JPS6318154A - Air-fuel ratio control device for internal combustion engine - Google Patents

Abstract

PURPOSE:To enable prevention of the occurrence of a trouble by copying with abnormality on an air-fuel ratio sensor, by a method wherein, relation to a cylinder group where an air-fuel ratio sensor to which abnormality occurs is present, an air-fuel ratio is controlled according to an estimating value of a correction amount based on an output value from other normal air-fuel ratio sensor. CONSTITUTION:In an engine 10, plural cylinders 11a-11d, 11e-11h are set in a state to be divided into two groups responding to banks on both sides, and exhaust systems 16a and 16b are set independently from each other in a manner to be positioned facing each group. In this constitution, air-fuel ratio sensors 17a and 17b are situated to the exhaust systems 16a and 16b, respectively, and detecting signals therefrom are inputted to a control unit 18 to control each of injectors 22a-11h. The control unit 18 calculates a central value of two different air-fuel ratio control amounts responding to the respective groups, stores two different deviation values responding to a difference between the central values of the one and the other in each group, and estimates an air-fuel ratio control amount, based on the central value and the deviation value.

Description

[Detailed Description of the Invention] [Industrial Field of Application] This invention is applicable to a type 8-cylinder engine in which the cylinders are divided into multiple groups and an exhaust system is set for each group. The present invention relates to an air-fuel ratio control device for an internal combustion engine that controls the air-fuel ratio for each group in the engine.

[Prior art] For engines, for example, Japanese Patent Application Laid-Open No. 59-126047
As shown in the publication, an oxygen concentration sensor installed in the exhaust system of this engine detects the amount of oxygen contained in the exhaust gas, that is, the air-fuel ratio of this engine, and injects fuel according to the state of this air-fuel ratio. Quantity control is being carried out.

Here, in an engine with a large number of engine cylinders, the plurality of cylinders mentioned above are divided into a plurality of groups. For example, in an 8-cylinder engine, these 8 cylinders are divided into two groups. A V-type eight-cylinder engine is known in which the two groups are arranged in a V-shape.

In this case, an exhaust system is formed for each cylinder group set in a ■ shape.

In the case of such a V-type 8-cylinder engine, it is possible to perform air-fuel ratio control in common for all cylinders, but it is considered that air-fuel ratio control is performed independently for each cylinder glue unit. There is.

When controlling the air-fuel ratio for each cylinder group in this manner, it is necessary to set an air-fuel ratio sensor in each exhaust system set for each cylinder group.

In other words, two or more air-fuel ratio sensors are used in one engine, and if one of these multiple air-fuel ratio sensors becomes abnormal, the air-fuel ratio of this engine Control will not be executed properly.

Specifically, in the type 8-cylinder engine mentioned above, an air-fuel ratio sensor is set in each of the right and left banks, and air-fuel ratio feedback control is performed independently based on the detection signal from the air-fuel ratio sensor. Running. If that air-fuel ratio sensor malfunctions and is determined to be abnormal by the computer that executes engine control, air-fuel ratio feedback control will be stopped in the system of the air-fuel ratio sensor where the malfunction was detected. control to do so. In this system, oven control is performed, or control is performed as is at the upper or lower limit value. Therefore, normal air-fuel ratio control will not be performed in the bank where the faulty air-fuel ratio sensor exists, and as a result, not only will exhaust gas deteriorate, but if the air-fuel ratio continues to be high, In some cases, the catalyst in the exhaust gas purification system may become damaged.

[Problems to be Solved by the Invention] This invention has been made in view of the above-mentioned points. Even in this case, the air-fuel ratio control of the system in which this failure has occurred is performed effectively, and the exhaust gas condition is maintained in a normal state. Balanced air-fuel ratio control is performed throughout the engine. An object of the present invention is to provide an air-fuel ratio control device for an internal combustion engine.

[Means for Solving the Problems] That is, in the air-fuel ratio control device for an internal combustion engine according to the present invention, for example, when two air-fuel ratio sensors, a first and a second air-fuel ratio sensor, are used, this For example, the relative deviation value of the center value of the air-fuel ratio control amount corresponding to the detected value of each air-fuel ratio sensor is learned and memorized for each operating condition. The air-fuel ratio control amount on the side of the failed air-fuel ratio sensor is predicted and set based on the detected value from the fuel ratio sensor and the learned and stored deviation value.

[Function] In the air-fuel ratio control device as described above, even if one of the multiple air-fuel ratio sensors fails, there is no deviation value in the air-fuel ratio control amount from other systems by other air-fuel ratio sensors. Since the information is constantly learned and stored, the air-fuel ratio is detected by the malfunctioning air-fuel ratio sensor based on the control amount based on the detection value of other air-fuel ratio sensors that are still operating normally and the deviation value that has been learned and stored. The air-fuel ratio control amount of the system in which fuel ratio control is executed is predicted. Since the air-fuel ratio control of the system of the failed air-fuel ratio sensor is executed according to this predicted value, the fuel injection amount control, etc. corresponding to the operating control state of the engine at that time is performed with sufficient accuracy. This means that the system will be executed in a high state.

[Embodiments of the invention] Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows, for example, the configuration of a control system for a V-type eight-cylinder engine 10, which is divided into a right bank and a left bank, and eight cylinders 11a to 11d1 and lie to L.
lh is placed and set.

That is, the eight cylinders 11a to llh are divided into first and second groups corresponding to the right and left banks, and in this engine,
Air-fuel ratio feedback control is performed independently in each bank.

Each of the cylinders 11a to llh is supplied with intake air taken in from an air cleaner 13 via an intake pipe 12, and the intake pipe 12 is equipped with an air flow meter 14 for measuring the amount of intake air, and an accelerator. A throttle valve 15 is provided which is driven by operation, and the amount of intake air is controlled in response to the operation of the accelerator pedal.

In addition, exhaust pipes lea and 18b are independently set corresponding to the right and left banks of the cylinders 11a to ILh, respectively. first and second air-fuel ratio sensors 17a and 17b that measure the amount of
is provided. And these air-fuel ratio sensors 17a
and 17b1, and an air-fuel ratio detection signal and an intake air amount measurement signal from the air flow meter 14 and the like are supplied to an electronic engine control unit 18 constituted by, for example, a microcomputer. The control unit 18 is also supplied with a detection signal from a throttle opening sensor 19 that detects the opening state of the throttle valve 15.

The engine 10 is further provided with a water temperature sensor 20 that measures the temperature of the engine cooling water, and a crank angle sensor 21 that detects the crank angle of the engine 10. Detection signals from these sensors 20 and 21 are also used for carrot control. It is supplied to unit 18.

That is, the engine control unit 18 calculates the basic amount of fuel injection based on the amount of intake air measured by the air flow meter 14, and also calculates the basic amount of fuel injection based on the amount of intake air measured by the air flow meter 14. The basic injection amount is corrected and the actual fuel injection amount is calculated based on a detection signal corresponding to the operating state of the engine, such as the engine rotational speed obtained based on the signal.

Based on this calculation result, the injectors 2 are set for each cylinder 11a to llb of the engine 10.
2a to 22h are controlled so that an amount of fuel corresponding to the above calculation result is injected into each cylinder 11a to llh.

Additionally, the air-fuel ratio sensors 17a and 17b determine whether the air-fuel ratio state of the right bank and the left bank, that is, the fuel concentration state of the cylinder groups of the right bank and the left bank, is in a rich state or a lean state. The amount of fuel supplied to each of the cylinder groups of the right bank and the left bank is feedback-controlled in response to the detection result so that the respective stoichiometric air-fuel ratios are achieved.

That is, the right bank and left bank of this V-type 8-cylinder engine 10 independently adjust the air-fuel ratio based on the detection signals from the first and second air-fuel ratio sensors 17a and 17b corresponding to each bank. Feedback control is now executed.

FIG. 2 is for explaining the control state in the engine control unit 18 as described above, especially the air-fuel ratio control state. This figure shows the control state of the right bank, and the left bank is also the same. Control is executed.

That is, an interruption of this routine is executed in response to an appropriate clock pulse. First, in step 101, it is determined whether the conditions for this engine to execute air-fuel ratio feedback (A/F) control are met.

Here, until the engine is warmed up, the exhaust gas temperature rises, and the air-fuel ratio sensor is activated, there is a need to increase the amount of fuel during deceleration operation, when fuel is cut, and when high-load operation occurs. is detected based on the detection signals from the throttle opening sensor 19 and the water temperature sensor 20. During such a state, it is assumed that the execution conditions for air-fuel ratio feedback control are not in place. judge. If the conditions for executing air-fuel ratio feedback are not satisfied, this routine is ended immediately.

If it is determined in step 101 that the execution conditions for air-fuel ratio feedback control are met, the next step 1
02, it is determined whether the first air-fuel ratio sensor 17a of the right bank corresponding to this control routine is operating normally. The means for this determination is to detect that the output value of this sensor 17a does not take a predetermined value (for example, 0.45 V or more, or a rich state) even after a predetermined period of time when the air-fuel ratio feedback condition is satisfied. , or when the output of the air-fuel ratio sensor 17a does not reach a rich state even though the amount of fuel is increasing during high-load operation, etc.
Make it determined to be abnormal. And this step 1
If it is determined that the right air-fuel ratio sensor 17a is abnormal in step 02, this routine is immediately terminated.

If it is determined in step 102 that the air-fuel ratio sensor 1a is normal, the process advances to step 103 to adjust the air-fuel ratio to the stoichiometric air-fuel ratio based on the detection output from the right air-fuel ratio sensor 17a. A correction value rFR(A/F)J is calculated, and the fuel injection amount from the right bank injectors 22a to 22d is corrected according to this correction value. Then, based on the above air-fuel ratio correction value, the average value r
Find "fR(A/F)".

Next, in step 104, it is determined whether the second air-fuel ratio sensor 17b of the left bank, which is different from this control routine, is normal. If it is determined in this step 104 that the second (left side) air-fuel ratio sensor 17b is normal, then in step 105, the air-fuel ratio correction value at that time is determined based on the output value from this air-fuel ratio sensor 17b. The average value rfh(A/F)J is calculated. Then, in the next step 106, the average value rfR of the air-fuel ratio correction value of the right bank is
(A/F)J and the average value of the air-fuel ratio correction value of the left bank [
Find the difference [ΔfRj] from fL(A/F)J. and,
At the end of the next step 10, the operating state of the engine at this time is stored in the memory MR(n) set in the control unit 18.
Detection is performed based on the map stored in the map.

Figure 3 shows the state of the map for determining this operating state. Based on the state of the cooling water temperature, it is classified as to whether or not the engine is currently in a warm-up state, and the throttle valve 15 is Fully open (idling) or rQ/ which is the intake air m (Q) divided by the engine speed (N)
Depending on whether the value of Nj is greater than or equal to a set value, the engine load state is classified into three states: light, medium, and high. That is,
The engine operating state is divided into eight states in total, and it is determined which of these current states the engine belongs to.

The memory area corresponding to each detected operating state contains learning data Δf corresponding to each operating state.
R1 to ΔfR8 are each stored and set.

Then, in step 108, a weighted arithmetic average is calculated between the difference value ΔfR obtained in step 106 and the previously learned value MR(n) detected in step 107, and the learned value is It is to be updated. Here, for example, the following calculations are performed.

MR(n)” i8xMR(n)+Δf Rl/9 Step 1 above
If it is determined in step 04 that there is an abnormality in the second air-fuel ratio sensor 17b, the process proceeds to step 109. This step 1
In step 09, the operating state is detected in the same manner as in step 107, and the learning value ΔfR corresponding to the current operating state is read out. Then, in the next step 110, the average value rfR(A
/F) J and the learning data ΔfR learned corresponding to the operating condition, the left bank air-fuel ratio correction value rFL(A/F
) to calculate J. Specifically, the second one on the left
When the air-fuel ratio sensor 17b is normal, ΔfR - fR (A/F) - fL (A/F), so F p (A / F ) - f R (A / F
)-ΔfR calculation is executed.

That is, if the second air-fuel ratio sensor 17b is not normal, it is impossible to calculate the air-fuel ratio correction amount based on the output value of the air-fuel ratio sensor 17b. first air-fuel ratio sensor 1 of
The predicted value Fh (A/F) of the air-fuel ratio correction amount for the left bank is calculated based on the average value of the air-fuel ratio correction amount obtained based on the output value of 7a and the learned value of the deviation value ΔfH.

Then, air-fuel ratio control for the left bank is executed based on this calculated value.

The above explanation shows the processing routine related to the right bank (first group) equipped with the first air-fuel ratio sensor 17a, but similar processing is performed in the left bank (second group). If the first air-fuel ratio sensor 17a becomes abnormal, the air-fuel ratio control for the right bank is executed by calculating the output value of the second air-fuel ratio sensor 17b and the learned value. It is something.

In the above embodiment, a V-type 8-cylinder engine is used as an example.
The case is shown in which the cylinders are divided into two groups, one on the right side and the other on the left side, and air-fuel ratio feedback control is executed for each group.

However, if multiple cylinders are set up in even more groups, an air-fuel ratio sensor is set for each group, and air-fuel ratio feedback control is executed independently for each group, the above Similar processing can be performed.In other words, if any of the multiple air-fuel ratio sensors becomes abnormal, the air-fuel ratio correction amount based on the output value of the normal air-fuel ratio sensor is used in the same manner as described above. By correcting this based on the learned value, a predicted value of the air-fuel ratio correction amount for the group of air-fuel ratio sensors that has become abnormal can be obtained, and air-fuel ratio control is executed according to this predicted value. It becomes like this.

[Effects of the Invention] As described above, in the air-fuel ratio control device according to the present invention, the cylinders are divided into a plurality of groups, the air-fuel ratio sensor is set for each group, and the air-fuel ratio sensor is set independently for each group. When performing air-fuel ratio feedback control, for example, even if one of the air-fuel ratio sensors becomes abnormal, other normal air-fuel ratio sensors in the cylinder group in which the air-fuel ratio sensor that has experienced the abnormality exist Air-fuel ratio control is now executed based on a predicted value of the air-fuel ratio correction amount based on the output value of the air-fuel ratio sensor. Therefore, even if an abnormality occurs in some of the air-fuel ratio sensors, engine control will be executed in almost the same state as if normal air-fuel ratio feedback was performed, and the exhaust gas may deteriorate or the catalyst This can effectively prevent the occurrence of melting loss and the like.

[Brief explanation of the drawing]

Fig. 1 is a block diagram illustrating an air-fuel ratio control device for an internal combustion engine according to the present invention, Fig. 2 is a flowchart illustrating the flow of control in the engine control unit of the above embodiment, and Fig. 3 shows the process of the above control. FIG. 3 is a diagram illustrating the contents of a memory that stores learning data to be used. 10...Engine, lla~llf...Cylinder, 12
...Intake pipe, 14...Air flow meter, 15...
- Throttle valve, lea, 16b...first and second exhaust pipes (corresponding to right bank and left bank), 17a, L7b...first and second air-fuel ratio sensors, 18...engine control Unit, 19...
・Throttle opening sensor, 20...Water temperature sensor, 21
...Crank angle sensor, 22a-22r...Injector.

Claims (1)

[Scope of Claims] An internal combustion engine in which a plurality of cylinders are divided into at least first and second groups, and an exhaust system is set corresponding to each group, first and second air-fuel ratio sensors respectively set in exhaust systems corresponding to the respective groups; means for monitoring the normal operating state of each of the first and second air-fuel ratio sensors; 2, the center of the first and second air-fuel ratio control amounts corresponding to the first and second groups, respectively, based on the detection signals of the respective air-fuel ratio sensors. means for calculating a value; and corresponding to the first and second groups, each corresponds to the difference between the center value of the air-fuel ratio control amount of the other group and the center value of the air-fuel ratio control amount of its own group. First thing to do
and a means for learning and storing the second deviation value and the second deviation value of the corresponding group by detecting an abnormality of the first or second air-fuel ratio sensor.
or a means for predicting and calculating its own air-fuel ratio control amount based on the center value of the first air-fuel ratio control amount; An air-fuel ratio control device for an internal combustion engine, characterized in that fuel injection amount is controlled based on an air-fuel ratio control amount based on a detection signal of an air-fuel ratio sensor, or the predicted air-fuel ratio control amount.