JPH06317142A - Exhaust emission control device of internal combustion engine - Google Patents

Abstract

PURPOSE:To reduce the consumption amount of a reducing agent for regenerating an NOx absorber without increasing the consumption amount of lubricating oil and deteriorating a driving feeling. CONSTITUTION:An NOx absorber 15 is disposed in the exhaust pipe 3 of a diesel engine 1 and an engine intake pipe 2 is provided with an intake shutter valve 6 and the exhaust pipe 3 is provided with an exhaust shutter valve 8. An EGR passage 11 for causing engine exhaust to flow back downstream of the intake shutter valve of the intake pipe and an EGR valve 12 are provided. When the intake shutter valve and the exhaust shutter valve are closed and the NOx absorber is reclaimed, part of exhaust is allowed to flow back to the intake side via the EGR passage 11, so that the amount of fresh air flowing in from the outside is greatly reduced without excessively increasing the negative pressure of intake air.

Description

Detailed Description of the Invention

[0001]

The present invention relates to relates to an exhaust purifying apparatus for an internal combustion engine, in the exhaust gas of an internal combustion engine causing combustion of gasoline engines such as lean air causing combustion of a diesel engine or a lean air-fuel ratio in particular NO _X The present invention relates to an exhaust gas purification device that can effectively remove components.

[0002]

2. Description of the Related Art Exhaust gas from an internal combustion engine that burns lean air-fuel ratio
NO in the air_XAs an example of an exhaust purification device that purifies
The one described in Japanese Laid-Open Patent Publication No. 62-106826 is available.
It In the device of the publication, the exhaust passage of the diesel engine
NO in the presence of oxygen_XAbsorbing NO_XPlace absorbent
Absorbent NO_XNO when the absorption efficiency decreases _XSucking
NO by shutting off the exhaust gas inflow to the sorbent_XGuide the reducing agent to the absorbent
NO absorbed by entering_XRelease and reduce purification
is doing.

The device disclosed in the above publication is exhaust gas containing a large amount of oxygen.
Is NO_XNO while preventing it from flowing into the absorbent_XSucking
NO by introducing a reducing agent into the collecting agent_XAbsorbent atmosphere
NO by reducing oxygen concentration_XAbsorbent to NO_XEmit
And reduce this NO by reducing agent _XIs reduced and purified. Shi
However, in the device of the above publication, NO_XNO from absorbent_X
Release and reduction purification (hereinafter NO_X"Regeneration" of absorbent
No when performing_XIt is necessary to block the exhaust gas flow into the absorbent.
Because it is necessary, NO during engine operation_XRelease and purify
If you try, multiple NO_XAbsorbents are arranged in parallel
And sequentially switch to block exhaust gas inflow and NO _XRegeneration of absorbent
It is necessary to secure the exhaust flow path by performing
May be complicated and the mountability on the vehicle may deteriorate.
It

On the other hand, the applicant of the present application_XRegeneration of absorbent
Sometimes introducing a reducing agent with a certain amount of exhaust flowing
NO_XRegenerate the absorbent, NO_XExhausted even when absorbent is regenerated
We have already proposed an exhaust purification system that does not block air inflow
(Japanese Patent Application No. 4-263892). According to this device, N
O_XThe exhaust flow path is secured even when the absorbent is regenerated, and a single NO
_XNO during engine operation using absorbent_XRegenerate the absorbent
Multiple NO_XNeed to provide absorbent
Since it does not have any, it is possible to simplify the device and improve mountability.
it can.

In the device proposed in Japanese Patent Application No. 4-263892, the exhaust system upstream of the NO _x absorbent is provided with oxygen consuming means for consuming oxygen in the exhaust gas, and the oxygen in the exhaust gas flowing into the NO _x absorbent is provided. Decrease the concentration and NO when regenerating NO _X absorbent
_It facilitates the release of _X.

[0006]

[Patent Document 1] Japanese Patent Application No. 4-263
When the regeneration is performed while the exhaust gas is flowing through the NO _x absorbent as in the apparatus of No. 892, it is necessary to consume oxygen contained in the inflowing exhaust gas to reduce the atmospheric oxygen concentration of the NO _x absorbent. In the apparatus of Japanese Patent Application No. 4-263892 mentioned above,
An intake throttle valve is provided in the engine intake passage, and the intake throttle valve is closed during engine braking to throttle the engine intake air amount, and the reducing agent is supplied to the oxygen consuming means provided upstream of the NO _x absorbent to burn it. Oxygen in the exhaust gas is consumed, and the oxygen concentration in the exhaust gas flowing into the NO _x absorbent is reduced to regenerate the NO _x absorbent.

In an engine that burns at a lean air-fuel ratio such as a diesel engine, a large amount of oxygen is contained in the exhaust gas.
When the regeneration is performed with the exhaust flowing through the NO _x absorbent, the amount of the reducing agent required to consume the oxygen in the exhaust becomes very large, which causes a problem that the reducing agent consumption increases. In the above-mentioned Japanese Patent Application No. 4-263892, the amount of oxygen flowing into the engine is reduced by reducing the amount of engine intake air during regeneration of the NO _x absorbent, and the amount of reducing agent required for consuming oxygen in the exhaust gas is reduced. There is.

When the regeneration is performed while the exhaust gas is flowing through the NO _x absorbent, the amount of the reducing agent required for consuming oxygen in the exhaust gas decreases as the engine intake air amount decreases. However, when the intake air throttle amount is used to reduce the engine intake air amount as in the device of the above-mentioned Japanese Patent Application No. 4-263892, the engine intake air amount cannot be significantly reduced and the reducing agent consumption is reduced. There arises a problem that the amount cannot be sufficiently reduced.

That is, in the device of Japanese Patent Application No. 4-263892 mentioned above, when the throttle amount of the intake shutter valve is excessively increased during engine braking, the negative pressure of the intake manifold excessively increases and the negative pressure in the cylinder during the intake stroke. Grows larger. For this reason, deceleration torque more than expected by the driver is generated during engine braking, not only does the deceleration shock increase and the driving sensation worsens, but the increase in cylinder negative pressure causes lubrication between the piston ring and cylinder wall. There is a problem that the oil enters the combustion chamber and the consumption of lubricating oil of the engine increases. Therefore, the throttle amount of the engine intake air amount by the intake shutter valve cannot be increased to a certain extent or more, and it is difficult to sufficiently reduce the reducing agent consumption amount.

In view of the above-mentioned problems, the present invention provides NO _X without causing a deterioration in operating intervals and an increase in engine lubricating oil consumption.
It is an object of the present invention to provide an exhaust emission control device that can reduce the amount of reducing agent consumed during regeneration of the absorbent.

[0011]

According to the present invention, in order to solve the problems], in an exhaust passage of an internal combustion engine causing combustion of lean air-fuel ratio, the air-fuel ratio of the inflowing exhaust gas is the oxygen concentration of the inflowing exhaust absorbs NO _X when the lean NO _X to release the absorbed NO _X when lowered
An absorbent is arranged to absorb NO _x in the exhaust gas,
Lowering the oxygen concentration in the exhaust gas by supplying a reducing agent to _X absorbent, the exhaust purification system of an internal combustion engine to reduce and purify the NO _X with the release of NO _X absorbed from _the NO _X absorbent, the NO There is provided an exhaust gas purification device for an internal combustion engine, which is provided with means for returning at least a part of engine exhaust gas to an engine intake passage when supplying a reducing agent to the _X absorbent.

[0012]

By recirculating the engine exhaust gas to the intake side when the NO _x absorbent is regenerated, the amount of fresh air drawn into the engine from the outside is reduced without increasing the negative pressure of the intake manifold. Therefore, even if the amount of fresh air is significantly reduced, the amount of reducing agent consumed is significantly reduced without increasing the amount of lubricating oil consumed or deteriorating the driving feeling.

[0013]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a diagram showing the configuration of an embodiment of an exhaust gas purification apparatus for an internal combustion engine of the present invention. In FIG. 1, 1
Is a diesel engine, 2 is an engine intake pipe, and 3 is an engine exhaust pipe. An intake shutter valve 6 is provided in the intake pipe 2 of the engine. Further, a casing accommodating the NO _x absorbent 15 is connected to the exhaust pipe 3, and an exhaust shutter valve 8 is provided in the exhaust pipe 3 on the downstream side of the NO _x absorbent 15. examples, an EGR passage 11 for exhaust gas recirculation for connecting _the NO _X absorbent 15 upstream portion of the exhaust pipe 3 and the intake shutter valve 6 downstream portion of the intake pipe 2 is provided. Figure 1
Reference numeral 12 indicates an EGR provided on the EGR passage 11.
It is a valve. A negative pressure actuator 13 is connected to the valve body 12a of the EGR valve 12 to control the operation of the EGR valve 12. The negative pressure actuator 13 includes a negative pressure chamber 13b formed by a diaphragm 13a and a spring 13c for biasing the diaphragm 13a, and the valve body 12a of the EGR valve 12 is connected to the diaphragm 13a. The spring 13c constantly presses the diaphragm 13a in a direction in which the valve body 12 is in close contact with the valve seat.
Is closed by the valve body 12, and the exhaust gas does not flow back from the EGR passage 11 to the intake passage 2. However, during normal operation, the negative pressure chamber 13b of the negative pressure actuator 13 receives a negative pressure from an appropriate negative pressure source according to the operating state. Is supplied, the EGR valve 12 can be opened and exhaust gas recirculation can be performed. Further, in the present embodiment, the urging force of the spring 13c is such that when the pressure in the intake pipe 2 decreases and the difference between the exhaust pressure in the EGR passage 11 and the intake pressure exceeds a predetermined value, It is appropriately set so as to push up the valve body 12a against the biasing force and flow into the intake pipe 2.

The intake shutter valve 6 and the exhaust shutter valve 8 are valves of a type such as a butterfly valve having a low resistance when fully opened, and are kept fully open during normal operation of the engine so that intake resistance and exhaust resistance are not generated. Further, the intake shutter valve 6 is provided with an actuator 7 of an appropriate type such as a negative pressure actuator, a stepper motor, etc., and is closed to a predetermined opening during a NO _x absorbent 15 regeneration operation described later to throttle the intake pipe 2 to reduce the NO _x absorbent. The exhaust flow rate passing through 15 is reduced. Similarly, the exhaust shutter valve 8 is provided with an actuator 9 of an appropriate type, and is closed to a predetermined opening when the NO _x absorbent 15 is regenerated, and the exhaust pipe 3 is throttled to increase the exhaust pressure.
The flow rate of the exhaust gas flowing back to the intake pipe 2 through the GR passage 11 is increased.

Reference numeral 30 in the drawing denotes an electronic control unit (ECU) of the engine 1. ECU30 is CPU21,
The RAM 22, the ROM 23, the input port 24, and the output port 25 are connected to each other by a bidirectional bus 26, and are composed of a well-known digital computer. In addition to the control, in this embodiment, the fuel injection control for the regeneration operation of the NO _X absorbent 15 and the opening / closing control of the intake shutter valve 6 and the exhaust shutter valve 8 are performed. For these controls, signals such as engine speed, accelerator opening, and exhaust temperature are input to input ports of the ECU 30 from sensors (not shown).

The NO _x absorbent 15 uses, for example, alumina as a carrier, and potassium K, sodium Na, etc. are provided on the carrier.
, 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. Has been done. This _the NO _X absorbent 15 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 exhaust air-fuel ratio mentioned above means here N
The exhaust passage on the upstream side of the O _X absorbent 15 and the engine combustion chamber,
It means the ratio of the total amount of air and the total amount of fuel supplied to the intake passage and the like. Therefore, 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) when fuel, reducing agent or air is not supplied to the exhaust passage or intake passage on the upstream side of the NO _x absorbent 15. .

In this embodiment, since the diesel engine is used, the exhaust air-fuel ratio during normal operation is lean, and the NO _X absorbent 15 absorbs NO _{X in} the exhaust.
Further, when the oxygen concentration in the exhaust gas decreases due to the operation described later, the NO _X absorbent 15 releases the absorbed NO _X.
There are some points where the detailed mechanism of this absorption / release action is not clear. However, it is considered that this absorbing / releasing action is performed by the mechanism shown in FIG. Next, this mechanism will be described by taking as an example the case where platinum Pt and barium Ba are supported on a carrier, 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 Figure 2 (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
2 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_XAbsorbent 1
Absorbed within 5.

Therefore, NO ₂ is produced on the surface of platinum Pt as long as the oxygen concentration in the inflowing exhaust gas is high, and NO ₂ is absorbed in the absorbent and nitrate ion NO ₃ unless the NO _X absorption capacity of the absorbent is saturated. ^- is generated. In contrast the reaction with the amount of NO ₂ oxygen concentration is lowered in the inflowing exhaust gas decreases the reverse (NO ₃ ^- → NO ₂₎ proceeds, the nitrate ions NO ₃ of the absorbent ^- is NO ₂ It is released from the absorbent in the form. That is, when the oxygen concentration in the inflowing exhaust gas decreases, NO
NO _X is released from the _X absorbent 15.

On the other hand, when reducing components such as HC and CO are present in the inflowing exhaust gas, these components are 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, the NO released from the NO _X absorbent 15 due to the decrease in the oxygen concentration in the exhaust gas.
₂ is reduced by reacting with HC and CO as shown in Fig. 2 (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. Accordingly HC in the inflowing exhaust gas, NO _X from _the NO _X absorbent 15 in a short time when the CO component is present is released,
Will be reduced.

That is, HC and CO in the inflowing exhaust gas first react with O ₂ ⁻ or O ²⁻ on platinum Pt immediately to be oxidized, and then O ₂ ⁻ or O ²⁻ on platinum Pt are consumed. the HC, NO _X discharged from the released NO _X and the engine from the absorbent by CO is reduced even yet HC, any remaining CO is. Therefore, N
The amount of reducing agent to be supplied to the NO _x absorbent in order to release and reduce (regenerate) O _x is the amount necessary to sufficiently reduce the oxygen concentration in exhaust gas due to oxygen consumption due to oxidation, and the amount of NO _x.
This is the sum of the amount required to reduce all the NO _x released from the _X absorbent 15. However, in a diesel engine, the air-fuel ratio of the exhaust gas is always lean, so if NO _x is released or reduced while the exhaust gas is flowing through the NO _x absorbent 15, the amount of the reducing agent for consuming oxygen in the exhaust gas is small. Will be very large. Therefore, in this embodiment, the intake shutter valve 6 provided in the intake pipe 2 is closed during regeneration of the NO _X absorbent 15 to reduce the amount of fresh air drawn into the engine 1 from the outside, and the exhaust pipe 3 The exhaust shutter valve 8 provided in the intake valve is closed to recirculate the exhaust gas through the EGR passage 11 to the intake pipe downstream of the intake shutter valve 6 to generate N
The amount of oxygen flowing into the O _X absorbent is reduced.

By performing exhaust gas recirculation when the intake shutter valve 6 is closed, most of the exhaust gas is recirculated from the upstream side of the NO _x absorbent 15 to the downstream side of the intake shutter valve 6 and a small amount of new exhaust gas flowing from the intake shutter valve 6. The air is mixed with the air and is sucked into the engine 1. By appropriately setting the amount of the recirculated exhaust gas, the inflow of fresh air can be significantly increased without excessively reducing the amount of the intake air sucked into the engine 1. It can be reduced. Therefore, according to the present embodiment, the amount of the reducing agent for consuming the inflowing oxygen is reduced while preventing the intake negative pressure from excessively increasing to increase the lubricating oil consumption amount and the deterioration of the driving feeling. It becomes possible to do.

In this embodiment, the fuel (light oil) of the engine 1 is used as the reducing agent supplied to the NO _x absorbent 15, and the intake shutter valve 6 is closed and the fuel injection valve 4 is operated in the same manner as in the normal operation. In addition, the reducing agent is supplied to the NO _x absorbent 15 by injecting fuel into the combustion chamber. At this time, the fuel injection amount from the fuel injection valve 4 consumes all oxygen in the fresh air flowing from the intake shutter valve 6, and
The amount is required to reduce the NO _X absorbed by the NO _X absorbent 15.

In this embodiment, the exhaust gas recirculation is performed.
When throttled intake air only by the intake shutter valve 6
Compared to, it is possible to reduce the inflow of fresh air to about 1/3
The amount of reducing agent for oxygen consumption
Will be reduced. Next, the operation of the exhaust purification system of this embodiment will be described.
explain about. In this embodiment, the ECU 30 is NO_XSucking
NO only when the regenerating operation execution condition of the collecting agent 15 is satisfied_X
The regeneration operation of the absorbent 15 is performed. Here, NO of this embodiment
_XThe conditions for executing the regeneration of the absorbent are as follows: (1) The driver operates the accelerator.
Not working, and the engine speed is higher than a specified value.
(That is, the engine is in the brake state)
And), (2) Check that the engine exhaust temperature is above a specified value.
And (3) NO_XAbsorbent NO _XAbsorption amount exceeds a specified value
That is, all the above conditions are met.
Only if NO_XThe absorbent is regenerated.

Since the NO _x absorbent is regenerated only when the engine is decelerated (condition (1) above), it is necessary to close the intake shutter valve and the exhaust shutter valve to reduce the intake air amount during regeneration. This is because if regeneration is performed during operation, torque shock will occur and the drivability will deteriorate.
Further, the reason why the exhaust gas temperature is equal to or higher than the predetermined value (the above-mentioned condition (2)) is that the NO _X absorbent must reach the activation temperature at which the NO _X release and the reducing action are activated. Further, when the NO _X absorption of the NO _X absorbent that is equal to or higher than a predetermined value (the condition (3)) required to reproduce execution conditions are you doing truly reproduced avoiding frequent regeneration operations This is because only the reproduction operation is performed.

It should be noted, NO _X absorption of the NO _X absorbent, for example, advance the engine load emissions of the NO _X from the engine per unit time (accelerator opening) to ROM23 the ECU30 as a function of engine speed, etc. Remember
Seeking NO _X emissions by the function of the accelerator opening and the rotational speed at regular intervals, which in integrating the multiplied by the constant factor as NO _X absorption of _the NO _X absorbent in said predetermined time Required by.

When all of the above reproduction conditions are satisfied,
The ECU 30 drives the actuator 7 of the intake shutter valve 6 and the actuator 9 of the exhaust shutter valve 8 to close the intake shutter valve 6 and the exhaust shutter valve 8. By closing the intake shutter valve 6, the amount of air taken into the engine from the intake pipe 2 is reduced, and the amount of fresh air flowing in is reduced. Further, closing the intake shutter valve 6 increases the intake pipe negative pressure on the downstream side of the shutter valve 6, but at the same time the exhaust shutter valve 8 is closed and the exhaust pressure increases, so that the valve body 12a of the EGR valve 12 is closed. Is exerted by a force due to the differential pressure between the exhaust pipe pressure and the intake pipe negative pressure, and the valve body 12a is separated from the valve seat even when the negative pressure is not supplied to the negative pressure chamber 13b of the negative pressure actuator 13. Exhaust gas flows into the intake pipe 2 from 11.

Therefore, even when the intake shutter valve 6 is closed to greatly reduce the inflow of fresh air, the intake negative pressure of the engine does not increase above a certain value, and the consumption of lubricating oil increases and the driving feeling deteriorates. Absent. Further, the ECU 30 controls the fuel injection amount from the fuel injection valve 4 to a preset amount at the same time when the intake shutter valve 6 is closed. This fuel injection amount is the amount necessary to consume all the oxygen in the fresh air flowing through the intake shutter valve 6 in the closed state, and NO _X.
It is set to the sum of the amount required to reduce the NO _X absorbed by the absorbent 15. The fuel amount required for reduction of the NO _X absorbed in the NO _X absorbent is less than the amount of fuel required to consume the oxygen in the fresh air, NO _X
The amount of fuel (reducing agent) consumed at the time of regeneration of the absorbent is substantially determined by the amount of fresh air flowing in. Further, when the intake shutter valve 6 is closed, the flow through the valve 6 is choked, and the amount of fresh air that flows in is determined by the negative pressure of the intake manifold. Therefore, in this embodiment, the flow rate is substantially constant regardless of the engine speed. . Therefore, the amount of fuel injected from the fuel injection valve 4 when the NO _X absorbent 15 is regenerated can be set to a constant value regardless of the engine speed.

As described above, the amount of fresh air is reduced and the combustion chamber
By injecting fuel into the cylinder, the injected fuel is
Fuel that did not burn in the cylinder
NO _XAcid in the exhaust gas because it burns due to the catalytic action of the absorbent
Element is consumed, and the above NO_XNO from absorbent_XRelease of
Withdrawals and returns are made. NO above_XRegeneration operation of absorbent
When the regeneration operation is performed for a predetermined time, or when the
Due to the change, the above playback operation execution conditions are no longer met
To end. If it is determined that the playback operation has finished,
ECU 30, the intake shutter valve 6 and the exhaust shutter are
Open the target valve 8 and restart the normal fuel injection control.
It As a result, the EGR valve 12 is closed and the engine 1 is
Return to normal operating conditions.

In the above embodiment, the fuel injection amount at the time of regeneration of the NO _X absorbent is controlled to a constant value, but in reality, a part of the fuel injected together with the exhaust gas also recirculates to the intake side and NO.
The amount of fuel required decreases as time passes from the start of the _X- absorbent regeneration operation. Therefore, the oxygen concentration in the exhaust oxygen concentration sensor for detecting oxygen concentration in the exhaust to the exhaust pipe on the downstream side of the NO _X absorbent 15 is disposed, passes through _the NO _X absorbent 15 is maintained at a predetermined level Thus, the fuel supply amount can be reduced by feedback-controlling the fuel injection amount at the time of regeneration of the NO _X absorbent (so that the exhaust air-fuel ratio becomes considerably rich).

Further, in the above embodiment, the reducing agent (fuel) is supplied to the NO _X absorbent by the fuel injection from the fuel injection valve 4, but a reducing agent supply device is separately provided to supply the reducing agent to the NO _X absorbent. It may be supplied. In this case, for example,
A reducing agent supply nozzle opening to shutter valve 6 downstream of the intake pipe 2 is provided, and supplies the reducing agent into the intake pipe by using an intake pipe negative pressure during _the NO _X absorbent regeneration, or NO _X
It is also possible to provide a supply nozzle in the exhaust pipe upstream of the absorbent and inject the reducing agent into the exhaust pipe by a pressurizing means such as a pump.

Next, FIG. 3 shows another embodiment of the present invention. 3, the same elements as those of the embodiment of FIG. 2 are designated by the same reference numerals. In the embodiment of FIG. 2, the EGR passage 11 has N
O _X absorbent 15 had been connected to the exhaust passage upstream of, EGR passage 11 in this embodiment is connected to an exhaust passage downstream of the NO _X absorbent 15, the exhaust shutter valve as _the NO _X absorbent 15 2 is different from the embodiment of FIG. 2 in that exhaust gas is recirculated from a portion between 8 and 8 to the intake side.

In the embodiment of FIG. 2, for example, when combustion does not occur in the engine 1 due to insufficient compression due to a decrease in suction pressure, the total amount of fuel supplied is changed to NO _x absorbent 1.
Therefore, the HC component of the fuel may flow out to the downstream side without being burned depending on the conditions such as the exhaust temperature. In this embodiment, since the exhaust gas is taken out from the downstream side of the NO _x absorbent 15 and is recirculated to the intake side, the unburned HC component that has passed through the NO _x absorbent 15 can be recirculated together with the exhaust gas. _The fuel can be effectively used when the _X absorbent 15 is regenerated.

Further, in the embodiment of FIG. 2, in order to secure the flow of exhaust gas through the NO _x absorbent 15, a certain amount of fresh air is introduced from the intake shutter valve 6 and the amount of fresh air from the exhaust shutter valve 8 is increased. it is necessary to flow out the corresponding amount of the exhaust to the outside, but in this embodiment _the NO _X absorbent 15
Since the exhaust gas is taken out from the downstream side and is recirculated to the intake side, the flow of the exhaust gas through the NO _x absorbent 15 can be secured regardless of the amount of fresh air introduced from the intake shutter valve 6. Therefore, the present embodiment has an advantage that the amount of fresh air can be reduced significantly more than the embodiment of FIG. 2 and the reducing agent consumption amount can be further reduced. The regeneration operation of the NO _X absorbent 15 in this embodiment is substantially the same as that in the embodiment shown in FIG. 2, and therefore its explanation is omitted here.

The case where the exhaust gas purification apparatus for an internal combustion engine according to the present invention is applied to a diesel engine has been described above. However, the present invention is not limited to application to a diesel engine, but to a gasoline engine that performs lean combustion. It goes without saying that is also applicable.

[0037]

The exhaust gas purifying apparatus for an internal combustion engine according to the present invention has N
By providing a means for recirculating at least a part of the engine exhaust gas to the engine intake side during the regeneration operation of the O _X absorbent, it is possible to increase the consumption of the engine lubricating oil and the deterioration of the driving feeling.
O _X absorbent significant reduction of the reducing agent consumption during reproduction the effect that can be achieved.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of an exhaust emission control device of the present invention.

FIG. 2 is a diagram illustrating the NO _X absorption and release action of a NO _X absorbent.

FIG. 3 is a diagram showing an embodiment of the exhaust emission control device of the present invention different from that of FIG.

[Explanation of symbols]

1 ... Diesel engine 2 ... Engine intake pipe 3 ... Engine exhaust pipe 6 ... Intake shutter valve 8 ... Exhaust shutter valve 11 ... EGR passage 12 ... EGR valve 15 ... NO _X absorbent 30 ... Electronic control unit

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Office reference number FI technical display location F02D 9/02 341 G 9/04 E F02M 25/07 B

Claims (1)

[Claims] 1. The exhaust passage of an internal combustion engine that burns lean air-fuel ratio absorbs NO _x when the air-fuel ratio of the inflowing exhaust gas is lean and absorbs N _x when the oxygen concentration of the inflowing exhaust gas decreases.
NO _X absorbent that releases O _X is placed and NO _{X in} exhaust gas
To absorb the exhaust of an internal combustion engine with the release of NO _X absorbed and thus reduce the oxygen concentration in the exhaust gas _the NO _X absorbent to reduce and purify the NO _X by feeding a reducing agent to the _the NO _X absorbent in purifier, the NO in the _X absorbent when supplying a reducing agent, an exhaust purification device for an internal combustion engine, characterized in that it comprises means for recirculating at least a portion of the engine exhaust to an engine intake passage.