JP5704038B2 - Air-fuel ratio sensor correction device - Google Patents

Description

  The present invention relates to a correction device for an air-fuel ratio sensor. More specifically, the present invention relates to a correction device that corrects the outputs of air-fuel ratio sensors installed upstream and downstream of a catalyst in an exhaust path of an internal combustion engine.

  Patent Document 1 discloses a system having a catalyst installed in an exhaust path of an internal combustion engine and air-fuel ratio sensors installed respectively upstream and downstream of the catalyst. In this system, the deterioration of the catalyst is judged by comparing the output change of the air-fuel ratio sensor upstream of the catalyst with the output change of the downstream air-fuel ratio sensor. Further, in Patent Document 1, in order to improve the accuracy of the catalyst deterioration determination, the output characteristic of the downstream air-fuel ratio sensor is measured, and the downstream air-fuel ratio is calculated based on the measured output characteristic and the output characteristic of the reference sensor. It has been proposed to correct the output characteristics of the sensor.

  Specifically, in Patent Document 1, the difference between the amplitude of the downstream side air-fuel ratio sensor detected by changing the air-fuel ratio upstream of the catalyst between the rich air-fuel ratio and the lean air-fuel ratio and the amplitude of the reference sensor. Accordingly, a method for correcting the output characteristics of the downstream air-fuel ratio sensor has been proposed.

Japanese Patent Laid-Open No. 06-280662 JP 2003-148207 A JP 2004-124864 A JP 2009-281328 A

  In a system in which air-fuel ratio sensors are arranged before and after the catalyst, and the deterioration of the catalyst is determined by comparing the output changes, if an output error occurs in any of the air-fuel ratio sensors, the output error Affects parameters. As a result, for example, an erroneous determination may occur in the catalyst deterioration determination. Further, in a system that performs feedback correction of the air-fuel ratio in accordance with the output of the air-fuel ratio sensor before and after the catalyst, the output error of the air-fuel ratio sensor can affect the air-fuel ratio control.

  Therefore, in order to realize catalyst deterioration determination and air-fuel ratio control with higher accuracy, it is desired that output errors be reduced for the upstream and downstream air-fuel ratio sensors. In this regard, there is room for improvement in a technique that uniformly corrects only the output of the downstream air-fuel ratio sensor and uniformly covers the entire range from the rich air-fuel ratio to the lean air-fuel ratio, as in the technique of Patent Document 1 above.

  Here, the upstream air-fuel ratio sensor and the downstream air-fuel ratio sensor have different installation locations, and differ in regions where output errors are likely to occur due to differences in installation environments. For example, the concentration of exhaust gas components is completely different between upstream and downstream of the catalyst, and particularly when the exhaust gas is in the vicinity of the stoichiometric air-fuel ratio, the downstream gas of the catalyst has a low concentration. For this reason, in the air-fuel ratio sensor on the downstream side of the catalyst, in the vicinity of the theoretical air-fuel ratio, the concentration fluctuates greatly even if the exhaust gas slightly changes, and an error is likely to occur in its output. As described above, the characteristics of the output error generated in the air-fuel ratio sensor differ depending on the difference in the installation environment of the air-fuel ratio sensor. Accordingly, it is desired to correct the output of the air-fuel ratio sensor in consideration of such output error characteristics.

  The present invention aims to solve the above-described problems, and provides an air-fuel ratio sensor correction apparatus improved so that an output deviation of the air-fuel ratio sensor can be corrected according to the difference in the installation environment of the air-fuel ratio sensor. Is.

In order to achieve the above object, a first invention is a correction apparatus for an air-fuel ratio sensor,
First detection means for detecting the output of a first air-fuel ratio sensor installed upstream of the catalyst in the exhaust path of the internal combustion engine;
Second detection means for detecting an output of a second air-fuel ratio sensor installed downstream of the catalyst in the exhaust path;
The output of the first air-fuel ratio sensor and the second air-fuel ratio when the value of the first air-fuel ratio obtained based on the output of the first air-fuel ratio sensor is within a predetermined range set near the stoichiometric air-fuel ratio. Output correction value calculating means for calculating an output correction value for the second air-fuel ratio sensor according to a difference from an output of the fuel ratio sensor;
Output correction means for correcting the output of the second air-fuel ratio sensor in accordance with the output correction value;
Is provided.

  In a second aspect based on the first aspect, the output correction means outputs the output of the second air-fuel ratio sensor in accordance with the output correction value when the value of the first air-fuel ratio is within the predetermined range. Correct.

  According to a third invention, in the first or second invention, the output correction value calculating means is configured so that the value of the first air-fuel ratio is within the predetermined range and the operating state of the internal combustion engine is a predetermined idle operation. The output correction value is calculated according to the difference between the output of the first air-fuel ratio sensor and the output of the second air-fuel ratio sensor in the state.

  In a fourth aspect based on the third aspect, the output correction means is configured such that the value of the first air-fuel ratio is within the predetermined range, and the operation state of the internal combustion engine is the predetermined idle operation state. In addition, the output of the second air-fuel ratio sensor is corrected according to the output correction value.

According to a fifth invention, in any one of the first to fourth inventions, before the catalyst reaches the activation temperature, a difference between the output of the first air-fuel ratio sensor and the output of the second air-fuel ratio sensor is determined. A reference correction value calculating means for calculating a reference correction value for each of the first air-fuel ratio sensor and the second air-fuel ratio sensor;
Reference correction means for correcting outputs of the first air-fuel ratio sensor and the second air-fuel ratio sensor according to the reference correction value;
Is further provided.

  According to a sixth invention, in any one of the first to fifth inventions, the output correction value calculating means determines the output according to a ratio of the output of the first air-fuel ratio sensor to the output of the second air-fuel ratio sensor. An output correction value is calculated.

According to a seventh invention, in any one of the first to sixth inventions, the output correction value calculation means is configured to output the output correction value when the output correction value has never been calculated after the internal combustion engine is started. To calculate
The output correction means corrects the output of the second air-fuel ratio sensor using the output correction value until the internal combustion engine is first stopped after the output correction value is calculated.

  When the air-fuel ratio is in the vicinity of the stoichiometric air-fuel ratio upstream of the catalyst, the concentration of the exhaust gas component purified by the catalyst is particularly low. For this reason, it is considered that each component concentration of the exhaust gas changes greatly due to a slight change in the gas downstream of the catalyst, and the output of the second air-fuel ratio sensor fluctuates greatly. On the other hand, on the upstream side of the catalyst, the concentration of exhaust gas is relatively high, so even if there is a slight change in gas, the effect is small and output is less likely to vary. In this regard, as in the present invention, if the output correction value for the second air-fuel ratio sensor is calculated in a region where the air-fuel ratio is within a predetermined range near the stoichiometric air-fuel ratio, the region where deviation easily occurs. The output of the second air-fuel ratio sensor at can be corrected to a value closer to the actual air-fuel ratio. Therefore, for example, it is possible to improve the accuracy of control such as catalyst deterioration determination and air-fuel ratio feedback control performed based on the outputs of the first and second air-fuel ratio sensors.

  Further, in the present invention, if the correction using the output correction value of the present invention is performed when the air-fuel ratio is within a predetermined range in the vicinity of the theoretical air-fuel ratio, it is specific to a region where output deviation is likely to occur. This output correction value can be used to correct the output of the second air-fuel ratio sensor in that region. Therefore, the output deviation of the air-fuel ratio sensor can be corrected more accurately.

  Further, the second air-fuel ratio sensor that detects low-concentration exhaust gas reacts more sensitively to a slight change in gas components in a region where the amount of exhaust gas is small, and is more likely to be displaced. Become. In this regard, if the output correction value of the second air-fuel ratio sensor can be calculated based on the output of the first air-fuel ratio sensor in the idling operation state of the present invention, it is more accurate even in the region where the exhaust gas amount is small. The output deviation of the air-fuel ratio sensor can be corrected.

  In the present invention, if the outputs of the first and second air-fuel ratio sensors are corrected based on the difference between the outputs of the first and second air-fuel ratio sensors before the catalyst reaches the activation temperature, For example, after correcting an error such as a circuit error included in each of the first and second air-fuel ratio sensors, it is possible to further correct a deviation in the output of the second air-fuel ratio sensor that occurs particularly in the vicinity of the theoretical air-fuel ratio. Therefore, the output correction of the air-fuel ratio sensor can be performed with higher accuracy.

It is a schematic diagram for demonstrating the whole structure of the system in embodiment of this invention. It is a figure for demonstrating the output characteristic of the downstream sensor in embodiment of this invention. It is a flowchart for demonstrating the control routine which a control apparatus performs in Embodiment 1 of this invention.

  Embodiments of the present invention will be described below with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and the description thereof is simplified or omitted.

Embodiment.
[Entire configuration of system of this embodiment]
FIG. 1 is a schematic diagram for explaining the overall configuration of a system according to an embodiment of the present invention. The system of FIG. 1 is used by being mounted on a vehicle or the like. In FIG. 1, a catalyst 6 is installed in the exhaust path 4 of the internal combustion engine 2. The catalyst 6 can purify exhaust gas by oxidizing carbon monoxide (CO) and hydrocarbons (HC) discharged from the internal combustion engine 2 and reducing nitrogen oxides (NOx).

  An air-fuel ratio sensor 10 (first air-fuel ratio sensor) is installed upstream of the catalyst 6 in the exhaust path 4, and an air-fuel ratio sensor 12 (second air-fuel ratio sensor) is installed downstream of the catalyst 6 in the exhaust path 4. Has been. Both the air-fuel ratio sensors 10 and 12 are limit current sensors, and are sensors that emit an output corresponding to the air-fuel ratio of the exhaust gas to be detected. In the present embodiment, it is assumed that the outputs of the air-fuel ratio sensors 10 and 12 coincide with the air-fuel ratio in order to simplify the description. However, in the present invention, the outputs of the air-fuel ratio sensors 10 and 12 have only to be correlated with the air-fuel ratio and the air-fuel ratio can be detected based on the outputs. For the sake of simplicity, in the following embodiments, the upstream air-fuel ratio sensor 10 of the catalyst 6 is also referred to as “upstream sensor”, and the downstream air-fuel ratio sensor 12 is also referred to as “downstream sensor”.

  The system of FIG. 1 includes a control device 14. The control device 14 comprehensively controls the entire system of the internal combustion engine 2. Various actuators are connected to the output side of the control device 14, and various sensors such as the air-fuel ratio sensors 10 and 12 are connected to the input side. The control device 14 receives various sensor signals, detects the air-fuel ratio of the exhaust gas, the engine speed, and other various information necessary for the operation of the internal combustion engine 2, and operates each actuator according to a predetermined control program. There are many actuators and sensors connected to the control device 14, but the description thereof is omitted in this specification. Control executed by the control device 14 in this system includes control for correcting the output of the downstream sensor 12.

[Outline of control in this embodiment]
By the way, in the air-fuel ratio control of the internal combustion engine 2, the output of the downstream sensor 12 may be used together with the output of the upstream sensor 10. In the control for determining the deterioration of the catalyst, the output of the upstream sensor 10 and the downstream sensor 12 are compared to compare the change in the air-fuel ratio upstream of the catalyst 6 and the change in the air-fuel ratio downstream of the catalyst 6. Thus, the presence or absence of deterioration of the catalyst 6 is determined.

  In these controls, when there is a deviation between the outputs of the upstream sensor 10 and the downstream sensor 12, the accuracy of the control may be reduced. In the present embodiment, output correction of the upstream sensor 10 and the downstream sensor 12 is executed in order to suppress a decrease in control accuracy due to such output deviation.

  First, the outputs of the upstream sensor 10 and the downstream sensor 12 may include a shift such as a circuit error due to an initial stage or deterioration with time. When an output shift caused by such a circuit error or the like occurs, an output point (stoichiometric point) for the stoichiometric air-fuel ratio gas shifts, resulting in an output shift over the entire air-fuel ratio.

  Therefore, first, the deviation of the stoichiometric point between the upstream sensor 10 and the downstream sensor 12 is corrected as follows. In the state before the activation of the catalyst 6, exhaust gas having the same air-fuel ratio flows around the catalyst 6. Therefore, the difference between the output of the upstream sensor 10 and the output of the downstream sensor 12 is detected in this state before activation. In accordance with this difference, a reference correction value for the upstream sensor 10 and the downstream sensor 12 is calculated, thereby correcting the output of the upstream sensor 10 and the output of the downstream sensor 12. Thereby, the output deviation due to the circuit error or the like of the upstream sensor 10 or the downstream sensor 12 is corrected.

[Characteristic control in this embodiment]
In the present embodiment, after correcting the deviation of the stoichiometric point, the output of the downstream sensor 12 is corrected based on the output of the upstream sensor 10 in the following region.

  For example, when the upstream sensor 10 or the downstream sensor 12 leaks oxygen from the atmosphere due to airtight leakage, the output may be shifted. However, the exhaust gas upstream of the catalyst 6 to be detected by the upstream sensor 10 has a high concentration of each component that affects the sensor output. Therefore, even if an airtight leak occurs in the upstream sensor 10, the concentration change due to the oxygen leak is small, and the influence of the airtight leak hardly appears in the output.

  In addition, when the air-fuel ratio of the exhaust gas is largely biased to rich or lean, or when the exhaust gas amount is large as a whole, since there are many components of the exhaust gas on the downstream side of the catalyst 6, the concentration change due to airtight leakage is It will be small. Therefore, in the region where the air-fuel ratio is rich or lean, or in the region where the exhaust gas amount is large, it is considered that the influence of the airtight leak is also very small for the downstream sensor 12.

  On the other hand, when the air-fuel ratio is in the region near the stoichiometric air-fuel ratio, the concentration of exhaust gas downstream of the catalyst 6 is extremely low. In particular, when the exhaust gas amount is a small region as a whole, the concentration change of the exhaust gas increases due to airtight leakage downstream of the catalyst 6. Therefore, in such a region, it is conceivable that the output of the downstream sensor 12 is deviated even if the amount of oxygen leakage due to airtight leakage is slight.

  FIG. 2 is a diagram for explaining an output shift at the time of oxygen leak of the downstream sensor 12 in the embodiment of the present invention. In FIG. 2, the horizontal axis represents the actual air-fuel ratio, and the vertical axis represents the air-fuel ratio value based on the output of the downstream sensor 12. Further, in the figure, a plot of ▲ represents the first measurement value based on the output of the downstream sensor 12, and a plot of x represents the second measurement value. As shown in FIG. 2, when there is an oxygen leak in the downstream sensor 12, the output value of the downstream sensor 12 is shifted to the lean side as a whole near the theoretical air-fuel ratio.

  As described above, when an air-tight leak occurs in the air-fuel ratio sensor, the influence on the output due to the air-tight leak is the output of the downstream sensor 12 particularly in the vicinity of the theoretical air-fuel ratio and in a specific operation region with a low air amount. Appears easily. Therefore, in this embodiment, in this specific region, the output of the downstream sensor 12 is corrected based on the output of the upstream sensor 10 in particular.

  In the present embodiment, specifically, a predetermined range near the theoretical air-fuel ratio is set to a range of 14.6 ± 0.2. Moreover, let the operation area | region of a low air quantity be an idle operation state. When these operation region conditions are satisfied, the output of the downstream sensor 12 is corrected based on the output of the upstream sensor 10.

  As a specific correction method, for example, the output of the upstream sensor 10 (hereinafter also referred to as “upstream output”) and the output of the downstream sensor 12 (hereinafter also referred to as “downstream output”) are detected a plurality of times in the above-described region. To do. Note that the outputs of the sensors 10 and 12 detected here take into account the delay of the volume of the exhaust path 4 between the upstream sensor 10 and the downstream sensor 12. That is, for example, when an upstream output is detected at a time t1 at a certain time, the downstream output is detected at a time t2 when the exhaust gas to be detected reaches the downstream sensor 12 at the time t1. In this time, the upstream output at time t1 is compared with the downstream output at time t2. Here, it is assumed that the difference between the times t1 and t2, that is, the output delay of the downstream sensor 12, is obtained in advance and stored in the control device 14.

After detecting the upstream output and the downstream output a plurality of times in this way, an output ratio (upstream output / downstream output) that is a ratio of the upstream output to the downstream output is calculated. This output ratio is further calculated a plurality of times, and an average value of the output ratios for a plurality of times is obtained. The average value of the output ratio is a correction coefficient (output correction value) for the output of the downstream sensor 12. After the correction coefficient is calculated, when the operation area is in the above-described area, the downstream output is corrected by the correction coefficient according to the following equation (1).
Downstream output after correction = downstream output x correction factor (1)

  Further, in the present embodiment, the correction coefficient is calculated once for each one-trip operation from the start to the stop of the internal combustion engine 2, and after the correction coefficient is calculated, until the internal combustion engine 2 is stopped, The output of the downstream sensor 12 is corrected by the calculated correction coefficient.

[Specific Control of this Embodiment]
FIG. 3 is a flowchart for illustrating a control routine executed by the control device in the embodiment of the present invention. The routine of FIG. 3 is repeatedly executed at regular intervals during the operation of the internal combustion engine 2.

  In the routine of FIG. 3, it is first determined whether or not the precondition is satisfied (S102). The precondition is stored in the control device 14 in advance, and it is determined here whether or not all the stored preconditions are satisfied. As specific preconditions, for example, the start of the internal combustion engine 2 is started, the activity of the upstream sensor 10 and the downstream sensor 12 is recognized, and the correction of the stoichiometric point deviation of the upstream sensor 10 and the downstream sensor 12 described above. Is completed. If the establishment of the precondition is not recognized in step S102, the current process ends.

  If it is determined in step S102 that the precondition is satisfied, it is next determined as a first correction condition whether or not the current operation state is an idle operation state (S104). Specifically, for example, the determination is made based on whether or not the air amount <10 is satisfied. In step S104, when it is not recognized that the vehicle is in the idling operation state, the current process ends.

  On the other hand, if it is determined in step S104 that the engine is in the idling state, then, as a second correction condition, whether or not the current output of the upstream sensor 10 is within a predetermined range near the theoretical air-fuel ratio is determined. It is determined (S106). Specifically, the predetermined range here is an air-fuel ratio range of 14.6 ± 0.2. If the second correction condition is not satisfied, the current process ends.

  On the other hand, if it is recognized in step S106 that the second correction condition is satisfied, it is next determined whether or not a correction coefficient has not been calculated (S108). In the present embodiment, the correction coefficient is calculated once for each trip of the internal combustion engine 2 from start to stop, and after the correction coefficient is calculated, the calculated correction coefficient is calculated during the trip. Thus, the output of the downstream sensor 12 is corrected. Accordingly, in step S108, it is determined whether the correction coefficient has not been calculated yet since the internal combustion engine 2 has been started this time.

  In step S108, when it is not recognized that the correction coefficient has not been calculated, that is, when the correction coefficient has already been calculated in the current trip, the output of the downstream sensor 12 is corrected by the calculated correction coefficient. (S110), and the current process ends.

  On the other hand, if it is determined in step S108 that the correction coefficient has not been calculated, then the output ratio between the upstream sensor 10 and the downstream sensor 12 is detected (S112). Specifically, the outputs of the upstream sensor 10 and the downstream sensor 12 are detected at each timing, and a value obtained by dividing the output of the upstream sensor 10 by the output of the downstream sensor 12 is detected as an output ratio.

  Next, it is determined whether or not the detection of the output ratio has been completed a required number of times (S114). For example, here, it is set to detect the output ratio 10 times continuously for calculating the correction coefficient. Therefore, in step S114, it is determined whether or not the detection of the output ratio 10 times is completed. .

  In step S114, when the detection of the output ratio is not completed, the process returns to step S112, the output of the upstream sensor 10 and the output of the downstream sensor 12 are detected again, and the output ratio is calculated.

  Thereafter, when the completion of detection of the output ratio is recognized in step S114, a correction coefficient is calculated and stored (S116). Specifically, the average value of the output ratio obtained in step S112 is obtained and stored as the correction coefficient. The stored value is cleared when the internal combustion engine 2 is stopped.

  Thereafter, the output of the downstream sensor 12 is corrected by the calculated correction coefficient (S110). Thereafter, the current process ends. In this routine, control is performed so that the output of the downstream sensor 12 is corrected (S110) only when the correction condition (S104, S106) is satisfied. That is, the correction coefficient calculated here is used only in an environment where the correction condition is satisfied.

  As described above, according to the present embodiment, when the air amount is small and the air-fuel ratio is in the vicinity of the theoretical air-fuel ratio, the output of the downstream sensor 12 can be corrected using the output of the upstream sensor 10 as a reference. it can. As a result, in an area that is highly susceptible to changes in gas concentration due to leakage or the like, the output of the upstream sensor that has a small effect can be used as a reference, so air-fuel ratio control and catalyst deterioration determination can be performed with higher accuracy. Can be executed.

  In the present embodiment, a case has been described in which the above correction is performed only when the output of the upstream sensor 10 is within a predetermined range near the stoichiometric air-fuel ratio and in an idle operation state. However, the present invention is not limited to this. When the air-fuel ratio is in the vicinity of the stoichiometric air-fuel ratio, even if the amount of air is large to some extent, the exhaust gas concentration is low downstream of the catalyst 6. Therefore, in the vicinity of the theoretical air-fuel ratio, the downstream sensor 12 is easily affected by the concentration change due to the airtight leakage. Therefore, when the air-fuel ratio is in the vicinity of the stoichiometric air-fuel ratio, the above control may be performed regardless of whether or not the engine is in the idling operation state. Further, the present invention is not limited to the case where the engine is in the idle operation state. For example, another condition that reduces the air amount to some extent may be set, and the output of the downstream sensor 12 may be corrected when the condition is satisfied. .

  In the present embodiment, the case where the output of the downstream sensor 12 is corrected by the obtained correction coefficient only when the air-fuel ratio is in a predetermined range near the stoichiometric air-fuel ratio has been described. However, the present invention is not limited to this. For example, the output of the downstream sensor 12 may be corrected using the obtained correction coefficient under all air-fuel ratios.

  Further, in the present embodiment, a case has been described in which the stoichiometric deviations of the upstream sensor 10 and the downstream sensor 12 are corrected before the activation of the catalyst 6. However, the present invention is not limited to this, and errors caused by the electrical circuits of the upstream sensor 10 and the downstream sensor 12 may be corrected in advance by other methods. Further, this correction is not limited to before the activation of the catalyst 6. Furthermore, the correction of the deviation of the stoichiometric point may not be performed.

  Further, in this embodiment, the case where the correction coefficient is the average value of the ratio (output ratio) of the upstream output to the downstream output has been described. However, the output correction value in the present invention is not limited to such an average value of the output ratio. For example, as the output correction value, the output ratio may be detected once and used. For example, the output correction value is not limited to the ratio, and the difference between the downstream output and the upstream output or the average value of the difference may be used. Good. Furthermore, another value corresponding to the difference between the downstream output and the upstream output may be used as the output correction value.

  In the present embodiment, the correction coefficient is calculated once per trip, and the output of the downstream sensor 12 is corrected with the same correction coefficient until the stop of the internal combustion engine 2 after the correction coefficient is calculated. . However, the present invention is not limited to this. For example, the output correction value may be calculated once during a plurality of trips or a plurality of times per trip. Further, the output correction value may be calculated once every predetermined operation time or operation distance, for example, instead of using the internal combustion engine 2 from start to stop.

  In the present embodiment, for the sake of convenience, it has been described that the outputs of the air-fuel ratio sensors 10 and 12 coincide with the air-fuel ratio. However, the present invention is not limited to this, and it is sufficient that the output of the air-fuel ratio sensor has a correlation with the air-fuel ratio. In this case, the output correction value may be in accordance with the difference in the outputs of the air-fuel ratio sensors 10 and 12, or may be in accordance with the difference in the air-fuel ratio based on the output. The output may be corrected, or the air-fuel ratio calculated according to the output may be corrected.

  In the above embodiment, when referring to the number of each element, quantity, quantity, range, etc., the reference is made unless otherwise specified or the number is clearly specified in principle. The invention is not limited to the numbers. Further, the structure and the like described in this embodiment are not necessarily essential to the present invention unless otherwise specified or clearly specified in principle.

2 Internal combustion engine 4 Exhaust path 6 Catalyst 10 Upstream sensor (air-fuel ratio sensor)
12 Downstream sensor (air-fuel ratio sensor)
14 Control device

Claims (7)

First detection means for detecting the output of a first air-fuel ratio sensor installed upstream of the catalyst in the exhaust path of the internal combustion engine;
Second detection means for detecting an output of a second air-fuel ratio sensor installed downstream of the catalyst in the exhaust path;
The output of the first air-fuel ratio sensor and the second air-fuel ratio when the value of the first air-fuel ratio obtained based on the output of the first air-fuel ratio sensor is within a predetermined range set near the stoichiometric air-fuel ratio. Output correction value calculating means for calculating an output correction value for the second air-fuel ratio sensor according to a difference from an output of the fuel ratio sensor;
Output correction means for correcting the output of the second air-fuel ratio sensor in accordance with the output correction value;
A correction apparatus for an air-fuel ratio sensor comprising:   The output correction means corrects the output of the second air-fuel ratio sensor according to the output correction value when the value of the first air-fuel ratio is within the predetermined range. The correction | amendment apparatus of the air-fuel ratio sensor of description.   The output correction value calculating means outputs the output of the first air-fuel ratio sensor when the value of the first air-fuel ratio is within the predetermined range and when the operation state of the internal combustion engine is a predetermined idle operation state. The correction apparatus for an air-fuel ratio sensor according to claim 1 or 2, wherein the output correction value is calculated according to a difference from an output of the second air-fuel ratio sensor.   The output correcting means is configured to output the second air-fuel ratio according to the output correction value when the value of the first air-fuel ratio is within the predetermined range and when the operating state of the internal combustion engine is the predetermined idle operating state. The correction device for an air-fuel ratio sensor according to claim 3, wherein the output of the air-fuel ratio sensor is corrected. Before the catalyst reaches the activation temperature, a reference for each of the first air-fuel ratio sensor and the second air-fuel ratio sensor according to the difference between the output of the first air-fuel ratio sensor and the output of the second air-fuel ratio sensor. A reference correction value calculating means for calculating a correction value;
Reference correction means for correcting outputs of the first air-fuel ratio sensor and the second air-fuel ratio sensor according to the reference correction value;
The air-fuel ratio sensor correction apparatus according to any one of claims 1 to 4, further comprising:   6. The output correction value calculating unit calculates the output correction value according to a ratio of the output of the first air-fuel ratio sensor to the output of the second air-fuel ratio sensor. The correction device for an air-fuel ratio sensor according to claim 1. The output correction value calculating means calculates the output correction value when the output correction value has not been calculated once after the internal combustion engine is started,
The output correction means corrects the output of the second air-fuel ratio sensor using the output correction value until the internal combustion engine is first stopped after the output correction value is calculated.
The air-fuel ratio sensor correction apparatus according to any one of claims 1 to 6,

Images