JP7575725B2 - Control device for internal combustion engine - Google Patents

Description

The present invention relates to technology for detecting the exhaust air-fuel ratio of an internal combustion engine.

2. Description of the Related Art An exhaust passage of an internal combustion engine is provided with a sensor for detecting the air-fuel ratio in the exhaust passage in order to control the air-fuel ratio of the internal combustion engine to improve exhaust emissions and to enhance fuel economy and drivability.
For example, in Patent Document 1, an air-fuel ratio sensor (air-fuel ratio detection means) and an O2 sensor (oxygen concentration detection means) are provided near an exhaust purification catalyst provided in the exhaust passage, and fuel injection control is performed based on the detection value of the air-fuel ratio sensor, and the detection value of the air-fuel ratio sensor is corrected based on the detection value of the O2 sensor, thereby improving the accuracy of the detection value of the air-fuel ratio sensor.

Furthermore, in Patent Document 1, the exhaust temperature is estimated based on the intake air volume and target air-fuel ratio of the internal combustion engine, and the detection value of the O2 sensor is corrected based on the estimated exhaust temperature, thereby improving the accuracy of the detection value of the air-fuel ratio sensor that is corrected based on the detection value of the O2 sensor.

Japanese Patent Application Publication No. 9-49448

In Patent Document 1, the detection value of the O2 sensor is corrected based on the estimated exhaust temperature. When correcting the detection value of the air-fuel ratio sensor based on the detection value of this O2 sensor, the detection value of the O2 sensor that has been corrected based on the exhaust temperature is used. However, since the corrected detection value of the O2 sensor may not represent the change in oxygen concentration in the exhaust passage more accurately than the detection value of the O2 sensor before correction, it may not be possible to sufficiently improve the accuracy of the air-fuel ratio feedback control based on the detection value of the air-fuel ratio sensor.

The present invention was made in consideration of these problems, and its purpose is to provide a control device for an internal combustion engine that appropriately performs corrections using the detection value of the oxygen concentration detection means, and improves the accuracy of air-fuel ratio feedback control based on the detection value of the air-fuel ratio detection means.

In order to achieve the above object, a control device for an internal combustion engine of the present invention comprises an exhaust purification device provided in an exhaust passage of an internal combustion engine, an air-fuel ratio detection means provided upstream of the exhaust purification device, and an oxygen concentration detection means provided downstream of the exhaust purification device, and feedback controls the air-fuel ratio so that the detection value of the air-fuel ratio detection means becomes a target value, and the control device comprises temperature acquisition means for acquiring a temperature of the oxygen concentration detection means, correction means for correcting the target value in accordance with an output value of the oxygen concentration detection means, and correction amount change means for changing a correction amount of the target value by the correction means based on the temperature of the oxygen concentration detection means acquired by the temperature acquisition means, and the correction means corrects the target value to the lean side when the output value of the oxygen concentration detection means falls within a rich region, and the rich region is a region where a large deviation from a theoretical air-fuel ratio region occurs. the correction means corrects the target value more to the lean side as the output value of the oxygen concentration detection means is located in a region among the multiple regions into which the rich region is divided and which has a greater deviation from the stoichiometric air-fuel ratio region, and the correction amount change means changes the correction amount by the correction means so that the target value becomes leaner as the temperature of the oxygen concentration detection means acquired by the temperature acquisition means is higher, and the correction amount change means does not change the correction amount by the correction means based on the temperature of the oxygen concentration detection means for the region among the multiple regions into which the rich region is divided and which has the greatest deviation from the stoichiometric air-fuel ratio region, and does not change the correction amount by the correction means based on the temperature of the oxygen concentration detection means by more than a predetermined amount for the region among the multiple regions into which the rich region is divided and which has the smallest deviation from the stoichiometric air-fuel ratio region .

This makes it possible to suppress the effect of temperature on the oxygen concentration detection means, and improve the accuracy of correcting the target value of the feedback control of the air-fuel ratio based on the detection value of the oxygen concentration detection means.
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In particular, the higher the temperature of the oxygen concentration detection means, the greater the amount of correction of the target value by the correction means. This improves the correction accuracy of the target value of the air-fuel ratio feedback control in response to the characteristics of the oxygen concentration detection means, in which the range of variation of the output value narrows as the temperature increases.
Preferably, the correction means does not correct the target value in the region obtained by dividing the rich region into a plurality of regions and in which the deviation from the theoretical air-fuel ratio region is the smallest when the temperature of the oxygen concentration detection means is below a predetermined value, and the correction amount change means corrects the target value even in the region obtained by dividing the rich region into a plurality of regions and in which the deviation from the theoretical air-fuel ratio region is the smallest when the temperature of the oxygen concentration detection means is equal to or higher than a predetermined value.

As a result, even if the output value of the oxygen concentration detection means does not correct the target value when the temperature of the oxygen concentration detection means is below a predetermined value, the target value of the feedback control of the air-fuel ratio is corrected when the temperature of the oxygen concentration detection means is above a predetermined value. Therefore, even in an oxygen concentration detection means that has a characteristic that the range of variation of the output value becomes narrower as the temperature increases, it is possible to appropriately capture changes in oxygen concentration and perform feedback control with high accuracy.

Preferably , an exhaust gas recirculation means is provided for recirculating exhaust gas to the intake air, and the correction means corrects the target value to the lean side when the output value of the oxygen concentration detection means falls within the rich region, and the larger the amount of recirculated exhaust gas becomes, the more the correction means corrects the target value to the lean side.

As a result, by correcting the target value to the lean side in response to the increase in the amount of exhaust gas recirculated, which reduces nitrogen oxides (NOx) in the exhaust, the air-fuel ratio of the exhaust gas flowing into the exhaust purification device can be controlled to an appropriate range in which emissions of nitrogen oxides and carbon monoxide (CO) are reduced.
Preferably, the invention includes an ignition timing changing means for changing the ignition timing of the internal combustion engine, and when the output value of the oxygen concentration detection means falls within the rich region, the correction means corrects the target value to the lean side, and the more the ignition timing is retarded, the more the correction means corrects the target value to the rich side.

As a result, by correcting the target value to the rich side in response to the reduction in carbon monoxide in the exhaust due to the retarded ignition timing, the air-fuel ratio of the exhaust flowing into the exhaust purification device can be controlled to an appropriate range that reduces emissions of nitrogen oxides and carbon monoxide.

According to the control device for an internal combustion engine of the present invention, the effect of the temperature of the oxygen concentration detection means on the detection value can be suppressed by changing the correction amount of the target value of the feedback control of the air-fuel ratio based on the detection value of the oxygen concentration detection means based on the temperature of the oxygen concentration detection means, and the target value of the feedback control of the air-fuel ratio can be appropriately set. This makes it possible to appropriately control the air-fuel ratio of the exhaust flowing into the exhaust purification device, thereby improving the exhaust purification performance of the exhaust purification device.

1 is a schematic configuration diagram of an intake and exhaust system of an engine according to an embodiment of the present invention; 4 is a graph showing the purification performance of each exhaust component and the output value of an O2 sensor versus the exhaust air-fuel ratio in a three-way catalyst. 4 is an example of a map for setting a LAFS correction amount. 11 is another example of a map for setting a LAFS correction amount. 1 is a graph showing the purification performance of each exhaust component and the output value of an O2 sensor versus the exhaust air-fuel ratio in a three-way catalyst, and shows an example of setting a threshold value for determining a LAFS correction amount.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic diagram showing the configuration of an intake and exhaust system of an engine 2 (internal combustion engine) to which a control device according to an embodiment of the present invention is applied.
The engine 2 is mounted on the vehicle as a driving source.
The engine 2 is a multi-cylinder gasoline engine, and for simplicity, only one cylinder is shown in Fig. 1. The engine 2 is configured to be able to inject fuel into the intake port 4 of each cylinder from a fuel injection valve 3 provided in the intake port 4 of each cylinder at any injection timing and injection amount.

An intake passage 5 of the engine 2 is provided with a throttle valve 6 for adjusting the flow rate of fresh air.
On the other hand, an exhaust passage 10 of the engine 2 is provided with a three-way catalyst 12 as an exhaust purification device.
The three-way catalyst 12 has the function of oxidizing HC and CO in the exhaust gas and reducing NOx at a theoretical air-fuel ratio, thereby removing these exhaust components from the exhaust gas.

The exhaust passage 10 of the engine 2 is provided with a LAFS (linear air-fuel ratio sensor) 22 (exhaust air-fuel ratio detection means) on the upstream side of the three-way catalyst 12, and an O2 sensor 23 (oxygen concentration detection means) that detects the exhaust air-fuel ratio and an exhaust temperature sensor 24 (temperature acquisition means) that detects the exhaust temperature are provided on the downstream side of the three-way catalyst 12.
The engine control unit 30 is configured to include input/output devices, memory devices (ROM, RAM, non-volatile RAM, etc.), a timer, a central processing unit (CPU), etc., and receives detection information from various sensors such as the LAFS 22 and the O2 sensor 23, as well as other vehicle operation information such as the amount of accelerator operation of the vehicle, and calculates the amount of fuel injection from the fuel injection valve 3 and the opening of the throttle valve 6 based on this information, thereby controlling the operation of the various devices mentioned above, thereby controlling the operation of the engine 2.

Specifically, the engine control unit 30 feedback controls the fuel injection amount so that the detection value of the LAFS 22 becomes a target air-fuel ratio (target value), for example, a value indicating the theoretical air-fuel ratio.
2 is a graph showing the purification performance of each exhaust component and the output value of the O2 sensor 23 with respect to the exhaust air-fuel ratio in the three-way catalyst 12 when the engine 2 is operated at a predetermined rotation speed and a predetermined load. In FIG. 2(A), the solid line shows the output value of the LAFS 22. The dashed line shows the amount of carbon monoxide CO and hydrocarbons HC, and the dashed line shows the amount of nitrogen oxides NOx discharged from the three-way catalyst 12. The amount of fuel injection is feedback-controlled based on the detection value of the LAFS 22, with the air-fuel ratio at which the amount of carbon monoxide CO, hydrocarbons HC, and nitrogen oxides NOx discharged from the three-way catalyst 12 is small, that is, the area near the theoretical air-fuel ratio (theoretical air-fuel ratio area), being set as the target air-fuel ratio. FIG. 2(B) shows the output value of the O2 sensor 23. In FIG. 2(B), the dashed line shows the output value of the O2 sensor 23 when the O2 sensor 23 is in a high temperature state, and the dashed line shows the output value of the O2 sensor 23 when the O2 sensor 23 is in a low temperature (normal temperature). The output value of the O2 sensor 23 changes greatly in the stoichiometric air-fuel ratio region, and changes slightly on the rich side and lean side of the stoichiometric air-fuel ratio region. Therefore, the difference between the output value of the O2 sensor 23 at the boundary (rich boundary) between the stoichiometric air-fuel ratio region and the rich region and the output value of the O2 sensor 23 at the boundary (lean boundary) between the stoichiometric air-fuel ratio region and the lean region becomes large. For example, the O2 sensor 23 can determine the state of the exhaust air-fuel ratio downstream of the three-way catalyst 12, i.e., whether the exhaust air-fuel ratio is in the stoichiometric air-fuel ratio region or in a rich or lean state, based on the output value of the O2 sensor 23, by providing a rich threshold value (rich judgment value) and a lean threshold value (lean judgment value) for the output value at the rich boundary and the lean boundary, respectively.

The engine control unit 30 has a function of correcting the output value of the LAFS 22 based on the output value of the O 2 sensor 23 .
Furthermore, the engine control unit 30 of this embodiment is provided with a target air-fuel ratio correction section 1 that corrects the target air-fuel ratio in the above feedback control. The target air-fuel ratio correction section 1 has a temperature acquisition section 35 (temperature acquisition means) that acquires the temperature of the O2 sensor 23 based on the exhaust temperature detected by the exhaust temperature sensor 24, and a correction section 36 (correction means, correction amount change means) that corrects the target air-fuel ratio. The three-way catalyst 12, the LAFS 22, the O2 sensor 23, the exhaust temperature sensor 24, and the target air-fuel ratio correction section 1 and the feedback control function of the air-fuel ratio in the engine control unit 30 correspond to the control device of the present invention.

The correction unit 36 corrects the target air-fuel ratio based on the output value of the O2 sensor 23 and the temperature of the O2 sensor 23. Here, the temperature of the O2 sensor 23 is estimated based on the exhaust temperature detected by the exhaust temperature sensor 24. Specifically, the temperature of the O2 sensor 23 is estimated taking into consideration that the temperature of the O2 sensor 23 changes with a delay relative to the exhaust temperature. The correction unit 36 sets the LAFS correction amount (the correction amount of the target air-fuel ratio) based on the output value of the O2 sensor 23 and the temperature (exhaust temperature) of the O2 sensor 23 using a map such as that shown in FIG. 3. As shown in FIG. 3, the absolute value of the LAFS correction amount (the correction amount of the target air-fuel ratio) is made smaller as the output value of the O2 sensor 23 approaches the theoretical air-fuel ratio, and the absolute value of the LAFS correction amount is made larger as the output value of the O2 sensor 23 becomes richer or leaner. That is, the absolute value of the LAFS correction amount is made larger as the output value of the O2 sensor 23 becomes richer or leaner, and the target air-fuel ratio is changed more significantly.

Also, the higher the exhaust temperature, i.e., the higher the temperature of the O2 sensor 23, the larger the absolute value of the LAFS correction amount (the correction amount of the target air-fuel ratio) is made.
In this embodiment, as shown in Fig. 3, the output value of the O2 sensor 23 is divided into three stages, large, medium, and small, in each of the rich and lean regions, and the exhaust temperature is divided into four stages, and the LAFS correction amount is set to four stages, large, medium, small, and 0 (no correction). When the output value of the O2 sensor 23 is rich and large or lean and large (i.e., a region where the deviation from the theoretical air-fuel ratio region is large), the absolute value of the LAFS correction amount is set to large regardless of the exhaust temperature. When the output value of the O2 sensor 23 is rich or lean and medium (a region where the deviation from the theoretical air-fuel ratio region is smaller than rich and large lean), the absolute value of the LAFS correction amount (correction amount of the target air-fuel ratio) is increased from small to medium to large as the exhaust temperature increases, as described above. When the output value of the O2 sensor 23 is small rich or small lean (a region where the deviation from the theoretical air-fuel ratio region is smaller than middle rich or middle lean), no correction is performed in the lowest region of the four stages of exhaust gas temperature (LAFS correction amount = 0), and the LAFS correction amount is set to small in other regions. Note that the lowest region of the four stages of exhaust gas temperature is a region equal to or higher than the activation temperature of the O2 sensor 23, and preferably extends from the vicinity of the activation temperature (including the activation temperature).

By making such corrections, the LAFS correction amount can be set large in response to the characteristics of the O2 sensor 23, such as the narrowing of the output value fluctuation range due to temperature rise, and the target air-fuel ratio in the air-fuel ratio feedback control can be changed significantly in response to temperature changes. In other words, when the output value fluctuation range of the O2 sensor 23 narrows due to temperature rise, the LAFS correction amount is increased to reflect the small fluctuation in the output value of the O2 sensor 23 in the target air-fuel ratio. Therefore, this corrected target air-fuel ratio can be used to accurately execute air-fuel ratio feedback control based on the output value of LAFS 22.

Furthermore, when the output value of the O2 sensor 23 is small rich or small lean, in the lowest exhaust temperature range of the four stages, the LAFS correction amount is set to 0. However, even if the output value of the O2 sensor 23 is in a range close to the stoichiometric air-fuel ratio, in the case where the exhaust temperature is equal to or higher than the second lowest range of the four stages, the LAFS correction amount is set to small, not 0.
As a result, even if the output value of the O2 sensor 23 does not correct the LAFS correction amount when the temperature of the oxygen concentration detection means is low and below a predetermined value, the LAFS correction amount is set to be small when the temperature of the O2 sensor 23 is above a predetermined value, and the target air-fuel ratio in the feedback control is corrected, so that feedback control can be performed with high accuracy even if the air-fuel ratio of the exhaust gas near the O2 sensor 23 is close to the theoretical air-fuel ratio. That is, even if the output value of the O2 sensor 23 exceeds the rich threshold value or the lean threshold value when the temperature of the O2 sensor 23 is below a predetermined value, when the temperature of the O2 sensor 23 is above a predetermined value (the second lowest region of the four exhaust gas temperature stages), the fluctuation range of the output value of the O2 sensor 23 becomes narrower and the output value of the O2 sensor 23 does not exceed the rich threshold value or the lean threshold value, so that the correction of the target air-fuel ratio may not be performed even if the exhaust gas is in a state where the correction of the target air-fuel ratio is originally desired. Even if the output value of the O2 sensor 23 does not correct the LAFS correction amount when the temperature of the oxygen concentration detection means is low and below a predetermined value, when the temperature of the O2 sensor 23 is above a predetermined value, the LAFS correction amount is set to a small value and the target air-fuel ratio in feedback control is corrected, thereby eliminating such a situation and enabling feedback control to be performed with high accuracy.

Furthermore, if the engine 2 is equipped with an EGR device (exhaust gas recirculation means), the target air-fuel ratio may be further corrected based on the EGR amount (amount of exhaust gas recirculated). Specifically, the correction unit 36 may correct the target air-fuel ratio to the leaner side as the amount of exhaust gas recirculated increases.
As a result, the target air-fuel ratio can be corrected in response to the reduction in NOx in the exhaust gas due to the increase in the amount of recirculation of the exhaust gas. Specifically, in the case where the exhaust gas purification device is the three-way catalyst 12 and the target air-fuel ratio is the stoichiometric air-fuel ratio, the amount of NOx in the exhaust gas is reduced by increasing the amount of recirculation of the exhaust gas, but the amount of CO in the exhaust gas is not reduced as much as the amount of NOx. Therefore, the air-fuel ratio region in which the amount of CO and NOx emitted from the three-way catalyst 12 is reduced is expanded to the lean side. By setting the target air-fuel ratio in the center of this expanded air-fuel ratio region, the exhaust gas can be kept in good condition even if the air-fuel ratio fluctuates. Therefore, even if the air-fuel ratio fluctuates, it is difficult to deviate from the stoichiometric air-fuel ratio region, and the exhaust gas purification performance of the three-way catalyst 12 can be improved. It is not necessary to set the target air-fuel ratio in the center of the expanded air-fuel ratio region, but by doing so, even if the air-fuel ratio fluctuates, the fluctuated air-fuel ratio is likely to fall within the air-fuel ratio region in which the amount of CO and NOx emitted from the three-way catalyst 12 is reduced.

Furthermore, if the engine control unit 30 has a function of changing the ignition timing (ignition timing changing means), it is preferable to further correct the target air-fuel ratio based on the ignition timing. Specifically, it is preferable that the correction unit 36 corrects the target air-fuel ratio to the rich side as the ignition timing is retarded.
This allows the target air-fuel ratio to be corrected in response to the reduction in CO in the exhaust gas due to the retardation of the ignition timing. Specifically, in the case where the exhaust gas purification device is a three-way catalyst 12 and the target air-fuel ratio is the stoichiometric air-fuel ratio, the CO in the exhaust gas is reduced by retarding the ignition timing, but the NOx in the exhaust gas is not reduced as much as the CO. Therefore, the air-fuel ratio region in which the amount of CO and NOx emitted from the three-way catalyst 12 is reduced is expanded to the rich side. By setting the target air-fuel ratio in the center of this expanded air-fuel ratio region, the exhaust gas can be kept good even if the air-fuel ratio fluctuates slightly. Therefore, even if the air-fuel ratio fluctuates, it is difficult to deviate from the stoichiometric air-fuel ratio region, and the exhaust gas purification performance of the three-way catalyst 12 can be improved.

Although the description of the present invention is now completed, the present invention is not limited to the above embodiment.
For example, in the above embodiment, the output value of the O2 sensor 23 is divided into three stages of large, medium, and small for rich and lean, and the exhaust temperature is divided into four stages, and the LAFS correction amount is set to four stages of large, medium, small, and 0 in the correction unit 36, but it may be appropriately set to other two or more stages, or may be set continuously. Also, when the output value of the O2 sensor 23 is small rich or small lean and in the region where the exhaust temperature is the lowest, the LAFS correction amount is set to 0, but it may be set to small or a value less than small.

The LAFS correction amount may be set differently in the rich and lean regions. For example, since the output value of the O2 sensor 23 in the lean region is less susceptible to temperature changes of the O2 sensor 23, the LAFS correction amount may be set smaller in the lean region than in the rich region, or the LAFS correction amount may be set to 0 in the lean region. Note that if there is a case in which the lean region is more susceptible to temperature changes than the rich region, the LAFS correction amount in the lean region may be set larger than the LAFS correction amount in the rich region.

Furthermore, the exhaust purification device is not limited to a three-way catalyst, and the target air-fuel ratio of the detection value of the LAFS 22 when feedback controlling the fuel injection amount does not have to be the stoichiometric air-fuel ratio.
In addition, in the above embodiment, the correction unit 36 is set to change the LAFS correction amount (the correction amount of the target air-fuel ratio) based on the output value of the O2 sensor 23 and the exhaust temperature, but the LAFS correction amount may be changed by changing the threshold value that determines the LAFS correction amount based on the output value of the O2 sensor 23 and the exhaust temperature.

As shown in Figures 4 and 5, the correction unit 36 has three thresholds, a first threshold, a second threshold, and a third threshold, in order from the rich side, for the output value of the O2 sensor 23, and sets the LAFS correction amount depending on which of these thresholds the output value of the O2 sensor 23 is in. Furthermore, the settings of the first threshold, the second threshold, and the third threshold differ depending on the exhaust temperature (temperature of the O2 sensor 23). For example, in the normal temperature range where the exhaust temperature is appropriately set, when the output value of the O2 sensor 23 is equal to or higher than the first threshold, the LAFS correction amount is large, when it is less than the first threshold and equal to or higher than the second threshold, the LAFS correction amount is small, and when it is less than the second threshold and equal to or higher than the third threshold, the LAFS correction amount is 0. On the other hand, in the high temperature range where the exhaust temperature is higher than the normal temperature range, when the output value of the O2 sensor 23 is equal to or higher than the first threshold, the LAFS correction amount is large, when it is less than the first threshold and equal to or higher than the second threshold, the LAFS correction amount is large, and when it is less than the second threshold and equal to or higher than the third threshold, the LAFS correction amount is set to small. That is, the first and second thresholds in the normal temperature range are lowered to the second and third thresholds in the high temperature range. When the output value of the O2 sensor 23 is less than the third threshold, it is determined that the air-fuel ratio is in the stoichiometric air-fuel ratio range or a range close to the stoichiometric air-fuel ratio range, and the LAFS correction amount is set to 0. Therefore, in the high temperature range where the exhaust temperature is higher than the normal temperature range, the threshold for determining the LAFS correction amount is lowered compared to the normal temperature range.

As a result, similarly to the above embodiment, the LAFS correction amount is changed based on the temperature of the O2 sensor, and the target air-fuel ratio can be appropriately set.
In the lean region, the LAFS correction amount (absolute value) may be set in the same manner as in the rich region. In this case, the lean judgment value, which is the output value of the O2 sensor 23 at which the LAFS correction amount is switched from 0 to small, is increased in the high exhaust gas temperature region compared to the normal temperature region. This makes it possible to appropriately set the target air-fuel ratio by changing the LAFS correction amount even in the lean region.

The invention can also be widely applied to internal combustion engines other than those used to drive vehicles, which are equipped with an air-fuel ratio detection means in the exhaust passage and feedback-control the air-fuel ratio based on the detection value of the air-fuel ratio detection means.

1 Target air-fuel ratio correction unit 2 Engine (internal combustion engine)
10 exhaust passage 12 three-way catalyst (exhaust gas purification device)
22 LAFS (air-fuel ratio detection means)
23 O2 sensor (oxygen concentration detection means)
24 Exhaust temperature sensor (temperature acquisition means)
30 Engine control unit 35 Temperature acquisition unit (temperature acquisition means)
36 Correction unit (correction means, correction amount change means)

Claims (4)

an exhaust purification device provided in an exhaust passage of the internal combustion engine;
an air-fuel ratio detection means provided upstream of the exhaust purification device;
an oxygen concentration detection means provided downstream of the exhaust purification device,
A control device for an internal combustion engine that feedback controls an air-fuel ratio so that a detection value of the air-fuel ratio detection means becomes a target value,
A temperature acquisition means for acquiring a temperature of the oxygen concentration detection means;
a correction means for correcting the target value in accordance with an output value of the oxygen concentration detection means;
a correction amount changing means for changing a correction amount of the target value by the correction means based on the temperature of the oxygen concentration detection means acquired by the temperature acquisition means ,
the correction means corrects the target value to a lean side when the output value of the oxygen concentration detection means falls in a rich region that is a region richer than a stoichiometric air-fuel ratio region,
the rich region is divided into a plurality of regions according to the magnitude of deviation from the stoichiometric air-fuel ratio region, and the correction means corrects the target value to the lean side more significantly as the output value of the oxygen concentration detection means is positioned in a region among the plurality of regions into which the rich region is divided that has a greater deviation from the stoichiometric air-fuel ratio region,
the correction amount changing means changes the correction amount by the correcting means so that the target value becomes leaner as the temperature of the oxygen concentration detecting means acquired by the temperature acquiring means becomes higher;
The correction amount changing means does not change the correction amount by the correcting means based on the temperature of the oxygen concentration detecting means for a region in which the deviation from the stoichiometric air-fuel ratio region is the largest among the regions obtained by dividing the rich region into a plurality of regions, and does not change the correction amount by the correcting means based on the temperature of the oxygen concentration detecting means by a predetermined amount or more for a region in which the deviation from the stoichiometric air-fuel ratio region is the smallest.
A control device for an internal combustion engine. the correction means does not correct the target value when the temperature of the oxygen concentration detection means is less than a predetermined value in a region in which the deviation from the stoichiometric air-fuel ratio region is smallest among a plurality of regions obtained by dividing the rich region,
When the temperature of the oxygen concentration detection means is equal to or higher than a predetermined value, the correction amount change means corrects the target value even in a region where the deviation from the stoichiometric air-fuel ratio region is smallest among a plurality of regions obtained by dividing the rich region.
2. The control device for an internal combustion engine according to claim 1. An exhaust gas recirculation means is provided for recirculating the exhaust gas to the intake air,
3. The control device for an internal combustion engine according to claim 1, wherein the correction means corrects the target value to the lean side when the output value of the oxygen concentration detection means falls within the rich region , and corrects the target value to the lean side as the amount of recirculated exhaust gas increases. an ignition timing changing means for changing the ignition timing of the internal combustion engine;
3. The control device for an internal combustion engine according to claim 1, wherein the correction means corrects the target value to the lean side when the output value of the oxygen concentration detection means falls within the rich region , and corrects the target value to the rich side as the ignition timing is retarded.

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