JPH0663469B2 - Engine air-fuel ratio control abnormality detection device - Google Patents

Description

The present invention relates to a device for detecting an air-fuel ratio control abnormality of an engine that controls an air-fuel ratio, based on a detection value of an air-fuel ratio sensor.

[Prior Art] Conventionally, in a device that controls an air-fuel ratio of an engine based on a detection value of an air-fuel ratio sensor, a change with time of the engine,
Air-fuel ratio control may not be performed properly due to component tolerances, malfunctions, or the like. Therefore, as shown in Toyota Technical Publication, issue date January 29, 1987, issue number 1667, the air-fuel ratio correction value calculated as a value that reflects the air-fuel ratio of the engine based on the detection value of the air-fuel ratio sensor. When,
A technique is disclosed in which a product of a learning value for converging the air-fuel ratio correction value to a reference value is calculated, and when the product becomes large, it is determined that the air-fuel ratio control is abnormal.

[Problems to be Solved by the Invention] However, in the related art, as described below, when a plurality of abnormal states overlap, an abnormality in the air-fuel ratio control may not be detected.

That is, in the technology for detecting an abnormality in the air-fuel ratio control based on the product of the air-fuel ratio correction value and the learned value, it is possible to detect only a deviation in the characteristics of the air flow meter, but this can be detected. When a change over time such as a change in the flow rate characteristic and a component tolerance are added, the both cancel each other out, and this may not be detected even though the air-fuel ratio control is abnormal.

Further, even when the product of the air-fuel ratio correction value and the learning value is not used for the determination, the air-fuel ratio correction value is converged within the predetermined swing range by the learning control, so that the above-described aging change occurs. There was also a problem that it was difficult to find.

An object of the present invention is to improve the ability to detect an abnormality in air-fuel ratio control by solving the above problems.

[Means for Solving the Problem] As means for solving the above-mentioned object, an air-fuel ratio control abnormality detecting apparatus for an engine of the present invention, as illustrated in FIG. 1, merges exhaust gases of respective cylinders of an engine MA. The air-fuel ratio sensor MB for detecting the air-fuel ratio from the portion that is being operated, the correction coefficient calculation means MC for calculating a feedback correction coefficient based on the detection value of the air-fuel ratio sensor MB, and the deviation between the feedback correction coefficient and the reference value. Learning means MD for storing as a learning value, and an air-fuel ratio control means for controlling the air-fuel ratio of the engine by correcting the amount of fuel supplied to the engine based on the calculated feedback correction coefficient and the stored learning value.
In an engine air-fuel ratio control abnormality detection device including ME, an acceleration transient state detection means MF for detecting that the engine is in a predetermined acceleration transient operation state (a state in which the throttle opening speed is a predetermined value or more), A swing width detection means MG for detecting the swing width of the feedback correction coefficient, and only during the acceleration transient operation state, if the swing width of the feedback correction coefficient is equal to or more than a predetermined value, the count value is increased by a predetermined addition value, and the shake width is If the count value is less than the predetermined value, the counting means MH decreases the predetermined subtraction value, and the air-fuel ratio abnormality determining means MI determines that the air-fuel ratio control of the engine is abnormal when the count value is equal to or more than the predetermined count value. It is characterized by being provided.

[Operation] According to the air-fuel ratio control abnormality detection device of the present invention, the feedback correction coefficient is calculated based on the air-fuel ratio detection value, and based on the feedback correction coefficient and the learning value,
The air-fuel ratio of the engine is controlled by correcting the fuel amount.

Here, this learning value is learned from the deviation between the feedback correction coefficient and the reference value, and is changed during the steady operation to store the optimum value. Therefore, in the air-fuel ratio control during steady operation, the correction by the optimum learning value is added, so that the air-fuel ratio itself is well converged to the target air-fuel ratio. As a result, the influence of abnormality of the air-fuel ratio control system component over time is slowed down, and the fluctuation range of the feedback correction coefficient is likely to be small.

However, in the acceleration transient operation state, the update of the learning value does not follow and the learning value deviates from the optimum value. Therefore, it becomes difficult for the air-fuel ratio to converge as in the steady operation, and if there is an abnormality, the fluctuation range of the feedback correction coefficient is increased as an effect thereof.

The air-fuel ratio control abnormality detecting device of the present invention detects the abnormality of the air-fuel ratio control system by utilizing such a phenomenon during the acceleration transient operation state by adopting the above-described configuration and operating as follows.

The counting means MH increases or decreases the count value according to the swing width of the feedback correction coefficient only in a predetermined acceleration transient operation state in which the update of the learned value does not follow. The condition for this increase / decrease is that the count value is increased if the fluctuation range of the feedback correction coefficient is equal to or greater than a predetermined value. Therefore, when the air-fuel ratio does not easily converge, the count value gradually increases. Then, in the air-fuel ratio abnormality determination means MI, it is detected that the air-fuel ratio does not easily converge due to the count value reaching a predetermined value or more, in other words, the influence of the abnormality of the air-fuel ratio control system is greatly expressed, and the air-fuel ratio control is performed. Was decided to be abnormal.

[Embodiment] An embodiment of the present invention will be described below in detail with reference to the drawings.

FIG. 2 shows a schematic configuration of a system to which this embodiment is applied.
A cylinder engine 10 is mainly shown.

The engine 10 is controlled by the engine controller 12. In the vicinity of the air cleaner 14 of the intake port,
An intake air temperature sensor 16 that detects the intake air temperature and outputs an intake air temperature signal, and an intake air amount sensor 18 that detects the intake air amount and outputs an intake air amount signal are provided. A throttle valve 20 is arranged on the downstream side of the air cleaner 14, and the throttle valve 20 has an idle switch 22 that is “ON” (LL “ON”) when the throttle valve is fully closed, and an opening degree of the throttle valve 20 ( A throttle sensor 24 for detecting the throttle opening) TA is attached. A surge tank 26 is formed on the downstream side of the throttle valve 20, and an intake manifold 28 and an intake port 30 are provided on the downstream side of the surge tank 26 for each cylinder. A fuel injection valve 32 that opens according to a valve opening signal from the engine controller 12 is attached to each intake port 30. Combustion chamber 34 for burning the fuel injected from each fuel injection valve 32
An exhaust manifold 36 is provided downstream of the exhaust manifold 36. An O ₂ sensor 38, which detects the residual oxygen concentration of the exhaust gas and outputs an air-fuel ratio signal, is attached to the confluence of the exhaust manifold 36, and a three-way catalyst 39 is provided downstream of this.

An engine water temperature sensor 42 that detects the cooling water temperature in the water jacket and outputs a cooling water temperature signal is attached to the engine block 40 that forms the combustion chamber 34.

The ignition plug 44 provided in the combustion chamber 34 has an igniter 46
The high voltage from is supplied via a distributor 48. The distributor 48 has an engine speed
An engine speed sensor 50 that outputs a crank angle signal for calculating NE and a cylinder discrimination sensor 52 that outputs a cylinder discrimination signal are provided.

The engine controller 12 includes an input interface 54, an output interface 55, a storage unit 56, and a central processing unit 58, and performs the processing described below.

A process of inputting a signal or the like from a sensor of each part of the engine 10 via the input interface 54.

A process of calculating various drive signals in the central processing unit 58 in accordance with various control routine programs and data stored in the storage unit 56 based on the various input signals.

A process of outputting a drive signal of each part of the engine 10 and a display signal of the air-fuel ratio control abnormality display unit 60 from the output interface 55 based on the calculation result of the central processing unit 58.

Next, based on the flowchart of the air-fuel ratio control abnormality detection routine shown in FIGS. 3 to 5, the control of this embodiment executed by the engine controller 12 every 8 ms will be described.

As shown in the air-fuel ratio control abnormality detection routine of FIG. 3, this embodiment detects the acceleration transient operating state of the engine based on the throttle opening speed ΔTA. When this routine is started, it is first judged based on the cooling water temperature information or the like whether or not the O ₂ sensor 38 is in a normally functioning state (step 100). It is determined whether or not the air-fuel ratio feedback control (F / B) based on the air-fuel ratio signal from the ₂ sensor 38 is executed by an air-fuel ratio control routine (not shown) (step 110). The air-fuel ratio control performed by the air-fuel ratio routine is
Although not shown in detail, since it is well known, the following control is performed. The fuel injection amount is calculated based on the intake air amount, engine speed, throttle opening, cooling water temperature, etc.If the air-fuel ratio signal is rich, the feedback correction coefficient FAF is decreased by a predetermined amount, while if it is lean, the FAF is decreased. The feedback correction coefficient FA
F is calculated, based on various operating conditions, it is determined whether the execution condition of the air-fuel ratio feedback control is satisfied,
If the air-fuel ratio feedback control execution condition is satisfied, the fuel injection amount obtained in
The fuel injection amount is corrected by FAF and the learning value FG calculated below, and if the feedback control condition is not satisfied, the fuel injection amount obtained in is corrected only by the learning value KG (FAF = 1). Then, fuel injection is executed. The deviation between the feedback correction coefficient FAF and the reference value (FAF = 1) is stored as the learning value FG, and the FAF is corrected with the learning value KG.

When the O ₂ sensor 38 is normal and the feedback control is performed, that is, when the execution condition for the abnormality detection of the air-fuel ratio control is satisfied, the count C1 is incremented (C1 ← C1 + 1) next. (Step 120) Then, it is determined whether or not the value of the counter C1 is a predetermined value α or more (Step 130). If the value of the counter C1 is less than the predetermined value α, that is, the execution condition of the air-fuel ratio control abnormality detection is satisfied, but if this state has not yet reached the determination time corresponding to the predetermined value α, Next, the maximum value TAmax and the minimum value TAmin of the throttle opening TA during this determination time are calculated and updated (step 140). This is the fourth
As shown in the figure, first, the throttle opening TA from the throttle sensor 24 is read (step 150), and it is determined whether or not the read throttle opening TA is less than or equal to the throttle opening TAmin calculated and updated up to the previous time. Judge (Step 1
60), if the following is true, the throttle opening TA this time is set as a new throttle opening TAmin (step 170).
As a result, the throttle opening TAmin is updated every time the throttle opening TA smaller than the previous throttle opening TAmin is read. On the other hand, the read throttle opening TA is the throttle opening TAmi calculated and updated up to the previous time.
If it is larger than n, it is next judged whether or not it is equal to or larger than the throttle opening TAmax (step 180). If it is smaller than n, this routine is once terminated, and if it is larger than this, this throttle opening TAmax is reached. Is set as a new throttle opening TAmax (step 190). As a result, the throttle opening TAmax is updated every time when the throttle opening TA larger than the previous throttle opening TAmax is read.

After updating the throttle opening degrees TAmax and TAmin, as shown in FIG. 3, the maximum value FAFmax and the minimum value FAFmin of the feedback correction coefficient FAF during the determination time are calculated and updated (step 200 ). As shown in FIG. 5, first, a feedback correction coefficient FAF is read from an air-fuel ratio control routine (not shown) (step 210), and the read feedback correction coefficient FAF is calculated and updated by the previous time. It is determined whether or not it is below (step 220), and if it is below, the current feedback correction coefficient FAF is set as a new feedback correction coefficient FAFmin (step 230). As a result, the feedback correction coefficient FAFmin is updated every time the feedback correction coefficient FAFmin is read from the previous feedback correction coefficient FAFmin. On the other hand, when the read feedback correction coefficient FAF is larger than the feedback correction coefficient FAFmin calculated and updated up to the previous time, it is next determined whether or not it is equal to or larger than the feedback correction coefficient FAFmax (step 240). If this is the case, the routine ends immediately, and if this is the case, the current feedback correction coefficient FAF is set to the new feedback correction coefficient F
Set as AFmax (step 250). As a result, the feedback correction coefficient FAFmax is updated every time the feedback correction coefficient FAF larger than the previous feedback correction coefficient FAFmax is read.

When the determination time is reached when the conditions for air-fuel ratio control abnormality detection are satisfied (step 130), based on the throttle opening TAmax, TAmin and the feedback correction coefficient FAFmax, FAFmin within the determination time, A change amount ΔTA of the throttle opening and a swing range ΔFAF of the feedback correction coefficient are calculated by the following equations (1) and (2) (step 260).

ΔTA = TAmax-TAmin (1) ΔFAF = FAFmax-FAFmin (2) After calculating ΔTA and ΔFAF above, whether or not the amount of change ΔTA in throttle opening is greater than or equal to the set value β, That is, it is determined whether or not the opening degree of the throttle valve 20 is in a large transient operation (for example, when the accelerator pedal is depressed for rapid acceleration) (step 270), and ΔTA is less than a predetermined value β. If it is during operation, it is determined that the condition for detecting the abnormality of the air-fuel ratio control is not currently satisfied, and then the throttle opening TAmax, TAmin, the feedback correction coefficients FAFmax, FAFmin, and the counter C1 are cleared. The processing to be performed is executed (step 280).

If ΔTA is greater than or equal to the predetermined value β, that is, during transient operation (step 270), then it is determined whether the swing width ΔFAF of the feedback correction coefficient is greater than or equal to the predetermined value γ (step 290). , The counter C2 is incremented (C2 ← C2 + 1) (step 300), and if less, the counter C2 is decremented (C2 ← C2-1) (step
310). As a result, during transient operation, when the fluctuation range ΔFAF of the feedback correction coefficient becomes an abnormal value that cannot occur in the normal state (for example, when it exceeds the maximum value during normal operation).
And reflect the occurrence state of the abnormal value (ΔFAF ≧ predetermined value γ) of the fluctuation range ΔFAF of the feedback correction coefficient,
The counter C2 can be increased or decreased.

As a result of the increase / decrease of the counter C2, when it is determined that the value of the counter C2 is equal to or larger than the predetermined value δ, that is, when the abnormal state of the swing width ΔFAF of the feedback correction coefficient frequently occurs (step 320 ), And then outputs a display signal to the air-fuel ratio control abnormality display section 60 to control the air-fuel ratio (A /
F) Abnormality is displayed (step 330). On the other hand, counter C
When 2 is less than the predetermined value δ, that is, when the abnormal state of the deviation width ΔFAF of the feedback correction coefficient does not occur or the occurrence frequency is low, A / F abnormality is not output and the throttle opening described above is output. The routine TAmax, TAmin, the feedback correction coefficients FAFmax, FAFmin, and the counter C1 are cleared (step 280), and this routine is once ended. As a result, if it is not abnormal, the counter C2
Other variables except for are set to the initial state, and the air-fuel ratio control abnormality detection processing is repeated again. Further, when the O ₂ sensor 38 is not in a normally functioning state (step 100) or when the air-fuel ratio feedback control by the air-fuel ratio signal from the O ₂ sensor 38 is not executed by the air-fuel ratio control routine (not shown) (Step 110) Since the condition for judging the abnormality of the air-fuel ratio control is not satisfied, the variable is set to the initial state by the step 280 described above.

As described above, according to the present embodiment, during the transient operation of the engine 10, the state in which the swing range of the feedback correction coefficient FAF is large, continuously or frequently occurs, the air-fuel ratio control is abnormal. It is judged that it has occurred, and an alarm is issued. As a result, as shown below, even if the change in characteristics and the change with time overlap, it is possible to detect an abnormality in the air-fuel ratio of a part of the cylinders and an abnormality due to the change in the overall characteristics, which is an extremely excellent effect. Play.

When the change in the characteristics of the intake air amount sensor 18 and the change in the injection characteristics of the fuel injection valve 32 overlap, the learning value KG is usually set.
However, in this embodiment, the learning value KG cannot be detected.
Has a large following delay, and abnormal air-fuel ratio control is detected during transient operation in which deviation of the air-fuel ratio due to fluctuations in individual characteristics of the intake air amount sensor 18, fuel injection valve 32, etc. is significant. Abnormalities due to changes in individual characteristics that affect the fuel ratio control can be detected.

The present invention is not limited to the above embodiment,
For example, the predetermined value γ serving as a criterion for determining whether the swing width ΔFAF of the feedback correction coefficient is the normal value may be a function of the throttle opening change amount ΔTA, as an example below.

(1) A> ΔTA ≧ B and ΔFAF ≧ K1 → increment of counter C2 (2) ΔTA ≧ A and ΔFAF ≧ K2 → increment of counter C2 (K1 <K2) Further, in the present embodiment, the change of the throttle opening TA From the state, it was judged whether there was a transient operation and whether it was abnormal,
Instead of this, it may be estimated from the sudden change in the engine speed.

Next, the second embodiment will be described based on the flowchart of the air-fuel ratio control abnormality detection routine shown in FIG.

When the air-fuel ratio control abnormality detection routine shown in FIG. 6 is started, it is first determined whether or not the air-fuel ratio feedback control (F / B) by the air-fuel ratio signal from the O ₂ sensor 38 is being executed (step 500), if this routine has not been executed, this routine is temporarily terminated, and if it is being executed, the change amount ΔTA (for example, the change amount in 0.8 seconds) of the throttle opening TA detected by the throttle sensor 24 per unit time is calculated. It is read (step 510), and then it is determined whether or not it is a transition time (step 520) depending on whether or not the amount of change ΔTA per unit time exceeds 15 deg. If it is determined that it is not a transient time, it is temporarily terminated, and if it is a transient time, then the fluctuation width ΔFAF of the feedback correction coefficient per unit time (for example, the maximum value and the minimum value in 0.8 seconds). Difference) is read (step 530), and it is judged whether or not this variation ΔFAX exceeds 15% by a predetermined value (step 540).
(However, 0 ≤ CLR ≤ 10) is decremented (step 5
50), end as it is, and if it exceeds, counter CLR
Is incremented (step 560) and the process proceeds to the next step. After incrementing, the counter CLR
Is determined to be 10 (step 570), and if it is less than 10, the process is temporarily terminated, and if 10 is reached, an "on" signal is output to the air-fuel ratio control abnormality display section 60 (step 580). ).

According to the present embodiment described above, the abnormality of the air-fuel ratio control during the transient operation can be detected as in the case of the first embodiment, and according to the present embodiment, the unit time of sampling should be as short as possible. It is possible to detect the abnormality of the air-fuel ratio control by adjusting the value of the feedback correction coefficient FAF during transient operation and extracting only the fluctuation state of the feedback correction coefficient FAF.

[Advantages of the Invention] In the engine air-fuel ratio control abnormality detection device of the present invention, during acceleration transient operation, a state in which the swing range of the air-fuel ratio correction value is equal to or greater than a predetermined value occurs frequently or continuously. It is judged that the engine air-fuel ratio control is abnormal.

During this acceleration transient operation state, the follow-up of learning control is delayed, and the characteristic changes of various components (such as the intake air amount sensor) appear remarkably as fluctuations in the air-fuel ratio correction value. By detecting the abnormality, it is possible to accurately detect the abnormality due to the variation of the individual characteristics in which the abnormality does not easily appear in the air-fuel ratio control in the steady state.

[Brief description of drawings]

FIG. 1 is a configuration diagram illustrating a basic configuration of an engine air-fuel ratio control abnormality detecting device of the present invention, FIG. 2 is a configuration diagram of an embodiment of the present invention, and FIG. 3 is an air-fuel ratio of the first embodiment. Flow chart of control abnormality detection routine, FIG. 4 shows TAmax and TAmin.
Flowchart of calculation update routine, Fig. 5 shows the FAFma
x, FAFmin calculation update routine flowchart, and FIG. 6 is a flow chart of the air-fuel ratio control abnormality detection routine of the second embodiment. MA: engine, MB: air-fuel ratio sensor, MC: correction coefficient calculation means, MD: learning means, ME: air-fuel ratio control means, MF
...... Acceleration transient state detection means, MG ・ ・ ・ Swing width detection means, MH
...... Counting means, MI ...... Air-fuel ratio abnormality judging means, 10 ......
Engine, 12 ...... engine controller, 24 ...... throttle sensor, 32 ...... fuel injection valve, 38 ...... O ₂ sensor, 60 ...... air-fuel ratio control abnormality display unit

Claims (1)

[Claims] 1. An air-fuel ratio sensor for detecting an air-fuel ratio from a confluent portion of exhaust gas of each cylinder of an engine, and a correction coefficient calculation means for calculating a feedback correction coefficient based on a detection value of the air-fuel ratio sensor, Learning means for storing a deviation between the feedback correction coefficient and the reference value as a learning value; and an empty space of the engine by correcting the amount of fuel supplied to the engine based on the calculated feedback correction coefficient and the stored learning value. In an air-fuel ratio control abnormality detection device for an engine, comprising an air-fuel ratio control means for controlling a fuel ratio, an acceleration transient state detection means for detecting that the engine is in a predetermined acceleration transient operation state, and a swing range of the feedback correction coefficient The swing width detecting means for detecting, and the swing width of the feedback correction coefficient is a predetermined value or more only in the acceleration transient operation state. For example, a count means for increasing the count value by a predetermined addition value and a predetermined subtraction value if the swing width is less than a predetermined value, and an air-fuel ratio control of the engine is abnormal when the count value becomes a predetermined count value or more. An air-fuel ratio control abnormality detecting device for an engine, comprising: