JP2000145434A - Exhaust emission control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To supply an exhaust emission catalyst with a uniform volume of a reducing agent in its radial direction. SOLUTION: An NOx absorbent 17, which absorbs NOx when the air-fuel ratio of an inflowing exhaust gas is lean and discharges the absorbed NOx when the oxygen concentration of the inflowing exhaust decreases, is installed in an exhaust path of an engine. An oxidation catalyst 16 is installed in the exhaust path upstream of the NOx absorbent 17. To discharge and reduce NOx contained in the NOx absorbent 17, a reducing agent injection nozzle 21 that supplies the NOx absorbent 17 with a reducing agent is located in the exhaust path upstream from the oxidation catalyst 16. A microporous body 24 is mounted at the tip of the reducing agent injection nozzle 21. The reducing agent injected from the reducing agent injection nozzle 21 seeps through an entire peripheral surface of the microporous body 24, being supplied evenly in a radial direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an exhaust gas purifying apparatus for an internal combustion engine.

[0002]

2. Description of the Related Art An exhaust purification catalyst is disposed in an engine exhaust passage, and a reducing agent injection nozzle is disposed in an engine exhaust passage upstream of the exhaust purification catalyst, and a reducing agent is supplied from the reducing agent injection nozzle to the exhaust purification catalyst. An exhaust gas purifying apparatus for an internal combustion engine as described above is known (see Japanese Utility Model Laid-Open No. 5-1818). In this exhaust gas purification device, the impingement plate faces the injection port of the reducing agent injection nozzle to cause the reducing agent injected from the reducing agent injection nozzle to collide with the impingement plate, so that the reducing agent is uniformly diffused in the radial direction. ing.

[0003]

However, there is a problem that, for example, the reducing agent does not easily travel on the back side of the collision plate, and thus the reducing agent cannot be sufficiently diffused uniformly in the radial direction.

[0004]

According to a first aspect of the present invention, an exhaust purification catalyst is disposed in an engine exhaust passage, and a reducing agent is injected into an engine exhaust passage upstream of the exhaust purification catalyst. In an exhaust gas purifying apparatus for an internal combustion engine in which a nozzle is arranged and a reducing agent is supplied from a reducing agent injection nozzle to an exhaust gas purification catalyst, a porous body is arranged between the reducing agent injection nozzle and the exhaust gas purification catalyst. That is, in the first invention, the reducing agent injected from the reducing agent injection nozzle flows into the pores of the porous body and then flows out from the entire peripheral surface of the porous body, so that the reducing agent is uniformly distributed in the radial direction. Supplied.

According to a second aspect of the present invention, in the first aspect, one side of the pore body is disposed adjacent to the injection port of the reducing agent injection nozzle, and the other side of the pore body is located upstream of the exhaust gas purifying catalyst. It is disposed adjacent to the end face, and the reducing agent is injected from the reducing agent injection nozzle during the engine deceleration operation so that the reducing agent is temporarily stored in the pores. That is, during the engine acceleration operation, for example, a large amount of NO _X is released from the engine. On the other hand, when the engine is accelerated, the reducing agent stored in the pores flows out of the pores. Therefore, in the second invention, the reducing agent is temporarily stored in the pores during the engine deceleration operation,
Next, when the engine acceleration operation is performed, the exhaust gas is favorably purified.

According to a third aspect of the present invention, an exhaust purifying catalyst is disposed in an engine exhaust passage, and a reducing agent injection nozzle is disposed in an engine exhaust passage upstream of the exhaust purifying catalyst. In an exhaust gas purifying apparatus for an internal combustion engine in which a reducing agent is supplied from a reducing agent injection nozzle to an exhaust purification catalyst, a reducing agent injection nozzle is arranged such that a reducing agent injection direction of the reducing agent injection nozzle is opposed to an exhaust flow direction. are doing. That is, in the third aspect, since the reducing agent is injected opposite to the exhaust flow, the diffusion of the reducing agent in the radial direction is promoted.

[0007]

FIG. 1 shows a case where the present invention is applied to a diesel engine. However, the present invention can be applied to a spark ignition type engine. Referring to FIG. 1, 1 is an engine body, 2 is a combustion chamber, 3 is an intake port, 4 is an intake valve, 5 is an exhaust port, 6 is an exhaust valve, and 7 is fuel injection for directly injecting fuel into the combustion chamber 2. Each nozzle is shown.
The intake port 3 of each cylinder is connected to a common surge tank 9 via a corresponding intake branch pipe 8, and the surge tank 9 is connected to an air cleaner 11 via an intake duct 10. An intake control valve 13 driven by an actuator 12 is arranged in the intake duct 10. On the other hand, the exhaust port 5 of each cylinder is connected to a casing 18 which accommodates an oxidation catalyst 16 and _the NO _X absorbent 17 via a common exhaust manifold 14 and exhaust pipe 15, the casing 17 is connected to the exhaust pipe 19. The oxidation catalyst 16 and N
The O _X absorbent 17 can be arranged on a common carrier.

A reducing agent supply device 20 for supplying a reducing agent is provided in a casing 18 upstream of the oxidation catalyst 16. The reducing agent supply device 20 includes a plurality of, for example, three reducing agent injection nozzles 21 arranged in a direction transverse to the exhaust gas flow direction. These reducing agent injection nozzles 21 are connected to the discharge side of a reducing agent pump 23 via a common electromagnetic valve 22, and the suction side of the reducing agent pump 23 is connected to a reducing agent tank (not shown). The actuator 12, the solenoid valve 22, and the reducing agent pump 23 are connected to the electronic control unit 30.
Are controlled based on output signals from

FIG. 2 is an enlarged view around the leading end of the reducing agent injection nozzle 21. Referring to FIG. 2, a pore body 24 is provided between the reducing agent injection nozzle 21 and the oxidation catalyst 16. In the present embodiment, the injection port 21a of the reducing agent injection nozzle 21 is attached to one side surface of the porous body 24 by the holder 25, and the upstream end surface of the oxidation catalyst 16 is brought into contact with the other side surface of the porous body 24. . The porous body 24 is formed of, for example, a porous material such as ceramic or foamed plastic, or a fabric such as a woven fabric or a nonwoven fabric, and has a large number of continuous pores. The pores 24 and the reducing agent injection nozzle 21
A gap may be formed between the pores 24 or between the porous body 24 and the oxidation catalyst 16.

[0010] The reducing agent can be selected from hydrocarbons, hydrogen and alcohols and can be gaseous or liquid. In this embodiment, engine fuel (light oil) is used as the reducing agent. Thus, the reductant tank is formed from a fuel tank and does not require an additional reductant tank. The electronic control unit (ECU) 30 comprises a digital computer,
A ROM (read only memory) 32, a RAM (random access memory) 33, a CPU (microprocessor) 34, a B-RAM (backup RA) connected to a power source at all times via a bidirectional bus 31
M) 35, an input port 36, and an output port 37. A pressure sensor 38 for generating an output voltage proportional to the absolute pressure PM in the surge tank 9 is attached to the surge tank 9, and an output voltage proportional to the temperature of exhaust gas flowing out of the NO _X absorbent 17 is provided in the exhaust pipe 19. Is mounted. Temperature of the exhaust represents _the NO _X absorbent temperature TNA. Further, the depression amount sensor 40 generates an output voltage proportional to the depression amount DEP of the accelerator pedal. The output voltages of these sensors 38, 39, 40 are input to the input port 36 via the corresponding AD converters 41, respectively. The input port 36 has a rotation speed sensor 4 for generating an output pulse representing the engine rotation speed N.
2 are connected. On the other hand, the output port 37 is connected to the actuator 12, the electromagnetic valve 22, and the reducing agent pump 23 via the corresponding drive circuits 43, respectively.

The oxidation catalyst 16 accommodated in the casing 17 uses, for example, alumina as a carrier and carries a noble metal such as platinum Pt, palladium Pd, rhodium Rh, and iridium Ir. On the other hand, the NO _X absorbent 17 contained in the casing 18 downstream of the oxidation catalyst 16 uses, for example, alumina as a carrier, and, for example, potassium K,
At least one selected from the group consisting of alkali metals such as sodium Na, lithium Li and cesium Cs; alkaline earths such as barium Ba and calcium Ca; and rare earths such as lanthanum La and yttrium Y, and platinum Pt, palladium Pd and rhodium. Rh and a noble metal such as iridium Ir are supported. The ratio of the total air amount to the total fuel amount and the total reducing agent amount supplied into the exhaust passage, the combustion chamber, and the intake passage upstream of a certain position in the exhaust passage is determined by the air-fuel ratio of the exhaust flowing through the position. This N
O _X absorbent 17 absorbs NO _X when the air-fuel ratio of the exhaust gas flowing is lean, perform absorption and release action of the NO _X that releases NO _X to the oxygen concentration in the exhaust gas absorbed and reduced flowing. Note that matches the ratio of the air quantity for the air-fuel ratio is the amount of fuel supplied to the engine of the exhaust gas flowing to the NO _X absorbent 17 when the fuel or air to _the NO _X absorbent 17 in the exhaust passage upstream of is not supplied .

If the above-mentioned NO _X absorbent 17 is disposed in the engine exhaust passage, the NO _X absorbent 17 actually performs the NO _X absorption / release operation, but the detailed mechanism of this absorption / release operation is not clear. There is also. However, it is considered that this absorption / release action is performed by a mechanism as shown in FIGS. 3 (A) and 3 (B). Next, regarding this mechanism, platinum Pt and barium Ba are deposited on the carrier.
Will be described as an example in the case of carrying other precious metals,
The same mechanism is obtained by using an alkali metal, an alkaline earth, or a rare earth.

That is, when the inflowing exhaust gas becomes considerably lean, the oxygen concentration in the inflowing exhaust gas greatly increases.
As shown in (A), these oxygens O ₂ adhere to the surface of platinum Pt in the form of O ₂ ⁻ or O ²⁻ . On the other hand, NO in the exhaust gas that flows in reacts with O ₂ ⁻ or O ²⁻ on the surface of platinum Pt to become NO ₂ (2NO + O ₂ → 2NO ₂ ). Then part of the produced NO ₂ while bonding with the barium oxide BaO is absorbed into the absorbent while being further oxidized on the platinum Pt, 3 nitric acid as shown in (A) ions NO ₃ ^- in It diffuses into the absorbent in form. Thus N
O _X is absorbed in the NO _X absorbent 17.

[0014] NO ₂ is produced on the surface of the oxygen concentration is as high as platinum Pt in the inflowing exhaust gas, as long as NO ₂ to NO _X absorbing capacity of the absorbent is not saturated is absorbed in the absorbent and nitrate ions NO ₃ ^- Is generated. On the other hand, when the oxygen concentration in the exhaust gas that flows in decreases and the amount of generated NO ₂ decreases, the reaction proceeds in the reverse direction (NO ₃ ⁻ → NO ₂ ), and thus the nitrate ions NO ₃ ⁻ There are released from the absorbent in the form of NO _2. That is, when the oxygen concentration in the inflowing exhaust gas decreases _the NO _X absorbent as shown in FIG. 3 (B) 17
NO _X is to be released from the. The oxygen concentration in the exhaust gas lean degree of the exhaust gas flowing to flow the lower the lowered, thus NO _X from _the NO _X absorbent 17 when lowering the lean degree of the exhaust gas flowing is to be released.

Meanwhile, when supplying a reducing agent (HC) in this case _the NO _X absorbent 17 unburned H in the reducing agent and the exhaust
C and CO react with oxygen O ₂ ^- or O ^2- on platinum Pt to be oxidized. Also, the air-fuel ratio of the exhaust gas flowing to the NO _X absorbent 17 is supplied a certain amount of reducing agent to the NO _X absorbent 17 is a lean, because the oxygen concentration around the platinum Pt is lowered locally NO ₂ is released from the absorbent, and this NO ₂ is reduced by reacting with the reducing agent and unburned HC and CO as shown in FIG. 3 (B).
In this way, when NO ₂ is no longer present on the surface of platinum Pt, NO ₂ is released from the absorbent one after another. Accordingly, the air-fuel ratio of the exhaust gas flowing to the NO _X absorbent 17 be supplied a certain amount of reducing agent to the NO _X absorbent 17 is NO _X is released from _the NO _X absorbent 17 even lean, is released and NO _X is to be reduced.

In a diesel engine as shown in FIG.
Usually reduces smoke and particulates emitted from engines
Therefore, the average air-fuel ratio of the air-fuel mixture burned in the combustion chamber 2 is
It is maintained leaner than the stoichiometric air-fuel ratio. Therefore
NO during normal operation_XAir-fuel ratio of exhaust gas flowing into absorbent 17
Is lean, so the NO discharged from the engine at this time _X
Is NO_XAbsorbed by the absorbent 17.

However, NO_XNO of absorbent 17_Xabsorption
NO because the ability is limited_XNO of absorbent 17_Xabsorption
NO before capacity saturates_XNO from absorbent 17_XRelease
Need to be done. NO_XNO from absorbent 17_XRelease
NO to let_XWhen the reducing agent is supplied to the absorbent 17
NO_XNO of absorbent 17_XRelease rate, and NO_XReturn
Original reaction rate is NO_XDepends on the absorbent temperature TNA, but
NO_XNO of absorbent 17_XThe purification rate R is shown in FIG.
So no_XDepends on the absorbent temperature TNA. From FIG.
As you can see, NO_XAbsorbent temperature TNA is NO_XAbsorbent
It should be higher than the threshold temperature T1 determined according to the type of 17
NO_XPurification rate R is higher than allowable minimum purification rate R1
You. NO_XAbsorbent temperature TNA is equal to threshold temperature T1
NO when low _XIf it cannot be released and reduced
NO_XThe reducing agent supplied to the absorbent 17 is an acid
NO without being converted_XIt flows out of the absorbent 17.

[0018] Therefore, in the present embodiment, NO _X absorbent temperature TNA stops the reducing agent supply operation of the reducing agent supply device 20 when lower than the threshold temperature T1, NO _X absorbent temperature T
NA is a reducing agent supply operation of the reducing agent supply device 20 by a predetermined set time when it becomes higher than the threshold temperature T1 performed by releasing NO _X in _the NO _X absorbent 17, so as to reduce I have. The threshold temperature T1 is 150 to
About 230 ° C.

[0019] In this case, _the NO _X absorbent rapidly released air-fuel ratio of the exhaust gas flowing into the NO _X in _the NO _X absorbent 17 needs to supply the reducing agent so that the stoichiometric air-fuel ratio or rich to 17, reduced be able to. However, in order to make the air-fuel ratio of the exhaust gas flowing to the NO _X absorbent 17 in the diesel engine shown in FIG. 1 to the stoichiometric air-fuel ratio or rich requires a large amount of reducing agent, whereas, as described above NO _X air-fuel ratio of the exhaust gas flowing into the absorbent 17 is a lean NO _X in even _the NO _X absorbent 17 is released can be reduced. In this embodiment, NO in _the NO _X absorbent 17
_{When the} reducing agent supply operation is performed to release and reduce _X , the air-fuel ratio of the exhaust gas flowing into the NO _X absorbent 17 is kept lean.

The reducing agent supplied from the reducing agent supply device 20 first reaches the oxidation catalyst 16, where the reducing agent is partially oxidized, and then flows into the NO _x absorbent 17. As a result, N
Temperature of the exhaust gas flowing into the O _X absorbent 17 is raised, NO _X emission rate and the reduction rate of the NO _X absorbent 17 is kept high. Further, the oxygen concentration in the exhaust gas flowing to the NO _X absorbent 17 is made to decrease by the reducing agent is partially oxidized and further a reducing agent is made to more easily reacts with state NO _X, also NO _X by these Absorbent 17
NO _X emission rate and the reduction ratio of can be maintained high.

[0021] _the NO _X absorbent release the NO _X in the 17, only qN per unit time from the reducing agent supply device 20 reducing agent is supplied to the time to reduction. This qN is favorably emits NO _X in _the NO _X absorbent 17 while maintaining a small reducing agent consumption ratio is optimal amount of reducing agent to be reduced, are obtained by experiments in advance. qN is stored in the ROM 32 in advance in the form of a map shown in FIG. 5 as a function of the absolute pressure PM in the surge tank 9 and the engine speed N.

[0022] As described above, in this embodiment, releasing the NO _X in _the NO _X absorbent 17, the air-fuel ratio of the exhaust gas flowing to the NO _X absorbent 17 when to be reduced is a lean, NO _X oxygen concentration in the surface of the absorbent 17 is NO _X is released from _the NO _X absorbent 17 by reducing locally, it is reduced. Release of such NO _X, the reducing agent sufficiently vaporized in order to perform a reducing action effectively NO _X
Droplets having a large particle size rather than being supplied to the absorbent 17,
Alternatively, it has been found that it is preferable to supply the reducing agent in the form of a continuous stream. Further, the reducing agent when the reducing agent flowing into _the NO _X absorbent 17 is a small diameter is likely to pass through _the NO _X absorbent 17 without being oxidized to susceptible to exhaust gas flow.

[0023] Therefore, in the present embodiment, fitted with a pore 24 at the tip of the reducing agent injection nozzle 21, so as to supply the reducing agent to the oxidation catalyst 16 and _the NO _X absorbent 17 via the Hosoanatai 24 . That is, the reducing agent injection nozzle 21
The relatively small diameter reducing agent particles ejected from the fine particles travel inside the fine pores of the fine pores 24 while aggregating with each other, and as a result, flow out of the fine pores 24 in the form of droplets having a large particle diameter or a continuous flow. I do. This reducing agent is partially oxidized in the oxidation catalyst 16, flows into _the NO _X absorbent 17 while maintaining the shape of large droplets or continuous stream of particle size. Therefore, NO _X
NO _X in the absorbent 17 can be released and reduced effectively. The reducing agent is so fed to _the NO _X absorbent 17 in the form of large droplets or continuous flow of grain size, is prevented from flowing out of _the NO _X absorbent 17 without reducing agent is oxidized You.

Further, in this case, the reducing agent that has flowed in from one side surface of the porous body 24 oozes out from the entire remaining peripheral surface of the porous body 24, as indicated by arrows in FIG. Therefore, the reducing agent can be uniformly supplied in the radial direction, and N
NO _X in the O _X absorbent 17 can be uniformly released and reduced. However, increasing _the amount of NO _X is much the engine acceleration operation is discharged from the when the engine performed, this time NO _X
Air-fuel ratio of the exhaust gas flowing into the absorbent 17 is likely to flow out from _the NO _X absorbent 17 without NO _X even lean is absorbed.

Therefore, in the present embodiment, a small amount of reducing agent is injected from the reducing agent injection nozzle 21 during the engine deceleration operation to allow the reducing agent to soak into the micropores 24, and then the engine acceleration operation is performed. so that the reduction of large amounts of the NO _X with a reducing agent that is stored in the pores body 24 when the. That is, when the engine acceleration operation is performed, the temperature and pressure of the exhaust gas discharged from the engine increase, so that the pores 2
4 releases the stored reducing agent. This reducing agent then flows into the NO _x absorbent 17 to reduce a part of the NO _x in the exhaust gas, and thus a large amount of N _x
O _X is prevented from flowing out. With this configuration, the reducing agent can be supplied without delay when the amount of NO _X discharged from the engine increases.

It is to be noted that it is detected whether or not the engine acceleration operation has been performed, and when the engine acceleration operation has been performed, the reducing agent is injected from the reducing agent injection nozzle 21 to reduce the reduction stored in the pores 24. The agent may be extruded out of the pores 24, thereby providing a reducing agent. FIG. 7 shows a routine for calculating the reducing agent injection amount q injected from the reducing agent injection nozzle 21 per unit time. This routine is executed by interruption every predetermined set time.

Referring to FIG. 7, first, at step 50, it is determined whether or not a flag is set. This flag is set when the reducing agent is to be supplied from the reducing agent supply device 20, and is reset when the supply of the reducing agent is to be stopped. Flag routine goes to step 51 when it is reset, NO _X absorbent temperature TNA whether higher than the threshold temperature T1 is determined. TNA> T1
The routine goes to step 52, whether _the NO _X absorbent temperature TNA was a T1 or less in the last processing cycle is determined at the time of. T in the previous processing cycle
If NA> T1, then the routine proceeds to step 53, where it is determined whether or not the rate of change ΔDEP of the accelerator pedal depression amount DEP is smaller than a fixed value D1, that is, whether or not the engine is being decelerated. When ΔDEP ≧ D1, that is, when the engine deceleration operation is not being performed, the routine proceeds to step 62, where the reducing agent injection amount q is set to zero. That is, the reducing agent supply operation is stopped. On the other hand, when ΔDEP <D1, that is, when the engine is being decelerated, the routine proceeds to step 54, where the reducing agent injection amount q is set to, for example, a constant value qS. This qS is the pore 2
4 is an amount of the reducing agent necessary to optimize the amount of the reducing agent to be impregnated into the inside of the porous body 4, and therefore, a reducing agent supply operation for storing the reducing agent in the pores 24 is performed. On the other hand, in step 52, TNA ≦ T
When 1, i.e. _the NO _X absorbent temperature TNA proceeds to then step 55 when rises above the threshold temperature T1, the flag is set.

Step 5 when the flag is set
From 0, the process proceeds to step 56, where qN is calculated from the map of FIG. In the following step 57, the reducing agent injection amount q becomes qN
It is said. Therefore, a reducing agent supply action for releasing and reducing NO _X in the NO _X absorbent 17 is performed. In the following step 58, the counter value C representing the time during which the flag is set is incremented by one. In a succeeding step 59, it is determined whether or not the count value C is larger than the set value C1. When C ≦ C1, the processing cycle ends. When C> C1, it is determined that the reducing agent supply operation has been performed for a certain period of time, and the routine proceeds to step 60, where the flag is reset. In the following step 61, the counter value C is cleared, and in the following step 62, the reducing agent injection amount q becomes q
N. That is, the reducing agent supply operation is stopped.

FIG. 8 shows another embodiment of the reducing agent injection nozzle 21. In the present embodiment, the reducing agent injection nozzle 21 is arranged such that the reducing agent injection direction of the reducing agent injection nozzle 21 is parallel to the axis of the exhaust passage and faces the exhaust flow. As a result, the reducing agent injected from the reducing agent injection nozzle 21 collides with the exhaust gas to promote diffusion, and
Thus, the reducing agent can be uniformly supplied in the radial direction.

Furthermore, since the reducing agent injected at the beginning of the reducing agent injection period and the reducing agent injected at the end of the reducing agent injection period can flow together in the exhaust passage, an exhaust portion having a considerably high reducing agent concentration is formed. Can be. In other words, a pulse-like concentration distribution of the reducing agent can be formed. Such reducing agent concentration is high exhaust portion effectively releases NO _X in _the NO _X absorbent 17 when flowing into _the NO _X absorbent 17 can be reduced. Note that the reducing agent injection direction of the reducing agent injection nozzle 21 is not necessarily parallel to the exhaust passage axis.

FIG. 9 shows still another embodiment of the reducing agent injection nozzle 21. In the present embodiment, the reducing agent injection nozzle 21 includes an annular injection hole holder 26. The nozzle holder 26 is formed with a plurality of nozzles 21a arranged annularly, and these nozzles 21a are directed inward in the radial direction of the exhaust passage. Also in this embodiment, since the reducing agent injection direction of the reducing agent injection nozzle 21 intersects with the exhaust flow, the diffusion of the reducing agent is promoted, and thus the reducing agent can be uniformly supplied in the radial direction. . Further, since the reducing agent injection direction is directed inward in the radial direction of the exhaust passage, the amount of the reducing agent adhering to the inner wall surface of the exhaust passage is reduced.

[0032] In the embodiment described so far, the exhaust gas purifying catalyst formed from the oxidation catalyst 16 and _the NO _X absorbent 17 release the NO _X in _the NO _X absorbent 17, the reducing agent supply device for reducing 20 The present invention is applied to the case where the reducing agent is supplied from the apparatus. However, reduction to an exhaust gas purifying catalyst was formed to include a selective reduction catalyst capable of reducing the NO _X in the inflowing exhaust gas, to reduce NO _X in the selective reduction catalyst in an oxygen atmosphere containing a reducing agent The present invention can also be applied to a case where a reducing agent is supplied from the agent supply device 20. Alternatively, the present invention can also be applied to a case where a reducing agent is supplied from the reducing agent supply device 20 in order to regenerate an exhaust purification catalyst poisoned by a sulfur component or SOF (organic soluble component).

[0033]

As described above, the reducing agent can be supplied uniformly in the radial direction of the exhaust purification catalyst.

[Brief description of the drawings]

FIG. 1 is an overall view of an internal combustion engine.

FIG. 2 is a partially enlarged view showing a tip of a reducing agent injection nozzle.

FIG. 3 is a diagram for explaining the NO _X absorbing / releasing action of a NO _X absorbent.

FIG. 4 is a view showing a NO _X purification rate R of a NO _X absorbent.

FIG. 5 is a diagram showing a reducing agent supply amount qN.

FIG. 6 is a partially enlarged view similar to FIG. 2, showing a flow of a reducing agent.

FIG. 7 is a flowchart for calculating a reducing agent injection amount q.

FIG. 8 is a view showing another embodiment of the reducing agent injection nozzle.

FIG. 9 is a view showing still another embodiment of the reducing agent injection nozzle.

[Explanation of symbols]

1 ... engine body 15 ... exhaust pipe 16 ... oxidizing catalyst 17 ... NO _X absorbent 21 ... reducing agent injection nozzle 24 ... Hosoanatai

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (reference) F01N 3/24 F01N 3/28 301E 3/28 301 B01D 53/36 102A F-term (reference) 3G091 AA02 AA17 AA18 AB02 AB05 AB06 BA01 BA03 BA11 BA14 BA15 BA19 CA16 CA18 CA19 CB08 DB06 DB10 EA06 EA07 EA17 EA18 EA30 FA02 FA04 FA17 FA19 FB02 FB10 FC07 GB01W GB01X GB02W GB03W GB04W GB05W GB06W GB06X GB07W GB10X HA08 BA10 ABAX HA08 HA10 BA03 BA31X BA33X BA41X CC31 EA08 4G069 AA01 AA03 AA15 BA01B BC02B BC03B BC04B BC06B BC09B BC13B BC40B BC42B BC71B BC72B BC74B BC75B CA08 CA13 DA05 ED04

Claims (3)

[Claims] An exhaust purification catalyst is disposed in an engine exhaust passage, and a reducing agent injection nozzle is disposed in an engine exhaust passage upstream of the exhaust purification catalyst, and a reducing agent is supplied from the reducing agent injection nozzle to the exhaust purification catalyst. An exhaust purification device for an internal combustion engine, wherein a pore body is arranged between a reducing agent injection nozzle and an exhaust purification catalyst. 2. One side of the porous body is arranged adjacent to the injection port of the reducing agent injection nozzle, and the other side of the porous body is arranged adjacent to the exhaust upstream end face of the exhaust purification catalyst, and the reducing agent injection is performed during engine deceleration operation. 2. The exhaust gas purifying apparatus for an internal combustion engine according to claim 1, wherein the reducing agent is injected from a nozzle to temporarily store the reducing agent in the pores. 3. An exhaust purification catalyst is disposed in an engine exhaust passage, a reducing agent injection nozzle is disposed in an engine exhaust passage upstream of the exhaust purification catalyst, and a reducing agent is supplied from the reducing agent injection nozzle to the exhaust purification catalyst. An exhaust purification device for an internal combustion engine, wherein the reducing agent injection nozzle is arranged such that a reducing agent injection direction of the reducing agent injection nozzle is opposed to an exhaust flow direction.