JP2005009385A - Failure detecting device for exhaust secondary air supply system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a failure detecting device for an exhaust secondary air supply system for simply and precisely detecting a failure of the exhaust secondary air supply system. <P>SOLUTION: In a V-type engine with air supply pipes connected to the respective banks, two air-fuel ratio sensors are provided at their downstream positions for generating outputs corresponding to the concentration of oxygen in exhaust gas. A difference Δmax between maximum values KO2RMAX, KO2LMAX for air-fuel feedback correction, calculated in accordance with the outputs, is calculated (S16, S18) and the calculated difference is compared with a prescribed value (S20). When the calculated difference exceeds the prescribed value, the exhaust secondary air supply system is detected to be in failure (S24). <P>COPYRIGHT: (C)2005,JPO&NCIPI

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 exhaust, secondary exhaust 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. A plurality of air supply pipes connected to the exhaust system of the internal combustion engine for supplying the exhaust secondary air, respectively, and disposed in the exhaust system at positions downstream of the plurality of air supply pipes, respectively. A plurality of air-fuel ratio sensors that produce an output corresponding to the oxygen concentration in the exhaust gas flowing through the exhaust gas, and by comparing values obtained based on the outputs of the plurality of air-fuel ratio sensors, the failure of the exhaust secondary air supply device The apparatus is configured to include failure detection means for detecting.
[0009]
An output according to the oxygen concentration in the exhaust gas that is connected to the exhaust system of the internal combustion engine and is disposed in the exhaust system at a downstream position of a plurality of air supply pipes that supply the exhaust secondary air, respectively, and flows through the exhaust system. And a plurality of air-fuel ratio sensors for generating the exhaust gas, and a failure detection means for detecting a failure of the exhaust secondary air supply device by comparing values obtained based on their outputs. A failure of the air supply device can be detected easily and accurately. In addition, troublesome work such as learning and checking the output of the air-fuel ratio sensor when the exhaust secondary air supply device is normal is unnecessary, and inconveniences such as delay in failure detection due to learning occur. There is nothing. Further, when an air supply pipe is arranged in each engine having an exhaust system for each bank such as a V-type engine, it is not only possible to detect the presence or absence of a failure, but when a failure is detected, which bank It is also possible to detect whether it has occurred in the air supply pipe.
[0010]
3. The correction coefficient difference calculating means for calculating the difference between the air-fuel ratio feedback correction coefficients calculated based on the outputs of the plurality of air-fuel ratio sensors, and the calculation Comparing means for comparing the calculated difference with a predetermined value is provided, and when the calculated difference exceeds the predetermined value, the exhaust secondary air supply device is detected as a failure.
[0011]
A difference between air-fuel ratio feedback correction coefficients calculated based on outputs of a plurality of air-fuel ratio sensors is calculated and compared with a predetermined value. When the calculated difference exceeds a predetermined value, the exhaust secondary air supply device Since it is configured to detect a failure, 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 internal combustion engine is a V-type engine, includes one air pump, the air supply pipe is connected to the air pump, and branches from the middle to each of the V-type engines. It was configured to be connected to the bank.
[0013]
Thereby, in a V-type engine in which an air supply pipe is connected to each bank, a failure of the exhaust secondary air supply device can be detected easily and accurately.
[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, in S16, the air-fuel ratio feedback correction coefficient KO2 is calculated from the outputs of the PO2 sensors 50R, L in the left and right banks, respectively. The correction coefficient calculated from the PO2 sensor 50R on the right bank side is KO2R, and the correction coefficient on the left bank side is KO2L. Then, the maximum values KO2RMAX and KO2LMAX are obtained.
[0036]
Next, in S18, KO2LMAX is subtracted from the obtained maximum value KO2RMAX, and the difference Δmax is obtained as an absolute value.
[0037]
Next, the process proceeds to S20, where the difference Δmax obtained as an absolute value is compared with a predetermined value, and it is determined whether or not the difference Δmax exceeds the predetermined value. If the result is negative, the process proceeds to S22, where the air supply pipe 32 is determined to be normal ( When the determination is affirmative, the process proceeds to S24, where it is determined (detected) that the air supply pipe 32 is out of order.
[0038]
4 and FIG. 5, if the exhaust secondary air supply device 30 is normal, and the air pump 34 starts to be driven at the time ta in FIG. 22 is supplied with the same amount of air and flows through the exhaust pipe 24. As a result, the exhaust gas gradually becomes lean at the positions where the PO2 sensors 50R and 50L are arranged. Therefore, the values of the air-fuel ratio feedback correction coefficients KO2R, L calculated based on the detected values also gradually change so as to correct in the rich direction as shown in the figure, but the difference between the maximum values is also zero. It becomes a very small value.
[0039]
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 either of the air supply pipes 32R, L of the left and right banks, causing air leakage. When not done, the amount of air flowing through the exhaust pipe 24 also differs between the left and right banks.
[0040]
For example, as shown in FIG. 5, if the above-described failure occurs in the air supply pipe on the right bank 10R side, the amount of supplied air is insufficient, and thus is calculated based on the detected value of the PO2 sensor 50R. The change in the value of the air-fuel ratio feedback correction coefficient KO2R is smaller than the change in the air-fuel ratio feedback correction coefficient KO2L on the left bank 10L side to which the desired air amount is supplied, and the difference between the two gradually increases. The maximum value KO2LMAX becomes the maximum.
[0041]
Therefore, the exhaust secondary air supply apparatus 30 is broken by comparing the difference between the air-fuel ratio feedback correction coefficients KO2RMAX and KO2LMAX between the right and left banks as appropriate, and more accurately, the maximum value is small. The air supply pipe 32 (the change in the air-fuel ratio feedback correction coefficient is small) is damaged, such as a crack, the seal of the connecting portion between the flange portion 32b and the exhaust manifold 22 is insufficient, or the air pump 34 or cut It can be determined that a failure has occurred, such as insufficient sealing at the connection between the off valve 36 and the air supply pipe 32.
[0042]
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.
[0043]
As described above, the predetermined value is set by appropriately selecting a value sufficient for determining a failure from the difference. For example, the difference between the outputs of the PO2 sensors 50R and 50L when the secondary exhaust air is not supplied. Learning may be performed and a predetermined value set according to the learning value may be corrected.
[0044]
In the above, the maximum value KO2RMAX, KO2LMAX of the air-fuel ratio feedback correction coefficients KO2R, L of the left and right banks is calculated, and the difference Δmax is calculated and compared with a predetermined value. There is no need to find a value. For example, the maximum value may be obtained for only one of the air-fuel ratio feedback correction coefficients KO2R and L, and the other value may be calculated using a value before reaching the maximum value and compared with a predetermined value. Alternatively, for both KO2R and L, the difference between the two may be calculated using the value before reaching the maximum value and compared with a predetermined value.
[0045]
Further, the difference between the outputs (or the maximum values) of the PO2 sensors 50R, 50L may be obtained, and the failure may be detected by comparing the difference with a predetermined value set as appropriate. Also in this case, when the difference exceeds a predetermined value, the value in the rich direction is output, or the air supply pipe 32 on the PO2 sensor 50R or 50L side indicating the inversion of the output can be regarded as a failure.
[0046]
In this embodiment, as described above, the exhaust secondary air supply for supplying the exhaust secondary air to the upstream position of the catalyst device 26 disposed in the exhaust system (exhaust manifold 22, exhaust pipe 24) of the internal combustion engine (engine) 10. In the failure detection device of the device 30, a plurality of air supply pipes 32R, L connected to an exhaust system (exhaust manifold 22) of the internal combustion engine and supplying the exhaust secondary air respectively, and the plurality of air supply pipes A plurality of air-fuel ratio sensors (PO2 sensors 50R, L) that are arranged in the exhaust system (exhaust pipe 24) at downstream positions and generate outputs corresponding to the oxygen concentration in the exhaust flowing through the exhaust system, respectively. A failure detection means (ECU 54, S10 to S24) for detecting a failure of the exhaust secondary air supply device by comparing values obtained based on the output of the air-fuel ratio sensor is provided. It was.
[0047]
More specifically, the failure detection means is configured to detect the difference between the air-fuel ratio feedback correction coefficients KO2R and L calculated based on the outputs of the plurality of air-fuel ratio sensors (more precisely, the maximum values KO2RMAX and KO2LMAX). Correction coefficient difference calculating means (ECU 54, S16, S18) for calculating the difference Δmax), and comparing means (ECU 54, S20) for comparing the calculated difference with a predetermined value, wherein the calculated difference is a predetermined value. Is exceeded, the exhaust secondary air supply device is configured to detect a failure (ECU 54, S24).
[0048]
The internal combustion engine is a V-type engine, and includes one air pump 34. The air supply pipes 32R and L are connected to the air pump, and branch from the middle to branch into each bank 10R of the V-type engine. , L to be connected.
[0049]
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 even if it is not a V-type engine, if the exhaust system is composed of a plurality of systems and each can be provided with an air supply pipe and an air-fuel ratio sensor, it is equally valid. Further, although the O2 sensor is used as the air-fuel ratio sensor, the present invention is not limited to this, and a sensor that generates an output proportional to the oxygen concentration may be used.
[0050]
【The invention's effect】
According to the first aspect, a failure of the exhaust secondary air supply device can be detected easily and accurately. In addition, troublesome work such as learning and checking the output of the air-fuel ratio sensor when the exhaust secondary air supply device is normal is unnecessary, and inconveniences such as delay in failure detection due to learning occur. There is nothing. Further, when an air supply pipe is arranged in each engine having an exhaust system for each bank such as a V-type engine, it is not only possible to detect the presence or absence of a failure, but when a failure is detected, which bank It is also possible to detect whether it has occurred in the air supply pipe.
[0051]
According to the second aspect of the present invention, it is possible to detect a failure of the exhaust secondary air supply device more easily and accurately.
[0052]
According to the third aspect of the present invention, in the V-type engine in which the air supply pipe is connected to each bank, a failure of the exhaust secondary air supply device can be detected easily and accurately.
[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 (O2 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 (O2 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.
[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 of an exhaust secondary air supply device for supplying exhaust secondary air to a position upstream of a catalyst device disposed in an exhaust system of an internal combustion engine, the exhaust secondary air is connected to the exhaust system of the internal combustion engine and is connected to the exhaust secondary air. And a plurality of air-fuel ratios that are arranged in the exhaust system at positions downstream of the plurality of air supply pipes and generate outputs corresponding to the oxygen concentration in the exhaust gas flowing through the exhaust system. An exhaust secondary air supply comprising a sensor and a failure detection means for detecting a failure of the exhaust secondary air supply device by comparing values obtained based on outputs of the plurality of air-fuel ratio sensors Device failure detection device. The failure detection means compares the calculated difference with a predetermined value with correction coefficient difference calculation means for calculating a difference between air-fuel ratio feedback correction coefficients calculated based on outputs of the plurality of air-fuel ratio sensors. The failure detection device for an exhaust secondary air supply device according to claim 1, further comprising a comparison unit, wherein when the calculated difference exceeds a predetermined value, the exhaust secondary air supply device is detected as a failure. . The internal combustion engine is a V-type engine, includes one air pump, the air supply pipe is connected to the air pump, and is branched from the middle to be connected to each bank of the V-type engine. The failure detection device for an exhaust secondary air supply device according to claim 1 or 2.

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