JP2004204715A - Secondary air feeding abnormality detector for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To detect with high accuracy the abnormality of a system including a secondary air feeding mechanism by calculating with high accuracy a secondary air flow rate regardless of a secondary air downstream air-fuel ratio without installing a new sensor. <P>SOLUTION: When a real secondary air flow rate QAIREAL corrected and calculated by subtracting a secondary air flow rate mean value QERRAVE during an air pump stopping time from a secondary air flow rate mean value QAIAVE during an air pump operating time does not exist between an upper limit flow rate KH1 and a lower limit flow rate KL1, the system including the secondary air feeding mechanism is determined as abnormal (step S117 to step S122). Therefore, variation in the secondary air flow rate caused by secular change and a product tolerance can be favorably corrected by the conventional system without installing a new sensor, thereby suppressing an increase in costs. Also, the calculation accuracy of the real secondary air flow rate QAIREAL is improved, thereby improving abnormality determination accuracy of the system including the secondary air feeding mechanism. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a secondary air supply abnormality detection device for an internal combustion engine that detects an abnormality when secondary air is supplied to activate a catalyst in an exhaust passage of the internal combustion engine.
[0002]
[Prior art]
Conventionally, when a secondary air supply abnormality of an internal combustion engine is detected, a method of directly detecting a secondary air flow rate using a pressure sensor or a flow rate sensor has been considered, but an increase in cost for a new sensor or the like is inevitable. .
[0003]
A related prior art document disclosed in Japanese Patent Application Laid-Open No. 6-146867 is known. In this case, the oxygen (O 2) in the exhaust gas is located downstream of the location where the secondary air supply passage is open, that is, downstream of the secondary air to which the secondary air is supplied. _Two An oxygen sensor for detecting the concentration is provided, and when the output of the oxygen sensor is inverted, it can be determined that the air-fuel ratio (A / F) downstream of the secondary air has reached the stoichiometric air-fuel ratio. There has been proposed a method of obtaining a flow rate of secondary air (secondary air supply amount) supplied from a secondary air supply mechanism to an exhaust passage based on an air amount and an engine operation state.
[Patent Document] JP-A-6-146867 (Pages 2 to 3)
[0004]
[Problems to be solved by the invention]
By the way, in the above-described case, the secondary air flow rate is not obtained unless the air-fuel ratio downstream of the secondary air is controlled near the stoichiometric air-fuel ratio and the oxygen sensor output changes suddenly. Therefore, there is a problem that a calculation error is large.
[0005]
Therefore, the present invention has been made to solve such a problem, and a secondary air flow rate can be calculated with high accuracy regardless of the air-fuel ratio downstream of the secondary air without installing new sensors. It is an object of the present invention to provide a secondary air supply abnormality detecting device for an internal combustion engine that can accurately detect a system abnormality including an air supply mechanism.
[0006]
[Means for Solving the Problems]
According to the secondary air supply abnormality detection device for an internal combustion engine of the first aspect, when the air-fuel ratio supplied to the internal combustion engine estimated by the air-fuel ratio estimating means and the secondary air is supplied from the secondary air supply mechanism. The secondary air supply mechanism is provided by the abnormality determination means based on the secondary air flow rate from the secondary air supply mechanism calculated by the secondary air flow rate calculation means based on the air-fuel ratio detected by the air-fuel ratio detection means A system abnormality is determined. As described above, the secondary air flow rate is calculated with high accuracy regardless of the air-fuel ratio downstream of the secondary air, so that a system abnormality including the secondary air supply mechanism is accurately detected.
[0007]
In the secondary air supply abnormality detection device for an internal combustion engine according to the second aspect, the secondary air flow rate used for the abnormality determination is set to an average value or an integrated value for a predetermined period, so that a steep change is smoothed. Since the calculation accuracy of the secondary air flow rate is improved, a system abnormality including the secondary air supply mechanism is detected with high accuracy.
[0008]
In the abnormality determining means in the secondary air supply abnormality detection device for an internal combustion engine according to the third aspect, the calculation error of the air-fuel ratio supplied to the internal combustion engine is calculated based on the air-fuel ratio supplied to the internal combustion engine and the secondary air supply mechanism. The calculation accuracy is calculated based on the air-fuel ratio detected by the air-fuel ratio detecting means when the air is not supplied, and the secondary air flow rate is corrected by the secondary air flow rate calculating means. The accuracy of the determination of the system abnormality including the secondary air supply mechanism is improved.
[0009]
According to the secondary air supply abnormality detection device for an internal combustion engine of the fourth aspect, the air-fuel ratio supplied to the internal combustion engine by the abnormality determination means and the air-fuel ratio detection when the secondary air is supplied from the secondary air supply mechanism. When the deviation amount of the air-fuel ratio from the air-fuel ratio detected by the means is not within a predetermined range, the abnormality determination means determines that the system is abnormal including the secondary air supply mechanism. As described above, the air-fuel ratio deviation amount is calculated with high accuracy irrespective of the air-fuel ratio downstream of the secondary air, so that a system abnormality including the secondary air supply mechanism is accurately detected.
[0010]
In the abnormality determination means in the secondary air supply abnormality detection device for an internal combustion engine according to claim 5, the steep change is smoothed by setting the air-fuel ratio deviation amount used for abnormality determination to be an average value or an integrated value for a predetermined period. Since the calculation accuracy of the air-fuel ratio deviation amount is improved, a system abnormality including the secondary air supply mechanism can be detected with high accuracy.
[0011]
In the abnormality determining means in the secondary air supply abnormality detecting device for an internal combustion engine according to claim 6, the calculation error of the air-fuel ratio deviation amount is determined by the air-fuel ratio supplied to the internal combustion engine and the secondary air supplied from the secondary air supply mechanism. Correction is performed based on the air-fuel ratio deviation from the air-fuel ratio detected by the air-fuel ratio detection means when the air-fuel ratio is not detected, so that the calculation accuracy of the air-fuel ratio deviation is improved, and the system abnormality including the secondary air supply mechanism is determined. Accuracy is improved.
[0012]
According to the secondary air supply abnormality detecting device for an internal combustion engine according to the seventh aspect, the amount of intake air supplied into the intake passage of the internal combustion engine is further detected by the intake air amount detecting means, and various amounts of fuel are injected by the fuel injection amount calculating means. By calculating the fuel injection amount to be supplied to the internal combustion engine based on the operating parameters, it is possible to construct the system using an existing system without installing new sensors, thereby suppressing an increase in cost.
[0013]
In the abnormality determination means in the secondary air supply abnormality detection device for an internal combustion engine according to claim 8, when it is determined that the system including the secondary air supply mechanism is abnormal, the secondary air supply and the air-fuel ratio feedback control are stopped. In addition, the air-fuel ratio overcorrection due to the air-fuel ratio deviation is prevented beforehand.
[0014]
In the secondary air supply abnormality detection device for an internal combustion engine according to the ninth aspect, the condition that the calculation error of the air-fuel ratio supplied to the internal combustion engine is large, the condition that the secondary air flow rate is not stable, or the secondary air flow amount is large Under the condition where the ratio of the air flow rate becomes small, the diagnosis is prohibited, so that the air-fuel ratio overcorrection due to the air-fuel ratio deviation is prevented beforehand.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described based on examples.
[0016]
<Example 1>
FIG. 1 is a schematic configuration diagram showing an internal combustion engine to which a secondary air supply abnormality detection device for an internal combustion engine according to a first embodiment of the present invention is applied, and peripheral devices thereof.
[0017]
In FIG. 1, reference numeral 10 denotes an internal combustion engine, and an air flow meter 12 that detects an amount of intake air supplied through an air cleaner (not shown) is provided upstream of an intake passage 11 of the internal combustion engine 10. Downstream of the air flow meter 12, a throttle valve 13 for adjusting the amount of intake air to the internal combustion engine 10 is provided. The throttle valve 13 is provided with a throttle opening sensor 14 for detecting its opening. An injector (fuel injection valve) 16 that injects and supplies fuel is disposed near the intake port 15 of each cylinder of the internal combustion engine 10 from the intake passage 11.
[0018]
Then, a mixture of the amount of intake air set by the throttle valve 13 and the fuel injected and supplied by the injector 16 is introduced into the combustion chamber 18 of the internal combustion engine 10 by opening the intake valve 17. An ignition plug 19 is provided for each cylinder on the cylinder head side of the internal combustion engine 10. The mixture in the combustion chamber 18 is ignited by the spark discharge of the ignition plug 19. After the air-fuel mixture is burned in the combustion chamber 18, the exhaust gas is opened from the combustion chamber 18 to the exhaust passage 22 by opening the exhaust valve 21 as exhaust gas.
[0019]
A well-known three-way catalyst 23 is disposed in the middle of the exhaust passage 22, and an A / F sensor 24 that outputs a linear signal according to an A / F (air-fuel ratio) of exhaust gas is provided upstream of the three-way catalyst 23. Is provided with an oxygen sensor 25 whose output voltage is inverted depending on whether the A / F of the exhaust gas is rich or lean with respect to the stoichiometric air-fuel ratio. The crankshaft 26 of the internal combustion engine 10 is provided with a crank angle sensor 27 that detects a crank angle [° CA (Crank Angle)] that is a rotation angle of the crankshaft 26. The engine rotation speed NE is calculated based on the angle of rotation of the crankshaft 26 per predetermined time. Further, the internal combustion engine 10 is provided with a water temperature sensor 28 for detecting the temperature of the cooling water.
[0020]
Next, the configuration of the secondary air supply mechanism 30 that supplies outside air into the exhaust passage 22 will be described. A secondary air supply passage 31 for supplying secondary air is connected to the exhaust passage 22 on the upstream side of the A / F sensor 24. An air filter 32 is provided on the atmosphere side of the secondary air supply passage 31, and an air pump 33 for feeding secondary air under pressure is provided downstream of the air filter 32.
[0021]
On the exhaust passage 22 side of the air pump 33, a combination valve 34 is provided. The combination valve 34 is configured by integrating a pressure-driven open / close valve 35 for opening and closing the secondary air supply passage 31 and a check valve 36 on the downstream side thereof. The open / close valve 35 of the combination valve 34 is switched between open and closed by the back pressure guided by the intake pressure introduction passage 37. The intake pressure introduction passage 37 is connected to the intake passage 11, and the back pressure of the on-off valve 35 is set between the atmospheric pressure and the intake pressure by an electromagnetically driven switching valve 38 provided in the middle of the intake pressure introduction passage 37. Is switched by.
[0022]
That is, when supplying the secondary air, the switching valve 38 is opened to introduce the intake pressure of the intake passage 11. Then, by introducing the intake pressure to the on-off valve 35, the on-off valve 35 is opened. As a result, the secondary air discharged from the air pump 33 passes through the on-off valve 35 and flows to the check valve 36 side. The check valve 36 regulates the flow of the exhaust gas from the exhaust passage 22. When the secondary air pressure of the air pump 33 becomes higher than the exhaust gas pressure, the check valve 36 is controlled by the pressure. Is opened, and the secondary air is supplied into the exhaust passage 22.
[0023]
On the other hand, when stopping the secondary air, the air pump 33 is stopped, and the switching valve 38 is switched to the position for introducing the atmospheric pressure to introduce the atmospheric pressure to the on-off valve 35. Thereby, the on-off valve 35 is closed. Then, the secondary air to the exhaust passage 22 is stopped, and the pressure of the secondary air does not act on the check valve 36, so that the pressure on the exhaust passage 22 side increases. For this reason, the check valve 36 is automatically closed, and the exhaust gas in the exhaust passage 22 is prevented from flowing back to the air pump 33 side.
[0024]
Numeral 40 denotes an ECU (Electronic Control Unit). The ECU 40 stores a CPU 41 as a central processing unit for executing various known arithmetic processing, a ROM 42 storing a control program and a control map, and various data. It is configured as a logical operation circuit including a RAM 43, a B / U (backup) RAM 44, an input / output circuit 45, and a bus line 46 connecting them. The above-mentioned various sensor signals are input to the ECU 40, and control signals are output from the ECU 40 to the injector 16, the ignition plug 19, the air pump 33 of the secondary air supply mechanism 30, the switching valve 38, and the like based on the input signals. .
[0025]
Next, a processing procedure for detecting a secondary air supply abnormality in the CPU 41 in the ECU 40 used in the secondary air supply abnormality detection apparatus for an internal combustion engine according to the first embodiment of the present invention will be described with reference to a flowchart of FIG. This will be described with reference to FIG. The operation will be described with reference to FIG. Specifically, FIG. 3 shows the operation of the parameters calculated in FIG. This parameter is an engine supply air-fuel ratio λENG supplied to the internal combustion engine 10, a secondary air downstream air-fuel ratio λAFS detected downstream of the secondary air supply passage 31, and a secondary air calculated based on these two parameters. Flow rate QAI [g / sec: gram per second]. Note that this secondary air supply abnormality detection routine is repeatedly executed by the CPU 41 at predetermined time intervals.
[0026]
In FIG. 2, first, in step S101, it is determined whether a diagnosis (hereinafter simply referred to as “diag”) condition is satisfied. As the diagnostic conditions, the A / F sensor 24 is activated, the operating condition is steady (no sudden change), the air pump 33 is changed to "ON" or "OFF" and continues for a predetermined time (time t0 to time t1 shown in FIG. 3). ), And the intake air amount QAFM is less than a predetermined amount α. Here, the activity of the A / F sensor 24 can be determined, for example, based on whether the element impedance has become less than a predetermined value [kΩ: kilo ohm].
[0027]
When the determination condition of step S101 is satisfied, that is, when all the diagnostic conditions are satisfied (after time t1 shown in FIG. 3), the process proceeds to step S102, and it is determined whether the air pump 33 is operating. When the determination condition of step S102 is satisfied, that is, when the air pump 33 is operating and the secondary air is being supplied, the process proceeds to step S103, and the continuation counter CON indicating the secondary air “ON (supply)” is incremented by “+1”. Is done. Next, the process proceeds to step S104, where the engine that is supplied to the internal combustion engine 10 by the following equation (1) based on the intake air amount QAFM detected by the air flow meter 12 and the fuel injection amount F supplied from the injector 16: The supply air-fuel ratio λENG is calculated (see FIG. 3). Note that 14.5 is a value near the stoichiometric air-fuel ratio.
[0028]
(Equation 1)
λENG ← QAFM / F / 14.5 (1)
[0029]
Next, in step S105, the secondary air downstream air-fuel ratio λAFS downstream of the secondary air supply passage 31 is read based on the A / F sensor 24 signal. Next, the process proceeds to step S106, where the secondary air flow rate QAI when the air pump 33 is operating is calculated by the following equation (2) (see FIG. 3).
[0030]
(Equation 2)
QAI ← λAFS / λENG * QAFM-QAFM (2)
[0031]
Next, the process proceeds to step S107, in which the secondary air flow rate QAI when the air pump 33 calculated in step S106 is operating is integrated to calculate a secondary air flow integrated value QAISUM. Next, the process proceeds to step S108, and it is determined whether or not the continuation counter CON incremented in step S103 exceeds a predetermined value K1. When the determination condition of step S108 is satisfied, that is, when the continuation counter CON is larger than the predetermined value K1, the process proceeds to step S109, and the secondary air flow average value QAIAVE with respect to the secondary air flow QAI when the air pump 33 is operating is calculated by the following equation ( It is calculated in 3).
[0032]
[Equation 3]
QAIAVE ← QAISUM / CON (3)
[0033]
On the other hand, when the determination condition of step S102 is not satisfied, that is, when the secondary air is not supplied while the air pump 33 is stopped, the process proceeds to step S110, and the continuation counter COFF indicating the secondary air “OFF (stop)” is set. "+1" is incremented. Next, the routine proceeds to step S111, where the intake air amount QAFM detected by the air flow meter 12 and the fuel injection amount F supplied from the injector 16 are supplied to the internal combustion engine 10 by the above equation (1). The supply air-fuel ratio λENG is calculated (see FIG. 3). Next, in step S112, the secondary air downstream air-fuel ratio λAFS downstream of the secondary air supply hole 31a of the secondary air supply passage 31 connected to the exhaust passage 22 is read based on the A / F sensor 24 signal. I will. Next, the process proceeds to step S113, where the secondary air flow rate QERR when the air pump 33 is stopped is calculated by the following equation (4).
[0034]
(Equation 4)
QERR ← λAFS / λENG * QAFM-QAFM (4)
[0035]
Next, the process proceeds to step S114, in which the secondary air flow rate QERR at the time when the air pump 33 is stopped calculated in step S113 is integrated to calculate a secondary air flow integrated value QERRSUM. Next, the process proceeds to step S115, where it is determined whether the continuation counter COFF incremented in step S110 exceeds a predetermined value K2. If the determination condition of step S115 is satisfied, that is, if the continuation counter COFF is larger than the predetermined value K2, the process proceeds to step S116, and the next air flow average value QERRAVE in the secondary air flow QERR when the air pump 33 is stopped is calculated by the following equation (5). ).
[0036]
(Equation 5)
QERRAVE ← QERRSUM / COFF (5)
[0037]
After the processing in step S109 or step S116, the process proceeds to step S117, in which the secondary air flow when the air pump 33 calculated in step S116 is stopped is calculated from the average secondary air flow rate QAIAVE when the air pump 33 calculated in step S109 is activated. The flow average value QERRAVE is subtracted, and the true secondary air flow QAIREAL is calculated. Next, the process proceeds to step S118, and it is determined whether the true secondary air flow rate QAIREAL calculated in step S117 exceeds a preset upper limit flow rate KH1. If the determination condition in step S118 is not satisfied, that is, if the true secondary air flow rate QAIREAL is less than or equal to the upper limit flow rate KH1, the process proceeds to step S119, and if the true secondary air flow rate QAIREAL is less than the preset lower limit flow rate KL1. It is determined whether there is. If the determination condition of step S119 is not satisfied, that is, if the true secondary air flow rate QAIREAL is within the range between the upper limit flow rate KH1 and the lower limit flow rate KL1, the process proceeds to step S120, and it is determined that the secondary air supply system is normal. (See FIG. 3), this routine ends.
[0038]
On the other hand, when the determination condition in step S118 is satisfied, that is, when the true secondary air flow rate QAIREAL exceeds the upper limit flow rate KH1, the process proceeds to step S121, and it is determined that the flow rate is excessive in the secondary air supply system (see FIG. 3). Then, this routine ends. On the other hand, when the determination condition of step S119 is satisfied, that is, when the true secondary air flow rate QAIREAL is less than the lower limit flow rate KL1, the process proceeds to step S122, and it is determined that the flow rate is insufficient in the secondary air supply system (see FIG. 3). Then, this routine ends.
[0039]
When the determination condition of step S101 is not satisfied, that is, when at least one diagnosis condition is not satisfied (before time t1 shown in FIG. 3), or the determination condition of step S108 is not satisfied, that is, the continuation counter CON Is smaller than the predetermined value K1 or when the determination condition of step S115 is not satisfied, that is, when the continuation counter COFF is smaller than the predetermined value K2, the routine is terminated without any operation.
[0040]
As described above, the secondary air supply abnormality detection device for the internal combustion engine according to the present embodiment is installed in the exhaust passage 22 of the internal combustion engine 10 and purifies exhaust gas, and the upstream side of the three-way catalyst 23. A secondary air supply mechanism 30 for supplying secondary air into the exhaust passage 22 of the first and second exhaust passages 22 and a downstream side of the secondary air supply passage 31 a of the secondary air supply passage 31 in the exhaust passage 22 on the upstream side of the three-way catalyst 23. An A / F sensor 24 is provided as an air-fuel ratio detecting means for detecting an A / F (air-fuel ratio) in the exhaust gas, and a CPU 41 in the ECU 40 for estimating an engine supply air-fuel ratio λENG supplied to the internal combustion engine 10. And the engine supply air-fuel ratio λENG supplied to the internal combustion engine 10 estimated by the air-fuel ratio estimation means and the secondary air supply mechanism 30 is supplying secondary air. Detected by A / F sensor 24 A secondary air flow rate calculating means, which is achieved by a CPU 41 in the ECU 40 for calculating a secondary air flow rate QAI from the secondary air supply mechanism 30 based on the secondary air downstream air-fuel ratio λAFS, and the secondary air flow rate calculation Abnormality determination means achieved by the CPU 41 in the ECU 40 for determining a system abnormality including the secondary air supply mechanism 30 based on the secondary air flow rate QAI calculated by the means.
[0041]
The abnormality determination means achieved by the CPU 41 in the ECU 40 of the secondary air supply abnormality detection device for the internal combustion engine of the present embodiment is a secondary air flow rate QAI used for abnormality determination integrated for a predetermined period and averaged. The air flow average value QAIAVE is used. The abnormality determination means achieved by the CPU 41 in the ECU 40 of the secondary air supply abnormality detection device for the internal combustion engine according to the present embodiment calculates the engine supply air-fuel ratio λENG supplied to the internal combustion engine 10 from the calculation error. 10 based on the engine supply air-fuel ratio λENG supplied to the engine 10 and the secondary air downstream air-fuel ratio λAFS detected by the A / F sensor 24 when the secondary air is not supplied from the secondary air supply mechanism 30. The flow rate QERR is calculated, and the secondary air flow rate QAI calculated by the secondary air flow rate calculation means achieved by the CPU 41 in the ECU 40 is corrected.
[0042]
In addition, the secondary air supply abnormality detection device for an internal combustion engine according to the present embodiment includes an air flow meter 12 as intake air amount detection means for detecting an intake air amount QAFM supplied into an intake passage 11 of the internal combustion engine 10; A fuel injection amount calculating means which is achieved by the CPU 41 in the ECU 40 and calculates a fuel injection amount F to be supplied to the engine 10 on the basis of an intake air amount QAFM as various operating parameters and an engine rotation speed NE by the crank angle sensor 27. The engine supply air-fuel ratio λENG supplied to the internal combustion engine 10 is calculated based on the intake air amount QAFM and the fuel injection amount F.
[0043]
That is, the true secondary air flow rate QAIREAL is calculated by subtracting and correcting the secondary air flow average value QERRAVE when the air pump 33 is stopped from the secondary air flow average value QAIAVE when the air pump 33 is operating, and calculating the true secondary air flow rate QAIREAL. When the secondary air flow rate QAIREAL is not between the upper limit flow rate KH1 and the lower limit flow rate KL1 within a predetermined range, it is determined that the system including the secondary air supply mechanism 30 is abnormal. For this reason, the cost increase can be suppressed by appropriately correcting the secondary air flow rate variation due to aging or product tolerance by the existing system without installing new sensors. In addition, the accuracy of the determination of the system abnormality including the secondary air supply mechanism 30 is improved by appropriately correcting the fuel injection amount variation from the injector 16 and the like, and improving the calculation accuracy of the true secondary air flow rate QAIREAL. Can be.
[0044]
Further, the abnormality determining means achieved by the CPU 41 in the ECU 40 of the secondary air supply abnormality detecting device for the internal combustion engine of the present embodiment is configured to perform the secondary air supply when the system including the secondary air supply mechanism 30 is determined to be abnormal. This is to stop the supply and the air-fuel ratio feedback control. In addition, the secondary air supply abnormality detection device for an internal combustion engine according to the present embodiment has a condition that a calculation error of the air-fuel ratio supplied to the internal combustion engine 10 becomes large, a condition that the secondary air flow rate is not stable, or a condition that the intake air amount is Under the condition that the ratio of the secondary air flow rate becomes small, the diagnosis is prohibited. Thus, it is possible to prevent the air-fuel ratio overcorrection due to the A / F deviation.
[0045]
By the way, in the above-described embodiment, the system abnormality determination including the secondary air supply mechanism 30 when the secondary air flow rate calculated when the air pump 33 is operated is not within the predetermined range has been described. However, the present invention is not limited to this. For example, even though the air pump 33 is in a stop condition, the air pump 33 is in an operating state and the secondary air supply mechanism 30 or the like has some abnormality. It is also possible to cope with a system abnormality in which the secondary air is supplied into the exhaust passage 22 from the secondary air supply hole 31a of the secondary air supply passage 31.
[0046]
<Example 2>
FIG. 4 is a flowchart showing a processing procedure for detecting a secondary air supply abnormality in the CPU 41 in the ECU 40 used in the secondary air supply abnormality detection apparatus for an internal combustion engine according to the second example of the embodiment of the present invention. This will be described with reference to the time chart of FIG. Note that this secondary air supply abnormality detection routine is repeatedly executed by the CPU 41 at predetermined time intervals. Further, the configuration of the secondary air supply abnormality detection device for an internal combustion engine according to the present embodiment is the same as the schematic diagram of FIG. 1 in the above-described first embodiment, and a detailed description thereof will be omitted.
[0047]
4, first, in step S201, as in the above-described embodiment, the A / F sensor 24 is activated, the operating condition is steady (no sudden change), and the air pump 33 changes to “ON” or “OFF” for a predetermined time. Continuation (time t0 to time t1 shown in FIG. 3), it is determined whether a diag condition such as the intake air amount QAFM is less than the predetermined amount α is satisfied. When the determination condition of step S201 is satisfied, that is, when all the diagnostic conditions are satisfied (after time t1 shown in FIG. 3), the process proceeds to step S202, and it is determined whether the air pump 33 is operating. When the determination condition of step S202 is satisfied, that is, when the air pump 33 is operating and the secondary air is being supplied, the process proceeds to step S203, and the intake air amount QAFM detected by the air flow meter 12 and the supply from the injector 16 are provided. From the fuel injection amount F, the engine supply air-fuel ratio λENG supplied to the internal combustion engine 10 is calculated by the above equation (1) (see FIG. 3).
[0048]
Next, in step S204, the secondary air downstream air-fuel ratio λAFS downstream of the secondary air supply hole 31a of the secondary air supply passage 31 connected to the exhaust passage 22 is read based on the A / F sensor 24 signal. I will. Next, proceeding to step S205, the engine supply air-fuel ratio λENG calculated in step S203 is subtracted from the secondary air downstream air-fuel ratio λAFS read in step S204, and the air-fuel ratio deviation amount ΔλON when the air pump 33 operates is reduced. It is calculated (the air-fuel ratio deviation amount between the secondary air downstream air-fuel ratio λAFS and the engine supply air-fuel ratio λENG shown in FIG. 3). Next, the process proceeds to step S206, where the air-fuel ratio deviation amount ΔλON when the air pump 33 calculated in step S205 is operating is integrated, and the air-fuel ratio deviation amount integrated value ΔλONSUM is calculated.
[0049]
On the other hand, when the determination condition of step S202 is not satisfied, that is, when the secondary air is not supplied when the air pump 33 is stopped, the process proceeds to step S207, and the intake air amount QAFM detected by the air flow meter 12 and the injector 16 From the supplied fuel injection amount F, the engine supply air-fuel ratio λENG supplied to the internal combustion engine 10 is calculated by the above equation (1) (see FIG. 3). Next, in step S208, the secondary air downstream air-fuel ratio λAFS downstream of the secondary air supply hole 31a of the secondary air supply passage 31 connected to the exhaust passage 22 is read based on the A / F sensor 24 signal. I will. Next, the process proceeds to step S209, in which the engine supply air-fuel ratio λENG calculated in step S207 is subtracted from the secondary air downstream air-fuel ratio λAFS read in step S208, and the air-fuel ratio deviation amount ΔλOFF when the air pump 33 is stopped is calculated. Is done.
[0050]
Next, the process proceeds to step S210, where the air-fuel ratio deviation amount ΔλOFF when the air pump 33 is stopped calculated in step S209 is integrated, and the air-fuel ratio deviation amount integrated value ΔλOFFSUM is calculated. After the processing of step S206 or step S210, the process shifts to step S211 to determine whether or not a predetermined time has been integrated. When the determination condition of step S211 is satisfied, that is, when the integration is performed for a predetermined time, the process proceeds to step S212, and the air-fuel ratio deviation integrated value ΔOFFSUM calculated in step S210 is calculated from the air-fuel ratio deviation integrated value ΔONSUM calculated in step S206. The air-fuel ratio deviation integrated value ΔλREALSUM for abnormality determination is calculated.
[0051]
Next, the process proceeds to step S213, and it is determined whether or not the abnormality determination air-fuel ratio deviation amount integrated value ΔλREALSUM calculated in step S212 exceeds the preset upper limit value KH2. If the determination condition in step S213 is not satisfied, that is, if the air-fuel ratio deviation integrated value ΔλREALSUM for abnormality determination is smaller than the upper limit KH2, the process proceeds to step S214, and the air-fuel ratio deviation integrated value ΔλREALSUM for abnormality determination is set in advance. It is determined whether it is less than the lower limit value KL2. When the determination condition in step S214 is not satisfied, that is, when the air-fuel ratio deviation integrated value ΔλREALSUM for abnormality determination is within the range between the upper limit value KH2 and the lower limit value KL2, the process proceeds to step S215, and the secondary air supply system operates normally. Is determined, and this routine ends.
[0052]
On the other hand, when the determination condition of step S213 is satisfied, that is, when the abnormality determination air-fuel ratio deviation amount integrated value ΔλREALSUM exceeds the upper limit value KH2 and is large, the process proceeds to step S216, where it is determined that the flow rate is excessive in the secondary air supply system. End the routine. On the other hand, when the determination condition of step S214 is satisfied, that is, when the abnormality determination air-fuel ratio deviation integrated value ΔλREALSUM is less than the lower limit value KL2, the process proceeds to step S217, and it is determined that the flow rate is insufficient in the secondary air supply system, and End the routine. When the determination condition of step S201 is not satisfied, that is, when at least one diagnosis condition is not satisfied (prior to time t1 shown in FIG. 3), or the determination condition of step S211 is not satisfied, that is, the predetermined time integration If not, the routine ends without doing anything.
[0053]
As described above, the secondary air supply abnormality detection device for the internal combustion engine according to the present embodiment is installed in the exhaust passage 22 of the internal combustion engine 10 and purifies exhaust gas, and the upstream side of the three-way catalyst 23. A secondary air supply mechanism 30 for supplying secondary air into the exhaust passage 22 of the first and second exhaust passages 22 and a downstream side of the secondary air supply passage 31 a of the secondary air supply passage 31 in the exhaust passage 22 on the upstream side of the three-way catalyst 23. An A / F sensor 24 is provided as an air-fuel ratio detecting means for detecting an A / F (air-fuel ratio) in the exhaust gas, and a CPU 41 in the ECU 40 for estimating an engine supply air-fuel ratio λENG supplied to the internal combustion engine 10. And the engine supply air-fuel ratio λENG supplied to the internal combustion engine 10 estimated by the air-fuel ratio estimation means and the secondary air supply mechanism 30 is supplying secondary air. Detected by A / F sensor 24 Abnormality determination means achieved by the CPU 41 in the ECU 40 that determines a system abnormality including the secondary air supply mechanism 30 based on the air-fuel ratio deviation amount ΔλON from the secondary air downstream air-fuel ratio λAFS. is there.
[0054]
The abnormality determination means achieved by the CPU 41 in the ECU 40 of the secondary air supply abnormality detection device for an internal combustion engine of the present embodiment is an air-fuel ratio deviation amount integration obtained by integrating the air-fuel ratio deviation amount ΔλON used for abnormality determination for a predetermined period. The value is ΔλONSUM. The abnormality determination means achieved by the CPU 41 in the ECU 40 of the secondary air supply abnormality detection device for the internal combustion engine according to the present embodiment uses the calculation error of the air-fuel ratio deviation amount ΔλON to supply the engine supply to the internal combustion engine 10. The correction is performed based on the air-fuel ratio λENG and the air-fuel ratio deviation amount ΔλOFF from the secondary air downstream air-fuel ratio λAFS detected by the A / F sensor 24 when the secondary air is not supplied from the secondary air supply mechanism 30. is there.
[0055]
In addition, the secondary air supply abnormality detection device for an internal combustion engine according to the present embodiment includes an air flow meter 12 as intake air amount detection means for detecting an intake air amount QAFM supplied into an intake passage 11 of the internal combustion engine 10; A fuel injection amount calculating means which is achieved by the CPU 41 in the ECU 40 and calculates a fuel injection amount F to be supplied to the engine 10 on the basis of an intake air amount QAFM as various operating parameters and an engine rotation speed NE by the crank angle sensor 27. The engine supply air-fuel ratio λENG supplied to the internal combustion engine 10 is calculated based on the intake air amount QAFM and the fuel injection amount F.
[0056]
That is, the air-fuel ratio deviation integrated value ΔλOFFSUM when the air pump 33 is stopped is subtracted and corrected from the air-fuel ratio deviation integrated value ΔλONSUM when the air pump 33 is operated, and the abnormality-determined air-fuel ratio deviation integrated value ΔλREALSUM is calculated. When the abnormality determination air-fuel ratio deviation amount integrated value ΔλREALSUM is not between the upper limit KH2 and the lower limit KL2 within a predetermined range, it is determined that the system including the secondary air supply mechanism 30 is abnormal. For this reason, the cost increase can be suppressed by appropriately correcting the secondary air flow rate variation due to aging or product tolerance by the existing system without installing new sensors. Further, the accuracy of the determination of the system abnormality including the secondary air supply mechanism 30 is improved by suitably correcting the fuel injection amount variation by the injector 16 and improving the calculation accuracy of the abnormality determination air-fuel ratio deviation integrated value ΔλREALSUM. can do.
[0057]
Further, the abnormality determining means achieved by the CPU 41 in the ECU 40 of the secondary air supply abnormality detecting device for the internal combustion engine of the present embodiment is configured to perform the secondary air supply when the system including the secondary air supply mechanism 30 is determined to be abnormal. This is to stop the supply and the air-fuel ratio feedback control. In addition, the secondary air supply abnormality detection device for an internal combustion engine according to the present embodiment has a condition that a calculation error of the air-fuel ratio supplied to the internal combustion engine 10 becomes large, a condition that the secondary air flow rate is not stable, or a condition that the intake air amount is Under the condition that the ratio of the secondary air flow rate becomes small, the diagnosis is prohibited. Thus, it is possible to prevent the air-fuel ratio overcorrection due to the A / F deviation.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram showing an internal combustion engine to which a secondary air supply abnormality detection device for an internal combustion engine according to a first embodiment and a second embodiment of the present invention is applied, and peripheral devices thereof; It is.
FIG. 2 shows a processing procedure of secondary air supply abnormality detection by a CPU in an ECU used in a secondary air supply abnormality detection device for an internal combustion engine according to a first embodiment of the present invention. It is a flowchart shown.
FIG. 3 is a time chart showing a transition state of an engine supply air-fuel ratio, a secondary air downstream air-fuel ratio, and a secondary air flow rate corresponding to the processing of FIG. 2;
FIG. 4 is a flowchart showing a processing procedure for detecting a secondary air supply abnormality in a CPU in an ECU used in a secondary air supply abnormality detection apparatus for an internal combustion engine according to a second embodiment of the present invention; It is a flowchart shown.
[Explanation of symbols]
10 Internal combustion engine
11 Intake passage
12 Air flow meter
22 Exhaust passage
23 Three-way catalyst
24 A / F (air-fuel ratio) sensor
27 Crank angle sensor
30 Secondary air supply mechanism
31 Secondary air supply passage
31a Secondary air supply hole
40 ECU (electronic control unit)

Claims (9)

A catalyst installed in the exhaust passage of the internal combustion engine for purifying exhaust gas,
A secondary air supply mechanism for supplying secondary air into the exhaust passage on the upstream side of the catalyst;
Air-fuel ratio detection means disposed in the exhaust passage on the upstream side of the catalyst and downstream of the supply hole for secondary air to detect an air-fuel ratio in exhaust gas;
Air-fuel ratio estimation means for estimating the air-fuel ratio supplied to the internal combustion engine,
Based on the air-fuel ratio supplied to the internal combustion engine estimated by the air-fuel ratio estimating means and the air-fuel ratio detected by the air-fuel ratio detecting means when the secondary air is supplied from the secondary air supply mechanism. Secondary air flow rate calculating means for calculating a secondary air flow rate from the secondary air supply mechanism;
Abnormality determining means for determining a system abnormality including the secondary air supply mechanism based on the secondary air flow rate calculated by the secondary air flow rate calculating means. Supply abnormality detection device. 2. The secondary air supply abnormality detection device for an internal combustion engine according to claim 1, wherein the abnormality determination unit sets the secondary air flow rate used for abnormality determination as an average value or an integrated value for a predetermined period. 3. The abnormality judging means calculates a calculation error of an air-fuel ratio supplied to the internal combustion engine by comparing the air-fuel ratio supplied to the internal combustion engine with the air-fuel ratio when the secondary air is not supplied from the secondary air supply mechanism. 3. The internal combustion engine according to claim 1, wherein the secondary air flow rate is calculated based on the air-fuel ratio detected by the detection means, and the secondary air flow rate calculated by the secondary air flow rate calculation means is corrected. Secondary air supply abnormality detection device. A catalyst installed in the exhaust passage of the internal combustion engine for purifying exhaust gas,
A secondary air supply mechanism for supplying secondary air into the exhaust passage on the upstream side of the catalyst;
Air-fuel ratio detection means disposed in the exhaust passage on the upstream side of the catalyst and downstream of the supply hole for secondary air to detect an air-fuel ratio in exhaust gas;
A predetermined amount of air-fuel ratio deviation between the air-fuel ratio supplied to the internal combustion engine and the air-fuel ratio detected by the air-fuel ratio detection means when the secondary air is supplied from the secondary air supply mechanism. A secondary air supply abnormality detection device for an internal combustion engine, comprising: abnormality determination means for determining a system abnormality including the secondary air supply mechanism when not within the range. 5. The secondary air supply abnormality detection device for an internal combustion engine according to claim 4, wherein the abnormality determination unit sets the air-fuel ratio deviation amount used for abnormality determination as an average value or an integrated value for a predetermined period. The abnormality determination means detects the calculation error of the air-fuel ratio deviation amount by the air-fuel ratio detection means when the air-fuel ratio supplied to the internal combustion engine and the secondary air is not supplied from the secondary air supply mechanism. The secondary air supply abnormality detection device for an internal combustion engine according to claim 4 or 5, wherein the correction is performed based on an air-fuel ratio deviation amount from the air-fuel ratio to be performed. Intake air amount detection means for detecting an intake air amount supplied into an intake passage of the internal combustion engine,
Fuel injection amount calculation means for calculating the fuel injection amount to be supplied to the internal combustion engine based on various operating parameters,
The secondary air supply abnormality detection device for an internal combustion engine according to claim 1 or 4, wherein the air-fuel ratio supplied to the internal combustion engine is calculated based on the intake air amount and the fuel injection amount. 5. The internal combustion engine according to claim 1, wherein the abnormality determination unit stops the secondary air supply and the air-fuel ratio feedback control when determining that the system including the secondary air supply mechanism is abnormal. Secondary air supply abnormality detection device. Under the condition that the calculation error of the air-fuel ratio supplied to the internal combustion engine becomes large, the condition that the secondary air flow rate is not stable, or the condition that the intake air amount is large and the ratio of the secondary air flow rate becomes small, the diagnosis (Diagnosis: The secondary air supply abnormality detecting device for an internal combustion engine according to claim 1 or 4, wherein the diagnosis is prohibited.

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