JPH11229860A - Diagnostic device for exhaust emission control device of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the failure diagnosis accuracy of the combustor located upstream of the catalyst of the internal combustion engine. SOLUTION: If the catalyst temperature is greater than the combustor temperature when the combustor temperature and the catalyst temperature are compared while the combustor is in operation, the temperature gradient ΔT1(= catalyst temperature - combustor temperature)is calculated as the temperature gradient resulting from incomplete combustion (S1 through S4). On the other hand, CO, HC, and H2 concentration inside the mixing chamber of exhaust and secondary air are calculated based on the exhaust air fuel ratio and exhaust flow rate and the secondary air flow rate. From this, the temperature increase gradient ΔT2 of the exhaust temperature at complete combustion in the catalyst is calculated. The proportion ΔT1/ΔT2 is defined as proportion UBR not burned in the combustor. When UBR is greater than a predetermined value A, failure indicator lamp is indicated as well as storing it as a quantitative diagnosis result of the degree of abnormality (S9 through S12).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for diagnosing abnormality of a combustor for purifying exhaust gas by burning exhaust gas immediately after the start of an internal combustion engine.

[0002]

2. Description of the Related Art Noble metals (platinum,
Catalysts carrying rhodium or other metals have been used in the past. Such a catalyst purifies by oxidizing and reducing HC, CO, NOx, and the like, which are harmful components in the exhaust gas. By the way, in order to obtain this catalytic action, the exhaust gas temperature must be high. For example, in order to purify HC with a catalyst, a temperature of about 300 ° C. is generally required. Therefore, immediately after the start of the internal combustion engine, the exhaust gas temperature is low,
Because it does not reach the temperature at which the catalyst is activated (around 300 ° C),
There is almost no purification of HC. This results in an increase in the amount of HC released into the atmosphere.

[0003] In order to solve the above-mentioned problem, it is known to dispose a combustor upstream of a catalyst provided in an exhaust system of an internal combustion engine and to activate the combustor immediately after starting to activate the catalyst early by its heat. (Japanese Unexamined Patent Publication No. 5-868)
No. 45, etc.). In such a device, a temperature sensor is installed in the combustor to determine whether the combustion in the combustor has started, and when the temperature detected by the temperature sensor rises when the combustor is operated, the combustion is performed. Has started. Further, a temperature sensor is also provided on the catalyst, and control is performed to stop the operation of the combustor when the catalyst temperature reaches a predetermined temperature.

Here, the combustor does not inject fuel into the combustor, but enriches the air-fuel ratio of the internal combustion engine.
There is also known an apparatus that supplies secondary air and burns a mixture of the rich exhaust and air with an ignition device (Japanese Patent Application Laid-Open No. 6-50 / 1990).
No. 8409, Tokuyohei No. 6-511530). Even in this case, it is easily conceivable to detect the state of combustion from the combustor temperature and control the operation of the combustor.

[0005]

BRIEF Problem to be Solved] In the diagnostic system of the thus constructed exhaust gas purifying apparatus, the combustion component in the exhaust gas supplied to the exhaust of the combustor (CO, HC, H _2, etc.) and 2
Although it is configured so that O _{2 of the} secondary air burns almost completely in the combustor, the combustion becomes unstable due to dirt in the combustor and dirt on the spark plug, etc. It may be supplied to the catalyst without burning. When incomplete combustion occurs in the combustor in this way, the amount of heat required to activate the catalyst is reduced by the heat generated in the combustor immediately after startup, so the catalyst activity is delayed, and again, until the catalyst activity. Takes some time, and if exhaust gas of incomplete combustion flows into the catalyst from the combustor during that time, there is a problem that the exhaust gas is deteriorated because the purification process is not performed by the catalyst. Therefore, it is necessary to quantitatively diagnose the combustion state in the combustor, and it is required to determine that the combustor has failed if the degree of incomplete combustion has increased to some extent.

However, in the above-mentioned conventional diagnostic apparatus, although it is possible to determine whether or not combustion is occurring in the combustor, combustion becomes unstable due to contamination in the combustor and the like.
For abnormal conditions such as incomplete combustion,
The abnormality could not be diagnosed. The present invention has been made in view of such a conventional problem, and has an object to diagnose an abnormal state in which a combustor causes incomplete combustion.

Another object of the present invention is to quantitatively diagnose the degree of abnormality when the abnormal state occurs.

[0008]

Therefore, according to the present invention, as shown in FIG. 1, a combustor for burning exhaust gas is provided in an exhaust passage of an internal combustion engine, and a combustor is provided downstream of the combustor. An exhaust gas purification catalyst, a combustion control device that controls the combustor to burn exhaust gas after the engine is started,
An internal combustion engine including: a combustor temperature detecting means for detecting a temperature of the combustor; a catalyst temperature detecting means for detecting a temperature of the catalyst; and a temperature of the combustor and a temperature of the catalyst in an operating state of the combustor. And when the temperature of the catalyst is higher than the temperature of the combustor, and diagnosing an abnormal combustion state of the combustor based on the temperature difference between the two. It is characterized by having done.

According to the first aspect of the present invention, even when the combustor is performing incomplete combustion during operation of the combustor, the combustion takes place almost completely in the catalyst after the catalyst has been activated to some extent. Utilizing the characteristic that the catalyst temperature rises more than the combustor temperature, the combustor diagnosis means compares the combustor temperature detected by the combustor temperature detection means with the catalyst temperature detected by the catalyst temperature detection means. If the temperature of the catalyst is higher than the temperature of the combustor, it is determined that the combustor may have incomplete combustion, and the incomplete combustion of the combustor is determined based on the temperature difference between the two. Diagnose abnormal conditions according to the degree of combustion.

In the invention according to a second aspect, the combustor diagnostic means estimates an exhaust temperature rise ΔT2 at the time of complete combustion from the air-fuel ratio of exhaust gas in the combustor and the flow rate of exhaust gas passing through the combustor. Comparing the temperature difference ΔT1 between the detected temperature of the combustor and the detected temperature of the catalyst with the estimated exhaust temperature rise allowance ΔT2 at the time of complete combustion, and using the value of ΔT1 / ΔT2 as an incomplete combustion ratio to determine the abnormality of the combustor. It is characterized by quantitatively diagnosing the degree of

According to the second aspect of the present invention, as described above, the supplied combustible component burns almost completely at least in the catalyst after the catalyst has been activated to some extent. As the temperature, it can be considered that the temperature difference between this temperature and the temperature in the combustor is caused by the inability to burn in the combustor. On the other hand, the temperature rise of the exhaust gas when the combustible components are completely burned should be roughly estimated from the concentration of the supplied combustible components, that is, the air-fuel ratio of the exhaust gas in the combustor, and the flow rate of the exhaust gas passing through the combustor. Is possible.

For example, if the exhaust gas containing 1 vol% of CO completely burns CO, the temperature rises by about 100 ° C.
This is determined by the heat of combustion of CO and the heat capacity of the exhaust gas.
When ₁ vol% of H ₂ burns, the temperature of the exhaust gas rises by about 80 ° C. Also, CO, H in the exhaust gas discharged from the engine
The concentrations of C and H ₂ are almost determined by the air-fuel ratio of the engine, and can be determined by experimentally obtaining them in advance. It is supplied to further combustor, since the exhaust is a mixture which has been diluted by the secondary air, based on the flow rate of the exhaust gas flow and the secondary air, the CO, HC, the concentration of H ₂ if the correction can be calculated CO supplied to the combustor, HC, the concentration of H ₂ by the following equation.

COmix = COexh × Qexh / (Q
exh + Qair) HCmix = HCexh × Qexh / (Qexh + Qa
ir) H_Twomix = H_Twoexh × Qexh / (Qexh + Qa
ir) where COmix: exhaust and secondary air supplied to the combustor
COexh: CO concentration in the exhaust gas discharged from the engine
Degree (volume%) HCmix: Mixing of exhaust air supplied to the combustor and secondary air
HC concentration in air (% by volume) HCexh: HC concentration in exhaust gas discharged from the engine
Degree (volume%)  H_Twomix: mixing of exhaust air supplied to the combustor and secondary air
H in the air_TwoConcentration (% by volume)  H_Twoexh: H in exhaust gas discharged from the engine_TwoDark
Degree (volume%)  Qexh: Exhaust flow rate (L / min)  Qair: Secondary air flow rate (L / min)  The exhaust flow rate depends on the engine operating conditions (rotational speed, throttle opening).
Degree). The secondary air flow rate is basically
Set a constant flow rate as it is sufficient to supply a sufficient amount for baking.
It is possible to use this value.
To make the flow variable, install a flow meter and
It is also possible to use fruits. Combustion determined above
CO, HC, H supplied to the vessel_TwoCompletely burned from concentration
The temperature rise of the exhaust gas in the case is calculated and the catalyst temperature
Incomplete combustion in the combustor with the ratio of the temperature difference between the temperature and the combustor temperature
Quantitative diagnosis of the degree of abnormality of the combustor as a percentage
Become.

According to a third aspect of the present invention, the combustor diagnosing means includes a primary diagnosing means and a secondary diagnosing means. It is determined whether or not the catalyst temperature is higher. When the primary diagnosis means determines that the catalyst temperature is higher, the secondary diagnostic means determines whether the operating condition of the internal combustion engine is stable. In this method, the combustor is forcibly operated to quantitatively diagnose the degree of abnormality of the combustor.

According to the third aspect of the present invention, for example, the temperature of the combustor and the catalyst are in a transient state immediately after starting, and it is difficult to perform an accurate quantitative diagnosis in a short time. The primary diagnosis is performed only by comparing the temperature with the catalyst, and a rough determination is made. After that, when the operating condition of the internal combustion engine is stabilized and the temperature condition of the catalyst and the like is stabilized, the combustor is forcibly operated to perform the operation. Perform the following diagnosis and make an accurate quantitative diagnosis.

According to a fourth aspect of the present invention, the secondary diagnostic means completes the temperature difference between the combustor temperature before the forced operation of the combustor and the catalyst temperature after the forced operation for the secondary diagnosis. An exhaust temperature rise allowance ΔT2 during combustion is compared with a temperature difference ΔT1 between the combustor temperature and the catalyst temperature after the forcible operation of the combustor.
The value of T1 / ΔT2 is defined as an incomplete combustion ratio, and the degree of abnormality of the combustor is quantitatively diagnosed.

According to the fourth aspect of the invention, at the time of the secondary diagnosis, the combustor temperature before the forcible operation of the combustor is stored, and the temperature difference from the temperature at which the catalyst temperature becomes stable after the forcible operation is stored. The detected temperature is set as the temperature rise allowance ΔT2 of the exhaust gas at the time of complete combustion. In other words, before the combustor is operated, almost no combustible components are supplied and ignition is not performed, whereas the combustible components supplied after the operation are almost completely burned by at least the catalyst. Is the temperature rise ΔT2 of the exhaust gas. On the other hand, the temperature difference ΔT1 between the combustor temperature and the catalyst temperature after the forcible operation of the combustor can be considered to be caused by the inability to burn in the combustor as described above. Thereby, ΔT1 / Δ
Using the value of T2 as an incomplete combustion ratio, the degree of abnormality of the combustor can be quantitatively diagnosed.

According to this method, CO, H is determined from the air-fuel ratio of the engine.
C, it is not necessary to estimate the concentration of H _2, it is possible to further improve the accuracy of diagnosis. The invention according to claim 5 is characterized in that a predetermined time after the operation of the combustor is included as a condition for starting the secondary diagnosis.

According to the fifth aspect of the present invention, after the combustor is operated, it waits for a predetermined time to elapse before the temperature of the combustor or the catalyst decreases to a certain level from the high temperature state to a stable state. By performing the secondary diagnosis, the accuracy of the secondary diagnosis can be improved. The invention according to claim 6 is characterized in that the operating state of the internal combustion engine when performing the secondary diagnosis is a low-speed low-load condition.

According to the present invention, when the engine is operating in a stable state of low speed and low load such as idling after the activation of the catalyst, the secondary diagnosis is performed by forcibly operating the combustor. it can. Further, in the invention according to claim 7, the exhaust-burning combustor enriches the air-fuel ratio of an internal combustion engine with a combustion vessel installed in the middle of an exhaust passage, a spark plug installed in the combustion vessel, and the like. Means, and means for supplying secondary air to the exhaust passage, and characterized in that the combustor is operated by enriching the air-fuel ratio, supplying secondary air, and performing ignition.

According to the seventh aspect of the present invention, the air-fuel ratio is enriched to increase the combustible component in the exhaust gas supplied to the combustion vessel, and the secondary air is supplied to the combustion vessel via the exhaust passage to remove oxygen. By igniting the air-fuel mixture in the combustion container with an ignition device after replenishment, the combustor can be operated under favorable combustion conditions.

According to an eighth aspect of the present invention, there is provided a combustor for burning the exhaust gas, comprising: a combustion vessel installed in the middle of an exhaust passage; a spark plug installed in the combustion vessel; It comprises a secondary fuel supply means and a means for supplying secondary air to the exhaust passage, and is characterized in that the combustor is operated by performing secondary fuel supply, secondary air supply and ignition.

According to the eighth aspect of the present invention, the secondary fuel is supplied to the combustion vessel, the secondary air is supplied into the combustion vessel through the exhaust passage to supply oxygen, and then the ignition is performed by the ignition plug. By doing so, it is possible to operate the combustor with the air-fuel mixture in the combustion container under favorable combustion conditions.

[0024]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 shows the configuration of the embodiment of the present invention. A combustion vessel 4 is provided on the upstream side of the exhaust gas purification catalyst 3 provided in the exhaust passage 2 of the engine 1, and an ignition plug 5 is provided in the combustion vessel 4.
Further upstream, a secondary air supply passage 7 from a secondary air pump 6 is connected and connected as means for supplying secondary air. The spark plug 5 performs spark discharge by an ignition device 8 including an ignition coil and the like. A combustor temperature sensor 9 as a combustor temperature detecting means is provided at a most downstream portion in the combustion vessel 4, and a catalyst temperature as a catalyst temperature detecting means for detecting an exhaust gas temperature in the catalyst is provided in the catalyst 3. A sensor 10 is provided. This catalyst temperature sensor may be installed immediately downstream of the catalyst 3. The signals of these temperature sensors are sent to the engine control unit (ECU).
11 is input.

The secondary air pump 6 and the ignition device 8 are controlled by an ECU
In response to the signal from 11, the secondary air is supplied and the spark plug 5 is discharged. Further, a fuel injection device 13 is attached to the intake passage 12 of the engine 1,
Fuel is injected according to a signal from U11. Here, as described later, the combustion container 4, the spark plug 5, and the means for enriching the air-fuel ratio by increasing the fuel injection amount by the fuel injection device 13 for exhaust combustion and the secondary air supply means A combustor is constituted by the secondary air pump 6, and the combustor is operated by performing air-fuel ratio enrichment, secondary air supply, and ignition.

The ECU 11 performs a failure diagnosis of a combustor, which will be described later, based on signals from the combustor temperature sensor 9 and the catalyst temperature sensor 10, and when it is determined that a failure has occurred, a failure indicator light ( (Not shown). Here, the operation of the combustor will be described. Immediately after starting, the fuel injection device 13 injects fuel according to a signal from the ECU 11 so that the air-fuel ratio becomes very rich (air-fuel ratio is 10 or less). At the same time, the ECU 11 also activates the secondary air pump 6 and the ignition device 8, so that the supply of the secondary air and the spark discharge of the ignition plug 5 start. The flow rate of the secondary air is set to a flow rate at which the amount of oxygen becomes at least excessive in a state of being mixed with the rich exhaust gas (this varies depending on the exhaust gas amount and the operating state of the engine. There). As a result, combustible components (C
O, HC, and H ₂ ) and O ₂ from the secondary air are supplied in a mixed state, and this starts combustion by the spark of the spark plug 5. The operation of the combustor is stopped when the combustor temperature and the catalyst temperature each reach a predetermined temperature.

Next, failure diagnosis of the combustor according to the first embodiment will be described with reference to the flowchart of FIG. This routine is executed, for example, every second. S1
Then, the operation of the combustor is determined, and if it is operating, the process proceeds to S2. If it is not operating, this routine ends. At S2, the combustor temperature Tcomb and the catalyst temperature Tcat are read.

[0028] In S3, compare Tcomb and Tcat
However, if Tcat is higher, there is a possibility of abnormal combustion.
Therefore, the process proceeds to S4 for further diagnosis. Tcat is Tc
If it is less than or equal to omb, it is determined that there is no abnormality and the processing ends.
You. In S4, the temperature difference ΔT1 between the two is calculated as in the following equation.
I do. ΔT1 = Tcat−Tcomb In S5, an experiment was previously performed based on the set air-fuel ratio A / F of the engine.
Flammable components CO, HC, H in exhaust gas_TwoEach concentration
Degree COexh, HCexh, H_Twoexh from the table
read.

[0029] In S6, the engine speed Ne and the throttle
Read the exhaust flow rate Qexh determined by the opening TVO from the map
Take away. In S7, the above value and the secondary air flow rate Qair are
Using a mixture of exhaust air and secondary air supplied to the combustor
Combustible components CO, HC, H in the state_TwoEach concentration COmi
x, HCmix, H_Twomix is calculated by the following equation.

COmix = COexh × Qexh / (Q
exh + Qair) HCmix = HCexh × Qexh / (Qexh + Qa
ir) H_Twomix = H_Twoexh × Qexh / (Qexh + Qa
ir) where COmix: exhaust and secondary air supplied to the combustor
COexh: CO concentration in the exhaust gas discharged from the engine
Degree (volume%) HCmix: Mixing of exhaust air supplied to the combustor and secondary air
HC concentration in air (% by volume) HCexh: HC concentration in exhaust gas discharged from the engine
Degree (volume%)  H_Twomix: mixing of exhaust air supplied to the combustor and secondary air
H in the air_TwoConcentration (% by volume)  H_Twoexh: H in exhaust gas discharged from the engine_TwoDark
Degree (volume%)  Qexh: Exhaust flow rate (L / min)  Qair: Secondary air flow rate (L / min)  However, the secondary air flow rate Qair is a fixed value.

In S8, the temperature rise allowance at the time of complete combustion ΔT2
Is calculated by the following equation. ΔT2 = COmix × 100 + HCmix × 200 + H
_Twomix × 80 This is the heat of combustion and the heat of exhaust gas as described above.
Approximately determined by capacity, but instead of experimental
There is no problem even if the formula obtained in is used. Next, in S9, combustion
The incomplete combustion ratio UBR in the vessel is determined by the following equation.

UBR = △ T1 / △ T2 In S1O, this UBR is a predetermined value A (for example, 0.2:
Implies that the incomplete combustion ratio is 20%)
In this case, it is determined that the combustor has failed, and the process proceeds to S11.
Turns on the fault indicator to notify the driver of the fault. Sa
Further, in S12, the UBR which is the result of the quantitative diagnosis is
Make a memory and record the degree of failure and
Information. For example, if UBR is not so big
Repair by overhaul etc., UBR is quite large
If it is difficult, you can refer to the need to replace the combustor, etc.
Wear.

If UBR is equal to or less than the predetermined value A in S1O,
The combustor determines that the required performance can be maintained for the time being, and terminates this routine. Here, the predetermined value A varies depending on the configuration, performance, and the like of the entire exhaust system.
It is obtained experimentally when the exhaust system is determined in advance.

With the above operation, even when the combustion state of the combustor becomes unstable and partial combustion occurs partially, the degree of the failure can be quantitatively diagnosed, and the erroneous diagnosis is performed. Can be prevented. Also knowing the extent of the failure, there tends bear the corresponding prospect of repair, a merit that can facilitate repair. Next, a second embodiment of the present invention will be described. This is a failure diagnosis method applied when the operating time of the combustor immediately after startup is short, and performs a simple primary diagnosis and a more detailed secondary diagnosis when it is determined to be NG there. . That is, immediately after the start, the temperatures of the combustor and the catalyst are in a transient state, and it is difficult to perform accurate quantitative diagnosis in a short time. The secondary diagnosis is performed under low-speed and low-load conditions, preferably under steady-state conditions such as idling, thereby enabling accurate quantitative diagnosis.

First, the primary diagnosis will be described with reference to the flowchart of FIG. This routine is executed, for example, every second. In S21, the operation of the combustor is determined. If the combustor is operating, the process proceeds to S22. If it is not operating, this routine ends. Here, the operation of the combustor indicates a normal operation of the combustor from the start, and does not include a forced operation of the combustor for a secondary diagnosis described later.

[0036] In S22, the combustor temperature Tcomb and the catalyst
The temperature Tcat is read. In S23, Tcomb and Tc
At is compared, if Tcat is higher, the abnormal combustion
Judgment that further detailed secondary diagnosis is necessary
Then, the process proceeds to S24, where the secondary diagnosis flag F1 is set to 1. This
F1 is set to 0 at startup together with F2 and F3 described later.
It is set. Tcat is Tcomb in S23
If it is lower, it is determined that there is no abnormality and the process ends.

Next, the secondary diagnosis will be described with reference to FIGS.
The description will be given according to the flowchart. This routine is, for example, 1
Executed every second. In S31, the value of the secondary diagnosis flag F1 is changed.
If the value is 0, secondary diagnosis is not required.
Ends the routine. If it is 1, go to step 32
Proceed to determine whether the secondary diagnosis end flag F3 is 0 or not.
I do. When F3 is 1, the secondary diagnosis is terminated.
Ends this routine, but if it is 0
Goes to S33 to perform secondary diagnosis.

In step 33, it is determined whether a predetermined time (for example, one minute) has elapsed since the operation of the combustor was completed.
This is because the operation of the combustor lowers the temperature of the combustor and the catalyst to a certain extent from a high temperature and waits until the temperature becomes stable. After the predetermined time has passed and the state has been stabilized, the process proceeds to S34, and it is determined whether or not the apparatus is in an idle state.

If it is determined in S34 that the vehicle is in the idle state, the flow proceeds to S35. In S35, the value of the combustor forced operation start flag F2 for secondary diagnosis is determined. F2 = 0
In the case of, since the forcible operation of the combustor has not started, S3
6, the combustor temperature Tcomb before the forcible operation of the combustor
Is detected and stored as Tcomb1. In S37, the forcible operation of the combustor is started. This is similar to the operation of the combustor immediately after the start, in which the air-fuel ratio of the engine is enriched.
The secondary air is supplied to perform spark discharge to the spark plug.

In S38, F2 = 1 is set to indicate that the forced operation of the combustor has started. Next, when this routine is executed, the process proceeds to S39 because F2 = 1 in S35,
Here, it is determined whether a predetermined time has elapsed since F2 = 1. Before the elapse of a predetermined time, the subsequent steps are skipped. Here, the predetermined time is, for example, 10 seconds, which is a time until the temperatures of the combustor and the catalyst rise and become stable by the forced operation of the combustor.

If it is determined in S39 that the predetermined time has elapsed, the process proceeds to S40, and ΔT1 is calculated by the following equation. ΔT1 = Tcat−Tcomb This is a temperature difference between the catalyst temperature after the forcible operation and the combustor temperature after the forcible operation, and indicates a temperature difference due to incomplete combustion in the combustor.

In S41, ΔT2 is calculated by the following equation. ΔT2 = Tcat−Tcomb1 This is a comparison between the catalyst temperature after forced operation of the combustor and the combustor temperature before operation, and this temperature difference indicates that the combustible components supplied to the combustor have completely burned. Shows the temperature rise due to

In S42, the incomplete combustion ratio UBR, which is the result of the quantitative diagnosis, is calculated by the following equation. UBR = △ T1 / △ T2 In S43, as in the first embodiment, this UBR is equal to the predetermined value A.
When it is larger than (for example, 0.2), it is determined that the combustor has failed, and the process proceeds to S44, where the failure indicator is turned on to notify the driver of the failure. Further, in S45, this UBR
Is stored in memory, and the degree of failure is recorded as reference information for repair.

In S46, the forced operation of the combustor is stopped, and S
Since the secondary diagnosis has been completed at 47, F3 = 1 is set, and even if this routine is executed next time, the following steps are skipped at S32. If the UBR is equal to or less than the predetermined value A in S43, it is determined that the combustor can maintain the required performance for the time being,
S46 and subsequent steps are executed, and the secondary diagnosis ends.

If it is determined in step S34 that the engine is not idling, the flow proceeds to step S48. If F2 = 1, the flow advances to step S49 to temporarily stop the secondary diagnosis, and the forced operation of the combustor is stopped. In S50, F2 is set to 0 so that the forced operation of the combustor for the secondary diagnosis can be started again. If F2 = 0 in S48, this routine is terminated.

As described above, according to the second embodiment, the secondary diagnosis is executed when the temperature conditions of the engine, the combustor, and the catalyst are stabilized, so that the failure diagnosis of the combustor can be performed more accurately. Can be performed. Further, in the above embodiment, an ignition plug is installed in a combustion vessel provided in the middle of the exhaust passage, and the air-fuel ratio of the engine is enriched, so that the mixture of exhaust gas containing a large amount of combustible components and secondary air However, the present invention can be similarly applied to a combustor that directly injects fuel into a combustion container in an exhaust passage, instead of enriching an air-fuel ratio of an engine to supply a combustible component. It is something. In this case, the combustion vessel,
A combustor is constituted by a secondary fuel supply means and a secondary air supply means for supplying a secondary fuel to the ignition plug and the combustion vessel,
The combustor is operated by performing the secondary fuel supply, the secondary air supply, and the ignition.

[Brief description of the drawings]

FIG. 1 is a block diagram showing the configuration and functions of the present invention.

FIG. 2 is a diagram showing a system configuration according to an embodiment of the present invention.

FIG. 3 is a flowchart showing a diagnostic routine of the combustor according to the first embodiment of the present invention.

FIG. 4 is a flowchart showing a first stage of a primary diagnosis routine of a combustor according to a second embodiment of the present invention.

FIG. 5 is a flowchart showing a first stage of a secondary diagnosis routine.

FIG. 6 is a flowchart showing a second stage of the secondary diagnosis routine.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Internal combustion engine 2 Exhaust passage 3 Catalyst device 4 Combustion container 5 Ignition plug 6 Secondary air pump 7 Secondary air supply passage 8 Ignition device 9 Combustor temperature sensor 10 Catalyst temperature sensor 11 ECU 13 Fuel injection device

Continued on the front page (51) Int.Cl. ⁶ Identification code FI F01N 3/24 ZAB F01N 3/24 ZABL F02D 41/04 305 F02D 41/04 305A (72) Inventor Keiji Okada 2 Takaracho, Kanagawa-ku, Yokohama-shi, Kanagawa-ku Address Nissan Motor Co., Ltd.

Claims (8)

[Claims] 1. A combustion device for burning exhaust gas in an exhaust passage of an internal combustion engine, a catalyst for purifying exhaust gas installed downstream of the combustor, and an exhaust gas burning by the combustor after the engine is started. A combustion control device that controls the temperature of the combustor; a catalyst temperature detection device that detects the temperature of the catalyst; and A combustor that compares the temperature of the combustor with the temperature of the catalyst and, when the temperature of the catalyst is higher than the temperature of the combustor, diagnoses an abnormal combustion state of the combustor based on the temperature difference between the two. A diagnostic device for an exhaust gas purification device for an internal combustion engine, comprising: diagnostic means. 2. The combustor diagnostic means estimates an exhaust gas temperature rise ΔT2 at the time of complete combustion from the air-fuel ratio of exhaust gas in the combustor and the flow rate of exhaust gas passing through the combustor. The temperature difference ΔT1 between the detected temperatures of the catalyst is compared with the estimated exhaust gas temperature rise ΔT2 at the time of complete combustion, and ΔT1 /
2. The diagnostic apparatus for an exhaust gas purifying apparatus for an internal combustion engine according to claim 1, wherein the degree of abnormality of the combustor is quantitatively diagnosed by using the value of ΔT2 as an incomplete combustion ratio. 3. The combustor diagnosis means comprises a primary diagnosis means and a second diagnosis means.
And a primary diagnostic unit, wherein the primary diagnostic unit determines whether a catalyst temperature is higher than a combustor temperature in a combustion operation state, and the secondary diagnostic unit is configured by the primary diagnostic unit. When it is determined that the catalyst temperature is higher, the combustor is forcibly operated under the condition that the operation state of the internal combustion engine is stable, and the degree of abnormality of the combustor is quantitatively diagnosed. The diagnostic device for an exhaust gas purification device for an internal combustion engine according to claim 1 or 2. 4. The secondary diagnostic means determines the temperature difference between the combustor temperature before the forcible operation of the combustor and the catalyst temperature after the forcible operation for the secondary diagnosis by an exhaust gas temperature rise ΔT2 during complete combustion. This is compared with the temperature difference ΔT1 between the combustor temperature after the forced operation of the combustor and the catalyst temperature after the forced operation, and the value of ΔT1 / ΔT2 is used as an incomplete combustion ratio to quantitatively diagnose the degree of abnormality of the combustor. The diagnostic device for an exhaust gas purifying apparatus for an internal combustion engine according to claim 3, wherein: 5. The exhaust gas purification of an internal combustion engine according to claim 3, wherein a condition that a predetermined time has elapsed after operation of the combustor is included as a condition for starting the secondary diagnosis. Device diagnostic device. 6. The exhaust gas of an internal combustion engine according to claim 3, wherein the operating state of the internal combustion engine when the secondary diagnosis is performed is a low speed and low load condition. Diagnostic device for purification equipment. 7. A combustor for exhaust combustion includes a combustion vessel installed in the middle of an exhaust passage, a spark plug installed in the combustion vessel, means for enriching the air-fuel ratio of the internal combustion engine, 7. A method according to claim 1, further comprising means for supplying secondary air, wherein the combustor is operated by enriching the air-fuel ratio, supplying secondary air, and performing ignition. A diagnostic device for an exhaust purification device of an internal combustion engine. 8. A combustor for burning the exhaust gas includes a combustion vessel provided in the middle of an exhaust passage, a spark plug provided in the combustion vessel, secondary fuel supply means for supplying fuel to the combustion vessel, and an exhaust passage. Means for supplying secondary air to the
The diagnostic device for an exhaust gas purification device for an internal combustion engine according to any one of claims 1 to 6, wherein the combustor is operated by performing secondary fuel supply, secondary air supply, and ignition.