WO1993017232A1

WO1993017232A1 - Method and system for controlling air-fuel ratio of internal combustion engine

Info

Publication number: WO1993017232A1
Application number: PCT/JP1991/000650
Authority: WO
Inventors: Junichi Furuya
Original assignee: Junichi Furuya
Priority date: 1990-05-16
Filing date: 1991-05-16
Publication date: 1993-09-02
Also published as: JP2757064B2; JPH0422726A

Abstract

An air-fuel ratio control system provided with air-fuel ratio sensors across a three-way catalyst, for performing air-fuel ratio feedback control, wherein, in controlling an air-fuel ratio feedback correction coefficient on the basis of an output value from the air-fuel sensor on the upstream side, a control operation value is corrected on the basis of an output value of the air-fuel ratio sensor on the downstream side. Here, the correction value on the basis of the output from the air-fuel ratio sensor on the downstream side is calculated from a uniform learning correction value uniformly used in the whole of operational regions and an area-by-area learning correction value specific to each of separate operational regions. Further, when the uniform learning correction value is added for correction, a process for subtracting for correction from the area-by-area learning correction value the corrected value is performed only in a region where learning progresses beyond a predetermined value among the respective operational regions in which area-by-area learning correction values are stored. With the above-described arrangement, the promotion of progress of the air-fuel ratio learning control by the air-fuel ratio sensor on the downstream side can be compatible with an improvement in accuracy of learning, and furthermore, the progress of learning can be promoted in the region where the chance of learning is little and learning in separate operational regions is required.

Description

Akira Itoda

Method and apparatus for controlling air-fuel ratio of an internal combustion engine

Technology field>

The present invention relates to a method and an apparatus for controlling an air-fuel ratio of an intake air-fuel mixture to a target air-fuel ratio in an internal combustion engine mounted on an automobile, and in particular, an air-fuel ratio sensor is provided for each of an exhaust system on an upstream side and a downstream side of an exhaust purification catalyst. The present invention relates to a method and an apparatus for performing feedback control of the air-fuel ratio with high accuracy based on the detection values of these two air-fuel ratio sensors.

Conventionally, in order to maintain good conversion efficiency in a three-way catalyst provided in an exhaust system for exhaust gas purification, feedback control of the air-fuel ratio of an engine intake air-fuel mixture to a stoichiometric air-fuel ratio has been performed. I have.

Specifically, first, an air-fuel ratio sensor (oxygen sensor) that detects the air-fuel ratio of the engine intake air-fuel mixture via the oxygen concentration in the exhaust gas is compared with the combustion chamber to ensure detection responsiveness. The air-fuel ratio sensor detects the rich air-fuel ratio of the actual air-fuel ratio with respect to the stoichiometric air-fuel ratio based on the oxygen concentration in the exhaust gas detected by the air-fuel ratio sensor. Feedback control is performed on the fuel supply amount in a direction to bring the air-fuel ratio closer to the theoretical air-fuel ratio.

However, since the air-fuel ratio sensor provided in the exhaust system relatively close to the combustion chamber as described above is exposed to high-temperature exhaust, there is a problem that its characteristics are liable to change due to thermal deterioration or the like. In addition, the exhaust manifold provided in the air-fuel ratio sensor has a problem that it is difficult to accurately detect the average air-fuel ratio of all cylinders due to insufficient mixing of exhaust gas for each cylinder. It was hot. Therefore, in the above-described conventional air-fuel ratio feedback control, responsiveness is ensured, but it is difficult to stably perform high-precision air-fuel ratio control. I got it. .

In view of this point, in addition to the air-fuel ratio sensor on the upstream side of the catalyst, an air-fuel ratio sensor is also provided on the downstream side of the catalyst, and the feedback value of the air-fuel ratio is controlled using the detection values of these two air-fuel ratio sensors. Some have been proposed (see JP-A-58-48757, etc.).

In other words, the air-fuel ratio sensor on the downstream side has poor responsiveness because it is far from the combustion chamber, but has little thermal effect because it is on the downstream side of the catalyst, and the poisoning amount due to toxic components in the exhaust gas is low. It is possible to detect the average air-fuel ratio of all the cylinders because the air-fuel ratio is small and the exhaust gas mixture is good, so that high-accuracy and stable detection performance can be obtained compared to the air-fuel ratio sensor provided on the upstream side.

Therefore, two air-fuel ratio feedback correction coefficients independently set based on the detection values of the two air-fuel ratio sensors are used in combination, or the air-fuel ratio feedback set by the upstream air-fuel ratio sensor is used. The control amount of the feedback correction coefficient (proportional constant or integral constant), the comparison voltage used to determine the output voltage of the upstream air-fuel ratio sensor, and the detection result of the upstream air-fuel ratio sensor are used for actual control. The delay time is corrected based on the detection result of the air-fuel ratio sensor on the downstream side. With the air-fuel ratio control using the two air-fuel ratio sensors, variations in the output characteristics of the upstream air-fuel ratio sensor can be compensated for by the downstream air-fuel ratio sensor, and highly accurate air-fuel ratio feedback control can be performed.

However, in the air-fuel ratio control using two air-fuel ratio sensors (generally, oxygen sensors) as described above, the required level of the air-twist ratio correction amount during the feedback control is increased during non-feedback control (at open loop). In particular, there may be a large gap, and the following problems occur especially at the start of feedback control when shifting from non-feedback control to feedback control. That is, since the detection of the air-fuel ratio by the downstream air-fuel ratio sensor is delayed as compared with the upstream-side air-fuel ratio sensor, the speed of the air-fuel ratio correction control by the downstream air-fuel ratio sensor is reduced by the air-fuel ratio correction using the upstream air-fuel ratio sensor. If the speed is set to be almost the same, the control overshoot will increase. Therefore, in order to suppress the overshooting of the control, in the air-fuel ratio control using the air-fuel ratio sensor on the downstream side, the control speed is lower than the speed of the air-fuel ratio control by the air-fuel ratio sensor on the upstream side. You have set.

Therefore, until the air-fuel ratio correction amount controlled based on the downstream air-fuel ratio sensor (for example, the proportional correction amount in the proportional-integral control of the air-fuel ratio feedback correction amount based on the upstream air-fuel ratio sensor) reaches the required value. It takes a long time to reach the target air-fuel ratio, which may lead to deterioration of fuel efficiency, drivability, and exhaust properties.

In addition, when the engine operating state transitions to a different area during the air-fuel ratio feedback control, the air-fuel ratio may still deviate significantly from the target air-fuel ratio due to the difference in the required level of the air-fuel ratio correction between the operating areas. This also leads to deterioration of fuel efficiency, drivability, and exhaust characteristics. Therefore, an average value of the air-fuel ratio correction amount based on the air-fuel ratio sensor on the downstream side is sequentially calculated as a learning correction amount and stored for each operating region, and the learning correction amount is used together with the air-fuel ratio correction amount to perform air-fuel ratio correction. There has been previously proposed a device that can always perform stable air-fuel ratio control by controlling the fuel ratio (see Japanese Patent Application Laid-Open No. 63-97851, etc.).

However, as described above, the control speed of the air-fuel ratio correction based on the downstream air-fuel ratio sensor is set relatively low to suppress overshoot. When the amount is learned for each driving region, the learning does not easily progress. In addition, the required value of the air-fuel ratio correction amount varies greatly depending on the operating conditions. It is desirable to secure the learning accuracy by dividing the area to be finely divided.However, if the area is divided finely, the time spent staying in each area is shortened, and the frequency with which the actual operating conditions correspond to each area is also reduced. Less will further hinder learning progress.

Therefore, it has conventionally been difficult to achieve the two goals of accelerating learning and improving learning accuracy at a high level, and a certain compromise was found to compare operating areas where the learning correction amount was recorded. And the driving performance was deteriorated due to the deterioration of the exhaust properties and the variation of the air-fuel ratio.

Therefore, as will be described later, uniform learning in a wide driving area to promote the progress of learning, and subdivided learning in each driving area to maintain the improvement of learning accuracy are simultaneously performed while matching. The present invention has invented an air-fuel ratio control method and apparatus for an internal combustion engine that can achieve both the promotion of the air-fuel ratio control learning by the air-fuel ratio sensor on the downstream side of the catalyst and the improvement of the learning accuracy.

However, it has been found that the air-fuel ratio control using these two types of learning has the following problems to be further improved.

In other words, when the uniform learning in the wide operating area and the learning for each of the subdivided operating areas are simultaneously performed as described above, the learning correction amount for the wide operating area is added and updated. In other words, all the subdivided operating regions included in this wide region are controlled by the updated learning correction amount. Therefore, it is necessary to subtract and update the learning correction amount in each of the subdivided operation regions by the update amount to prevent the correction based on the learning correction amount from becoming excessive.

However, as described above, in the configuration in which the entire learning value is subtracted and updated when the uniform learning value is added and updated, in the subdivided driving region, in the region where the learning opportunity is small, the uniform learning correction is performed before convergence. Quantity update Only the subtraction will be updated. For this reason, there is a problem that the convergence becomes slower in an area that is farther from the convergence level and has less learning opportunities due to such an update, and the learning progresses by performing uniform learning and area-specific learning simultaneously. Even if we tried to achieve both the promotion and the improvement of the learning accuracy, learning with the air-fuel ratio sensor downstream of the catalyst, which had a detection response delay, could not achieve a sufficient effect.

The present invention has been made in view of the above-described problems. First, uniform learning in a wide driving range for promoting the progress of learning, and divided into different driving ranges for maintaining improved learning accuracy. The air-fuel ratio control of the internal combustion engine achieves both the advancement of the air-fuel ratio learning control by the air-fuel ratio sensor on the downstream side of the catalyst and the improvement of the learning accuracy. It is an object to provide a method and an apparatus.

In addition, in the air-fuel ratio learning control using the air-fuel ratio sensor on the downstream side of the catalyst that performs the uniform learning and the area-specific learning as described above, the learning opportunities in the area-based learning are reduced, and the convergence in the operation area is improved. It aims to improve.

Further, it is another object of the present invention to be able to reliably and easily determine a driving area where learning opportunities are small in area-specific learning.

In order to achieve the above object, the method and apparatus for controlling the air-fuel ratio of an internal combustion engine according to the present invention basically comprises: an upstream side and a downstream side of a catalytic exhaust purification device provided in an exhaust system of an internal combustion engine. First and second air-fuel ratio sensors whose output values change in response to the concentration of specific components in the exhaust gas that change according to the air-fuel ratio of the engine intake air-fuel mixture are provided. Then, a first air-fuel ratio correction amount is calculated based on the output value of the first air-fuel ratio sensor, and a second air-fuel ratio correction amount is calculated based on the output value of the second air-fuel ratio sensor. Air-fuel ratio correction amount The final air-fuel ratio correction amount is calculated based on this, and the air-fuel ratio of the engine intake air-fuel mixture is controlled.

Here, as a characteristic configuration according to the present invention, the second air-fuel ratio correction amount is set as follows.

That is, while the learning correction amount for each area recorded for each of the plurality of operating regions is corrected and rewritten based on the output value of the second air-fuel ratio sensor, it is based on the average level of the learning correction amount for each area. The stored value of the uniform learning correction amount used uniformly in the entire operation region by the correction amount is added and corrected and rewritten. Here, when the uniform learning correction amount is added and corrected, the correction amount is subtracted and corrected from the error correction amount for each area for each operating region, and the learning correction amount for each error is rewritten.

Then, the second air-fuel ratio correction amount is set based on the learning correction amount for each area corresponding to the corresponding operation region and the uniform learning correction amount uniformly used for all operation regions.

As described above, the second air-fuel ratio correction amount based on the output value of the second air-fuel ratio sensor is calculated based on the area-specific learning correction amount applied to each area and the uniform learning used uniformly in all operation areas. If learning is set separately for the correction amount, learning and correction of the air-fuel ratio based on the output value of the second air-fuel ratio sensor will ensure uniform learning and promote the progress of learning. Learning accuracy can be maintained by separate learning.

Here, the degree of learning progress is determined for each driving area in which the learning correction amount for each area is stored, and for the driving area where the learning progress degree is equal to or less than a predetermined value, the amount obtained by adding and correcting the uniform learning correction amount is used. It is preferable to prohibit the process of subtraction correction.

By such a subtraction correction prohibition process, even in an operating region where learning opportunities are small and learning progress is slow, the required level in the operating region can be quickly adjusted. It can be made to converge.

As described above, in the driving region where learning opportunities are small, when the addition and correction of the uniform learning correction amount is not to be subtracted and corrected, the number of times the output value of the second air-fuel ratio sensor has crossed the target air-fuel ratio equivalent value is calculated as It is preferable that the learning correction amount for each area is obtained for each driving area where the learning correction amount is stored, and the degree of learning progress is determined for each driving area based on the number of times of experience.

In other words, in an operating region where the output value of the second air-fuel ratio sensor has no experience of crossing the target air-fuel ratio equivalent value, the optimum value for matching the air-fuel ratio detected by the second air-fuel ratio sensor to the target is used. This means that the air-fuel ratio correction amount has not been confirmed at all, and conversely, if the number of times of crossing the target air-fuel ratio equivalent value is large, the air-fuel ratio correction amount can be brought closer to the optimum level. Therefore, it is possible to determine the degree of learning progress for each driving area by using the above-mentioned experience count as it is to indicate the degree of learning progress.

Further, as the air-fuel ratio sensors provided respectively on the upstream and downstream of the exhaust gas purifying catalyst, sensors whose output values change in response to the oxygen concentration in the exhaust gas can be used.

Furthermore, the second air-fuel ratio correction amount may be configured to be calculated as a value for correcting the control operation amount of the first air-fuel ratio correction amount.

Further, the exhaust gas purification catalyst is a three-way catalyst, and the first air-fuel ratio correction amount and the first air-fuel ratio correction amount are adjusted so that the air-fuel ratio detected by the first air-fuel ratio sensor and the second air-fuel ratio sensor approaches the stoichiometric air-fuel ratio. It is possible to configure so that the air-fuel ratio correction amounts of 2 are calculated respectively. With this configuration, the conversion efficiency of oxidation and reduction in the three-way catalyst is kept at the best.

Further, an average value of the learning correction amount for each area when the output value of the second air-fuel ratio sensor crosses a value corresponding to the target air-fuel ratio is obtained, and the uniform learning correction amount is corrected based on the average value. It is good to configure. Since the uniform learning correction amount is a correction amount used uniformly in all the operation regions, it should be given as an average value of the required correction levels in each operation region. Therefore, it is assumed that the learning correction amount for each area when the output value of the second air-fuel ratio sensor crosses a value corresponding to the target air-fuel ratio roughly indicates the optimum correction level in that region. The uniform learning correction amount is corrected based on the average value of the optimum correction level.

Brief description of drawings>

FIG. 1 is a block diagram showing a basic configuration of an air-fuel ratio control device according to the present invention.

FIG. 2 is a diagram showing a system configuration in one embodiment of the present invention. FIG. 3 is a flowchart showing a fuel injection amount setting routine in the embodiment.

FIG. 4 is a flowchart showing an air-fuel ratio feedback correction coefficient setting routine in the embodiment.

Figs. 5 (A) and (B) are diagrams showing the operating regions of the uniform learning correction amount map and the area-specific learning correction amount map, respectively.

FIG. 6 and FIG. 7 are diagrams for explaining how the uniform learning correction value and the learning correction value for each area are updated.

A schematic configuration of an air-fuel ratio control apparatus for an internal combustion engine according to the present invention is as shown in FIG. 1, and an embodiment of the air-fuel ratio learning control apparatus and method for such an internal combustion engine is shown in FIGS. 2 to 7. It is.

2, an intake passage 12 of an engine 11 has an air flow meter 13 for detecting an intake air flow rate Q and a throttle for controlling the intake air flow rate Q in conjunction with an accelerator pedal (not shown). A valve 14 is provided.Each branch of the downstream intake manifold is provided with electromagnetic fuel injection for each cylinder. Valve 15 is provided.

The fuel injection valve 15 is driven to open by an injection pulse signal from a control unit 16 incorporating a microcomputer, is pressure-fed from a fuel pump (not shown), and is controlled to a predetermined pressure by a pressure regulator. The injected fuel is supplied.

Further, a water temperature sensor 17 for detecting a cooling water temperature Tw in the cooling jacket of the engine 11 is provided.

On the other hand, the exhaust passage 18 is provided with a first air-fuel ratio sensor 19 for detecting the air-fuel ratio of the intake air-fuel mixture by detecting the oxygen concentration in the exhaust at the exhaust manifold collecting section, and the exhaust pipe on the downstream side thereof is provided. The exhaust gas is provided with a three-way catalyst 20 as an exhaust gas purification catalyst for purifying exhaust gas by oxidizing C〇 and HC in the exhaust gas and reducing NO x, and further comprises a first empty space downstream of the three-way catalyst 20. A second air-fuel ratio sensor 21 having the same function as the fuel ratio sensor is provided.

The first air-fuel ratio sensor 19 and the second air-fuel ratio sensor 21 are known oxygen concentration sensors whose output voltage changes in response to the oxygen concentration in the exhaust gas. By utilizing the sudden change in the oxygen concentration of the air, the rich / lean of the actual air-fuel ratio, which is the stoichiometric air-fuel ratio, can be detected. In addition, a crank angle sensor 24 is built in the distribution unit (not shown in FIG. 2), and a crank unit angle signal output from the crank angle sensor 22 in synchronization with the engine rotation is counted for a certain period of time. Alternatively, the engine speed N is detected by measuring the cycle of the crank reference angle signal.

Next, the air-fuel ratio control by the control unit 16 will be described with reference to the flowcharts of FIGS. Here, the outline of the air-fuel ratio control of the present embodiment will be described. While the air-fuel ratio feedback correction coefficient α is proportionally integrated based on the output value of the first air-fuel ratio sensor 19, the control of the correction coefficient The manipulated variable (proportional component) is corrected based on the output value of the second air-fuel ratio sensor 21. In the correction control based on the output value of the second air-fuel ratio sensor 21, uniform learning that is used uniformly in all operation regions, and learning by region in each of the plurality of divided operation regions is performed. Is used together.

In this embodiment, the first air-fuel ratio correction amount calculating means, the second air-fuel ratio correction amount calculating means, the air-fuel ratio correction amount calculating means, the air-fuel ratio control means, the first area learning correction amount correcting means, The functions of the uniform learning correction amount correction means, the second area-specific learning correction amount correction means, the air-fuel ratio correction amount calculation means based on the learning amount, the learning progress determination means, and the correction prohibition means are described in FIG. As shown in the flow chart of Fig. 4, the control unit 16 is provided as software, and the uniform learning correction amount storage means and the area-specific learning correction amount storage means are provided by the control unit 16. It is assumed that the RAM with the backup function built in is equivalent.

FIG. 3 shows a fuel injection amount setting routine, which is performed at predetermined intervals (for example, 10 ms).

Step (denoted by S in the figure) In step 1, based on the intake air flow rate Q detected by the air flow meter 13 and the engine speed N calculated based on the signal from the crank angle sensor 24, the suction per unit rotation The basic fuel injection amount Tp corresponding to the air amount is calculated by the following equation.

T p = K x QXN (K is a constant)

In step 2, various correction coefficients C 0 EF are set based on the cooling water temperature detected by the water temperature sensor 17, and the like.

At step 3, the air-fuel ratio feedback correction coefficient (final air-fuel ratio correction amount) set by the air-fuel ratio feedback correction coefficient setting routine described later is read.

In step 4, a voltage correction amount Ts is set based on the battery voltage value. This is because of the change in the effective valve opening time of the fuel injector 15 due to battery voltage fluctuation. This is for correcting the change.

In step 5, the final fuel injection amount (fuel supply amount) Ti is calculated according to the following equation. The function of step 5 of setting the fuel injection amount Ti while correcting with the air-fuel ratio feedback correction coefficient as shown in the following equation corresponds to the air-fuel ratio control means.

T i = T p x C O E F x α + T s

In step 6, the calculated fuel injector Ti is set in an output register.

Thus, at a predetermined fuel injection timing synchronized with the rotation of the engine, a drive pulse signal having a pulse width of the calculated fuel injection amount Ti is given to the fuel injection valve 15 to perform fuel injection.

Next, the air-fuel ratio feedback correction coefficient setting routine will be described with reference to the flowchart of FIG. This routine is executed in synchronization with the engine speed.

In step 11, the operating conditions for performing feedback control of the air-fuel ratio (the operating conditions for learning the uniform learning correction amount P H0SM and the learning correction amount for each area PHOSSx, which will be described later, match. However, the engine steady operation is added to the control conditions. It is preferable to improve the accuracy by determining whether or not. If the above operating conditions are not satisfied, this routine ends. In this case, the feedback correction coefficient α is clamped to the value at the end of the previous feedback control or a fixed reference value, and the feedback control is stopped.

In step 12, the signal voltage V ₀₂ (output value) from the first air-fuel ratio sensor 19 and the signal voltage V ′ 0 2 (output value) from the second air-fuel ratio sensor 21 are input. In step 13, (in this example the stoichiometric air-fuel ratio) the first air signal voltage V ₀₂ of the fuel ratio sensor 19 and the target air-fuel ratio input in step 12 is compared with the reference value S equivalent, Ritsuchi air-fuel ratio from the lean Or when reversing from rich to lean It is determined whether or not.

If it is determined that the reversal is being performed, the process proceeds to step 14, and the uniform learning correction amount PH0SM for uniformly correcting the proportional correction amount PH0S of the air-fuel ratio feedback correction coefficient (air-fuel ratio correction amount) is uniformly corrected. Based on the engine speed N and the basic fuel injection amount Tp, the area-based learning correction amount PHOSSx of the proportional component correction amount PH0S is also read out from the amount map (stored in the RAM of the microcomputer built in the control unit 16). From the area-based learning correction amount map (also stored in RAM), the area-based learning correction amount PHOSSx stored in the corresponding operating area is searched and found.

As shown in FIG. 5, the uniform learning correction amount map stores one uniform learning correction amount PH0SM in the entire operation region where learning is performed, and the engine-specific learning correction amount map includes The learning correction amount PHOSSx for each area is recorded in each of the nine operating regions divided into three by the rotation speed N and the basic fuel injection amount Tp.

In step 15, the second air-fuel ratio signal voltage V _'02 and the target air-fuel ratio from the sensor 21 (the stoichiometric air-fuel ratio) is compared with the corresponding reference value SL, the air-fuel ratio from the lean or al-liter or Ritsuchi to lean Judgment is made as to whether or not the vehicle has been reversed (whether or not the vehicle has crossed the standard 值 SL equivalent to the target air-fuel ratio).

When it is determined to be the time of reversal, the process proceeds to step 16, and the value PHOSP that uses the area-based learning correction amount PHOSSx retrieved in step 14 this time. After that, the process proceeds to step 17, where the uniform learning correction amount PHOSM correction amount DPHOSP is calculated by the following equation.

DPHOSP = M (PHOSP. + PHOSP) / 2

Here, PHOSP-! Is area-based learning correction amount PHOSSx when the output V _'02 of the previous second air-fuel ratio sensor 21 has been inverted, M is a positive constant (<1) Ru der. That is, the correction amount DPHOSP is calculated every time the output of the second air-fuel ratio sensor 21 is inverted. The area-based learning correction amount P HOSSx is set as a value corresponding to a predetermined ratio of the averaged value, and the uniform learning correction amount P H0SM sets the average level of the learning-based learning correction amount P HOSSx for all operating area variers. Make them learn.

In step 18, the uniform learning correction amount PH0SM is corrected by the value obtained by adding the correction amount DPH0SP calculated in step 17 to the uniform learning correction amount PH0SM searched in step 14, and the corrected value is stored in the RAM. Update the uniform learning correction amount PH0 SM.

Therefore, step 17.18 corresponds to uniform learning correction amount correcting means. Next, in step 19, the count value CONTROx obtained by integrating the number of times of output reversal (the number of times of rich / lean reversal) of the second air-fuel ratio sensor 21 is compared with the predetermined value RC0NT for each operation region of the learning correction amount map for each area. Then, the learning progress degree is determined for each area. If the output of the second air-fuel ratio sensor 21 is inverted many times in the same area, the learning in that area progresses accordingly, and the air-fuel ratio correction amount required in the operation area is learned. Therefore, when the count value CONTROx is equal to or less than the predetermined value, it can be determined that the learning progress is slow in the area. The predetermined value may be set, for example, from the average of the count values CONTROx for each operation region.

In the present embodiment, the inversion of the output means that the output V ′ _{02 of} the second air-fuel ratio sensor 21 has crossed the reference value SL corresponding to the stoichiometric air-fuel ratio, and the count value CONTROx is This indicates the number of times the air-fuel ratio has crossed the reference value SL.

In step 19, it is determined that the count value CONTROx is equal to or greater than the predetermined value RCONT, and the learning correction amount P HOSSx for each operating region in which the degree of learning progress is high is corrected in step 20 by the uniform learning correction amount P H0SM. The map is rewritten by subtracting and correcting the amount DPH0SP, but the count value CONTROx Is determined to be less than the predetermined value RCONT, and the correction rewriting of the area-based learning correction amount P HOSSx in step 20 is not executed in the operation region where the learning progress is low.

That is, when the uniform learning correction amount P H0SM is added and corrected, the correction amount as the uniform learning correction amount P H0SM + area-specific learning correction amount P HOSSx in the entire area increases by the rewriting correction amount DPH0SP. Therefore, the learning correction amount P HOSSx for each area needs to be subtracted and corrected by that amount.In this embodiment, however, learning is sufficiently advanced instead of subtracting and correcting the learning correction amount P HOSSx for each area for all areas. It is performed only in the operation area that is determined to be in operation.

As a result, the area that has not been subjected to the subtraction correction is set in the excessive correction direction, but the learning is not sufficiently advanced and the learning correction for each area is in the stage before converging to the required amount in the operation area. With respect to the quantity P H0SS _x , the above-described setting of the excessive correction direction is set in a direction approaching the required amount, and the learning convergence in an area where learning opportunities are small and learning progresses slowly can be accelerated.

The steps 19 and 20 correspond to the learning progress determining means, the second area-specific learning correction amount correcting means, and the correction prohibiting means.

In step 21, the area-based learning correction amount P HOSSx corresponding to the end of the current driving state error corrected in step 20 or kept at the previous map value is calculated in the next step 17. Therefore, it is set as P HOSP-i, and then the process proceeds to step 22.

If it is determined in step 15 that the second air-fuel ratio sensor 21 is not in the inverting state, the process jumps from step 16 to step 21 and proceeds to step 22.

In step 22, determine Ritsuchi, the lean output V _'02 of the second air-fuel ratio sensor 21 as compared to the target air-fuel ratio phase in question reference value SL with respect to the target of the actual air-fuel ratio Separate.

When the air-fuel ratio is determined to rich (V, _{0 2>} SL) goes to stearyl-up 23, Eria a value obtained by subtracting the Eria based learning correction amount P HOSSx or al a predetermined value DPH0SR retrieved in step 14 Correction calculation of separate learning correction amount P HOSSx is performed. Further, the process proceeds to step 24 when the air-fuel ratio is determined to lean (V _'02 rather SL), the retrieved area-specific learning correction amount P HOSSx a predetermined value DP HOSL the added area-based learning correction amount by the value P HOSSx Is corrected.

That is, each time this routine is executed, the learning correction amount P HOSSx for each error of the pertinent area is searched and read out, and is read out in the direction where the actual air-fuel ratio approaches the target air-fuel ratio based on the output of the second air-fuel ratio sensor 21. To correct. Therefore, the steps 22 and 23 correspond to the first error correction amount correcting means.

In step 25, the area-based learning correction amount P HOSSx stored in the corresponding operation area of the error-based learning correction amount map is rewritten with the learning correction amount for each area P HOSSx corrected in step 23 or 24. Accordingly, the learning correction amount P HOSSx for each error is sequentially corrected in a direction in which the air-fuel ratio detected by the second air-fuel ratio sensor 21 approaches the target, and the map data is rewritten based on the correction result. It has become.

In step 26, the uniform learning correction amount P HOSM updated as described above and the learning correction amount P HOSSx for each area are added, and the second air-fuel ratio based on the output value of the second air-fuel ratio sensor 21 is added. Calculate the proportional correction amount P HOS corresponding to the correction amount. The proportional correction amount P HOS corresponding to the second air-fuel ratio correction amount is used to correct the control operation amount in the first air-fuel ratio correction amount setting control based on the output value of the first air-fuel ratio sensor 19. This is the value used.

Step 26 corresponds to the air-fuel ratio correction amount calculating means based on the learning amount. Next, the routine proceeds to step 27, where rich / lean determination is performed by the first air-fuel ratio sensor 19, and when lean-rich is reversed, the routine proceeds to step 28, where the air-fuel ratio feedback correction coefficient α in the decreasing direction given when the rich is reversed for α setting is reversed. the proportional component P _R from the reference value P _R0 is updated by the air-fuel ratio control correction amount PH0S reduced value. Then updated with the value obtained by subtracting the proportional part P _R, the air-fuel ratio feedback correction coefficient from the current value in step 29.

When the air-fuel ratio is reversed, the process proceeds to step 30, and the proportional amount in the increasing direction given when the air-fuel ratio feedback correction coefficient is set to the air reversal is set to the reference value P _{L 0} by the air-fuel ratio control correction amount P L0. Update with the value obtained by adding H0S. Next, in step 31, the air-fuel ratio feedback correction coefficient is updated with a value obtained by adding the proportional component 分 ι · to the current value.

If it is determined in step 13 that the output of the first air-fuel ratio sensor 19 is not at the time of inversion, the process proceeds to step 32, where rich / lean determination based on the output of the first air-fuel ratio sensor 19 is performed. If so, proceed to step 33 to update the air-fuel ratio feedback correction coefficient a with the value obtained by reducing the integral I _κ from the current value. If lean, proceed to step 34 to update with the value obtained by adding the integral. Here, the function of setting the air-fuel ratio feedback correction coefficient excluding the correction by steps 28 and 30 in the steps 27 to 34 is the first air-fuel ratio correction amount calculation by the first air-fuel ratio sensor 19. Steps 27 to 34 including step 28 and step 30 correspond to the air-fuel ratio correction amount calculating means.

With this configuration, the learning is advanced in the entire driving range where the learning is performed with the uniform learning correction amount P H0SM, and the output value of the second air-fuel ratio sensor 21 is adjusted to the reference value (target air-fuel ratio equivalent value). The convergence can be promoted, and the learning correction amount P H0SS _x for each area enables high-precision learning corresponding to the different correction requests for each operation area.The second air-fuel ratio sensor 21 controls the air-fuel ratio learning control. Progress Both line promotion and improvement of learning accuracy are compatible.

FIGS. 6 and 7 show how the uniform learning correction amount P H0SM and the area-specific learning correction amount P HOSSx are updated, respectively.

In this embodiment, based on the air-fuel ratio feedback control based on the detection value of the first air-fuel ratio sensor 19, the proportion of the air-fuel ratio feedback correction coefficient is calculated based on the detection value of the second air-fuel ratio sensor. Although an example in which the present invention is applied to the correction is shown, it is obvious that the present invention is not limited to this. For example, the air-fuel ratio feedback correction coefficient obtained by combining the two values with the air-fuel ratio feedback correction coefficient set by correcting the integral component instead of the proportional component, It may be used for correcting the injection amount. Further, while performing the air-fuel ratio feedback control by the first air-fuel ratio sensor, the reference value SL for rich / lean judgment based on the output value of the first air-fuel ratio sensor 19 and the output value of the first air-fuel ratio sensor 19 The delay time for setting the air-fuel ratio feedback correction coefficient LMD based on the above is also applicable to the correction of the delay time by the detection of the second air-fuel ratio sensor 21.

Industrial applicability>

As described above, according to the method and apparatus for controlling the air-fuel ratio of an internal combustion engine according to the present invention, in the air-fuel ratio control for controlling the air-fuel ratio of the engine intake air-fuel mixture to the target air-fuel ratio, the control accuracy to the target air-fuel ratio deteriorates. Since it can be self-corrected and the accuracy and convergence of such self-correction can be obtained at a high level, it is most suitable for air-fuel ratio control of an electronically controlled fuel injection gasoline internal combustion engine. It is extremely effective in raising.

Claims

Scope of word blue

(1) Exhaust gas purification provided in the exhaust passage of the internal combustion engine Provided on the upstream side and downstream side of the catalyst, respectively, the output value changes in response to the concentration of the specific gas component in the exhaust that changes depending on the air-fuel ratio And a first and a second air-fuel ratio sensor.

Correcting and rewriting the learning correction amount for each area in the corresponding operating region based on the learning correction amount for each area stored for each of the plurality of operating regions and the output value of the second air-fuel ratio sensor;

Adding and correcting and rewriting the stored value of the uniform learning correction amount that is uniformly used in the entire operation region by the correction amount based on the average level of the learning correction amount for each area;

Subtracting and correcting the added correction amount of the uniform learning correction amount from each of the learning correction amounts for each area in each operation region, and

Calculating a second air-fuel ratio correction amount based on the output value of the second air-fuel ratio sensor based on the learning correction amount for each area and the uniform learning correction amount in the corresponding operation region;

Calculating a first air-fuel ratio correction amount based on an output value of the first air-fuel ratio sensor;

Setting a final air-fuel ratio correction amount based on the first air-fuel ratio correction amount and the second air-fuel ratio correction amount;

Controlling the air-fuel ratio of the engine intake air-fuel mixture based on the final air-fuel ratio correction amount;

An air-fuel ratio control method for an internal combustion engine comprising:

(2) determining the degree of learning progress for each driving region in which the learning correction amount for each area is stored;

About the driving region where the degree of the learning progress is determined to be equal to or less than a predetermined value 2. The air-fuel ratio control method for an internal combustion engine according to claim 1, further comprising a step of prohibiting subtraction and correction of the addition and correction of the uniform learning correction amount.

(3) The number of times that the output value of the second air-fuel ratio sensor has crossed the target air-fuel ratio equivalent value is determined for each operating region in which the learning correction amount for each area is stored, and for each operating region based on the number of experiences. 3. The method for controlling an air-fuel ratio of an internal combustion engine according to claim 2, wherein the degree of learning progress is determined.

(4) The air-fuel ratio control method for an internal combustion engine according to claim 1, wherein the first and second air-fuel ratio sensors are sensors whose output values change in response to oxygen concentration in exhaust gas.

(5) The air-fuel ratio control method for an internal combustion engine according to claim 1, wherein the second air-fuel ratio correction amount is a value for correcting a control operation amount of the first air-fuel ratio correction amount.

(6) The exhaust gas purification catalyst is a three-way catalyst, and the first air-fuel ratio correction amount is set so that the air-fuel ratio detected by the first air-fuel ratio sensor and the second air-fuel ratio sensor approaches the stoichiometric air-fuel ratio. 2. The air-fuel ratio control method for an internal combustion engine according to claim 1, wherein the second air-fuel ratio correction amount is calculated.

(7) The average value of the learning correction amount for each area when the output value of the second air-fuel ratio sensor crosses a value corresponding to the target air-fuel ratio is obtained, and the uniform learning correction amount is corrected based on the average value. 2. The method for controlling an air-fuel ratio of an internal combustion engine according to claim 1, which is configured as described above.

(8) The first type, which is provided upstream and downstream of the exhaust purification catalyst provided in the exhaust passage of the internal combustion engine, and whose output value changes in response to the concentration of the specific gas component in the exhaust that changes depending on the air-fuel ratio. A first air-fuel ratio correction amount calculating means for calculating a first air-fuel ratio correction amount based on an output value of the first air-fuel ratio sensor; and

Second air-fuel ratio correction amount calculating means for calculating a second air-fuel ratio correction amount based on an output value of the second air-fuel ratio sensor; Air-fuel ratio correction amount calculating means for calculating a final air-fuel ratio correction amount based on the first air-fuel ratio correction amount and the second air-fuel ratio correction amount;

Air-fuel ratio control means for controlling the air-fuel ratio of the engine intake air-fuel mixture based on the final air-fuel ratio correction amount calculated by the air-fuel ratio correction amount calculation means;

An air-fuel ratio control device for an internal combustion engine, comprising:

The second air-fuel ratio correction amount calculating means,

A uniform learning correction amount storage means for rewritably storing a uniform learning correction amount uniformly used in all operation regions;

An area-specific learning correction amount storage means for rewritably storing an area-specific learning correction amount for each of a plurality of divided operation regions;

On the basis of the learning correction amount for each area retrieved from the learning correction amount storage for each area and the output value of the second air-fuel ratio sensor, the learning correction amount for each area of the operating region corresponding to the learning correction amount storing means for each area. Means for correcting the learning correction amount for each first error that corrects and rewrites

Adding and correcting the uniform learning correction amount stored in the uniform learning correction amount storage unit by a correction amount based on the average level of the area-specific learning correction amount, and rewriting;

Subtracting and correcting each of the learning correction amounts for each of the operating ranges stored in the learning correction amount for each area by the correction amount obtained by adding and correcting the uniform learning correction amount by the uniform learning correction amount correcting means. (2) Learning correction amount for each area

The second air-fuel ratio correction amount is calculated based on the learning correction amount for each area of the corresponding operating region retrieved from the learning correction amount storing means for each area and the uniform learning correction amount stored in the uniform learning correction amount storing means. Air-fuel ratio correction amount calculating means based on the learning amount to be calculated;

An air-fuel ratio control device for an internal combustion engine, comprising:

(9) learning progress discriminating means for discriminating the degree of learning progress for each operation area of the learning-specific learning correction amount storage means,

Correction prohibiting means for prohibiting correction of the learning correction amount for each area by the second learning correction amount correcting means for the area in which the degree of learning progress is determined to be equal to or less than a predetermined value by the learning progress determining means;

9. The air-fuel ratio control device for an internal combustion engine according to claim 8, wherein:

(10) The learning progress determining means obtains the number of times that the output value of the second air-fuel ratio sensor has crossed the value corresponding to the target air-fuel ratio for each operation area of the learning correction amount storage means for each area, and based on the number of times of experience. 10. The air-fuel ratio control device for an internal combustion engine according to claim 9, wherein the degree of learning progress is determined for each operation region.

(11) The air-fuel ratio control device for an internal combustion engine according to claim 8, wherein the first and second air-fuel ratio sensors are sensors whose output values change in response to oxygen concentration in exhaust gas.

(13) The second air-fuel ratio correction amount calculated by the second air-fuel ratio correction amount calculating means corrects the control operation amount of the first air-fuel ratio correction amount by the first air-fuel ratio correction amount calculating means. The air-fuel ratio control for an internal combustion engine according to claim 8, which is a value for

(13) The exhaust purification catalyst is a three-way catalyst, and the first air-fuel ratio correction amount calculating means and the second air-fuel ratio correction amount calculating means are a first air-fuel ratio sensor and a second air-fuel ratio sensor. 9. The air-fuel ratio control device for an internal combustion engine according to claim 8, wherein the first air-fuel ratio correction amount and the second air-fuel ratio correction amount are calculated in a direction in which the air-fuel ratio detected in the step approaches the stoichiometric air-fuel ratio. .

(14) The uniform learning correction amount correction means obtains an average value of the learning correction amount for each area when the output value of the second air-fuel ratio sensor crosses a value corresponding to the target air-fuel ratio, and calculates the average value. 9. The air-fuel ratio control device for an internal combustion engine according to claim 8, wherein the air-fuel ratio control device is configured to correct the uniform learning correction amount based on the correction amount.