JP4034697B2 - Failure detection device for exhaust secondary air supply device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a failure detection device for an exhaust secondary air supply device.
[0002]
[Prior art]
The exhaust secondary air supply device includes, for example, an air supply pipe and an air pump connected to an upstream position of a catalyst device disposed in an exhaust system of the internal combustion engine. The exhaust secondary air is driven from the air supply pipe by driving the air pump. Introduce to promote combustion and reduce unburned components in the exhaust.
[0003]
In the exhaust secondary air supply device, when a failure such as breakage of the air supply pipe occurs, the intended function is not achieved. Therefore, various failure detection methods have been proposed, and examples thereof are described in Patent Document 1. The technology has been proposed.
[0004]
[Patent Document 1]
Japanese Patent Laid-Open No. 5-26033
In the technique described in Patent Literature 1, an air supply pipe that is connected to an air pump driven by an internal combustion engine and supplies secondary air to the upstream side of the catalyst device, and its opening degree are adjusted to adjust the secondary air supply amount. In the exhaust secondary air supply device including a control valve for controlling the air, the exhaust secondary air is intermittently supplied in a predetermined diagnostic operation region, and an air-fuel ratio sensor (O2 sensor) disposed between the air supply position and the catalyst device The failure is detected by determining whether or not the output of () is reversed in accordance with intermittent supply.
[0006]
[Problems to be solved by the invention]
As described above, in the prior art, in order to detect a failure with high accuracy, it is necessary to learn and confirm the output of the air-fuel ratio sensor when the exhaust secondary air supply device is normal. As a result, failure detection is delayed. Such inconvenience is particularly noticeable when an exhaust system is provided for each bank as in a V-type engine.
[0007]
Accordingly, an object of the present invention is to provide a failure detection device for an exhaust secondary air supply device that solves the above-described problems and detects a failure of the exhaust secondary air supply device easily and accurately.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, according to claim 1, a failure detection device for an exhaust secondary air supply device for supplying exhaust secondary air to an upstream position of a catalyst device arranged in an exhaust system of an internal combustion engine. The air-fuel ratio sensor that generates an output corresponding to the oxygen concentration in the exhaust gas flowing through the exhaust system, and when the exhaust secondary air is supplied, is calculated at the first time tn based on the output of the air-fuel ratio sensor. A first difference between the air-fuel ratio feedback correction coefficient and the air-fuel ratio feedback correction coefficient calculated at the second time tn + o after the first predetermined time o has elapsed from the first time tn. Correction coefficient difference calculation means, first comparison means for comparing the calculated first difference with a first predetermined value, an air-fuel ratio feedback correction coefficient calculated at the first time tn, and the second time 2nd place from tn + o Second correction coefficient difference calculating means for calculating a second difference from the air-fuel ratio feedback correction coefficient calculated at the third time tn + o + p after the time p has elapsed, and calculating the calculated second difference to the second A second comparison means for comparing with a predetermined value and a failure detection means for detecting a failure of the exhaust secondary air supply device based on the comparison results output by the first and second comparison means are provided. .
[0009]
When the exhaust secondary air is supplied, the air-fuel ratio feedback correction coefficient calculated at the first time tn based on the output of the air-fuel ratio sensor and the first predetermined time o after the first time tn have elapsed. The first difference from the air-fuel ratio feedback correction coefficient calculated at time tn + o of 2 is calculated, the calculated first difference is compared with a first predetermined value, and calculated at the first time tn. A second difference is calculated between the air-fuel ratio feedback correction coefficient and the air-fuel ratio feedback correction coefficient calculated at the third time tn + o + p after the second predetermined time p has elapsed from the second time tn + o. the difference between the 2 compared to the second predetermined value, since the failure of the exhaust secondary air supply device to 如 rather configuration you detected based on their comparison results, easily and accurately a failure of the exhaust secondary air supply device It can be detected well. Further, troublesome work such as learning and confirming the air-fuel ratio sensor output when the exhaust secondary air supply device is normal is not necessary, so that failure detection is not delayed. Further, based on the output of the air-fuel ratio sensor when the exhaust secondary air is supplied, in other words, when the exhaust secondary air is intermittently operated to supply the exhaust secondary air intermittently. Since the failure detection is not performed based on the output, the failure detection is not erroneously affected by the error due to the difference in the load of the internal combustion engine.
[0010]
In the second aspect, wherein the failure detection means, when the first difference that is pre SL calculated does not exceed said first predetermined value, together with the exhaust secondary air supply device detects a failure, When the calculated first difference is greater than or equal to the first predetermined value, and the calculated second difference does not exceed the second predetermined value, the exhaust secondary air supply device has failed. Configured to detect .
[0011]
When the first differential issued calculated does not exceed a first predetermined value, the exhaust secondary air supply device detects a failure, one first difference calculated is not less than the first predetermined value, When the calculated second difference does not exceed the second predetermined value, the exhaust secondary air supply device is configured to detect a failure . Therefore, the first predetermined time is appropriately set, for example, as described subsequently. By setting the time such that the change in the operating state such as the load of the internal combustion engine due to the operation of the secondary air supply device ends, a failure of the exhaust secondary air supply device can be detected more easily and accurately.
[0012]
According to a third aspect of the present invention, the first predetermined time is set based on a time at which a change in the operating state of the internal combustion engine due to the operation of the exhaust secondary air supply device ends.
[0013]
Since the first predetermined time is set based on the time when the change in the operating state of the internal combustion engine due to the operation of the exhaust secondary air supply device ends, the air-fuel ratio sensor behaves unexpectedly according to the change. Also when shown, such an influence can be avoided and a failure of the exhaust secondary air supply device can be detected with higher accuracy.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a failure detection device for an exhaust secondary air supply device according to one embodiment of the present invention will be described with reference to the accompanying drawings.
[0015]
FIG. 1 is a schematic diagram showing the overall configuration of a failure detection device for an exhaust secondary air supply device according to the embodiment.
[0016]
In the figure, reference numeral 10 denotes a multi-cylinder internal combustion engine (hereinafter referred to as “engine”). The engine 10 is composed of a 4-cycle V-type 6-cylinder DOHC engine. The right bank 10R includes three cylinders (cylinders) # 1, # 2, and # 3, and the left bank 10L includes # 4 and # 4. Three cylinders 5 and # 6 are provided.
[0017]
In the engine 10, the air drawn from the air cleaner 14 flows through the intake pipe 16, reaches the intake port of each cylinder 12 through an intake manifold (not shown) while the flow rate is adjusted by the throttle valve 20, and is arranged there. Gasoline fuel is injected from an injector (not shown). Thus, the generated air-fuel mixture enters a cylinder combustion chamber (not shown) when an intake valve (not shown) is opened, and is ignited and burned by a spark plug (not shown).
[0018]
Exhaust gas (exhaust gas) generated by combustion flows through the exhaust manifold 22 provided for each of the left and right banks 10R and 10L when an exhaust valve (not shown) is opened, and merges at the gathering portion. After the harmful components are removed by the flow and the catalytic device (three-way type) 26, they are discharged outside the engine.
[0019]
An exhaust secondary air supply device 30 is provided in an exhaust system including the exhaust manifold 22 and the exhaust pipe 24. The exhaust secondary air supply device 30 mainly includes an air supply pipe (delivery pipe) 32 connected to an upstream position of the catalyst device 26 in the exhaust system of the engine 10 and an air pump 34.
[0020]
The intake pipe 16 is branched upstream of the throttle valve 20, and the other end of the branch pipe 16 a is connected to the intake side of the air pump 34. The discharge side of the air pump 34 is connected to the air supply pipe 32. The air supply pipe 32 branches via a cut-off valve 36 and is connected to the exhaust manifolds 22 of the left and right banks 10R and 10L, respectively. The air supply pipe disposed in the exhaust manifold 22 on the right bank 10R side is 32R, and the air supply pipe on the left bank 10L side is 32L. The air supply pipes 32R and 32L are configured to supply the same amount of air.
[0021]
FIG. 2 shows the configuration of the air supply pipe 32 and the like in detail. As shown in the drawing, a flange 32b is formed in the vicinity of the opening 32a at the tip of the air supply pipe 32, and the opening 32a is formed in the exhaust manifold 22. The air supply pipe 32 is connected to the exhaust manifold 22 by being bolted to the exhaust manifold 22 with a flange 32b while being matched with a hole (shown by a broken line in FIG. 1) 22a.
[0022]
An electric motor 40 is connected to the air pump 34, and is driven by its rotation to suck air sucked from the air cleaner 14 and pump it to the air supply pipe 32. The cut-off valve 36 includes a negative pressure diaphragm (not shown), and when negative pressure is introduced through a negative pressure introduction mechanism (not shown), the cut-off valve 36 is opened to supply the pumped air introduced from the suction port 36a to the exhaust manifold 22. To do.
[0023]
In FIG. 1, a crank angle sensor 42 is arranged near a rotation shaft (not shown) such as a crank shaft of the engine 10 to output a cylinder discrimination signal, and a TDC signal is output at or near the TDC position of each cylinder. In addition, a crank angle signal obtained by subdividing it is output.
[0024]
Further, an absolute pressure sensor 44 is provided downstream of the position of the throttle valve 20 in the intake pipe 16 to output a signal corresponding to the intake pipe absolute pressure (engine load) PBA, and to the cooling water passage (see FIG. (Not shown) is provided with a water temperature sensor 46 and outputs a signal corresponding to the engine cooling water temperature TW.
[0025]
Further, in the exhaust system, a first air-fuel ratio sensor 50 is disposed upstream of the catalyst device 26, and a second air-fuel ratio sensor 52 is disposed downstream thereof. A signal corresponding to the oxygen concentration is output (hereinafter, the sensors arranged in the right bank 10R are 50R and 52R, and those arranged in the left bank 10L are 50L and 52L). The first and second air-fuel ratio sensors 50 and 52 are both O2 sensors, and output signals that repeat inversion in the rich direction and the lean direction around the theoretical air-fuel ratio equivalent value. Hereinafter, the first air-fuel ratio sensor 50 is referred to as “PO2 sensor”, and the second air-fuel ratio sensor 52 is referred to as “SO2 sensor”.
[0026]
The output of the sensor group described above is sent to the ECU 54. The ECU 54 is composed of a microcomputer, counts the crank angle signal of the input crank angle sensor 42 to detect the engine rotational speed NE, and supplies the fuel to the engine 10 based on the sensor output including the crank angle sensor 42. The injection amount TI is calculated as follows.
[0027]
TI = TIM × KO2 × KTOTAL + TTOTAL
In the above, TIM is a basic value obtained by map search from the engine speed NE and the engine load (intake pipe absolute pressure) PBA. KO2 is an air-fuel ratio feedback correction coefficient determined based on the detected air-fuel ratio obtained from the PO2 sensor output, and is calculated as follows. In the following, n is a discrete sample number, more specifically, a control cycle.
KO2 (n) = KO2 (n-1) -KO2I (when the detected air-fuel ratio is rich)
KO2 (n) = KO2 (n-1) + KO2I (when the detected air-fuel ratio is lean)
That is, KO2 is determined by adding / subtracting I (integral control term) to the deviation from the theoretical air-fuel ratio equivalent value (reversal center value) of the PO2 sensor output. Note that KO2 is calculated for each bank based on the outputs of the PO2 sensors 50R and 50L disposed in the left and right banks 10R and L, respectively. Also, KO2 is learning controlled.
[0028]
KTOTAL is a correction coefficient in another multiplication format, and TTOTAL is a correction coefficient in an addition format. The fuel injection amount TI is indicated as the valve opening time of the injector. Further, the fuel injection amount TI is increased when the engine 10 is started.
[0029]
The ECU 54 determines the ignition timing using the engine speed NE and the like, and after the engine 10 is started, energizes the electric motor 40 for a predetermined time to drive the air pump 34 to drive the exhaust secondary air to the exhaust system. To supply. Thereby, the unburned component of the fuel increased at the time of start-up is burned in the exhaust manifold 22 and the exhaust pipe 24 downstream thereof, and released to the atmosphere while heating the catalyst device 26. Thereby, the activation of the catalyst device 26 is promoted, and the release of unburned components to the atmosphere is reduced. The ECU 54 also detects a failure of the exhaust secondary air supply device 30.
[0030]
Next, the failure detection operation of the exhaust secondary air supply device 30 will be described.
[0031]
FIG. 3 is a flowchart showing the operation.
[0032]
In the following, it is determined in S10 whether or not the monitor area (failure detection area). After the engine 10 is started and the warm-up is completed, it is determined as the monitor region when the engine 10 is in an idle state or other steady operation state.
[0033]
When the result in S10 is negative, the subsequent processing is skipped. When the result is affirmative, the process proceeds to S12, and it is determined whether or not a failure of the exhaust secondary air supply device 30 has been detected. Even when the result in S12 is affirmative, the subsequent processing is skipped. Even when the electric motor 40 is not faulty, the subsequent processing is skipped also when it is determined that the electric current to the electric motor 40 is excessive and overheated.
[0034]
On the other hand, when the result in S12 is negative, the program proceeds to S14, in which the air pump 34 is turned on, that is, the electric motor 40 is energized to drive the air pump 34, and learning of the air-fuel ratio feedback correction coefficient KO2 is prohibited. That is, since the original air-fuel ratio feedback control by the artificial air-fuel ratio operation for failure detection is not affected, the learning is prohibited.
[0035]
Next, the process proceeds to S16, and after a certain time (for example, 1 to 2 seconds) has elapsed, the air-fuel ratio feedback correction coefficient KO2 is calculated for each of the left and right banks from the outputs of the PO2 sensors 50R, L in the left and right banks. The correction coefficient calculated from the PO2 sensor 50R on the right bank side is KO2R1, and that on the left bank side is KO2L1. The time at this time is assumed to be tn.
[0036]
Next, the process proceeds to S18, and at time tn + m after a predetermined time m has elapsed from time tn, the air-fuel ratio feedback correction coefficient KO2 is again calculated for the left and right banks from the outputs of the PO2 sensors 50R, L in the left and right banks. The correction coefficient on the right bank side calculated at this time is KO2R2, and that on the left bank side is KO2L2.
[0037]
Next, the process proceeds to S20, and as shown in the figure, the difference obtained by subtracting the air-fuel ratio feedback correction coefficients KO2R1, KO2L1 at time tn from the air-fuel ratio feedback correction coefficients KO2R2, KO2L2 at time tn + m after a predetermined time m, respectively. It is determined whether or not a predetermined value is exceeded.
[0038]
When the result in S20 is affirmative, the process proceeds to S22, where the air supply pipe 32 is determined to be normal (detected), and negative, more precisely, when either or both of KO2R and L are negative, the process proceeds to S24. It is determined (detected) that the air supply pipe 32R or L on the left and right banks side is malfunctioning.
[0039]
Here, it demonstrates with reference to FIG. 4 and FIG.
[0040]
If the exhaust secondary air supply device 30 is normal and the air pump 34 starts to be driven at time ta in FIG. 4, the same amount of air is supplied to the exhaust manifolds 22 in the left and right banks and flows through the exhaust pipe 24. As a result, the exhaust gas gradually becomes leaner at the positions where the PO2 sensors 50R and 50L are arranged. Accordingly, the value of the air-fuel ratio feedback correction coefficient KO2R, L calculated based on the detected value also gradually changes so as to correct in the rich direction, as shown in the figure, at the time tn immediately after the air pump is driven. The difference between the value and the value at time tn + m expands to a certain value or more as the air amount increases.
[0041]
On the other hand, the same amount of air is supplied to the exhaust manifolds 22 of the left and right banks, such as when a failure such as a crack has occurred in one of the air supply pipes 32R, 32L of the left and right banks, causing a leak. When not done, the amount of air flowing through the exhaust pipe 24 also differs between the left and right banks.
[0042]
For example, as shown in FIG. 5, if the above-described failure occurs on the right bank 10R side, the value of the air-fuel ratio feedback correction coefficient KO2R calculated based on the detected value of the PO2 sensor 50R is also shown in FIG. Thus, the expected change is not shown between time tn and time tn + m.
[0043]
Accordingly, the predetermined value is appropriately set, and the difference between the air-fuel ratio feedback correction coefficient calculated at time tn and the air-fuel ratio feedback correction coefficient calculated at time tn + m after a predetermined time m from time tn is set for the left and right banks. By comparing the two, the exhaust secondary air supply device 30 breaks down, and more precisely, the air supply pipe 32R or 32L on the side where the difference does not exceed a predetermined value causes breakage such as cracks. The flange 32b and the exhaust manifold Therefore, it can be determined that a failure has occurred, such as insufficient sealing of the connection part 22 or insufficient sealing of the connection part of the air pump 34 or the cut-off valve 36 and the air supply pipe 32.
[0044]
Here, the predetermined time is set based on the time when the change in the operating state of the engine 10 due to the operation of the exhaust secondary air supply device 30 ends. That is, since the air pump 34 of the exhaust secondary air supply device 30 is driven by the electric motor 40, when the air pump 34 is driven, the operating state such as the load of the engine 10 fluctuates transiently due to a sudden increase in the electrical load, As a result, the behavior of the air-fuel ratio may be affected. Therefore, the predetermined time is set to a time longer than the time at which the change ends, based on the time at which the change of the driving state ends. Thereby, the failure of the exhaust secondary air supply device 30 can be detected with higher accuracy. The air pump 34 stops after the second calculation is completed.
[0045]
Since the failure detection device according to this embodiment is configured as described above, it is possible to easily and accurately detect a failure such as a failure of the exhaust secondary air supply device 30, more specifically, a failure of the air supply pipe 32. Can do.
[0046]
FIG. 6 is a flowchart showing a failure detection operation of the exhaust secondary air supply device 30 according to the second embodiment of the present invention.
[0047]
In the following, after the same processing as in the first embodiment from S100 to S106, the process proceeds to S108, and again at the time tn + o after a certain time o has elapsed from the time tn, the PO2 sensors 50R, From the output of L, the air-fuel ratio feedback correction coefficient KO2 is calculated for each of the left and right banks. The correction coefficient on the right bank side calculated at this time is KO2R2, and that on the left bank side is KO2L2.
[0048]
Next, the process proceeds to S110, and at time tn + o + p after a certain time p has elapsed from time tn + o, the air-fuel ratio feedback correction coefficient KO2 is again calculated for the left and right banks from the outputs of the PO2 sensors 50R, L in the left and right banks. The correction coefficient on the right bank side calculated at this time is KO2R3, and that on the left bank side is KO2L3. The certain times o and p may be the same length as the predetermined time m described above, or may be shorter than that.
[0049]
Next, the process proceeds to S112, and as shown in the figure, the difference obtained by subtracting the air-fuel ratio feedback correction coefficients KO2R1, KO2L1 at time tn from the air-fuel ratio feedback correction coefficients KO2R2, KO2L2 at time tn + o after a predetermined time o, respectively. It is determined whether or not a predetermined value is exceeded.
[0050]
If the result in S112 is negative, more precisely if either or both of KO2R and L are negative, the process proceeds to S114, where the corresponding air supply pipe 32R or L on the left and right bank sides is determined to be faulty (detected), and in S112 When the result is affirmative, the routine proceeds to S116, where the difference obtained by subtracting the air-fuel ratio feedback correction coefficients KO2R1, KO2L1 at time tn from the air-fuel ratio feedback correction coefficients KO2R3, KO2L3 at time tn + o + p after a predetermined time o + p, respectively. It is determined whether or not the second predetermined value is exceeded.
[0051]
When the result in S116 is affirmative, the process proceeds to S118, where it is determined (detected) that the air supply pipe 32 is normal. When the result is negative, that is, when either or both of KO2R and L are denied, the process proceeds to S114. It is determined (detected) that the bank-side air supply pipe 32R or L is out of order.
[0052]
In the above, the difference between the output at the time tn of the PO2 sensors 50R, L and the output at the time tn + m after a predetermined time is obtained, and the difference is compared with a predetermined value set as appropriate to detect a failure. You may do it .
[0053]
The predetermined value (and the second predetermined value) is set by appropriately selecting a value sufficient for determining a failure from the difference as described above. For example, the PO2 sensor when exhaust secondary air is not supplied The difference between the outputs of 50R and L may be learned, and the set predetermined value may be corrected according to the learning value.
[0054]
Further, the air-fuel ratio feedback correction coefficients KO2R and L for the left and right banks are both set to the time tn and the time tn + m after a predetermined time, but may be different for the left and right banks. That is, the time tn and tn + m may be set for the right bank side, while the time tq may be set for the left bank side and tq + r after the predetermined time r.
[0055]
As described above, this embodiment is the failure detection device for the exhaust secondary air supply device 30 that supplies the exhaust secondary air to the upstream position of the catalyst device 26 disposed in the exhaust system of the internal combustion engine (engine) 10. an air-fuel ratio sensor produces an output corresponding to the oxygen concentration in the exhaust gas flowing through the exhaust system (PO2 sensor 50R, L), wherein when the exhaust secondary air is supplied, the first time based on the output of the air-fuel ratio sensor The air-fuel ratio feedback correction coefficient KO2R, L1 calculated at tn and the air-fuel ratio feedback correction coefficient KO2R, L2 calculated at the second time tn + o after the first predetermined time o has elapsed from the first time tn. First correction coefficient difference calculating means for calculating a first difference, first comparing means for comparing the calculated first difference with a first predetermined value, and an empty calculated at the first time tn Fuel ratio The second difference between the feedback correction coefficient KO2R, L1 and the air-fuel ratio feedback correction coefficient KO2R, L3 calculated at the third time tn + o + p after the second predetermined time p has elapsed from the second time tn + o is calculated. Based on a comparison result output by a second correction coefficient difference calculating means, a second comparing means for comparing the calculated second difference with a second predetermined value, and the first and second comparing means. It was composed as comprising a (S 118 from ECU 54, S10 4) failure detecting means for detecting a failure of the exhaust secondary air supply apparatus Te.
[0056]
More specifically, the failure detection means, when the first difference that is pre SL calculated does not exceed said first predetermined value, together with the exhaust secondary air supply device detects a failure, the calculated When the first difference is not less than the first predetermined value and the calculated second difference does not exceed the second predetermined value, the exhaust secondary air supply device detects a failure ( ECU 54, and S 118) as composed of S 112.
[0057]
Further, the first predetermined time m is set based on the time when the change of the operating state of the internal combustion engine due to the operation of the exhaust secondary air supply device ends.
[0058]
In this embodiment, the air supply pipes 30R, L are arranged for each of the left and right banks 10R, L of the V-type engine, and the PO2 sensors 50R, L are arranged downstream thereof. The present invention is not limited to this, and is equally applicable to other than V-type engines. Further, although the O2 sensor is used as the air-fuel ratio sensor, it is not limited thereto, and a sensor that generates an output proportional to the oxygen concentration may be used.
[0059]
【The invention's effect】
According to the first aspect, a failure of the exhaust secondary air supply device can be detected easily and accurately. Further, troublesome work such as learning and confirming the air-fuel ratio sensor output when the exhaust secondary air supply device is normal is not necessary, so that failure detection is not delayed. Further, based on the output of the air-fuel ratio sensor when the exhaust secondary air is supplied, in other words, when the exhaust secondary air is intermittently operated to supply the exhaust secondary air intermittently. Since the failure detection is not performed based on the output, the failure detection is not erroneously affected by the error due to the difference in the load of the internal combustion engine.
[0060]
In the second aspect, the first predetermined time is appropriately set, for example, to a time at which the change in the operation state such as the load of the internal combustion engine due to the operation of the exhaust secondary air supply device ends as will be described subsequently By doing so, the failure of the exhaust secondary air supply device can be detected more easily and accurately.
[0061]
According to the third aspect of the present invention, the first predetermined time is set based on the time at which the change in the operating state of the internal combustion engine due to the operation of the exhaust secondary air supply device ends, and accordingly, Even when the air-fuel ratio sensor exhibits unexpected behavior, such an influence can be avoided and a failure of the exhaust secondary air supply device can be detected with higher accuracy.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing an overall configuration of a failure detection device for an exhaust secondary air supply device according to an embodiment of the present invention.
2 is an explanatory perspective view showing in detail a part of components of an exhaust secondary air supply device such as an air supply pipe in the device shown in FIG. 1;
FIG. 3 is a flowchart showing the operation of the apparatus shown in FIG. 1;
4 illustrates the operation of the apparatus shown in FIG. 3, and shows the output of the air-fuel ratio sensor (O 2 sensor) when the exhaust secondary air supply apparatus is not broken and the air-fuel ratio feedback correction coefficient calculated based on the output. It is a time chart.
FIG. 5 explains the operation of the apparatus shown in FIG. 3. The output of the air-fuel ratio sensor (O 2 sensor) when a failure occurs in the exhaust secondary air supply apparatus and the air-fuel ratio feedback correction coefficient calculated based on the output. It is a time chart which shows.
FIG. 6 is a flow chart similar to FIG. 3, showing the operation of the failure detection device for the exhaust secondary air supply device according to the second embodiment of the present invention.
[Explanation of symbols]
10 Engine (Internal combustion engine)
22 Exhaust manifold 24 Exhaust pipe 26 Catalytic device 30 Exhaust secondary air supply device 32 Air supply pipe 34 Air pump 50 First air-fuel ratio sensor (PO2 sensor)
54 ECU (Electronic Control Unit)

Claims (3)

In a failure detection device for an exhaust secondary air supply device that supplies exhaust secondary air to an upstream position of a catalyst device disposed in an exhaust system of an internal combustion engine, an output corresponding to the oxygen concentration in the exhaust flowing through the exhaust system is generated. When the air-fuel ratio sensor and the exhaust secondary air are supplied, an air-fuel ratio feedback correction coefficient calculated at a first time tn based on the output of the air-fuel ratio sensor and a first predetermined value from the first time tn. First correction coefficient difference calculating means for calculating a first difference from an air-fuel ratio feedback correction coefficient calculated at a second time tn + o after the time o has elapsed, and calculating the calculated first difference to a first First comparison means for comparing with a predetermined value, an air-fuel ratio feedback correction coefficient calculated at the first time tn, and a third time tn + o + p after a second predetermined time p has elapsed from the second time tn + o Calculated Second correction coefficient difference calculating means for calculating a second difference with the air-fuel ratio feedback correction coefficient, second comparing means for comparing the calculated second difference with a second predetermined value, and the second 1. A failure detection device for an exhaust secondary air supply device, comprising failure detection means for detecting a failure of the exhaust secondary air supply device based on a comparison result output by a first comparison device. Said failure detecting means, when the first difference that is pre SL calculated does not exceed said first predetermined value, together with the exhaust secondary air supply device detects a failure, the first difference the calculated is The exhaust secondary air supply device detects a failure when the calculated second difference does not exceed the second predetermined value while being greater than or equal to the first predetermined value. The failure detection device for an exhaust secondary air supply device according to claim 1. 3. The exhaust secondary air according to claim 2, wherein the first predetermined time is set based on a time at which a change in an operating state of the internal combustion engine due to the operation of the exhaust secondary air supply device ends. Failure detection device for the supply device.

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