JP2008025366A - Control device of secondary air supply system for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately estimate a secondary air flow rate without having sensors for measuring the secondary air flow rate (or secondary air pressure), in a secondary air supply system for an internal combustion engine. <P>SOLUTION: Based on an excess air ratio (air-fuel ratio) detected by an air-fuel ratio sensor 16 during a secondary air supply period, a fuel injection amount, and an intake air amount, a secondary air flow rate estimate value during the secondary air supply period is calculated. Based on the excess air ratio (air-fuel ratio) detected by an air-fuel ratio sensor 16 during the secondary air supply period, a fuel injection amount, and an intake air amount, the secondary air flow rate estimate value during the secondary air supply period is calculated, and the secondary air flow rate estimate value during the secondary air supply period is detected as an estimated error of the secondary air flow rate. Then, the secondary air flow rate estimate value during the secondary air supply period is corrected by the estimated error of the secondary air flow rate detected during the secondary air supply period so as to acquire a final secondary air flow rate estimate value. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a control device for a secondary air supply system of an internal combustion engine that supplies secondary air to an exhaust passage of the internal combustion engine for early warm-up of a catalyst or the like.

  For example, as shown in Patent Document 1 (Japanese Patent Laid-Open No. 2003-83048) and Patent Document 2 (Japanese Patent Laid-Open No. 2004-11585), the exhaust gas purification catalyst in the exhaust pipe of the internal combustion engine is upstream of the exhaust gas. In addition, there is known a technique in which secondary air is supplied by an air pump to promote purification (oxidation reaction) of HC and CO in exhaust gas, or to accelerate catalyst warm-up by the reaction heat.

  When such a secondary air supply system breaks down, exhaust emission deteriorates. Therefore, in Patent Documents 1 and 2, a pressure sensor is installed in the secondary air supply pipe, and the pressure of the secondary air detected by this pressure sensor is reduced. Based on this, the abnormality diagnosis of the secondary air supply system is performed.

  However, this configuration has a drawback in that the pressure sensor needs to be installed in the secondary air supply pipe, which increases the cost accordingly.

Therefore, as shown in Patent Document 3 (Japanese Patent No. 3482019), the air-fuel ratio (ratio between the intake air amount and the fuel injection amount) of the air-fuel mixture supplied to the internal combustion engine during the secondary air supply period and the air-fuel ratio sensor The secondary air flow rate is calculated based on the detected air-fuel ratio and the intake air amount, and the operation state of the secondary air supply system is monitored based on the secondary air flow rate.
JP 2003-83048 A JP 2004-11585 A Japanese Patent No. 3482019

  In the technique of Patent Document 3, the air-fuel ratio supplied to the internal combustion engine (ratio between the intake air amount and the fuel injection amount), the air-fuel ratio detected by the air-fuel ratio sensor, and the intake air amount during the secondary air supply period. Although the secondary air flow rate is calculated, the supply air-fuel ratio and the air-fuel ratio sensor detected air are affected by the individual differences (manufacturing variation, change over time, etc.) of the fuel injection valve, air-fuel ratio sensor, and intake air amount sensor. Since it is inevitable that the data on the fuel ratio and the intake air amount will vary, it is difficult to accurately calculate the secondary air flow rate.

  The present invention has been made in view of such circumstances. Therefore, the object of the present invention is to estimate the secondary air flow rate based on the air-fuel ratio detected by the air-fuel ratio sensor, the fuel injection amount, and the intake air amount. In the provided secondary air supply system, the estimation error of the secondary air flow rate caused by individual differences (manufacturing variation, change with time, etc.) of the fuel injection valve, the air-fuel ratio sensor, and the intake air amount sensor can be accurately detected. It is an object of the present invention to provide a control device for a secondary air supply system of an internal combustion engine capable of performing the above.

  In order to achieve the above object, an invention according to claim 1 is provided with an air-fuel ratio sensor for detecting an air-fuel ratio of exhaust gas in an exhaust passage of an internal combustion engine, and moreover than the air-fuel ratio sensor in the exhaust passage. In a control device for a secondary air supply system of an internal combustion engine that supplies secondary air to the upstream side, a secondary air supply system that supplies air into the exhaust passage based on an air-fuel ratio detected by the air-fuel ratio sensor, a fuel injection amount, and an intake air amount. A secondary air flow rate estimating means for estimating a secondary air flow rate, and a secondary air flow rate estimating means for estimating a secondary air flow rate by the secondary air flow rate estimating means during a secondary air supply stop period, An estimation error detecting means for detecting as an estimation error is provided.

  During the secondary air supply stop period, the supply of secondary air into the exhaust passage is completely stopped and the true value of the secondary air flow rate becomes zero. If the flow rate is estimated and the estimated value of the secondary air flow rate is compared with the true value (= 0), the estimation error of the secondary air flow rate (= estimated value−true value = estimated value) from the difference between the two. Can be obtained with high accuracy. Therefore, as in the present invention, during the secondary air supply stop period (that is, during the period when the true value of the secondary air flow rate is 0), the secondary air flow rate is estimated, and the estimated value is used as the secondary air flow rate. If it is detected as an estimation error of the flow rate, it can accurately detect the estimation error of the secondary air flow rate caused by individual differences (manufacturing variation, change over time, etc.) of the fuel injection valve, air-fuel ratio sensor, and intake air amount sensor. Can do.

  According to the second aspect of the present invention, the final secondary air flow rate is obtained by correcting the secondary air flow rate estimated during the secondary air supply period by the estimated error detected by the estimation error detecting means. It is good to make it. In this way, it is possible to accurately detect the secondary air flow rate without being affected by individual differences (manufacturing variation, temporal change, etc.) among the fuel injection valve, the air-fuel ratio sensor, and the intake air amount sensor. As a result, the secondary air flow rate can be accurately estimated without newly providing dedicated sensors for measuring the secondary air flow rate (or secondary air pressure), and there is a demand for cost reduction. It is possible to improve the estimation accuracy of the secondary air flow rate while satisfying.

  Further, according to the present invention, as in claim 3, an abnormality diagnosis means for performing an abnormality diagnosis of the secondary air supply system based on the final secondary air flow rate corrected by the estimated error is provided. good. In this way, it is possible to accurately perform abnormality diagnosis of the secondary air supply system without newly providing dedicated sensors for measuring the secondary air flow rate (or secondary air pressure). Therefore, it is possible to improve the abnormality diagnosis accuracy of the secondary air supply system while satisfying the demand for cost reduction.

Hereinafter, an embodiment embodying the best mode for carrying out the present invention will be described.
First, a schematic configuration of the entire system will be described with reference to FIG.
A fuel injection valve 13 that injects fuel is attached in the vicinity of the intake port of the intake manifold 12 of each cylinder of the engine 11 that is an internal combustion engine. On the other hand, the exhaust pipe 14 (exhaust passage) of the engine 11 is provided with a catalyst 15 such as a three-way catalyst for purifying CO, HC, NOx, etc. in the exhaust gas. An air-fuel ratio sensor 16 that detects the air-fuel ratio is provided.

  Next, the configuration of the secondary air supply system 17 that supplies secondary air to the upstream side of the air-fuel ratio sensor 16 in the exhaust pipe 14 (for example, near the exhaust port) will be described. The secondary air supply system 17 distributes the secondary air discharged from an air pump 18 driven by an electric motor to a secondary air supply nozzle 20 of each cylinder through a secondary air pipe 19 so that an exhaust manifold (exhaust gas) of each cylinder. Introduced into the aisle). The secondary air pipe 19 is provided with a control valve 21 for opening and closing the secondary air pipe 19.

  The air pump 18 and the control valve 21 of the secondary air supply system 17 are controlled by a control circuit (hereinafter referred to as “ECU”) 23. The ECU 23 reads the output signals of various sensors (for example, the rotation angle sensor 24, the intake air amount sensor 25, the water temperature sensor 26, etc.) that detect the engine operating state, and the engine rotation speed, the intake air amount, the cooling water temperature, etc. The engine operating state is detected, and the fuel injection amount and ignition timing are controlled according to the engine operating state.

  The ECU 23 executes a secondary air supply control program (not shown) to turn on the air pump 18 and open the control valve 21 when a predetermined secondary air supply control execution condition is satisfied. Secondary air supply control for supplying secondary air to the exhaust pipe 14 is started, and the air pump 18 is turned off when the secondary air supply control execution condition is not satisfied or when a predetermined secondary air supply execution period has elapsed. At the same time, the control valve 21 is closed to stop the supply of secondary air. FIG. 2 shows the behavior of the detected air-fuel ratio, supply air-fuel ratio, and estimated secondary air flow rate of the air-fuel ratio sensor 16 during the secondary air supply period and the secondary air supply stop period.

  Further, the ECU 23 executes a secondary air supply system abnormality diagnosis program shown in FIG. 3 to be described later, whereby the excess air ratio λout (A) detected by the air-fuel ratio sensor 16 during the secondary air supply period and the fuel injection amount Fin. Based on (A) and the intake air amount Qin (A), the secondary air flow rate estimated value Qap (A) during the secondary air supply period is calculated and detected by the air-fuel ratio sensor 16 during the secondary air supply stop period. Based on the excess air ratio λout (B), the fuel injection amount Fin (B), and the intake air amount Qin (B), the estimated secondary air flow rate Qap (B) during the secondary air supply stop period is calculated. The estimated value Qap (B) is detected as an estimation error of the secondary air flow rate, and the secondary air flow rate estimated value Qap (A) calculated during the secondary air supply period is detected during the secondary air supply period. A final secondary air flow rate estimated value Qap (AB) is obtained by correcting the secondary air flow rate by an estimated error Qap (B).

Specifically, the secondary air flow rate estimated value Qap (A) during the secondary air supply period is calculated by the following equation.
Qap (A) = {λout (A) / λin (A)} × Qin (A) −Qin (A) (1)

In the above equation, λin (A) is the excess air ratio of the air-fuel mixture supplied to the engine 11 during the secondary air supply period, and the intake air amount Qin (A) and the fuel injection amount Fin during the secondary air supply period It is calculated by the following equation from (A) and the theoretical air fuel ratio (target air fuel ratio).
λin (A) = Qin (A) / {Fin (A) × theoretical air-fuel ratio} (2)
Here, the theoretical air-fuel ratio is 14.7.

  The first term {λout (A) / λin (A)} × Qin (A) on the right side of the above (1) corresponds to the exhaust flow rate during the secondary air supply period, and the intake air amount Qin ( By subtracting A), the estimated secondary air flow rate Qap (A) during the secondary air supply period is obtained.

Substituting the above equation (2) into the equation (1) and rearranging it leads to the following equation.
Qap (A) = λout (A) × Fin (A) × theoretical air-fuel ratio−Qin (A) (3)
Further, a secondary air flow rate estimation error Qap (B) that is an estimated value of the secondary air flow rate during the secondary air supply stop period is calculated by the following equation.
Qap (B) = {λout (B) / λin (B)} × Qin (B) −Qin (B) (4)

In the above equation, λin (B) is the excess air ratio of the air-fuel mixture supplied to the engine 11 during the secondary air supply stop period, and the intake air amount Qin (B) and fuel injection during the secondary air supply stop period It is calculated from the amount Fin (B) and the theoretical air fuel ratio (target air fuel ratio) by the following equation.
λin (B) = Qin (B) / {Fin (B) × theoretical air-fuel ratio} (5)

The first term {λout (B) / λin (B)} × Qin (B) on the right side of the above (3) corresponds to the exhaust flow rate during the secondary air supply stop period. From this exhaust flow rate, the intake air amount Qin By subtracting (B), the secondary air flow rate estimate Qap (B) during the secondary air supply stop period is estimated, and this secondary air flow rate estimate Qap (B) is estimated as the secondary air flow rate estimation error. Is detected.
Substituting the above equation (5) into the equation (4) and rearranging it leads to the following equation.
Qap (B) = λout (B) × Fin (B) × theoretical air-fuel ratio−Qin (B) (6)

  During the secondary air supply stop period, the supply of the secondary air into the exhaust pipe 14 is completely stopped and the true value of the secondary air flow rate becomes 0. Therefore, the secondary air supply is stopped during the secondary air supply stop period. If the estimated air flow rate value Qap (B) is calculated and the estimated secondary air flow rate value Qap (B) is compared with the true value (= 0), the estimated error (= (Estimated value−true value = estimated value) Qap (B) can be obtained with high accuracy.

  By subtracting the secondary air flow rate estimated value (secondary air flow rate estimation error) Qap (B) during the secondary air supply stop period from the secondary air flow rate estimated value Qap (A) during the secondary air supply period, The final estimated secondary air flow rate Qap (AB) is obtained.

Qap (AB) = Qap (A)-Qap (B)
= [{Λout (A) / λin (A)} × Qin (A) −Qin (A)]
− [{Λout (B) / λin (B)} × Qin (B) −Qin (B)]
= {Λout (A) × Fin (A) × theoretical air-fuel ratio−Qin (A)}
− {Λout (B) × Fin (B) × theoretical air / fuel ratio−Qin (B)} (7)

Since the fuel injection amounts Fin (A) and Fin (B) cannot be actually measured, the required fuel injection amounts calculated by the ECU 23 may be directly used as the fuel injection amounts Fin (A) and Fin (B).
Further, the relationship between the detected excess air ratio λ and the detected air-fuel ratio is defined by the following equation.
Detected air excess ratio λ = Detected air / fuel ratio / theoretical air / fuel ratio (8)

Therefore, the supply air-fuel ratio and the detected air-fuel ratio during the secondary air supply period are AFin (A) and AFout (A), respectively, and the supply air-fuel ratio and the detected air-fuel ratio during the secondary air supply stop period are respectively AFin (B), Assuming that AFout (B), the secondary air flow rate estimated value Qap (A) during the secondary air supply period and the secondary air flow rate estimation error Qap (B) which is the secondary air flow rate estimated value during the secondary air supply stop period ) Is calculated by the following equation.
Qap (A) = {AFout (A) / AFin (A)} × Qin (A) −Qin (A) (9)
Qap (B) = {AFout (B) / AFin (B)} × Qin (B) −Qin (B) (10)

Here, the supply air-fuel ratio AFin (A) during the secondary air supply period is calculated from the intake air amount Qin (A) and the fuel injection amount Fin (A) during the secondary air supply period by the following equation.
AFin (A) = Qin (A) / Fin (A) (11)
Substituting this equation (11) into the above equation (9) and rearranging it leads to the following equation.
Qap (A) = AFout (A) × Fin (A) −Qin (A) (12)

Similarly, the supply air-fuel ratio AFin (B) during the secondary air supply stop period is calculated by the following equation from the intake air amount Qin (B) and the fuel injection amount Fin (B) during the secondary air supply stop period. The
AFin (B) = Qin (B) / Fin (B) (13)
Substituting this equation (13) into the above equation (10) and rearranging it leads to the following equation.
Qap (B) = AFout (B) × Fin (B) −Qin (B) (14)

Therefore, a corrected secondary air flow rate estimated value Qap (AB) obtained by removing the secondary air flow rate estimation error Qap (B) is obtained from the above formulas (12) and (14) by the following formula.
Qap (AB) = Qap (A)-Qap (B)
= {AFout (A) × Fin (A) −Qin (A)}
− {AFout (B) × Fin (B) −Qin (B)} (15)

  Further, in the present embodiment, the corrected secondary air flow rate estimated value Qap (B) from which the secondary air flow rate estimation error Qap (B) is removed is compared with the abnormality determination threshold value, and the corrected secondary air flow rate estimated value Qap is compared. Whether or not the secondary air supply system 17 is abnormal is determined based on whether or not (AB) is smaller than the abnormality determination threshold value. In this case, the abnormality determination threshold value may be a fixed value that is adapted in advance. However, if the exhaust pressure of the engine 11 acting on the outlet of the secondary air supply nozzle 20 varies during the supply of the secondary air, Considering that the flow rate of the secondary air flowing into the exhaust pipe 14 from the secondary air supply system 17 varies, the abnormality determination threshold is mapped according to a parameter (for example, intake air amount) that causes the exhaust pressure to vary. It may be set by, for example.

  The calculation process of the corrected secondary air flow rate Qap (A-B) and the abnormality diagnosis of the secondary air supply system 17 described above are executed by the ECU 23 as follows in accordance with the secondary air supply system abnormality diagnosis program of FIG. This program is executed at a predetermined cycle during engine operation. First, in step 101, it is determined whether secondary air is being supplied (the air pump 18 is on and the control valve 21 is open). If it is medium, the routine proceeds to step 102 where the excess air ratio λout (A) detected by the air-fuel ratio sensor 16 during the supply of secondary air, the fuel injection amount Fin (A) injected from the fuel injection valve 13, and the intake air amount. The intake air amount Qin (A) detected by the sensor 25 is read.

Thereafter, the process proceeds to step 103, and the secondary air flow rate estimated value Qap (A) during the secondary air supply period is calculated by the following equation.
Qap (A) = λout (A) x Fin (A) x Theoretical air-fuel ratio-Qin (A)

  As shown in FIG. 2, the detected excess air ratio λout (A) of the air-fuel ratio sensor 16 oscillates due to noise superimposed on the output of the air-fuel ratio sensor 16, fluctuations in the flow state of exhaust gas around the air-fuel ratio sensor 16, and the like. Further, since the fuel injection amount Fin (A) (excess air supply rate) also vibrates due to the vibration of the pressure of the fuel supplied to the fuel injection valve 13, etc., the secondary air flow rate estimated value Qap ( A) also results in vibration. As a countermeasure, calculate the average value (or smoothing value) of the detected excess air ratio λout (A) and the average value (or smoothing value) of the fuel injection amount Fin (A) during the specified period during the supply of secondary air. Then, the secondary air flow rate estimated value Qap (A) may be calculated using the average value (or the smoothed value) thereof, or it may be determined within a predetermined period during the supply of secondary air. The average value, the smoothed value, and the integrated value of the estimated secondary air flow rate Qap (A) repeatedly calculated at the calculation cycle may be calculated. In this way, it is possible to obtain data on the average or intermediate secondary air flow rate estimated value Qap (A) within a predetermined period during the supply of secondary air, and the detected excess air ratio λout (A) or It is possible to acquire data on the reliable secondary air flow rate estimated value Qap (A) that eliminates the influence of the vibration of the fuel injection amount Fin (A) as much as possible.

  However, the present invention calculates the secondary air flow rate estimated value Qap (A) using the instantaneous value of the excess air ratio λout (A) and the fuel injection amount Fin (A) detected at a predetermined timing during the supply of the secondary air. It is not excluded from the technical scope of the present invention that the configuration is performed only once. This is because the excess air ratio λout (A) and the fuel injection amount Fin (A) from which the vibration component is removed can be detected by filtering the output of the air-fuel ratio sensor 16 and the signal of the fuel injection amount Fin (A). is there.

  On the other hand, if it is determined in step 101 that the secondary air is not being supplied, the routine proceeds to step 104, where it is determined whether or not the secondary air flow rate estimated value Qap (A) during the secondary air supply period has been calculated. If the secondary air flow rate estimated value Qap (A) during the secondary air supply period has not been calculated yet, the program is terminated without performing the subsequent processing.

  On the other hand, if it is determined in step 104 that the secondary air flow rate estimated value Qap (A) during the secondary air supply period has been calculated, the process proceeds to step 105, where the empty air supply is stopped during the secondary air supply stop period. The excess air ratio λout (B) detected by the fuel ratio sensor 16, the fuel injection amount Fin (B) injected from the fuel injection valve 13, and the intake air amount Qin (B) detected by the intake air amount sensor 25 are read.

Thereafter, the routine proceeds to step 106, where the secondary air flow rate estimated value (secondary air flow rate estimation error) Qap (B) during the secondary air supply stop period is calculated by the following equation.
Qap (B) = λout (B) x Fin (B) x Theoretical air-fuel ratio-Qin (B)

  Also in this case, the average value (or smoothing value) of the detected excess air ratio λout (B) and the average value (or smoothing value) of the fuel injection amount Fin (B) within the predetermined period during the secondary air supply stoppage are calculated. The secondary air flow rate estimation error Qap (B) may be calculated using the average value (or the smoothed value) of these values, or within a predetermined period when the secondary air supply is stopped. Alternatively, the average value, the smoothed value, and the integrated value of the secondary air flow rate estimation error Qap (B) repeatedly calculated at a predetermined calculation cycle may be calculated. The processing in step 106 serves as an estimation error detection means in the claims.

After calculating the secondary air flow estimation error Qap (B), proceed to step 107 and subtract the secondary air flow estimation error Qap (B) from the secondary air flow estimation value Qap (A) during the secondary air supply period. Then, the corrected secondary air flow rate estimated value Qap (AB) is obtained.
Qap (AB) = Qap (A)-Qap (B)
The processes in steps 101 to 107 described above serve as secondary air flow rate estimation means in the claims.

  Thereafter, the routine proceeds to step 108, where the corrected secondary air flow rate estimated value Qap (AB) is compared with the abnormality determination threshold value, and the corrected secondary air flow rate estimated value Qap (AB) must be less than the abnormality determination threshold value. For example, it is determined that the flow rate of the secondary air flowing into the exhaust pipe 14 from the secondary air supply system 17 is abnormally small, and the process proceeds to step 109 to determine that the secondary air supply system 17 is abnormal.

  On the other hand, if it is determined in step 108 that the corrected secondary air flow rate estimated value Qap (AB) is greater than or equal to the abnormality determination threshold value, the secondary air flowing into the exhaust pipe 14 from the secondary air supply system 17. It is determined that the air flow rate is within the normal range, the process proceeds to step 110, and it is determined that the secondary air supply system 17 is normal. Note that the processing from step 108 to step 110 serves as abnormality diagnosis means in the claims.

  In this program, the secondary air flow rate estimation error Qap (B) is calculated after the secondary air supply is completed. However, before the secondary air supply is started, the secondary air flow rate estimation error Qap (B ) May be calculated, and then the exhaust flow rate Qout (A) at the time of secondary air supply may be calculated.

  Alternatively, the secondary air flow rate estimation error Qap (B) may be stored in a rewritable nonvolatile memory such as a backup RAM for learning. In this case, the secondary air flow estimation error Qap (B) is learned for each engine operating condition, and the secondary air flow estimation error corresponding to the engine operating condition at the time when the secondary air flow estimated value Qap (A) is calculated. The learned value of Qap (B) may be read from the memory and the secondary air flow rate estimated value Qap (A) may be corrected. Of course, it goes without saying that the secondary air flow rate estimation error Qap (B) may be learned regardless of the engine operating conditions.

  According to the present embodiment described above, during the secondary air supply stop period, the supply of secondary air into the exhaust pipe 14 is completely stopped and the true value of the secondary air flow rate becomes zero. Paying attention, the secondary air flow rate estimated value Qap (B) is calculated during the secondary air supply stop period, and the secondary air flow rate estimated value Qap (B) is compared with the true value (= 0). Since an estimation error (= estimated value−true value = estimated value) of the secondary air flow rate is detected, during the secondary air supply stop period (that is, during the period when the true value of the secondary air flow rate is 0) ), It is possible to accurately detect a secondary air flow rate estimation error caused by individual differences (manufacturing variation, temporal change, etc.) among the fuel injection valve 13, the air-fuel ratio sensor 16, and the intake air amount sensor.

  Then, the secondary air flow rate estimated value Qap (A) calculated during the secondary air supply period is corrected by the secondary air flow rate estimation error Qap (B) to obtain the final secondary air flow rate estimated value Qap (AB Therefore, the secondary air flow rate can be accurately detected without being affected by individual differences (manufacturing variation, change with time, etc.) of the fuel injection valve 13, the air-fuel ratio sensor 16, and the intake air amount sensor. it can. As a result, the secondary air flow rate can be accurately estimated without newly providing dedicated sensors for measuring the secondary air flow rate (or secondary air pressure), and there is a demand for cost reduction. It is possible to improve the estimation accuracy of the secondary air flow rate while satisfying.

  Further, in the present embodiment, the final secondary air flow rate estimated value Qap (AB) corrected by the secondary air flow rate estimation error Qap (B) is compared with the abnormality determination threshold value, so that the secondary air supply system 17 Since the presence / absence of abnormality is determined, the abnormality diagnosis of the secondary air supply system 17 can be accurately performed without providing a dedicated sensor for measuring the secondary air flow rate (or secondary air pressure). It can be executed well and the abnormality diagnosis accuracy of the secondary air supply system 17 can be improved while satisfying the demand for cost reduction.

  In the present embodiment, the present invention is applied to the secondary air supply system 17 including the air pump 18 driven by an electric motor. However, the present invention includes an air pump driven via an electromagnetic clutch by the power of the engine 11 or the like. The present invention may be applied to a secondary air supply system.

It is a schematic block diagram of the whole system in one Example of this invention. It is a time chart which shows the behavior of the detection λ and supply λ of the air-fuel ratio sensor and the estimated secondary air flow rate when the secondary air is supplied and when the secondary air supply is stopped. It is a flowchart which shows the flow of a process of a secondary air supply system abnormality diagnosis program.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Engine (internal combustion engine), 12 ... Intake manifold, 13 ... Fuel injection valve, 14 ... Exhaust pipe (exhaust passage), 15 ... Catalyst, 16 ... Air-fuel ratio sensor, 17 ... Secondary air supply system, 18 ... Air pump, DESCRIPTION OF SYMBOLS 19 ... Secondary air piping, 20 ... Secondary air supply nozzle, 21 ... Control valve, 23 ... ECU (Secondary air flow rate estimation means, estimation error detection means, abnormality diagnosis means)

Claims (3)

An air-fuel ratio sensor for detecting the air-fuel ratio of the exhaust gas is installed in the exhaust passage of the internal combustion engine, and the secondary air supply of the internal combustion engine that supplies secondary air upstream of the air-fuel ratio sensor in the exhaust passage In the system control unit,
Secondary air flow rate estimating means for estimating a secondary air flow rate to be supplied into the exhaust passage based on the air / fuel ratio detected by the air / fuel ratio sensor, the fuel injection amount, and the intake air amount;
An estimation error detecting means for estimating a secondary air flow rate by the secondary air flow rate estimating means during a secondary air supply stop period and detecting the estimated value as an estimation error of the secondary air flow rate estimating means. A control device for a secondary air supply system of an internal combustion engine.   The secondary air flow rate estimation means corrects the secondary air flow rate estimated during the secondary air supply period by the estimated error detected by the estimation error detection means to obtain a final secondary air flow rate. The control device for a secondary air supply system of an internal combustion engine according to claim 1.   The internal combustion engine according to claim 2, further comprising an abnormality diagnosis unit that performs an abnormality diagnosis of the secondary air supply system based on a final secondary air flow rate corrected by the estimated error. Secondary air supply system control device.

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