JP2003206795A - Method and device for controlling exhaust emission of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a waste of fuel by suppressing the degradation of exhaust emission attributable to impairment of the catalyst reaction of a NOx occlusion reduction catalyst by hydrocarbon. <P>SOLUTION: When it is determined that a flow-in HC concentration thccl into the NOx occlusion reduction catalyst is larger than an excessive concentration determination value thmax ('YES' in S116), HC control by the NOx occlusion reduction catalyst cannot be achieved, and NOx control can be impaired by HC heavily covering a catalyst surface. Accordingly, the implementation of a rich spike is prohibited in advance, or stopped in the way by implementing rich spike prohibition (S120). Since a situation that the catalyst surface is heavily covered by HC can be prevented, the degradation of the exhaust emission attributable to the impairment of the catalyst reaction of the NOx occlusion reduction catalyst by HC can be suppressed, and a waste of fuel can be prevented. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas purification method and an exhaust gas purification apparatus for an internal combustion engine having an NOx storage reduction catalyst in an exhaust system.

[0002]

2. Description of the Related Art As an exhaust gas purification system for an internal combustion engine, NOx in the exhaust gas is stored during execution of stratified charge combustion or lean combustion (a fuel concentration lower than the theoretical air-fuel ratio) to obtain a theoretical air-fuel ratio or rich (theoretical air-fuel ratio). Higher fuel concentration than
There is known a system using a NOx storage reduction catalyst that releases NOx that has been stored and reduces and purifies it by HC (hydrocarbon) or CO in the exhaust when combustion starts and the oxygen concentration in the exhaust decreases. -161105). In such a system, NOx in the NOx storage reduction catalyst
When the stored amount reaches a predetermined amount, a rich spike is executed to supply a high concentration fuel to the internal combustion engine, thereby discharging a large amount of unburned gas such as HC and CO in the exhaust gas. The unburned gas acts as a reducing agent on the NOx storage reduction catalyst, and thereby the stored NOx is reduced and disappears, so that the NOx storage reduction catalyst can store NOx again.

When such a rich spike is executed at a low load such as at the time of idling, a large change in the air-fuel ratio may occur suddenly to cause misfire.
For this reason, in the disclosed technique, a large change in the air-fuel ratio is suppressed during a rich spike to prevent misfire.

[0004]

However, in an operating state where a large amount of HC may be contained in the exhaust gas, for example, at low load or low rotation such as idling, NO is generated.
x Among the occlusion reduction catalysts, the surface of the catalyst such as platinum component may be thickly covered with hydrocarbon. Further, the surface of the catalyst may be thickly covered with hydrocarbon due to the rich spike performed in the above operating state.

When the surface of the catalyst is thickly covered with hydrocarbons in this way, the adhering hydrocarbons hinder the catalytic reaction and the reduction of the stored NOx does not proceed sufficiently. Therefore, even if the rich spike is executed or the rich spike is continued, a situation in which the NOx released in the rich atmosphere cannot be sufficiently reduced and purified, and the exhaust emission may be deteriorated and fuel is wasted. Become.

An object of the present invention is to suppress deterioration of exhaust emission due to inhibition of catalytic reaction of NOx storage reduction catalyst by hydrocarbons and prevent waste of fuel.

[0007]

[Means for Solving the Problems] Means for achieving the above-mentioned objects and their effects will be described below. The exhaust purification method for an internal combustion engine according to claim 1, wherein NOx stored in a NOx storage reduction catalyst provided in an exhaust system of the internal combustion engine.
A method for purifying exhaust gas of an internal combustion engine for performing a rich spike in which a reducing component containing hydrocarbon is supplied by exhaust gas when reducing NO, wherein exhaust gas purification in the NOx storage reduction catalyst is performed by hydrocarbons flowing into the NOx storage reduction catalyst. When it is determined that the rich spike may be hindered, execution of the rich spike is prohibited or stopped midway.

When there is a possibility that the surface of the catalyst is thickly covered by the hydrocarbons flowing into the NOx storage reduction catalyst as described above and the exhaust purification of the NOx storage reduction catalyst may be hindered, execution of rich spike is prohibited in advance or Since it is stopped midway, the surface of the catalyst is not thickly covered with hydrocarbons to the extent of a problem, and it is possible to prevent a situation in which exhaust gas purification is hindered.

Therefore, if the determination is made before the execution of the rich spike, the execution of the rich spike is prohibited even if the rich spike condition is satisfied, so that the surface of the catalyst is thickly covered with hydrocarbons. Therefore, a large amount of unpurified hydrocarbon is not released downstream of the NOx storage reduction catalyst. Moreover, in lean combustion or stratified charge combustion, the NOx concentration is relatively low, and even if the exhaust gas is in a lean atmosphere, the stored NOx is not discharged. In this way, it is possible to suppress the deterioration of exhaust emission due to the inhibition of the catalytic reaction of the NOx storage reduction catalyst by the hydrocarbon and prevent the fuel waste.

If the determination is made during the execution of the rich spike, the rich spike is stopped immediately. At this time, the catalyst surface is beginning to be covered with hydrocarbons because the rich spike has already been done halfway, but to the extent of the problem, the catalyst surface is not covered with hydrocarbons and exhaust purification will not be hindered. . Since the exhaust gas is temporarily in the rich atmosphere, the stored NOx is partially released from the NOx storage reduction catalyst. However, since the catalytic action is sufficient, the hydrocarbons present on the catalyst surface are oxidized by the released NOx and converted into carbon dioxide gas and water for purification, and further NOx itself is deprived of oxygen and reduced to nitrogen gas for purification. To be done. In this way N
Exhaust emission deterioration due to the inhibition of the catalytic reaction of the Ox storage reduction catalyst can be suppressed, and the fuel waste can be prevented.

According to a second aspect of the present invention, there is provided an exhaust gas purification method for an internal combustion engine, wherein when reducing NOx stored in a NOx storage reduction catalyst provided in an exhaust system of the internal combustion engine, a reducing component containing hydrocarbon is supplied by exhaust gas. A method for purifying exhaust gas of an internal combustion engine that executes rich spike, wherein when it is determined that NOx purification in the NOx storage reduction catalyst may be hindered by hydrocarbons flowing into the NOx storage reduction catalyst, the rich spike Is prohibited in advance or stopped midway.

When there is a possibility that the surface of the catalyst is thickly covered by the hydrocarbons flowing into the NOx storage reduction catalyst in this way and the NOx purification by the NOx storage reduction catalyst may be hindered, execution of the rich spike is prohibited in advance or Since the catalyst is stopped midway, it is possible to prevent the situation where the surface of the catalyst is not thickly covered with hydrocarbons to the extent of a problem and NOx purification is hindered.

By the operation as described in claim 1, NOx storage reduction by hydrocarbons is carried out regardless of whether the judgment is made before the rich spike execution or during the rich spike execution. Exhaust emission deterioration due to the inhibition of the catalytic reaction of the catalyst can be suppressed, and fuel waste can be prevented.

According to a third aspect of the present invention, there is provided an exhaust gas purification method for an internal combustion engine, wherein when reducing NOx stored in a NOx storage reduction catalyst provided in an exhaust system of the internal combustion engine, a reducing component containing hydrocarbon is supplied by exhaust gas. A method of purifying exhaust gas of an internal combustion engine that executes a rich spike, wherein when it is determined that the hydrocarbon purification capacity of the NOx storage reduction catalyst cannot process the hydrocarbons flowing into the NOx storage reduction catalyst, the rich It is characterized in that the execution of spikes is prohibited in advance or stopped midway.

As described above, when the hydrocarbon purification capability of the NOx storage reduction catalyst cannot process the hydrocarbons flowing into the NOx storage reduction catalyst, execution of the rich spike is prohibited or stopped midway. The surface of the catalyst is not thickly covered with hydrocarbon to the extent that it becomes a problem, and it is possible to prevent the situation where purification is hindered.

By the operation as described in claim 1, the NOx storage reduction by the hydrocarbon is carried out regardless of whether the judgment is made before the rich spike execution or during the rich spike execution. Exhaust emission deterioration due to the inhibition of the catalytic reaction of the catalyst can be suppressed, and fuel waste can be prevented.

According to a fourth aspect of the present invention, there is provided an exhaust gas purification method for an internal combustion engine, wherein when reducing NOx stored in a NOx storage reduction catalyst provided in an exhaust system of the internal combustion engine, a reducing component containing hydrocarbon is supplied by exhaust gas. An exhaust gas purification method for an internal combustion engine that executes a rich spike, wherein the execution of the rich spike is prohibited in advance or stopped midway when the concentration of hydrocarbons flowing into the NOx storage reduction catalyst is higher than an excessive concentration determination value. Characterize.

When the concentration of hydrocarbons flowing into the NOx storage reduction catalyst is higher than the excess concentration determination value, NO
x The amount of hydrocarbons purified by the occlusion reduction catalyst is NOx
Assuming that the amount of hydrocarbons flowing into the storage reduction catalyst cannot be kept up with, the execution of the rich spike is prohibited or stopped midway.

As a result, due to the action as described in claim 1, NOx due to hydrocarbons is obtained whether the determination is made before the rich spike execution or during the rich spike execution. It is possible to suppress deterioration of exhaust emission due to the inhibition of the catalytic reaction of the storage reduction catalyst and prevent fuel waste.

According to a fifth aspect of the present invention, there is provided an exhaust gas purification method for an internal combustion engine, wherein when reducing NOx stored in a NOx storage reduction catalyst provided in an exhaust system of the internal combustion engine, a reducing component containing hydrocarbon is supplied by exhaust gas. An exhaust gas purification method for an internal combustion engine that executes a rich spike, wherein when the hydrocarbon flow rate per unit time flowing into the NOx storage reduction catalyst is larger than an excessive flow rate determination value, execution of the rich spike processing is prohibited in advance or It is characterized by stopping halfway.

When the hydrocarbon flow rate per unit time flowing into the NOx storage reduction catalyst is larger than the excessive flow rate determination value, the amount of hydrocarbons purified by the NOx storage reduction catalyst flows into the NOx storage reduction catalyst. Assuming that the amount of hydrogen cannot be caught up, execution of rich spike is prohibited in advance or stopped midway.

As a result, due to the action as described in claim 1, NOx due to hydrocarbons is obtained whether the determination is performed before the rich spike execution or during the rich spike execution. It is possible to suppress deterioration of exhaust emission due to the inhibition of the catalytic reaction of the storage reduction catalyst and prevent fuel waste.

In an exhaust gas purification method for an internal combustion engine according to a sixth aspect, in any one of the first to fifth aspects, the process of prohibiting or stopping the execution of the rich spike in advance is:
The feature is that it is not performed except when idle.

Usually, the problem that the catalyst reaction inhibition of the NOx storage reduction catalyst due to the thick coating of the surface of the catalyst by the hydrocarbon becomes a problem at the time of idling at a low load and a low rotation speed. It can be said that nothing happens. Therefore, as described above, the process of prohibiting the rich spike execution in advance or stopping the rich spike may not be performed except during the idle time. As a result, it is not necessary to perform unnecessary judgment processing.

According to a seventh aspect of the present invention, there is provided an exhaust gas purification method for an internal combustion engine according to any one of the first to sixth aspects, wherein a start catalyst having an oxygen storage function is arranged upstream of the NOx storage reduction catalyst in the exhaust system. It is characterized in that the amount of hydrocarbons flowing into the NOx storage reduction catalyst, the concentration of hydrocarbons or the flow rate of hydrocarbons per unit time is determined in consideration of the degree of purification of hydrocarbons by the start catalyst.

NOx is a three-way catalyst having a function of storing oxygen in order to remove hydrocarbons, carbon monoxide and the like released in large quantities at the time of starting the internal combustion engine.
When the storage reduction catalyst is arranged on the upstream side of the exhaust system, the amount of hydrocarbons flowing into the NOx storage reduction catalyst, the hydrocarbon concentration, or the flow rate of hydrocarbons per unit time can be adjusted by the start catalyst to purify the hydrocarbons. It depends on the degree.

Therefore, the amount of hydrocarbons flowing into the NOx storage reduction catalyst, the concentration of hydrocarbons or the flow rate of hydrocarbons per unit time can be accurately determined by considering the degree of purification of hydrocarbons by the start catalyst. It is possible to appropriately suppress the deterioration of exhaust emission due to the inhibition of the catalytic reaction of the NOx storage reduction catalyst by the hydrocarbon, and it is possible to appropriately prevent the fuel waste.

According to an eighth aspect of the present invention, there is provided an exhaust gas purification method for an internal combustion engine according to the seventh aspect, based on an air-fuel ratio detected from an exhaust component upstream of the start catalyst and a bed temperature of the start catalyst. It is characterized in that the degree of purification of hydrocarbons by the start catalyst is obtained.

It has been found that the air-fuel ratio detected from the exhaust component upstream of the start catalyst and the bed temperature of the start catalyst are related to the degree of purification of hydrocarbons by the start catalyst. Therefore, by determining the degree of purification of hydrocarbons by the start catalyst based on the air-fuel ratio detected from the exhaust gas component upstream of the start catalyst and the bed temperature of the start catalyst, the hydrocarbons flowing into the NOx storage reduction catalyst are obtained. The amount, hydrocarbon concentration or hydrocarbon flow rate per unit time can be accurately determined. Therefore, it is possible to appropriately suppress the deterioration of the exhaust emission due to the inhibition of the catalytic reaction of the NOx storage reduction catalyst by the hydrocarbon, and it is possible to appropriately prevent the fuel waste.

According to a ninth aspect of the present invention, there is provided an exhaust gas purification apparatus for an internal combustion engine, which obtains a NOx storage amount in a NOx storage reduction catalyst provided in an exhaust system of the internal combustion engine, and when the NOx storage amount reaches a reference value, carbonization is performed. By executing a rich spike in which a reducing component containing hydrogen is supplied by exhaust, the NO
An exhaust gas purification device for an internal combustion engine that reduces NOx stored in an x storage reduction catalyst, wherein the hydrocarbon detection means determines the amount of hydrocarbons flowing into the NOx storage reduction catalyst and the hydrocarbon detection means. Depending on the inflowing hydrocarbon amount,
When there is a possibility that exhaust purification by the NOx storage reduction catalyst may be hindered, rich spike prohibiting means for prohibiting or stopping the execution of the rich spike in advance is provided.

When the rich spike prohibiting means determines that the inflowing hydrocarbon amount obtained by the hydrocarbon detecting means may hinder the exhaust purification of the NOx storage reduction catalyst, the rich spike prohibiting is prohibited in advance or stopped midway. is doing. For this reason, the surface of the catalyst is not thickly covered with hydrocarbons to the extent that it becomes a problem, which prevents the situation where exhaust purification is hindered.

The rich spike prohibiting means judges that the inflowing hydrocarbon amount obtained by the hydrocarbon detecting means may hinder exhaust gas purification by the NOx storage reduction catalyst,
If the operation is performed before the rich spike execution, the rich spike execution can be prohibited even if the rich spike condition is satisfied, so that the surface of the catalyst is not thickly covered with hydrocarbons and a large amount of unpurified hydrocarbons are present. It is not released downstream of the NOx storage reduction catalyst. Moreover, in lean combustion or stratified charge combustion, the NOx concentration is relatively low, and even if the exhaust gas is in a lean atmosphere, the stored NOx is not discharged. In this manner, deterioration of exhaust emission due to the inhibition of the catalytic reaction of the NOx storage reduction catalyst by the hydrocarbon can be suppressed, and fuel waste can be prevented.

Further, when the rich spike prohibiting means makes the above determination during the execution of the rich spike, the rich spike is immediately stopped. At this time, the catalyst surface is beginning to be covered with hydrocarbons because the rich spike has already been done halfway, but to the extent of the problem, the catalyst surface is not covered with hydrocarbons and exhaust purification will not be hindered. . Since the exhaust gas is temporarily made rich, N
Part of the stored NOx is released from the Ox storage reduction catalyst. However, since the catalytic action is sufficient, the hydrocarbons present on the catalyst surface are oxidized by the released NOx and converted into carbon dioxide gas and water for purification, and further NOx itself is deprived of oxygen and reduced to nitrogen gas for purification. To be done. In this manner, deterioration of exhaust emission due to the inhibition of the catalytic reaction of the NOx storage reduction catalyst by the hydrocarbon can be suppressed, and fuel waste can be prevented.

An exhaust gas purification apparatus for an internal combustion engine according to a tenth aspect of the present invention obtains a NOx storage amount in a NOx storage reduction catalyst provided in an exhaust system of the internal combustion engine, and when the NOx storage amount reaches a reference value, carbonization is performed. By executing a rich spike in which a reducing component containing hydrogen is supplied by exhaust, the NO
An exhaust gas purification device for an internal combustion engine that reduces NOx stored in an x storage reduction catalyst, wherein the hydrocarbon detection means determines the amount of hydrocarbons flowing into the NOx storage reduction catalyst and the hydrocarbon detection means. Depending on the inflowing hydrocarbon amount,
When there is a risk that NOx purification in the NOx occlusion reduction catalyst may be hindered, rich spike prohibition means for prohibiting or stopping the execution of the rich spike in advance is provided.

The rich spike prohibiting means prohibits execution of the rich spike in advance or stops midway when the inflowing hydrocarbon amount obtained by the hydrocarbon detecting means may interfere with NOx purification in the NOx storage reduction catalyst. is doing. For this reason, the surface of the catalyst is not thickly covered with hydrocarbons to the extent of a problem, which prevents the situation where NOx purification is hindered.

By the operation as described in claim 9, carbonization is performed regardless of whether the determination by the rich spike prohibiting means is made before the rich spike execution or during the rich spike execution. It is possible to suppress the deterioration of exhaust emission due to the inhibition of the catalytic reaction of the NOx storage reduction catalyst by hydrogen and prevent the fuel waste.

According to an eleventh aspect of the present invention, there is provided an exhaust gas purification apparatus for an internal combustion engine, wherein an NOx storage amount in a NOx storage reduction catalyst provided in an exhaust system of the internal combustion engine is calculated, and when the NOx storage amount reaches a reference value, carbonization is performed. By executing a rich spike in which a reducing component containing hydrogen is supplied by exhaust, the NO
An exhaust gas purification apparatus for an internal combustion engine that reduces NOx stored in an x storage reduction catalyst, wherein the hydrocarbon detection means determines the amount of hydrocarbons flowing into the NOx storage reduction catalyst, and the inflow obtained by the hydrocarbon detection means. When the amount of hydrocarbons exceeds the ability of the NOx occlusion reduction catalyst to purify hydrocarbons, rich spike prohibiting means for prohibiting or stopping the execution of the rich spike in advance is provided.

The rich spike prohibiting means prohibits the execution of the rich spike in advance or stops the midway when the inflowing hydrocarbon amount obtained by the hydrocarbon detecting means exceeds the hydrocarbon purification capacity of the NOx storage reduction catalyst. ing. For this reason, the surface of the catalyst is not thickly covered with hydrocarbons to the extent that it becomes a problem, which prevents purification from being hindered.

By the operation as described in claim 9, carbonization is performed regardless of whether the determination by the rich spike prohibiting means is performed before the rich spike execution or during the rich spike execution. It is possible to suppress the deterioration of exhaust emission due to the inhibition of the catalytic reaction of the NOx storage reduction catalyst by hydrogen and prevent the fuel waste.

According to a twelfth aspect of the present invention, there is provided an exhaust gas purification apparatus for an internal combustion engine, wherein an NOx storage amount in a NOx storage reduction catalyst provided in an exhaust system of the internal combustion engine is calculated, and when the NOx storage amount reaches a reference value, carbonization is performed. By executing a rich spike in which a reducing component containing hydrogen is supplied by exhaust, the NO
An exhaust gas purification apparatus for an internal combustion engine that reduces NOx stored in an x storage reduction catalyst, wherein the hydrocarbon detection means determines the concentration of hydrocarbons flowing into the NOx storage reduction catalyst, and the inflow obtained by the hydrocarbon detection means. When the hydrocarbon concentration exceeds the hydrocarbon purification capacity of the NOx storage reduction catalyst, the rich spike prohibiting means for prohibiting or stopping the execution of the rich spike in advance is provided.

As described above, the rich spike inhibiting means has the inflowing hydrocarbon concentration N determined by the hydrocarbon detecting means.
If the amount of hydrocarbons purified by the NOx storage reduction catalyst exceeds the amount of hydrocarbons purified by the Ox storage reduction catalyst, the rich spike is prohibited in advance because the amount of hydrocarbons purified by the NOx storage reduction catalyst cannot keep up with the amount of hydrocarbons flowing into the NOx storage reduction catalyst. Or stop halfway.

As a result, by the operation as described in claim 9, both when the determination by the rich spike prohibiting means is performed before the rich spike execution and when it is performed during the rich spike execution. As a result, it is possible to suppress the deterioration of exhaust emission due to the inhibition of the catalytic reaction of the NOx storage reduction catalyst by the hydrocarbons and prevent the fuel waste.

An exhaust purification system for an internal combustion engine according to a thirteenth aspect of the present invention obtains the NOx storage amount in a NOx storage reduction catalyst provided in the exhaust system of the internal combustion engine, and when the NOx storage amount reaches a reference value, carbonization is performed. By executing a rich spike in which a reducing component containing hydrogen is supplied by exhaust, the NO
An exhaust gas purification apparatus for an internal combustion engine for reducing NOx stored in an x storage reduction catalyst, comprising: a hydrocarbon detection means for determining a hydrocarbon flow rate per unit time flowing into the NOx storage reduction catalyst; and a hydrocarbon detection means. When the obtained hydrocarbon flow rate per unit time exceeds the hydrocarbon purification capacity of the NOx storage reduction catalyst, the rich spike prohibiting means for prohibiting the execution of the rich spike in advance or stopping the rich spike in the middle is provided. Is characterized by.

As described above, the rich spike prohibiting means purifies the NOx storage reduction catalyst when the hydrocarbon flow rate per unit time obtained by the hydrocarbon detection means exceeds the hydrocarbon purification capacity of the NOx storage reduction catalyst. Assuming that the amount of hydrocarbons generated does not catch up with the amount of hydrocarbons flowing into the NOx storage reduction catalyst, the execution of the rich spike is prohibited or stopped midway.

As a result, due to the operation as described in claim 9, both when the determination by the rich spike prohibiting means is performed before the rich spike execution and when it is performed during the rich spike execution. As a result, it is possible to suppress the deterioration of exhaust emission due to the inhibition of the catalytic reaction of the NOx storage reduction catalyst by the hydrocarbons and prevent the fuel waste.

In the exhaust gas purifying apparatus for an internal combustion engine according to claim 14, in any one of claims 9 to 13, the rich spike prohibiting means preliminarily prohibits the execution of the rich spike or stops the processing during the idling. It is characterized by not performing other than.

Normally, the problem that the inhibition of the catalytic reaction of the NOx storage reduction catalyst due to the thick coating of the surface of the catalyst by the hydrocarbon becomes a problem at the time of idling at a low load and at a low rotation speed. It can be said that nothing happens. Therefore, as described above, the rich spike prohibiting means may not perform the process of prohibiting the execution of the rich spike in advance or stopping it in the middle except during the idling time.
As a result, the rich spike prohibiting means does not need to perform unnecessary judgment processing.

According to a fifteenth aspect of the present invention, in the exhaust gas purifying apparatus for an internal combustion engine according to any one of the ninth to fourteenth aspects, the exhaust catalyst of the internal combustion engine has a start catalyst having an oxygen storage function upstream of the NOx storage reduction catalyst. And a start catalyst purification capacity detection means for determining the degree of purification of hydrocarbons by the start catalyst, wherein the hydrocarbon detection means is based on the start catalyst determined by the start catalyst purification capacity detection means. It is characterized in that the amount of hydrocarbons flowing into the NOx storage reduction catalyst, the concentration of hydrocarbons, or the flow rate of hydrocarbons per unit time is determined in consideration of the degree of purification of hydrocarbons.

The start catalyst described above is
When the Ox storage reduction catalyst is arranged upstream of the exhaust system, the amount of hydrocarbons flowing into the NOx storage reduction catalyst,
The hydrocarbon concentration or the hydrocarbon flow rate per unit time is influenced by the degree of purification of hydrocarbons by the start catalyst.

Therefore, the hydrocarbon detection means considers the degree of purification of hydrocarbons by the start catalyst determined by the start catalyst purification capacity detection means and considers N.
The amount of hydrocarbons flowing into the Ox storage reduction catalyst, the concentration of hydrocarbons, or the flow rate of hydrocarbons per unit time is calculated.
Therefore, the rich spike prohibiting means can accurately determine the amount of hydrocarbons, the concentration of hydrocarbons, and the flow rate of hydrocarbons per unit time.
x Deterioration of exhaust emission due to inhibition of catalytic reaction of the occlusion reduction catalyst can be appropriately suppressed, and fuel waste can be appropriately prevented.

According to a sixteenth aspect of the present invention, there is provided the exhaust gas purification device for an internal combustion engine according to any one of the ninth to fourteenth aspects, wherein the hydrocarbon detecting means is a hydrocarbon amount in the exhaust gas discharged from the combustion chamber of the internal combustion engine, or a carbonization amount. It is characterized in that the hydrogen concentration or the hydrocarbon flow rate per unit time is obtained.

The hydrocarbon affecting the NOx storage reduction catalyst in this way may be obtained as the amount of hydrocarbons in the exhaust gas discharged from the combustion chamber of the internal combustion engine, the hydrocarbon concentration, or the hydrocarbon flow rate per unit time.

According to a seventeenth aspect of the present invention, in the exhaust gas purifying apparatus for an internal combustion engine according to the sixteenth aspect, a start catalyst having an oxygen storage function is arranged upstream of the NOx storage reduction catalyst in the exhaust system of the internal combustion engine. A start catalyst purifying ability detecting means for determining the degree of purification of hydrocarbons by the start catalyst, wherein the rich spike inhibiting means is provided in the exhaust gas discharged from the combustion chamber of the internal combustion engine obtained by the hydrocarbon detecting means. Whether or not the amount of hydrocarbons, the concentration of hydrocarbons, or the flow rate of hydrocarbons per unit time hinders the purification of the NOx storage reduction catalyst or exceeds the purification ability was determined by the start catalyst purification ability detection means. Characterized by a judgment considering the degree of purification of hydrocarbons by the start catalyst To.

When there is a start catalyst, the amount of hydrocarbons discharged from the combustion chamber of the internal combustion engine, the hydrocarbon concentration, or the hydrocarbon flow rate per unit time, which is obtained by the hydrocarbon detection means, When the rich spike inhibiting means determines whether or not the purification of the NOx storage reduction catalyst is hindered or exceeds the purification capacity, the purification of hydrocarbons by the start catalyst determined by the start catalyst purification capacity detection means The degree may be considered. As a result, the rich spike inhibiting means can accurately determine the influence of the amount of hydrocarbons, the concentration of hydrocarbons, and the flow rate of hydrocarbons per unit time on the catalyst, so that the inhibition of the catalytic reaction of the NOx storage reduction catalyst by the hydrocarbons can be prevented. It is possible to appropriately suppress the deterioration of the exhaust emission due to it and appropriately prevent the fuel waste.

According to the eighteenth aspect of the present invention, there is provided the exhaust gas purification device for an internal combustion engine according to the fifteenth or seventeenth aspects, wherein the start catalyst purification performance detecting means is an air-fuel ratio detected from an exhaust gas component upstream of the start catalyst. The degree of purification of hydrocarbons by the start catalyst is obtained based on the bed temperature of the start catalyst.

As described above, the air-fuel ratio detected from the exhaust gas component upstream of the start catalyst and the bed temperature of the start catalyst are related to the degree of purification of hydrocarbons by the start catalyst. Therefore, the start catalyst purification capacity detecting means determines the degree of purification of hydrocarbons by the start catalyst based on the air-fuel ratio detected from the exhaust component upstream of the start catalyst and the bed temperature of the start catalyst. The rich spike inhibiting means can accurately determine the amount of hydrocarbons flowing into the NOx storage reduction catalyst, the hydrocarbon concentration, or the flow rate of hydrocarbons per unit time. Therefore, it is possible to appropriately suppress the deterioration of the exhaust emission due to the inhibition of the catalytic reaction of the NOx storage reduction catalyst by the hydrocarbon, and it is possible to appropriately prevent the fuel waste.

[0057]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [Embodiment 1] FIG. 1 shows a cylinder injection type gasoline engine (hereinafter abbreviated as "engine") 2 mounted on a vehicle and its electronic control unit (hereinafter "E").
(Hereinafter referred to as "CU") 4. Engine 2
Each cylinder has a fuel injection valve 6 for directly injecting fuel into the combustion chamber, and a spark plug 8 for igniting the injected fuel.
And are provided respectively. A throttle valve 12 whose opening is adjusted by a motor is provided in the middle of an intake path 10 connected to the combustion chamber via an intake valve (not shown). The intake air amount GA (mg / sec) supplied to each cylinder is adjusted by the opening of the throttle valve 12 (throttle opening TA). Throttle opening T
A is detected by the throttle opening sensor 14, the intake air amount GA is detected by the intake air amount sensor 16, and E
It is read in CU4.

A start catalyst 20 is provided on the upstream side and a NOx storage reduction catalyst 22 is provided on the downstream side in the middle of the exhaust path 18 connected to the combustion chamber via an exhaust valve (not shown). An air-fuel ratio sensor 24 that detects the air-fuel ratio from the exhaust component is provided upstream of the start catalyst 20, and a first oxygen sensor that detects oxygen in the exhaust component is provided between the start catalyst 20 and the NOx storage reduction catalyst 22. 26
However, a second oxygen sensor 28 that detects oxygen in the exhaust gas component is provided downstream of the NOx storage reduction catalyst 22.

The ECU 4 is an engine control circuit mainly composed of a digital computer. This EC
U4 is a throttle opening sensor 14, an intake air amount sensor 16, an air-fuel ratio sensor 24, two oxygen sensors 26, 28.
Other than the above, an accelerator opening sensor 32 that detects the amount of depression of the accelerator pedal 30 (accelerator opening ACCP), an engine speed sensor 34 that detects an engine speed NE from the rotation of a crankshaft (not shown), and a cooling of the engine 2. Signals are input from the cooling water temperature sensor 36 and the like that detect the water temperature THW. In addition to such sensors,
Although not shown, a sensor such as a vehicle speed sensor necessary for engine control is provided.

The ECU 4 appropriately controls the fuel injection timing of the engine 2, the fuel injection amount, the ignition timing, the throttle opening TA, etc., based on the contents detected by the various sensors described above. As a result, for example, the combustion mode is switched between stratified combustion and homogeneous combustion according to the operating state. In the first embodiment, the combustion mode is determined on the basis of the map of the engine speed NE and the load factor eklq during normal operation excluding the cold state. Here, the load factor eklq is a value obtained from a map having the accelerator opening ACCP and the engine speed NE as parameters, for example, as a ratio of the current load to the maximum engine load.

Next, in the present embodiment, the rich spike prohibition process of the processes related to the exhaust gas purification management for the NOx storage reduction catalyst 22 executed by the ECU 4 will be described. FIG. 2 shows the rich spike prohibition processing.
This process is a process that is repeatedly executed at regular time intervals.

When this process is started, it is first determined whether the engine 2 is in stratified combustion (S110). If it is not during the stratified charge combustion (“NO” in S110), that is, if the homogeneous combustion is performed at the stoichiometric air-fuel ratio (including the case of temporarily making the rich state), the rich spike is permitted (S118). ). That is, N of the NOx storage reduction catalyst 22
When the Ox storage amount reaches the NOx storage capacity, the rich spike is executed as usual, and fuel is injected from the fuel injection valve 6 into the combustion chamber at a stoichiometric air-fuel ratio or in a rich state. Exhaust corresponding to NOx
It is supplied to the storage reduction catalyst 22. As a result, the NOx stored in the NOx storage reduction catalyst 22 is released and reduced. However, step S
In the state determined to be “NO” in 110, since the combustion is already performed at the stoichiometric air-fuel ratio, the NOx occlusion amount in the NOx occlusion reduction catalyst 22 is decreasing or is almost absent. Is. In this way, this processing is once terminated.

If the engine 2 is in stratified charge combustion (S11
If "0" is "YES"), then it is determined whether the current engine 2 is idle (S112). Normally, when the surface of the NOx storage reduction catalyst 22 is thickly covered with HC, NO
x Inhibition of the catalytic reaction of the occlusion reduction catalyst becomes a problem during idling at low load and low rotation, so if it is determined that the engine is not idling (“NO” in S112), rich spike is permitted. (S118), this process is once terminated.

If the vehicle is idle ("YES" in S112)
S ”), and then the value of the HC concentration thccl flowing into the NOx storage reduction catalyst 22 is read (S114). This NO
As the inflow HC concentration thccl of the x storage reduction catalyst 22, the value obtained by the inflow HC concentration thccl calculation process (FIG. 4) of the NOx storage reduction catalyst described later is read.

Next, it is judged whether the inflowing HC concentration thccl is larger than the excessive concentration judgment value thmax (S11).
6). If thccl ≦ thmax (“NO” in S116), rich spike is permitted (S11).
8).

However, if thccl> thmax (“YES” in S116), rich spike is prohibited (S120). When the rich spike is prohibited, the rich spike is not executed even if the rich spike condition is satisfied, that is, the NOx storage amount of the NOx storage reduction catalyst 22 reaches the NOx storage capacity. Alternatively, when the rich spike is in the middle, the rich spike is stopped. Therefore, the exhaust gas maintains the lean state or returns to the lean state.

In the case of the present embodiment, the excess concentration judgment value t
hmax is set as follows. That is, as shown in the graph of FIG. 3, when the inflowing HC concentration thccl into the NOx storage reduction catalyst 22 is 5000 ppm or less, the NOx reduction rate during rich is 100% and NOx is completely purified. However, the inflowing HC concentration thccl is 500
It decreases when it exceeds 0 ppm, and NO at about 6000 ppm
The x reduction rate is 0%. And the inflowing HC concentration thc
When cl increases, the amount of NOx that has been stored is added, and N that is discharged downstream from the NOx storage reduction catalyst 22.
The amount of Ox increases. Therefore, in order to reliably reduce and purify NOx, the excess concentration determination value thmax is 5
Set to a value of 000 ppm or less. The excess concentration determination value thmax = 5000 ppm is set here.

Next, the inflow HC concentration t of the NOx storage reduction catalyst
The hccl calculation process (FIG. 4) will be described. This process is repeatedly executed at regular time intervals. When this processing is started, first, the load factor eklq is calculated using the map Mthcin.
Then, the HC concentration thcin on the inflow side of the start catalyst is calculated based on the engine speed NE (S210). This map Mthcin has a load factor ekl obtained by an experiment in advance.
This is set by obtaining the HC concentration in the exhaust gas discharged from the combustion chamber of the engine 2 using q and the engine speed NE as parameters.

Next, the air-fuel ratio AFsc on the inflow side of the start catalyst 20 is detected from the output of the air-fuel ratio sensor 24 (S212). Then, the bed temperature esctempave of the start catalyst 20 is detected (S214). Floor temperature esctempave of this start catalyst 20
Is estimated from the engine speed NE and the intake air amount GA by a floor temperature estimation process separately performed by the ECU 4. In this bed temperature estimation process, for example, the catalyst bed temperature can be estimated as the exhaust temperature obtained from the engine speed NE and the intake air amount GA during stable operation of the engine 2. When the engine 2 is in transition, the bed temperature esctempave is calculated by repeating and calculating the catalyst bed temperature so as to follow the exhaust temperature based on the time constant of the intake air amount GA. Instead of making such an estimation, a temperature sensor may be provided in the start catalyst 20 to directly measure the bed temperature.

Next, the HC purification rate redhc (%) of the start catalyst 20 is obtained from the map Mredhc based on the inflow side air-fuel ratio AFsc of the start catalyst 20 and the bed temperature esctempave of the start catalyst 20 (S216). ). This map Mred
hc is the air-fuel ratio AFsc and the bed temperature es obtained by an experiment in advance.
This is set by detecting the purification state due to the oxidation of HC in the start catalyst 20 using ctempave as a parameter.

Next, as shown in the following equation 1, the HC concentration thccl on the inflow side of the NOx storage reduction catalyst 22 is calculated (S218).

[0072]

[Equation 1]     thccl ← thcin x redhc / 100 [Equation 1] In this way, this processing is once terminated.

The start catalyst inflow side HC concentration thccl thus repeatedly calculated is read in step S114 of the rich spike prohibition processing (FIG. 2) to determine whether rich spike is permitted or prohibited.

In the above-described structure, the process for calculating the inflowing HC concentration thccl of the NOx storage reduction catalyst (FIG. 4) is the process as the hydrocarbon detecting means, and the rich spike inhibiting process (FIG. 2) is the process as the rich spike inhibiting means. , N
Steps S212 to S216 of the inflow HC concentration thccl calculation process (FIG. 4) of the Ox storage reduction catalyst correspond to the process as the start catalyst purification capacity detection means.

According to the first embodiment described above, the following effects can be obtained. (I). Thcc in rich spike prohibition process (Fig. 2)
If it is determined that l> thmax (“YE” in S116).
S ”), purification of HC by the NOx storage reduction catalyst 22
Do not catch up with the HC flowing into the NOx storage reduction catalyst 22,
It indicates that NOx purification may be hindered. Therefore, by executing the rich spike prohibition in step S120, the execution of the rich spike is prohibited in advance or stopped midway. For this reason, it is possible to prevent the situation where the surface of the NOx storage reduction catalyst 22, particularly the catalyst surface of Pt or the like, is thickly covered with HC to the extent of a problem.

When the rich spike prohibition (S120) is performed before the rich spike execution, the rich spike execution is prohibited even if the rich spike condition is satisfied. Therefore, the surface of the catalyst such as Pt is not thickly covered with HC, and a large amount of HC is stored in the NOx storage reduction catalyst 22.
Will not be released downstream. Moreover, NO in stratified combustion
Since the x concentration is relatively low and the exhaust gas is in a lean atmosphere, the NOx stored in the NOx storage reduction catalyst 22 is reduced.
Is not discharged. In this way, it is possible to suppress the deterioration of exhaust emission due to the inhibition of the catalytic reaction of the NOx storage reduction catalyst 22 due to HC, and to prevent the fuel waste.

When the rich spike inhibition (S120) is performed during the execution of the rich spike, the rich spike is immediately stopped. At this time, since the rich spike has already been done halfway, the catalyst surface such as Pt is beginning to be covered with HC, but the catalyst surface is not covered with HC to the extent of a problem. For this reason, the exhaust gas temporarily becomes rich atmosphere, and the stored NOx is partially released from the NOx storage reduction catalyst 22. However, since the catalytic action is sufficient, Pt is released by the released NOx.
HC existing on the catalyst surface is oxidized and converted into carbon dioxide gas and water for purification, and NOx itself is deprived of oxygen and reduced to nitrogen gas for purification. In this way, it is possible to suppress the deterioration of exhaust emission due to the inhibition of the catalytic reaction of the NOx storage reduction catalyst 22 due to HC, and to prevent the fuel waste.

(B). Normally, the catalyst surface such as Pt is HC
It can be said that such a situation does not occur in other operating states when the NOx storage reduction catalyst 22 has a problem of inhibiting the catalytic reaction of the NOx storage reduction catalyst 22 when it is idling at low load and low rotation. Therefore, in the rich spike prohibition process (FIG. 2), except during idle time (“NO” in S112),
Rich spike permission (S118) is set. As a result, it is not necessary to read (S114) or determine (S116) the inflowing HC concentration thccl of the NOx storage reduction catalyst, and the burden on the ECU 4 is reduced, so that an inexpensive IC or the like can be used.

Further, when it is not during the stratified charge combustion (“NO” in S110), that is, because the combustion is performed at the stoichiometric air-fuel ratio during the homogeneous combustion, the NOx storage amount in the NOx storage reduction catalyst 22 decreases. Since it can be determined that there is, or hardly exists, the process is shifted to the rich spike permission (S118) side. As a result, the inflow HC concentration of the NOx occlusion reduction catalyst is further thccl.
(S114) and determination (S116) need not be executed, the load on the ECU 4 is further reduced, and a cheaper IC or the like can be used.

(C). Start catalystist 20 is NO
It is arranged on the upstream side of the x storage reduction catalyst 22. Therefore, the concentration of HC flowing into the NOx storage reduction catalyst 22 is influenced by the degree of purification of HC by the start catalyst 20. Therefore, the inflow HC concentration th of the NOx storage reduction catalyst
In the ccl calculation process (FIG. 4), the start catalyst 2
By obtaining the HC purification rate redhc of 0 (S212-
S216), the inflowing HC concentration t of the NOx storage reduction catalyst in consideration of the degree of purification of HC by the start catalyst 20
Hccl is calculated (S218). Therefore, in step S116 of the rich spike inhibition process (FIG. 2), NOx is generated.
Since the HC concentration flowing into the storage reduction catalyst 22 can be accurately determined, the NOx storage reduction catalyst 22 due to HC
It is possible to appropriately suppress the deterioration of exhaust emission due to the inhibition of the catalytic reaction, and appropriately prevent fuel waste.

[Second Embodiment] In the system configuration of the present embodiment, as shown in FIG. 5, only the NOx storage reduction catalyst 22 is arranged in the exhaust passage 18 as an exhaust purification catalyst, and the start catalyst is not arranged. . Then, in place of FIG. 4, the inflowing HC concentration t of the NOx storage reduction catalyst shown in FIG.
The hccl calculation process is executed. The other structure is the same as that of the first embodiment.

Inflow HC concentration of NOx occlusion reduction catalyst thc
The cl calculation process (FIG. 6) will be described. When this process starts, the same map Mth as in step S210 of FIG.
The load factor eklq and the engine speed NE are determined by cin.
The HC concentration of the exhaust component discharged from the combustion chamber of the engine 2 is calculated based on the above, and is set as the inflow HC concentration thccl of the NOx storage reduction catalyst (S211). In this way, this processing is once terminated.

The inflowing HC concentration thccl calculation process (FIG. 6) of the NOx storage reduction catalyst described above corresponds to the process as the hydrocarbon detecting means. According to the second embodiment described above, the following effects can be obtained.

(A). The effects (i) and (ii) of the first embodiment are produced. [Third Embodiment] In the present embodiment, the rich spike prohibition process shown in FIG. 7 is executed instead of the rich spike prohibition process (FIG. 2) and the inflow HC concentration thccl calculation process of the NOx storage reduction catalyst (FIG. 4). To be done. Incidentally, step S1
In 10, S112, S118, and S120, the same processing as the processing of the same sign described in the rich spike prohibition processing (FIG. 2) of the first embodiment is performed. The other structure is the same as that of the first embodiment.

When the rich spike prohibiting process (FIG. 7) is started, first, the determinations in steps S110 and S112 are made. If "NO" is determined in either step S110 or step S112, rich spike permission (S118) is executed.

On the other hand, if stratified charge combustion and idling (“YES” in S110 and S112), then the map M
From mhcext, the HC flow rate mhcext (mg / sec) discharged by the engine 2 is obtained based on the load factor eklq, the engine speed NE, and the intake air amount GA (S113). This map Mmhcext is set by previously obtaining the flow rate (mg / sec) of HC discharged from the combustion chamber of the engine 2 by experiments using the load factor eklq, the engine speed NE and the intake air amount GA as parameters.

Next, the purification capacity mscmax (mg / sec) of the start catalyst 20 is calculated (S11).
5). The purification capacity mscmax is represented by the flow rate (mg / sec) of HC that can be purified by the start catalyst 20.

The purification capacity mscmax of the start catalyst 20 is obtained by a separate start catalyst purification capacity mscmax calculation process. For example, the inflowing HC concentration thc of the NOx storage reduction catalyst
The air-fuel ratio AFsc on the inflow side of the start catalyst 20 determined in step S212 of the cl calculation process (FIG. 4), the floor temperature esctempave of the start catalyst 20 determined in step S214, and the intake air amount GA (mg
/ Sec) based on the map. This map shows the air-fuel ratio AFsc on the inlet side and the bed temperature esctempa.
It is set in advance by an experiment using ve and the intake air amount GA as parameters.

Next, the following expression 2 is judged (S117).

[0090]

Mhext> mhmax + mscmax [Equation 2] Here, mhmax is the purifying capacity (mg / sec) of the NOx storage reduction catalyst 22, and the purifiable flow rate of HC (mg
/ Sec). The NOx storage reduction catalyst purification capacity mhmax is calculated from a map based on the excess concentration determination value thmax and the intake air amount GA used in step S116 of the first embodiment, for example.

The right side of the equation 2 is the start catalyst 2
0 represents the HC purification capacity in cooperation with the NOx storage reduction catalyst 22. Therefore, when the above equation 2 is satisfied (“YES” in S117), the HC flow rate mhcext from the engine 2 is determined by the start catalyst 20 and the NOx storage reduction catalyst 22 in cooperation with the HC purification capacity (mhma).
x + mscmax) is exceeded, rich spike is prohibited (S120).

On the other hand, "mhcext≤mhmax + ms
If “cmax” (“NO” in S117), rich spike permission (S118) is executed. In the above-described configuration, the rich spike prohibition process (FIG. 7) corresponds to the process as the rich spike prohibition means, the step S113 corresponds to the process as the hydrocarbon detection means, and the step S115 corresponds to the process as the start catalyst purification capacity detection means. To do.

According to the third embodiment described above, the following effects can be obtained. (I). In the rich spike prohibition process (Fig. 7), "mhc
If it is determined that “ext> mhmax + mscmax” (“YES” in S117), start catalyst list 2
It is shown that the HC purification of the NOx storage reduction catalyst 22 judged in consideration of the HC purification capacity of 0 cannot catch up with the HC flowing into the NOx storage reduction catalyst 22. Therefore, by executing the rich spike prohibition in step S120, the execution of the rich spike is prohibited in advance or stopped midway. For this reason, it is possible to prevent the situation where the surface of the NOx storage reduction catalyst 22, particularly the catalyst surface of Pt or the like, is thickly covered with HC to the extent of a problem.

As a result, as described in (A) of the first embodiment, the rich spike inhibition (S12
0) is performed before the execution of the rich spike and when it is performed during the execution of the rich spike.
It is possible to suppress the deterioration of the exhaust emission due to the inhibition of the catalytic reaction of the NOx storage reduction catalyst 22 due to C, and prevent the fuel waste.

(B). Rich spike prohibition processing (Fig. 7)
Then, the NOx storage reduction catalyst 2 is obtained in consideration of the degree of purification of HC by the start catalyst 20 by obtaining the start catalyst purification capacity mscmax (S115).
It is determined whether the HC flowing into 2 can be purified by the NOx storage reduction catalyst 22 (S117). Therefore N
Since it is possible to accurately determine whether or not purification can be performed by the Ox storage reduction catalyst 22, deterioration of exhaust emission due to the inhibition of the catalytic reaction of the NOx storage reduction catalyst 22 due to HC can be appropriately suppressed, and fuel waste can be appropriately prevented. can do.

(C). The same effect as (b) of the first embodiment is produced. [Other Embodiments] (a). In the first and second embodiments, the concentration thccl of HC flowing into the NOx storage reduction catalyst 22 is obtained and compared with the excess concentration determination value thmax to determine whether rich spike inhibition or permission is permitted. The flow rate of inflowing HC may be obtained and compared with the flow rate determination value to determine whether rich spike prohibition or permission is permitted.

(B). In the third embodiment, whether the HC flow rate discharged from the engine 2 is a flow rate which causes a problem in the NOx storage reduction catalyst 22 or not, considering the degree of HC purification by the start catalyst 20, prohibits rich spike. Although it is determined whether or not to permit, rich spike prohibition or permission is to be performed in consideration of the degree of HC purification by the start catalyst 20 as to whether or not the HC concentration discharged from the engine 2 is a concentration that causes a problem in the NOx storage reduction catalyst 22. You may judge whether.

(C). In each of the above-described embodiments, the in-cylinder injection type engine is used, but it is also applicable to a port injection type engine that injects fuel into the intake port. In the case of this configuration, lean combustion is performed instead of stratified combustion, and during this lean combustion, NOx is stored in the NOx storage reduction catalyst.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an engine and an ECU according to a first embodiment.

FIG. 2 is a flowchart of rich spike prohibition processing executed by the ECU of the first embodiment.

FIG. 3 is a graph showing the relationship between the rich NOx reduction rate and the inflowing HC concentration in the NOx occlusion reduction catalyst.

FIG. 4 is a flowchart of an inflow HC concentration thccl calculation process of the NOx storage reduction catalyst executed by the ECU of the first embodiment.

FIG. 5 is a schematic configuration diagram of an engine and an ECU according to a second embodiment.

FIG. 6 is a flowchart of an inflow HC concentration thccl calculation process of the NOx storage reduction catalyst executed by the ECU of the second embodiment.

FIG. 7 is a flowchart of rich spike prohibition processing executed by the ECU of the third embodiment.

[Explanation of symbols]

2 ... Engine, 4 ... ECU, 6 ... Fuel injection valve, 8 ...
Spark plug, 10 ... Intake path, 12 ... Throttle valve, 14 ... Throttle opening sensor, 16 ... Intake air amount sensor, 18 ... Exhaust path, 20 ... Start catalyst,
22 ... NOx storage reduction catalyst, 24 ... Air-fuel ratio sensor, 26
... 1st oxygen sensor, 28 ... 2nd oxygen sensor, 30 ... Accelerator pedal, 32 ... Accelerator opening sensor, 34 ... Engine speed sensor, 36 ... Cooling water temperature sensor.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) F01N 3/24 F01N 3/28 301C 3/28 301 F02D 41/04 305A F02D 41/04 305 41/08 305 41/08 305 45/00 314R 45/00 314 314Z B01D 53/36 103B 101B F term (reference) 3G084 AA03 AA04 BA09 BA13 BA17 BA24 CA03 DA10 FA07 FA10 FA26 FA28 FA29 FA30 FA33 3G091 AA02 AA12 AA24 A01 BA03 BA06 AB06 AB03 AB06 AB06 AB06 AB06 AB06 AB06 BA15 CB02 CB05 CB07 DA08 DA10 DB10 EA01 EA03 EA05 EA07 EA08 EA10 EA16 EA17 EA18 EA33 EA34 FA12 FB05 FB09 HA08 HA36 HA37 3G301 HA01 HA04 HA06 HA15 JA25 JA26 JA02 PA08 PD08P12A08ZZP12A08ZZP12A08PZP12A01P12Z0P12PZP12P12Z0P12P0Z0P12P0Z0P0P0Z0P0Z0P0Z0P0Z0P0Z0P0Z0P0Z0P0Z0P0Z0P0Z0P0Z0Z0P0Z0P0Z0Z0Z0Z0Z0Z0Z0Z0Z0Z0Z0P0Z0Z0Z0Z0Z0Z025Z0Z025 AB05 AB07 AC02 CC32 CC44 DA01 DA02 DA03 DA08 DA09 DA10 DA13 DA20 EA04

Claims (18)

[Claims] 1. A method for purifying exhaust gas of an internal combustion engine, wherein when reducing NOx stored in a NOx storage reduction catalyst provided in an exhaust system of the internal combustion engine, a rich spike for supplying a reducing component containing hydrocarbon by exhaust gas is executed. The exhaust gas purification in the NOx occlusion reduction catalyst is the NOx
An exhaust gas purification method for an internal combustion engine, wherein the execution of the rich spike is prohibited in advance or stopped midway when it is determined that there is a possibility that the hydrocarbon will flow into the storage reduction catalyst. 2. A method for purifying exhaust gas of an internal combustion engine, wherein when reducing NOx stored in a NOx storage reduction catalyst provided in an exhaust system of the internal combustion engine, a rich spike for supplying a reducing component containing hydrocarbon by exhaust gas is executed. The NOx purification in the NOx storage reduction catalyst is the NOx
x Exhaust gas purification method for an internal combustion engine, wherein the execution of the rich spike is prohibited or stopped midway when it is determined that the hydrocarbon may flow into the storage reduction catalyst. 3. An exhaust gas purification method for an internal combustion engine, which performs a rich spike for supplying a reducing component containing hydrocarbon by exhaust gas when reducing NOx stored in a NOx storage reduction catalyst provided in an exhaust system of the internal combustion engine. When it is determined that the hydrocarbon purification capacity of the NOx storage reduction catalyst cannot process the hydrocarbons flowing into the NOx storage reduction catalyst, execution of the rich spike is prohibited or stopped midway. An exhaust gas purification method for an internal combustion engine, comprising: 4. A method for purifying exhaust gas of an internal combustion engine, wherein when reducing NOx stored in a NOx storage reduction catalyst provided in an exhaust system of the internal combustion engine, a rich spike for supplying a reducing component containing hydrocarbon by exhaust gas is executed. An exhaust gas purification method for an internal combustion engine, wherein when the hydrocarbon concentration flowing into the NOx storage reduction catalyst is higher than an excess concentration determination value, execution of the rich spike is prohibited or stopped midway. 5. An exhaust gas purification method for an internal combustion engine, which performs a rich spike for supplying a reducing component containing hydrocarbon by exhaust gas when reducing NOx stored in a NOx storage reduction catalyst provided in an exhaust system of the internal combustion engine. When the flow rate of hydrocarbons flowing into the NOx storage reduction catalyst per unit time is larger than the excess flow rate determination value, execution of the rich spike is prohibited in advance or stopped midway. Exhaust purification method. 6. An exhaust gas purification method for an internal combustion engine according to any one of claims 1 to 5, wherein the process of prohibiting execution of the rich spike or stopping the rich spike in advance is not performed except during idling. 7. The N according to any one of claims 1 to 6.
A start catalyst having an oxygen storage function is arranged upstream of the exhaust system of the Ox storage reduction catalyst, and the NOx is considered in consideration of the degree of purification of hydrocarbons by the start catalyst.
An exhaust gas purification method for an internal combustion engine, comprising: determining the amount of hydrocarbons flowing into the storage reduction catalyst, the concentration of hydrocarbons, or the flow rate of hydrocarbons per unit time. 8. The air-fuel ratio detected from the exhaust gas component upstream of the start catalyst according to claim 7,
An exhaust gas purification method for an internal combustion engine, comprising: determining a degree of purification of hydrocarbons by the start catalyst based on a bed temperature of the start catalyst. 9. A rich NOx storage / reduction catalyst provided in an exhaust system of an internal combustion engine, wherein a NOx storage amount is obtained, and when the NOx storage amount reaches a reference value, a reducing component containing hydrocarbon is supplied by exhaust gas. By running the spike,
An exhaust emission control device for an internal combustion engine, which reduces NOx stored in the NOx storage reduction catalyst, wherein the hydrocarbon detection means determines the amount of hydrocarbons flowing into the NOx storage reduction catalyst and the hydrocarbon detection means. In the case where the amount of inflowing hydrocarbons may hinder the exhaust purification in the NOx storage reduction catalyst, rich spike prohibiting means for prohibiting or stopping the execution of the rich spike in advance is provided. An exhaust purification device for an internal combustion engine. 10. A rich NOx storing and reducing catalyst provided in an exhaust system of an internal combustion engine is obtained, and when the NOx storing amount reaches a reference value, a reducing component containing hydrocarbon is supplied by exhaust. An exhaust emission control device for an internal combustion engine that reduces NOx stored in the NOx storage reduction catalyst by executing a spike, the hydrocarbon detection means for obtaining the amount of hydrocarbons flowing into the NOx storage reduction catalyst, When the amount of inflowing hydrocarbons obtained by the hydrogen detection means may hinder the NOx purification in the NOx storage reduction catalyst, rich spike prohibition means for prohibiting or stopping the execution of the rich spike in advance An exhaust emission control device for an internal combustion engine, comprising: 11. A rich NOx storing and reducing catalyst provided in an exhaust system of an internal combustion engine is obtained, and when the NOx storing amount reaches a reference value, a reducing component containing hydrocarbon is supplied by exhaust. An exhaust emission control device for an internal combustion engine that reduces NOx stored in the NOx storage reduction catalyst by executing a spike, the hydrocarbon detection means for obtaining the amount of hydrocarbons flowing into the NOx storage reduction catalyst, If the amount of inflowing hydrocarbons obtained by the hydrogen detection means exceeds the hydrocarbon purification capacity of the NOx storage reduction catalyst, rich spike prohibition means for prohibiting or stopping the execution of the rich spike in advance is provided. An exhaust emission control device for an internal combustion engine, characterized in that 12. A rich NOx storage reduction catalyst provided in an exhaust system of an internal combustion engine, wherein a NOx storage amount is obtained, and when the NOx storage amount reaches a reference value, a reducing component containing a hydrocarbon is supplied by exhaust gas. An exhaust emission control device for an internal combustion engine, which reduces NOx stored in the NOx storage reduction catalyst by executing a spike, the hydrocarbon detection means for obtaining a concentration of hydrocarbons flowing into the NOx storage reduction catalyst, If the inflowing hydrocarbon concentration obtained by the hydrogen detecting means exceeds the hydrocarbon purification capacity of the NOx storage reduction catalyst, rich spike prohibiting means for prohibiting or stopping the execution of the rich spike in advance is provided. An exhaust emission control device for an internal combustion engine, characterized in that 13. A rich NOx storage / reduction catalyst provided in an exhaust system of an internal combustion engine, wherein a NOx storage amount is obtained, and when the NOx storage amount reaches a reference value, a reducing component containing a hydrocarbon is supplied by exhaust gas. An exhaust emission control device for an internal combustion engine, which reduces NOx stored in the NOx storage reduction catalyst by executing a spike, and is a hydrocarbon detection means for determining a hydrocarbon flow rate per unit time flowing into the NOx storage reduction catalyst. And if the hydrocarbon flow rate per unit time obtained by the hydrocarbon detection means exceeds the hydrocarbon purification capacity of the NOx storage reduction catalyst, the rich spike is prohibited in advance or is stopped midway. An exhaust emission control device for an internal combustion engine, comprising: spike prohibiting means. 14. The internal combustion engine according to claim 9, wherein the rich spike prohibiting means does not perform a process of prohibiting the rich spike or stopping the rich spike in advance except during idle time. Exhaust gas purification device for engines. 15. The start catalyst having an oxygen storage function is arranged upstream of the NOx storage reduction catalyst in the exhaust system of the internal combustion engine according to claim 9, and carbonization by the start catalyst is performed. A start catalyst purification capacity detection means for determining the degree of purification of hydrogen is provided, and the hydrocarbon detection means considers the degree of purification of hydrocarbons by the start catalyst obtained by the start catalyst purification capacity detection means, and the NOx. An exhaust emission control device for an internal combustion engine, characterized in that the amount of hydrocarbons flowing into the storage reduction catalyst, the concentration of hydrocarbons, or the flow rate of hydrocarbons per unit time is obtained. 16. The hydrocarbon detector according to claim 9, wherein the hydrocarbon detection means indicates the amount of hydrocarbons in the exhaust gas discharged from the combustion chamber of the internal combustion engine, the hydrocarbon concentration, or the hydrocarbon flow rate per unit time. An exhaust emission control device for an internal combustion engine, which is characterized in that it is required. 17. The exhaust system of an internal combustion engine according to claim 16, wherein a start catalyst having an oxygen storage function is arranged upstream of the NOx storage reduction catalyst, and the degree of purification of hydrocarbons by the start catalyst is increased. A required start catalyst purification capacity detecting means is provided, and the rich spike inhibiting means is a hydrocarbon amount in the exhaust gas discharged from the combustion chamber of the internal combustion engine obtained by the hydrocarbon detecting means, a hydrocarbon concentration or per unit time. Whether or not the hydrocarbon flow rate of the NOx inhibits the purification in the NOx storage reduction catalyst or exceeds the purification capacity,
An exhaust gas purification apparatus for an internal combustion engine, characterized in that the determination is made in consideration of a degree of purification of hydrocarbons by a start catalyst obtained by the start catalyst purification ability detection means. 18. The start catalyst purifying ability detecting means according to claim 15 or 17, based on an air-fuel ratio detected from an exhaust component upstream of the start catalyst and a bed temperature of the start catalyst. ,
An exhaust gas purification apparatus for an internal combustion engine, wherein the degree of purification of hydrocarbons by the start catalyst is obtained.