JP2002155724A - Exhaust gas purification device for internal combustion engine - Google Patents

Abstract

(57) Abstract: An object of the present invention is to provide an exhaust gas purification apparatus for an internal combustion engine equipped with a particulate filter carrying a NOx absorbent, without increasing the fuel consumption unnecessarily. It is an object to provide a technique capable of sufficiently eliminating poisoning and PM poisoning. SOLUTION: An exhaust gas purifying apparatus for an internal combustion engine according to the present invention requires a particulate filter carrying a NOx absorbent and eliminating poisoning of the particulate filter by oxides and / or particulate matter. Occurs, on the condition that the deceleration operation state of the internal combustion engine is detected, provided with a poisoning elimination unit that executes the poisoning elimination processing of the particulate filter, and when the internal combustion engine is in the deceleration operation state, and It is characterized in that the poisoning elimination process of the particulate filter is executed when the vehicle is in the idling operation state.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for purifying exhaust gas of an internal combustion engine, and more particularly to a technique for purifying nitrogen oxides (NO
The present invention relates to an exhaust gas purification device having a means for removing x) and a means for removing particulate matter in exhaust gas.

[0002]

2. Description of the Related Art In general, in an internal combustion engine mounted on an automobile or the like, in particular, a diesel engine, in addition to nitrogen oxides (NOx) contained in exhaust gas, particulate matter (PM: Par
In response to such a demand, a method has been proposed in which a particulate filter carrying a NOx absorbent is disposed in an exhaust passage of an internal combustion engine.

The NOx absorbent absorbs nitrogen oxides (NOx) in the exhaust gas when the oxygen concentration of the inflowing exhaust gas is high, and absorbs the nitrogen oxides (NOx) when the oxygen concentration of the inflowing exhaust gas decreases. It emits. The particulate filter is formed of a porous base material having a plurality of pores, and is a filter that traps PM in the exhaust gas when the exhaust gas flows through the pores.

[0004] By disposing the particulate filter carrying the NOx absorbent in the exhaust passage of the internal combustion engine, it is possible to remove nitrogen oxides (NOx) and PM contained in the exhaust gas.

By the way, the P of the particulate filter
Since the M trapping capacity is limited, if particulate matter of PM trapping capacity or more is trapped by the particulate filter,
So-called PM poisoning, which causes clogging of the exhaust flow passage in the particulate filter and causes problems such as an excessive increase in back pressure, occurs. For this reason, when the particulate filter is arranged in the exhaust passage of the internal combustion engine, it is necessary to eliminate the PM poisoning of the particulate filter before the back pressure rises excessively.

As a method of eliminating PM poisoning of the particulate filter, the temperature of the particulate filter is raised to a high temperature range of about 500 ° C. to 700 ° C., and the air-fuel ratio of exhaust gas flowing into the particulate filter is reduced. By setting the air-fuel ratio, the particulate matter (P
A method for oxidizing (burning) M) is known.

Further, the fuel of the internal combustion engine sometimes contains a sulfur (S) component. When such a fuel is burned in the internal combustion engine, the sulfur (S) component in the fuel is oxidized. S
Since the sulfur oxides such as O ₂ or SO ₃ (SOx) is formed, sulfur oxides in exhaust gas discharged from the internal combustion engine (SO
x) will be included.

The exhaust gas containing sulfur oxide (SOx) is N
When flowing into the Ox absorbent, sulfur oxides (SOx) are absorbed by the NOx absorbent by the same mechanism as nitrogen oxides (NOx). However, the nitrogen oxides (NOx) absorbed by the NOx absorbent form stable barium sulfate (BaSO ₄ ) with the passage of time. Therefore, simply reducing the oxygen concentration of the exhaust gas flowing into the NOx absorbent is not sufficient. It is difficult to decompose and release and tends to accumulate in the NOx absorbent.

When the accumulated amount of SOx in the NOx absorbent increases,
The so-called SOx poisoning occurs, in which the NOx absorbing ability of the NOx absorbent is reduced and nitrogen oxides (NOx) in the exhaust gas cannot be sufficiently removed. For this reason, when the NOx absorbent is disposed in the exhaust passage of the internal combustion engine, it is necessary to eliminate SOx poisoning of the NOx absorbent before the NOx absorbing ability of the NOx absorbent excessively decreases.

As a method for eliminating SOx poisoning of the NOx absorbent, the ambient temperature of the NOx absorbent is set to about 500 ° C.
By raising the temperature to a high temperature range of 700 ° C. and making the air-fuel ratio of the exhaust gas flowing into the NOx absorbent a rich air-fuel ratio, barium sulfate (B
aSO ₄ ) is thermally decomposed into SO ₃₋ and SO ₄₋ and then SO _{3 −}
And SO _4- to remove hydrocarbons (HC) and carbon monoxide (C
A method is known in which the compound is reacted with O) to reduce it to gaseous SO ₂₋ .

Therefore, when the particulate filter carrying the NOx absorbent is disposed in the exhaust passage of the internal combustion engine, SOx poisoning of the particulate filter and P
It is necessary to eliminate M poisoning as appropriate. In order to eliminate SOx poisoning and PM poisoning of the particulate filter, it is necessary to raise the temperature of the particulate filter to a high temperature range of 500 ° C. or higher. It is conceivable to perform SOx poisoning elimination processing or PM poisoning elimination processing during operation.

However, when the internal combustion engine is in a high-load, high-speed operation state, the amount of exhaust gas discharged from the internal combustion engine increases, so that the air-fuel ratio of the exhaust gas is increased to eliminate SOx poisoning of the particulate filter. To achieve the air-fuel ratio, a large amount of fuel corresponding to the displacement is required, and there is a problem that fuel consumption increases.

To cope with such a problem, an exhaust gas purifying apparatus for an internal combustion engine as disclosed in Japanese Patent Application Laid-Open No. 8-170558 has been proposed. The exhaust gas purifying apparatus for an internal combustion engine described in the above-mentioned publication heats the catalyst and controls the air-fuel ratio of the exhaust gas flowing into the catalyst to a richer side than the stoichiometric air-fuel ratio during an idle operation in which the exhaust gas flow rate is reduced. Another object of the present invention is to eliminate catalyst poisoning while suppressing an increase in fuel consumption due to unnecessary cooling of the catalyst by exhaust gas and enrichment of exhaust gas.

[0014]

By the way, when the internal combustion engine is in an idling operation state, the flow rate of exhaust gas discharged from the internal combustion engine per unit time decreases, and accordingly, the exhaust gas flows into the catalyst per unit time. Since the flow rate of the exhaust gas also decreases, the amount of fuel flowing into the catalyst per unit time when the air-fuel ratio of the exhaust gas is set to the rich air-fuel ratio also decreases.

Therefore, in the exhaust gas purifying apparatus in which the catalyst poisoning elimination process is executed only during the idling operation as in the above-described conventional exhaust gas purifying apparatus, the internal combustion engine is operated for a long period of time in order to eliminate the catalyst poisoning. If the internal combustion engine needs to be operated and the idling operation of the internal combustion engine is not continued for a long time, it becomes difficult to eliminate poisoning of the catalyst.

Further, the above-mentioned conventional exhaust gas purifying apparatus is
When applied to a particulate filter loaded with x absorbent, PM poisoning elimination processing needs to be performed in addition to SOx poisoning elimination processing.
It is assumed that it will be difficult to sufficiently perform the Ox poisoning elimination process and the PM poisoning elimination process.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described various problems, and in an exhaust gas purifying apparatus for an internal combustion engine having a particulate filter carrying a NOx absorbent, fuel consumption is unnecessarily increased. It is an object of the present invention to provide a technique capable of reliably eliminating SOx poisoning and PM poisoning of a particulate filter without causing the particulate filter to poison.

[0018]

The present invention employs the following means to solve the above-mentioned problems. That is, the exhaust gas purification device for an internal combustion engine according to the present invention is provided in the exhaust passage of the internal combustion engine, absorbs nitrogen oxides in the exhaust gas when the oxygen concentration of the inflow exhaust gas is high, and reduces the oxygen concentration of the inflow exhaust gas. When it is necessary to eliminate the particulate filter having a function of releasing nitrogen oxides that have been absorbed, and the poisoning of the particulate filter by oxides and / or the particulate matter, And a poisoning elimination unit that executes a poisoning elimination process for the particulate filter when a deceleration operation state is detected.

In the exhaust gas purifying apparatus for an internal combustion engine configured as described above, if it becomes necessary to eliminate the poisoning of the particulate filter by the oxide and / or the particulate matter, the poisoning eliminating means is provided by the internal combustion engine. On the condition that the deceleration operation state is detected, the processing for eliminating poisoning of the particulate filter is executed.

In this case, the processing for eliminating poisoning of the particulate filter is performed not only during the period when the internal combustion engine is in the deceleration operation state but also during the deceleration operation period when the internal combustion engine is shifted from the deceleration operation state to the idle operation state. In addition to this, it is also executed during the idle operation period.

As a result, the execution area of the poisoning elimination process is expanded as compared with the case where the poisoning elimination process is executed only when the internal combustion engine is in the idling operation state.

In the exhaust gas purifying apparatus for an internal combustion engine according to the present invention, when the poisoning eliminating means needs to eliminate the poisoning of the particulate filter by the oxide and the particulate matter, The air-fuel ratio of the exhaust gas flowing into the particulate filter may be set to the rich air-fuel ratio for a first predetermined period from the time when the deceleration operation state is detected, and the lean air-fuel ratio may be set for the second predetermined period.

In this case, the air-fuel ratio of the exhaust gas flowing into the particulate filter is set to the rich air-fuel ratio during the first predetermined period from the time when the deceleration operation state of the internal combustion engine is detected, so that the exhaust gas flows into the particulate filter. The exhaust is
The exhaust gas contains a relatively large amount of reducing components such as hydrocarbons (HC) and carbon monoxide (CO).

When the exhaust gas containing a large amount of reducing components flows into the particulate filter, the oxide poisoning the particulate filter easily reacts with the reducing components in the exhaust gas. Elimination of poisoning is promoted.

Subsequently, in the second predetermined period after the first predetermined period has elapsed since the detection of the deceleration operation state of the internal combustion engine, the air-fuel ratio of the exhaust gas flowing into the particulate filter is set to the lean air-fuel ratio. Therefore, the exhaust gas flowing into the particulate filter is an exhaust gas containing a relatively large amount of oxygen.

When the exhaust gas containing a large amount of oxygen flows into the particulate filter, the particulate matter poisoning the particulate filter easily reacts with the oxygen contained in the exhaust gas. Elimination of poisoning by particulate matter of the filter is promoted.

As described above, if the processing for eliminating the poisoning of the particulate filter by the oxide and the poisoning by the particulate matter is performed on the condition that the deceleration operation state of the internal combustion engine is detected, the poisoning of the particulate filter is performed. The cancellation process is executed not only during the period when the internal combustion engine is in the deceleration operation state but also during the idle operation period in addition to the deceleration operation period when the internal combustion engine transitions from the deceleration operation state to the idle operation state. become.

As a result, the execution period of the poisoning elimination process for oxides and the execution period of the poisoning elimination process for particulate matter are sufficiently ensured.

As a method of changing the air-fuel ratio of the exhaust gas flowing into the particulate filter, a sub-injection amount by a fuel injection valve for directly injecting fuel into the cylinder of the internal combustion engine, and / or a method of changing the air-fuel ratio upstream of the particulate filter. An example of a method of changing the amount by controlling the amount of addition means for adding fuel to the exhaust passage can be exemplified.

Further, when the exhaust gas purifying apparatus for an internal combustion engine according to the present invention further includes an exhaust gas recirculation mechanism for recirculating a part of the exhaust gas flowing through the exhaust passage of the internal combustion engine to the intake passage, When the poisoning by the oxide of the filter is eliminated, the poisoning eliminating means may control the exhaust gas recirculation mechanism so as to increase the amount of exhaust gas recirculated from the exhaust passage to the intake passage.

In this case, the amount of exhaust gas recirculated from the exhaust passage to the intake passage is increased during the period in which the process of eliminating poisoning of the particulate filter by the oxide is performed. The amount of fresh air will be reduced instead of increasing the amount of exhaust gas taken into the vehicle.

As a result, the amount of oxygen sucked into the internal combustion engine decreases, and accordingly, the amount of oxygen contained in the exhaust gas discharged from the internal combustion engine also decreases, and the air-fuel ratio of the exhaust gas is reduced to the rich air-fuel ratio. It is possible to reduce the amount of fuel (or reducing agent) required in the case. Furthermore, in an internal combustion engine in which combustion is prohibited during the deceleration operation state, the intake air of the internal combustion engine is directly discharged as exhaust gas, so that when the amount of fresh air taken into the internal combustion engine is reduced, The amount of fresh air flowing into the particulate filter is reduced, so that it is possible to suppress the particulate filter from being cooled by relatively low-temperature fresh air.

The exhaust gas purifying apparatus for an internal combustion engine according to the present invention further includes an intake throttle valve provided in an intake passage of the internal combustion engine for adjusting a flow rate of intake air flowing through the intake passage. When the poisoning by the oxide of the curated filter is eliminated, the poisoning eliminating means may reduce the opening of the intake throttle valve.

In this case, the amount of fresh air sucked into the internal combustion engine is reduced during the period in which the processing for eliminating the poisoning of the particulate filter by the oxide is performed. Therefore, the amount of exhaust gas discharged from the fuel cell is also reduced.

As a result, it is possible to reduce the amount of fuel (or reducing agent) required when the air-fuel ratio of the exhaust gas is set to the rich air-fuel ratio. Furthermore, in an internal combustion engine in which combustion is prohibited during the deceleration operation state, the intake air of the internal combustion engine is directly discharged as exhaust gas, so that when the amount of fresh air taken into the internal combustion engine is reduced, The amount of fresh air flowing into the particulate filter is reduced, so that it is possible to suppress the particulate filter from being cooled by relatively low-temperature fresh air.

When the exhaust gas purifying apparatus for an internal combustion engine according to the present invention includes both an exhaust gas recirculation mechanism and an intake throttle valve, the poisoning eliminating means removes the poisoning of the particulate filter by the oxide. When solving the problem, the amount of fresh air sucked into the internal combustion engine may be reduced by using the exhaust gas recirculation mechanism and the intake throttle valve together.

Further, the exhaust gas purifying apparatus for an internal combustion engine according to the present invention may further include a deceleration torque generating means for generating a desired deceleration torque when the processing for eliminating poisoning of the particulate filter is executed. Good.

This is based on the assumption that combustion is performed in the internal combustion engine to suppress a decrease in exhaust gas temperature in the particulate filter poisoning elimination process, in other words, to suppress a decrease in the temperature of the particulate filter. When the air-fuel mixture is burned in the internal combustion engine in the operating state, the negative torque (so-called engine braking force) generated by the internal combustion engine decreases, and the deceleration performance of the vehicle equipped with the internal combustion engine decreases. This is because it is conceivable.

Here, the method of generating the deceleration torque includes a method of reducing the generated torque of the internal combustion engine, a method of increasing the braking force by a braking device provided in a vehicle equipped with the internal combustion engine, or the above two methods. Examples of the method may be a method in which the methods are appropriately combined.

As a method for reducing the generated torque of the internal combustion engine, a method of advancing the combustion timing of the internal combustion engine,
Preferably, a method of advancing the combustion timing to before the top dead center of the compression stroke can be exemplified.

When the air-fuel mixture is burned before the top dead center of the compression stroke in the internal combustion engine, the pressure (combustion pressure) generated by the combustion of the air-fuel mixture prevents the piston from rising, and as a result, the internal combustion engine Will decrease.

Here, in advancing the combustion timing of the internal combustion engine, the ignition timing may be advanced when the internal combustion engine according to the present invention is a gasoline engine equipped with a spark plug, or When the internal combustion engine according to the present invention is a compression ignition type diesel engine having no spark plug, the fuel injection timing may be advanced.

Further, the internal combustion engine according to the present invention is a compression ignition type diesel engine, wherein a main fuel injection means for injecting a main fuel supplied to a cylinder for combustion and a secondary fuel injection means prior to the injection of the main fuel. In the case of an internal combustion engine having pilot injection means for injecting fuel into a cylinder, the deceleration torque generating means may advance the fuel injection timing of the main fuel injection means and the fuel injection timing of the pilot injection means. You may.

When the internal combustion engine according to the present invention has an exhaust gas recirculation mechanism, the deceleration torque generating means advances the fuel injection timing of the internal combustion engine and recirculates the exhaust gas by the exhaust gas recirculation mechanism. The amount may be increased.

Generally, since the exhaust gas of an internal combustion engine contains an inert gas component such as carbon dioxide (CO2) and water (H2O), the exhaust gas recirculated by an exhaust gas recirculation mechanism is contained in the mixture. Then, the combustion heat of the air-fuel mixture is absorbed by the nonflammability and heat absorption of the inert gas component, and the combustion pressure generated when the air-fuel mixture burns decreases accordingly.

Therefore, when the combustion injection timing of the internal combustion engine is advanced and the amount of exhaust gas recirculated by the exhaust gas recirculation mechanism is increased, the deceleration torque of the internal combustion engine is easily generated.

[0047]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A specific embodiment of an exhaust gas purifying apparatus for an internal combustion engine according to the present invention will be described below with reference to the drawings. Here, a case where the exhaust gas purification apparatus according to the present invention is applied to a diesel engine for driving a vehicle will be described as an example.

<First Embodiment> First, a first embodiment of an exhaust gas purifying apparatus for an internal combustion engine according to the present invention will be described with reference to FIG.
This will be described with reference to FIG.

FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine to which the exhaust gas purifying apparatus according to the present invention is applied and an intake / exhaust system thereof.

The internal combustion engine 1 shown in FIG. 1 is a water-cooled four-stroke cycle diesel engine having four cylinders 2.

The internal combustion engine 1 has a fuel injection valve 3 for directly injecting fuel into the combustion chamber of each cylinder 2. Each fuel injection valve 3 is connected to a pressure accumulation chamber (common rail) 4 for accumulating fuel up to a predetermined pressure. The common rail 4 is provided with a common rail pressure sensor 4a that outputs an electric signal corresponding to the pressure of the fuel in the common rail 4.

The common rail 4 communicates with a fuel pump 6 via a fuel supply pipe 5. This fuel pump 6
Is a pump that operates using the rotational torque of the output shaft (crankshaft) of the internal combustion engine 1 as a drive source. A pump pulley 6 a attached to the input shaft of the fuel pump 6 is connected to the output shaft (crankshaft) of the internal combustion engine 1. It is connected to the attached crank pulley 1a via a belt 7.

In the fuel injection system configured as described above, when the rotational torque of the crankshaft is transmitted to the input shaft of the fuel pump 6, the fuel pump 6 is transmitted from the crankshaft to the input shaft of the fuel pump 6. The fuel is discharged at a pressure corresponding to the rotating torque.

The fuel discharged from the fuel pump 6 is
The fuel is supplied to the common rail 4 via the fuel supply pipe 5, and is accumulated to a predetermined pressure by the common rail 4. Common rail 4
The fuel stored at the predetermined pressure is distributed to the fuel injection valve 3 of each cylinder 2. The fuel injection valve 3 opens when a drive current is applied, and injects fuel into the combustion chamber of each cylinder 2.

Next, an intake branch pipe 8 is connected to the internal combustion engine 1, and each branch pipe of the intake branch pipe 8 communicates with a combustion chamber of each cylinder 2 via an intake port (not shown). .

The intake branch pipe 8 is connected to an intake pipe 9,
This intake pipe 9 is connected to an air cleaner box 10. An air flow meter 11 that outputs an electric signal corresponding to the mass of the intake air flowing through the intake pipe 9 and an electric current corresponding to the temperature of the intake air flowing through the intake pipe 9 are provided at an intake pipe 9 downstream of the air cleaner box 10. An intake air temperature sensor 12 that outputs a signal is attached.

An intake throttle valve 13 for adjusting the flow rate of intake air flowing through the intake pipe 9 is provided at a portion of the intake pipe 9 located immediately upstream of the intake branch pipe 8. The intake throttle valve 13 has an intake throttle actuator 1 that includes a stepper motor or the like and drives the intake throttle valve 13 to open and close.
4 is attached.

A compressor housing 15a of a centrifugal supercharger (turbocharger) 15 which operates using heat energy of exhaust gas as a drive source is provided in an intake pipe 9 located between the air flow meter 11 and the intake throttle valve 13. And
An intercooler 16 for cooling intake air, which has been compressed in the compressor housing 15a and has become high temperature, is provided in the intake pipe 9 downstream of the compressor housing 15a.
Is provided.

In the intake system configured as described above, the intake air flowing into the air cleaner box 10 passes through the intake pipe 9 after dust and the like in the intake are removed by an air cleaner (not shown) in the air cleaner box 10. And flows into the compressor housing 15a.

The intake air flowing into the compressor housing 15a is compressed by rotation of a compressor wheel provided inside the compressor housing 15a. The intake air that has been compressed in the compressor housing 15a and has become high temperature is cooled by the intercooler 16, and then flows into the intake branch pipe 8 with the flow rate adjusted by the intake throttle valve 13 as necessary. The intake air flowing into the intake branch pipe 8 is distributed to the combustion chamber of each cylinder 2 via each branch pipe, and is burned using the fuel injected from the fuel injection valve 3 of each cylinder 2 as an ignition source.

On the other hand, an exhaust branch pipe 18 is connected to the internal combustion engine 1, and each branch pipe of the exhaust branch pipe 18 communicates with the combustion chamber of each cylinder 2 via an exhaust port (not shown).

The exhaust branch pipe 18 is connected to the centrifugal supercharger 15.
Of the turbine housing 15b. The turbine housing 15b is connected to an exhaust pipe 19, and the exhaust pipe 19 is connected downstream to a muffler (not shown).

In the middle of the exhaust pipe 19, a particulate filter 20 for removing and purifying harmful gas components in the exhaust gas is disposed. An exhaust pipe 19 downstream of the particulate filter 20 has an air-fuel ratio sensor 23 that outputs an electric signal corresponding to the air-fuel ratio of the exhaust flowing through the exhaust pipe 19, and a temperature corresponding to the temperature of the exhaust flowing through the exhaust pipe 19. And an exhaust gas temperature sensor 24 for outputting a detected electric signal.

The exhaust pipe 19 downstream of the air-fuel ratio sensor 23 and the exhaust temperature sensor 24 is provided with an exhaust throttle valve 21 for adjusting the flow rate of exhaust flowing through the exhaust pipe 19. The exhaust throttle valve 21 is provided with an exhaust throttle actuator 22 configured by a stepper motor or the like and driving the exhaust throttle valve 21 to open and close.

In the exhaust system configured as described above, the air-fuel mixture (burned gas) burned in each cylinder 2 of the internal combustion engine 1 is discharged to the exhaust branch pipe 18 through the exhaust port, and then to the exhaust branch pipe 18. To the turbine housing 15b of the centrifugal supercharger 15
Flows into The exhaust gas flowing into the turbine housing 15b rotates a turbine wheel rotatably supported in the turbine housing 15b by using thermal energy of the exhaust gas. At this time, the rotational torque of the turbine wheel is transmitted to the compressor wheel of the compressor housing 15a described above.

The exhaust gas discharged from the turbine housing 15b flows into a particulate filter 20 via an exhaust pipe 19, and harmful gas components in the exhaust gas are removed or purified. The exhaust gas from which the harmful gas components have been removed or purified by the particulate filter 20 is discharged into the atmosphere via a muffler after the flow rate is adjusted by an exhaust throttle valve 21 as necessary.

The exhaust branch pipe 18 and the intake branch pipe 8 communicate with each other via an exhaust gas recirculation passage (EGR passage) 25 for recirculating a part of the exhaust flowing through the exhaust branch pipe 18 to the intake branch pipe 8. Have been. In the middle of the EGR passage 25, a flow rate adjusting valve (EGR) configured by an electromagnetic valve or the like to change the flow rate of exhaust gas (hereinafter, referred to as EGR gas) flowing in the EGR passage 25 according to the magnitude of the applied electric power. (Valve) 26 is provided.

In the EGR passage 25, the EGR valve 26
The EG flowing in the EGR passage 25 is located at a more upstream portion.
An EGR cooler 27 for cooling the R gas is provided.

In the exhaust gas recirculation mechanism configured as described above, when the EGR valve 26 is opened, the EGR passage 25 becomes conductive, and a part of the exhaust gas flowing through the exhaust branch pipe 18 flows to the EGR passage 25. It flows into the intake branch pipe 8 through the EGR cooler 27.

At this time, in the EGR cooler 27, heat exchange is performed between the EGR gas flowing in the EGR passage 25 and a predetermined refrigerant, and the EGR gas is cooled.

The EGR gas recirculated from the exhaust branch pipe 18 to the intake branch pipe 8 via the EGR passage 25 is guided to the combustion chamber of each cylinder 2 while mixing with fresh air flowing from the upstream of the intake branch pipe 8. Then, the fuel injected from the fuel injection valve 3 is burned using the ignition source.

Here, the EGR gas contains an inert gas component such as water (H ₂ O) or carbon dioxide (CO ₂ ) that does not burn itself and has endothermic properties. Therefore, if EGR gas is contained in the air-fuel mixture,
The combustion temperature of the air-fuel mixture is lowered, so that nitrogen oxides (NO
x) is suppressed.

Further, when the EGR gas is cooled in the EGR cooler 27, the temperature of the EGR gas itself decreases and the volume of the EGR gas decreases, so that when the EGR gas is supplied into the combustion chamber, The ambient temperature of the air does not unnecessarily rise, and the amount of fresh air (volume of fresh air) supplied into the combustion chamber does not unnecessarily decrease.

Next, the particulate filter 20 according to the present embodiment will be specifically described.

FIG. 2 is a view showing the structure of the particulate filter 20. FIG. 2A is a front view of the particulate filter 20, and FIG. FIG. 4 shows a side sectional view.

As shown in FIGS. 2A and 2B, the particulate filter 20 includes a first exhaust passage 50 whose downstream end is closed by a plug 52 and an upstream end. Is a wall flow type filter made of a porous base material, wherein the second exhaust flow paths 51 closed by plugs 53 and the second exhaust flow paths 51 are alternately arranged in a honeycomb shape through partition walls 54. In addition, as a base material of the particulate filter 20, cordierite, ceramic, or the like can be exemplified.

The partition wall 54 of the particulate filter 20
When the oxygen concentration of the exhaust gas flowing through the particulate filter 20 is high, nitrogen oxide (NOx) contained in the exhaust gas is absorbed on the surface of the When the oxygen concentration of the exhaust gas flowing through the filter 20 decreases and a reducing agent such as hydrocarbon (HC) is present, it is reduced to nitrogen (N ₂ ) while releasing the absorbed nitrogen oxide (NOx). An NOx storage reduction catalyst is supported.

The storage-reduction NOx catalyst uses, for example, alumina (Al ₂ O ₃ ) as a carrier and, for example, potassium (K), sodium (Na), lithium (Li), or cesium (Cs) on the carrier. At least one selected from an alkali metal, an alkaline earth such as barium (Ba) or calcium (Ca), and a rare earth such as lanthanum (La) or yttrium (Y);
and a noble metal such as t).

In the particulate filter 20 configured as described above, the exhaust gas that has flowed into the particulate filter 20 first flows into the first exhaust passage 50, and the surrounding exhaust gas flows as shown by the arrow in FIG. It flows to the adjacent second exhaust passage 51 through the pores of the partition wall 54.

When the exhaust gas passes through the partition wall 54, so-called particulate matter (PM) such as soot and SOF (Soluble Organic Fraction) contained in the exhaust gas is collected.

When the air-fuel ratio of the exhaust gas flowing into the particulate filter 20 is an oxygen-excess air-fuel ratio (lean air-fuel ratio), the NOx storage reduction catalyst carried on the particulate filter 20 causes the NOx catalyst in the exhaust Absorbs oxides (NOx). When the air-fuel ratio of the exhaust gas flowing into the particulate filter 20 becomes the stoichiometric air-fuel ratio or the rich air-fuel ratio, and the oxygen concentration decreases and the concentration of the reducing agent increases, the nitrogen oxides absorbed by the NOx storage reduction catalyst are reduced. (NOx) is reduced and purified while being released.

Here, the NOx absorption / desorption mechanism of the NOx storage reduction catalyst will be described with reference to an example of the NOx storage reduction catalyst in which platinum (Pt) and barium (Ba) are supported on a carrier made of alumina.

It is considered that the NOx absorbing / releasing action of the NOx storage reduction catalyst is performed by a mechanism as shown in FIG.

First, in the NOx storage reduction catalyst, when the air-fuel ratio of the exhaust gas flowing into the NOx storage reduction catalyst becomes a lean air-fuel ratio and the oxygen concentration in the exhaust gas increases, as shown in FIG. In addition, oxygen (O ₂ ) in the exhaust gas changes to O ₂ ^- or O ^2-
And adheres to the surface of platinum (Pt) in the form of, and the nitrogen monoxide (NO) in the exhaust gas becomes O ₂ ^- or O ^2-
To form nitrogen dioxide (NO ₂ ) (2NO +
O ₂ → 2NO ₂ ).

Nitrogen dioxide (NO ₂ ) is oxidized on the surface of platinum (Pt) and combines with barium oxide (BaO) to form nitrate ions (NO ₃ ⁻ ). Thus, the nitrogen oxides (NOx) in the exhaust gas are stored in the storage-reduction NOx catalyst as nitrate ions (NO ₃ ⁻ ).

The above-described NOx storage operation is continued as long as the air-fuel ratio of the inflowing exhaust gas is lean and the NOx storage capacity of the storage reduction type NOx catalyst is not saturated.

On the other hand, the storage reduction type NOx catalyst is
When the oxygen concentration of the inflow exhaust gas decreases, nitrogen dioxide (N
O ₂ ) is reduced, so that barium oxide (Ba)
The nitrate ion (NO ₃ ⁻ ) bonded to O) is conversely converted to nitrogen dioxide (NO ₂ ) or nitric oxide (NO) and is released from the NOx storage reduction catalyst.

That is, when the oxygen concentration of the exhaust gas flowing into the NOx storage reduction catalyst decreases, nitrate ions (NO ₃ ⁻ )
Nitrogen oxide (NOx) stored in the NOx storage reduction catalyst in the form of nitrogen dioxide (NO ₂ ) or nitrogen monoxide (N
O) and is released from the NOx storage reduction catalyst.

As shown in FIG. 3B, the nitrogen oxides (NOx) released from the NOx storage reduction catalyst are reduced components (for example, platinum (Pt) of the NOx storage reduction catalyst) contained in the exhaust gas. ) Reacts with the above oxygen O ₂ ^- or O ^2- to react with a partially oxidized hydrocarbon (HC) or an active species such as carbon monoxide (CO)) and is reduced to nitrogen (N ₂ ).

[0090] That is, hydrocarbons in the exhaust gas (HC) and carbon monoxide (CO) is, O ₂ on the platinum (Pt) ^- or O ^2- reacts with being oxidized, whereby the upper platinum (Pt) of O ₂ ^- or O even ² is consumed Note if hydrocarbon (HC) and carbon monoxide (CO) is left, their hydrocarbon (HC) and carbon monoxide (CO) is storage-reduction Oxide (NOx) Released from Type NOx Catalyst and Internal Combustion Engine 1
Reacts with the nitrogen oxides discharged from the (NOx), as a result, nitrogen oxides (NOx) is brought into reduced to nitrogen (N _2).

Therefore, by setting the air-fuel ratio of the exhaust gas flowing into the NOx storage reduction catalyst to the stoichiometric air-fuel ratio or the rich air-fuel ratio, the nitrogen oxides (NOx) stored in the NOx storage reduction catalyst can be released. It is possible to reduce.

Since the NOx storage capacity of the NOx storage reduction catalyst is limited, when exhaust gas having a lean air-fuel ratio flows into the NOx catalyst over a long period of time, the NOx storage capacity of the NOx storage reduction catalyst becomes saturated. In addition, nitrogen oxides (NOx) in the exhaust gas are released to the atmosphere without being removed or purified by the NOx storage reduction catalyst.

However, in a diesel engine such as the internal combustion engine 1, a mixture having a lean air-fuel ratio is burned in most of the operating region, and the air-fuel ratio of exhaust gas becomes a lean air-fuel ratio in most of the operating region. Therefore, the NOx storage capacity of the storage reduction type NOx catalyst tends to be saturated.

Therefore, when the storage reduction type NOx catalyst is applied to a lean burn type internal combustion engine such as a diesel engine,
It is necessary to set the air-fuel ratio of the exhaust to a stoichiometric air-fuel ratio or a rich air-fuel ratio at a predetermined timing before the NOx storage capacity of the storage reduction type NOx catalyst is saturated.

On the other hand, the internal combustion engine 1 according to the present embodiment is provided with a reducing agent supply mechanism for adding fuel (light oil) as a reducing agent to the exhaust gas flowing through the exhaust passage upstream of the NOx storage reduction catalyst. I made it.

The reducing agent supply mechanism is an embodiment of the adding means according to the present invention. As shown in FIG. 1, the reducing agent supply mechanism is mounted on the cylinder head of the internal combustion engine 1 so that the injection hole faces the exhaust branch pipe 18. A reducing agent injection valve 28 which is mounted and opens when fuel of a predetermined valve opening pressure or higher is applied to inject fuel.
A reducing agent supply passage 29 for guiding the fuel discharged from the fuel pump 6 to the reducing agent injection valve 28; and a fuel supply passage 29 provided in the middle of the reducing agent supply passage 29 and flowing through the reducing agent supply passage 29. A flow control valve 30 for adjusting the flow rate, and a shutoff valve 31 provided in the reducing agent supply passage 29 upstream of the flow adjustment valve 30 to shut off the flow of fuel in the reducing agent supply passage 29
And a reducing agent pressure sensor 32 attached to the reducing agent supply passage 29 upstream of the flow control valve 30 and outputting an electric signal corresponding to the pressure in the reducing agent supply passage 29.

In the reducing agent injection valve 28, the injection hole of the reducing agent injection valve 28 is located downstream of the connection portion of the exhaust branch pipe 18 with the EGR passage 25, and the four branch pipes of the exhaust branch pipe 18 It is preferable that the projection is protruded to the exhaust port of the cylinder 2 closest to the collecting portion and is attached to the cylinder head so as to face the collecting portion of the exhaust branch pipe 18.

This prevents the reducing agent (unburned fuel component) injected from the reducing agent injection valve 28 from flowing into the EGR passage 25, and prevents the reducing agent from being centrifuged in the exhaust branch pipe 18 without stagnation. This is to reach the turbine housing 15b of the supercharger.

In the example shown in FIG. 1, the fourth (# 4) cylinder 2 of the four cylinders 2 of the internal combustion engine 1 is located closest to the gathering portion of the exhaust branch pipe 18, so that the fourth cylinder (# 4) 4) Although the reducing agent injection valve 28 is attached to the exhaust port of the cylinder 2, when the cylinder 2 other than the fourth (# 4) cylinder 2 is located closest to the collecting portion of the exhaust branch pipe 18, The reducing agent injection valve 28 is attached to the exhaust port of the cylinder 2.

Further, the reducing agent injection valve 28 is designed to penetrate a water jacket (not shown) formed in the cylinder head or to be mounted close to the water jacket, and to reduce the water using cooling water flowing through the water jacket. The agent injection valve 28 may be cooled.

In such a reducing agent supply mechanism, when the flow control valve 30 is opened, the high-pressure fuel discharged from the fuel pump 6 is supplied through the reducing agent supply passage 29 to the reducing agent injection valve 28.
Is applied. When the pressure of the fuel applied to the reducing agent injection valve 28 reaches or exceeds the valve opening pressure, the reducing agent injection valve 2
8 is opened, and fuel as a reducing agent is injected into the exhaust branch pipe 18.

The reducing agent injected from the reducing agent injection valve 28 into the exhaust branch pipe 18 flows into the turbine housing 15b together with the exhaust gas flowing from the upstream side of the exhaust branch pipe 18. The exhaust gas and the reducing agent that have flowed into the turbine housing 15b are:
The mixture is stirred and homogeneously mixed by the rotation of the turbine wheel to form a rich air-fuel ratio exhaust gas.

The rich air-fuel ratio exhaust gas thus formed flows from the turbine housing 15b into the particulate filter 20 via the exhaust pipe 19, and is stored in the NOx storage reduction catalyst of the particulate filter 20. The nitrogen oxides (NOx) are released and reduced to nitrogen (N ₂ ).

After that, when the flow control valve 30 is closed and the supply of the reducing agent from the fuel pump 6 to the reducing agent injection valve 28 is interrupted, the pressure of the fuel applied to the reducing agent injection valve 28 is reduced The pressure drops below the valve pressure, and as a result, the reducing agent injection valve 2
8 is closed, and the addition of the reducing agent into the exhaust branch pipe 18 is stopped.

The internal combustion engine 1 configured as described above is provided with an electronic control unit (ECU) 35 for controlling the internal combustion engine 1. The ECU 35 is a unit that controls the operating state of the internal combustion engine 1 according to the operating conditions of the internal combustion engine 1 and the driver's requirements.

The ECU 35 includes a common rail pressure sensor 4
a, various types of air flow meter 11, intake air temperature sensor 12, intake pipe pressure sensor 17, air-fuel ratio sensor 23, exhaust gas temperature sensor 24, reducing agent pressure sensor 32, crank position sensor 33, water temperature sensor 34, accelerator opening degree sensor 36, etc. The sensors are connected via electric wiring, and output signals of the various sensors described above are input to the ECU 35.

On the other hand, the fuel injection valve 3, the intake throttle actuator 14, the exhaust throttle actuator 22, the EGR valve 26, the flow control valve 30, the shutoff valve 31, and the like are connected to the ECU 35 via electric wiring. Each part is ECU3
5 is controlled.

Here, as shown in FIG. 4, the ECU 35 is connected to a C
A PU 351, a ROM 352, a RAM 353, a backup RAM 354, an input port 356, and an output port 357.
And an A / D converter (A / D) 355 connected to.

The input port 356 inputs the output signals of a sensor that outputs a digital signal, such as the crank position sensor 33, and converts those output signals to C.
The data is transmitted to the PU 351 and the RAM 353.

The input port 356 is connected to the common rail pressure sensor 4a, the air flow meter 11,
2. Intake pipe pressure sensor 17, air-fuel ratio sensor 23, exhaust temperature sensor 24, reducing agent pressure sensor 32, water temperature sensor 3.
4. The output signal of a sensor that outputs a signal in the form of an analog signal, such as the accelerator opening sensor 36, is output to the A / D 355.
And outputs those output signals to the CPU 351 or R
It transmits to AM353.

The output port 357 is connected to the fuel injection valve 3,
Intake throttle actuator 14, exhaust throttle actuator 22, EGR valve 26, flow control valve 30, shut-off valve 31
Control signals output from the CPU 351 are connected to the fuel injection valve 3, the intake throttle actuator 14, the exhaust throttle actuator 22,
The signal is transmitted to the EGR valve 26, the flow control valve 30, or the shutoff valve 31.

The ROM 352 includes a fuel injection control routine for controlling the fuel injection valve 3, an intake throttle control routine for controlling the intake throttle valve 13, an exhaust throttle control routine for controlling the exhaust throttle valve 21, and EGR. In addition to various application programs such as an EGR control routine for controlling the valve 26, a reducing agent addition control routine for controlling the flow regulating valve 30, and a shutoff valve control routine for controlling the shutoff valve 31, the particulate filter 2
A poisoning elimination control routine for eliminating 0 poisoning is stored.

The ROM 352 stores various control maps in addition to the application programs described above. The control map includes, for example, a fuel injection amount control map indicating a relationship between an operation state of the internal combustion engine 1 and a basic fuel injection amount (basic fuel injection time), and a relation between the operation state of the internal combustion engine 1 and the basic fuel injection timing. Fuel injection timing control map,
An intake throttle valve opening control map showing the relationship between the operating state of the internal combustion engine 1 and the target opening of the intake throttle valve 13, and the exhaust throttle showing the relationship between the operating state of the internal combustion engine 1 and the target opening of the exhaust throttle valve 21. Valve opening control map, operating state of internal combustion engine 1 and EGR
EGR valve opening control map showing the relationship with the target opening of the valve 26; flow regulating valve control map showing the relationship between the operating state of the internal combustion engine 1 and the opening timing of the flow regulating valve 30; operating state of the internal combustion engine 1 And a shut-off valve control map showing the relationship between the opening and closing timing of the shut-off valve 31.

The RAM 353 stores an output signal from each sensor, a calculation result of the CPU 351 and the like. The calculation result is, for example, an engine speed calculated based on a time interval at which the crank position sensor 33 outputs a pulse signal. These data are rewritten to the latest data each time the crank position sensor 33 outputs a pulse signal.

The backup RAM 354 is a nonvolatile memory capable of storing data even after the operation of the internal combustion engine 1 is stopped.

The CPU 351 operates in accordance with the application program stored in the ROM 352 to control fuel injection, intake throttle control, exhaust throttle control, EG
In addition to the R control, the reducing agent addition control, and the shutoff valve control, the poisoning elimination control which is the gist of the present invention is executed.

For example, in the fuel injection control, the CPU 351
First, the amount of fuel injected from the fuel injection valve 3 is determined, and then the timing for injecting fuel from the fuel injection valve 3 is determined.

When determining the fuel injection amount, the CPU 35
1 reads the engine speed and the output signal (accelerator opening) of the accelerator opening sensor 36 stored in the RAM 353. The CPU 351 accesses the fuel injection amount control map and calculates a basic fuel injection amount (basic fuel injection time) corresponding to the engine speed and the accelerator opening. C
The PU 351 corrects the basic fuel injection time based on output signal values of the air flow meter 11, the intake air temperature sensor 12, the water temperature sensor 34, and the like, and determines a final fuel injection time.

When determining the fuel injection timing, the CPU 3
51 accesses a fuel injection timing control map and calculates a basic fuel injection timing corresponding to the engine speed and the accelerator opening. The CPU 351 is an air flow meter 1
1. The basic fuel injection timing is corrected using output signal values of the intake air temperature sensor 12, the water temperature sensor 34, and the like as parameters,
Determine the final fuel injection timing.

When the fuel injection time and the fuel injection timing are determined, the CPU 351 compares the fuel injection timing with the output signal of the crank position sensor 33, and the output signal of the crank position sensor 33 starts the fuel injection. At the time coincident with the timing, application of drive power to the fuel injection valve 3 is started. The CPU 351 stops applying the driving power to the fuel injection valve 3 when the elapsed time from the start of the application of the driving power to the fuel injection valve 3 reaches the fuel injection time.

In the intake throttle control, the CPU 351
Reads the engine speed and the accelerator opening stored in the RAM 353, for example. The CPU 351 accesses the intake throttle opening control map and calculates a target intake throttle opening corresponding to the engine speed and the accelerator opening. The CPU 351 applies drive power corresponding to the target intake throttle valve opening to the intake throttle actuator 14.

At this time, the CPU 351 sets the intake throttle valve 13
May be detected, and the intake throttle actuator 14 may be feedback-controlled based on the difference between the actual opening of the intake throttle valve 13 and the target intake throttle valve opening.

In the exhaust throttle control, the CPU 351
For example, when the internal combustion engine 1 is in a warm-up operation state after a cold start, or when a vehicle interior heater is in an operating state, the exhaust throttle actuator is driven to close the exhaust throttle valve 21 in the valve closing direction. 22 is controlled.

In this case, the load on the internal combustion engine 1 increases, and the fuel injection amount increases accordingly. As a result, the calorific value of the internal combustion engine 1 increases, the warm-up of the internal combustion engine 1 is promoted, or the heat source of the vehicle interior heater is secured.

In EGR control, the CPU 351
The engine speed, the accelerator opening, the output signal (cooling water temperature) of the water temperature sensor 34, and the like stored in the RAM 353 are read, and it is determined whether or not the execution condition of the EGR control is satisfied.

The above-mentioned EGR control execution conditions are as follows: the cooling water temperature is equal to or higher than a predetermined temperature; the internal combustion engine 1 has been continuously operated for a predetermined time or more from the start; Conditions such as certain conditions can be exemplified.

If it is determined that the above-described EGR control execution condition is satisfied, the CPU 351 accesses the EGR valve opening control map and sets the target EGR valve corresponding to the engine speed and the accelerator opening. Calculate the opening.
The CPU 351 applies drive power corresponding to the target EGR valve opening to the EGR valve 26. On the other hand, when it is determined that the EGR control execution condition as described above is not satisfied, the CPU 351 performs control to maintain the EGR valve 26 in the fully closed state.

Further, in the EGR control, the CPU 351
EGR valve 2 using intake air amount of internal combustion engine 1 as a parameter
The so-called EGR valve feedback control for performing feedback control of the opening degree of the valve 6 may be performed.

In the EGR valve feedback control, for example, the CPU 351 determines the target intake air amount of the internal combustion engine 1 using the accelerator opening, the engine speed, and the like as parameters. At this time, the relationship between the accelerator opening, the engine speed, and the target intake air amount may be mapped in advance, and the target intake air amount may be calculated from the map, the accelerator opening, and the engine speed. .

When the target intake air amount is determined by the above procedure, the CPU 351 reads out the output signal value (actual intake air amount) of the air flow meter 11 stored in the RAM 353, and reads the actual intake air amount and the target intake air amount. Compare with air volume.

When the actual intake air amount is smaller than the target intake air amount, the CPU 351 closes the EGR valve 26 by a predetermined amount. In this case, the amount of EGR gas flowing into the intake branch pipe 8 from the EGR passage 25 decreases, and accordingly, the amount of EGR gas drawn into the cylinder 2 of the internal combustion engine 1 decreases. As a result, the cylinder 2 of the internal combustion engine 1
The amount of fresh air sucked in increases by the amount of the decrease in the EGR gas.

On the other hand, when the actual intake air amount is larger than the target intake air amount, the CPU 351 opens the EGR valve 26 by a predetermined amount. In this case, the amount of EGR gas flowing into the intake branch pipe 8 from the EGR passage 25 increases, and accordingly, the amount of EGR gas drawn into the cylinder 2 of the internal combustion engine 1 increases. As a result, the amount of fresh air sucked into the cylinder 2 of the internal combustion engine 1 decreases by an amount corresponding to the increase in the EGR gas.

In addition, in the reducing agent addition control, the CPU 351
First, it is determined whether or not the reducing agent addition condition is satisfied. As the reducing agent addition conditions, for example, the storage reduction type NOx catalyst is in an active state, the output signal value (exhaust temperature) of the exhaust temperature sensor 24 is equal to or lower than a predetermined upper limit, or the SOx reduction of the storage reduction type NOx catalyst. Conditions such as the poisoning elimination control not being executed to recover poison or PM poisoning of the particulate filter 20 can be exemplified.

When the CPU 351 determines that the reducing agent addition condition described above is satisfied, the storage reduction type N
The flow control valve 30 is controlled so that the air-fuel ratio of the exhaust gas flowing into the Ox catalyst becomes a stoichiometric air-fuel ratio or a rich air-fuel ratio spikes in a relatively short cycle, and the nitrogen oxides stored in the storage-reduction NOx catalyst ( NOx) is released and reduced in a short period.

At this time, the CPU 351 reads the engine speed, the accelerator opening, the intake air amount, the fuel injection amount (fuel injection time), etc. stored in the RAM 353. CPU
351 accesses the flow control valve control map in the ROM 352 and calculates the valve opening timing of the flow control valve 30 corresponding to the above-described engine speed, accelerator opening, intake air amount, and fuel injection amount. The CPU 351 opens the flow control valve 30 according to the valve opening timing.

In this case, the high-pressure fuel discharged from the fuel pump 6 is supplied through the reducing agent supply passage 29 to the reducing agent injection valve 28.
, Whereby the pressure of the fuel applied to the reducing agent injection valve 28 increases. When the pressure of the fuel applied to the reducing agent injection valve 28 reaches or exceeds the valve opening pressure, the reducing agent injection valve 28 opens to inject fuel as a reducing agent into the exhaust branch pipe 18.

The reducing agent injected from the reducing agent injection valve 28 into the exhaust branch pipe 18 mixes with the exhaust gas flowing from the upstream of the exhaust branch pipe 18 to form an exhaust gas having a stoichiometric air-fuel ratio or a rich air-fuel ratio. The exhaust gas having the stoichiometric air-fuel ratio or rich air-fuel ratio flows into the NOx storage reduction catalyst.

As described above, when exhaust gas having a stoichiometric air-fuel ratio or a rich air-fuel ratio flows into the NOx storage reduction catalyst, the nitrogen oxides (NOx) stored in the NOx storage reduction catalyst are reduced.
Is released and is reduced to nitrogen (N ₂ ) or the like.

Next, the poisoning elimination control which is the gist of the present invention will be described.

In the exhaust system of the internal combustion engine 1 according to the present embodiment, a particulate filter 20 carrying a storage-reduction NOx catalyst is disposed, but the particulate filter 20 has only a limited PM trapping ability. Because there is a PM
When particulate matter having a trapping ability or more is trapped in the particulate filter 20, the exhaust passage in the particulate filter is clogged, and a problem such as an excessive rise in back pressure is induced. PM poisoning occurs.

Further, the fuel of the internal combustion engine 1 sometimes contains a sulfur (S) component. When such a fuel is burned in the internal combustion engine 1, the sulfur (S) component in the fuel is oxidized. since the sulfur oxides such as SO ₂ and SO ₃ (SOx) is formed by, it will include sulfur oxides (SOx) in the exhaust gas of the internal combustion engine 1.

When exhaust gas containing sulfur oxide (SOx) flows into the particulate filter 20, the sulfur oxide (SOx) is absorbed by the NOx storage reduction catalyst by the same mechanism as that of nitrogen oxide (NOx). Sulfur oxides absorbed in the NOx storage reduction catalyst (SOx), in order to form a stable barium sulfate (BaSO ₄₎ over time, thereby simply reduce the oxygen concentration of the exhaust flowing into the NOx storage reduction catalyst It is difficult to decompose and release alone
It is likely to be accumulated in the NOx storage reduction catalyst.

When the amount of SOx stored in the NOx storage reduction catalyst increases, the NOx absorption capacity of the NOx storage reduction catalyst decreases, so that nitrogen oxides (NOx) in the exhaust gas cannot be sufficiently removed. SOx poisoning occurs.

Therefore, the PM poisoning of the particulate filter 20 is eliminated before the back pressure rises excessively, and the SOx of the NOx storage reduction catalyst is reduced before the NOx absorption capacity of the NOx storage reduction catalyst excessively decreases. Poisoning needs to be eliminated.

As a method of eliminating PM poisoning of the particulate filter 20, the particulate filter 2 is used.
0 is raised to a high temperature range of about 500 ° C. to 700 ° C., and the air-fuel ratio of the exhaust gas flowing into the particulate filter 20 is set to a lean air-fuel ratio, thereby oxidizing (burning) particulate matter (PM). An example of a method for performing the above can be given.

On the other hand, as a method of eliminating SOx poisoning of the NOx storage reduction catalyst, the temperature of the NOx storage reduction catalyst is raised to a high temperature range of about 500 ° C. to 700 ° C. By setting the air-fuel ratio of the inflowing exhaust gas to the rich air-fuel ratio, barium sulfate (BaSO ₄ ) absorbed by the NOx storage reduction catalyst is converted to SO ₃ ^−.
And SO ₄ ^- in pyrolyzing, then SO ₃ ^- and SO ₄ ^- is reacted with hydrocarbons (HC) and carbon monoxide in the exhaust gas (CO) gaseous SO ₂ ^- illustrates a method for reducing the be able to.

As described above, when eliminating SOx poisoning and PM poisoning of the particulate filter 20, it is necessary to raise the temperature of the particulate filter 20 to a high temperature range of 500 ° C. or more. It is conceivable to perform the SOx poisoning elimination process or the PM poisoning elimination process during a high-load / high-rotation operation in which the exhaust gas temperature increases. However, when the internal combustion engine 1 is in a high-load / high-speed operation state, the amount of exhaust discharged from the internal combustion engine 1 per unit time increases, so that the air-fuel ratio of the exhaust is set to the rich air to eliminate SOx poisoning. When setting the fuel ratio, a large amount of fuel corresponding to the displacement is required, and there is a problem that the fuel consumption increases.

On the other hand, during idling operation when the amount of exhaust gas discharged from the internal combustion engine 1 per unit time decreases,
It is conceivable that SOx poisoning is eliminated by heating the particulate filter 20 and controlling the air-fuel ratio of the exhaust gas flowing into the particulate filter 20 to be richer than the stoichiometric air-fuel ratio. However, when the internal combustion engine 1 is in the idling operation state, the flow rate of exhaust gas discharged from the internal combustion engine 1 per unit time, in other words, the flow rate of exhaust gas flowing into the particulate filter 20 per unit time decreases. Accordingly, the amount of the reducing agent supplied to the particulate filter 20 per unit time is also reduced, so that there is a problem that it takes time until the SOx poisoning is eliminated.

In response to the various problems described above, in the poisoning elimination control according to the present embodiment, if it becomes necessary to eliminate PM poisoning of the particulate filter 20, the deceleration operation state of the internal combustion engine 1 is detected. Under such a condition, the SOx poisoning elimination process of the NOx storage reduction catalyst is executed in addition to the PM poisoning elimination process of the particulate filter 20.

That is, when it becomes necessary to eliminate the PM poisoning of the particulate filter 20, the CPU 351 triggers the shift of the operation state of the internal combustion engine 1 from the steady operation state or the acceleration operation state to the deceleration operation state. In addition, the PM poisoning elimination process of the particulate filter 20 and the SOx poisoning elimination process of the NOx storage reduction catalyst are executed.

Specifically, as shown in FIG. 5, when the accelerator opening (accelerator position) is fully closed (accelerator position is 0%) and the operation state of the internal combustion engine 1 shifts to the deceleration operation state, the CPU 351 sets First, in order to increase the bed temperature of the particulate filter 20 and the NOx storage reduction catalyst, secondary fuel is post-injected from the fuel injection valve 3 during the expansion stroke of each cylinder 2 and exhaust gas is discharged from the reducing agent injection valve 28. Add fuel into it.

At this time, the CPU 351 feeds back the post-injection fuel amount and the added fuel amount based on the output signal value of the exhaust gas temperature sensor 24 in order to prevent an excessive bed temperature of the particulate filter 20 and the NOx storage reduction catalyst. You may make it control.

Subsequently, the CPU 351 sets the storage reduction type NO
The SOx poisoning elimination process of the x catalyst (SOx poisoning recovery operation) is executed for a first predetermined time. In the SOx poisoning elimination process, the CP
U351 controls the amount of post-injected fuel from the fuel injection valve 3 and the amount of added fuel from the reducing agent injection valve 28 so that the air-fuel ratio of the exhaust gas flowing into the particulate filter 20 becomes a rich air-fuel ratio. At that time, the CPU 351 may perform feedback control of the post-injection fuel amount and the added fuel amount based on the output signal of the air-fuel ratio sensor 35.

Further, the CPU 351 executes the PM poisoning elimination process (PM poisoning recovery operation) of the particulate filter 20 for a second predetermined time after the first predetermined time has elapsed. In the PM poisoning elimination process, the CPU 351
Controls the post-injection fuel amount and the added fuel amount so that the air-fuel ratio of the exhaust gas flowing into the particulate filter 20 becomes a weak lean air-fuel ratio.

The CPU 351 terminates the post-injection from the fuel injection valve 3 and the addition of fuel from the reducing agent injection valve 28 after the second predetermined time has elapsed.

Here, the first predetermined time and the second
May be a fixed value set in advance,
The variable value may be changed according to the operation history of the internal combustion engine 1.

In general, when the internal combustion engine 1 is in a deceleration operation state, when a predetermined fuel cut condition is satisfied, the injection of the main fuel from the fuel injection valve 3 is prohibited, that is, a so-called deceleration fuel cut control is executed. That is, it is preferable to prohibit the execution of the deceleration fuel cut control during the execution period of the SOx poisoning elimination process and the PM poisoning elimination process as described above.

This is because, when the deceleration fuel cut control is executed during the execution period of the SOx poisoning elimination process and the PM poisoning elimination process, the low-temperature fresh air sucked into the internal combustion engine 1 is directly discharged as exhaust gas. This is because the particulate filter 20 and the NOx storage reduction catalyst are unnecessarily cooled by the low-temperature exhaust gas.

In the SOx poisoning elimination process and the PM poisoning elimination process, the CPU 351 executes the EGR valve 2
It is preferable to perform control so as to increase the opening degree of the intake throttle valve 6 and decrease the opening degree of the intake throttle valve 13.

This is because the amount of fresh air sucked into the internal combustion engine 1 is reduced, thereby suppressing an increase in the amount of post-injected fuel and the amount of added fuel, and suppressing a decrease in exhaust gas temperature due to low-temperature fresh air. That's why.

When the PM poisoning elimination process and the SOx poisoning elimination process are executed on the condition that the deceleration operation state of the internal combustion engine 1 is detected, the internal combustion engine 1 as well as the deceleration operation period are executed. 1 shifts to the idle operation state after the deceleration operation state, the PM poisoning elimination processing and S
Since the Ox poisoning elimination process is executed, it is possible to sufficiently secure the execution periods of the PM poisoning elimination process and the SOx poisoning elimination process.

Hereinafter, the poisoning elimination control according to the present embodiment will be specifically described. In the poisoning elimination control, the CPU 3
51 executes a poisoning elimination control routine as shown in FIG. This poisoning elimination control routine is performed in advance by R
This is a routine stored in the OM 352,
51 is a routine that is repeatedly executed every predetermined time (for example, every time the crank position sensor 33 outputs a pulse signal).

In the poisoning elimination control routine, the CPU 351
First, in step S601, the back pressure acting on the internal combustion engine 1: detecting a P _X. The back pressure: P _X changes according to the engine speed of the internal combustion engine 1 and the opening of the intake throttle valve 13,
The engine speed and the opening of the intake throttle valve 13 may be estimated as parameters.

In step S602, the CPU 351 executes the processing in step S6.
01 at the detected back pressure criteria from P _X back pressure: P _X0 subtraction to values obtained (P _X -P _X0) is a predetermined value: to determine whether P _S is greater than or not. The reference back pressure: P _X0 is under the same conditions as the back pressure: P _X (for example, when the engine speed and the opening of the intake throttle valve 13 are the same), and the particulate filter 20 Pressure when no particulate matter (PM) is trapped.
It is stored in the OM 352.

In S602, the value (P _X −) obtained by subtracting the reference back pressure: P _X0 from the back pressure: P _X.
P _X0 ) is determined to be equal to or less than the predetermined value: P _S ,
The CPU 351 determines the PM of the particulate filter 20.
Assuming that the degree of poisoning is within the allowable range, the execution of this routine is temporarily terminated.

On the other hand, in S602, the back pressure: P
Wherein the _X reference back pressure value obtained by subtracting the P _X0 (P _X -
P _X0 ) is determined to be larger than the predetermined value: P _S ,
The CPU 351 determines the PM of the particulate filter 20.
It is considered that the degree of poisoning is beyond the allowable range, and S60
Proceed to 3.

In S603, the CPU 351 determines whether or not the operation state of the internal combustion engine 1 is in the deceleration operation state or the idle operation state.

If it is determined in step S603 that the operation state of the internal combustion engine 1 is not the deceleration operation state or the idle operation state, the CPU 351 terminates the execution of this routine.

If it is determined in step S603 that the operation state of the internal combustion engine 1 is in the deceleration operation state or the idle operation state, the CPU 351 proceeds to step S604, and proceeds to S604.
The SOx poisoning elimination flag storage area set in advance in 353 is accessed, and it is determined whether or not “1” is stored in the SOx poisoning elimination flag storage area.

The SOx poisoning elimination flag storage area is
This is an area in which “1” is set when the execution of the Ox poisoning elimination process ends, and “0” is reset when the execution of the PM poisoning elimination process ends.

If it is determined in step S604 that "1" is not stored in the SOx poisoning elimination flag storage area, that is, if the execution of the SOx poisoning elimination process is not completed, the CPU 351 proceeds to step S605. Then, the SOx poisoning elimination process of the NOx storage reduction catalyst is executed.

In the SOx poisoning elimination process, the CPU 35
As described in the description of FIG. 5, first, during the expansion stroke of each cylinder 2, the temperature of the exhaust gas is increased by performing post-injection from the fuel injection valve 3, and the exhaust gas is discharged from the reducing agent injection valve 28 into the exhaust gas. By adding the fuel, the fuel is burned by the NOx storage reduction catalyst, thereby increasing the bed temperature of the particulate filter 20 and the NOx storage reduction catalyst.

Subsequently, the CPU 351 sets the air-fuel ratio sensor 3
5, the post-injection fuel amount and the added fuel amount are feedback-controlled so that the air-fuel ratio of the exhaust gas flowing into the NOx storage reduction catalyst becomes a desired rich air-fuel ratio suitable for SOx poisoning elimination. I do. Further, the CPU 351
Increases the opening of the EGR valve 26 and decreases the opening of the intake throttle valve 13 in order to reduce the amount of fresh air sucked into the internal combustion engine 1.

In this case, the air-fuel ratio of the exhaust gas flowing into the NOx storage reduction catalyst becomes a rich air-fuel ratio under the condition that the bed temperature of the NOx storage reduction catalyst becomes high.
Barium sulfate absorbed in the Ox catalyst (BaSO ₄₎ is SO ₃ ^- and SO ₄ ^- are pyrolyzed, their SO ₃ ^- and SO ₄ ^-
There react with hydrocarbons (HC) and carbon monoxide in the exhaust gas (CO) gaseous SO ₂ ^- will be reduced to.

[0175] When the execution of the SOx poisoning recovery process is started in the S605, CPU 351 is, SOx poisoning recovery timer in S606: Launch the T _1, thereby counting the execution time of the SOx poisoning recovery process.

In S607, the CPU 351 sets the SO
x poisoning recovery timer: counting time T ₁ is the first predetermined time: T
_S or higher, that is, the SOx poisoning elimination process is the first
It is determined whether the process has been executed for a predetermined time or more.

If it is determined in S607 that the measured time of the SOx poisoning elimination timer: T ₁ is less than the first predetermined time: T _S , the CPU 351 proceeds to S6.
Returning to 03, it is determined whether the deceleration operation state or the idle operation state of the internal combustion engine 1 is continued.
If the CPU 351 determines in S603 that the deceleration operation state or the idle operation state of the internal combustion engine 1 is continued, the processing from S604 is executed again, and the processing in S603 is performed.
If it is determined that the internal combustion engine 1 is not in the deceleration operation state or the idle operation state in S 614, the process proceeds to S 614, the execution of the SOx poisoning elimination process is stopped, and the time of the SOx poisoning elimination timer: T ₁ is set to “0” To end the execution of this routine.

On the other hand, if it is determined in S607 that the measured time of the SOx poisoning elimination timer: T ₁ is equal to or longer than the first predetermined time: T _S , that is, the execution time of the SOx poisoning elimination processing is the first time. If it is determined that the predetermined time has exceeded T _S , the CPU 351 determines that SOx poisoning of the NOx storage reduction catalyst has been eliminated, and proceeds to S608.

In S608, the CPU 351 reads the RAM3
The SOx poisoning elimination flag storage area 53 is accessed, and the value of the SOx poisoning elimination flag storage area is changed from “0” to “1”.
Rewrite to

In S609, the CPU 351 starts executing the PM poisoning elimination processing of the particulate filter 20. In the PM poisoning elimination processing, the CPU 351 sets the opening degree of the EGR valve 26 and the opening degree of the intake throttle valve 13 in the same manner as in the above-described SOx poisoning elimination processing, as described in the description of FIG. The post-injection fuel amount and the added fuel amount are controlled such that the air-fuel ratio of the exhaust gas flowing into the particulate filter 20 becomes a weak lean air-fuel ratio while maintaining the air-fuel ratio.

In this case, the particulate filter 20
Because the air-fuel ratio of the exhaust flowing into the air becomes a weak lean air-fuel ratio,
Unburned fuel components remaining in the exhaust gas (for example, hydrocarbons (H
C)) is combusted by the NOx storage reduction catalyst, and the heat generated at that time keeps the temperature of the particulate filter 20 at a high temperature. When the exhaust gas having a low lean air-fuel ratio flows into the particulate filter 20 under the condition that the temperature of the particulate filter 20 is maintained at a high temperature, the particulate matter (PM) trapped in the particulate filter 20 Will be oxidized (burned).

[0182] When the execution of the PM poisoning recovery process is started in the S609, CPU 351 may, PM poisoning recovery timer in S610: Launch the T _2, thereby counting the execution time of the PM poisoning recovery process.

In S611, the CPU 351 sets the PM
Poisoning recovery timer: counting time T ₂ is the second predetermined time: T _P
Whether or not the above is true, that is, the SOx poisoning elimination process is the second
It is determined whether the process has been executed for a predetermined time or more.

[0184] wherein the PM poisoning recovery timer in S611: counting time T ₂ is the second predetermined time: If it is determined to be less than T _P, CPU 351 is described above S60
Returning to step 3, it is determined whether the deceleration operation state or the idle operation state of the internal combustion engine 1 is continued.

If it is determined in S603 that the deceleration operation state or the idling operation state of the internal combustion engine 1 is continued, the CPU 351 executes the processing after S604 again. At that time, the CPU 351 determines that “1” is stored in the SOx poisoning elimination flag storage area in S604, and thus skips the processing in S605 to S608 and executes the processing in and after S609 again. become.

When it is determined in S603 that the internal combustion engine 1 is not in the deceleration operation state or the idle operation state,
CPU351 proceeds to S614, to cancel the execution of the PM poisoning recovery processing, PM poisoning recovery timer: T ₂ of the measurement time is reset to "0", the value of the SOx poisoning recovery flag storage area " Reset to "0".

[0187] On the other hand, the PM poisoning recovery timer in the S611: counting time T ₂ is the second predetermined time: If it is determined that the T _P or more, i.e., the execution time of the PM poisoning recovery process first second predetermined time: If it is determined reaches or exceeds T _P, CPU 351 considers the PM poisoning of the particulate filter 20 has been eliminated, the process proceeds to S612.

In S612, the CPU 351 terminates the execution of the PM poisoning elimination process. Specifically, the CPU 351
Controls the fuel injection valve 3 to stop the post-injection and controls the flow control valve 30 to stop the addition of fuel from the reducing agent injection valve 28.

[0189] In S613, the CPU 351 sets the RAM 3
The SOx poisoning elimination flag storage area 53 is accessed, and the value of the SOx poisoning elimination flag storage area is changed from “1” to “0”.
Rewrite to The CP that has completed the processing of S613
U351 terminates the execution of this routine.

By executing the poisoning elimination control routine by the CPU 351 in this way, the poisoning elimination means according to the present invention is realized.

In the embodiment described above, the storage reduction type N
SOx of particulate filter carrying Ox catalyst
The poisoning elimination process and the PM poisoning elimination process are executed when the internal combustion engine 1 is in the deceleration operation state and in the idling operation state.
It becomes easy to secure the execution period of the poisoning elimination process.

Further, in the exhaust gas purifying apparatus for an internal combustion engine according to the present embodiment, when the SOx poisoning elimination processing and the PM poisoning elimination processing are executed, the opening degree of the intake throttle valve 13 is reduced and the EGR valve is reduced. 26, the internal combustion engine 1
Since the flow rate of exhaust gas discharged per unit time from is reduced, the amount of post-injected fuel and the amount of added fuel for the purpose of setting the air-fuel ratio of exhaust gas to a rich air-fuel ratio can be reduced.

Therefore, according to the exhaust gas purifying apparatus for an internal combustion engine according to the present embodiment, the particulate filter and the NOx storage-reduction type are controlled while suppressing an increase in fuel consumption for eliminating SOx poisoning and PM poisoning. PM poisoning of catalyst and SOx
Poisoning can be eliminated.

<Embodiment 2> Next, a second embodiment of the exhaust gas purifying apparatus for an internal combustion engine according to the present invention will be described with reference to FIGS.
A description will be given based on FIG. Here, a configuration different from that of the above-described first embodiment will be described, and a description of a similar configuration will be omitted.

The difference between the first embodiment and the present embodiment is that the deceleration torque is positively generated when the processing for eliminating the poisoning of the particulate filter 20 and the NOx storage reduction catalyst is performed. On the point.

This is based on the assumption that the execution of the deceleration fuel cut control is prohibited while the poisoning elimination processing of the particulate filter 20 and the NOx storage reduction catalyst is being executed.

If the execution of the deceleration fuel cut control is prohibited during the execution of the particulate filter 20 and the poisoning elimination processing, the fuel is burned in the internal combustion engine 1, so that the torque of the internal combustion engine 1 becomes unnecessary. , And as a result, the deceleration performance of the vehicle may be reduced.

On the other hand, in the case where the execution of the deceleration fuel cut control is prohibited and the processing for eliminating the poisoning of the particulate filter 20 and the NOx storage reduction catalyst is executed, if the deceleration torque is generated, the deceleration is reduced. Since the increase in the torque of the internal combustion engine 1 due to the prohibition of the execution of the fuel cut control is offset by the deceleration torque,
The deceleration performance of the vehicle does not decrease. as a result,
It is possible to eliminate the poisoning of the particulate filter 20 and the NOx storage reduction catalyst without reducing the deceleration performance of the vehicle.

Next, a method for positively generating a deceleration torque when the processing for eliminating poisoning of the particulate filter 20 and the NOx storage reduction catalyst is being executed will be described.

As a method for generating the deceleration torque, a method for reducing the torque itself generated by the internal combustion engine 1, a method for increasing the braking force of a braking device provided in a vehicle on which the internal combustion engine 1 is mounted, or the above-described method. Although a method of appropriately combining the two can be exemplified, here, a method of reducing the torque itself generated by the internal combustion engine 1 will be described.

When the torque itself generated by the internal combustion engine 1 is to be reduced, the CPU 351 advances the injection timing of the main fuel from the fuel injection valve 3 before the top dead center of the compression stroke, preferably to the middle of the compression stroke. Corner.

If the main fuel is injected in the middle of the compression stroke, the fuel will burn in the middle of the compression stroke.
As shown in FIG. 7, the pressure in the cylinder 2 has a maximum value (hereinafter, referred to as a maximum in-cylinder pressure) before the top dead center of the compression stroke.

In this case, the maximum in-cylinder pressure described above is
The lifting operation of a piston (not shown) in the inside is hindered. For this reason, the internal combustion engine 1 performs a negative work of raising the piston to the top dead center in the compression stroke against the maximum in-cylinder pressure.

As a result, even if fuel is burned in the internal combustion engine 1 by prohibiting the execution of the deceleration fuel cut control, the torque of the internal combustion engine 1 does not increase unnecessarily.

In the above description of FIG. 6, an example has been described in which the main fuel is supplied into the cylinder 2 by one fuel injection. However, the main fuel is supplied into the cylinder 2 by two fuel injections. For example, when part of the main fuel to be supplied into the cylinder 2 is injected in a pilot manner, and when the pilot injected fuel is ignited, the remaining main fuel is main injected, As shown in FIG. 8, the CPU 351 may advance both the pilot injection timing and the main injection timing to the middle of the compression stroke.

When the injection of the main fuel is advanced to generate the deceleration torque, the CPU 351 determines whether the exhaust gas (EGR gas) is recirculated from the exhaust branch pipe 18 to the intake branch pipe 8.
The EGR valve 26 may be controlled so as to increase the amount of EGR.

Here, the exhaust gas as the EGR gas contains an inert gas component such as carbon dioxide (CO ₂ ) or water (H ₂ O) which does not burn itself and has an endothermic property, such as carbon dioxide (CO ₂ ) and water (H ₂ O). Therefore, when the EGR gas is supplied into the cylinder 2, the combustion temperature in the cylinder 2 is reduced. As a result, the maximum in-cylinder pressure decreases, and it becomes easy to generate a deceleration torque.

As described above, in the exhaust gas purifying apparatus for an internal combustion engine according to the present embodiment, when the particulate filter 20 and the occlusion reduction type NOx catalyst are subjected to the poisoning elimination process, the particulate filter 20 and the occlusion reduction type Nx catalyst are removed.
Even if the execution of the deceleration fuel cut control is prohibited in order to suppress the decrease in the temperature of the Ox catalyst, unnecessary increase in torque of the internal combustion engine 1 can be suppressed, so that the deceleration performance of the vehicle does not decrease.

Therefore, according to the exhaust gas purifying apparatus for an internal combustion engine in the present embodiment, it is possible to preferably eliminate the poisoning of the particulate filter 20 and the NOx storage reduction catalyst without deteriorating the deceleration performance of the vehicle. It becomes possible.

[0210]

In the exhaust gas purifying apparatus for an internal combustion engine according to the present invention, if it becomes necessary to eliminate the poisoning of the particulate filter carrying the NOx absorbent by the oxide and / or the particulate matter, On the condition that the deceleration operation state of the engine is detected, the processing for eliminating poisoning of the particulate filter is executed. In such a case, the poisoning elimination process is executed not only during the deceleration operation period but also during the idle operation period, and it is easy to secure the execution period of the poisoning elimination process.

Further, in the exhaust gas purifying apparatus for an internal combustion engine according to the present invention, the processing for eliminating poisoning by the oxide of the particulate filter carrying the NOx absorbent and the processing for eliminating poisoning by the particulate matter are performed by the internal combustion engine. This is executed during the deceleration operation or the idling operation in which the amount of exhaust gas discharged from the engine is relatively small, so that it is possible to suppress an increase in fuel consumption related to the poisoning elimination process.

Therefore, according to the exhaust gas purifying apparatus for an internal combustion engine according to the present invention, it becomes necessary to eliminate the poisoning of the particulate filter carrying the NOx absorbent by the oxide and the particulate matter. In addition, it is possible to reliably eliminate poisoning of the particulate filter while suppressing an increase in fuel consumption associated with the poisoning elimination process.

In the exhaust gas purifying apparatus for an internal combustion engine according to the present invention, if the deceleration torque generating means generates a desired deceleration torque when the process for eliminating poisoning of the particulate filter is performed, the particulate filter may be used. Even if combustion is performed in the internal combustion engine to suppress the temperature decrease of the vehicle, a decrease in the deceleration performance of the vehicle equipped with the internal combustion engine can be suppressed.

[Brief description of the drawings]

FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine to which an abnormality detection device for a reducing agent supply device according to the present invention is applied and an intake and exhaust system thereof.

2A is a front view of the particulate filter, and FIG. 2B is a cross-sectional view of the particulate filter.

FIG. 3A is a diagram illustrating the NOx storage mechanism of the NOx storage reduction catalyst; FIG. 3B is a diagram illustrating the NOx release mechanism of the NOx storage reduction catalyst;

FIG. 4 is a block diagram showing an internal configuration of an ECU.

FIG. 5 is a diagram illustrating poisoning elimination control according to the embodiment;

FIG. 6 is a flowchart showing a poisoning elimination control routine.

FIG. 7 is a diagram (1) showing the relationship between the injection timing of the main fuel and the in-cylinder pressure in the second embodiment.

FIG. 8 is a diagram (2) showing the relationship between the injection timing of the main fuel and the in-cylinder pressure in the second embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine 2 ... Cylinder 3 ... Fuel injection valve 4 ... Common rail 5 ... Fuel supply pipe 6 ... Fuel pump 13 ... Throttle valve 18 ... exhaust branch pipe 19 ... exhaust pipe 20 ... particulate filter 21 ... exhaust throttle valve 25 ... EGR passage 26 ... EGR valve 27 ... EGR cooler 28 ... reducing agent Injection valve 29 ... Reducing agent supply path 30 ... Flow regulating valve 31 ... Shutoff valve 32 ... Reducing agent pressure sensor 33 ... Crank position sensor 34 ... Water temperature sensor 35 ... ECU 351 ..CPU 352..ROM 353..RAM 354..backup RAM

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F01N 3/28 F01N 3/28 A 3G301 3/36 3/36 BR R F02D 21/08 301 F02D 21/08 301B 301D 41/12 360 41/12 360 380 380A 41/38 41/38 B 41/40 41/40 C 43/00 301 43/00 301K 301N 301C 301T F02M 25/07 570 F02M 25/07 570J (72G ) Inventor Masaaki Kobayashi 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Co., Ltd. 1 Toyota Town, Toyota City (72) Inventor Hisashi Ohki Toyota Town, Toyota City, Aichi Prefecture 1 Toyota Motor Corporation (72) Inventor Daisuke Shibata 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Corporation (72) Inventor Akihiko Negami 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Corporation (72) Inventor Tomohisa Oda 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation (72) Inventor Yasuo Harada 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation (72) Inventor Yasuhiko Otsubo Aichi 1 Toyota Town, Toyota City F-term (reference) in Toyota Motor Corporation 3G062 AA01 AA05 BA00 BA04 BA05 CA03 CA05 DA01 EA12 ED08 FA08 GA02 GA05 GA06 GA08 GA09 GA12 GA15 GA17 GA21 3G084 AA01 BA05 BA09 BA13 BA15 BA17 BA19 BA20 BA24 CA03 CA06 DA00 DA02 DA10 EB06 EB08 EB11 FA00 FA07 FA10 FA11 FA20 FA27 FA29 FA38 3G090 AA01 BA01 CB04 CB07 CB25 DA09 DB03 DB07 EA06 EA07 3G091 AA02 AA11 AB04 AB06 AB13 BA11 BA33 CA01 CB02 CB03 EA07 EA07 DC10 EA3 1 EA34 FA12 FA19 FB10 FB12 FC01 FC05 GB03W GB06W HA14 HB05 3G092 AA01 AA02 AA06 BA01 BA07 BB01 BB06 BB08 BB13 DC01 DC09 DC12 DE03S EA05 EA07 EA21 EC01 FA24 FA37 GA13 GB08 HA01Z HA05X HA06Z HD05 HD03 HD05 HD03 HD05 HD03 HD05 HD02 JA21 JA24 JA25 JA26 JA33 KA16 KA18 LA03 LB01 LB04 LB11 LC01 MA01 MA12 MA14 MA18 MA23 MA24 NC01 NC02 ND01 NE13 NE15 PA01Z PA07A PA10A PA11Z PB00Z PB08A PD03A PD03Z PD09A PD09Z PD11Z PD12A PD14Z PE01Z03

Claims (12)

[Claims] 1. A nitrogen oxide provided in an exhaust passage of an internal combustion engine to absorb nitrogen oxides in the exhaust gas when the oxygen concentration of the inflowing exhaust gas is high, and to absorb nitrogen oxides in the exhaust gas when the oxygen concentration of the inflowing exhaust gas decreases. A particulate filter having a function of discharging the particulate filter, and when it is necessary to eliminate poisoning by the oxide and / or particulate matter of the particulate filter, when a deceleration operation state of the internal combustion engine is detected. ,
An exhaust gas purifying apparatus for an internal combustion engine, comprising: a poisoning elimination unit that executes a process for eliminating poisoning of the particulate filter. 2. The poisoning elimination means, when eliminating poisoning of the particulate filter by oxides and poisoning by particulate matter, sets an air-fuel ratio of exhaust gas flowing into the particulate filter to a second value. The exhaust gas purification apparatus for an internal combustion engine according to claim 1, wherein the first predetermined period is a rich air-fuel ratio, and the second predetermined period is a lean air-fuel ratio. 3. An exhaust gas recirculation mechanism for recirculating a part of exhaust gas flowing through an exhaust passage of the internal combustion engine to an intake passage, wherein the poisoning eliminating means removes poisoning of the particulate filter by oxide. 2. The exhaust gas purifying apparatus for an internal combustion engine according to claim 1, wherein the exhaust gas recirculation mechanism is controlled so as to increase an amount of exhaust gas recirculated from the exhaust passage to the intake passage. 4. An intake throttle valve provided in an intake passage of the internal combustion engine for adjusting a flow rate of intake air flowing in the intake passage, wherein the poisoning eliminating means is configured to poison the particulate filter with oxide. 2. The exhaust gas purifying apparatus for an internal combustion engine according to claim 1, wherein the degree of opening of the intake throttle valve is reduced in order to solve the problem. 5. An exhaust gas recirculation mechanism for recirculating a part of exhaust gas flowing through an exhaust passage of the internal combustion engine to an intake passage, and adjusting a flow rate of intake air provided in the intake passage of the internal combustion engine and flowing through the intake passage. And a poisoning elimination means, wherein the poisoning eliminating means increases the amount of exhaust gas recirculated from the exhaust passage to the intake passage when eliminating poisoning by the oxide of the particulate filter. The exhaust gas purifying apparatus for an internal combustion engine according to claim 1, wherein the exhaust gas recirculation mechanism is controlled and the opening degree of the intake throttle valve is reduced. 6. A fuel injection valve for directly injecting fuel into a cylinder of the internal combustion engine, and an addition unit for adding fuel to an exhaust passage upstream of the particulate filter, wherein the poisoning elimination unit is provided. 3. An exhaust gas purifying apparatus for an internal combustion engine according to claim 2, wherein an air-fuel ratio of exhaust gas is controlled by controlling a sub-injection amount from said fuel injection valve and / or an addition amount from said adding means. 7. The exhaust system for an internal combustion engine according to claim 1, further comprising a deceleration torque generating means for generating a desired deceleration torque when the process for eliminating poisoning of the particulate filter is executed. Purification device. 8. The system according to claim 7, wherein the deceleration torque generating means reduces the generated torque of the internal combustion engine.
An exhaust gas purifying apparatus for an internal combustion engine according to claim 1. 9. The exhaust gas purifying apparatus for an internal combustion engine according to claim 8, wherein said deceleration torque generating means advances a fuel injection timing of said internal combustion engine. 10. An exhaust gas recirculation mechanism for recirculating a part of exhaust gas flowing through an exhaust passage of the internal combustion engine to an intake passage, wherein the deceleration torque generating means advances a fuel injection timing of the internal combustion engine. The exhaust gas recirculated by said exhaust gas recirculation mechanism is increased.
An exhaust gas purifying apparatus for an internal combustion engine according to claim 1. 11. A main fuel injection means for injecting main fuel for combustion into a cylinder of the internal combustion engine, and a pilot injection for injecting secondary fuel prior to main fuel injection by the main fuel injection means. 11. The internal combustion engine according to claim 9, further comprising: a deceleration torque generating unit that advances a fuel injection timing of the main fuel injection unit and the pilot injection unit. 12. Exhaust gas purification device. 12. The exhaust gas purifying apparatus for an internal combustion engine according to claim 7, wherein said deceleration torque generating means increases a braking force by a braking device for a vehicle equipped with said internal combustion engine.