JP2001123824A - Exhaust gas purification device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To more precisely determine the deterioration of an exhaust emission catalyst by providing technology for accurately determining the temperature distribution in the exhaust emission catalyst. SOLUTION: An exhaust emission control device for an internal combustion engine comprises an exhaust temperature detecting means, provided in an exhaust passage at the downstream side of an exhaust emission catalyst and a catalyst deterioration determining means for determining the degree of deterioration of the exhaust emission catalyst according to a value detected by the exhaust temperature detecting means when the internal combustion engine, after keeping normal operation at a preset rotating speed or lower for a certain period, transits to high rotating speed operation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas purifying technique for an internal combustion engine mounted on an automobile or the like, and more particularly to a technique for detecting deterioration of an exhaust gas purifying catalyst provided in an exhaust system of an internal combustion engine.

[0002]

2. Description of the Related Art In an internal combustion engine mounted on an automobile or the like, an exhaust purification catalyst is provided in the middle of an exhaust passage for the purpose of purifying harmful gas components in exhaust gas. As such an exhaust purification catalyst, for example, a three-way catalyst formed by coating a ceramic carrier surface with alumina and carrying a platinum-rhodium-based or palladium-rhodium-based noble metal catalyst material on the alumina surface is used. Are known.

The three-way catalyst converts hydrocarbons (HC) and carbon monoxide (CO) contained in exhaust gas into oxygen (O ₂ ) in the exhaust gas when the air-fuel ratio of the inflowing exhaust gas is near the stoichiometric air-fuel ratio. With water (H ₂ O) and carbon dioxide (CO
₂ ) Simultaneously with the oxidation to nitrogen oxides (NO _x ) contained in the exhaust gas react with hydrocarbons (HC) and carbon monoxide (CO) in the exhaust gas to produce water (H ₂ O), carbon dioxide (C)
O ₂ ) and nitrogen (N ₂ ).

According to such a three-way catalyst, it is possible to purify hydrocarbons (HC), carbon monoxide (CO) and nitrogen oxides (NO _x ) contained in exhaust gas, and to remove those harmful gases. The components are prevented from being released into the atmosphere.

[0005] In the exhaust gas purification apparatus as described above, it is also important to accurately determine the performance deterioration of the three-way catalyst. To meet such demands, conventionally, Japanese Unexamined Patent Publication No.
A “catalyst deterioration determining device” as described in Japanese Patent No. 70438 is known.

The catalyst deterioration judging device described in the above-mentioned publication measures the actual temperature of the catalyst based on the temperature of the exhaust gas discharged from the catalytic converter (catalyst outgassing temperature), and also determines the operating state of the catalyst and the catalytic converter. Estimate the catalyst temperature when the degree of deterioration of the catalytic converter is about a predetermined degree based on the external environment, and try to determine the degree of deterioration of the catalytic converter by comparing the measured catalyst temperature with the estimated catalyst temperature. Things. 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 outlet gas temperature as a parameter, and attempts to determine the degree of deterioration of the catalytic converter from the measured heat amount. Is what you do.

[0007]

The above-described catalyst deterioration judging device judges the deterioration of the catalyst when the operating state of the internal combustion engine and the temperature of the exhaust gas are stable, particularly when the internal combustion engine is in an idling operation state. It is preferred to do so.

In recent years, since the capacity of the catalytic converter tends to increase, when the exhaust gas flow rate is low, such as when the internal combustion engine is in an idling state, the reaction heat generated in a part of the catalytic converter is reduced. Is difficult to be transmitted to other parts, and the temperature of each part may be different in the catalytic converter.

[0009] Since such a temperature difference in the catalytic converter is hardly reflected on the catalyst output gas temperature, the amount of heat generated in the catalytic converter based on the catalyst output gas temperature when the internal combustion engine is in an idle operation state can be accurately determined. It is difficult to measure, and there is a possibility that the accuracy of catalyst deterioration determination may decrease.

[0010] The present invention has been made in view of the above-mentioned problems, and provides a technique capable of accurately determining the temperature distribution inside the exhaust gas purification catalyst. It is intended to contribute to improvement in the accuracy of the determination.

[0011]

The present invention employs the following means in order to solve the above-mentioned problems. That is, the catalyst deterioration detection device for an internal combustion engine according to the present invention includes an exhaust purification catalyst provided in an exhaust passage of the internal combustion engine and a temperature of exhaust gas provided in an exhaust passage downstream of the exhaust purification catalyst and flowing through the exhaust passage. Exhaust gas detection means for detecting the exhaust gas purification based on the detection value of the exhaust temperature detection 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 predetermined period of time. And a catalyst deterioration determining means for determining the degree of deterioration of the catalyst.

[0012] In the exhaust gas purification apparatus configured as described above,
The catalyst deterioration determination means is configured to determine whether the exhaust gas purification catalyst is to be operated based on the temperature of exhaust gas discharged from the exhaust gas purification catalyst when the internal combustion engine shifts to a high rotation operation state after continuing a steady operation state of a predetermined number of rotations or less for a certain period of time. Deterioration is determined.

Here, when the internal combustion engine shifts to the high rotation operation state after continuing the steady operation state at a predetermined rotation speed or less,
Since the flow rate of the exhaust gas discharged from the internal combustion engine rapidly increases and the flow velocity of the exhaust gas rapidly increases, the exhaust gas remaining in the exhaust purification catalyst during the steady operation of the internal combustion engine is simultaneously discharged. Become. In this way, the temperature of the exhaust gas exhausted from the exhaust purification catalyst at a time is a temperature reflecting the calorific value of the entire exhaust purification catalyst.

Therefore, in the exhaust gas purifying apparatus for an internal combustion engine according to the present invention, the catalyst deterioration judging means judges the deterioration of the exhaust gas purifying catalyst based on the exhaust gas temperature reflecting the temperature inside the exhaust gas purifying catalyst. The judgment accuracy does not decrease.

In the exhaust gas purifying apparatus for an internal combustion engine according to the present invention, an idling operation state can be exemplified as a steady operation state at a predetermined speed or less, and an acceleration operation state can be exemplified as a high rotation operation state. it can.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A specific embodiment of an exhaust gas purifying apparatus for an internal combustion engine according to the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine to which an exhaust gas purifying apparatus for an internal combustion engine according to the present invention is applied and an intake and exhaust system thereof. The internal combustion engine 1 shown in FIG. 1 has four cylinders 2a.
Is a four-cycle water-cooled gasoline engine.
An ignition plug 2b is attached to the internal combustion engine 1 so as to face the combustion chamber of each cylinder 2a.

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.
Is connected to an air cleaner box 6 via an intake pipe 5.

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 electric signal corresponding to the opening of the throttle valve 7 is attached to the throttle valve 7.

In the intake pipe 5, the throttle valve 7
An air flow meter 9 that outputs an electric signal corresponding to the mass of the intake air flowing through the intake pipe 5 is attached to a more upstream portion.

Each branch pipe of the intake branch pipe 3 has a cylinder 2a.
Fuel injection valve 11 for injecting fuel toward the intake port of the vehicle
a, 11b, 11c, and 11d (hereinafter, collectively referred to as fuel injection valves 11) are attached.

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.

Each fuel injection valve 11 is connected to drive circuits 12a, 12b, 12c and 12d (hereinafter collectively referred to as drive circuit 12) via electric wiring.
When a drive current is applied to the fuel injection valve 11 from the fuel injection valve 2, the fuel injection valve 11 opens to inject fuel.

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).

In the middle of the exhaust pipe 14, the exhaust pipe 14
An exhaust gas purifying catalyst 15 for purifying harmful gas components contained in exhaust gas flowing through the inside is provided. The exhaust purification catalyst 15 includes, for example, a ceramic carrier made of cordierite formed in a lattice shape having a plurality of through holes along the exhaust gas flow direction, and a catalyst layer coated on the surface of the ceramic carrier. A layer of platinum-rhodium (Pt-Rh) or palladium-rhodium (Pd) is formed on the surface of porous alumina (Al ₂ O ₃ ) having a large number of pores.
-A three-way catalyst formed by supporting a Rh-based noble metal catalyst substance.

The exhaust purification catalyst 15 thus configured
Is activated when the temperature is equal to or higher than a predetermined temperature, and the exhaust purification catalyst 15
If the air-fuel ratio of the exhaust flowing into the air is near the desired air-fuel ratio,
Hydrocarbon (HC) and carbon monoxide (C) contained in exhaust gas
O) is reacted with oxygen O ₂ in the exhaust gas to oxidize it to H ₂ O and CO ₂ , and simultaneously, NO _X in the exhaust gas is reacted with HC and CO in the exhaust gas to form H ₂ O, CO ₂ and N ₂ . To reduce.

In the exhaust pipe 14, an exhaust purification catalyst 15
An air-fuel ratio sensor 1 that outputs an electric signal corresponding to the air-fuel ratio of the exhaust gas flowing into the exhaust purification catalyst 15
6 are provided.

The air-fuel ratio sensor 16 includes, for example, a solid electrolyte portion obtained by firing zirconia (ZrO ₂ ) in a cylindrical shape, an outer platinum electrode covering the outer surface of the solid electrolyte portion, and an inner platinum electrode covering the inner surface of the solid electrolyte portion. Oxygen concentration in the exhaust gas with the movement of oxygen ions when a voltage is applied between the electrodes and a platinum electrode (unburned gas component concentration when richer than stoichiometric air-fuel ratio) Is a sensor that outputs a voltage having a value proportional to.

In the exhaust pipe 14, an exhaust purification catalyst 15
An exhaust temperature sensor 17 that outputs an electric signal corresponding to the temperature of the exhaust gas flowing out of the exhaust purification catalyst 15 (hereinafter, referred to as catalyst outlet gas temperature) is provided immediately downstream of the exhaust gas purifying catalyst 15.

On the other hand, the internal combustion engine 1 includes a timing rotor attached to an end of a crankshaft (not shown) and an electromagnetic pickup attached to a cylinder block of the internal combustion engine 1. A crank position sensor 18 that outputs a pulse signal each time the motor rotates (for example, 30 degrees) is attached.

The internal combustion engine 1 is provided with a water temperature sensor 19 for outputting an electric signal corresponding to the temperature of cooling water flowing in a water jacket formed in a cylinder block and a cylinder head of the internal combustion engine 1.

The thus configured internal combustion engine 1 includes an electronic control unit (EC) for controlling the internal combustion engine 1.
U: Electronic Control Unit) 20 is also provided. The ECU 20 includes a throttle position sensor 8,
Air flow meter 9, air-fuel ratio sensor 16, exhaust temperature sensor 17, crank position sensor 18, water temperature sensor 1
Various sensors such as 9 are connected via electric wiring, and output signals of the sensors are input to the ECU 20.

The ECU 20 is connected with an ignition plug 2b, a drive circuit 12, and the like via electric wiring, and controls the ignition plug 2b, the drive circuit 12, and the like using output signal values of the various sensors described above as parameters. ing.

Here, as shown in FIG. 2, the ECU 20 includes a CPU connected to each other by a bidirectional bus 21.
22, ROM 23, RAM 24, and backup RAM 2
5, an input port 26 and an output port 27, and an A / D converter (A / D) 28 connected to the input port 26.

The input port 26 receives an output signal of a sensor that outputs a digital signal, such as the crank position sensor 18, and outputs the output signal to the CP.
It is transmitted to U22 and RAM24.

The input port 26 has a throttle position sensor 7, an air flow meter 9, an air-fuel ratio sensor 1
6. The output signal of a sensor that outputs a signal in the form of an analog signal, such as the exhaust gas temperature sensor 17 and the water temperature sensor 19, is A
The signals are input via the / D converter 28 and their output signals are transmitted to the CPU 22 and the RAM 24.

The output port 27 is connected to the ignition plug 2b, the drive circuit 12 and the like via electric wiring, and transmits a control signal output from the CPU 22 to the ignition plug 2b and the drive circuit 12.

The ROM 23 includes an ignition timing control routine for determining the ignition timing of each ignition plug 2b, a fuel injection amount control routine for determining the fuel injection amount to be injected from each fuel injection valve 11, and a fuel injection amount. Application programs such as an air-fuel ratio feedback control routine for performing the air-fuel ratio 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.

The control map includes, for example, an ignition timing control map showing the relationship between the operating state of the internal combustion engine 1 and the ignition timing, a fuel injection amount control map showing the relationship between the operating state of the internal combustion engine 1 and the fuel injection amount, A fuel injection timing control map showing the relationship between the operating state of the internal combustion engine 1 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 An activity determination control map or the like showing the relationship with the catalyst activation time).

The RAM 24 stores an output signal from each sensor, a calculation result of the CPU 22, and the like. The calculation result is, for example, an engine speed calculated from an output signal of the crank position sensor 18. These data are
Each time the crank position sensor 18 outputs a signal,
Rewritten with the latest data.

The backup RAM 25 is a nonvolatile memory capable of storing data even after the operation of the internal combustion engine 1 is stopped. The CPU 22 operates according to an application program stored in the ROM 23. At this time, the CPU 22 determines the operating state of the internal combustion engine 1 from the output signals of the 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, deterioration determination control (catalyst deterioration determination control) of the exhaust gas purification catalyst 15, which is the gist of the present invention.
Execute

In the catalyst deterioration determination control, the CPU 22 determines the degree of deterioration of the exhaust purification catalyst 15 based on the output signal value (catalyst outgas temperature) of the exhaust temperature sensor 17 attached to the exhaust pipe 14 downstream of the exhaust purification catalyst 15. Is determined.

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 idling operation state, the temperature of each part may be different in the exhaust purification catalyst 15, and such an exhaust purification catalyst 1
Since it is difficult for the temperature difference in the exhaust gas 5 to be reflected on the catalyst output gas temperature, it is necessary to detect the catalyst output gas temperature on which the temperature difference in the exhaust purification catalyst 15 is reflected.

FIG. 3 shows an example of the temperature distribution in the exhaust purification catalyst 15 when the internal combustion engine 1 is in the idling operation state.
Shown in In the example illustrated in FIG. 3, when the internal combustion engine 1 is in the idling operation state when the exhaust purification catalyst is in a new state, the temperature of the exhaust gas discharged from the internal combustion engine becomes low. Although exposed to low-temperature exhaust gas, the temperature becomes relatively low.However, the reaction between the harmful gas component and the catalyst material becomes active in the part from the middle part to the outlet part, and the amount of reaction heat increases accordingly, Temperature is high.

On the other hand, when the exhaust gas purification catalyst is in a deteriorated state, the temperature of the inlet portion in the exhaust gas purification catalyst is relatively low as in the case of a new state, but the harmful gas component is in the intermediate portion. The reaction between the catalyst and the catalytic substance becomes slow, and the amount of reaction heat generated accordingly decreases. Therefore, the temperature is significantly lower than that of a new exhaust gas purification catalyst.

As described above, since the amount of reaction heat generated in the exhaust gas purification catalyst differs between the exhaust gas purification catalyst in a new state and the exhaust gas purification catalyst in a deteriorated state, the amount of reaction heat generated in the exhaust gas purification catalyst is detected. This makes it possible to determine the degree of deterioration of the exhaust purification catalyst.

When the flow rate of the exhaust gas is low, such as when the internal combustion engine 1 is in an idling operation state, the temperature of the exhaust gas from the catalyst easily reflects the temperature at the outlet of the exhaust gas purification catalyst 15 and the exhaust gas temperature is low. Since it is difficult to reflect the heat quantity of the entire purification catalyst, it is difficult to grasp the heat quantity of the entire exhaust purification catalyst 1 simply by detecting the catalyst output gas temperature when the internal combustion engine 1 is in an idle operation state.

Therefore, in the catalyst deterioration determination control according to the present embodiment, the CPU 22 performs a deterioration determination process based on the catalyst outlet gas temperature when the internal combustion engine 1 shifts to the acceleration operation after the idle operation for a predetermined time or more. I did it.

When the internal combustion engine 1 shifts from the idling operation state to the acceleration operation state, the flow rate of the exhaust gas discharged from the internal combustion engine 1 sharply increases, and the flow velocity of the exhaust gas passing through the exhaust purification catalyst 15 sharply increases. When the internal combustion engine 1 is in the idling operation state, the exhaust gas that has accumulated in the exhaust gas purification catalyst 15 is exhausted from the exhaust gas purification catalyst 15 all at once. This is because the temperature becomes a value reflecting the calorific value of the entire purification catalyst 15.

For example, when the internal combustion engine 1 is idling, the temperature of the exhaust gas discharged from the internal combustion engine 1 becomes relatively low, and the temperature of the exhaust gas retained in the exhaust purification catalyst 15 accordingly becomes relatively low. Therefore, when the internal combustion engine 1 shifts from the idle operation state to the acceleration operation state and the exhaust gas remaining in the exhaust gas purification catalyst 15 is exhausted at once, the catalyst outlet gas temperature once drops.

At this time, if the exhaust gas purification catalyst 15 is not deteriorated, the exhaust gas remaining in the exhaust gas purification catalyst 15 is heated by the reaction heat generated in the exhaust gas purification catalyst 15. The temperature of the catalyst outgas when the exhaust gas staying inside is exhausted at the same time does not decrease so much.

On the other hand, if the exhaust purification catalyst 15 has deteriorated, the amount of reaction heat generated in the exhaust purification catalyst 15 decreases, and the exhaust gas remaining in the exhaust purification catalyst 15 is not heated much. As a result, the temperature of the exhaust gas from the catalyst when the exhaust gas remaining in the exhaust gas purifying catalyst 15 is exhausted all at once is greatly reduced.

As a result, it can be said that the catalyst outgassing temperature when the internal combustion engine 1 shifts to the acceleration operation state after the idling operation for a predetermined time or more is a temperature reflecting the calorific value of the entire exhaust purification catalyst 15.

Hereinafter, the catalyst deterioration determination control according to the present embodiment will be specifically described. In performing the deterioration determination control of the exhaust purification catalyst 15, the CPU 22 executes a catalyst deterioration determination control routine as shown in FIG.

The catalyst deterioration determination control routine is performed in advance in the ROM
23 is a routine that is repeatedly executed at predetermined time intervals (for example, every time the crank position sensor 18 outputs a pulse signal).

In the catalyst deterioration determination control routine, the CPU 2
2 first determines in step 401 whether the deterioration determination condition is satisfied. Examples of the deterioration determination condition include, for example, a condition that the warm-up of the internal combustion engine 1 is completed, a condition that the exhaust purification catalyst 15 is in an active state, and the like.

If it is determined in step 401 that the deterioration determination condition is not satisfied, the CPU 22 determines in step 408 a counter for measuring the time during which the internal combustion engine 1 is in the idle operation state: the counter value of Cidl. Is reset to "0", and the execution of this routine is temporarily ended.

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 operation state of the internal combustion engine 1 is an idle operation state.

If it is determined in step 402 that the internal combustion engine 1 is in the idling state, the CPU 22
Goes to step 403, and updates the counter value of the counter: Cidl. After completing the process of step 403, the CPU 22 ends the execution of this routine once.

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 to determine whether or not the internal combustion engine 1 is in an accelerating operation state.

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 Step 40
In step 8, the counter value of the counter Cidl is reset to "0", and the execution of this routine is temporarily terminated.

If it is determined in step 404 that the internal combustion engine 1 is in the accelerating operation state, the CPU 22
Proceeding to step 405, it is determined whether or not the counter value of the counter: Cidl exceeds a predetermined time: C, that is, whether or not the internal combustion engine 1 has shifted to the acceleration operation state after continuing the idle operation state for the predetermined time: C or more. Is determined. The above-mentioned predetermined time: C is a time sufficient for a temperature difference in the exhaust purification catalyst 15 to occur due to the continuation of the idling state of the internal combustion engine 1.

At step 405, the counter: C
If it is determined that the measured time of idl 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 ends the execution of this routine once.

At step 405, the counter: C
If it is determined that the measured time of idl exceeds the predetermined time: C, the CPU 22 proceeds to step 406 and inputs the output signal value of the exhaust gas temperature sensor 17 (catalyst output gas temperature).

In step 407, the CPU 22 executes a catalyst deterioration determination process based on the catalyst outlet gas temperature input in step 406. That is, CPU2
2 determines the degree of deterioration of the exhaust gas purification catalyst 15 using the catalyst outlet gas temperature immediately after the internal combustion engine 1 shifts from the idle operation state to the acceleration operation state as a parameter.

Immediately after the internal combustion engine 1 shifts from the idling operation state to the acceleration operation state, all the exhaust gas remaining in the exhaust gas purifying catalyst 15 when the internal combustion engine 1 is in the idling operation state is simultaneously discharged. Will be discharged.

At this time, the exhaust gas that had stayed in the vicinity of the relatively low-temperature portion in the exhaust gas purification catalyst 15 was discharged at a low temperature, and stayed in the vicinity of the relatively high-temperature portion in the exhaust gas purification catalyst 15. The exhaust gas will be discharged at a high temperature. That is, the heat quantity 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 entire heat quantity in the exhaust purification catalyst 15.

As a result, by detecting the temperature of the exhaust gas exhausted from the exhaust purification catalyst 15 all at once, the total amount of heat in the exhaust purification catalyst 15 can be accurately detected. For example, when the internal combustion engine 1 shifts to the acceleration operation state after continuing the idle operation state for the predetermined time: C or more, if 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 shift temporarily decreases as compared with the catalyst outlet gas temperature during the idling operation, but the degree of the drop does not become excessively large. This is because when the internal combustion engine is in an idling operation state, the exhaust purification catalyst 1
It is considered that the reaction between the catalytic substance and the harmful gas component is actively performed in 5, and the amount of reaction heat generated at that time is relatively large.

On the other hand, when the internal combustion engine 1 is shifted to the acceleration operation state after continuing the idle operation state for a predetermined time: C or more, if the exhaust purification catalyst 15 is deteriorated, the internal combustion engine 1 is in the idle operation state. Immediately after shifting from the state to the acceleration operation state, the catalyst outgassing temperature temporarily decreases compared to the catalyst outgassing 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 idle operation state, the reaction between the catalytic substance and the harmful gas component in the exhaust purification catalyst 15 becomes slow, and the amount of reaction heat generated accordingly decreases.

Here, returning to the catalyst deterioration determination control routine of FIG. 4, after completing the catalyst deterioration determination processing in S407, the CPU 22 proceeds to step 408 and resets the counter value of the counter: Cidl to “0”. . C
When the PU 22 finishes executing the processing of Step 408,
The execution of this routine ends once.

As described above, 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 purifying apparatus for an internal combustion engine according to the present embodiment, the exhaust gas purification is performed based on the catalyst outlet 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 is possible to perform the deterioration determination based on the catalyst output gas temperature reflecting the temperature distribution in the exhaust purification catalyst 15 when the internal combustion engine 1 is in the idling operation state, and the determination accuracy is improved. Can be improved.

[0072]

In the exhaust gas purifying apparatus for an internal combustion engine according to the present invention, the detected value of the exhaust gas temperature detecting means when the internal combustion engine shifts to a high-speed operation state after continuing a steady operation at a predetermined speed or less for a certain period of time. Is used as a parameter to determine the degree of deterioration of the exhaust purification catalyst, so that it is possible to perform highly accurate deterioration determination based on a 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 gas purification 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.

FIG. 4 is a diagram showing a catalyst deterioration determination control routine.

FIG. 5 is a diagram showing an aspect of a catalyst outlet gas temperature when the internal combustion engine shifts from an idling operation state to an acceleration operation state.

[Explanation of symbols]

 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 Temperature sensor 18 Crank position sensor 19 Water temperature sensor 20 ECU 22 CPU

Continued on front page F-term (reference) 3G084 CA04 CA09 DA27 EB12 EC01 FA07 FA10 FA20 FA27 FA29 FA33 FA38 3G091 AA17 AA23 AA28 AB03 BA33 DB10 EA17 EA30 EA34 FA12 FA17 FC04 GA06 GB05W GB06W GB07W GB17X HA36 HA37

Claims (2)

[Claims] An exhaust purification catalyst provided in an exhaust passage of an internal combustion engine; exhaust temperature detection means provided in an exhaust passage downstream of the exhaust purification catalyst to detect a temperature of exhaust flowing through the exhaust passage; 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 predetermined period, a catalyst deterioration determination for determining a degree of deterioration of the exhaust gas purification catalyst based on a detection value of the exhaust gas temperature detection means. Means for purifying exhaust gas of an internal combustion engine. 2. When the internal combustion engine shifts to an acceleration operation state after continuing the idle operation state for a certain period of time, the catalyst deterioration determination means detects the exhaust gas purification catalyst based on a detection value of the exhaust gas temperature detection means. The exhaust gas purifying apparatus for an internal combustion engine according to claim 1, wherein the degree of deterioration is determined.