JP3622597B2 - Exhaust gas purification device for internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an exhaust purification technology for an internal combustion engine mounted on an automobile or the like, and more particularly to a technology for detecting deterioration of an exhaust purification catalyst provided in an exhaust system of the internal combustion engine.
[0002]
[Prior art]
In an internal combustion engine mounted on an automobile or the like, an exhaust purification catalyst is provided in the middle of the exhaust passage for the purpose of purifying harmful gas components in the exhaust. As such an exhaust purification catalyst, for example, a three-way catalyst configured by coating alumina on the surface of a ceramic carrier and supporting a platinum-rhodium-based or palladium-rhodium-based noble metal catalyst substance on the alumina surface, etc. Are known.
[0003]
The three-way catalyst causes hydrocarbon (HC) and carbon monoxide (CO) contained in the exhaust to react with oxygen (O ₂ ) in the exhaust when the air-fuel ratio of the inflowing exhaust is near the stoichiometric air-fuel ratio. In addition to oxidizing to water (H ₂ O) and carbon dioxide (CO ₂ ), nitrogen oxide (NO _x ) contained in the exhaust gas is reacted with hydrocarbon (HC) and carbon monoxide (CO) in the exhaust gas. To water (H ₂ O), carbon dioxide (CO ₂ ), and nitrogen (N ₂ ).
[0004]
According to such a three-way catalyst, it becomes possible to purify hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NO _x ) contained in the exhaust, and those harmful gas components are removed from the atmosphere. It is prevented from being released inside.
[0005]
By the way, in the exhaust purification apparatus as described above, it is also important to accurately determine the performance deterioration of the three-way catalyst. Conventionally, a “catalyst deterioration determination device” as described in Japanese Patent Application Laid-Open No. 8-270438 is known in response to such a requirement.
[0006]
The catalyst deterioration determination device described in the above publication measures the actual temperature of the catalyst based on the temperature of the exhaust gas exhausted from the catalytic converter (catalyst output gas temperature), and the engine operating state and the external environment of the catalytic converter. Is used to estimate the catalyst temperature when the degree of deterioration of the catalytic converter is a predetermined degree, and to compare the measured catalyst temperature with the estimated catalyst temperature to determine the degree of deterioration of the catalytic converter. . That is, the catalyst deterioration determination device described in the above publication measures the amount of reaction heat generated in the catalytic converter using the catalyst output gas temperature as a parameter, and tries to determine the deterioration degree of the catalytic converter from the measured heat amount. To do.
[0007]
[Problems to be solved by the invention]
In the catalyst deterioration determination device described above, it is preferable to determine the deterioration of the catalyst when the operation state of the internal combustion engine and the exhaust gas temperature are stable, particularly when the internal combustion engine is in the idle operation state.
[0008]
By the way, in recent years, since the capacity of the catalytic converter tends to increase, when the flow rate of the exhaust gas is low, such as when the internal combustion engine is in an idle operation state, the reaction heat generated in a part of the catalytic converter is different from the other. It is difficult to transmit to the part, and the temperature of each part may be different in the catalytic converter.
[0009]
Since such a temperature difference in the catalytic converter is difficult to be reflected in the catalyst outlet gas temperature, the amount of heat generated in the catalytic converter must be accurately measured based on the catalyst outlet gas temperature when the internal combustion engine is in an idle operation state. Is difficult, and there is a possibility that the accuracy of the catalyst deterioration determination is lowered.
[0010]
The present invention has been made in view of the above-described problems, and provides a technique capable of accurately determining the temperature distribution inside the exhaust purification catalyst, thereby providing accuracy of deterioration determination regarding the exhaust purification catalyst. The purpose is to contribute to improvement.
[0011]
[Means for Solving the Problems]
In the present invention, the following means are adopted to solve the above-described problems. That is, the catalyst deterioration detection device for an internal combustion engine according to the present invention is
An exhaust purification catalyst provided in the exhaust passage of the internal combustion engine;
An exhaust temperature detecting means provided in an exhaust passage downstream of the exhaust purification catalyst, and detecting a temperature of exhaust flowing through the exhaust passage;
Catalyst deterioration for determining the degree of deterioration of the exhaust purification catalyst based on the detection value of the exhaust gas temperature detecting means when the internal combustion engine shifts to a high rotation operation state after continuing a steady operation at a predetermined speed or less for a certain period. A determination means;
It is characterized by having.
[0012]
In the exhaust purification device configured as described above, the catalyst deterioration determination means is discharged from the exhaust purification catalyst when the internal combustion engine shifts to a high rotation operation state after continuing a steady operation state at a predetermined rotation speed or lower for a certain period. The deterioration of the exhaust purification catalyst is determined based on the temperature of the exhaust gas.
[0013]
Here, when the internal combustion engine shifts to the high rotation operation state after continuing the steady operation state of the predetermined number of revolutions or less, the flow rate of the exhaust gas exhausted from the internal combustion engine increases rapidly, and the flow rate of the exhaust gas increases rapidly. Therefore, the exhaust gas that has accumulated in the exhaust purification catalyst during the steady operation of the internal combustion engine is discharged all at once. In this way, the temperature of the exhaust gas discharged from the exhaust purification catalyst all at once becomes a temperature reflecting the amount of heat of the entire exhaust purification catalyst.
[0014]
Therefore, in the exhaust gas purification apparatus for an internal combustion engine according to the present invention, the catalyst deterioration determination means performs the deterioration determination of the exhaust purification catalyst based on the exhaust temperature reflecting the temperature in the exhaust purification catalyst, and the determination accuracy is high. There is no decline.
[0015]
In the exhaust gas purification apparatus for an internal combustion engine according to the present invention, an idle operation state can be exemplified as a steady operation state at a predetermined rotational speed or less, and an acceleration operation state can be exemplified as a high rotation operation state.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, specific embodiments of an exhaust emission control device for an internal combustion engine according to the present invention will be described with reference to the drawings.
[0017]
FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine to which an exhaust gas purification apparatus for an internal combustion engine according to the present invention is applied and an intake / exhaust system thereof.
The internal combustion engine 1 shown in FIG. 1 is a four-cycle water-cooled gasoline engine having four cylinders 2a. A spark plug 2b is attached to the internal combustion engine 1 so as to face the combustion chamber of each cylinder 2a.
[0018]
An intake branch pipe 3 is connected to the internal combustion engine 1, and each branch pipe of the intake branch pipe 3 communicates with a combustion chamber of each cylinder 2a via an intake port (not shown).
The intake branch pipe 3 is connected to a surge tank 4, and the surge tank 4 is connected to an air cleaner box 6 via an intake pipe 5.
[0019]
The intake pipe 5 is provided with a throttle valve 7 for adjusting the flow rate of intake air flowing through the intake pipe 5 in conjunction with an accelerator pedal (not shown). A throttle position sensor 8 that outputs an electrical signal corresponding to the opening degree of the throttle valve 7 is attached to the throttle valve 7.
[0020]
An air flow meter 9 that outputs an electrical signal corresponding to the mass of the intake air flowing through the intake pipe 5 is attached to a portion of the intake pipe 5 upstream of the throttle valve 7.
[0021]
Fuel injection valves 11a, 11b, 11c, and 11d (hereinafter collectively referred to as fuel injection valves 11) for injecting fuel toward the intake ports of the respective cylinders 2a are attached to the respective branch pipes of the intake branch pipe 3. Yes.
[0022]
Each fuel injection valve 11 communicates with a fuel distribution pipe 10, and the fuel distribution pipe 10 communicates with a fuel pump (not shown). The fuel discharged from the fuel pump is supplied to the fuel distribution pipe 10 and then distributed from the fuel distribution pipe 10 to each fuel injection valve 11.
[0023]
Each fuel injection valve 11 is connected to drive circuits 12 a, 12 b, 12 c, and 12 d (hereinafter collectively referred to as drive circuit 12) via electrical wiring, and a drive current is supplied from the drive circuit 12 to the fuel injection valve 11. When applied, the fuel injection valve 11 is opened to inject fuel.
[0024]
On the other hand, an exhaust branch pipe 13 is connected to the internal combustion engine 1, and each branch pipe of the exhaust branch pipe 13 communicates with a combustion chamber of each cylinder 2a via an exhaust port (not shown). The exhaust branch pipe 13 is connected to an exhaust pipe 14, and the exhaust pipe 14 is connected downstream to a muffler (not shown).
[0025]
An exhaust gas purification catalyst 15 for purifying harmful gas components contained in the exhaust gas flowing through the exhaust pipe 14 is provided in the middle of the exhaust pipe 14. The exhaust purification catalyst 15 includes, for example, a ceramic carrier made of cordierite formed in a lattice shape so as to have a plurality of through holes along the exhaust flow direction, and a catalyst layer coated on the surface of the ceramic carrier. The layer is formed by supporting a platinum-rhodium (Pt-Rh) or palladium-rhodium (Pd-Rh) noble metal catalyst material on the surface of porous alumina (Al ₂ O ₃ ) having a large number of pores. Three-way catalyst.
[0026]
The exhaust purification catalyst 15 configured as described above is activated when the temperature is equal to or higher than a predetermined temperature. When the air-fuel ratio of the exhaust gas flowing into the exhaust purification catalyst 15 is close to a desired air-fuel ratio, hydrocarbons ( HC) and carbon monoxide (CO) are reacted with oxygen O ₂ in the exhaust to oxidize to H ₂ O and CO ₂ , and simultaneously NO _X in the exhaust is reacted with HC and CO in the exhaust to produce H ₂ O. , CO ₂ and N ₂ .
[0027]
An air-fuel ratio sensor 16 that outputs an electrical signal corresponding to the air-fuel ratio of the exhaust gas flowing into the exhaust purification catalyst 15 is provided at a location upstream of the exhaust purification catalyst 15 in the exhaust pipe 14.
[0028]
The air-fuel ratio sensor 16 includes, for example, a solid electrolyte portion obtained by firing zirconia (ZrO ₂ ) into a cylindrical shape, an outer platinum electrode that covers the outer surface of the solid electrolyte portion, and an inner platinum electrode that covers the inner surface of the solid electrolyte portion. When the voltage is applied between the electrodes, the oxygen concentration in the exhaust gas is proportional to the movement of oxygen ions (the concentration of the unburned gas component when richer than the stoichiometric air-fuel ratio). It is a sensor that outputs a value voltage.
[0029]
An exhaust temperature sensor 17 that outputs an electrical signal corresponding to the temperature of the exhaust gas flowing out from the exhaust purification catalyst 15 (hereinafter referred to as catalyst exhaust gas temperature) is provided at a position immediately downstream of the exhaust purification catalyst 15 in the exhaust pipe 14. Is provided.
[0030]
On the other hand, the internal combustion engine 1 includes a timing rotor attached to an end portion of a crankshaft (not shown) and an electromagnetic pickup attached to a cylinder block of the internal combustion engine 1, and the crankshaft has a predetermined angle (for example, 30 A crank position sensor 18 that outputs a pulse signal each time it rotates is attached.
[0031]
The internal combustion engine 1 is provided with a water temperature sensor 19 that outputs an electrical signal corresponding to the temperature of the cooling water flowing in the water jacket formed in the cylinder block and cylinder head of the internal combustion engine 1.
[0032]
The internal combustion engine 1 configured as described above is provided with an electronic control unit (ECU: Electronic Control Unit) 20 for controlling the internal combustion engine 1. Various sensors such as a throttle position sensor 8, an air flow meter 9, an air-fuel ratio sensor 16, an exhaust temperature sensor 17, a crank position sensor 18 and a water temperature sensor 19 are connected to the ECU 20 through electric wiring, and output signals of the sensors are output. It is input to the ECU 20.
[0033]
The ECU 20 is connected to the ignition plug 2b, the drive circuit 12 and the like via electric wiring, and controls the ignition plug 2b, the drive circuit 12 and the like using the output signal values of the various sensors described above as parameters.
[0034]
Here, as shown in FIG. 2, the ECU 20 includes a CPU 22, a ROM 23, a RAM 24, a backup RAM 25, an input port 26, and an output port 27 that are connected to each other by a bidirectional bus 21, and the input port 26. And an A / D converter (A / D) 28 connected to the.
[0035]
The input port 26 receives an output signal of a sensor that outputs a digital signal format signal, such as the crank position sensor 18, and transmits the output signal to the CPU 22 and the RAM 24.
[0036]
The input port 26 outputs an output signal of a sensor that outputs a signal in an analog signal format, such as a throttle position sensor 7, an air flow meter 9, an air-fuel ratio sensor 16, an exhaust gas temperature sensor 17, and a water temperature sensor 19, to an A / D converter 28. And the output signals are transmitted to the CPU 22 and the RAM 24.
[0037]
The output port 27 is connected to the spark plug 2b, the drive circuit 12 and the like through electrical wiring, and transmits a control signal output from the CPU 22 to the spark plug 2b and the drive circuit 12.
[0038]
The ROM 23 is an ignition timing control routine for determining the ignition timing of each spark plug 2b, a fuel injection amount control routine for determining a fuel injection amount to be injected from each fuel injection valve 11, and an air-fuel ratio of the fuel injection amount. Application programs such as an air-fuel ratio feedback control routine for performing feedback control, a fuel injection timing control routine for determining the fuel injection timing of each fuel injection valve 11, and various control maps are stored.
[0039]
The control map includes, for example, an ignition timing control map indicating the relationship between the operating state of the internal combustion engine 1 and the ignition timing, a fuel injection amount control map indicating the relationship between the operating state of the internal combustion engine 1 and the fuel injection amount, and the internal combustion engine 1. The fuel injection timing control map showing the relationship between the operating state of the engine and the fuel injection timing, the temperature of the cooling water at the start of the internal combustion engine 1 and the time required from the start to the activation of the exhaust purification catalyst 15 (hereinafter referred to as catalyst activation time) An activity determination control map showing the relationship between
[0040]
The RAM 24 stores output signals from the sensors, calculation results of the CPU 22, and the like. The calculation result is, for example, the engine speed calculated from the output signal of the crank position sensor 18. These data are rewritten to the latest data every time the crank position sensor 18 outputs a signal.
[0041]
The backup RAM 25 is a nonvolatile memory that can store data even after the internal combustion engine 1 is stopped.
The CPU 22 operates according to an application program stored in the ROM 23. At that time, the CPU 22 determines the operating state of the internal combustion engine 1 from the output signals of the respective sensors stored in the RAM 24, and executes various controls such as ignition control and fuel injection control from the operating state and each control map. At the same time, the deterioration determination control (catalyst deterioration determination control) of the exhaust purification catalyst 15 which is the gist of the present invention is executed.
[0042]
In the catalyst deterioration determination control, the CPU 22 determines the deterioration degree of the exhaust purification catalyst 15 based on the output signal value (catalyst output gas temperature) of the exhaust temperature sensor 17 attached to the exhaust pipe 14 downstream from the exhaust purification catalyst 15. .
[0043]
The catalyst deterioration determination control is preferably executed when the temperature of the exhaust gas discharged from the internal combustion engine 1 is stable, for example, when the internal combustion engine 1 is in an idle operation state. However, when the internal combustion engine 1 is in an idle operation state, the temperature of each part in the exhaust purification catalyst 15 may be different, and such a temperature difference in the exhaust purification catalyst 15 is difficult to be reflected in the catalyst exhaust gas temperature. Therefore, it is necessary to detect the catalyst output gas temperature in which the temperature difference in the exhaust purification catalyst 15 is reflected.
[0044]
Here, FIG. 3 shows an example of the temperature distribution in the exhaust purification catalyst 15 when the internal combustion engine 1 is in the idle operation state. In the example shown in FIG. 3, when the internal combustion engine 1 is in an idle operation state when the exhaust purification catalyst is in a new state, the temperature of the exhaust gas exhausted from the internal combustion engine is lowered. Although exposed to low-temperature exhaust, the temperature becomes relatively low, but the reaction between the harmful gas component and the catalytic material becomes active in the region from the middle part to the outlet part, and the amount of heat of reaction increases accordingly. The temperature is high.
[0045]
On the other hand, when the exhaust purification catalyst is in a deteriorated state, the temperature of the inlet portion in the exhaust purification catalyst is relatively low as in the case of a new product, but in the middle portion, harmful gas components and catalyst substances are present. Reaction is slowed down and the amount of reaction heat generated is reduced accordingly, so the temperature is significantly lower than that of a new exhaust purification catalyst.
[0046]
As described above, since the amount of reaction heat generated in the exhaust purification catalyst differs between the new exhaust purification catalyst and the deteriorated exhaust purification catalyst, the amount of reaction heat generated in the exhaust purification catalyst is detected. It becomes possible to determine the degree of deterioration of the exhaust purification catalyst.
[0047]
By the way, when the flow rate of the exhaust gas is low as in the case where the internal combustion engine 1 is in the idling operation state, the catalyst outgas temperature easily reflects the temperature of the outlet portion in the exhaust purification catalyst 15 and the entire exhaust purification catalyst. It is difficult to reflect the amount of heat of the exhaust purification catalyst 1 simply by detecting the catalyst exhaust gas temperature when the internal combustion engine 1 is in the idle operation state.
[0048]
Therefore, in the catalyst deterioration determination control in the present embodiment, the CPU 22 performs the deterioration determination process based on the catalyst exhaust gas temperature when the internal combustion engine 1 shifts to the acceleration operation after being idled for a predetermined time or more. .
[0049]
This is because when the internal combustion engine 1 shifts from the idle operation state to the acceleration operation state, the flow rate of the exhaust gas discharged from the internal combustion engine 1 increases rapidly, and the flow rate of the exhaust gas passing through the exhaust purification catalyst 15 increases rapidly. Since the exhaust gas staying in the exhaust purification catalyst 15 when the internal combustion engine 1 is in the idle operation state is exhausted from the exhaust purification catalyst 15 at the same time, the catalyst exhaust gas temperature at that time is the exhaust purification catalyst 15. This is because the temperature reflects the total amount of heat.
[0050]
For example, when the internal combustion engine 1 is idling, the temperature of the exhaust gas discharged from the internal combustion engine 1 is relatively low, and accordingly, the temperature of the exhaust gas staying in the exhaust purification catalyst 15 is also relatively low. When the internal combustion engine 1 shifts from the idle operation state to the acceleration operation state and the exhaust gas staying in the exhaust purification catalyst 15 is exhausted all at once, the catalyst exhaust gas temperature is once lowered.
[0051]
At this time, if the exhaust purification catalyst 15 is not deteriorated, the exhaust gas staying in the exhaust purification catalyst 15 is heated by the reaction heat generated in the exhaust purification catalyst 15, so that it stays in the exhaust purification catalyst 15. The exhaust gas temperature of the catalyst when exhausted exhaust gases are exhausted all at once is not so lowered.
[0052]
On the other hand, if the exhaust purification catalyst 15 is deteriorated, the amount of reaction heat generated in the exhaust purification catalyst 15 is reduced, and the exhaust gas staying in the exhaust purification catalyst 15 is not heated so much. The exhaust gas temperature when the exhaust gas staying in the catalyst 15 is exhausted all at once is greatly reduced.
[0053]
As a result, it can be said that the catalyst outgas temperature when the internal combustion engine 1 shifts to the acceleration operation state after the idling operation for a predetermined time or longer reflects the heat amount of the entire exhaust purification catalyst 15.
[0054]
Hereinafter, the catalyst deterioration determination control in the present embodiment will be specifically described.
In executing the deterioration determination control of the exhaust purification catalyst 15, the CPU 22 executes a catalyst deterioration determination control routine as shown in FIG.
[0055]
The catalyst deterioration determination control routine is a routine stored in the ROM 23 in advance, and is a routine that is repeatedly executed every predetermined time (for example, every time the crank position sensor 18 outputs a pulse signal).
[0056]
In the catalyst deterioration determination control routine, the CPU 22 first determines in step 401 whether a deterioration determination condition is satisfied. Examples of the deterioration determination condition include conditions such as warming up of the internal combustion engine 1 and the exhaust purification catalyst 15 being in an active state.
[0057]
When it is determined in step 401 that the deterioration determination condition is not satisfied, the CPU 22 sets a counter value of Cidl: “0” for counting the time during which the internal combustion engine 1 is in the idling operation state in step 408. To "" and the execution of this routine is once terminated.
[0058]
On the other hand, if it is determined in step 401 that the deterioration determination condition is satisfied, the CPU 22 proceeds to step 402 and determines whether or not the operating state of the internal combustion engine 1 is in an idle operating state.
[0059]
When it is determined in step 402 that the internal combustion engine 1 is in the idling state, the CPU 22 proceeds to step 403 and updates the counter value of counter: Cidl. When the CPU 22 finishes executing the process of step 403, it temporarily ends the execution of this routine.
[0060]
If it is determined in step 402 that the operation state of the internal combustion engine 1 is not in the idle operation state, the CPU 22 proceeds to step 404 and determines whether or not the internal combustion engine 1 is in the acceleration operation state.
[0061]
If it is determined in step 404 that the internal combustion engine 1 is not in the acceleration operation state, that is, if it is determined that the internal combustion engine 1 is not in the idle operation state and is not in the acceleration operation state, the CPU 22 determines in step 408. Counter: The counter value of Cidl is reset to “0” and the execution of this routine is once ended.
[0062]
When it is determined in step 404 that the internal combustion engine 1 is in the acceleration operation state, the CPU 22 proceeds to step 405 and determines whether or not the counter value of the counter: Cidl exceeds a predetermined time: C, that is, the internal combustion engine 1. Determines whether or not the state has shifted to the acceleration operation state after continuing the idle operation state for a predetermined time: C or more. The predetermined time C is a time sufficient for the temperature difference in the exhaust purification catalyst 15 to be generated due to the internal combustion engine 1 continuing the idle operation state.
[0063]
If it is determined in step 405 that the time measured by the counter: Cidl is equal to or less than the predetermined time: C, the CPU 22 resets the counter value of the counter: Cidl to “0” in step 408 and temporarily executes this routine. finish.
[0064]
If it is determined in step 405 that the time measured by the counter: Cidl exceeds the predetermined time: C, the CPU 22 proceeds to step 406 and inputs the output signal value (catalyst output gas temperature) of the exhaust temperature sensor 17. .
[0065]
In step 407, the CPU 22 executes a catalyst deterioration determination process based on the catalyst output gas temperature input in step 406. That is, the CPU 22 determines the degree of deterioration of the exhaust purification catalyst 15 using the catalyst exhaust gas temperature immediately after the internal combustion engine 1 shifts from the idle operation state to the acceleration operation state as a parameter.
[0066]
Here, immediately after the internal combustion engine 1 shifts from the idle operation state to the acceleration operation state, all the exhaust gas remaining in the exhaust purification catalyst 15 when the internal combustion engine 1 is in the idle operation state is exhausted all at once. It will be.
[0067]
At that time, the exhaust gas staying in the vicinity of the relatively low temperature portion in the exhaust purification catalyst 15 is discharged at a low temperature, and the exhaust gas staying in the vicinity of the relatively high temperature portion in the exhaust purification catalyst 15 is high temperature. It will be discharged as it is. That is, the amount of heat of the exhaust gas exhausted from the exhaust purification catalyst 15 immediately after the internal combustion engine 1 shifts from the idle operation state to the acceleration operation state reflects the total amount of heat in the exhaust purification catalyst 15.
[0068]
As a result, it is possible to accurately detect the total amount of heat in the exhaust purification catalyst 15 by detecting the temperature of the exhaust gas discharged from the exhaust purification catalyst 15 all at once. For example, when the internal combustion engine 1 shifts to the acceleration operation state after continuing the idle operation state for a predetermined time: C or more and the exhaust purification catalyst 15 has not deteriorated, the internal combustion engine 1 changes from the idle operation state to the acceleration operation state. As shown in FIG. 5, the catalyst outlet gas temperature immediately after the transition temporarily decreases as compared with the catalyst outlet gas temperature during the idling operation, but the degree of reduction does not become excessively high. This is because when the internal combustion engine is in an idle operation state, the reaction between the catalytic substance and the harmful gas component is actively performed in the exhaust purification catalyst 15, and the amount of reaction heat generated at that time is relatively large. it is conceivable that.
[0069]
On the other hand, when the internal combustion engine 1 has been in the idle operation state for a predetermined time: C or more and then shifted to the acceleration operation state, if the exhaust purification catalyst 15 has deteriorated, the internal combustion engine 1 is accelerated from the idle operation state. The catalyst output gas temperature immediately after the transition to the state once decreases as compared with the catalyst output gas temperature during the idling operation, and the degree of the decrease becomes excessively large. This is presumably because when the internal combustion engine 1 is in the idling operation state, the reaction between the catalytic substance and the harmful gas component becomes slow in the exhaust purification catalyst 15, and the amount of reaction heat generated accordingly decreases.
[0070]
Here, returning to the catalyst deterioration determination control routine of FIG. 4, when the CPU 22 finishes executing the catalyst deterioration determination process in S407, the CPU 22 proceeds to step 408 and resets the counter value of the counter: Cidl to “0”. When the CPU 22 finishes executing the processing of step 408, the execution of this routine is once ended.
[0071]
Thus, when the CPU 22 executes the catalyst deterioration determination control routine, the catalyst deterioration determination means according to the present invention is realized.
Therefore, according to the exhaust gas purification apparatus for an internal combustion engine according to the present embodiment, the exhaust gas purification is performed based on the catalyst exhaust gas temperature when the internal combustion engine 1 shifts to the acceleration operation state after continuing the idle operation state for a predetermined time or more. By performing the deterioration determination of the catalyst 15, it becomes possible to perform the deterioration determination based on the catalyst exhaust gas temperature reflecting the temperature distribution in the exhaust purification catalyst 15 when the internal combustion engine 1 is in the idling operation state. Can be improved.
[0072]
【The invention's effect】
In the exhaust gas purification apparatus for an internal combustion engine according to the present invention, the exhaust gas purification is performed using the detected value of the exhaust gas temperature detection means as a parameter when the internal combustion engine shifts to a high rotation operation state after continuing a steady operation at a predetermined speed or less for a certain period. Since the degree of deterioration of the catalyst is determined, it is possible to perform highly accurate deterioration determination based on the detection value reflecting the temperature distribution in the exhaust purification catalyst.
[Brief description of the drawings]
FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine to which an exhaust emission control device according to the present invention is applied. FIG. 2 is a block diagram showing an internal configuration of an ECU. FIG. 3 is a diagram showing a temperature distribution inside an exhaust purification catalyst. 4 is a diagram showing a catalyst deterioration determination control routine. FIG. 5 is a diagram showing a mode of catalyst output gas temperature when the internal combustion engine is shifted from an idle operation state to an acceleration operation state.
DESCRIPTION OF SYMBOLS 1 ...... Internal combustion engine 2a ... Cylinder 2b ... Spark plug 13 ... Exhaust branch pipe 14 ... Exhaust pipe 15 ... Exhaust purification catalyst 16 ... Air-fuel ratio sensor 17 ... Exhaust gas Temperature sensor 18 ... Crank position sensor 19 ... Water temperature sensor 20 ... ECU
22 ... CPU

Claims (2)

An exhaust purification catalyst provided in the exhaust passage of the internal combustion engine;
An exhaust temperature detecting means provided in an exhaust passage downstream of the exhaust purification catalyst and detecting a temperature of exhaust flowing through the exhaust passage;
Catalyst deterioration for determining the degree of deterioration of the exhaust purification catalyst based on the detected value of the exhaust gas temperature detecting means when the internal combustion engine shifts to the high rotation operation state after continuing the steady operation at a predetermined speed or less for a certain period. A determination means;
An exhaust emission control device for an internal combustion engine, comprising: The catalyst deterioration determination means determines the degree of deterioration of the exhaust purification catalyst based on the detection value of the exhaust gas temperature detection means when the internal combustion engine shifts to the acceleration operation state after continuing the idle operation state for a certain period. The exhaust emission control device for an internal combustion engine according to claim 1.

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