JPH06307232A - Exhaust emission control device of internal combustion engine - Google Patents

Abstract

PURPOSE:To conduct efficiently the recovery operation of the SOX poisoning of an NOX absorbent. CONSTITUTION:An NOX absorbent 24 and a hydrogen gas supply device 31 to supply hydrogen gas to the NOX absorbent 24 are provided at the exhaust passage 22 of an internal combustion engine 1. When the NOX absorbing quantity of the NOX absorbent 24 has increased, NOX release from the NOX absorbent 24 and reducing purification are conducted by making the exhaust air-fuel ratio of the engine 1 rich, and when the SOX absorbing quantity of the NOX absorbent 24 has increased, the exhaust air-fuel ratio of the engine 1 is made rich and at the same time hydrogen gas is supplied to the NOX absorbent 24 from the hydrogen gas supply device 31 and the SOX poisoning of the NOX absorbent 24 is dissolved. As a result, the consumption quantity of hydrogen gas is reduced.

Description

Detailed Description of the Invention

[0001]

Relates to an exhaust purifying apparatus of the present invention is an internal combustion engine BACKGROUND OF THE relates to an exhaust purifying apparatus for an internal combustion engine equipped with _the NO _X absorbent to remove NO _X in the exhaust gas in particular.

[0002]

2. Description of the Related Art Japanese Unexamined Patent Publication No. 62-106826 discloses
NO when the air-fuel ratio of the exhaust gas is lean_XAbsorbs and drains
NO absorbed when the oxygen concentration in the gas decreases_XEmit
NO to_XAbsorbent placed in exhaust passage of diesel engine
And this NO_XNO in exhaust gas to absorbent_XExcretion to absorb
An air purification device is disclosed. In the device of the publication, the NO
_XBlocks exhaust gas inflow when the absorption efficiency of the absorbent decreases
Then NO_XSupplying hydrogen gas to the absorbent, NO_XAbsorbent
NO absorbed from_XReleased and NO released
_XWe carry out reduction purification of.

[0003] In the apparatus of JP-A Sho 62-106826, the release of the NO _X from _the NO _X absorbent by lowering the atmospheric oxygen concentration of the NO _X absorbent by supplying hydrogen gas to _the NO _X absorbent and to doing reduce and purify (following _the NO _X absorbent as "regeneration"), a large amount of hydrogen is consumed in order to consume the oxygen in the container with _the NO _X absorbent. Therefore, in the device of the above publication, it is necessary to supply a large amount of hydrogen gas for each regeneration operation of the NO _x absorbent, and the hydrogen gas consumption increases. Hydrogen gas can be supplied by a storage container, hydrogen gas generator, etc.
In order to supply a large amount of hydrogen gas, it is necessary to increase the scale of the container and generator, which causes problems in mounting on a vehicle and requires frequent replenishment of hydrogen and raw materials for hydrogen generation. There is a problem such as.

The applicant of the present invention has responded to the above problems by using NO _x.
When the absorbent is regenerated, the amount of fuel supplied to the engine is increased to shift the exhaust air-fuel ratio to rich and unburned HC, C in the exhaust gas
An exhaust gas purification device that regenerates the NO _x absorbent by increasing the O component has already been proposed (Japanese Patent Application No. 4-214313).
issue). _The NO _X absorbent absorbs NO _X in the exhaust gas of a lean air-fuel ratio as described above, the oxygen concentration in the exhaust performing absorbing and releasing action of the NO _X that releases NO _X absorbed and reduced.
This absorption and release action will be described in detail later, but if sulfur oxides (SO _X ) are present in the exhaust gas, the NO _X absorbent will be NO _X.
The same mechanism that absorbs the S
Absorbs O _X.

However, NO_XSO absorbed by absorbent
_XForms a stable sulfate, so NO_XAbsorbent
No decomposition or release at the temperature for regeneration NO_XAbsorbent
Tends to accumulate within. NO_XSO in absorbent
_XWhen the accumulated amount increases, NO _XAbsorbent NO_XAbsorption capacity
NO in exhaust gas_XCan be removed sufficiently
No longer stop_XOf so-called SO
_XThere is a problem of poisoning.

On the other hand, NO for absorbed SO _X in the _X absorbent NO _X absorbent hot and NO by the same mechanism as the absorption and desorption of NO _X by placing the rich air-fuel ratio atmosphere
It is known that it can be released from the _X- absorbent. Applicant, _the NO _X absorbent is SO _X poisoning which releases SO _X from _the NO _X absorbent by which to increase the fuel supply to the engine to the exhaust air-fuel ratio rich when they are hot state About the solution method Japanese Patent Application No. 4-198
Proposed in No. 224.

[0007]

It is generally known that hydrogen is more effective than HC and CO components in order to eliminate SO _X poisoning of NO _X absorbent. Hydrogen has a particularly strong affinity with sulfuric acid, and actively reacts with SO _X absorbed by the NO _X absorbent to generate gaseous H ₂ S, and NO _X.
Release from absorbent.

[0008] In the exhaust also by that increase the CO component of the combustion air-fuel ratio of the engine when the exhaust temperature is high in the rich exhaust gas of the engine as No. aforementioned Japanese Patent Application No. 4-198224, CO + H ₂ The reaction of O → CO ₂ + H ₂ occurs, and a certain amount of hydrogen can be generated.

However, as described above, hydrogen is generated and SO
_In order to utilize for the elimination of _X poisoning, the exhaust gas temperature is kept high enough to cause the above reaction, and the generated H ₂ reaches the NO _X absorbent before reacting with the oxygen in the exhaust gas, That is, it is necessary to operate the engine under high load and high rotation. Therefore, the operating conditions in which H ₂ due to the above reaction can be used for eliminating SO _X poisoning are extremely limited,
It is difficult to eliminate SO _X poisoning efficiently under conditions such as when the vehicle is running in urban areas.

On the other hand, can also be achieved to eliminate the SO _X poisoning during reproduction of the NO _X absorbent is a device that uses hydrogen gas regeneration of the NO _X absorbent as JP 62-106826 JP previously described However, in this case, there arises a problem that the amount of hydrogen gas consumed becomes large as described above. In view of the above problems, and an object thereof is to provide a means for eliminating the SO _X poisoning of easily and efficiently _the NO _X absorbent without the consumption of significant hydrogen gas.

[0011]

According to the present invention, N which absorbs NO _X when the air-fuel ratio of the inflowing exhaust gas is lean and releases the absorbed NO _X when the oxygen concentration of the inflowing exhaust gas decreases.
An O _X absorbent is disposed in the exhaust passage to absorb NO _X in the exhaust gas, and the exhaust air-fuel ratio flowing into the NO _X absorbent after NO _X absorption is made rich to absorb N _X from the NO _X absorbent.
In an exhaust emission control device for an internal combustion engine that releases O _x and reduces and purifies the released NO _x , a means for directly or indirectly detecting the amount of SO _x accumulated in the NO _x absorbent, and the detection and enriching means for SO _X storage amount which is to rich the air-fuel ratio of exhaust gas flowing into _the NO _X absorbent when the predetermined value or more, the NO _X when the exhaust air-fuel ratio is made rich by the rich means An exhaust gas purifying apparatus for an internal combustion engine, comprising: a means for supplying hydrogen gas to an absorbent.

[0012]

The oxygen concentration in the exhaust gas is drastically reduced by shifting the exhaust air-fuel ratio to rich when the SO _x poisoning of the NO _x absorbent is eliminated. In this state, hydrogen gas is supplied to the NO _x absorbent, so the supplied hydrogen gas is not used for consuming oxygen in the exhaust gas but the entire amount is used for eliminating SO _x poisoning of the NO _x absorbent. , Hydrogen gas consumption is reduced.

Further, hydrogen gas has a particularly strong affinity with sulfuric acid, and reacts with SO _X in the NO _X absorbent at a lower temperature than HC, CO, etc., and produces H ₂ S. Therefore, HC,
NO, for elimination of SO _X poisoning in the case of using a CO
_While it is necessary to keep the _X absorbent at a high temperature (500 to 600 ° C or higher), when hydrogen gas is used, SO _X poisoning is eliminated even at a relatively low temperature (300 to 400 ° C). It Therefore, NO _X absorbent temperature is obtained necessary readily SO _X poisoning recovery even at relatively low exhaust temperature city driving or the like.

[0014]

EXAMPLE FIG. 1 shows an example of the present invention. In FIG. 1, 1 is an internal combustion engine body, and 2 is an intake passage of the internal combustion engine. The intake port of each cylinder of the engine 1 is connected to the surge tank 5 via the branch pipe 4, and the branch pipe 4 of each cylinder is connected.
Is equipped with a fuel injection valve 7 for injecting fuel into each intake port. The surge tank 5 is connected to the intake passage 2, and the intake passage 2 is connected to an air cleaner 10 via an air flow meter 8. A throttle valve 11 is arranged in the air supply passage 2, and the throttle valve 11 is provided with an idle switch 12 which detects a fully closed state and outputs an idle signal.

Further, each exhaust port of the engine 1 is connected to an exhaust passage 22 via an exhaust manifold 21, and the exhaust passage 2
2 is provided with a NO _x absorbent 24 described later. Reference numeral 31 in the drawing denotes a hydrogen gas supply device for supplying hydrogen gas to the NO _X absorbent 24. In this embodiment, the hydrogen gas supply device 31 is a hydrogen gas generator 32 that generates hydrogen gas by electrolysis of water, and the container 3 that stores the generated hydrogen gas.
3 and hydrogen gas from the container 33 to the control valve 34.
Is supplied to the exhaust passage 22 on the upstream side of the NO _x absorbent 24.

Reference numeral 30 in the drawing denotes an electronic control unit (ECU) 30 for controlling the engine. The ECU 30
A CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), and a digital computer of a known type in which input / output ports are connected by a bidirectional bus. In addition to the basic control of the engine such as the above, the present embodiment also controls the SO _X poisoning elimination operation of the NO _X absorbent. For these controls, the output voltage proportional to the engine intake air amount from the air flow meter 8 is input to the input port of the ECU 30.
Further, an output voltage representing the vehicle traveling speed is input from the vehicle speed sensor 14 via an A / D converter (not shown), and an output pulse signal representing the engine speed is output from the rotation speed sensor 13 from the idle switch 12. Each signal is being input.

The output port of the ECU 30 has a fuel injection valve 7 and a hydrogen gas generator 3 through a drive circuit (not shown).
2. Control valves 34 are respectively connected to control the fuel injection amount to the engine, the operation of the hydrogen gas generator, and the opening / closing of control valve 34. Next, the NO _X absorbent 24 used in this embodiment will be described. As the NO _x absorbent 24, a carrier such as alumina is used, and potassium K,
At least one selected from sodium Na, lithium Li, alkali metals such as cesium Cs, alkaline earths such as barium Ba and calcium Ca, rare earths such as lanthanum La and yttrium Y, and a noble metal such as platinum Pt. Is carried. This _the NO _X absorbent is an air-fuel ratio of the exhaust flowing absorbs NO _X in the case of lean, the oxygen concentration is carried out to absorbing and releasing action of the NO _X that releases NO _X when lowered.

The exhaust air-fuel ratio mentioned above means here N
It means the ratio of the total amount of air and the total amount of fuel supplied to the exhaust passage on the upstream side of the O _X absorbent, the engine combustion chamber, the intake passage, and the like. Therefore, the fuel in the upstream side exhaust passage of the NO _X absorbent, hydrogen gas or the exhaust air-fuel ratio when the air is not supplied is equal to the operating air-fuel ratio of the engine (air-fuel ratio in the combustion in the engine combustion chamber).

In the present embodiment, the operating space during normal operation of the engine 1
The fuel ratio is fairly lean. Therefore NO_XSucking
NO because the air-fuel ratio of the exhaust passing through the sorbent is lean_X
Absorbent is NO in exhaust gas_XAbsorbs. Also, as described below
The operating air-fuel ratio of the engine 1 is switched to rich, and NO_XSucking
NO when the exhaust air-fuel ratio passing through the sorbent 24 becomes rich _X
Absorbent NO absorbed_XTo release.

The detailed mechanism of the above-mentioned absorption and release action is not clear in some parts. However, it is considered that this absorbing / releasing action is performed by the mechanism shown in FIG. Next, regarding this mechanism, platinum P on the carrier
The case of supporting t and barium Ba will be described as an example, but the same mechanism can be obtained by using other noble metals, alkali metals, alkaline earths and rare earths.

That is, the inflow exhaust becomes considerably lean.
And the oxygen concentration in the exhaust gas increased significantly, as shown in Fig. 3 (A).
As these oxygen O₂Is O₂ ^-Or O^2-In the form of
It adheres to the surface of platinum Pt. On the other hand, the NO in the exhaust gas is
This O on the surface of platinum Pt₂ ^-Or O^2-Reacts with N
O₂Becomes (2NO + O₂→ 2 NO₂ ). Then generated
NO₂Part of the inside of the absorbent while being oxidized on platinum Pt
While being absorbed by and bound to barium oxide BaO,
As shown in (A), nitrate ion NO₃ ^-Absorbent in the form of
Diffuse in. NO in this way_XIs NO_XIn absorbent
Is absorbed by.

Therefore, as long as the oxygen concentration in the inflowing exhaust gas is high, NO ₂ is produced on the surface of platinum Pt, and N ₂ of the NO _x absorbent is generated.
O _X absorption is increased NO _X absorbing capacity of the absorbent as long as NO ₂ not to saturate is absorbed in the absorber nitrate ion NO
₃ ^- is generated. In contrast the oxygen concentration decreases and the amount of NO ₂ is reduced by reaction backward in the inflowing exhaust gas (NO ₃ ^- → NO ₂₎ proceeds to thus of the absorbent and nitrate ions NO ₃ ^- is NO ₂ Is released from the absorbent in the form of.
That is, the oxygen concentration in the inflowing exhaust gas is NO _X is released from _the NO _X absorbent when lowered.

On the other hand, when reducing components such as fuel HC and CO are present in the inflowing exhaust gas, these components react with oxygen O ₂ ⁻ or O ^{2 −} on the platinum Pt to be oxidized, and the oxygen in the exhaust gas is removed. It is consumed to reduce the oxygen concentration in the exhaust gas. In addition, NO released from the NO _X absorbent due to a decrease in oxygen concentration in the exhaust gas
₂ is reduced by reacting with HC and CO as shown in FIG. 3 (B). When NO ₂ is no longer present on the surface of platinum Pt in this manner, NO ₂ is released from the absorbent one after another.

That is, HC and CO in the inflowing exhaust gas are
O on the platinum Pt₂ ^-Or O^2-Reacts immediately with the acid
And then O on the platinum Pt₂ ^-Or O^2-Consumed
If HC and CO still remain after this,
Therefore NO released from the absorbent_XIs reduced. Real
In the embodiment, the ECU 30 is a separately executed routine (not shown).
Predetermined NO by chin_XWhen the absorbent regeneration conditions are met
To increase the amount of fuel supplied from the fuel injection valve 7 to the engine 1.
The combustion air-fuel ratio of the engine 1 is shifted to the rich side. to this
Than NO _XThe air-fuel ratio of the exhaust gas passing through the absorbent 24 is
And the oxygen concentration decreases and unburned H in the exhaust gas
Since the components such as C and CO increase, the above NO_XAbsorbent
NO from_XIs released and reduction purification (regeneration) is performed.

In the present embodiment, the NO _x absorbent regeneration conditions are as follows: (1) The engine exhaust temperature is equal to or higher than a predetermined value (that is, the NO _x absorbent has an activation temperature (for example, about 250 ° C.)).
It), has been reached (2) a predetermined time from the previous playback operation (for example, about several minutes) that it has passed (i.e. NO _X absorption amount of the NO _X absorbent is increasing),
(3) The throttle valve 11 is in a fully closed state (engine braking or idle operation). The purpose of performing the regeneration operation of the NO _X absorbent only during engine braking is mainly to prevent deterioration of vehicle drivability due to engine torque fluctuations during operation caused by changes in the air-fuel ratio.

Next, NO_XAbsorbent SO_XPoisoned mechanics
I will explain about. SO during exhaust_XContains ingredients
Then NO_XAbsorbent is NO above_XSame mechanism as absorption of
SO in the exhaust_XAbsorbs. That is, exhaust air-fuel
SO in the exhaust when the ratio is lean_X(Eg SO₂) Is
SO oxidized by platinum Pt₃ ^-, SO_Four ^-And then acid
BaSO combined with BaO_FourTo form. B
aSO _FourIs relatively stable, and the crystals become coarse.
Once produced, it is difficult to decompose and release due to rinsing. others
No_XBaSO in the absorbent_FourWhen the production of
NO_XThe amount of BaO that can be involved in the absorption of NO decreases_X
Absorbs less. This SO_XPrevent poisoning
NO in order to_XBaSO formed in the absorbent_FourTo
SO which is decomposed at high temperature and is generated by this₃
^-, SO_Four ^-Reduce the sulfate ion of NO, NO_XFrom absorbent
Need to be released. In the present invention, using hydrogen gas
Reduces sulfate ions to give gaseous H₂To switch to S
More NO_XAbsorbent SO_XThe poisoning has been eliminated.

Next, the SO of the embodiment of FIG._XFor poisoning elimination operation
explain about. In this embodiment, the history of engine operating conditions
To NO_XThe temperature of the absorbent 24 is detected and NO_XAbsorbent 2
When the temperature of 4 is above the specified value, supply hydrogen gas.
Salary SO _XEliminate poisoning. As mentioned above, SO_XPoisoning
In order to eliminate the problem, N up to the temperature at which stable sulfate can be decomposed
O_XAlthough it is necessary to raise the temperature of the absorbent, this example
By using hydrogen gas, which has a strong affinity with sulfuric acid,
Lower temperature than when using HC, CO, etc. (300
SO at ~ 400 degrees C)_XIt is possible to eliminate poisoning
ing. For this reason, a significantly high load and high rotation operating condition is required.
It is not required, and it is sufficiently NO when driving in urban areas._XAbsorbent
Is SO_XThe temperature rises to a temperature at which the poisoning elimination operation can be performed.
And SO_XExecution of poisoning elimination operation is NO_XDepending on the absorbent temperature
Sufficient SO_XTo eliminate poisoning
be able to.

Further, in this embodiment, when the hydrogen gas is supplied, the engine air-fuel ratio is shifted to the rich side before the supply. As a result, the oxygen concentration in the exhaust gas that flows into the NO _x absorbent during hydrogen gas supply is greatly reduced, and the amount of hydrogen gas required to consume oxygen in the exhaust gas is reduced, resulting in a small amount of hydrogen gas. Thus, SO _X poisoning can be completely eliminated.

Further, in this embodiment, the hydrogen gas is supplied only when the engine is idle (when the throttle valve is fully closed). By supplying hydrogen gas when the flow rate of exhaust gas decreases in this way, the hydrogen concentration necessary for maintaining the hydrogen concentration in the exhaust gas at the level required for SO _X poisoning elimination (for example, about 1%). The gas supply amount can be further reduced, and the hydrogen gas consumption amount during the SO _X poisoning elimination operation is significantly reduced.

Further, in the present embodiment, a hydrogen generator of the type that generates hydrogen by electrolysis of water is provided, and the generated hydrogen is stored in a container and NO _{X is} removed during SO _X poisoning elimination operation.
Hydrogen gas is supplied to the absorbent, but as a result of reducing the consumption of hydrogen gas as described above, it is possible to reduce the capacity of the hydrogen gas generator and the storage container, and it is easy to mount on a vehicle. In addition to being good, it is possible to reduce the supply frequency of the raw material (water).

FIG. 2 is a control flowchart of the SO _X poisoning elimination operation of this embodiment. This routine is the above E
It is executed by the CU 30 at regular intervals. When the routine starts in FIG. 2, in step 201, the engine speed N, the engine intake air amount Q, and the vehicle speed S are read.
Note that these values are separately read from the respective sensors by a routine that is executed by the ECU 30 at regular intervals, and the latest values are always stored in the RAM of the ECU 30.

Next, at step 203, the integrated value of the engine load state for the past 5 minutes is calculated. That is, in step 203, the intake air amount Q / N per engine revolution is calculated, and the Q / N is calculated from the numerical table stored in the ROM.
The engine load torque corresponding to is read out, the load torque is multiplied by the engine speed N to calculate the engine load, and the integrated value L of the calculated engine load for the past 5 minutes is calculated. Integrated value L is the quantity of heat engine is occurred in the past 5 minutes, i.e. the integrated value is proportional to the amount of heat that _the NO _X absorbent 24 is received L is as possible out to be used as a parameter representing the temperature of the NO _X absorbent 24.

In step 205, the vehicle speed S is used to calculate an integrated value D of the distance traveled by the vehicle since the SO _X poisoning elimination operation was performed last time. Here, Δt is an execution interval (time) of this routine. The cumulative value D of the traveled distance is the SO accumulated in the NO _X absorbent after the previous poisoning elimination operation is executed.
Used as a parameter that represents the amount of _X. Step two
Reference numerals 07 to 211 indicate the determination of the execution start condition of the SO _X poisoning elimination operation. That is, at step 207, it is determined whether or not the integrated load value L is equal to or greater than a predetermined value L ₀ (whether the NO _X absorbent 24 is at or above a predetermined temperature), and at step 209, is the integrated travel distance value D equal to or greater than a predetermined value D _0. Whether (the SO _X absorption amount of the NO _X absorbent 24 is equal to or more than a predetermined value), it is determined in step 211 whether the idle signal from the idle switch 12 is ON (whether the engine is in idle operation), Only when all of these conditions are satisfied, the SO _X poisoning elimination operation in step 215 and thereafter is executed.

That is, in step 215, the engine air-fuel ratio
The control flag FR is set (= "1"). Flag F
When R is set, the fuel that is separately executed by the ECU 30
Make the engine air-fuel ratio rich in the fuel injection control routine
Fuel injection amount is set, NO _XExhaust flowing into the absorbent 24
The air-fuel ratio shifts to the rich side. In addition, step 217
Then, the control valve 34 of the hydrogen supply device 31 is opened, and NO_X
Absorbent 24 Hydrogen gas is supplied to the upstream exhaust passage 22
It

It should be noted that the traveling distance integrated value D corresponds to a value at which the SO _X poisoning elimination operation is performed every several hours in ordinary city driving. Steps 219 and 221 show the determination of the termination condition of the SO _X poisoning elimination operation. That is, in step 219, the counter T indicating the elapsed time from the start of hydrogen gas supply is incremented by 1, and in step 221, it is determined whether or not the elapsed time T has reached the predetermined value T ₀ . In this embodiment, the predetermined value T ₀ is set to a value corresponding to the elapsed time of 1 minute in order to determine that the SO _X poisoning has disappeared when about 1 minute has elapsed after the supply of hydrogen gas was started. .

When it is determined in step 221 that SO _X poisoning has been eliminated, in step 223, the L, D, and T parameters are cleared and the flag FR is reset (= "0").
Is performed, the control valve 34 is closed in step 227, and S
The O _X poisoning elimination operation ends. If the predetermined time has not elapsed in step 221, the routine is finished and the supply of hydrogen gas is continued.

In the above embodiment, the temperature of the NO _X absorbent 24 is detected by using the history of engine operating conditions. For example, an exhaust temperature sensor for detecting the exhaust temperature in the exhaust passage downstream of the NO _X absorbent. May be provided, and the temperature of the NO _X absorbent 24 may be detected by calculating the integrated value of the exhaust temperature.
Further, in the present embodiment is carried out to eliminate the SO _X poisoning by supplying hydrogen gas to the same time _the NO _X absorbent shifts the exhaust air-fuel ratio rich, constant transitions the exhaust air-fuel ratio to a rich The supply of hydrogen gas may be started after a lapse of time. Unburned HC in the exhaust gas in this case, release of the NO _X from _the NO _X absorbent with CO component, the hydrogen gas after the reduction and purification is performed will be supplied, the hydrogen gas is usually NO _X Is not consumed for the release and reduction of SO _X
Since it is used only for eliminating poisoning, the consumption of hydrogen gas can be further reduced.

[0038]

According to the present invention, when the SO _X poisoning of the NO _X absorbent is eliminated, the exhaust air-fuel ratio is made rich and hydrogen gas is supplied to the NO _X absorbent.
_Since the consumption of hydrogen gas at the time of eliminating SO _X poisoning of the _X absorbent can be greatly reduced, it is possible to efficiently use the S gas of the NO _X absorbent by using the hydrogen gas which has conventionally been problematic in replenishment and storage.
O _X poisoning recovery can be achieved. Moreover, since it becomes possible to use the SO _X poisoning recovery hydrogen gas, free of SO _X poisoning removing operation performed it is possible to perform the SO _X poisoning recovery operation at relatively low _the NO _X absorbent temperature degree is increased, the effect can always maintain a high NO _X absorbing capacity of the NO _X absorbent can be obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of an exhaust purification system for an internal combustion engine of the present invention.

FIG. 2 is a control flowchart of a SO _X poisoning elimination operation of the embodiment of FIG.

FIG. 3 is a diagram for explaining the NO _X absorption / release action of the NO _X absorbent of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine main body 2 ... Intake passage 4 ... Branch pipe 5 ... Surge tank 7 ... Fuel injection valve 8 ... Air flow meter 10 ... Air cleaner 11 ... Throttle valve 12 ... Idle switch 13 ... Rotation speed sensor 14 ... Vehicle speed sensor 21 ... Exhaust manifold 22 ... Exhaust passage 24 ... NO _X absorbent 30 ... Electronic control unit (ECU) 31 ... Hydrogen gas supply device 32 ... Hydrogen gas generator 33 ... Hydrogen storage container 34 ... Control valve

Claims (1)

[Claims] 1. NO when the air-fuel ratio of the inflowing exhaust gas is lean
The _the NO _X absorbent to release the absorbed NO _X when the oxygen concentration of the inflowing exhaust absorbs _X was reduced by arranging in the exhaust passage to absorb the NO _X in the exhaust gas, the NO _X after NO _X absorbent
When the exhaust air-fuel ratio flowing into the absorbent is made rich, the NO _x
In an exhaust emission control device for an internal combustion engine that releases NO _X absorbed from an absorbent and reduces and purifies the released NO _X , the amount of SO _X accumulated in the NO _X absorbent is directly or indirectly detected. Means and the detected SO _X
Wherein when the amount of accumulation and the enrichment means to rich the air-fuel ratio of the exhaust gas flowing into the NO _X absorbent when the predetermined value or more, the exhaust air-fuel ratio by the rich means being rich NO _X
An exhaust gas purification apparatus for an internal combustion engine, comprising: a means for supplying hydrogen gas to the absorbent.