JP2002309929A - Exhaust emission control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent emission of a sulfur compound to the atmosphere during recovery of a catalyst poisoned due to the sulfur compound derived from sulfur contents in fuel and device lubricant and to prevent the catalyst poisoning due to the sulfur compound. SOLUTION: This exhaust emission control device is provided with a secondary air supply means 24 arranged in an exhaust passage 6 between a first catalyst 10 and a second catalyst 22, a poisoning detection means 26 detecting whether the first catalyst is poisoned or not, and a poisoning recovery control 28. The exhaust emission control device 16, which has the first catalyst arranged in the exhaust passage and the second catalyst arranged on the upstream side beyond the first catalyst, for an internal combustion device is provided with an adsorption quantity determination means arranged in the second catalyst, a catalyst temperature determination means determining whether the both temperatures of the first catalyst and the second catalyst exceed a set temperature or not, and a poisoning recovery controlling means performing poisoning recovery control for the second catalyst.

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 a method for recovering from sulfur poisoning of a catalyst due to a sulfur compound derived from the sulfur content of fuel and system lubricating oil. The present invention relates to an exhaust gas purification device for an internal combustion engine that prevents the release of a compound and prevents poisoning of a catalyst by a sulfur compound.

[0002]

2. Description of the Related Art In the exhaust gas of an internal combustion engine, carbon monoxide (CO) and unburned hydrocarbon (HC) are mainly contained as harmful substances.
And nitrogen oxides (NOx). In addition, the exhaust gas contains small amounts of hydrogen (H2) as well as sulfur oxides (SOx), which are derived from the sulfur content of fuel and equipment lubricating oil.

As an exhaust gas purifying apparatus for an internal combustion engine, there is one disclosed in Japanese Patent Application Laid-Open No. Hei 10-317946. The exhaust gas purification device disclosed in this publication includes a three-way catalyst disposed in an exhaust pipe of an internal combustion engine, and a NOx storage reduction catalyst disposed downstream of the three-way catalyst in the exhaust pipe.
Ni or Ni oxide is added to the Ox storage reduction catalyst,
The purification ability of the Ox storage reduction catalyst is restored within a short time.

[0004] Another example is disclosed in Japanese Patent Application Laid-Open No. 11-350945. The method of operating an exhaust gas purifying apparatus for an internal combustion engine disclosed in this publication improves an exhaust gas purifying apparatus including a sulfur trap and a nitrogen oxide storage catalyst.

[0005] Furthermore, there is one disclosed in JP-A-2000-42370. An exhaust gas purifying catalyst device and a method of using the same disclosed in this publication prevent poisoning by sulfur in exhaust gas and improve NOx purifying performance under a lean atmosphere, which has not been shown to have sufficient activity with a conventional catalyst. Let me.

[0006] Furthermore, there is one disclosed in Japanese Utility Model Laid-Open Publication No. Sho 62-119415. A secondary air control device for an internal combustion engine disclosed in this publication is provided with an oxygen concentration detector and a catalyst in an exhaust passage of an exhaust system of the internal combustion engine, and purifies exhaust gas by a signal from the oxygen concentration detector. In the secondary air control device for an internal combustion engine that controls the injection of air, means is provided for injecting secondary air into the exhaust passage when the catalyst bed temperature of the catalyst is in the range of 600 degrees to 800 degrees.

[0007]

In a conventional exhaust gas purifying apparatus for an internal combustion engine, a catalyst for purifying exhaust gas adsorbs a sulfur compound (SOx, H2S) or the like in the exhaust gas, and causes a sulfur poisoning. This is causing performance degradation.

Particularly, in the case of a nitrogen oxide (NOx) storage catalyst, the effect of sulfur poisoning is enormous, and a number of measures for preventing sulfur poisoning have been studied (for example, Japanese Patent Application Laid-Open No. 7-21).
No. 7474).

And removing sulfur adsorbed on the catalyst,
In other words, when recovering the catalyst from sulfur poisoning, it is necessary to raise the temperature of the catalyst to a sulfur desorption temperature (for example, 600 ° C.) or higher and to enrich the air-fuel ratio.

At this time, since the adsorbed sulfur is released as hydrogen sulfide (H2S), there is a disadvantage that a sulfur odor is generated from the tail pipe.

In another patent application, purge control is performed after sulfur poisoning of the catalyst. However, in this patent application, only a relatively surface portion of a nitrogen oxide (NOx) storage catalyst can be desorbed. .

However, there is an inconvenience that it is difficult to desorb a deep portion of the catalyst layer, and it is not possible to sufficiently recover from sulfur poisoning.

[0013]

SUMMARY OF THE INVENTION In order to eliminate the above-mentioned disadvantages, the present invention provides a first catalyst capable of adsorbing or occluding at least nitrogen oxides in an exhaust passage, and a downstream side of the first catalyst. In an exhaust gas purifying apparatus for an internal combustion engine provided with a second catalyst capable of adsorbing a sulfur compound, secondary air for purifying exhaust gas can be supplied to an exhaust passage between the first catalyst and the second catalyst. Secondary air supply means, and poison detection means for detecting whether or not the first catalyst is poisoned by a sulfur compound; and when the poisoning of the first catalyst is detected by the poison detection means. Is provided with poison recovery control means for performing poison recovery control.

An exhaust gas of an internal combustion engine having a first catalyst capable of adsorbing or occluding nitrogen oxides at least in an exhaust passage, and a second catalyst capable of adsorbing a sulfur compound upstream of the first catalyst is provided. In the purification device, there is provided an adsorption amount determining means for determining whether or not the amount of the sulfur compound adsorbed on the second catalyst exceeds a set amount, and the adsorption amount determining means determines that the amount of the sulfur compound exceeds the set amount. If the temperature of the first catalyst and the temperature of the second catalyst are both higher than a set temperature, a catalyst temperature determining means is provided for determining whether the temperatures of the two catalysts are both set. When the temperature exceeds the temperature, poisoning recovery control means for performing poisoning recovery control of the second catalyst is provided.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION
When the first catalyst recovers from the poisoning by the sulfur compound, the sulfur compound released from the downstream side of the first catalyst is adsorbed by the second catalyst located on the downstream side, and the sulfur compound is released into the atmosphere. Preventing.

Further, the poisoning by the sulfur compound is reliably prevented by the second catalyst provided in the exhaust passage on the upstream side of the first catalyst.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the drawings.

FIGS. 1 to 4 show a first embodiment of the present invention. In FIG. 2, 2 is an internal combustion engine, 4 is an intake passage, and 6 is an exhaust passage.

In the intake system of the internal combustion engine 2, a throttle body 8 provided with a throttle valve (not shown) is provided on the upstream side, and the intake passage 4 on the downstream side of the throttle body 8 is provided in accordance with the number of cylinders, for example. The fuel tank is divided into four parts, and the injectors 10 are respectively provided in the respective branch intake passage portions, and the ignition plugs 12 are respectively disposed above the respective cylinders.

In the exhaust system of the internal combustion engine 2, an oxygen sensor, an air-fuel ratio sensor, or a nitrogen oxide (NOx) is provided at a junction of a branch exhaust passage connected to each cylinder.
A first exhaust sensor 14 comprising a sensor is provided, and an exhaust gas purification device 16 is provided in an exhaust passage 6 downstream of the first exhaust sensor 14, and an exhaust gas purification device 16 is provided in an exhaust passage 6 downstream of the exhaust gas purification device 16. Oxygen sensor, air-fuel ratio sensor,
Alternatively, a second exhaust sensor 18 composed of a nitrogen oxide (NOx) sensor is provided.

At this time, the exhaust gas purifying device 16
It has at least a first catalyst 20 that can adsorb or store nitrogen oxides, and a second catalyst 22 that is located downstream of the first catalyst 20 and that can adsorb sulfur compounds.

The first catalyst 20 and the second catalyst 22
A secondary air supply means (also referred to as a “secondary air supply device”) 24 capable of supplying secondary air for purifying exhaust gas to the exhaust passage 6 is provided in the exhaust passage 6 between the first catalyst 20 and the sulfur compound. Poisoning detecting means 26 for detecting whether or not the poisoning is performed by the first catalyst 2.
When the poisoning of 0 is detected, the poisoning recovery control means 28 which performs poisoning recovery control is provided.

More specifically, as shown in FIG. 2, a first temperature sensor 30 is provided on the first catalyst 20 and a second temperature sensor 32 is provided on the second catalyst 22, and these first and second catalysts are provided. The temperature sensors 30 and 32 are provided to be connected to the input side of the control means (also referred to as “control unit”) 34.

On the input side of the control means 34, first,
In addition to the second temperature sensors 30 and 32, the first and second exhaust sensors 14 and 18 and other various sensors, or detection means (not shown) for detecting engine rotation, boost, throttle opening, vehicle speed, water temperature, and the like. Is connected.

At this time, the poisoning detecting means 2 for detecting whether or not the first catalyst 20 is poisoned by a sulfur compound.
Reference numeral 6 denotes a group of various sensors connected to the input section of the control means 34.

Actually, the poisoning detecting means 26
The detection of whether or not the catalyst 20 is poisoned by the sulfur compound is performed by (1) a reading of an odometer (not shown), (2) an engine speed and an integrated value of a timer (not shown), and (3) a sulfur compound (SOx) sensor or nitrogen oxidation. Object (NO
x) Output value of the sensor (4) Catalyst deterioration detection by the first exhaust sensor 14 at the front and the second exhaust sensor 18 at the rear (5) The first exhaust catalyst which is a nitrogen oxide (NOx) storage type catalyst
This is performed using an integrated value or the like of a time when the use environment of the catalyst 20 is 600 degrees or less.

Further, on the output side of the control means 34,
An ignition control unit (not shown) for controlling the injector 10 and the ignition plug 12 and a secondary air supply means 24 are connected.

As shown in FIG. 2, the control means 34 is provided with a poisoning recovery control means 28 for performing poisoning recovery control.

The poisoning recovery control means 28 controls the poisoning recovery of the first catalyst 20 by enriching at least the air-fuel ratio. That is, in practice, the first catalyst 20 is heated up to the sulfur poisoning recovery temperature (for example, 600 degrees) by enriching the air-fuel ratio and, for example, retarding the ignition timing of the internal combustion engine 2. Thus, the sulfur poisoning of the first catalyst 20 is recovered.

At the same time as the poisoning recovery control means 28 controls the poisoning recovery of the first catalyst 20, a control signal is output from the control means 34 to the secondary air supply means 24, and the secondary air supply The means 24 controls the secondary air to be supplied to the second catalyst 22. And
By supplying the secondary air, hydrogen sulfide can be adsorbed or oxidized.

At this time, the secondary air supply means 24
The secondary air is supplied to the second catalyst 22 only when it is determined that the first catalyst 20 has the sulfur adsorption ability. In addition, the supply amount of the secondary air can be set to be increased or decreased according to the state of the first catalyst 20.

Further, the first catalyst 20 comprises a nitrogen oxide (NOx) storage type catalyst, and the second catalyst 22 comprises
It consists of a catalyst carrying at least nickel or iron.

Further, after the poisoning recovery control means 28 controls the poisoning recovery of the first catalyst 20, the first
When the poisoning deterioration of the catalyst 20 is eliminated, the second catalyst 2
2 also performs the sulfur purge control.

The first catalyst 20 can be a three-way catalyst instead of a nitrogen oxide (NOx) storage catalyst.

Next, the first catalyst 20 is treated with nitrogen oxide (NO
x) The operation will be described with reference to the control flowchart of FIG. In the control flowchart of FIG. 1, the first catalyst 20 is referred to as “upstream catalyst” and the second catalyst 2
2 is also referred to as “downstream catalyst”.

When the control program is started (102), various signals such as engine rotation, boost, throttle opening, vehicle speed, first and second exhaust sensors 14, 18 and odometer are taken into the control means 34 (104). .

Then, it is determined whether or not the first catalyst 20, which is the upstream catalyst, is poisoned and deteriorated (106). If the determination (106) is NO, the control program ends (124). If the determination (106) is YES, the poisoning recovery control of the first catalyst 20, which is the upstream catalyst, by the poisoning recovery control means 28 in the control means 34 is turned ON, and the secondary air Turn on supply means 24
Then, the secondary air is supplied to the second catalyst 22, and the timer is started (108).

After a lapse of a predetermined time (which can be referred to as “time required for recovery from poisoning”), the timer is ended (11).
0), and the poisoning recovery control of the first catalyst 20, which is the upstream catalyst, by the poisoning recovery control means 28 in the control means 34 is turned off.
At the same time, the secondary air supply means 24 is turned off to stop supplying secondary air to the second catalyst 22 (11).
2).

Thereafter, various signals such as engine rotation, boost, throttle opening, vehicle speed, first and second exhaust sensors 14, 18 and odometer are taken into the control means 34 (11).
4), it is determined whether the poisoning degradation of the first catalyst 20, which is the upstream catalyst, has been eliminated (116).

If the determination (116) is NO, the poisoning recovery control of the first catalyst 20, which is the upstream catalyst, by the poisoning recovery control means 28 in the control means 34 is turned ON.
A process of turning on the secondary air supply means 24 to supply secondary air to the second catalyst 22 and starting a timer (10)
Returning to 8), if the determination (116) is YES, the sulfur purge control of the second catalyst 22, which is the downstream catalyst, is turned on and the timer is started (118).

Then, after the elapse of a predetermined time, the timer is set to end (120), the sulfur purge control of the second catalyst 22, which is the downstream catalyst, is turned off (122), and the control program is shifted to end (124).

The operation will be described with reference to the control flowchart of FIG. 3 in which the first catalyst 20 is a three-way catalyst.

When the control program is started (202), various signals such as engine speed, boost, throttle opening, vehicle speed, first and second exhaust sensors 14, 18 and odometer are taken into the control means 34 (204). .

Then, it is determined whether or not the first catalyst 20, which is the upstream catalyst, is poisoned and degraded (206). If this determination (206) is NO, the control program ends (236). ), And if the determination (206) is YES, it is determined (208) whether or not the first catalyst 20, which is the upstream catalyst, has a sulfur adsorption capacity.

If the judgment (208) is YES,
The poisoning recovery control of the first catalyst 20, which is the upstream catalyst, by the poisoning recovery control means 28 in the control means 34 is turned ON, and the secondary air supply means 24 is turned ON to supply the secondary air to the second catalyst 22. Then, the timer is started (210), and if the determination (208) is NO, the poisoning recovery control of the first catalyst 20, which is the upstream catalyst, by the poisoning recovery control means 28 in the control means 34 is turned ON. At the same time, the timer is started (212).

Further, the poisoning recovery control of the first catalyst 20, which is the upstream catalyst, by the poisoning recovery control means 28 in the control means 34 is turned on, and the secondary air supply means 24 is turned on.
The secondary air is supplied to the second catalyst 22 and the timer is ended (214) after a lapse of a predetermined time from the processing (210) for starting the timer, and the upstream catalyst is controlled by the poisoning recovery control means 28 in the control means 34. The poisoning recovery control of the first catalyst 20 is turned off and the secondary air supply means 2 is turned off.
4 is turned off to stop supplying secondary air to the second catalyst 22 (216).

Thereafter, various signals such as engine rotation, boost, throttle opening, vehicle speed, first and second exhaust sensors 14, 18 and odometer are taken into the control means 34 (21).
8) It is determined whether the poisoning degradation of the first catalyst 20 as the upstream catalyst has been eliminated (220).

If the determination (220) is NO, the poisoning recovery control of the first catalyst 20, which is the upstream catalyst, by the poisoning recovery control means 28 in the control means 34 is turned ON.
A process of turning on the secondary air supply means 24 to supply the secondary air to the second catalyst 22, and starting the timer (21)
Returning to 0), if the determination (220) is YES, the sulfur purge control of the second catalyst 22, which is the downstream catalyst, is turned ON and the timer is started (222).

Further, the poisoning recovery control of the first catalyst 20, which is the upstream catalyst, by the poisoning recovery control means 28 in the control means 34 is turned ON, and a predetermined time elapses from the processing (212) for starting the timer. Later, the timer is set to the end (224), and the poisoning recovery control means 2 in the control means 34 is set.
Then, the poisoning recovery control of the first catalyst 20, which is the upstream catalyst, is turned off (226).

After that, various signals such as engine rotation, boost, throttle opening, vehicle speed, first and second exhaust sensors 14, 18 and odometer are taken into the control means 34 (22).
8) It is determined whether the poisoning degradation of the first catalyst 20 as the upstream catalyst has been eliminated (230).

If the determination (230) is NO, the poisoning recovery control of the first catalyst 20, which is the upstream catalyst, by the poisoning recovery control means 28 in the control means 34 is turned ON.
Returning to the process for starting the timer (212), if the determination (230) is YES, the sulfur purging control of the second catalyst 22, which is the downstream catalyst, is turned ON, and
The timer is started (222).

Then, after the elapse of the predetermined time, the timer is set to the end (232), the sulfur purge control of the second catalyst 22, which is the downstream catalyst, is turned off (234), and the process is shifted to the end of the control program (236).

FIG. 4 discloses a diagram showing the effect of the first embodiment in the case where the exhaust gas purifying apparatus 16 is used.

Thus, when the first catalyst 20 recovers from the poisoning by the sulfur compound, the sulfur compound released from the downstream side of the first catalyst 20 can be adsorbed by the second catalyst 22 located on the downstream side. Yes, it is possible to prevent the release of sulfur compounds into the atmosphere, which is practically advantageous.

The sulfur compounds adsorbed on the second catalyst 22 are desorbed after the sulfur compounds of the first catalyst 20 located on the upstream side are desorbed, so that the sulfur adsorption performance of the second catalyst 22 is improved. It is possible to sufficiently secure and prevent the discharge of hydrogen sulfide.

Further, the poisoning recovery control means 28 can recover the first catalyst 20 from sulfur poisoning by enriching at least the air-fuel ratio and performing the poisoning recovery control of the first catalyst 20.

Further, the poisoning recovery control means 28 controls the poisoning recovery of the first catalyst 20, and at the same time, controls the secondary air supply means 24 to supply the secondary air to the second catalyst 22. This can prevent the sulfur compound released by the poisoning recovery control from the first catalyst 20 from directly flowing into the second catalyst 22 located on the downstream side, and prevent the purification performance of the second catalyst 22 from deteriorating. It is possible to prevent.

Further, when the deterioration of the first catalyst 20 has progressed to some extent, the emission amount of the sulfur compound decreases.
Since it is not necessary to perform the secondary air supply control, the secondary air supply means 24 supplies the secondary air to the second catalyst 22 only when it is determined that the first catalyst 20 has the sulfur adsorption ability. Functions have been added to avoid unnecessary control and improve control reliability.

After the poisoning recovery control means 28 controls the poisoning recovery of the first catalyst 20, if the poisoning deterioration of the first catalyst 20 is eliminated, the second catalyst 22
By performing the sulfur purge control, the sulfur purge control of the second catalyst is performed after the poisoning recovery control of the first catalyst 20 is completely completed, so that the release of sulfur compounds can be reliably prevented. It is possible.

FIGS. 5 to 7 show a second embodiment of the present invention. In the second embodiment, parts that perform the same functions as those in the first embodiment will be described with the same reference numerals.

A feature of the second embodiment is that the second catalyst 302 is provided in the exhaust passage 6 upstream of the first catalyst 20.
It is in the point that was arranged.

That is, a first catalyst 20 composed of a nitrogen oxide (NOx) storage type catalyst capable of adsorbing or storing at least nitrogen oxide is provided in the exhaust passage 6.
Second catalyst 302 capable of adsorbing sulfur compounds further upstream
Is provided.

Then, there is provided an adsorption amount determining means 304 for determining whether or not the amount of the sulfur compound adsorbed by the second catalyst 302 exceeds a set amount.
When it is determined that the sulfur compound amount exceeds the set amount, the catalyst temperature determining means 306 that determines whether the temperatures of both the first catalyst 20 and the second catalyst 302 exceed the set temperature is provided, The poisoning recovery control that performs the poisoning recovery control of the second catalyst 302 when the temperatures of the two catalysts, the first and second catalysts 20 and 302, both exceed the set temperature by the catalyst temperature determination means 306. A configuration is provided in which the means 308 is provided.

The poisoning recovery control means 308 controls the poisoning recovery of the second catalyst 302 by enriching the air-fuel ratio.

The exhaust gas purifying device 3 of the internal combustion engine 2
Reference numeral 10 denotes catalyst temperature increasing means (not shown) for controlling the temperature of the lower catalyst to increase when at least one of the temperatures of both the first catalyst 20 and the second catalyst 302 is lower than the set temperature. Is provided.

As the catalyst temperature raising means, the ignition timing of the internal combustion engine 2 is controlled by, for example, retarding the ignition timing.
It is conceivable to raise the temperature of the catalyst 20 or the second catalyst 302 to the sulfur poisoning recovery temperature (for example, 600 degrees).

Further, the poisoning recovery control means 308 controls the poisoning recovery of the second catalyst 302 only when it is determined that the first catalyst 20 has the sulfur adsorption ability.

Further, the second catalyst 302 comprises a catalyst carrying at least nickel or iron.

Reference numeral 30 denotes a first temperature sensor (also referred to as “temperature sensor A”), 32 denotes a second temperature sensor (also referred to as “temperature sensor B”), and 34 denotes control means.

The first catalyst 20 may be a three-way catalyst instead of a nitrogen oxide (NOx) storage catalyst.

Next, the first catalyst 20 is treated with nitrogen oxide (NO
x) The operation will be described with reference to the control flowchart of FIG. In the control flowchart of FIG. 6, the first catalyst 20 is the “downstream catalyst” and the second catalyst 2
2 is also referred to as “upstream catalyst”.

When the control program is started (402), various signals such as engine speed, boost, throttle opening, vehicle speed, first and second exhaust sensors 14, 18 and odometer are taken into the control means 34 (404). .

Then, it is determined (406) whether or not the amount of sulfur adsorbed by the second catalyst 302, which is the upstream catalyst, is large. If this determination (406) is NO, the control program ends (428) If the determination (406) is YES, the first temperature sensor 30 as the temperature sensor A exceeds the set temperature of 600 degrees, and the second temperature sensor 32 as the temperature sensor B sets the set temperature. Is determined (408) as to whether or not the angle exceeds 600 degrees.

If this judgment (408) is YES, that is, if the temperatures of both the first and second catalysts 20 and 302 exceed the set temperature of 600 degrees, the poisoning recovery control means in the control means 34 The second catalyst 3 which is the upstream catalyst according to 308
02, the poisoning recovery control is turned ON, the air-fuel ratio is enriched, and the process proceeds to a process (410) for starting a timer, and the determination (408) is NO, that is, the first and second catalysts 2
When the temperature of one of the catalysts 0 and 302 is equal to or lower than the set temperature of 600 degrees, the catalyst having a lower temperature in the first catalyst 20 or the second catalyst 302 is recovered by the catalyst temperature raising means. A process of turning on the catalyst temperature raising control for raising the temperature to a temperature (for example, 600 degrees), making the air-fuel ratio lean, and starting the timer (412).
Move to

After the process (412), a timer is set to end (414) after a lapse of a predetermined time (in other words, "time required for recovery from poisoning"), and the catalyst temperature raising control by the catalyst temperature raising means is performed. OFF (416), and then the engine speed, boost, throttle opening, vehicle speed,
Various signals from the second exhaust sensors 14 and 18 and the odometer are taken into the control means 34 (418), and the first temperature sensor 30 as the temperature sensor A exceeds the set temperature of 600 degrees and the temperature sensor B as the first temperature sensor B. (2) Whether the temperature sensor 32 exceeds the set temperature of 600 degrees or not (40
Return to 8).

The poisoning recovery control of the second catalyst 302, which is the upstream catalyst, by the poisoning recovery control means 308 in the control means 34 is turned ON, the air-fuel ratio is made rich, and the timer is started (step 410). Thereafter, the timer is set to the end (420) after a predetermined time (which can be referred to as "time required for poisoning recovery"), and the second catalyst 30 which is the upstream catalyst by the poisoning recovery control means 308 in the control means 34.
The poisoning recovery control 2 is turned off, and the air-fuel ratio is made lean to bring it into a stoichiometric state (422).

Thereafter, various signals such as engine rotation, boost, throttle opening, vehicle speed, first and second exhaust sensors 14, 18 and odometer are taken into the control means 34 (42).
4) It is determined whether or not the poisoning degradation of the second catalyst 302 as the upstream catalyst has been eliminated (426).

If the determination (426) is NO, the first temperature sensor 30 as the temperature sensor A exceeds the set temperature of 600 degrees and the second temperature sensor 32 as the temperature sensor B is set at the set temperature. Returning to the determination (408) of whether or not the angle exceeds a certain 600 degrees, if the determination (426) is YES, the process is shifted to the end (428) of the control program.

The operation will be described with reference to the control flowchart of FIG. 7 in which the first catalyst 20 is a three-way catalyst.

When the control program is started (502), various signals such as engine rotation, boost, throttle opening, vehicle speed, first and second exhaust sensors 14, 18 and odometer are taken into the control means 34 (504). .

Then, it is determined whether the amount of sulfur adsorbed by the second catalyst 302, which is the upstream catalyst, is large (506). If the determination (506) is NO, the control program ends (530). ), And if the determination (506) is YES, the process proceeds to a determination (508) as to whether or not the first catalyst 20, which is the downstream catalyst, has a sulfur adsorption capacity.

If the judgment (508) is NO, the process directly proceeds to the end (530) of the control program, and if the judgment (508) is YES, the first temperature sensor 30 as the temperature sensor A is set. Over the temperature of 600 degrees,
In addition, the process proceeds to the determination (510) as to whether or not the second temperature sensor 32 as the temperature sensor B exceeds the set temperature of 600 degrees.

If this determination (510) is YES, that is, if the temperatures of both the first and second catalysts 20 and 302 exceed the set temperature of 600 degrees, the poisoning recovery control means in the control means 34 The second catalyst 3 which is the upstream catalyst according to 308
02, the poisoning recovery control is turned ON, the air-fuel ratio is enriched, and the process proceeds to a process of starting a timer (512), and the determination (510) is NO, that is, the first and second catalysts 2
When the temperature of one of the catalysts 0 and 302 is equal to or lower than the set temperature of 600 degrees, the catalyst having a lower temperature in the first catalyst 20 or the second catalyst 302 is recovered by the catalyst temperature raising means. The process of turning on the catalyst temperature raising control for raising the temperature to a temperature (for example, 600 degrees), making the air-fuel ratio lean, and starting the timer (514).
Move to

After the process (514), a timer is set to end (516) after a lapse of a predetermined time (which can be referred to as “time required for poisoning recovery”), and the catalyst temperature raising control by the catalyst temperature raising means is performed. OFF (518), and then the engine speed, boost, throttle opening, vehicle speed,
Various signals from the second exhaust sensors 14 and 18 and the odometer are taken into the control means 34 (520), and the first temperature sensor 30 as the temperature sensor A exceeds the set temperature of 600 degrees and the second temperature sensor B as the temperature sensor B. (2) Determine whether the temperature sensor 32 exceeds the set temperature of 600 degrees (51)
Return to 0).

The poisoning recovery control of the second catalyst 302 as the upstream catalyst by the poisoning recovery control means 308 in the control means 34 is turned ON, the air-fuel ratio is enriched, and the timer is started (512). Thereafter, the timer is set to end (522) after the elapse of a predetermined time (which can be rephrased as "time required for poisoning recovery"), and the poisoning recovery control means 308 in the control means 34 controls the second catalyst 30 which is the upstream catalyst.
The poisoning recovery control 2 is turned off, and the air-fuel ratio is made lean to bring it into a stoichiometric state (524).

Thereafter, various signals such as engine rotation, boost, throttle opening, vehicle speed, first and second exhaust sensors 14, 18 and odometer are taken into the control means 34 (52).
6) It is determined (528) whether or not the poisoning degradation of the second catalyst 302 as the upstream catalyst has been eliminated.

If the determination (528) is NO, the first temperature sensor 30 as the temperature sensor A exceeds the set temperature of 600 degrees and the second temperature sensor 32 as the temperature sensor B is set at the set temperature. Returning to the determination (510) as to whether or not the angle exceeds a certain 600 degrees, if the determination (528) is YES, the process is shifted to the end (530) of the control program.

Thus, the second catalyst 302 provided in the exhaust passage 6 on the upstream side of the first catalyst 20 can reliably prevent poisoning by sulfur compounds.

Further, the poisoning recovery control means 308 can recover the second catalyst 302 from sulfur poisoning by enriching the air-fuel ratio and performing poisoning recovery control of the second catalyst 302.

Further, the exhaust gas purifying device 31 of the internal combustion engine 2
0 indicates that at least one of the temperatures of the first catalyst 20 and the second catalyst 302 is lower than the set temperature,
By controlling the temperature of the low-temperature catalyst by the catalyst temperature raising means (not shown), the poisoning recovery control is performed only when the temperature of the catalyst exceeds the set temperature, and the emission of sulfur compounds is performed. Can be reliably prevented.

Further, when the deterioration of the first catalyst 20 has progressed to some extent, the emission amount of the sulfur compound decreases.
Since there is no need to perform poisoning recovery control of the second catalyst 302 located on the upstream side, the poisoning recovery control means 308
In addition, a function of performing poisoning recovery control of the second catalyst 302 only when it is determined that the first catalyst 20 has the sulfur adsorption ability is added to avoid unnecessary control and improve control reliability. I have.

The present invention is not limited to the above-described first and second embodiments, and various application modifications are possible.

For example, in the first and second embodiments of the present invention, at least one first catalyst capable of adsorbing or occluding at least nitrogen oxide and one second catalyst capable of adsorbing one sulfur compound are used. Although it was configured to provide a total of two catalysts,
A special configuration in which three or more catalysts are provided is also possible.

That is, for example, when three catalysts are provided, the sulfur compound can be adsorbed upstream of the first catalyst in the state of the first and second catalysts disclosed in the first embodiment. A third catalyst is provided.

Then, the upstream side and the downstream side of the first catalyst can be sandwiched between the third catalyst and the second catalyst capable of adsorbing the sulfur compound, and the poisoning of the first catalyst by the sulfur compound can be performed by the third catalyst. In the case where the first catalyst is poisoned by a sulfur compound due to a decrease in the performance of the third catalyst or the like, the sulfur compound released from the downstream side of the first catalyst is transferred to the downstream side. It can be adsorbed by the located second catalyst and can prevent the release of sulfur compounds into the atmosphere.

[0096]

As described above in detail, according to the present invention, a first catalyst capable of adsorbing or occluding at least nitrogen oxide is provided in an exhaust passage, and a sulfur compound can be adsorbed downstream of the first catalyst. In an exhaust gas purifying apparatus for an internal combustion engine provided with a suitable second catalyst, secondary air supply means capable of supplying secondary air for purifying exhaust gas to the exhaust passage is provided in an exhaust passage between the first catalyst and the second catalyst. And a poisoning detecting means for detecting whether the first catalyst is poisoned by a sulfur compound,
When poisoning of the first catalyst is detected by the poisoning detecting means, poisoning recovery control means for performing poisoning recovery control is provided.
When the first catalyst recovers from the poisoning by the sulfur compound, the sulfur compound released from the downstream side of the first catalyst can be adsorbed by the second catalyst located on the downstream side, and the sulfur compound is released into the atmosphere. Can be prevented.

[0097] Further, a first catalyst capable of adsorbing or occluding at least nitrogen oxides is provided in the exhaust passage, and a second catalyst capable of adsorbing a sulfur compound is provided upstream of the first catalyst. The apparatus is provided with an adsorption amount determining means for determining whether or not the amount of the sulfur compound adsorbed by the second catalyst exceeds the set amount, and when the amount of the sulfur compound is determined to exceed the set amount by the adsorption amount determining means. And a catalyst temperature determining means for determining whether or not both the temperature of the first catalyst and the temperature of the second catalyst exceed the set temperature, and the temperature of both catalysts exceeds the set temperature by the catalyst temperature determining means. In such a case, the poisoning recovery control means for performing the poisoning recovery control of the second catalyst is provided. Prevent poisoning reliably Rukoto is possible.

[Brief description of the drawings]

FIG. 1 is a control flowchart showing a first embodiment of the present invention, in which a first catalyst is a nitrogen oxide (NOx) storage catalyst.

FIG. 2 is a schematic configuration diagram of an exhaust gas purification device for an internal combustion engine.

FIG. 3 is a control flowchart in which a first catalyst is a three-way catalyst.

FIG. 4 is a diagram showing a detected amount of hydrogen sulfide (H2S) and an elapsed time.

FIG. 5 is a control flowchart showing a second embodiment of the present invention in which the first catalyst is a nitrogen oxide (NOx) storage type catalyst.

FIG. 6 is a schematic configuration diagram of an exhaust gas purification device for an internal combustion engine.

FIG. 7 is a control flowchart in which the first catalyst is a three-way catalyst.

[Explanation of symbols]

2 Internal combustion engine 4 Intake passage 6 Exhaust passage 8 Throttle body 10 Injector 12 Spark plug 14 First exhaust sensor 16 Exhaust gas purifier 18 Second exhaust sensor 20 First catalyst 22 Second catalyst 24 Secondary air supply means (“secondary” 26 Poisoning detection means 28 Poisoning recovery control means 30 First temperature sensor 32 Second temperature sensor 34 Control means (also referred to as "control unit")

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat ゛ (Reference) F01N 3/22 311 F01N 3/24 C 3/24 R 3/28 301C 3/28 301 301G F02D 41/04 305A F02D 41/04 305 41/14 310K 41/14 310 310P 43/00 301E 43/00 301 301T 45/00 312R 45/00 312 312T 314Z 314 B01D 53 / 36K F term (reference) 3G084 AA03 AA04 BA09 BA13 BA25 DA10 DA14 DA19 DA22 DA27 DA28 EA11 EB01 FA05 FA11 FA20 FA26 FA27 FA29 FA30 3G091 AA02 AA17 AA23 AA28 AB01 AB03 AB06 AB08 BA11 BA14 BA20 BA33 CA22 CB02 DA01 DA02 DA04 DB06 DB10 DC01 EA01 EA06 EA30 EA18 EA30 EA16 EA30 GA06 GB01W HA08 HA36 HA39 HA42 HA47 HB07 3G301 HA01 HA06 HA15 JA15 JA21 JA25 JB09 LA01 L B02 MA01 MA11 MA18 NA04 NA06 NA07 NA08 ND01 NE01 NE06 NE13 NE15 PA07A PA07B PD01A PD01B PD12A PD12B PE01A PE01B PF01A PF01B 4D048 AA02 AA06 AA13 AA18 AB01 AB02 BA36Y BA38Y BC01 BD02 DA01 DA02

Claims (11)

[Claims] 1. Exhaust gas of an internal combustion engine provided with a first catalyst capable of adsorbing or occluding at least nitrogen oxides in an exhaust passage, and a second catalyst capable of adsorbing a sulfur compound downstream of the first catalyst. In the purification device, the first catalyst and the second catalyst
Poisoning detection for detecting whether or not the first catalyst is poisoned by a sulfur compound is provided in the exhaust passage between the catalysts with secondary air supply means capable of supplying secondary air for purifying exhaust gas to the exhaust passage. An exhaust gas purifying apparatus for an internal combustion engine, further comprising: a poisoning recovery control unit for performing poisoning recovery control when poisoning of the first catalyst is detected by the poisoning detection unit. 2. The exhaust gas purifying apparatus for an internal combustion engine according to claim 1, wherein said poisoning recovery control means controls the poisoning recovery of the first catalyst by enriching at least the air-fuel ratio. 3. The method according to claim 2, wherein the poisoning recovery control means controls the poisoning recovery of the first catalyst and simultaneously controls the secondary air supply means to supply the secondary air to the second catalyst. An exhaust gas purifying apparatus for an internal combustion engine according to claim 1. 4. The exhaust gas of an internal combustion engine according to claim 3, wherein said secondary air supply means supplies secondary air to the second catalyst only when it is determined that the first catalyst has a sulfur adsorption ability. Purification device. 5. The exhaust gas purifying apparatus for an internal combustion engine according to claim 4, wherein said first catalyst is a three-way catalyst. 6. When the poisoning deterioration of the first catalyst is eliminated after the poisoning recovery control of the first catalyst is performed by the poisoning recovery control means, sulfur purge control of the second catalyst is performed. An exhaust gas purifying apparatus for an internal combustion engine according to any one of claims 1 to 4. 7. An exhaust gas of an internal combustion engine in which a first catalyst capable of adsorbing or occluding at least nitrogen oxide is provided in an exhaust passage, and a second catalyst capable of adsorbing a sulfur compound is provided upstream of the first catalyst. In the purification device, there is provided an adsorption amount determining means for determining whether or not the amount of the sulfur compound adsorbed on the second catalyst exceeds a set amount, and the adsorption amount determining means determines that the amount of the sulfur compound exceeds the set amount. If the temperature of the first catalyst and the temperature of the second catalyst are both higher than a set temperature, a catalyst temperature determining means is provided for determining whether the temperatures of the two catalysts are both set. An exhaust gas purifying apparatus for an internal combustion engine, further comprising a poisoning recovery control means for performing poisoning recovery control of the second catalyst when the temperature exceeds the temperature. 8. The exhaust gas purifying apparatus for an internal combustion engine according to claim 7, wherein said poisoning recovery control means performs poisoning recovery control of the second catalyst by enriching the air-fuel ratio. 9. The exhaust gas purifying apparatus for an internal combustion engine raises the temperature of a low-temperature catalyst when at least one of the temperatures of both the first catalyst and the second catalyst is lower than a set temperature. The exhaust gas purifying apparatus for an internal combustion engine according to claim 7, further comprising a catalyst temperature increasing means for controlling the temperature of the exhaust gas. 10. The exhaust gas of an internal combustion engine according to claim 7, wherein the poisoning recovery control means performs the poisoning recovery control of the second catalyst only when it is determined that the first catalyst has the sulfur adsorption ability. Gas purification device. 11. The exhaust gas purifying apparatus for an internal combustion engine according to claim 1, wherein the second catalyst carries at least nickel or iron.