JP2891057B2 - Exhaust gas purification device for internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to an exhaust purifying apparatus for an internal combustion engine, in particular, a gasoline engine or the like for a diesel engine or lean burn, the NO _X in the exhaust gas of an internal combustion engine causing combustion of lean air-fuel ratio The present invention relates to an exhaust purification device that can be removed effectively.

[0002]

2. Description of the Related Art An example of this type of exhaust gas purifying apparatus is disclosed, for example, in Japanese Patent Application Laid-Open No. 62-106826. The apparatus of this publication, in an exhaust passage of a diesel engine, absorbent absorbs NO _X in the presence of oxygen by placing a (catalyst) to absorb the NO _X in the exhaust gas, NO _X in the absorbent
Absorption capacity and cut off the flow of exhaust gas into the absorber when saturated supplying reducing agent to the absorbent to release NO _X from the absorbent by the _the NO _X absorbent in an atmosphere under a rich air-fuel ratio In addition, the NO _X released together with the above is reduced and purified.

[0003]

Problems to be Solved by the Invention
In the exhaust gas purifying apparatus disclosed in Japanese Patent No. 6826, NO_XTo the absorbent
NO by shutting off the inflow of exhaust_XSupply reducing agent to absorbent
NO_XThe absorbent is being regenerated.
In this specification, the above NO_XNO from absorbent _Xrelease
And the operation of reduction purification_XAbsorbent regeneration operation ''
Bu). However, in the device of the above publication, after the end of the reproduction operation,
Next NO_XNO during standby period until absorption operation restart_XAbsorbent
Keeps the exhaust
Is not supplied during the standby period._XAbsorbent
Temperature may decrease. Especially in the exhaust passage
Multiple NO_XConnect the absorbents in parallel and turn the exhaust
Shut off and NO_XIn the case of regenerating absorbent
Means each NO_XAbsorbent NO_XMake the most of your absorption capacity
NO to_XThe time to absorb the water is the time required for regeneration
Set much longer. For this reason, after the end of the playback operation,
Waiting period becomes longer, NO_XLarge temperature drop of absorbent
Become.

[0004] Since NO _X absorbing capacity of the NO _X absorbent is lowered significantly in the low temperature range, the temperature of the NO _X absorbent is lowered during the waiting period, as described above, when restarting the absorption of the NO _{X the} NO _X absorbent can not exhibit a predetermined absorbent capacity, a problem that the purification efficiency of the NO _X in the exhaust gas decreases occur. To solve this problem, NO waiting period to start playback immediately after termination NO _X absorbing operation of the NO _X absorbent
_Although it is possible to prevent the temperature of the _X absorbent from lowering, in the case where a plurality of NO _X absorbents are connected in parallel to the exhaust passage for switching as described above, the switching cycle between the absorption and the regeneration is used. These shortened there is a problem that effectively no longer take advantage of the NO _X absorption capability of each _the NO _X absorbent. Also, there are cases where the effect on the engine output caused by exhaust flowing blocked accompanying the exhaust resistance variation to _the NO _X absorbent, it is not preferable to shorten the switching cycle.

[0005] The present invention has been made in view of the above, to prevent the temperature decrease of the NO _X absorbent during the waiting period after regeneration operation end, it is maintained at a high level the absorption capacity of the NO _X absorbing operation resumption of the NO _X absorbent It is an object of the present invention to provide a possible exhaust gas purification device for an internal combustion engine.

[0006]

According to the present invention, in order to solve the problems], in an exhaust passage of an internal combustion engine capable of performing combustion of the lean air-fuel ratio, NO _X in the exhaust gas when the air-fuel ratio of the inflowing exhaust is lean
Absorb oxygen concentration reducing agent is supplied to the inflowing exhaust is arranged _the NO _X absorbent to release the absorbed NO _X when dropped, flows into _the NO _X absorbent after imbibed with NO _X exhaust An exhaust gas of an internal combustion engine that repeats a regeneration operation of reducing the flow rate and supplying the reducing agent to the NO _X absorbent to release the absorbed NO _X and an operation of restoring the exhaust flow rate and restarting the NO _X absorption after the regeneration is completed in purifying apparatus for controlling the air-fuel ratio of the exhaust gas passing through the _the NO _X absorbent and supplying the reducing agent in a predetermined time period _the NO _X absorbent before resuming the NO _X absorbed by recovering exhaust flow rate to near stoichiometric air-fuel ratio There is provided an exhaust gas purification device for an internal combustion engine, characterized by comprising means.

[0007]

[Action] Prior NO _X absorbent resumed, the air-fuel mixture and the exhaust of the air-fuel ratio of the near stoichiometric air-fuel ratio and the reducing agent is supplied to _the NO _X absorbent,
The heat of oxidation of the reducing agent is generated on the NO _x absorbent. Accordingly, the temperature of the NO _X absorbent during the waiting period is kept high, the absorption capacity reduction of the NO _X absorbent resumption of the NO _X absorbent does not occur.

[0008]

Embodiments of the present invention will be described below with reference to the accompanying drawings. In FIG. 1, reference numeral 1 denotes an internal combustion engine capable of performing combustion at a lean air-fuel ratio, such as a diesel engine or a gasoline engine performing lean combustion, and 3 denotes an exhaust passage of the internal combustion engine 1. In this embodiment, the exhaust passage 3 has two branch passages 3.
a, 3b are provided, NO _X in the exhaust gas when the passage 3a, the exhaust air-fuel ratio flowing into each of the 3b lean
Absorb, NO _X absorbent oxygen concentration in the exhaust gas to release NO _X absorbed when lowered, respectively 5a, 5b are connected.

An exhaust switching valve 2 is provided at a branch of the exhaust passage 3 from the passages 3a and 3b.
b is closed to a predetermined opening to exhaust passage 3a,
The exhaust gas is distributed to 3b. For example, when the exhaust switching valve 2 is switched to the position shown by the solid line in FIG. 1, most of the exhaust flows into the branch passage 3b, and the flow rate of the exhaust flowing into the branch passage 3a is reduced. When the exhaust switching valve 2 is switched to the position shown by the dotted line in FIG. 1, most of the exhaust flows into the branch passage 3a, and the flow rate of the exhaust flowing into the branch passage 3b is reduced. An actuator of an appropriate type, such as a negative pressure actuator for driving the switching valve 2 to a predetermined switching position by driving a switching valve 2 by a control signal from an engine control circuit (ECU) 20 to be described later, is shown in FIG. .

[0010] The branch passage 3a in the present embodiment, 3b is _the NO _X absorbent 5a, are joined again at 5b downstream, the exhaust switching valve 2 is in the merging portion similar exhaust switching valve 22
And an actuator 22a. Exhaust switching valve 22 operates in conjunction with the exhaust switching valve 2 controls the flow rate of the exhaust gas flowing into the respective branch passages, the downstream side in _the NO _X absorbent during regeneration when _the NO _X absorbent regeneration operation described later Exhaust is prevented from flowing backwards.

Furthermore, branch passages 3a, NO _X absorbent 5a of 3b, NO _X absorbent 5a from the reducing agent supply device 11 to be described later to 5b upstream, the reducing agent supply nozzle for supplying a reducing agent to 5b, respectively 12a , 12b are connected. In FIG. 1, reference numerals 7a and 7b denote branch passages 3 respectively.
a, NO _X absorbent 5a of 3b, a air-fuel ratio sensor disposed in 5b the downstream side. As the air-fuel ratio sensors 7a and 7b, so-called all-range air-fuel ratio sensors that detect the oxygen concentration in the exhaust gas and generate an output voltage corresponding to the exhaust air-fuel ratio in a wide range are used.

A control circuit (ECU) of the engine 1 is shown at 20 in FIG. The ECU 20 includes a CPU, a RAM, and an RO.
M, and a well-known digital computer having a configuration in which an input port and an output port are mutually connected by a bidirectional bus, and performs basic control such as fuel injection amount control of an engine. Further, in the present embodiment, the ECU 20 further includes a drive circuit (not shown), a negative pressure control valve, and the like.
a and 22a are driven to control the switching position of the exhaust switching valves 2 and 22, and the reducing agent supply control from the reducing agent supply device 11 is performed. ECU2 for these controls
The input port of 0 receives air-fuel ratio signals from the air-fuel ratio sensors 7a and 7b, and also inputs signals such as engine speed and engine intake air amount from sensors not shown.

The reducing agent supply device 11 includes a reducing agent supply source 13 composed of a reducing agent container, a pressure pump and the like, and a reducing agent supply amount supplied from the reducing agent supply source 13 to the reducing agent supply nozzles 12a and 12b. Control valves 14a and 14b for adjusting the flow rate
And check valves 15a, 15 disposed between the nozzles 12a, 12b and the control valves 14a, 14b for preventing exhaust backflow.
b. Control valves 14a, 14b is described below _the NO _X absorbent 5a, when 5b playback operation and, during the subsequent waiting period, take the predetermined opening in response to a control signal of ECU 20, in an amount corresponding to the opening the reducing agent _the NO _X absorbent 5a,
5b.

[0014] _the NO _X absorbent 5a, 5b of the NO _X emission, the reducing agent used for reduction operations (playback operations), as long as it generates a hydrocarbon, reducing components such as carbon monoxide in the exhaust gas , Hydrogen, carbon monoxide and the like, liquid and gaseous hydrocarbons such as propane, propylene and butane, and liquid fuels such as gasoline, light oil and kerosene. _The NO _X absorbent 5a, 5b uses a carrier such as alumina or the like, an alkali metal, barium Ba, alkaline earth such as calcium Ca, such as the carrier on, for example, potassium K, sodium Na, lithium Li, cesium Cs , Lanthanum La, and rare earth elements such as yttrium Y, and a noble metal such as platinum Pt. This _the NO _X absorbent 5a, 5b absorbs NO _X in the case the air-fuel ratio of the exhaust gas flowing is lean, the oxygen concentration is carried out to absorbing and releasing action of the NO _X that releases NO _X when lowered.

The above-mentioned exhaust air-fuel ratio is defined as N
O _X absorbent 5a, upstream of the exhaust passage and the engine combustion chamber 5b, it shall mean the ratio of the sum of the total fuel and reducing agent, respectively to the intake passage or the like supplied air quantity. Therefore, NO _X absorbent 5a, the fuel in the upstream side exhaust passage 5b,
When no reducing agent or air is supplied, the exhaust air-fuel ratio becomes equal to the operating air-fuel ratio of the engine (air-fuel ratio in combustion in the engine combustion chamber).

In this embodiment, since an engine that performs combustion at a lean air-fuel ratio is used, the exhaust air-fuel ratio during normal operation is lean, and the NO _X absorbents 5a and 5b
Absorb _X. Further, when the has been oxygen concentration introduced the reducing agent into the exhaust gas decreases, NO _X absorbent 5a, 5b is a release of absorbed reducing agent performs a reducing agent supply device 11. The detailed mechanism of this absorption / release action is not clear in some parts. However, it is considered that this absorption / release action is performed by a mechanism as shown in FIG. Next, regarding this mechanism, platinum Pt and barium B
Although the case where a is carried will be described as an example, the same mechanism is obtained by using other noble metals, alkali metals, alkaline earths, and rare earths.

That is, the inflow exhaust gas becomes considerably lean.
And the oxygen concentration in the inflowing exhaust gas greatly increased, as shown in Fig. 2 (A).
These oxygen O_TwoIs O_Two ^-Or O^2-In the form of
It adheres to the surface of platinum Pt. On the other hand, NO in the inflow exhaust gas is
This O on the surface of platinum Pt_Two ^-Or O^2-Reacts with N
O_Two(2NO + O_Two→ 2NO_Two ). Then generated
NO_TwoSome of the oxygen is oxidized on platinum Pt and
FIG. 2 shows that while being absorbed by and combined with barium oxide BaO.
As shown in (A), nitrate ion NO_Three ^-Absorbent in the form of
Spreads in. NO in this way_XIs NO_XAbsorbent 5
a and 5b.

Therefore, as long as the oxygen concentration in the inflowing exhaust gas is high, NO ₂ is generated on the surface of the platinum Pt, and as long as the NO _x absorption capacity of the absorbent is not saturated, NO ₂ is absorbed in the absorbent and nitrate ions NO ₃ ^- is generated. On the other hand, when the oxygen concentration in the inflowing exhaust gas decreases and the amount of generated NO ₂ decreases, the reaction proceeds in the reverse direction (NO ₃ ⁻ → NO ₂ ), and thus the nitrate ion NO ₃ ⁻ in the absorbent becomes NO ₂ Released from the absorbent in the form of That is, the oxygen concentration when decreases _the NO _X absorbent 5a of the inflowing exhaust, NO _X is to be released from 5b.

On the other hand, if reducing components such as HC and CO are present in the inflowing exhaust gas, these components become oxygen O ₂ on platinum Pt.
^- or it is reacted with oxide and O ^2-, lowering the oxygen concentration in the exhaust to consume oxygen in the exhaust. Further, NO ₂ released from the NO _x absorbents 5a and 5b due to a decrease in the oxygen concentration in the exhaust gas is reduced by reacting with HC and CO as shown in FIG. 2 (B). In this manner, NO _{2 is} deposited on the surface of platinum Pt.
When NO is no longer present, NO ₂ is released from the absorbent one after another.

That is, HC and CO in the inflow exhaust gas are
O on platinum Pt_Two ^-Or O^2-Reacts immediately with acid
And then O on platinum Pt_Two ^-Or O^2-Is consumed
If HC and CO still remain,
Therefore, NO released from the absorbent_X, And with the exhaust
NO flowing into_XIs reduced. In this embodiment, the exhaust
NO by operating the changeover valves 2 and 22_XOf the absorbents 5a and 5b
NO_XAlternate absorption and release. That is, this embodiment
By operating the exhaust switching valves 2 and 22, one NO_X
Most of the exhaust gas flows through the absorbent (for example, 5a) and NO_XTo
Absorb. NO_XNO of absorbent 5a_XAbsorption
When it increases, the exhaust switching valves 2 and 22 are switched and other
NO_XExhaust gas is passed through the absorbent 5b, and NO _XAbsorbent 5a
While reducing the flow rate of exhaust gas flowing into the
NO from chisel 12a_XSupplying the reducing agent to the absorbent 5a
O_XThe absorbent 5a is regenerated. NO after switching_XSucking
NO of absorbent 5b_XWhen the amount of absorption increases, turn off the exhaust again.
The switching of the switching valves 2 and 22 is performed and NO_XOn the absorbent 5a side
NO exhaust gas_XNO by absorbent 5a_XResume absorption
NO_XThe regeneration of the absorbent 5b is performed.

[0021] above, the time _the NO _X absorbent is capable of performing the NO _X absorbent, for example a relatively long of about 10 minutes, the time required for regeneration of the NO _X absorbent, for example, several tens of Relatively short, on the order of seconds. Therefore, NO _X absorbent reproducing operation is ended, the next is switched exhaust switching valve N
Until the _OX absorption is resumed, the exhaust gas flow rate is kept reduced while the apparatus is in a standby state. Therefore, the problem that the temperature of the NO _X absorbent is lowered occurs during the waiting period.

In the embodiment according to the present invention, the standby NO _X
Supplying a reducing agent to the absorber, by maintaining the air-fuel ratio of the exhaust gas passing through _the NO _X absorbent to near the stoichiometric air-fuel ratio, NO
Solves the problem of temperature drop of _X absorbent. That is,
As described with reference to FIG. 2, the NO _X absorbent has a function as an oxidation catalyst that promotes the oxidation of reducing components such as HC and CO in the presence of oxygen. Therefore, by supplying oxygen and a reducing agent to the NO _X absorbent in standby, causing an oxidation reaction of the NO _X absorbent on the reducing agent, NO _X by reaction heat
It is possible to prevent the temperature of the absorbent from lowering. In the embodiment according to the present invention, the NO _X which is in the standby state for the mixture of the exhaust gas and the reducing agent maintained near the stoichiometric air-fuel ratio optimum for the oxidation reaction.
By supplying the absorbent, thereby preventing a decrease in the absorption capacity at the time of NO _X absorbed resumed maintaining a high temperature of the NO _X absorbent.

Next, the exhaust gas purifying operation of this embodiment will be described.
I will tell. In the following description, NO in FIG._XN of absorbent 5a
O_XThe absorption and regeneration operations will be described._Xabsorption
Absorption and regeneration operations are performed in the same manner for agent 5b.
You. The exhaust switching valves 2 and 22 are held at the positions indicated by the dotted lines in FIG.
NO_XMost of the engine exhaust flows into the absorbent 5a
And NO_XAs described above, the absorbent 5a contains NO in the exhaust gas. _Xof
Perform absorption. Then, after a predetermined time has passed, NO_XAbsorbent
NO of 5a_XWhen the amount of absorption increases, the ECU 20 turns off the exhaust.
The changeover valves 2 and 22 are switched to the positions indicated by the solid lines in FIG._X
The regeneration operation of the absorbent 5a is started.

In this embodiment, NO_XRegeneration of absorbent
This is performed at regular intervals, but the engine NO_XDepending on the amount
NO_XAbsorbent NO_XNO each time the amount of absorption reaches a predetermined value
_XRegeneration of the absorbent may be performed. In this case, E
The CU 20 determines the NO per unit time of the institution._XGenerated amount
Related load (for example, intake air amount per engine revolution) and machine
Is stored in advance in ROM as a function of
Read the engine load condition at regular time intervals and read the above
NO_XRead out the amount of generation and multiply this amount by a certain coefficient.
NO_XAbsorbent NO_XAbsorbed amount
You. This NO_XNO when the absorption amount reaches a predetermined value_XSucking
If the sorbent is regenerated, the engine NO _XChange in the amount generated
NO regardless of_XAbsorbent NO_XEnable absorption capacity
It can be used for

[0025] exhaust switching valve 2, 22 is switched to the position indicated by the solid line in FIG. 1, the flow rate of the exhaust gas flowing to _the NO _X absorbent 5a is reduced, most of the exhaust flows through the _the NO _X absorbent 5b because, NO in the exhaust gas by _the NO _X absorbent 5b
_X absorption is performed. Regenerating operation of the NO _X absorbent 5a is performed in the following procedure. First, ECU 20 are read exhaust air-fuel ratio of the engine from an output of the air-fuel ratio sensor 7b disposed on the downstream side of the NO _X absorbent 5b that initiated the absorption of the NO _X, and the exhaust air-fuel ratio, NO _X to be reproduced determining a reducing agent flow rate to be supplied to _the NO _X absorbent 5a and a flow rate of the exhaust gas flowing into the absorbent 5a side. In this embodiment, the reducing agent flow rate supplied to the NO _X absorbent during the regenerating operation is an amount that maintains only the rich side by a predetermined amount than the stoichiometric air-fuel ratio of the air-fuel ratio of the exhaust gas flowing into the NO _X absorbent. Further, the flow rate of the exhaust gas flowing to _the NO _X absorbent passes through the exhaust switching valve during playback operation, the engine load, as a function of operating conditions such as rotational speed, to previously obtain in advance by actual measurement and stored in the ROM .

The ECU20 is a control valve 14 of the reducing agent supply device 11, performs the supply of the reducing agent to the NO _X absorbent 5a is set to the corresponding opening to the calculated reducing agent flow through the, NO _X Air-fuel ratio sensor 7a downstream of absorbent 5a
The supply time of the reducing agent is controlled based on the output of. As described above, when the supply of the reducing agent to the NO _X absorbent is started,
First, the reducing agent consumes O ₂ in the exhaust gas or the Pt surface of the NO _X absorbent, and after consuming this O ₂ , reduction and purification of NO _X is started. Therefore, at the initial stage after the start of the supply of the reducing agent, N
The oxygen concentration in exhaust gas flowing out of O _X absorbent is relatively high, the O ₂ is consumed, the oxygen concentration in the exhaust gas and the reducing starts of the NO _X decreases rapidly. ECU 20
Maintains the supply amount of the reducing agent so that the exhaust air-fuel ratio becomes rich for a predetermined period after detecting the decrease in the oxygen concentration from the output change of the air-fuel ratio sensor 7a. This makes NO
It is prevented _{that X} absorbent excess reducing agent after playing flows out from _the NO _X absorbent. During this period, NO _X
It is set in advance according to the amount of NO _X absorbed by the absorbent (absorption time).

[0027] After the reproduction operation terminated, NO _X absorbent 5a is placed in a standby state includes the NO _X absorbent starts the next while reducing the flow rate of the exhaust. ECU20 in the present embodiment, after the reproduction time has elapsed, so that the exhaust gas air-fuel ratio of _the NO _X absorbent 5a downstream waiting is in the vicinity of the stoichiometric air-fuel ratio, the control valve based on output of the air-fuel ratio sensor 7a The opening of 14a is feedback-controlled. Thus, since by feedback-controlling the reducing agent supply amount based on the air-fuel ratio sensor output of the downstream exhaust air-fuel ratio passes through _the NO _X absorbent waiting is held accurately in the vicinity stoichiometric air-fuel ratio , NO
A favorable oxidation reaction of the reducing agent supplied to the _X absorbent is obtained, and the temperature of the standby NO _X absorbent can be kept high. This also it is possible to oxidize the total amount of the reducing agent supplied to _the NO _X absorbent is prevented from excess reducing agent flows out into _the NO _X absorbent downstream.

[0028] Figure 3, according to the operation shows the change cycle of the air-fuel ratio of the exhaust gas flowing into the NO _X absorbent. FIG.
In, at the time of NO _X absorbing operation of the NO _X absorbent NO _X
The exhaust air-fuel ratio flowing into the absorbent is maintained at a lean air-fuel ratio (Fig. 3, section I). Then the switching of the exhaust switching valve is performed, the reducing agent is supplied to _the NO _X absorbent, the predetermined period exhaust air-fuel ratio after the switching is held in the rich air-fuel ratio, NO
Regeneration of the _X absorbent is performed (FIG. 3, section II). Also, N
During O waiting period after the reproduction is completed in the _X absorbent, the exhaust air-fuel ratio is maintained near the stoichiometric air-fuel ratio, the temperature of the NO _X absorbent is maintained high (Fig. 3, section III). When the exhaust switching valve is switched again in this state, the air-fuel ratio of the exhaust gas flowing into the NO _X absorbent becomes the lean air-fuel ratio again, and the NO _X
Absorbent resume NO _X absorbent without temperature decreases (Fig. 3, section IV).

[0029] Incidentally, after the reproduction operation of the NO _X absorbent in the embodiment described above is finished, the exhaust air-fuel ratio to continue flowing into _the NO _X absorbent is being maintained at the stoichiometric air-fuel ratio, when particularly long waiting period stops the supply of the regenerating operation after the end once the reducing agent, by which only supplying a reducing agent predetermined period before resuming the NO _X absorbent to maintain the exhaust air-fuel ratio to the stoichiometric air-fuel ratio, NO _X absorbent resume it may be to raise the _the NO _X absorbent temperature before.

Further, in this embodiment, although adjusting the air-fuel ratio of the exhaust gas flowing into the NO _X absorbent waiting only by controlling the supply amount of the reducing agent, the exhaust switching valve together with a reducing agent supply amount 2,22 It is also possible to control the exhaust air-fuel ratio by controlling the opening degree of the exhaust gas and adjusting the amount of exhaust gas flowing in.

[0031]

As described above, the exhaust gas purifying apparatus of the present invention
NO_XNO in standby before resuming absorption_XThe stoichiometric air-fuel ratio for the absorbent
A mixture of the nearby exhaust and reducing agent was supplied.
And the waiting NO_XEffectively prevents temperature drop of absorbent
Stop, NO_XNO at the start of absorption _XHigh absorption capacity of absorbent
This has the effect of being able to maintain a high level.

[Brief description of the drawings]

FIG. 1 is an overall view showing one embodiment of an exhaust gas purification apparatus of the present invention.

FIG. 2 is a view for explaining the NO _X absorption / release action of a NO _X absorbent.

FIG. 3 is a diagram illustrating a cycle of changing an exhaust air-fuel ratio flowing into a NO _X absorbent.

[Explanation of symbols]

1 ... engine 3 ... exhaust passage 3a, 3b ... branch passages 5a, 5b ... NO _X absorbent 2,22 ... exhaust switching valve 11 ... reducing agent supply device (overall)

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI F01N 3/20 ZAB F01N 3/20 ZABN (72) Inventor Kiyoshi Shibata 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation (56) References JP-A-62-106826 (JP, A) WO 93/12863 (WO, A1) (58) Fields investigated (Int. Cl. ⁶ , DB name) F01N 3/08-3/28

Claims (1)

(57) [Claims] In an exhaust passage of claim 1 an internal combustion engine capable of performing combustion of the lean air-fuel ratio, the air-fuel ratio of the inflowing exhaust absorbs NO _X in the exhaust gas when the lean, the reducing agent is supplied to the inflowing exhaust oxygen concentration place _the NO _X absorbent to release the absorbed NO _X when dropped, N after imbibed with NO _X
NO reduces input flow rate of the exhaust gas flowing into the O _X absorbent
A regeneration operation for supplying the reducing agent to the _X absorbent to release the absorbed NO _X , and recovering the exhaust flow rate after the regeneration to
_In the exhaust gas purifying apparatus for an internal combustion engine that repeats the operation of restarting the _X absorption, the reducing agent is supplied to the NO _X absorbent for a predetermined period before the exhaust gas flow rate is recovered and the NO _X absorption is restarted, thereby reducing the NO _X absorption. An exhaust purification device for an internal combustion engine, comprising means for controlling an exhaust air-fuel ratio passing therethrough to a value close to a stoichiometric air-fuel ratio.