JP2008121455A - Control device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve reliability of various types of control of an internal combustion based on sensor output by quickly detecting wrong attachment of a plurality of air-fuel ratio sensors installed in an exhaust passage of an exhaust gas post-processing device to make an operator recognize it. <P>SOLUTION: The exhaust gas post-processing device 2 having an LNT 21 and a DPF 22 is installed in an exhaust passage 12 of an engine 1; and air-fuel ratio sensors 71 and 72 are arranged on its upper stream side and lower stream side, respectively; and control is executed by an ECU 6 based on output values thereof. The ECU 6 determines wrong attachment of the air-fuel ratio sensor when a heater current deviation of the air-fuel ratio sensors 71 and 72 in acceleration, or a sensor value deviation in rich spike control of the LNT 21deviates from a preset normal range. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to detection of erroneous attachment of a plurality of air-fuel ratio sensors in a control device provided with an exhaust aftertreatment device and a plurality of air-fuel ratio sensors in an exhaust passage of an internal combustion engine.

Diesel engines are effective in reducing CO ₂ , but are operated at a lean air-fuel ratio, so there are problems such as purification of NOx and emission of solid particulate matter (particulates: PM). Reduction has become a major issue. As countermeasures, in addition to improvements in combustion control technology, development of exhaust aftertreatment technology for purifying NOx and PM is being promoted.

As an exhaust aftertreatment device installed in an exhaust passage of an internal combustion engine, use of a combination of a NOx storage reduction catalyst (lean NOx trap: LNT) and a diesel particulate filter (DPF) has been studied (for example, patents). References 1 and 2). LNT is a device that occludes NOx during lean operation and reduces and purifies NOx during rich operation. To apply it to a diesel engine, a technology that temporarily creates a rich atmosphere is required. For this reason, rich spike control is known in which post-injection is performed at a predetermined cycle during lean operation, or fuel is added to exhaust gas and instantaneous rich air-fuel ratio operation is performed to reduce and purify NOx.
JP 2006-144659 A JP 2004-36552 A

Two air-fuel ratio sensors are usually attached to the exhaust passage upstream and downstream of the exhaust aftertreatment device. The upstream air-fuel ratio sensor is for correcting the fuel injection amount, and controls the air-fuel ratio so that the detected actual air-fuel ratio becomes the stoichiometric air-fuel ratio calculated according to the operating state of the engine. Etc. (see, for example, Patent Documents 1 and 3). The downstream air-fuel ratio sensor is used for LNT regeneration control, and is intended to prevent fuel consumption deterioration and white smoke by rich spike control based on the detected air-fuel ratio (see, for example, Patent Document 2). Further, for example, in order to harmonize desulfurization of LNT and regeneration of DPF, an LNT is disposed downstream of the DPF, and an air-fuel ratio sensor is disposed upstream and downstream of the LNT and DPF, respectively. There is also known a system for controlling to be within a predetermined range (see, for example, Patent Document 4).
Japanese Patent Laid-Open No. 2002-130009 JP 2005-133721 A

  By the way, the plurality of air-fuel ratio sensors attached before and after the exhaust aftertreatment device have the same specifications for the sensor structure including the connector shape and the sensor characteristics, and the attachment positions are close. For this reason, there is a concern that the position of the air-fuel ratio sensor is attached in the reverse direction.

  If a plurality of air-fuel ratio sensors are attached in reverse, the air-fuel ratio recognized by the ECU will be mistaken, and the control based on that will not be performed properly. As a result, exhaust emission not only deteriorates, but there is a possibility that problems such as water cracking of the sensor element due to the start of energization of the temperature control heater of the air-fuel ratio sensor being too early may occur.

  Accordingly, the present invention can quickly detect erroneous attachment of a plurality of air-fuel ratio sensors installed in the exhaust passage of the exhaust aftertreatment device and allow the driver to recognize the various control of the internal combustion engine based on the sensor output. The object is to improve the reliability and prevent problems such as deterioration of exhaust gas and moisture cracking of sensor elements.

  An internal combustion engine control apparatus according to a first aspect of the present invention includes an exhaust aftertreatment device installed in an exhaust passage of a vehicle internal combustion engine, and a plurality of air-fuel ratio sensors respectively installed on an upstream side and a downstream side of the exhaust aftertreatment device. The control unit performs control based on the output values of the plurality of air-fuel ratio sensors, and is provided with erroneous attachment detection means for detecting erroneous attachment of the plurality of air-fuel ratio sensors. The erroneous attachment detection means detects the current values of the temperature control heaters provided in the plurality of air-fuel ratio sensors in an operating state in which the exhaust flow rate increases rapidly, and downstream from the heater current values of the upstream air-fuel ratio sensors. When the sensor current value deviation obtained by subtracting the heater current value deviates from the preset normal range, it is determined that the plurality of air-fuel ratio sensors are erroneously attached.

  When the exhaust gas flow rate rapidly increases, the upstream air-fuel ratio sensor is first cooled to lower the temperature, and then the downstream air-fuel ratio sensor lowers in temperature. Since the control device increases the heater energization amount so that the sensor elements reach the target temperature, the heater current values of these sensors change with a delay. Therefore, by knowing in advance the heater current value change at this time, and comparing the deviation of the detected heater current value with the normal value, it is possible to detect erroneous attachment. Therefore, it is possible to reduce the influence on various controls based on the air-fuel ratio, to prevent controllability due to erroneous detection, deterioration of exhaust emission, cracking of the sensor, etc., and to improve reliability.

  In the control device according to claim 2 of the present invention, the operating state in which the exhaust flow rate in the erroneous attachment detecting means increases rapidly is the accelerated operating state of the internal combustion engine.

  During acceleration operation, the exhaust gas flow rate increases rapidly, so that a difference in the element temperature of the air-fuel ratio sensor tends to occur. Accordingly, it is possible to easily detect erroneous attachment by calculating the deviation of the heater current value for temperature control.

  The invention of claim 3 of the present invention discloses another device configuration for solving the problems of the present invention, wherein the erroneous attachment detecting means is configured to detect the plurality of empty air-fuel ratios in an operating state in which the air-fuel ratio changes suddenly. When the sensor value deviation obtained by subtracting the downstream air-fuel ratio from the upstream air-fuel ratio detected by the fuel ratio sensor deviates from the preset normal range, it is determined that the plurality of air-fuel ratio sensors are erroneously attached.

  For example, when fuel is added to the exhaust gas, first, the air-fuel ratio detected by the upstream air-fuel ratio sensor rapidly decreases, and then the detection value of the downstream air-fuel ratio sensor rapidly decreases. Therefore, it is possible to detect erroneous attachment by knowing in advance the delay of the sensor detection value change at this time and comparing the deviation of the detected sensor value with the normal value. Even in this case, it is possible to reduce the influence on various controls based on the air-fuel ratio, to prevent controllability due to erroneous detection, deterioration of exhaust emission, sensor water cracking, and the like, and to improve reliability.

  In the control device according to claim 4 of the present invention, the operation state in which the exhaust flow rate in the erroneous attachment detection means increases rapidly is a rich spike control operation state in which the stoichiometric air-fuel ratio or the rich air-fuel ratio is temporarily set during the lean operation. .

  When rich spike control is performed, fuel is added to the exhaust gas, and the air-fuel ratio is rapidly reduced, resulting in a difference in the detected value of the air-fuel ratio sensor. Therefore, it is possible to easily detect erroneous attachment by calculating the deviation of the sensor detection value.

  In the control device according to claim 5 of the present invention, the rich spike control makes the air-fuel ratio rich by post-injection or fuel addition from a fuel addition valve provided in the exhaust passage.

  Specifically, the air-fuel ratio can be made rich by periodically performing post injection or by adding fuel by providing a fuel addition valve in the exhaust passage.

  The control device according to claim 6 of the present invention includes a NOx occlusion reduction catalyst or a particulate filter as the exhaust aftertreatment device.

  For example, in an apparatus equipped with a NOx occlusion reduction catalyst, fuel injection is controlled by an air-fuel ratio sensor arranged upstream thereof, and at the time of regeneration, rich spike control is performed based on an air-fuel ratio sensor value mounted on the downstream side. The effect of applying the present invention is high. In addition, the present invention also detects erroneous attachment in devices that are equipped with a particulate filter and an air-fuel ratio sensor is installed downstream of the particulate filter, or in a device that performs control based on the detection value of the air-fuel ratio sensor installed before and after the particulate filter. can do.

  The control device according to claim 7 of the present invention corrects the fuel injection amount based on the detection value of the upstream air-fuel ratio sensor.

  For example, by estimating the oxygen concentration during combustion of the internal combustion engine from the detection value of the air-fuel ratio sensor arranged upstream of the exhaust aftertreatment device, and correcting the fuel injection amount so that the optimum oxygen concentration is achieved, the smoke reduction effect Is obtained.

  The control device according to claim 8 of the present invention performs regeneration control of the exhaust aftertreatment device based on a detection value of the downstream air-fuel ratio sensor.

  For example, an apparatus equipped with a NOx occlusion reduction catalyst needs to have a stoichiometric air-fuel ratio or a rich atmosphere during regeneration. By controlling the amount of fuel added based on the downstream air-fuel ratio sensor value, fuel consumption deterioration and white smoke can be reduced. The effect of preventing is obtained.

  According to a ninth aspect of the present invention, the apparatus includes a recognition value switching means for switching the recognition values of the upstream air-fuel ratio and the downstream air-fuel ratio when the erroneous attachment detection means determines that the attachment is incorrect.

  It is desirable to immediately return the attachment position to normal after detection of erroneous attachment. However, as a measure up to that time, the recognition value is exchanged inside the control device to make it self-normalized and controllable in a pseudo manner. Thereby, the influence of incorrect attachment can be reduced and deterioration of controllability can be prevented.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, a first embodiment of the invention will be described with reference to the drawings. FIG. 1 shows the overall configuration of a control device for an internal combustion engine to which the present invention is applied. In the present embodiment, an example of application to a four-cylinder diesel engine 1 will be described. Each cylinder of the engine 1 is provided with an injector 11, and an exhaust aftertreatment device 2 is installed in an exhaust passage 12 following the exhaust manifold. As shown in FIG. 2A, the exhaust aftertreatment device 2 includes a NOx storage reduction catalyst (hereinafter referred to as LNT) 21 and a diesel particulate filter (hereinafter referred to as DPF) 22 in series in this order. is set up.

Intake is introduced into each cylinder combustion chamber from the intake passage 13 through the intake manifold. The fuel is pumped from the fuel tank 4 to the common rail 3 that supplies fuel to the injector 11 via the metering valve 41 and the pump 31 so that the pressure of the common rail 3 detected by the pressure sensor 5 becomes a predetermined pressure. The ECU 6 is controlling.
An air flow meter 14 is installed in the intake passage 13 of the engine 1 to detect the amount of intake air and output it to the ECU 6.

LNT has a generally known structure. For example, the catalyst and NOx storage material are supported on a catalyst support having a honeycomb structure. During normal operation in a lean atmosphere, NOx is temporarily stored in the NOx storage material in the form of nitrate, and then released when it becomes a stoichiometric air-fuel ratio or rich atmosphere, and is reduced and purified to harmless N ₂ or the like by the catalyst. Since the diesel engine is operated in a lean atmosphere, rich spike control that temporarily creates a rich atmosphere by adding exhaust fuel is performed to purify NOx and regenerate LNT.

  The DPF 22 has a generally known structure, and has a large number of cells in the porous ceramic honeycomb structure as gas flow paths and is sealed so that the upstream side or the downstream side are staggered. The exhaust after combustion contains particulate PM (particulates) mainly composed of soot (carbon) and SOF (soluble organic component), and the PM discharged into the exhaust passage 12 is exhaust gas. While flowing through the DPF 22, it is collected by the porous partition walls that partition each cell and gradually accumulates. The collected PM is burned and removed by periodically heating and regenerating the DPF 22.

  For example, the DPF 22 may be a DPF with a catalyst carrying an oxidation catalyst. The oxidation catalyst is applied to the inner surface (porous partition wall surface) of the DPF 2 and promotes the oxidation of the collected PM. If the catalytic reaction is used in this way, the regeneration temperature of the DPF 2 can be lowered and stable combustion can be realized.

  In the exhaust passage 12, an air-fuel ratio sensor 71 is installed immediately upstream of the exhaust aftertreatment device 2, and an air-fuel ratio sensor 72 is installed immediately downstream. These air-fuel ratio sensors 71 and 72 have a generally known structure and include a sensor element capable of linearly detecting the air-fuel ratio and a temperature control heater having a heating element. The air-fuel ratio sensors 71 and 72 are connected to the ECU 6, detect the air-fuel ratios immediately upstream and immediately downstream of the exhaust aftertreatment device 2, and output them to the ECU 6. The detection value of the upstream air-fuel ratio sensor 71 is recognized as an upstream sensor value, and the detection value of the downstream air-fuel ratio sensor 72 is recognized as a downstream sensor value. A rich spike control fuel addition valve 73 is installed at the most upstream position of the exhaust passage 12. Or it is good also as a structure which performs rich spike control by the post injection from the injector 11. FIG.

  Further, a differential pressure sensor 8 is installed in the exhaust passage 12 to know the differential pressure across the DPF 2. One end of the differential pressure sensor 8 is connected to the exhaust passage 12 immediately upstream of the DPF 2 via the pressure introduction passage 81, and the other end is connected to the exhaust passage 12 immediately downstream of the DPF 2 via the pressure introduction passage 82. The pressure sensor 8 outputs a signal corresponding to the differential pressure across the DPF 2 to the ECU 6.

  Further, various sensors such as an accelerator opening sensor, a rotation speed sensor, and an exhaust temperature sensor (not shown) are connected to the ECU 6. The ECU 6 calculates the optimum fuel injection amount, injection timing, injection pressure, etc. according to the operating state based on the detection signals from these sensors, and the common rail 3 detected by the pressure sensor 5 becomes a predetermined injection pressure. In this manner, the metering valve 41 is controlled so that high-pressure fuel is fed to the common rail 3 and the injector 11 is driven at a predetermined timing to inject fuel into the engine 1.

At this time, the ECU 6 performs feedback control for correcting the fuel injection amount based on the detection value of the upstream air-fuel ratio sensor 71. First, the ECU 6 reads the detection results of the various sensors and compares them with map values stored in advance to calculate a basic fuel injection amount corresponding to the current engine operating state. Further, the O ₂ concentration in the engine combustion chamber is estimated from the value detected by the upstream air-fuel ratio sensor 71, and the correction amount of the basic fuel injection amount is calculated based on the deviation between this estimated value and the target O ₂ concentration. Set the fuel injection amount. By correcting the fuel injection amount according to the actual air-fuel ratio in this way, smoke can be reduced.

The ECU 6 also controls regeneration of the LNT 21 and the DPF 22.
The NOx occluded in the LNT is reduced and purified by performing rich spike control that temporarily performs rich operation at a predetermined cycle during lean operation. For example, the ECU 6 sets the lean operation time and the rich operation time to a predetermined ratio, calculates the target air-fuel ratio at each operation, and starts the lean operation at the predetermined air-fuel ratio. When a predetermined lean operation period is reached, an execution flag for performing rich spike control is set, the target air-fuel ratio at the time of rich is set, and the fuel addition valve 73 is driven to add fuel to the exhaust passage 12. Alternatively, in a configuration that does not include the fuel addition valve 73, fuel can be added to the exhaust gas by using the fuel injection from the injector 11 as two-stage injection of main injection and post injection.

  At this time, in order to perform the rich spike control appropriately, the fuel addition amount (rich spike amount) is feedback controlled based on the detection value of the downstream air-fuel ratio sensor 72. Since the rich spike control involves fuel consumption, there is a concern that fuel consumption may deteriorate due to excessive fuel being added to the exhaust, but it is necessary for the reduction purification of NOx from the downstream air-fuel ratio detected by the air-fuel ratio sensor 72. By calculating an appropriate amount of reducing agent (fuel amount) and using the optimal amount of rich spike, it is possible to prevent deterioration of fuel consumption. Moreover, the white smoke prevention effect by unburned fuel is also acquired.

  Further, the ECU 6 monitors the PM accumulation state on the DPF 22 based on the differential pressure across the DPF detected by the differential pressure sensor 8. This utilizes the fact that the pressure loss in the DPF 22 increases as the PM deposition amount increases. By modeling the relationship between the differential pressure across the DPF and the PM deposition amount in advance with respect to the exhaust flow rate, the PM deposition amount is reduced. Can be calculated. Then, the ECU 6 compares the calculated value of the PM accumulation amount with a reference value for starting the regeneration of the DPF 22, and determines whether regeneration is necessary.

  When the calculated value of the PM accumulation amount exceeds the reference value, the ECU 6 operates the temperature raising means to raise the DPF 22 to a predetermined target regeneration temperature (for example, 600 ° C. ± 50 ° C.) and burn and remove the PM. As the temperature raising means, for example, post-injection, intake throttle, fuel injection timing retardation, etc. are used, and the unburnt fuel is oxidized and the exhaust temperature is raised by the reaction heat. The ECU 6 feedback-controls the DPF temperature so that the DPF 22 is maintained at the target regeneration temperature.

  At this time, in order to prevent melting of the DPF 22 base material and the like, the reference value for determining regeneration is set to an accumulation amount that does not cause the temperature of the DPF 22 to rise excessively due to PM combustion. Further, in an operation state where the exhaust gas is naturally burned at a high temperature as in a high load, the air-fuel ratio of the exhaust gas can be controlled to a predetermined value or less so that the PM does not burn at once and the temperature rises excessively. For example, the intake air amount is feedback controlled based on the downstream air-fuel ratio detected by the air-fuel ratio sensor 72.

  As shown in FIG. 2A, the exhaust aftertreatment device 2 may have various configurations shown in FIGS. 2B to 2D in addition to the configuration in which the LNT 21 and the DPF 22 are integrated. FIG. 2B shows an example in which the LNT 21 and the DPF 22 are provided independently, and the air-fuel ratio sensors 71 and 72 are arranged before and after the LNT 21. Further, as shown in FIG. (DOC) 23 can also be provided. Alternatively, as shown in FIG. 2D, an exhaust aftertreatment device 2 'in which the DOC 23 and the DPF 22 are integrated may be provided, and the LNT 21 may be disposed upstream thereof. In these examples, the two air-fuel ratio sensors 71 and 72 are arranged before and after the LNT 21, but an air-fuel ratio sensor may be further arranged, for example, downstream of the DPF 22 according to necessary control.

  Next, the erroneous attachment detection means for the air-fuel ratio sensors 71 and 72, which is a feature of the present invention, will be described. As described above, the upstream air-fuel ratio and the downstream air-fuel ratio detected by the air-fuel ratio sensors 71 and 72 are used for various controls such as correction of the fuel injection amount and regeneration of the exhaust aftertreatment device 2. The detection values of the sensors 71 and 72 need to be correctly recognized by the ECU 6. In particular, when the DPF 22 is provided, PM may be oxidized or oxygen may be purged in the DPF 22, and in such a state, as shown in FIG. The detected value (downstream sensor value) of the downstream air-fuel ratio sensor 71 shifts to the rich side with respect to the detected value of 71 (upstream sensor value). As described above, when the upstream air-fuel ratio sensor 71 is used for smoke reduction, the air-fuel ratio delay (time constant) between the engine combustion chamber and the upstream air-fuel ratio sensor 71 is taken into consideration. Therefore, in order to accurately estimate the air-fuel ratio in the combustion chamber, it must be mounted at the correct position.

  However, since the air-fuel ratio sensors 71 and 72 have the same sensor structure and sensor characteristics, the air-fuel ratio sensors 71 and 72 may be reversed when they are installed. In this case, the air-fuel ratio used as a reference for rich spike control or air-fuel ratio estimation There will be a shift in the sensor value and also in the time constant for air-fuel ratio estimation. For this reason, there is a risk that exhaust gas may deteriorate due to fuel consumption deterioration or white smoke problems during rich spike control, or due to a deviation in the correction amount of the fuel injection amount.

  Therefore, in the present invention, erroneous attachment detection means is provided in the ECU 6 so that the driver can be warned promptly of the occurrence of erroneous attachment. Specifically, the erroneous attachment detection means detects the current values of the temperature control heaters provided in the air-fuel ratio sensors 71 and 72, respectively, in an operating state where the exhaust flow rate increases rapidly. The erroneous attachment detection means determines erroneous attachment depending on whether or not the sensor current value deviation obtained by subtracting the downstream heater current value from the heater current value of the upstream air-fuel ratio sensor is within a preset normal range. The operating state in which the exhaust flow rate increases rapidly is, for example, an acceleration operating state of the internal combustion engine.

  Alternatively, the erroneous attachment detection means is configured so that a sensor value deviation obtained by subtracting the downstream air-fuel ratio from the upstream air-fuel ratio detected by the air-fuel ratio sensors 71 and 72 in a driving state where the air-fuel ratio changes suddenly is a preset normal range. It is also possible to determine erroneous attachment depending on whether or not The operation state in which the exhaust flow rate increases rapidly is, for example, a rich spike control operation state.

  Next, details of the erroneous attachment detection control executed by the ECU 6 will be described. FIG. 3A is a flowchart of erroneous attachment detection control. Steps S1 and S2 are erroneous attachment determination procedures based on the heater current values of the air-fuel ratio sensors 71 and 72. Steps S3 and S4 are air-fuel ratio sensors 71 and 72, respectively. 7 shows an erroneous attachment determination procedure based on 72 detection values. First, in step S1, it is determined whether or not acceleration is being performed. The determination during acceleration is performed by, for example, comparing an increase in the intake air amount (Δ air amount) detected by the air flow meter 14 with a predetermined value A (g / s), and Δ air amount> A (g / If s), it is determined that the vehicle is accelerating, and the process proceeds to step S2.

In step S2, the heater current values of the air-fuel ratio sensors 71 and 72 are detected, their deviations (front and rear sensor current deviations) are calculated, and compared with the reverse attachment determination value α.
Front / rear sensor current deviation = upstream heater current value−downstream heater current value As shown in the time chart of FIG. 4, during acceleration, the exhaust flow rate increases as the engine speed increases, and the air-fuel ratio sensors 71 and 72 The sensor element is cooled by the inflowing air, so that the surface temperature is lowered. Here, the air-fuel ratio sensors 71 and 72 perform feedback control using a temperature control heater so that the surface temperature of the sensor element becomes an active temperature (for example, about 700 ° C.). It is known that the surface temperature of the sensor element has a correlation with the impedance of the detection unit, and by controlling the energization to the temperature control heater so that the surface temperature (impedance) becomes the target temperature (impedance), The surface temperature rises again. Along with this, the heater current value also increases.

  At this time, due to the difference in the mounting position, a difference occurs in the change in the heater current value between the air-fuel ratio sensor 71 on the upstream side of the LNT 21 and the air-fuel ratio sensor 72 on the downstream side as shown in the figure. That is, the heater current value of the upstream air-fuel ratio sensor 71 changes first, and the heater current value of the downstream air-fuel ratio sensor 72 changes with a delay. Therefore, as indicated by the solid line in the figure, when the sensor is normally mounted, the value of the sensor current deviation before and after the acceleration continues to be + (plus) for a certain period.

However, when the air-fuel ratio sensors 71 and 72 are attached in reverse, the upstream heater current value and the downstream heater current value are switched. For this reason, as shown by a dotted line in the figure, the sensor current deviation before and after the acceleration is a negative value. The present invention uses the difference in the rise of the heater current value, and whether the front-rear sensor current deviation is less than a preset reverse attachment determination value α (<0) as an index for detecting erroneous attachment. Determine. And if the following formula is affirmed,
Front-rear sensor current deviation <reverse mounting judgment value α (mA / s)
It determines with reverse attachment, and progresses to step 5. At this time, the incorrect attachment may be determined depending on whether or not the state where the reverse attachment determination value α is lower than the reverse attachment continuation time T (s).

If a negative determination is made in steps S1 and 2, the process proceeds to step S3. In step S3, it is determined whether the fuel addition execution flag for the rich spike control of the LNT 21 is switched from OFF to ON and within the time B (s). If an affirmative determination is made in step S3, the process proceeds to step S4, where a deviation (front-rear sensor value deviation) between the detection value of the air-fuel ratio sensor 71 and the detection value of the air-fuel ratio sensor 72 is calculated and compared with the reverse attachment determination value β. .
Front and rear sensor value deviation = upstream sensor value−downstream sensor value As shown in FIG. 5, the ECU 6 periodically performs rich spike control to add fuel from the fuel addition valve 73 to the exhaust. As a result, the air-fuel ratio in the exhaust gas periodically changes accordingly. That is, by adding fuel, first, the air-fuel ratio (sensor value) detected by the upstream air-fuel ratio sensor 71 is suddenly decreased and then rapidly increased. The air-fuel ratio (sensor value) detected by the downstream-side air-fuel ratio sensor 72 decreases rapidly in the same manner and then increases rapidly and repeats this.

Therefore, as shown by the solid line in the figure, the sensor value deviation at the beginning and after the addition becomes − (minus) when it is normally attached, decreases to a certain value, then starts to rise, and further + (plus) value After that, it decreases and converges to the zero point. In the case of reverse attachment, as shown by the dotted line in the figure, the deviation value curve in which the positive and negative signs are reversed is followed. Therefore, it is also possible to detect erroneous attachment by calculating the front / rear sensor value deviation within a certain time B (s) from the fuel addition and determining whether or not the predetermined reverse attachment determination value β (> 0) is exceeded. it can. And if the following formula is affirmed,
Front / rear sensor value deviation> Reverse mounting judgment value β
It determines with reverse attachment, and progresses to step 5.

  In step 5, an erroneous attachment determination flag is turned on, and a failure warning lamp (MIL) is turned on to allow the driver to recognize it. After detecting the erroneous attachment, it is desirable to quickly move the vehicle to a dealer or the like so that the attachment of the air-fuel ratio sensors 71 and 72 is set to the normal position. Each learning value that uses is cleared, and deterioration of controllability due to an incorrect learning value is prevented. Alternatively, the recognition value in the ECU 6 can be changed so that it becomes a pseudo-normal value and can be self-normalized and used, and the influence of erroneous mounting can be minimized. At this time, for example, when the control value changes greatly by exchanging the detection value, the detection value may be gradually changed until it becomes a normal value. Thereby, the malfunction which arises by switching immediately can be eliminated.

  As described above, according to the present invention, erroneous attachment of the air-fuel ratio sensors 71 and 72 can be easily detected and recognized by the driver. Therefore, rich spike control based on the air-fuel ratio and control of fuel injection amount correction are performed. It is possible to prevent problems such as deterioration of fuel consumption, exhaust emission, and water cracking of the sensor element due to deterioration in performance.

1 is an overall schematic configuration diagram of an internal combustion engine control apparatus to which the present invention is applied. (A)-(d) is a figure which shows the example of a structure of an exhaust-gas aftertreatment apparatus, and the attachment position of an air fuel ratio sensor. (A) is a flowchart of the erroneous attachment detection control executed in the ECU, and (b) is a diagram showing the deviation of the downstream air-fuel ratio sensor value. It is a time chart for demonstrating the erroneous attachment detection by a sensor electric current deviation. It is a time chart for demonstrating the erroneous attachment detection by an air fuel ratio sensor value deviation.

Explanation of symbols

1 engine (internal combustion engine)
DESCRIPTION OF SYMBOLS 11 Injector 12 Exhaust pipe 13 Intake pipe 14 Air flow meter 2 Exhaust post-processing apparatus 21 DPF (particulate filter)
22 LNT (NOx storage reduction catalyst)
3 Common rail 4 Fuel tank 5 Pressure sensor 6 ECU
71 Air-fuel ratio sensor 72 Air-fuel ratio sensor 73 Fuel addition valve 8 Differential pressure sensor

Claims (9)

An exhaust aftertreatment device installed in an exhaust passage of a vehicle internal combustion engine;
A plurality of air-fuel ratio sensors respectively installed on the upstream side and downstream side of the exhaust aftertreatment device;
In a control device for an internal combustion engine that performs control based on output values of the plurality of air-fuel ratio sensors,
Providing erroneous attachment detection means for detecting erroneous attachment of the plurality of air-fuel ratio sensors,
The erroneous attachment detection means detects the current values of the temperature control heaters provided in the plurality of air-fuel ratio sensors in an operating state in which the exhaust gas flow rate rapidly increases, and downstream from the heater current values of the upstream air-fuel ratio sensors. A control apparatus for an internal combustion engine, wherein when the sensor current value deviation obtained by subtracting the heater current value deviates from a preset normal range, it is determined that the plurality of air-fuel ratio sensors are erroneously attached.   2. The control device for an internal combustion engine according to claim 1, wherein the operation state in which the exhaust flow rate in the erroneous attachment detection means increases rapidly is an acceleration operation state of the internal combustion engine. An exhaust aftertreatment device installed in an exhaust passage of a vehicle internal combustion engine;
A plurality of air-fuel ratio sensors respectively installed on the upstream side and downstream side of the exhaust aftertreatment device;
In a control device for an internal combustion engine that performs control based on output values of the plurality of air-fuel ratio sensors,
Providing erroneous attachment detection means for detecting erroneous attachment of the plurality of air-fuel ratio sensors,
In the operation state where the air-fuel ratio changes abruptly, the erroneous attachment detection means has a preset normal sensor value deviation obtained by subtracting the downstream air-fuel ratio from the upstream air-fuel ratio detected by the plurality of air-fuel ratio sensors. A control device for an internal combustion engine, characterized in that, when out of range, it is determined that the plurality of air-fuel ratio sensors are erroneously attached.   4. The control device for an internal combustion engine according to claim 3, wherein the operating state in which the exhaust flow rate suddenly increases in the erroneous attachment detecting means is a rich spike control operating state in which a stoichiometric air-fuel ratio or a rich air-fuel ratio is temporarily set during lean operation.   5. The control device for an internal combustion engine according to claim 4, wherein the rich spike control controls the air-fuel ratio by post injection or fuel addition from a fuel addition valve provided in an exhaust passage.   The control apparatus for an internal combustion engine according to any one of claims 1 to 5, further comprising a NOx occlusion reduction catalyst or a particulate filter as the exhaust aftertreatment device.   The control apparatus for an internal combustion engine according to claim 6, wherein the fuel injection amount is corrected based on a detection value of the upstream air-fuel ratio sensor.   The control device for an internal combustion engine according to claim 6, wherein regeneration control of the exhaust aftertreatment device is performed based on a detection value of the downstream air-fuel ratio sensor.   The recognition value switching means according to any one of claims 1 to 8, further comprising recognition value switching means for exchanging recognition values of the upstream air-fuel ratio and the downstream air-fuel ratio when the erroneous attachment detection means determines that the attachment is incorrect. An exhaust purification device for an internal combustion engine.