JP4161708B2 - Secondary air supply abnormality detection device for internal combustion engine - Google Patents

Description

[0001]
BACKGROUND 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 supplying secondary air to activate a catalyst in an exhaust passage of the internal combustion engine.
[0002]
[Prior art]
Conventionally, a method of directly detecting the secondary air flow rate using a pressure sensor or a flow rate sensor when detecting an abnormality in the secondary air supply of the internal combustion engine is conceivable. .
[0003]
As related art documents related to this, those disclosed in Japanese Patent Laid-Open No. 6-146867 are known. In this case, oxygen (O) in the exhaust gas is provided downstream of the location where the secondary air supply passage is open, that is, downstream of the secondary air to which secondary air is supplied.₂ ) When an oxygen sensor for detecting the concentration is provided and the output of the oxygen sensor is reversed, it can be determined that the air-fuel ratio (A / F) downstream of the secondary air is the stoichiometric air-fuel ratio. There has been proposed a method for obtaining a flow rate of secondary air (secondary air supply amount) supplied from the secondary air supply mechanism to the exhaust passage based on the air amount and the engine operating state.
[Patent Literature]
JP-A-6-146867 (pages 2 to 3)
[0004]
[Problems to be solved by the invention]
By the way, in the above, the secondary air flow rate cannot be obtained unless the air-fuel ratio downstream of the secondary air is controlled in the vicinity of the theoretical air-fuel ratio and the oxygen sensor output changes suddenly. Therefore, there was a problem that the calculation error was large.
[0005]
Therefore, the present invention has been made to solve such a problem. The secondary air flow rate is calculated with high accuracy regardless of the air-fuel ratio downstream of the secondary air without installing new sensors. An object of the present invention is to provide a secondary air supply abnormality detection device for an internal combustion engine capable of accurately detecting 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 claim 1, when the secondary air is supplied from the air-fuel ratio supplied to the internal combustion engine estimated by the air-fuel ratio estimation means and the secondary air supply mechanism. The secondary air supply mechanism is included 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 error is determined. In this way, since the secondary air flow rate is calculated with high accuracy regardless of the air-fuel ratio downstream of the secondary air, the system abnormality including the secondary air supply mechanism is detected with high accuracy.
Further, the abnormality determination means is an air-fuel ratio detection means when the calculation error of the air-fuel ratio supplied to the internal combustion engine is that the air-fuel ratio supplied to the internal combustion engine and the secondary air are not supplied from the secondary air supply mechanism. Calculation based on the detected air-fuel ratio and correction of the secondary air flow rate by the secondary air flow rate calculation means improve the calculation accuracy of the secondary air flow rate, and improve the system abnormality including the secondary air supply mechanism. The determination accuracy is improved.
The intake air amount detection means detects the intake air amount supplied into the intake passage of the internal combustion engine, and the fuel injection amount calculation means calculates the fuel injection amount supplied to the internal combustion engine based on various operating parameters. Therefore, since it can be constructed by an existing system without installing new sensors, an increase in cost can be suppressed.
[0007]
In the abnormality determination means in the secondary air supply abnormality detection device for an internal combustion engine according to claim 2, the abrupt change is smoothed by making the secondary air flow rate used for abnormality determination an average value or an integrated value for a predetermined period. Since the calculation accuracy of the secondary air flow rate is improved, the system abnormality including the secondary air supply mechanism is detected with high accuracy.
[0009]
According to the secondary air supply abnormality detection device for an internal combustion engine of claim 3,An air-fuel ratio deviation amount between the air-fuel ratio supplied to the internal combustion engine by the abnormality determination means 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 is preset. When it is not within the predetermined range, it is determined by the abnormality determining means that there is a system abnormality including the secondary air supply mechanism. In this manner, the air-fuel ratio deviation is calculated with high accuracy regardless of the air-fuel ratio downstream of the secondary air, so that the system abnormality including the secondary air supply mechanism is detected with high accuracy.
Further, in this abnormality determination means, the air-fuel ratio deviation amount used for abnormality determination is set to an average value or integrated value for a predetermined period, so that a steep change is smoothed and the calculation accuracy of the air-fuel ratio deviation amount is improved. Therefore, the system abnormality including the secondary air supply mechanism is detected with high accuracy.
The intake air amount detection means detects the intake air amount supplied into the intake passage of the internal combustion engine, and the fuel injection amount calculation means calculates the fuel injection amount supplied to the internal combustion engine based on various operating parameters. Therefore, since it can be constructed by an existing system without installing new sensors, an increase in cost can be suppressed.
[0010]
In the abnormality determination means in the secondary air supply abnormality detection device for an internal combustion engine according to claim 4,Since the air-fuel ratio deviation amount used for abnormality determination is set to an average value or an integrated value for a predetermined period, a steep change is smoothed and the calculation accuracy of the air-fuel ratio deviation amount is improved. Including system abnormalities are detected with high accuracy.
[0013]
Claim5In the abnormality determination means in the secondary air supply abnormality detection apparatus for an internal combustion engine, when the system abnormality including the secondary air supply mechanism is determined, the secondary air supply and the air-fuel ratio feedback control are stopped, so that the air-fuel ratio Air-fuel ratio overcorrection due to deviation is prevented in advance.
[0014]
Claim6In the secondary air supply abnormality detection device for an internal combustion engine of this type, a condition that the calculation error of the air-fuel ratio supplied to the internal combustion engine becomes large, a condition that the secondary air flow rate is unstable, or a large intake air amount and a secondary air flow rate Under the condition that the ratio is small, the diagnosis is prohibited, so that over-correction of the air-fuel ratio due to the air-fuel ratio deviation is prevented in advance.
[0015]
DETAILED DESCRIPTION OF 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 and its peripheral devices to which a secondary air supply abnormality detection device for an internal combustion engine according to a first example of an embodiment of the present invention is applied.
[0017]
In FIG. 1, reference numeral 10 denotes an internal combustion engine, and an air flow meter 12 for detecting an intake air amount supplied via an air cleaner (not shown) is disposed upstream of an intake passage 11 of the internal combustion engine 10. A throttle valve 13 that adjusts the amount of intake air to the internal combustion engine 10 is disposed downstream of the air flow meter 12. The throttle valve 13 is provided with a throttle opening sensor 14 for detecting the opening. An injector (fuel injection valve) 16 for supplying fuel is disposed near the intake port 15 of each cylinder of the internal combustion engine 10 from the intake passage 11.
[0018]
Then, the air-fuel mixture of the intake air amount 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. A spark plug 19 is provided for each cylinder on the cylinder head side of the internal combustion engine 10. The air-fuel mixture in the combustion chamber 18 is ignited by the spark discharge of the spark plug 19. The air-fuel mixture is combusted in the combustion chamber 18 and then discharged from the combustion chamber 18 to the exhaust passage 22 by opening the exhaust valve 21 as exhaust gas.
[0019]
A 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 the A / F (air-fuel ratio) of the exhaust gas is disposed upstream of the upstream side. Are provided with oxygen sensors 25 whose output voltages are inverted depending on whether the exhaust gas A / F is rich or lean with respect to the stoichiometric air-fuel ratio. Further, a crank angle sensor 27 for detecting a crank angle [° CA (Crank Angle)] that is a rotation angle of the crank shaft 26 of the internal combustion engine 10 is disposed. The engine speed NE is calculated based on the angle at which the crankshaft 26 is rotated per predetermined time. Further, the internal combustion engine 10 is provided with a water temperature sensor 28 for detecting the cooling water temperature.
[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 upstream of the A / F sensor 24. An air filter 32 is disposed on the atmosphere side of the secondary air supply passage 31, and an air pump 33 that pumps secondary air is disposed on the downstream side of the air filter 32.
[0021]
A combination valve 34 is disposed on the exhaust passage 22 side of the air pump 33. The combination valve 34 is configured by integrating a pressure-driven on-off valve 35 that opens and closes the secondary air supply passage 31 and a check valve 36 on the downstream side thereof. The on-off valve 35 of the combination valve 34 is switched between open and closed by a 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 changed between the atmospheric pressure and the intake pressure by an electromagnetically driven switching valve 38 disposed in the middle of the intake pressure introduction passage 37. Can be switched with.
[0022]
That is, when supplying secondary air, the switching valve 38 is opened to introduce the intake pressure of the intake passage 11. The on-off valve 35 is opened by introducing the intake pressure to the on-off valve 35. Thereby, 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 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 secondary air is supplied into the exhaust passage 22.
[0023]
On the other hand, when the secondary air is stopped, the air pump 33 is stopped and the switching valve 38 is switched to a 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, the pressure of the secondary air does not act on the check valve 36, and 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]
Reference numeral 40 denotes an ECU (Electronic Control Unit). The ECU 40 stores a CPU 41 as a central processing unit that executes various known arithmetic processes, a ROM 42 that stores a control program and a control map, and various data. The logical operation circuit includes a RAM 43, a B / U (backup) RAM 44, an input / output circuit 45, a bus line 46 connecting them, and the like. The above-described various sensor signals are input to the ECU 40, and control signals are output from the ECU 40 to the injector 16, the spark 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, the processing procedure of the secondary air supply abnormality detection in the CPU 41 in the ECU 40 used in the secondary air supply abnormality detection device for the internal combustion engine according to the first example of the embodiment of the present invention is shown in the flowchart of FIG. Will be described. The operation will be described with reference to FIG. Specifically, FIG. 3 shows the operation of the parameters calculated in FIG. This parameter includes 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 secondary air calculated based on these two parameters. The flow rate is QAI [g / sec: gram per second]. The 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 diagnosis conditions, the A / F sensor 24 is active, the operation conditions are steady (no sudden change), the air pump 33 changes to "ON" or "OFF" and continues for a predetermined time (from 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 based on, for example, whether the element impedance is less than a predetermined value [kΩ: kiloohm].
[0027]
When the determination condition of step S101 is satisfied, that is, when all the diagnosis 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 in operation. When the determination condition of step S102 is satisfied, that is, when the air pump 33 is operating and the secondary air is 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, and the engine supplied to the internal combustion engine 10 by the following equation (1) from the intake air amount QAFM detected by the air flow meter 12 and the fuel injection amount F supplied from the injector 16. A supply air-fuel ratio λENG is calculated (see FIG. 3). Note that 14.5 is a value near the theoretical air-fuel ratio.
[0028]
[Expression 1]
λENG ← QAFM / F / 14.5 (1)
[0029]
Next, the process proceeds to step S105, where 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, and the secondary air flow rate QAI when the air pump 33 is operating is calculated by the following equation (2) (see FIG. 3).
[0030]
[Expression 2]
QAI ← λAFS / λENG * QAFM−QAFM (2)
[0031]
Next, the process proceeds to step S107, and the secondary air flow rate QAI when the air pump 33 calculated in step S106 is operated is integrated to calculate the secondary air flow rate integrated value QAISUM. Next, the routine proceeds to step S108, where it is determined whether or not the continuation counter CON incremented at step S103 exceeds a predetermined value K1. When the determination condition of step S108 is satisfied, that is, when the continuation counter CON exceeds the predetermined value K1, the process proceeds to step S109, and the secondary air flow rate average value QAIAVE relative to the secondary air flow rate QAI when the air pump 33 is operated is 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 air pump 33 is stopped and the secondary air is not supplied, the process proceeds to step S110 and the continuation counter COFF indicating the secondary air “OFF (stop)” is set. It is incremented by “+1”. Next, the process proceeds to step S111, and the engine supplied to the internal combustion engine 10 by the above equation (1) from the intake air amount QAFM detected by the air flow meter 12 and the fuel injection amount F supplied from the injector 16. A supply air-fuel ratio λENG is calculated (see FIG. 3). Next, the process proceeds to step S112, and 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. Be turned. Next, the process proceeds to step S113, and the secondary air flow rate QERR when the air pump 33 is stopped is calculated by the following equation (4).
[0034]
[Expression 4]
QERR ← λAFS / λENG * QAFM−QAFM (4)
[0035]
Next, the process proceeds to step S114, and the secondary air flow rate QERR when the air pump 33 calculated in step S113 is stopped is integrated to calculate a secondary air flow rate integrated value QERRSUM. Next, the routine proceeds to step S115, where it is determined whether or not the continuation counter COFF incremented at step S110 exceeds a predetermined value K2. When the determination condition in step S115 is satisfied, that is, when the continuation counter COFF exceeds the predetermined value K2, the process proceeds to step S116, and the next air flow average value QERRAVE at the secondary air flow QERR when the air pump 33 is stopped is expressed by the following equation (5). ).
[0036]
[Equation 5]
QERRAVE ← QERRSUM / COFF (5)
[0037]
After the process of step S109 or step S116, the process proceeds to step S117, and the secondary air when the air pump 33 calculated in step S116 is stopped from the secondary air flow rate average value QAIAVE calculated when the air pump 33 is operated in step S109. The average flow rate value QERRAVE is subtracted to calculate the true secondary air flow rate QAIREAL. Next, the process proceeds to step S118, where 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 QAIALAL is less than the upper limit flow rate KH1, the process proceeds to step S119, and the true secondary air flow rate QAIALAL is less than the preset lower limit flow rate KL1. It is determined whether there is any. When the determination condition of step S119 is not satisfied, that is, when the true secondary air flow rate QAIRE 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 the secondary air supply system is determined to be normal. (See FIG. 3), this routine is terminated.
[0038]
On the other hand, when the determination condition in step S118 is satisfied, that is, when the true secondary air flow rate QAIRE 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). This routine is terminated. 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). This routine is terminated.
[0039]
It should be noted that when the determination condition of step S101 is not satisfied, that is, when any one of the diagnosis conditions 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 This routine is terminated without doing anything when is less than the predetermined value K1 or when the determination condition of step S115 is not satisfied, that is, when the continuation counter COFF is less than the predetermined value K2.
[0040]
As described above, the secondary air supply abnormality detection device for the internal combustion engine of the present embodiment is installed in the middle of the exhaust passage 22 of the internal combustion engine 10 to purify the 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 and a downstream side of the secondary air supply hole 31 a of the secondary air supply passage 31 in the exhaust passage 22 upstream of the three-way catalyst 23. An A / F sensor 24 as an air / fuel ratio detecting means that is disposed and detects A / F (air / fuel ratio) in exhaust gas, and a CPU 41 in an ECU 40 that estimates an engine supply air / fuel ratio λENG supplied to the internal combustion engine 10. The air-fuel ratio estimating means achieved in step (i), the engine-supplied air-fuel ratio λENG supplied to the internal combustion engine 10 estimated by the air-fuel ratio estimating means, and the secondary air are supplied from the secondary air supply mechanism 30 Detected by A / F sensor 24 Secondary air flow rate calculation means achieved by the CPU 41 in the ECU 40 for calculating the 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 And an abnormality determining means that is 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]
Further, 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 this embodiment is the secondary air flow rate QAI used for abnormality determination integrated and averaged for a predetermined period. The air flow rate average value QAIAVE is used. Then, 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 calculates the error in calculating the engine supply air-fuel ratio λENG supplied to the internal combustion engine 10. 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]
Further, the secondary air supply abnormality detection device for the internal combustion engine of this embodiment includes an air flow meter 12 as intake air amount detection means for detecting the intake air amount QAFM supplied into the intake passage 11 of the internal combustion engine 10, and the internal combustion engine. A fuel injection amount calculation means achieved by the CPU 41 in the ECU 40 for calculating the fuel injection amount F to be supplied to the engine 10 based on the intake air amount QAFM as various operation parameters and the engine rotational speed NE by the crank angle sensor 27. The engine supply air-fuel ratio λENG supplied to the internal combustion engine 10 is calculated from 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 rate average value QERRAVE when the air pump 33 is stopped from the secondary air flow rate average value QAIAVE when the air pump 33 is operating, and this true 2 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 set in advance, it is determined that the system including the secondary air supply mechanism 30 is abnormal. For this reason, an increase in cost can be suppressed by suitably correcting the secondary air flow rate variation due to a change with time and product tolerance by an existing system without installing new sensors. Further, the accuracy of determination of system abnormality including the secondary air supply mechanism 30 is improved by suitably correcting the fuel injection amount variation from the injector 16 and improving the accuracy of calculating the true secondary air flow rate QAIREAL. Can do.
[0044]
Furthermore, when 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 determines that the system including the secondary air supply mechanism 30 is abnormal, the secondary air Supply and air-fuel ratio feedback control are stopped. In addition, the secondary air supply abnormality detection device for the internal combustion engine of the present embodiment has a condition that the 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 an intake air amount In a condition where the ratio of the secondary air flow rate is small and the ratio of the secondary air flow rate is small, the diagnosis is prohibited. As a result, air-fuel ratio overcorrection due to A / F deviation can be prevented.
[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 a preset predetermined range has been described. However, the present invention is not limited to this. For example, although 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 has some abnormality. It is also possible to cope with a system abnormality in which 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 of secondary air supply abnormality detection in the CPU 41 in the ECU 40 used in the secondary air supply abnormality detection device for the 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. The secondary air supply abnormality detection routine is repeatedly executed by the CPU 41 at predetermined time intervals. Further, since the configuration of the secondary air supply abnormality detection device for the internal combustion engine according to the present embodiment is the same as the schematic diagram of FIG. 1 in the first embodiment, detailed description thereof is omitted.
[0047]
In FIG. 4, first, in step S201, 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 in the same manner as in the above-described embodiment. It is determined whether the diagnosing condition such as the continuation (time t0 to time t1 shown in FIG. 3) and the intake air amount QAFM is less than the predetermined amount α is satisfied. When the determination condition in step S201 is satisfied, that is, when all the diagnosis 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 in operation. When the determination condition of step S202 is satisfied, that is, when the air pump 33 is operating and the secondary air is supplied, the process proceeds to step S203, and the intake air amount QAFM detected by the airflow meter 12 and the injector 16 are supplied. The engine supply air-fuel ratio λENG supplied to the internal combustion engine 10 is calculated from the fuel injection amount F by the above equation (1) (see FIG. 3).
[0048]
Next, the process proceeds to step S204, and 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. Be turned. Next, the process proceeds to step S205 where 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 is operated is reduced. Calculated (the air-fuel ratio deviation between the secondary air downstream air-fuel ratio λAFS and the engine supply air-fuel ratio λENG shown in FIG. 3). Next, the routine proceeds to step S206, where the air-fuel ratio deviation amount ΔλON when the air pump 33 calculated in step S205 is operated is integrated to calculate the air-fuel ratio deviation amount integrated value ΔλONSUM.
[0049]
On the other hand, when the determination condition of step S202 is not satisfied, that is, when the air pump 33 is stopped and the secondary air is not supplied, the process proceeds to step S207 and the intake air amount QAFM detected by the air flow meter 12 and the injector 16 are transferred. The engine supply air-fuel ratio λENG supplied to the internal combustion engine 10 is calculated from the fuel injection amount F supplied by the above equation (1) (see FIG. 3). Next, the process proceeds to step S208, and the secondary air downstream air-fuel ratio λAFS downstream from 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. Be turned. Next, the process proceeds to step S209, where 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 routine proceeds to step S210, where the air-fuel ratio deviation amount ΔλOFF when the air pump 33 calculated at step S209 is stopped is integrated to calculate the air-fuel ratio deviation amount integrated value ΔλOFFSUM. After the process of step S206 or step S210, the process proceeds to step S211, and it is determined whether the predetermined time has been accumulated. When the determination condition in step S211 is satisfied, that is, when the predetermined time is integrated, the process proceeds to step S212, and the air-fuel ratio deviation amount integrated value ΔOFFSUM calculated in step S210 is changed from the air-fuel ratio deviation amount integrated value ΔONSUM calculated in step S206. The abnormality determination air-fuel ratio deviation amount integrated value ΔλREALSUM is calculated by subtraction.
[0051]
Next, the process proceeds to step S213, where it is determined whether the abnormality determination air-fuel ratio deviation integrated value ΔλREALSUM calculated in step S212 exceeds a preset upper limit value KH2. If the determination condition in step S213 is not satisfied, that is, if the abnormality determination air-fuel ratio deviation amount integrated value ΔλREALSUM is less than the upper limit value KH2, the process proceeds to step S214, and the abnormality determination air-fuel ratio deviation amount integrated value ΔλREALSUM is preset. It is determined whether it is less than the lower limit value KL2. If the determination condition in step S214 is not satisfied, that is, if the abnormality determination air-fuel ratio deviation amount integrated value ΔλREALSUM 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 is normal. This routine is terminated.
[0052]
On the other hand, when the determination condition of step S213 is satisfied, that is, when the abnormality determination air-fuel ratio deviation integrated value ΔλREALSUM exceeds the upper limit KH2, 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. End the routine. It should be noted that when the determination condition of step S201 is not satisfied, that is, when any one of the diagnosis conditions is not satisfied (before time t1 shown in FIG. 3), or the determination condition of step S211 is not satisfied, that is, integration for a predetermined time. If not, the routine ends without doing anything.
[0053]
As described above, the secondary air supply abnormality detection device for the internal combustion engine of the present embodiment is installed in the middle of the exhaust passage 22 of the internal combustion engine 10 to purify the 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 and a downstream side of the secondary air supply hole 31 a of the secondary air supply passage 31 in the exhaust passage 22 upstream of the three-way catalyst 23. An A / F sensor 24 as an air / fuel ratio detecting means that is disposed and detects A / F (air / fuel ratio) in exhaust gas, and a CPU 41 in an ECU 40 that estimates an engine supply air / fuel ratio λENG supplied to the internal combustion engine 10. The air-fuel ratio estimating means achieved in step (i), the engine-supplied air-fuel ratio λENG supplied to the internal combustion engine 10 estimated by the air-fuel ratio estimating means, and the secondary air are supplied from the secondary air supply mechanism 30 Detected by A / F sensor 24 And an abnormality determination means that is 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 with the secondary air downstream air-fuel ratio λAFS. is there.
[0054]
Further, the abnormality determination means achieved by the CPU 41 in the ECU 40 of the secondary air supply abnormality detection apparatus for the internal combustion engine of the present embodiment is the 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. Then, 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 uses the calculation error of the air-fuel ratio deviation amount ΔλON as the engine supply supplied to the internal combustion engine 10. The correction is based on the air-fuel ratio deviation amount ΔλOFF between the air-fuel ratio λENG 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. is there.
[0055]
Further, the secondary air supply abnormality detection device for the internal combustion engine of this embodiment includes an air flow meter 12 as intake air amount detection means for detecting the intake air amount QAFM supplied into the intake passage 11 of the internal combustion engine 10, and the internal combustion engine. A fuel injection amount calculation means achieved by the CPU 41 in the ECU 40 for calculating the fuel injection amount F to be supplied to the engine 10 based on the intake air amount QAFM as various operation parameters and the engine rotational speed NE by the crank angle sensor 27. The engine supply air-fuel ratio λENG supplied to the internal combustion engine 10 is calculated from the intake air amount QAFM and the fuel injection amount F.
[0056]
That is, the air-fuel ratio deviation amount integrated value ΔλOFFSUM when the air pump 33 is stopped is subtracted from the air-fuel ratio deviation amount integrated value ΔλONSUM when the air pump 33 is operated and corrected, thereby calculating the abnormality determination air-fuel ratio deviation amount integrated value ΔλREALSUM. When the abnormality determination air-fuel ratio deviation integrated value ΔλREALSUM is not between the upper limit value KH2 and the lower limit value KL2 within a predetermined range, it is determined that the system including the secondary air supply mechanism 30 is abnormal. For this reason, an increase in cost can be suppressed by suitably correcting the secondary air flow rate variation due to a change with time and product tolerance by an existing system without installing new sensors. Further, the fuel injection amount variation or the like by the injector 16 is suitably corrected and the calculation accuracy of the abnormality determination air-fuel ratio deviation integrated value ΔλREALSUM is improved, thereby improving the determination accuracy of the system abnormality including the secondary air supply mechanism 30. can do.
[0057]
Furthermore, when 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 determines that the system including the secondary air supply mechanism 30 is abnormal, the secondary air Supply and air-fuel ratio feedback control are stopped. In addition, the secondary air supply abnormality detection device for the internal combustion engine of the present embodiment has a condition that the 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 an intake air amount In a condition where the ratio of the secondary air flow rate is small and the ratio of the secondary air flow rate is small, the diagnosis is prohibited. As a result, air-fuel ratio overcorrection due to A / F deviation can be prevented.
[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 example and a second example of an embodiment of the invention is applied and its peripheral devices. It is.
FIG. 2 shows a processing procedure for detecting a secondary air supply abnormality in a CPU in an ECU used in a secondary air supply abnormality detection device for an internal combustion engine according to a first example of an embodiment of the present invention; It is a flowchart to show.
FIG. 3 is a time chart showing a transition state of the engine supply air-fuel ratio, the secondary air downstream air-fuel ratio, and the secondary air flow rate corresponding to the processing of FIG. 2;
FIG. 4 shows a processing procedure for detecting a secondary air supply abnormality in a CPU in an ECU used in a secondary air supply abnormality detection device for an internal combustion engine according to a second example of an embodiment of the present invention; It is a flowchart to show.
[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 (6)

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;
An air-fuel ratio detecting means disposed downstream of the secondary air supply hole in the exhaust passage upstream of the catalyst and detecting an air-fuel ratio in the exhaust gas;
Air-fuel ratio estimating 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 estimation means and the air-fuel ratio detected by the air-fuel ratio detection means when 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;
An 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 ;
Intake air amount detection means for detecting the amount of intake air supplied into the 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 abnormality determination means calculates an error in calculating the air-fuel ratio supplied to the internal combustion engine when the air-fuel ratio supplied to the internal combustion engine and the secondary air from the secondary air supply mechanism are not supplied. The air-fuel ratio calculated by the detecting means and the secondary air flow rate calculated by the secondary air flow rate calculating means is corrected, and the air-fuel ratio supplied to the internal combustion engine is the intake air amount And a secondary air supply abnormality detection device for an internal combustion engine, wherein the abnormality is calculated from the fuel injection amount . 2. The secondary air supply abnormality detection apparatus for an internal combustion engine according to claim 1, wherein the abnormality determination unit uses the secondary air flow rate used for abnormality determination as an average value or an integrated value for a predetermined period. 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;
An air-fuel ratio detecting means disposed downstream of the secondary air supply hole in the exhaust passage upstream of the catalyst and detecting an air-fuel ratio in the exhaust gas;
An air-fuel ratio deviation amount 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 is set to a predetermined value. When it is not within the range, an abnormality determining means for determining that the system including the secondary air supply mechanism is abnormal ;
Intake air amount detection means for detecting the amount of intake air supplied into the 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 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 are not supplied from the secondary air supply mechanism The air-fuel ratio is corrected on the basis of the air-fuel ratio deviation amount from the air-fuel ratio, and the air-fuel ratio supplied to the internal combustion engine is calculated from the intake air amount and the fuel injection amount. Secondary air supply abnormality detection device. 4. The secondary air supply abnormality detection device for an internal combustion engine according to claim 3 , wherein the abnormality determination means uses the air-fuel ratio deviation amount used for abnormality determination as an average value or an integrated value over a predetermined period. The abnormality determining means, when it is determined that system abnormalities including the secondary air supply mechanism, an internal combustion engine according to claim 1 or claim 3, characterized in that to stop the secondary air supply and the air-fuel ratio feedback control 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 where the secondary air flow rate is unstable, or the condition where the intake air amount is large and the ratio of the secondary air flow rate is small, the diagnosis (Diagnosis: secondary air supply abnormality detecting device for an internal combustion engine according to claim 1 or claim 3, characterized in that prohibiting diagnosis).

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