JPH11200847A - Exhaust gas purification device for internal combustion engine - Google Patents

Abstract

(57) [Problem] To provide an exhaust gas purifying apparatus for an internal combustion engine capable of performing control for removing soot adhering to a catalyst due to rich operation, incomplete ignition, or the like, and suppressing a decrease in catalyst performance. SOLUTION: In an exhaust gas purifying apparatus for an internal combustion engine including a catalyst provided in an exhaust passage of an engine and an exhaust combustor provided upstream of the catalyst, it is determined whether or not the exhaust combustor normally ignites. An ignition determining means a and a catalyst purifying means b for removing soot attached to the catalyst when the ignition determining means a determines that normal ignition has not occurred.

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 apparatus for an internal combustion engine, and more particularly to heating the catalyst using an exhaust combustor installed upstream of the catalyst immediately after starting the internal combustion engine to activate the catalyst early. The present invention relates to an exhaust gas purification device provided with the device.

[0002]

2. Description of the Related Art Catalysts carrying noble metals (platinum, rhodium, etc.) or other metals have been used for exhaust gas purification of automobiles. Such catalysts are cleaned by causing HC are harmful components in the exhaust gas, CO, and NO _X such as oxidation, or reduction. The purification by the catalyst is strongly affected by the catalyst temperature, and is generally 350 to 40.
Requires temperatures above 0 ° C. Immediately after the start of the engine, the exhaust gas temperature is low, and the catalyst is activated (350 to 4).
(00 ° C. or higher), the harmful components are hardly purified. Further, during a cold state immediately after the start of the engine, the amount of HC and CO emissions may increase, and the amount of HC and CO released into the atmosphere may increase. In order to solve such a problem of the conventional exhaust gas purifying apparatus for an internal combustion engine, an exhaust combustor is installed upstream of a catalyst provided in an exhaust passage of the engine, and the catalyst is rapidly heated by the combustion energy. (Japanese Unexamined Patent Publication No. 6-508409) is known. In this system, during the period in which the catalyst is not activated immediately after the start, the air-fuel ratio is made to operate rich and secondary air is supplied into the exhaust passage by an air pump or the like, and the exhaust gas in the exhaust passage is mixed with the combustible air-fuel mixture. As a result, the combustible air-fuel mixture is burned by an ignition plug provided in the exhaust combustor, and the catalyst is rapidly heated by the combustion energy to activate the catalyst quickly.

[0003]

However, in such an exhaust gas purifying apparatus for an internal combustion engine, the air-fuel ratio is made rich and the combustible air-fuel mixture formed by the secondary air is exhausted by the ignition plug of the exhaust combustor. During combustion, if reliable ignition was not performed, there was a problem that soot due to enrichment of the air-fuel ratio and incomplete ignition adhered to the catalyst, possibly deteriorating the performance of the catalyst. . The present invention has been made in view of such a conventional problem, and it is determined whether a combustible mixture formed in an exhaust passage of an internal combustion engine has been securely ignited in an exhaust combustor, and ignition is performed. The object of the present invention is to solve the above problem by performing control for removing soot adhering to the catalyst when it is not performed.

[0004]

In order to solve the above-mentioned problems, in the exhaust gas purifying apparatus for an internal combustion engine according to the present invention, if it is determined that the exhaust combustor has not ignited normally, the soot attached to the catalyst is removed. Means to do this. That is, FIG.
As shown in the claim correspondence diagram, ignition determination means a for determining whether the exhaust combustor normally ignites, and control for removing soot attached to the catalyst when the ignition determination means a outputs that ignition is not normal. And a catalyst purifying means (b) for performing the reaction. In order to solve the above-mentioned problem, in the exhaust gas purifying apparatus for an internal combustion engine according to the second aspect, in the invention according to the first aspect, the ignition determining means a sets the catalyst temperature to a predetermined value after a lapse of a predetermined time from the ignition of the exhaust combustor. If it has not reached, it is a means to determine that normal ignition has not occurred. According to a third aspect of the present invention, there is provided an exhaust gas purifying apparatus for an internal combustion engine, wherein the catalyst purifying means includes a catalyst purifying means that supplies oxygen to the catalyst when the engine is under a high load operation. -A means for removal. In order to solve the above-mentioned problem, in the exhaust gas purifying apparatus for an internal combustion engine according to claim 4,
The catalyst purifying means b according to claim 1 or 2,
Is a means for retarding the ignition timing of the engine and supplying oxygen to the catalyst to burn and remove soot. In order to solve the above-mentioned problem, in the exhaust gas purifying apparatus for an internal combustion engine according to claim 5, in the invention according to claim 3 or 4, the catalyst purifying means b supplies oxygen to the catalyst using an oxygen supplying device of the exhaust combustor. The means to do it. According to a sixth aspect of the present invention, there is provided an exhaust gas purifying apparatus for an internal combustion engine.
In the described invention, the catalyst purifying means b is a means for supplying oxygen to the catalyst by making the air-fuel ratio of the internal combustion engine lean.

[0005]

The operation of the first aspect of the present invention will be described. If it is determined by the ignition determining means a that the exhaust combustor did not normally ignite, control is performed by the catalyst purifying means b to remove soot attached to the catalyst. Therefore, even when the exhaust combustor does not normally ignite and soot adheres to the catalyst, the catalyst purifying means b removes soot from the catalyst, and a reduction in the performance of the catalyst is suppressed. The operation of the second aspect will be described. If the ignition determining means a determines that the exhaust combustor did not normally ignite based on the catalyst temperature after a lapse of a predetermined time from the ignition of the exhaust combustor, the catalyst purifying means b removes soot adhering to the catalyst. Is performed. Claim 3
The operation of the described invention will be described. If it is determined by the ignition determination means a that the exhaust combustor did not normally ignite, control is performed by the catalyst purification means b to supply oxygen to the catalyst and burn and remove soot attached to the catalyst during a high load operation of the internal combustion engine. The operation of the invention will be described. If it is determined by the ignition determining means a that the exhaust combustor did not normally ignite, the catalyst purifying means b controls the ignition timing of the internal combustion engine to be retarded and oxygen is supplied to the catalyst to burn and remove soot that has adhered. Done. The operation of the invention will be described. If it is determined by the ignition determining means a that the exhaust combustor did not normally ignite, the catalyst purifying means b controls the supply of oxygen to the catalyst by the oxygen supply device of the exhaust combustor to burn and remove the adhering soot. The operation of the invention according to claim 6 will be described. If it is determined by the ignition determination means a that the exhaust combustor did not normally ignite,
The catalyst purifying means b controls the air-fuel ratio of the internal combustion engine to be lean to supply oxygen to the catalyst and burn and remove soot adhering thereto.

[0006]

Embodiments of the present invention will be described below with reference to the drawings. First Embodiment First, the configuration will be described. FIG. 2 is a diagram showing a configuration of the first embodiment. A catalyst 6 is provided in the exhaust passage 2 of the internal combustion engine 1. A temperature sensor 7 is attached to the catalyst 6. A combustion chamber 5 and an ignition plug 4 of an exhaust combustor are provided upstream of the catalyst 6, and an air pump 3 for supplying air into the exhaust passage 2 is provided upstream of the combustion chamber 5. The control unit 8 drives the air-fuel ratio of the internal combustion engine 1, the air pump 3, and the ignition plug 4 with reference to the cooling water temperature of the engine 1, the output of the temperature sensor 7, and the like to control the exhaust combustor.

Next, the operation of this embodiment will be described with reference to the flowchart shown in FIG. First, when the ignition switch is on, a flag FSS described later holds the value at the time of the ignition switch off in the previous operation. The flag FEGI is cleared to 0.

[0008] At S1, the cooling water temperature Tw at the time of starting the internal combustion engine 1 is determined.
It is determined whether start is lower than a predetermined value Twegi.
If it is low, it is determined that heating of the catalyst 6 by the exhaust combustor is necessary, and the process proceeds to S2, and it is determined whether the flag FEGI indicating that the use of the exhaust combustor has been completed is 1 or not. FEGI = 1
In the case of, use of the exhaust combustor has been completed, and in S4,
It is determined whether the soot removal operation of the catalyst 6 is necessary. Also, S1
Even if Twstart ≧ Twegi and it is not necessary to heat the catalyst 6 by the exhaust combustor, the process proceeds to S4 to determine whether the soot removal operation of the catalyst 6 by the past operation is necessary.
If the flag FSS = 1 indicating that soot has adhered to the catalyst 6 and the removal operation is necessary in S4, the process proceeds to S4.
A soot removal operation is performed at 10 or later. This will be described later. If the FSS is not 1 in S4, the process ends.

In S2, if FEGI is not 1, S3
To enrich the air-fuel ratio supplied to the internal combustion engine, and drive the air pump 3 and the spark plug 4 to perform combustion in the exhaust combustor. Next, in S5, it is determined whether a predetermined time has elapsed since the start of combustion in the exhaust combustor. If not, the combustion in the exhaust combustor is continued. If it has passed, the catalyst temperature Tcat is increased to a predetermined value Teg in S6.
Determine if i has been reached. If it has reached, the exhaust combustor ignites normally and determines that the catalyst 6 has been sufficiently heated, terminates combustion in the exhaust combustor in S7, and then proceeds to FE in S9.
GI = 1 is set. If Tcat has not reached Tegi in S6, it is determined that the exhaust combustor did not normally ignite and that soot generated by enrichment of the air-fuel ratio or incomplete ignition of the exhaust combustor adhered to the catalyst 6, In S8, FSS = 1 is set, and the process proceeds to S7.

Next, a description will be given of a routine in S4 when FSS = 1 and the soot removal operation of the catalyst 6 is required. S1
At 0, it is determined whether or not the internal combustion engine 1 is currently operating under a high load. This may be determined based on, for example, whether the engine speed is equal to or more than a predetermined value and the basic fuel injection pulse width is equal to or more than a predetermined value. If the operation is not a high-load operation, the catalyst temperature is low and soot is not burned and removed even if oxygen is supplied.
Then, the air pump 3 of the exhaust combustor is turned off, and the process ends. In the case of the high load operation, the air pump 3 is turned on in S11 and oxygen is fed into the high-temperature catalyst 6 to burn and remove soot. In S13, the soot is burned.
It is determined whether the total removal time has reached a predetermined value.
If the value has not reached the predetermined value, the process is terminated as it is, and the burning and removal of soot is continued. On the other hand, if it has reached the predetermined value, it is determined that the soot combustion / removal has been completed, the air pump 3 is turned off in S14, and FSS = 0 is set in S15, and the processing is terminated. Here, the soot combustion / removal is determined by whether or not a predetermined time has elapsed since the air pump 3 was turned on and the supply of oxygen to the catalyst 6 was started, that is, the total time during which the soot was burned / removed. Although it is determined whether the process has been completed, the determination may be made based on whether the catalyst temperature has increased due to soot combustion and has reached a predetermined value.

As described above, in the exhaust gas purifying apparatus for an internal combustion engine according to the first embodiment, the catalyst temperature does not reach a predetermined value after a lapse of a predetermined time from the start of the operation of the exhaust combustor. In this case, it was determined that the exhaust combustor did not normally ignite and soot was attached to the catalyst 6, and oxygen was supplied to the catalyst 6 by the air pump 3 during high-load operation with a high catalyst temperature to burn and remove soot. Therefore, a decrease in the performance of the catalyst 6 is suppressed.

Second Embodiment The configuration of the second embodiment is the same as that of the first embodiment.

Next, the operation of the second embodiment will be described. The second embodiment differs from the first embodiment in the method of burning and removing soot from S10 to S15, and is replaced with S21 to S24. If it is determined in S4 that soot combustion / removal of the catalyst is necessary, in S21, the ignition timing of the combustion chamber of the internal combustion engine (not the ignition plug of the exhaust combustor) is retarded by a predetermined amount to increase the catalyst temperature. At the same time, the air pump 3 is driven,
By supplying oxygen to the catalyst 6, soot is burned and removed. In S22, it is determined whether or not the total time for burning and removing soot has reached a predetermined time. If the value has not reached the predetermined value, the process is terminated as it is, and the burning and removal of soot is continued. On the other hand, if the predetermined time has been reached, it is determined that the soot combustion / removal has been completed, the ignition timing is retarded in S23, and the air pump 3 is turned off.
At 4, the FSS is set to 0, and the processing ends. As in the first embodiment, here, the total time during which the soot is burned and removed,
Although it is determined whether the soot combustion / removal has been completed, it may be determined whether the catalyst temperature has increased due to soot combustion and has reached a predetermined value.

Further, by combining the first and second embodiments, during high load operation, the ignition timing is retarded by a predetermined value, and the catalyst temperature is further increased to perform soot combustion / removal. Conceivable.

As described above, in the exhaust gas purifying apparatus for an internal combustion engine according to the second embodiment, if it is determined that the exhaust combustor has not ignited normally and soot has adhered to the catalyst 6, the ignition timing is immediately adjusted. By delaying the fixed amount and raising the catalyst temperature, and supplying oxygen to the catalyst 6 by the air pump 3,
It is possible to burn and remove soot without waiting for a high load condition, so that the performance of the catalyst 6 is prevented from deteriorating.

Third Embodiment The configuration of the third embodiment is the same as that of the first embodiment.

Next, the operation of the third embodiment will be described. The present embodiment differs from the first and second embodiments only in the method of supplying oxygen for burning and removing soot attached to the catalyst 6, and supplies oxygen by making the air-fuel ratio lean. Therefore, in steps S10 to S15 of the first embodiment and in steps S21 to S24 of the second embodiment, in steps S11 and S21 in which the air pump 3 is turned on, the air-fuel ratio is leaned by a predetermined amount, and the air pump 3 is turned off. In S14 and S23, the leaning of the air-fuel ratio ends.

As described above, in the exhaust gas purifying apparatus for an internal combustion engine according to the third embodiment, when it is determined that the exhaust combustor has not ignited normally and soot has adhered to the catalyst 6, the use of the exhaust combustor is terminated. Thereafter, under a condition of a high catalyst temperature, the air-fuel ratio is made lean by a predetermined value, oxygen is supplied to the catalyst 6, and soot is burned and removed.

[0019]

When it is determined that the exhaust combustor has not ignited normally and soot has adhered to the catalyst, the soot adhered to the catalyst is removed, so that a decrease in the performance of the catalyst is suppressed.

[Brief description of the drawings]

FIG. 1 is a diagram corresponding to claims of the present invention.

FIG. 2 is a configuration diagram of an embodiment.

FIG. 3 is a flowchart according to the first embodiment.

FIG. 4 is a flowchart according to the second embodiment.

[Explanation of symbols]

 Reference Signs List 1 engine 2 exhaust pipe 3 air pump 4 spark plug 5 combustion chamber 6 catalyst 7 temperature sensor 8 control unit a ignition determination means b catalyst purification means

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI F01N 3/22 301 F01N 3/22 301B 301P 3/24 3/24 R ZAB ZABL (72) Inventor Kazuhiko Kaneshari Kanagawa, Yokohama, Kanagawa 2 Takara-cho, Nissan Motor Co., Ltd.

Claims (6)

[Claims] 1. An exhaust purification system for an internal combustion engine, comprising: a catalyst provided in an exhaust passage of an engine; and an exhaust combustor provided upstream of the catalyst, wherein it is determined whether the exhaust combustor is normally ignited. When the ignition determining means determines that normal ignition is not performed,
An exhaust purification device for an internal combustion engine, comprising: a catalyst purifying means for removing soot attached to a catalyst. 2. The ignition determining means determines that normal ignition has not occurred when a catalyst temperature has not reached a predetermined value after a lapse of a predetermined time from the ignition of the exhaust combustor. Item 2. An exhaust gas purification device for an internal combustion engine according to item 1. 3. The method according to claim 1, wherein the catalyst purifying unit is configured to perform a high load operation.
3. The exhaust gas purifying apparatus for an internal combustion engine according to claim 1, wherein soot is supplied to the catalyst to burn and remove soot. 4. The catalyst purifying means retards the ignition timing of the internal combustion engine and supplies oxygen to the catalyst to burn soot.
3. The exhaust gas purifying apparatus for an internal combustion engine according to claim 1, wherein the exhaust gas purifying apparatus is removed. 5. The exhaust gas purifying apparatus for an internal combustion engine according to claim 3, wherein said catalyst purifying means supplies oxygen to the catalyst using an oxygen supplying device of an exhaust combustor. 6. The exhaust gas purifying apparatus for an internal combustion engine according to claim 3, wherein the catalyst purifying means supplies oxygen to the catalyst by making the air-fuel ratio of the internal combustion engine lean.