuel injection valve 24 over time. Therefore, by learning this, the average value of the air-fuel ratio correction coefficient FAF is learned. This is because FAFAV is controlled to be as close to the reference value 1.0 as possible.

Therefore, if the deviation ΔFAF is larger than the value 0 (step S604), the learning value KGn in the operating region n of the engine 1 is increased by the unit learning amount ΔKGn (step S605), and this learning value KGn is guarded. Value 1.15
Guard processing is performed in step S606, S60.
7). On the other hand, if the deviation ΔFAF is 0 or less (step S604), the learning value KGn of the operating region n of the engine 1
By the unit learning amount ΔKGn (step S60
8) Further, the learning value KGn is guarded with a guard value of 0.85 (steps S609 and 610). By the above processing, the air-fuel ratio correction coefficient FAF becomes the reference value 1.0.
Even if there is a factor that causes deviation, the deviation is learned to the learning value KGn, and learning control is performed so that the average value of the air-fuel ratio correction coefficient FAF always converges near the reference value 1.0.

On the premise of the fuel injection amount control, the air-fuel ratio control, and the learning control as described above, an abnormality determining device as an embodiment of the present invention is realized. That is, the abnormality determination device is realized by the electronic control device 14 executing the process shown in FIG. 8, detects exhaust leakage, and notifies the abnormality.
Therefore, the processing of FIG. 8 will be described below.

When the abnormality determination routine shown in FIG. 8 is started, it is first determined whether the cooling water temperature THW is 80 ° C., that is, the warm-up is completely completed and the conditions for learning control of the air-fuel ratio are satisfied. (Step S100), the cooling water temperature THW is 8
If it is 0 ° C. or higher, it is next determined whether or not the T terminal is turned on (step S110). The “T terminal” is a terminal prepared to allow the electronic control unit 14 to verify the normal operation of the device. By setting this terminal to a predetermined voltage level (ON state), the electronic control unit 14 is As a part of the diagnosis function, the following processing prepared in advance is executed.

When the T terminal is on, the output of the throttle position sensor 18 is read next,
Signal SPD from throttle position sensor 18 =
0, that is, it is determined whether or not it is in the idle state (step S120). Throttle position sensor 1
8 is equipped with an idle switch 80,
It may be determined that the idle state is the idle state depending on the idle state of the idle switch 80. The above three steps S100,
If the determinations at 110 and 120 are all "NO", nothing is done and the process goes to "END" to end this routine.
If all the conditions are satisfied, it is assumed that exhaust gas leakage can be detected, and the engine 1 is operated in the idle state until 40 seconds have elapsed (step S13).
0). When 40 seconds have elapsed, the learning value KG1 in the idle state of the air-fuel ratio correction value learned during this period is 1.0 + α.
It is determined whether or not the above (step S14).
0). The learning value KG1 is learned by the learning processing routine of FIG. 7 described above. However, when exhaust gas leakage exists, fresh air is sucked in due to pressure fluctuations in the exhaust pipe 10,
This is detected by the air-fuel ratio sensor 22 provided downstream of the catalytic converter as excess air in the air-fuel mixture,
It is reflected in the learning value KG. In this case, the learning value KG becomes a large value so as to increase the fuel amount and eliminate the excess air after the learning is performed so that the average value AV of the air-fuel ratio correction coefficient FAF becomes 1.0.

The learning value KG1 in the idle state, which is actually learned in the presence of exhaust gas leakage, is shown as a broken line B in FIG. In the figure, the solid line J indicates the learning value K when there is no exhaust leakage.
G is shown. Therefore, if it is determined that KG1 is equal to or more than the value 1.0 + α, it is determined that there is a possibility of exhaust gas leakage, and the process of setting the value 1 to the exhaust gas leakage flag FE is performed (step S150). Here, the reason why the exhaust leakage is not immediately determined based only on the determination in step S140 is that the learning value KG1 may exceed the value 1.0 and shift to the positive side even if the characteristics of the engine 1 and the air-fuel ratio sensor 22 change. This is because.

Therefore, after the learning result of the learning value KG1 in the idle state is determined in this way, it is confirmed that the inspector has turned off the T terminal (step S160), and an actual running test is performed (step S170). The running test may be a normal 10-mode running test including acceleration and steady running. When the running test is performed, the engine 1 is operated under various load conditions such as the acceleration region, and the air-fuel ratio correction coefficient F
The learning values KG2 to KG7 in each area are learned based on the feedback control of AF. Therefore, after the running test, for the learning values KG3 and KG4, ΔKG3 + Δ
It is determined whether KG4 is smaller than the predetermined value β (step S180). ΔKG3 and ΔKG4 are deviations of the learning values KG3 and KG4 in the acceleration region from the value 1.0.
The predetermined value β is a value that is considerably smaller than the determination value α used in the determination in step S140. Therefore, the learning value KG1 in the idle region is
Indicates a value when the air-fuel ratio is a large value (air-fuel mixture is in excess of air), and learning values KG3 and KG4 in the acceleration region indicate values when the air-fuel ratio is stoichiometric. First, it is determined that a leak has occurred in the exhaust system, and a process of turning on the corresponding lamp of the instrument panel is performed (step S190).

As shown in FIG. 9, the learning values KG3, KG in the acceleration region do not increase like the learning value KG1 in the idle region even when exhaust gas leaks. This is because the pressure of the exhaust pipe 10 fluctuates quickly, the suction frequency (pulsation cycle) of fresh air is high, and the response speed of the air-fuel ratio sensor 22 is low, so it is difficult to detect the change. . As shown in FIGS. 4 and 5, in the feedback control of the air-fuel ratio correction coefficient FAF, the maximum value TDR and the minimum value T for accurately determining the rich state and the lean state are used.
Since there is a delay time using DL, these values TD
Even if the oxygen concentration around the air-fuel ratio sensor 22 changes in a cycle shorter than the time corresponding to R and TDL, the air-fuel ratio sensor 2
2 cannot detect this. In fact, as shown in FIG. 9, the learning values KG3, KG4 in the acceleration region become smaller as the load becomes larger, even if exhaust gas leakage exists (broken line B), from the value 1.0. There is. Therefore, the learning value KG1 in the idle state is larger than the value 1.0 by the judgment value α, and the learning values KG3 and KG in the acceleration region are
When it is determined that 4 is a value near the value 1.0, the exhaust leakage is determined.

On the other hand, when the feedback control of the air-fuel ratio correction coefficient FAF is affected by changes in the characteristics of the engine 1 and the air-fuel ratio sensor 22, the engine 1
The influence is reflected in the learning value KG regardless of the driving range. Therefore, in this case, even if the learning value KG1 in the idle state exceeds the value 1.0 by the judgment value α, the learning values KG3 and KG4 in the acceleration region also greatly exceed the value 1. Therefore, in this case, it is not judged that the exhaust gas leaks.

By making the above determination, it is possible to detect the occurrence of exhaust gas leakage with high accuracy. Further, based on a signal from the air-fuel ratio sensor 22 that does not accurately reflect the air-fuel ratio of the air-fuel mixture in an idle state or the like, the engine 1 is operated for a long period of time, and not only emission deterioration but also fuel consumption deterioration and engine stall There is no occurrence of a defective operating condition such as occurrence of.

It is understood that various methods can be used to detect the exhaust gas leak on the assumption of the behavior of the learning value which is different for each load region of the engine 1 described above. For example, as shown in FIG. 10, instead of step S180 of the first embodiment, the learning value KG1 in the idle region is larger than the value 1.0 + κ (step S182), and the deviation between the learning values KG3 and KG4 in the acceleration region. When the absolute value of is less than the predetermined value γ (step S184), it is possible to determine that the exhaust gas is leaking and turn on the lamp.

Next, a second embodiment of the present invention will be described. The abnormality determination device according to the second embodiment is incorporated in the air-fuel ratio control device for the engine 1 according to the first embodiment, and determines exhaust leakage by a learning value KG using feedback control of the air-fuel ratio correction coefficient FAF. The points are the same as in the first embodiment. In this embodiment, when the engine 1 is first operated for a predetermined time and then stopped, at the end of the operation,
The end-time processing routine shown in FIG. 11 is executed, and the learning value KG1 in the idle region learned up to that point is set as the maintenance learning value KG.
11 (step S200), and similarly the learning values KG3, KG4 in the acceleration region are maintained learning values KG33, KG44.
Is performed (steps S210, 22).
0). The maintenance learning values KG11, KG33, KG44 are not lost because they are stored in a memory backed up by a battery (not shown) or a non-volatile memory such as a flash RAM.

Next, when the ignition switch 27a is turned on and the engine 1 is started, the electronic control unit 14 executes the abnormality determination processing routine shown in FIG. 12 at a predetermined interval. When this routine is started, first the cooling water temperature THW
Is 80 ° C. or higher, that is, it is determined whether or not the warm-up is completed (step S300), and then the learning value KG after the completion of warm-up
The absolute value of the deviation between 1 and the maintenance learning value KG11 is the judgment value α.
It is determined whether or not this is the case (step S310). When the learning value KG1 at the present time is significantly different from the maintenance learning value KG11 in which the previous value of the learning value KG1 in the idle region is stored, it is determined that there is a possibility of exhaust gas leakage.

Therefore, when this condition (step S310) is satisfied, the learning value KG in the current idle region
It is determined whether 1 is greater than the value 1.0 (step S320), and if all of these conditions are satisfied (steps S300, 310, 320), it is determined that exhaust gas leakage may occur. Yes (step S330). Actually, the exhaust leakage flag FE is set. Next, regarding the learning values KG3 and KG4 in the acceleration region, the corresponding maintenance learning value K
It is determined whether or not the absolute values of the deviations from G33 and KG44 are less than predetermined values δ and ε, respectively (step S3).
40, 350). Even if exhaust gas leakage occurs, the learning values KG3, KG4 in the acceleration region do not change so much. Therefore, if it is an acceleration leakage, both determinations in steps S340 and 350 are “YES”. Therefore, in this case, it is further determined whether the same determination is made twice by traveling for a certain period of time (step S360), and if it is determined that the same determination has been made for two trips, it is determined that exhaust gas has leaked. To turn on the lamp (step S370).

On the other hand, when the learning value KG1 in the idle region changes greatly due to the change in the characteristics of the engine 1 and the air-fuel ratio sensor 22, the learning values KG3, KG in the acceleration region.
Since 4 also changes in the same manner, either of the determinations in steps S340 and 350 becomes "NO", and the determination of exhaust gas leakage cannot be made.

According to the abnormality determining apparatus of the second embodiment having the above-mentioned configuration, the previous learning values KG, KG3, KG4
And the like are stored in a non-volatile memory, and the exhaust leakage is judged by using the magnitude of the deviation between this and the current learning values KG1, KG3, KG4. Therefore, not only when the T terminal of the diagnosis is turned on as in the first embodiment, it is possible to always judge the exhaust leakage. Moreover, since the value when the engine 1 was operated last time is memorized and the exhaust leakage is judged by comparison with this value, when a crack or the like occurs in the exhaust pipe 10 during operation, the vehicle is stopped immediately after that. If it does occur, there is the advantage that the presence of an exhaust leak can be detected accurately at an early point in the next run.

A modification of the second embodiment is shown in FIG. In this embodiment, it is the same that the learning value is stored as the maintenance learning value at the end of the operation (FIG. 11). In the abnormality determination processing routine shown in FIG. 13, after the completion of warming up and the determination that the learning value in the idle region is larger than 1.0 (steps S300 to 320), the current learning value KG1 in each operating region is determined. Deviations X1, X3, X4 between KG3, KG4 and the corresponding maintenance learning values KG11, KG33, KG44 are obtained (steps S382, 384,
386), then, a process of obtaining a difference A between the deviation X1 and the deviation X3 (step S388) and a difference B between the deviation X1 and the deviation X4 (step S390) is performed. After that, it is determined whether or not the difference A is the first determination value α or more (step S392). If the difference A is the first determination value α or more, the difference B is further determined by the second determination. It is determined whether or not the value is β or more (step S394).

Here, the differences A and B are the judgment values α or β.
It is judged that the learning value KG1 in the idle region changes with time in the acceleration region.
It is detected that it is sufficiently larger than the temporal change of G3 and KG4. In this case, it can be determined that the exhaust gas has leaked, but just in case, as in the above embodiment, it is checked that the same determination can be made in two trips (step S36).
0) After that, the lamp of the instrument panel is turned on as exhaust gas leakage (step S370). These processes are the same as those in the above embodiment.

In this modification as well, as in the second embodiment, it is possible to detect the occurrence of exhaust gas leakage with high accuracy and at an early time. Therefore, it is of course possible to achieve the same effect as that of the first embodiment, such as preventing the problem of operating the engine 1 and polluting the atmosphere without noticing the exhaust gas leakage.

Although one embodiment of the present invention has been described in detail above, the present invention is not limited to such an embodiment. For example, a CO sensor, a lean mixture sensor or the like may be used as the air-fuel ratio detecting means. The configuration used, the configuration in which the operating region of the engine is simply divided into the low load region and the high load region for learning, and the maintenance learning value KG11 and the like are stored at the time of vehicle shipment and are compared with the current learned value to cause exhaust gas leakage. The basic fuel injection amount TP is determined by the intake pipe negative pressure P and the rotation speed N.
Instead of using e, the intake air amount Q detected by an air flow meter and the number of revolutions Ne
It goes without saying that the present invention can be implemented in various modes without departing from the scope of the present invention.

[0061]

As described above, in the first abnormality determination system for an internal combustion engine of the present invention, the air-fuel ratio of the air-fuel mixture sucked into the internal combustion engine is feedback-controlled, and at least the low load region of the internal combustion engine and the low load region are reduced. Other than in the load region, the air-fuel ratio correction value is learned based on the feedback value, and the learned result is used to increase the learned air-fuel ratio correction value in the low-load region when the air-fuel ratio of the air-fuel mixture is large. Is a value corresponding to the case where the air-fuel ratio of the air-fuel mixture is larger than the learned air-fuel ratio correction value in a region other than the low load region, and the exhaust leakage is detected. to decide. Therefore, the presence of exhaust gas leakage can be accurately detected without being affected by the aging of the air-fuel ratio detecting means.

Further, in the second abnormality determining apparatus for the internal combustion engine of the present invention, the learned air-fuel ratio correction value at the predetermined time point is stored at least in the low load region of the internal combustion engine and in the region other than this low load region. When the difference between the air-fuel ratio correction value in the low load region and the air-fuel ratio correction value other than the low load region learned at the time of separation is compared, and the deviation of the air-fuel ratio correction value in the low load region is larger, It is determined that there is an exhaust gas leak. Therefore, the abnormality determination device can also accurately detect the presence of exhaust gas leakage without being affected by the change over time of the air-fuel ratio detecting means.

As a result, any of the abnormality judging devices can detect the occurrence of exhaust gas leakage with high accuracy, and the results of these abnormality judging devices are used to inform the driver of the existence of exhaust gas leakage. According to the abnormality notification device of the invention, it is possible to prevent the problem that the operation of the engine 1 is continued without noticing the exhaust gas leakage. Also,
Based on a signal from the air-fuel ratio detection means that does not accurately reflect the air-fuel ratio of the air-fuel mixture in the low load region, the internal combustion engine is operated for a long period of time, and not only emission deterioration but also fuel consumption deterioration and engine stall occur. It does not cause a poor operating condition.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing a configuration of an air-fuel ratio control device incorporating an abnormality determination device as an embodiment of the present invention together with an engine 1 and peripheral devices thereof.

FIG. 2 is a block diagram showing an electrical configuration of a control system centered on an electronic control device 14.

FIG. 3 is a flowchart showing a fuel injection control processing routine executed by an electronic control unit 14.

FIG. 4 is a flowchart showing a part of an air-fuel ratio feedback control routine in the embodiment.

FIG. 5 is a flowchart showing the same remainder.

FIG. 6 is a graph showing how the air-fuel ratio correction coefficient FAF is controlled.

FIG. 7 is a flowchart showing a learning processing routine executed by the electronic control unit 14.

FIG. 8 is a flowchart showing an abnormality determination processing routine in the first embodiment.

FIG. 9 is a graph exemplifying how the learned value changes in each operating region.

FIG. 10 is a flowchart showing a modification of the abnormality determination processing routine in the first embodiment.

FIG. 11 is a flowchart showing an end processing routine for maintaining a learned value in the second embodiment.

FIG. 12 is a flowchart showing an abnormality determination processing routine in the second embodiment.

FIG. 13 is a flowchart showing a modification of the second embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Engine 2 ... Air cleaner 3 ... Throttle body 4 ... Surge tank 5 ... Intake pipe 6 ... Engine body 7 ... Intake valve 8 ... Combustion chamber 9 ... Exhaust valve 10 ... Exhaust pipe 11 ... Catalytic converter 14 ... Electronic control unit 15 ... Intake Air temperature sensor 16 ... Intake pressure sensor 17 ... Throttle valve 18 ... Throttle position sensor 19 ... Water temperature sensor 20 ... Distributor 21 ... Rotation speed sensor 22 ... Air-fuel ratio sensor 24 ... Fuel injection valve 25 ... Bypass passage 26 ... Open / close valve 27 ... First idle Control device 27a ... Ignition switch 28 ... Low temperature start fuel injection valve 29 ... Water temperature switch 30 ... Distribution pipe 31 ... Fuel passage 32 ... Passage 33 ... Fuel tank 34 ... Fuel filter 35 ... Fuel pump 36 ... Fuel damper 37 ... Pressure control valve 38 ... Fuel pressure control valve 41 ... Igniter 70 ... ECU 70 ... CPU 70b ... ROM 70c ... RAM 70d ... A / D converter 70e ... Input processing circuit 70f ... Output processing circuit 70g ... Power supply circuit 80 ... Idle switch 88 ... Battery CDLY ... Delay counter FE ... Exhaust leakage flag F1 ... Air-fuel ratio flag FAF ... Air-fuel ratio correction coefficient KGn ... Learning value KIR, KIL ... Integration constant Ne ... Rotation speed P ... Intake pipe negative pressure RSR, RSL ... Skip amount TAU ... Actual fuel injection amount THW ... Cooling water temperature TP ... Basic fuel injection amount

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location G01M 15/00 Z

Claims (6)

[Claims] 1. An air-fuel ratio detecting means which is provided in an exhaust passage of an internal combustion engine and outputs a signal corresponding to an air-fuel ratio of an air-fuel mixture sucked into the internal combustion engine, and based on a signal from the air-fuel ratio detecting means. , Feedback controlling the air-fuel ratio of the air-fuel mixture sucked into the internal combustion engine, and learning an air-fuel ratio correction value based on the feedback value at least in a low load region of the internal combustion engine and other than the low load region. The learning means and the learned air-fuel ratio correction value in the low load region are values corresponding to the case where the air-fuel ratio of the air-fuel mixture is large, and the learned air-fuel ratio in a region other than the learned low load region. Than the correction value
An abnormality determination device for an internal combustion engine, comprising: an exhaust leakage determination means that determines that an exhaust leakage exists when it is determined that the air-fuel ratio of the air-fuel mixture is large. 2. An air-fuel ratio detecting means which is provided in an exhaust passage of an internal combustion engine and outputs a signal corresponding to an air-fuel ratio of an air-fuel mixture sucked into the internal combustion engine, and based on a signal from the air-fuel ratio detecting means. , Feedback controlling the air-fuel ratio of the air-fuel mixture sucked into the internal combustion engine, and learning an air-fuel ratio correction value based on the feedback value at least in a low load region of the internal combustion engine and other than the low load region. Learning means, air-fuel ratio correction value storage means for storing the air-fuel ratio correction value learned by the learning means at a predetermined time point in at least the low load region of the internal combustion engine and other than the low load region, and from the predetermined time point The difference between the air-fuel ratio correction value in the low load region learned at the time of separation and the air-fuel ratio correction value in the region other than the low load region and the stored air-fuel ratio correction value in each corresponding region is compared. On the other hand, an abnormality determination device for an internal combustion engine, comprising: an exhaust leakage determination means for determining that exhaust leakage exists when the deviation of the air-fuel ratio correction value in the low load region is larger. 3. The internal combustion engine according to claim 1, wherein the exhaust gas leakage determination means includes an execution instruction means that is executed when a specific diagnostic instruction is input to a diagnostic device that diagnoses a control system of the internal combustion engine. Anomaly judgment device. 4. The low load region is an idle region,
The abnormality determination device for an internal combustion engine according to claim 1, wherein a region other than the low load region is an acceleration region. 5. The abnormality determination device for an internal combustion engine according to claim 1, wherein the air-fuel ratio detection means is a sensor that outputs a signal that inverts a state in which the air-fuel mixture is stoichiometric as a threshold value, The learning means repeats a process of increasing / decreasing the fuel amount with respect to the intake air amount by a predetermined amount until the output signal of the sensor is reversed, and a standard value of an average value of values corresponding to the increased / decreased fuel amount. An abnormality determination device for an internal combustion engine, comprising: deviation learning means for learning a deviation as a learning value of an air-fuel ratio correction value. 6. An abnormality determination device for an internal combustion engine according to any one of claims 1 to 5, comprising means for notifying a driver of the determination result when the abnormality determination device for the internal combustion engine determines that exhaust gas leakage exists. An internal combustion engine abnormality notification device provided.