JP3855720B2 - Abnormality diagnosis device for catalyst early warm-up control system of internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an abnormality diagnosis device for an early catalyst warm-up control system for an internal combustion engine that diagnoses the presence or absence of an abnormality in an early catalyst warm-up control system that promotes warm-up of an exhaust gas purification catalyst for an internal combustion engine.
[0002]
[Prior art]
Recent automobiles are equipped with a catalyst such as a three-way catalyst to purify exhaust gas, but this catalyst has a low exhaust gas purification rate until it is warmed up to the activation temperature after the engine is started. Until the catalyst is warmed up to the activation temperature after the engine is started, the catalyst early warm-up control is executed by ignition timing retardation control or the like to increase the exhaust heat amount and warm the catalyst in a short time.
[0003]
[Problems to be solved by the invention]
If the catalyst early warm-up control system described above is operating normally, exhaust emissions after engine startup can be reduced considerably. However, if the catalyst early warm-up control system operates abnormally, the catalyst warms up to the activation temperature. It takes a long time to be used, and the exhaust emission becomes worse accordingly. Therefore, if the operation of the early catalyst warm-up control system becomes abnormal, it is desirable to detect it early so that repairs etc. can be performed early. A method for automatically diagnosing whether or not it is functioning properly has not been developed, so even if the operation of the early catalyst warm-up control system becomes abnormal, the driver continues to operate without notice of the abnormality at all. There is a problem that it ends up.
[0004]
The present invention has been made in view of such circumstances, and therefore the object thereof is an internal combustion engine having a function of automatically diagnosing the presence or absence of an abnormality in the catalyst early warm-up control system during operation of the internal combustion engine. An object of the present invention is to provide an abnormality diagnosis device for a catalyst early warm-up control system.
[0005]
[Means for Solving the Problems]
In order to achieve the above object, an abnormality diagnosis device for a catalyst early warm-up control system for an internal combustion engine according to claim 1 of the present invention comprises catalyst early warm-up control means for promoting warm-up of a catalyst for exhaust gas purification, An abnormality diagnosis means for diagnosing whether or not the catalyst early warm-up control means is operating normally; and an exhaust gas component detection means for detecting an exhaust gas component downstream of the catalyst, the abnormality diagnosis means The presence / absence of abnormality of the catalyst early warm-up control means is diagnosed based on the exhaust gas component detected by the exhaust gas component detection means.
[0006]
Since the purification rate of the exhaust gas passing through the catalyst changes according to the progress of the catalyst warm-up (activity level), the exhaust gas component detection means on the downstream side of the catalyst depends on the progress of the catalyst warm-up. The flowing exhaust gas component (for example, oxygen concentration, air-fuel ratio, etc.) changes, and the detection value of the exhaust gas component detection means on the downstream side of the catalyst changes accordingly. From this relationship, it is determined whether the progress of catalyst warm-up is normal or delayed based on the exhaust gas component detected by the exhaust gas component detection means on the downstream side of the catalyst during early catalyst warm-up control. If it is determined that the catalyst warm-up is delayed, it is diagnosed that the catalyst early warm-up control means is abnormal. In this case, the exhaust gas component detection means on the downstream side of the catalyst only needs to use a sensor installed for air-fuel ratio control, so there is no need to provide a new sensor such as a catalyst temperature sensor, thereby reducing costs. While satisfying the requirements, abnormality diagnosis of the catalyst early warm-up control means can be automatically performed during operation of the internal combustion engine.
[0007]
By the way, if the catalyst is used for a long period of time, the purification characteristics deteriorate, so even if the catalyst warm-up progress during the early catalyst warm-up control is normal, The purification rate of the exhaust gas passing therethrough is lower than usual. For this reason, when the catalyst is deteriorated and when the warm-up of the catalyst is delayed, the behavior of the exhaust gas purification rate during the early catalyst warm-up control (the detected value of the exhaust gas component detecting means downstream of the catalyst) In some cases, it may be difficult to distinguish between the two only from the detection value of the exhaust gas component detection means on the downstream side of the catalyst during the early catalyst warm-up control.
[0008]
In view of this point, in the invention according to claim 1 , the abnormality diagnosis means is based on the exhaust gas component detected by the exhaust gas component detection means during the catalyst early warm-up control by the catalyst early warm-up control means. First abnormality diagnosing means for temporarily detecting an abnormality corresponding to either an abnormality of the catalyst early warm-up control means or deterioration of the catalyst, and detected by the exhaust gas component detection means after completion of the catalyst early warm-up control. Second abnormality diagnosis means for detecting deterioration of the catalyst based on the exhaust gas component to be detected, the result of provisional detection by the first abnormality diagnosis means and the deterioration of the catalyst by the second abnormality diagnosis means. on the basis of the detection result so that diagnoses whether the catalyst early warm-up control means is operating normally. Thereby, the diagnostic accuracy of abnormality of the catalyst early warm-up control means can be improved.
[0009]
Further, as in claim 2 , detection of abnormality of the catalyst early warm-up control means by the first abnormality diagnosis means or provisional detection result of deterioration of the catalyst and detection of deterioration of the catalyst by the second abnormality diagnosis means. It is preferable to discriminate between the abnormality of the catalyst early warm-up control means and the deterioration of the catalyst based on the result. Thereby, it is possible to detect the deterioration of the catalyst in addition to the abnormality of the catalyst early warm-up control means.
[0010]
In this case, as in claim 3 , the exhaust gas component detecting means may be one that detects either the oxygen concentration of the exhaust gas or the air-fuel ratio of the exhaust gas as the exhaust gas component downstream of the catalyst. In this way, oxygen sensors and air-fuel ratio sensors, which are representative sensors installed for air-fuel ratio control, can be used as the exhaust gas component detection means, and the present invention is easily applied.
[0011]
By the way, even if the progress of the warm-up of the catalyst during the early catalyst warm-up control is delayed, after the early catalyst warm-up control is completed, the warm-up of the catalyst has progressed to some extent, so the catalyst must be deteriorated. In this case, the exhaust gas purification rate is high.
[0012]
Therefore, as in claim 4 , the first abnormality diagnosis means temporarily detects an abnormality corresponding to either the abnormality of the catalyst early warm-up control means or the deterioration of the catalyst, and the second abnormality diagnosis means. When the deterioration of the catalyst is detected by the above, it is preferable to finally diagnose the deterioration of the catalyst. In this way, it is possible to prevent the deterioration of the catalyst from being erroneously determined as an abnormality of the catalyst early warm-up control means, thereby improving the reliability of the abnormality diagnosis and also the deterioration of the catalyst. Can be detected.
[0013]
Further, as in claim 5 , the first abnormality diagnosis means temporarily detects an abnormality corresponding to either an abnormality of the catalyst early warm-up control means or a deterioration of the catalyst, and the second abnormality diagnosis means When the deterioration of the catalyst is not detected by the above, it is preferable to finally diagnose the abnormality of the catalyst early warm-up control means. Thereby, the abnormality of the catalyst early warm-up control means can be detected with high accuracy.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings. First, a schematic configuration of the entire engine control system will be described with reference to FIG. An air cleaner 13 is provided at the most upstream portion of the intake pipe 12 of the engine 11 which is an internal combustion engine, and an air flow meter 14 for detecting the intake air amount is provided downstream of the air cleaner 13. A throttle valve 15 and a throttle opening sensor 16 for detecting the throttle opening are provided on the downstream side of the air flow meter 14.
[0015]
Further, a surge tank 17 is provided on the downstream side of the throttle valve 15, and an intake pipe pressure sensor 18 for detecting the intake pipe pressure is provided in the surge tank 17. The surge tank 17 is provided with an intake manifold 19 for introducing air into each cylinder of the engine 11, and a fuel injection valve 20 for injecting fuel is attached in the vicinity of the intake port of the intake manifold 19 of each cylinder. .
[0016]
On the other hand, a catalyst 22 such as a three-way catalyst for reducing CO, HC, NOx and the like in the exhaust gas is installed in the middle of the exhaust pipe 21 of the engine 11. Sensors 23 and 24 (exhaust gas component detection means) for detecting any of gas component concentration such as oxygen concentration of exhaust gas, air-fuel ratio, and rich / lean are installed on the upstream side and downstream side of the catalyst 22, respectively. ing. In the present embodiment, an air-fuel ratio sensor (A / F sensor) that outputs a linear air-fuel ratio signal corresponding to the air-fuel ratio of the exhaust gas is used as the upstream sensor 23, and the downstream sensor 24 is an empty air-fuel ratio sensor. An oxygen sensor whose output voltage is inverted depending on whether the fuel ratio is rich or lean with respect to the stoichiometric air-fuel ratio is used. Further, a water temperature sensor 25 for detecting the coolant temperature and a crank angle sensor 26 for detecting the engine rotation speed are attached to the cylinder block of the engine 11.
[0017]
These various sensor outputs are input to an engine control circuit (hereinafter referred to as “ECU”) 27. The ECU 27 is mainly composed of a microcomputer, and executes air-fuel ratio control routines (not shown) stored in a built-in ROM (storage medium), and performs an upstream air-fuel ratio sensor 23 and a downstream oxygen sensor. Based on the output of the sensor 24, the air-fuel ratio of the exhaust gas is controlled. Specifically, the air-fuel ratio (fuel injection amount) is feedback controlled so that the air-fuel ratio of the exhaust gas upstream of the catalyst 22 matches the target air-fuel ratio based on the output of the upstream air-fuel ratio sensor 23, and further the catalyst The sub-feedback control for correcting the target air-fuel ratio upstream of the catalyst 22 based on the output of the downstream oxygen sensor 24 is performed so that the air-fuel ratio downstream of 22 is matched with the control target value (for example, near the theoretical air-fuel ratio).
[0018]
Further, the ECU 27 performs a catalyst early warm-up control routine shown in FIG. 2 for each predetermined crank angle after an ignition switch (not shown) is turned on, and serves as a catalyst early warm-up control means for performing catalyst early warm-up control. Fulfill. When this routine is started, first, at step 101, it is determined whether or not a catalyst early warm-up control execution condition is satisfied. The conditions for executing the catalyst early warm-up control include, for example, that the catalyst 22 is before warm-up (before activation), and is in an operation state in which ignition timing retarding control can be performed (for example, during idle operation). When all these conditions are satisfied, the catalyst early warm-up control execution condition is satisfied. Whether or not the catalyst 22 has been warmed up is determined by the elapsed time after starting and the coolant temperature, or by determining the intake air amount integrated value or the fuel injection amount integrated value after starting. In short, what is necessary is just to determine whether or not the catalyst 22 is warming up using a parameter related to the total amount of heat applied to the catalyst 22 after startup.
[0019]
When the catalyst early warm-up control execution condition is satisfied, the routine proceeds to step 102 where ignition timing retard control is executed to increase the amount of exhaust heat and promote the warm-up of the catalyst 22. Thereafter, when the conditions for executing the catalyst early warm-up control are no longer satisfied, the routine proceeds to step 103, where the catalyst early warm-up control is terminated and the routine proceeds to normal ignition timing control.
[0020]
Further, the ECU 27 executes the abnormality diagnosis routines shown in FIGS. 3 and 4 stored in the ROM, and diagnoses whether there is an abnormality in the early catalyst warm-up control and whether the catalyst 22 has deteriorated.
[0021]
Here, the diagnosis method will be schematically described. During the early catalyst warm-up control, the purification rate of the exhaust gas that passes through the catalyst 22 changes according to the progress (activity) of the catalyst 22 warm-up. The air-fuel ratio of the exhaust gas flowing around the downstream oxygen sensor 24 changes, and the output of the downstream oxygen sensor 24 changes accordingly. From this relationship, during the early catalyst warm-up control, it is possible to determine whether the warm-up progress of the catalyst 22 is normal or delayed based on the output of the downstream oxygen sensor 24 (see FIG. 5). ) If it is determined that the warm-up of the catalyst 22 is delayed, it is diagnosed as an abnormality in the early catalyst warm-up control.
[0022]
By the way, since the purification characteristics of the catalyst 22 deteriorate as the service period becomes longer, the catalyst 22 is deteriorated even if the warming-up progress of the catalyst 22 during the early catalyst warm-up control is normal. The purification rate of the exhaust gas passing through the catalyst 22 becomes lower than usual. For this reason, when the catalyst 22 is deteriorated and when the warm-up of the catalyst 22 is delayed, the behavior of the exhaust gas purification rate during the early catalyst warm-up control (the behavior of the output of the downstream oxygen sensor 24). Are similar, and it becomes difficult to distinguish between them only from the output of the downstream oxygen sensor 24 during the early catalyst warm-up control.
[0023]
Therefore, in this embodiment, when the warming up of the catalyst 22 has progressed to some extent during the early catalyst warm-up control, the progress of warming up (activation) of the catalyst 22 is determined using the output of the downstream oxygen sensor 24. An abnormality diagnosis is performed as to whether or not there is a delay (hereinafter, this abnormality diagnosis is referred to as “pre-warm-up abnormality diagnosis”). Further, after the catalyst early warm-up control is completed, the catalyst 22 At the time when it can be determined that the warm-up is completed, an abnormality diagnosis is performed again using the output of the downstream oxygen sensor 24 (hereinafter, this abnormality diagnosis is referred to as “abnormal diagnosis after warm-up”). Based on the result of the after-machine abnormality diagnosis, the abnormality of the early catalyst warm-up control and the deterioration of the catalyst 22 are discriminated.
[0024]
That is, even if the progress of the warm-up of the catalyst 22 during the early catalyst warm-up control is delayed, after the early catalyst warm-up control is completed, the warm-up of the catalyst 22 has progressed to some extent until then, so the catalyst 22 is deteriorated. If not, the exhaust gas purification rate is high. Therefore, when it is diagnosed that there is an abnormality in the abnormality diagnosis before warm-up, the deterioration of the catalyst 22 and the abnormality in the early catalyst warm-up control are determined by whether or not the abnormality diagnosis is again performed in the abnormality diagnosis after warm-up. Can be determined.
[0025]
The abnormality diagnosis routine shown in FIG. 3 for executing the abnormality diagnosis described above is started every predetermined time (for example, every 50 msec) after the ignition switch (not shown) is turned on, and serves as an abnormality diagnosis means in the claims. Fulfill. When this routine is started, first, at step 201, it is determined whether or not the pre-warmup abnormality diagnosis has been completed. If the pre-warmup abnormality diagnosis has not been completed, the routine proceeds to step 202, where the warm-up process of FIG. A pre-abnormality diagnosis routine is executed to determine abnormality / normality. When it is determined that the abnormality is detected in this pre-warm-up abnormality diagnosis, it means that either the catalyst early warm-up control abnormality or the catalyst 22 is deteriorated. Note that the pre-warm-up abnormality diagnosis routine of FIG. 4 executed in step 202 serves as the first abnormality diagnosis means in the claims.
[0026]
Then, in the next step 203, it is determined whether or not the abnormality diagnosis after warm-up has been completed. If the abnormality diagnosis after warm-up has not been completed, the process proceeds to step 204, and the abnormality diagnosis routine before warm-up in FIG. After the warm-up abnormality diagnosis routine for performing abnormality diagnosis by the same processing method is executed, abnormality / normality is determined again at a time when it can be determined that the warm-up of the catalyst 22 is completed even when the catalyst early warm-up control is abnormal. If the abnormality diagnosis after warm-up is determined to be abnormal again, it means that the catalyst 22 has deteriorated, and if it is determined to be normal, it means that the catalyst 22 has not deteriorated. The abnormality diagnosis routine after warm-up executed in step 204 serves as a second abnormality diagnosis means in the claims.
[0027]
Thereafter, the process proceeds to step 205, where it is determined whether or not an abnormality is determined in the abnormality diagnosis after warm-up. If the abnormality diagnosis is determined in the abnormality diagnosis after warm-up, the process proceeds to step 207 and the catalyst 22 is deteriorated. If it is determined that there is, a warning lamp (not shown) is turned on to warn the driver, and an abnormal code indicating catalyst deterioration is stored in the backup RAM (not shown) of the ECU 27, and this routine is terminated. .
[0028]
On the other hand, when it is determined that the abnormality is normal (no deterioration of the catalyst 22) in the abnormality diagnosis after warm-up, the process proceeds to step 206, where it is determined whether the abnormality diagnosis before warm-up is determined as abnormal. If it is determined in the pre-machine abnormality diagnosis that there is an abnormality, the process proceeds to step 208, where it is determined that the catalyst early warm-up control is abnormal, and a warning lamp (not shown) is lit to warn the driver. Then, the abnormality code indicating the abnormality of the early catalyst warm-up control is stored in the backup RAM (not shown) of the ECU 27, and this routine is terminated.
[0029]
On the other hand, when it is determined as normal by the abnormality diagnosis before warm-up, it is determined that the early catalyst warm-up control is normally performed and the catalyst 22 is not deteriorated, and this routine is terminated.
[0030]
Next, an abnormality diagnosis method will be described with reference to the time chart of FIG. After the engine 11 is started at time t1, air-fuel ratio feedback control is started at time t2. During the air-fuel ratio feedback control, the air-fuel ratio upstream of the catalyst 22 (the output af of the air-fuel ratio sensor 23) is periodically reversed to rich / lean, so that the exhaust gas purification is performed when the catalyst 22 is unwarmed or deteriorated. When the rate is low, the output sox of the oxygen sensor 24 on the downstream side of the catalyst 22 fluctuates relatively greatly according to the reverse of rich / lean of the air-fuel ratio on the upstream side of the catalyst 22. When the warm-up progresses to some extent and the exhaust gas purification rate increases to some extent, the fluctuation of the output sox of the downstream oxygen sensor 24 becomes small.
[0031]
Therefore, in the present embodiment, when the intake air amount integrated value sg after startup becomes equal to or greater than the predetermined value sga during the catalyst early warm-up control (when the catalyst early warm-up control is normally performed, At a time when it is determined that the fluctuation of the output sox of the downstream oxygen sensor 24 is reduced to a certain extent), the downstream oxygen sensor 24 detects the fluctuation of the air-fuel ratio upstream of the catalyst 22 (the output af of the air-fuel ratio sensor 23). A process for determining the degree of fluctuation of the output sox is started. In this process, the change amount Δsox (see FIG. 6) of the output sox of the downstream oxygen sensor 24 per calculation cycle (for example, 50 msec) is calculated and integrated to calculate the output change amount integrated value of the downstream oxygen sensor 24. While obtaining ΣΔsox, the change amount Δaf of the output af of the upstream air-fuel ratio sensor 23 per calculation cycle (for example, 50 msec) is calculated, integrated, and the output change amount integrated value ΣΔaf of the upstream air-fuel ratio sensor 23 is integrated. Ask. After this integration process is performed until a predetermined time (for example, 30 seconds) elapses, the ratio ΣΔaf / ΣΔsox between the output change integrated value ΣΔaf of the upstream air-fuel ratio sensor 23 and the output change integrated value ΣΔsox of the downstream oxygen sensor 24 Is calculated as an abnormality diagnosis parameter, and abnormality / normality is determined by whether or not the abnormality diagnosis parameter ΣΔaf / ΣΔsox is smaller than a predetermined determination value.
[0032]
Next, the processing contents of the pre-warm-up abnormality diagnosis routine of FIG. When this routine is started, first, in steps 301 and 302, it is determined whether or not the pre-warmup abnormality diagnosis execution condition is satisfied. The pre-warm-up abnormality diagnosis execution conditions are: (1) the intake air amount integrated value sg after the start is equal to or greater than the predetermined value sga [Step 301], and (2) the cooling water temperature detected by the water temperature sensor 25 is the predetermined temperature kthw. (For example, 20 ° C.) [Step 302]. That is, when the intake air amount integrated value sg after the start is less than the predetermined value sga or the cooling water temperature is equal to or lower than the predetermined temperature kthw, the temperature of the catalyst 22 is still low, and normal / abnormal catalyst early warm-up control is not performed. Since it is difficult to distinguish, the pre-warm-up abnormality diagnosis execution condition is not satisfied, and this routine is terminated without performing the subsequent processing.
[0033]
On the other hand, when the intake air amount integrated value sg after the start is equal to or greater than the predetermined value sga and the cooling water temperature exceeds the predetermined temperature kthw, the warm-up control of the catalyst 22 proceeds to some extent and the early catalyst warm-up control is performed. Therefore, the pre-warm-up abnormality diagnosis execution condition is satisfied, and the pre-warm-up abnormality diagnosis process after step 303 is executed as follows. First, in step 303, the previous output af (i-1) is subtracted from the current output af (i) of the upstream air-fuel ratio sensor 23, and the upstream air-fuel ratio sensor 23 per calculation cycle (for example, 50 msec) is subtracted. An output change amount Δaf is obtained. Then, in the next step 304, the previous output sox (i-1) is subtracted from the current output sox (i) of the downstream oxygen sensor 24, and the downstream oxygen sensor 24 per calculation cycle (for example, 50 msec) is subtracted. An output change amount Δsox is obtained.
[0034]
Thereafter, the process proceeds to step 305, where the output change amount Δaf of the upstream air-fuel ratio sensor 23 is integrated to obtain the integrated value ΣΔaf, and in the next step 306, the output change amount Δsox of the downstream oxygen sensor 24 is integrated. The integrated value ΣΔsox is obtained. Thereafter, the process proceeds to step 307, where the intake air amount g detected by the air flow meter 14 is integrated to obtain an intake air amount integrated value sg after starting.
[0035]
Thereafter, the process proceeds to step 308, where it is determined whether or not a predetermined time (for example, 30 sec) has elapsed since the start of the warm-up abnormality diagnosis process, and the above-described integration process is repeated until the predetermined time elapses. Then, when the predetermined time has elapsed, the routine proceeds to step 309, where the output change amount integrated value ΣΔaf of the upstream air-fuel ratio sensor 23 is divided by the output change amount integrated value ΣΔsox of the downstream oxygen sensor 24, and the abnormality diagnosis parameter sp is set. Ask.
sp = ΣΔaf / ΣΔsox
[0036]
Thereafter, the process proceeds to step 310, where the abnormality diagnosis parameter sp is compared with a predetermined determination value. If the abnormality diagnosis parameter sp is smaller than the determination value, the process proceeds to step 311 where it is determined that there is an abnormality and the abnormality diagnosis parameter sp is the determination value. If so, the process proceeds to step 312 and is determined to be normal. At this time, the determination value may be a fixed value for simplification of the arithmetic processing, but may be calculated by a map or the like according to the intake air amount integrated value sg after starting.
[0037]
When it is determined as abnormal in the pre-warm-up abnormality diagnosis routine of FIG. 4 described above, it means that either the catalyst early warm-up control abnormality or the catalyst 22 has deteriorated.
[0038]
The pre-warm-up abnormality diagnosis routine started in step 204 of FIG. 3 is the pre-warm-up abnormality diagnosis of FIG. 4 except that the judgment values are different in steps 301, 302, and 310 of the pre-warm-up abnormality diagnosis routine of FIG. Same as routine. The conditions for executing the abnormality diagnosis after warm-up are: (1) the intake air amount integrated value sg after starting is greater than or equal to a predetermined value that can be determined to end the warm-up of the catalyst 22 even when the catalyst early warm-up control is abnormal; 2) The cooling water temperature detected by the water temperature sensor 25 exceeds a predetermined temperature (for example, 80 ° C.) at which the warming of the catalyst 22 can be determined to end even when the catalyst early warming control is abnormal. When both 1 ▼ and 2) are satisfied, the post-warm-up abnormality diagnosis execution condition is satisfied, and the post-warm-up abnormality diagnosis is executed. If the abnormality diagnosis after the warm-up is determined to be abnormal again, it means that the catalyst 22 has deteriorated. If the abnormality diagnosis after the warm-up is determined to be normal, the catalyst 22 has deteriorated. Means not.
[0039]
In the present embodiment described above, the downstream oxygen sensor 24 is taken into consideration that the output of the oxygen sensor 24 downstream of the catalyst 22 changes in accordance with the progress of warming up of the catalyst 22 during the early catalyst warm-up control. Is used to diagnose whether there is an abnormality in the early catalyst warm-up control, so if an abnormality occurs in the early catalyst warm-up control during engine operation, the abnormality can be immediately detected and It is possible to avoid a situation where a person continues driving without noticing the abnormality at all.
[0040]
In addition, since the downstream oxygen sensor 24 used for the abnormality diagnosis of the catalyst early warm-up control may use a sensor installed for air-fuel ratio control, there is no need to provide a new sensor such as a catalyst temperature sensor. Thus, the abnormality diagnosis of the early catalyst warm-up control can be automatically performed during engine operation while satisfying the demand for cost reduction.
[0041]
Furthermore, in the present embodiment, considering that there is a possibility that the deterioration of the catalyst 22 may be erroneously determined as an abnormality in the catalyst early warm-up control when the catalyst 22 is degraded, the catalyst early warm-up control is performed. After performing abnormality diagnosis (pre-warm-up abnormality diagnosis) using the output of the downstream oxygen sensor 24, after completion of the early catalyst warm-up control, abnormality diagnosis (after warm-up abnormality) is performed again using the output of the downstream oxygen sensor 24. Diagnosis), and when it is diagnosed that there is an abnormality in the abnormality diagnosis before warming up, the deterioration of the catalyst 22 and the abnormality in the early catalyst warm-up control are determined depending on whether or not the abnormality diagnosis after the warming up is diagnosed again. Therefore, it is possible to prevent the deterioration of the catalyst 22 from being erroneously determined as an abnormality in the early catalyst warm-up control, thereby improving the reliability of the abnormality diagnosis and the catalyst. 22 degradation can also be detected.
[0042]
In the present embodiment, only one catalyst 22 is installed in the exhaust pipe 21, but the present invention can also be applied to a configuration in which a plurality of catalysts are installed. In this case, the abnormality diagnosis of the early catalyst warm-up control may be performed using the output of the sensor downstream of the specific catalyst among the plurality of catalysts.
[0043]
Further, the sensor on the downstream side of the catalyst 22 is not limited to the oxygen sensor, and an air-fuel ratio sensor, a gas sensor that detects the gas component concentration such as HC, may be used. Further, the catalyst early warm-up control is not limited to the retard of the ignition timing, and can be implemented by applying the present invention to various known catalyst early warm-up control systems.
[0044]
In this embodiment, the abnormality diagnosis is performed using the output change amount integrated value of the downstream oxygen sensor 24. However, the abnormality diagnosis is performed using the rich / lean inversion cycle of the output of the downstream oxygen sensor 24. Alternatively, the activation timing of the catalyst 22 (warming-up completion timing) is determined using the output of the downstream oxygen sensor 24, and whether or not the activation timing of the catalyst 22 is later than normal is abnormal. The abnormality diagnosis method may be implemented with various changes such as the presence / absence diagnosis.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of an entire engine control system showing an embodiment of the present invention. FIG. 2 is a flowchart showing a process flow of a catalyst early warm-up control routine. FIG. 3 is a process flow of an abnormality diagnosis routine. Flowchart [FIG. 4] Flowchart showing a flow of processing of an abnormality diagnosis routine before warm-up [FIG. 5] Time chart for explaining a processing method of abnormality diagnosis [FIG. 6] Time showing an example of an output waveform of a downstream oxygen sensor Chart [Explanation of symbols]
DESCRIPTION OF SYMBOLS 11 ... Engine (internal combustion engine), 12 ... Intake pipe, 14 ... Air flow meter, 20 ... Fuel injection valve, 21 ... Exhaust pipe, 22 ... Catalyst, 23 ... Upstream air-fuel ratio sensor, 24 ... Downstream oxygen sensor (exhaust gas) Component detection means), 27... ECU (catalyst early warm-up control means, abnormality diagnosis means, first abnormality diagnosis means, second abnormality diagnosis means).

Claims (5)

Exhaust gas purifying catalyst disposed in the exhaust passage of the internal combustion engine, catalyst early warm-up control means for promoting warm-up of the catalyst, and whether the catalyst early warm-up control means is operating normally In an abnormality diagnosis device for an early catalyst warm-up control system for an internal combustion engine, comprising an abnormality diagnosis means for diagnosing
An exhaust gas component detecting means for detecting an exhaust gas component downstream of the catalyst;
The abnormality diagnosis unit is configured to detect an abnormality in the catalyst early warm-up control unit based on an exhaust gas component detected by the exhaust gas component detection unit during the catalyst early warm-up control by the catalyst early warm-up control unit, or First abnormality diagnosis means for tentatively detecting an abnormality corresponding to any of the deteriorations, and deterioration of the catalyst based on exhaust gas components detected by the exhaust gas component detection means after completion of catalyst early warm-up control A second abnormality diagnosing means, and the catalyst early warm-up control means based on the result of provisional detection by the first abnormality diagnosing means and the result of detection of deterioration of the catalyst by the second abnormality diagnosing means. abnormality diagnosis apparatus for fast catalyst warm-up control system of the internal combustion engine you characterized in that diagnoses whether operating normally. The abnormality diagnosing means includes an abnormality of the catalyst early warm-up control means by the first abnormality diagnosing means or a provisional detection result of catalyst deterioration and a result of detection of the catalyst deterioration by the second abnormality diagnosing means. 2. The abnormality diagnosis device for an early catalyst warm-up control system for an internal combustion engine according to claim 1 , wherein an abnormality of the early catalyst warm-up control unit and deterioration of the catalyst are discriminated on the basis of the abnormality. The internal combustion engine according to claim 1 or 2 , wherein the exhaust gas component detection means detects either the oxygen concentration of the exhaust gas or the air-fuel ratio of the exhaust gas as the exhaust gas component downstream of the catalyst. Abnormality diagnosis device for engine early catalyst warm-up control system. The abnormality diagnosis means temporarily detects an abnormality corresponding to either the abnormality of the catalyst early warm-up control means or the deterioration of the catalyst by the first abnormality diagnosis means, and the second abnormality diagnosis means when detecting deterioration of the catalyst, the abnormality diagnosis apparatus for fast catalyst warm-up control system for an internal combustion engine according to claim 1 or 2, characterized in that the diagnosis finally deterioration of the catalyst. The abnormality diagnosis means temporarily detects an abnormality corresponding to either the abnormality of the catalyst early warm-up control means or the deterioration of the catalyst by the first abnormality diagnosis means, and the second abnormality diagnosis means The abnormality diagnosis of the catalyst early warm-up control system for an internal combustion engine according to claim 1 or 2 , wherein when the deterioration of the catalyst is not detected, an abnormality of the catalyst early warm-up control means is finally diagnosed. apparatus.

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