JP3419209B2 - Exhaust gas purification device for internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [0001] BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to purification of exhaust gas from an internal combustion engine.
Related to the device. [0002] 2. Description of the Related Art In a combustion chamber of each cylinder and an intake passage.
The ratio of the total air amount to the total supplied fuel amount is defined as the engine air-fuel ratio.
In other words, conventionally, in the exhaust passage connected to each cylinder,
Arrange the three-way catalyst and adjust the engine air-fuel ratio of each cylinder to the stoichiometric air-fuel ratio.
Or richly controlled exhaust gas of a spark ignition gasoline engine
A gasifier is known. When the engine air-fuel ratio is lean
When the exhaust gas flows into the three-way catalyst, the three-way catalyst
Oxide NO_XWithout purifying NO_XReleased into the atmosphere
Will be issued. Therefore, in this exhaust gas purification device,
Fuel ratio is set to stoichiometric air-fuel ratio or rich in three-way catalyst
NO_XIs to be purified well. On the other hand, the engine air-fuel ratio of each cylinder is
To reduce fuel consumption as much as possible.
No. However, the above-mentioned exhaust gas purification system requires lean operation.
When done, NO as described above_XCannot be purified well. So
Here, the exhaust passage upstream of a certain position in the exhaust passage, the fuel
The total amount of fuel supplied to the firing chamber and the intake passage
The ratio of the amount of air is called the exhaust air-fuel ratio of the exhaust flowing through that position.
Then, the cylinders of the multi-cylinder internal combustion engine are changed to the first and second cylinders.
Divided into groups and connected to a first cylinder group.
When the exhaust air-fuel ratio of the inflowing exhaust gas is rich in the exhaust passage,
In the exhaust that flows in_XTo NH_ThreeGenerate ternary
A first exhaust passage downstream of the three-way catalyst;
And the second exhaust passage connected to the cylinder group of
NO in exhaust gas flowing into the flow exhaust passage_XAnd NH_ThreeAnd purify
The exhaust gas purifying catalyst, which is to be
A rich operation in which the engine air-fuel ratio is rich is performed.
Lean operation in which the engine air-fuel ratio is lean for each cylinder in the cylinder group
An exhaust gas purifying apparatus for performing the above-described process is known (Japanese Patent Laid-Open No. 8-45 / 1996).
No. 22). With this exhaust gas purification device,
Fuel consumption by making many cylinders run lean
Rate while reducing as much as possible
Is conducted to the three-way catalyst to exhaust NH_ThreeGenerate a
And the NO generated in the cylinder where the lean operation is performed_X
And this NH_ThreeAnd the reaction in the exhaust purification catalyst
NO_XTo purify. [0004] As described above, the second
The lean operation is performed in each cylinder of the cylinder group of
Fuel consumption rate can be reduced by increasing the number of cylinders in the cylinder group
Can be. However, the number of cylinders in the second cylinder group is large.
NO flowing into the exhaust purification catalyst_XLarge amount
And the number of cylinders in the first cylinder group is reduced.
NH flowing into the gas purification catalyst_ThreeThe amount is reduced and therefore
NO_XNH required for purification_ThreeAmount for exhaust purification catalyst
NO in the exhaust purification catalyst because it is not supplied_XEnough
There is a problem that it cannot be purified. [0005] [MEANS FOR SOLVING THE PROBLEMS]
According to the present invention, the multi-cylinder internal combustion engine includes the first cylinder group and the second cylinder group.
The first cylinder group is divided into two cylinder groups.
NO_XTo NH_ThreeTo produce this NH_ThreeBy the second
NO in exhaust of cylinder group_XInternal combustion engine that purifies air
In the exhaust gas purification apparatus of the first aspect, the first cylinder group has at least two cylinders.
The sub-cylinder group is further divided into two sub-cylinder groups.
Exhaust air-fuel ratio of exhaust gas flowing into each connected sub-exhaust passage
In the exhaust that flows in when the air is rich_XTo NH_ThreeTo
NH generated_ThreeExhaust air-fuel ratio of generated catalyst and inflowing exhaust
In exhaust gas that flows in when lean_XOcclude and flow
It is occluded when the exhaust air-fuel ratio of the incoming exhaust gas becomes rich
NO_XAnd an occluding material for releasing NH 3_ThreeGenerated catalyst
In the sub exhaust passage downstream of the corresponding storage material or
NH3_ThreeEach downstream of the production catalyst
A second exhaust passage connected to the sub-exhaust passage and the second cylinder group;
In the merged exhaust passage that merges with the
NO_XAnd NH_ThreeAn exhaust purification catalyst that purifies
In the sub-exhaust passage or sub-cylinder group upstream of the storage material, respectively
Make the exhaust air-fuel ratio of the exhaust flowing into the corresponding storage material rich.
Or lean exhaust air-fuel ratio control means
And at least the second cylinder group performs a lean operation,
By controlling the air-fuel ratio control means, the exhaust gas flowing into some occlusion materials is controlled.
By making the exhaust air-fuel ratio of air rich,
NO stored_XRelease together under this occlusion material
Flow NH_ThreeNH in the production catalyst_ThreeGenerate
To the exhaust purification catalyst_ThreeAnd flow to the remaining occlusion material.
By making the exhaust air-fuel ratio of the
NO for occlusion material_XExhaust air-fuel ratio of the inflowing exhaust gas
Exhaust gas purification by sequentially changing the storage material that is rich
NH_ThreeIs always supplied. Sand
C, NO_XIs temporarily stored in the storage material, and then stored.
NO_XTo release this NO_XTo NH_ThreeGenerate
So that a relatively large amount of NH is added to the exhaust purification catalyst.
_ThreeIs supplied. NO_XOcclusion other than occlusion material that should release
NO for wood_XStorage effect, and therefore NO_XTo
Exhaust gas purification by sequentially changing the storage material to be released
Relatively large amount of NH in the catalyst_ThreeIs always supplied. [0006] DETAILED DESCRIPTION OF THE INVENTION In general, nitrogen oxides NO_XIn one
Nitric oxide NO, NO 2_Two, Dinitrogen tetroxide N_TwoO
_Four, Nitrous oxide N_TwoO and the like may be included. In the following, N
O_XMainly NO, NO_TwoExplain the case
However, the exhaust gas purification apparatus of the present invention purifies other nitrogen oxides.
You can also. FIG. 1 shows the present invention applied to a diesel engine.
Shows the case. With reference to FIG.
Cylinder # 1, cylinder # 1, cylinder # 2, cylinder # 3
The cylinder # 3 and the fourth cylinder # 4 are provided. Each cylinder # 1 to #
4 is a common surge via the corresponding intake branch 2
The surge tank 3 is connected to the intake duct 4
The air flow meter 5 is connected to the air flow meter 5. Air flow meter
5 is connected to the air cleaner 6. For each cylinder # 1 to # 4
Supplies fuel directly into the cylinder or via a sub-chamber (not shown)
The fuel injection valve 7 is mounted. Each fuel injection
The valve 7 is based on an output signal from the electronic control unit 20
Controlled. The cylinders # 1 to # 4 correspond to the respective cylinders.
Connected to a common exhaust manifold 9 via an exhaust branch 8
The exhaust manifold 9 has a built-in exhaust purification catalyst 10.
It is connected to the medium converter 11. Furthermore, the first cylinder # 1
And NO in the exhaust branch pipe 8 of the second cylinder # 2._X
The storage reduction catalysts 12a and 12b are respectively arranged. Figure
In the first diesel engine, the diesel engine is the first cylinder group
1a and a second cylinder group 1b.
The cylinder group 1a includes the first cylinder # 1 and the second cylinder # 2.
And the second cylinder group 1b is the third cylinder # 3 and the fourth cylinder
It is composed of cylinder # 4. Also, the first cylinder group 1a
Are divided into a first sub-cylinder group 1aa and a second sub-cylinder group 1ab.
The first sub-cylinder group 1aa is the first cylinder # 1
The second sub-cylinder group 1ab is the second cylinder #
2 is comprised. On the other hand, the exhaust manifold 9 merges
It constitutes an exhaust pipe. Still referring to FIG. 1, the first cylinder group 1
a intake branches of the first cylinder # 1 and the second cylinder # 2 constituting
The corresponding actuators 13a, 1
3b driven by intake throttle valves 14a, 14b
Is done. The actuators 13a and 13b shown in FIG.
Magnetic type, but use negative pressure type actuator
You can also. These intake throttle valves 14a, 14b are usually
It is kept fully open. Each actuator 13
a and 13b are based on the output signal from the electronic control unit 20.
It is controlled according to. By the way, although not shown, FIG.
The diesel engine has an accumulator for fuel,
The discharged fuel is supplied to each fuel injection valve 7 through the accumulator.
I try to distribute. Each fuel injection valve 7 is an electromagnetic
It has a needle driven by a solenoid.
When the electromagnetic solenoid is energized, the needle displaces and fuel
Fuel injection is started by opening the injection valve nozzle.
When the electromagnetic solenoid is de-energized, the needle
By shutting off, the fuel injection is stopped. in this way
Then, in one combustion cycle of each cylinder, the fuel is injected multiple times.
Firing. The electronic control unit (ECU) 20 is a digital
And a computer via the bidirectional bus 21.
ROM (Read Only Memory) 22, R connected to each other
AM (random access memory) 23, CPU (microphone)
Processor, 24, an input port 25, and an output port.
２６26 is provided. Air flow meter 5 is
An example output voltage is generated, and this output voltage is
7 to the input port 25. Correspond to each
NO_XNo. 1 cylinder upstream of the storage reduction catalysts 12a and 12b
In the exhaust branch pipes 8 of the # 1 and # 2 cylinders, proportional to the exhaust gas temperature
Temperature sensors 28a and 28b that generate
Output voltage of these temperature sensors 28a and 28b.
The pressure is passed through the corresponding AD converters 29a and 29b, respectively.
Input to the input port 25. Also, the input port 25
Output every time the crankshaft rotates for example 30 degrees
A crank angle sensor 30 that generates a pulse is connected.
The CPU 44 determines the engine speed based on the output pulse.
Is calculated. Further, the accelerator pedal is connected to the input port 25.
To generate an output voltage proportional to the amount of depression
An inset amount sensor 32 is connected. On the other hand, the output port 26
Represents each fuel injection valve via the corresponding drive circuit 33.
7. Connected to each actuator 13a, 13b
It is. In the example shown in FIG._XStorage reduction catalyst
12a and 12b are NO_XOcclusion and NH_ThreeWith generating action
Has both. That is, NO_XStorage reduction catalyst 12
a and 12b are NOs in the exhaust gas_XTemporarily store
Storage material and NO in inflowing exhaust gas_XTo NH_ThreeGenerate
NH_ThreeAnd the formed catalyst at the same time. This NO _X
The storage reduction catalysts 12a and 12b are formed on the surface of the carrier.
For example on a washcoat layer of alumina
Potassium K, sodium Na, lithium Li, cesium
Alkali metals such as Cs, barium Ba, calcium
Alkaline earths such as Ca, lanthanum La, yttries
Selected from rare earths such as U and transition metals such as Fe.
Palladium Pd, platinum Pt,
It is formed by supporting a noble metal such as rhodium Rh.
You. This NO_XThe storage reduction catalyst is used for exhaust air
Fuel ratio is stoichiometric air-fuel ratio (A / F) S (= 14.6, air excess
Exhaust gas flowing when leaner than the excess ratio λ = 1.0)
NO_XAnd reduce the oxygen concentration in the inflowing exhaust
That is, for example, the exhaust air-fuel ratio of the inflowing exhaust
Absorbs when it becomes richer than air-fuel ratio (A / F) S
NO_XReleases NO_XPerforms the absorption and release action. This NO_XThe storage reduction catalyst in the engine exhaust passage
This NO_XThe storage reduction catalyst is actually NO_Xof
Performs absorption and release, but the detailed mechanism of this absorption and release
There are some parts that are not clear. However, this
The absorption / release action is performed by the mechanism described below.
It is thought that it is. Next about this mechanism
When platinum Pt and barium Ba are supported on a carrier
As an example, we explain other precious metals, alkali metals,
The same mechanism is used when using alkaline earths, rare earths, and transition metals.
It becomes a rhythm. That is, NO_XFlow into storage reduction catalyst
The exhaust air-fuel ratio of the exhaust gas is lower than the stoichiometric air-fuel ratio (A / F) S.
That is, the oxygen concentration in the exhaust gas greatly increases.
Then these oxygen O_TwoIs O_Two ^-Or O^2-In the form of platinum Pt
Adheres to the surface of On the other hand, NO in the exhaust gas is a table of platinum Pt.
O on the surface_Two ^-Or O^2-Reacts with NO_Two(2N
O + O_Two→ 2NO_Two). NO generated next_TwoPart of
Is oxidized on platinum Pt while NO_XStorage in the storage reduction catalyst
Collected and combined with barium oxide BaO and nitrate ions
NO_Three ^-NO in the form of_XIt diffuses into the storage reduction catalyst. this
NO _XIs NO_XOccluded in the storage reduction catalyst
You. On the other hand, NO_XFlow into storage reduction catalyst
Oxygen concentration in exhaust gas decreases and NO_TwoProduction decreases
And the reaction is in the opposite direction (NO_Three ^-→ NO_Two) And thus
NO _XNitrate ion NO in the storage reduction catalyst_Three ^-Is NO_Twoof
NO in form_XReleased from the storage reduction catalyst. That is, N
O_XOxygen concentration in exhaust gas flowing into the storage reduction catalyst decreases
Then, for example, NO_XExhaust gas flowing into the storage reduction catalyst
NO when air-fuel ratio goes from lean to rich_XStorage reduction catalyst
From NO_XIs released. Also, NO_XThe storage reduction catalyst is
NO when the exhaust air-fuel ratio of the air is richer than the stoichiometric air-fuel ratio
_XNO on storage reduction catalyst_XThat is,
NO _XAnd NO_XNO released from the storage reduction catalyst_X
At least part of ammonia NH_ThreeConvert to this
NH in case_ThreeThe generation mechanism is not always clear
No, but no_XNO on storage reduction catalyst_XSome of the following
By the reaction of the formulas (1) and (2) shown in_ThreeConverted to
It is believed that. [0017] 5H_Two+ 2NO → 2NH_Three+ 2H_TwoO (1) 7H_Two+ 2NO_Two→ 2NH_Three+ 4H_TwoO (2) In contrast, the remaining NO_XIs the following equation (3)
Nitrogen N by the reaction of (6) _TwoIs thought to be reduced to
I have. 2CO + 2NO → N_Two+ 2CO_Two        (3) 2H_Two+ 2NO → N_Two+ 2H_TwoO (4) 4CO + 2NO_Two→ N_Two+ 4CO_Two        (5) 4H_Two+ 2NO_Two→ N_Two+ 4H_TwoO (6) Therefore NO_XExhaust air of exhaust gas flowing into the storage reduction catalyst
When the fuel ratio is rich, the NO_X
And released NO_XIs NH_ThreeOr N_TwoAny of
, Ie, NO_XNO from the storage reduction catalyst_XBut
It has been prevented from being discharged. NO_XNO on storage reduction catalyst_XIs NH_ThreeTo
The conversion efficiency ETA when converted is as shown in FIG.
NO_XExhaust air-fuel ratio of exhaust gas flowing into the storage reduction catalyst is theoretical
It increases as the air-fuel ratio (A / F) S decreases.
If it becomes smaller, it is maintained at a constant value. this is,
As the degree of richness increases, the above equations (3) to (3)
N of (6)_TwoThe above-mentioned formula (1) and
NH of (2)_ThreeThis is because the formation reaction becomes dominant.
Has been obtained. In the example shown in FIG._XOcclusion reduction
The exhaust air-fuel ratio of the exhaust gas flowing into the catalyst is about 13.8 (air
When the modulus λ is smaller than about 0.95), the conversion efficiency ET
A is maintained at a constant value. In the diesel engine shown in FIG._X
The exhaust air-fuel ratio of the exhaust gas flowing into the storage reduction catalyst is rich.
As much NH as possible_ThreePreferably can produce
New So, NO_XFor the storage reduction catalysts 12a and 12b
Is NO_XTo NH_ThreeP with high conversion efficiency to
NO carrying at least d_XThe storage reduction catalyst is used
You. On the other hand, NO carrying rhodium Rh_XOcclusion
NH on reduction catalyst_ThreeIs suppressed. Therefore N
O_XThe storage reduction catalysts 12a and 12b carry rhodium Rh.
Those not possessed are preferred. On the other hand, the exhaust purification catalyst 10
NH_ThreeAnd NO_XAnd at the same time purify
You. The exhaust purification catalyst 10 is not necessarily NH_ThreeWith adsorption function
Although it is not necessary that the exhaust purification catalyst
10 is NH in the exhaust gas flowing into _ThreeTemporarily store NH
_ThreeAdsorption and NO in oxidizing atmosphere_XTouch to reduce
WH with both medium action_ThreeNO by_xSelective touch
Medium (hereinafter NO_xFormed from 10a)
Is done. This NO_xThe selective reduction catalyst 10a is, for example, a carrier.
Zeolite supporting copper (hereinafter referred to as copper zeolite)
Zeolite supporting platinum and copper
(Hereinafter referred to as platinum / copper zeolite) or iron
A so-called zeolite system that supports zeolites
It is formed from a denitration catalyst. However, NO_xSelective reduction
Catalyst 10a, zeolite, silica, silica alumina,
Including solid acids such as titania and iron Fe, copper Cu, etc.
Transition metals or noble metals such as platinum Pt and palladium Pd
Or a catalyst carrying a genus or at least two of them
Can also be formed from a catalyst in which Some
Is a catalyst containing at least a noble metal
(Hereinafter referred to as precious metal catalyst), or precious metal catalyst and NH
_ThreeIt may be formed from a catalyst in combination with an adsorption oxidation catalyst.
No. NO_xThe selective reduction catalyst 10 a
NH in_ThreeIs adsorbed and the NH_ThreeLow concentration
In the exhaust gas flowing in_XSucks when there is
NH wearing_ThreeAt this time, in an oxidizing atmosphere
And, for example, NO_xOf the exhaust gas flowing into the selective reduction catalyst 10a.
If the exhaust air-fuel ratio is lean, this NH_ThreeOxidizes the whole amount of
You. Or NO in the inflowing exhaust_XAnd NH_ThreeMixed with
Then NO_xNH in the selective reduction catalyst 10a_ThreeIs NO
_XIs oxidized. NH in this case_ThreeOxidation mechanism
Is not always clear, but NO_xSelective reduction catalyst
NH released from 10a_ThreeOf the following equations (7) to (10)
It is believed that it is oxidized by the reaction. [0022]   4NH_Three+ 7O_Two      → 4NO_Two+ 6H_TwoO (7)   4NH_Three+ 5O_Two      → 4NO + 6H_TwoO (8)   8NH_Three+ 6NO_Two    → 12H_TwoO + 7N_Two        (9)   4NH_Three+ 4NO + O_Two→ 6H_TwoO + 4N_Two        (10) In the denitration reactions of equations (9) and (10), equations (7) and (10)
NO generated by the reaction of (8)_XAnd NO_xSelective touch
NO in exhaust gas flowing into the medium 10a_XIs reduced. Incidentally, the engine air-fuel ratio of each cylinder # 1 to # 4
Is lean, that is, lean in each of cylinders # 1 to # 4.
Driving is performed. Engine air-fuel ratio of diesel engine
It is not desirable to perform rich rich operation from the cylinder
Smoke and particulates are emitted. So figure
1 diesel engine always runs lean in each cylinder
To do. Therefore, the emissions from each cylinder
The exhaust air-fuel ratio of the exhaust gas is basically lean
You. In each cylinder, the pressure around the compression top dead center is usually
The fuel injection from the fuel injection valve 7 is performed once. This fuel
The engine output is obtained by the combustion of. Below
Describes such a fuel injection action as normal injection. What
The fuel injection amount in normal injection is, for example, the accelerator pedal
As a function of the amount of depression DEP of the cylinder 31 and the engine speed N
Stored in the ROM 22 in advance. Next, the exhaust gas purification method of the diesel engine shown in FIG.
The method will be described. In the diesel engine of FIG.
_XThe exhaust air-fuel ratio (A) of the exhaust gas flowing into the storage reduction catalyst 12a
/ F) N1 is enriched and NO_XStorage reduction catalyst 12
The exhaust air-fuel ratio (A / F) N2 of the exhaust flowing into b is lean
And the first exhaust air-fuel ratio state_XStorage reduction catalyst
The exhaust air-fuel ratio (A / F) N1 of the exhaust flowing into the
And NO_XExhaust flowing into the storage reduction catalyst 12b
The exhaust air-fuel ratio (A / F) N2 of the air is enriched in the second
The exhaust air-fuel ratio state is alternately and repeatedly performed. First exhaust
NO in the air-fuel ratio state_XIn the storage reduction catalyst 12a,
NO stored_XIs released, and this released
NO_XAnd NO in the inflowing exhaust_XTo NH_ThreeIs generated
Is done. This NH_ThreeThen NO_xSelective reduction catalyst 10a
Flows into. On the other hand, NO_XStorage reduction catalyst 12b
Then, NO_XIs occluded. In the second exhaust air-fuel ratio state, N
O_XNO in the exhaust gas flowing into the storage reduction catalyst 12a_XBut
Occluded. On the other hand, NO_XStorage reduction catalyst 12b
Then, the NO that is occluded_XIs released and this release
NO_XAnd NO in the inflowing exhaust_XTo NH_ThreeBut
Generated. This NH_ThreeThen NO_xSelective reduction catalyst 1
0a. Therefore, the first and second exhaust gas
By alternately repeating the air-fuel ratio state, the first air
NO from cylinder group 1a_xNH is always supplied to the selective reduction catalyst 10a._ThreeTo
Can be supplied. On the other hand, NO_xSelective reduction catalyst 10
In a, the third cylinder # 3 and the fourth cylinder constituting the second cylinder group
NO discharged from cylinder # 4_XIs flowing. NO_x
The exhaust air-fuel ratio of the entire exhaust gas flowing into the selective reduction catalyst 10a is:
It is maintained lean, so that the second cylinder group 1b
NO discharged from_XIs NO_xSmell in selective reduction catalyst 10a
Thus, NH constantly supplied from the first cylinder group 1a_ThreeBy
Is purified. Therefore, NO _XIs released into the atmosphere
Is prevented. By the way, NO_XStorage reduction catalyst 12a, 1
Exhaust air-fuel ratio of exhaust flowing into 2b changes from lean to rich
NO when switched_XRatio from the storage reduction catalysts 12a and 12b
Relatively large amount of NO_XIs released and this relatively large amount of NO_X
To NH_ThreeIs generated. Therefore, NO_XTemporarily
NO stored in_XProvide a storage reduction catalyst, NH_ThreeShould generate
NO when_XRelatively large amount of NO from storage reduction catalyst_XTo
Release this much NO_XTo NH_ThreeGenerate the ratio
Relatively large amount of NH_ThreeNO_xSupply to selective reduction catalyst 10a
Can be done. As a result, NO_xSelective reduction
NO flowing into the catalyst 10a_XNH required to purify water
_ThreeNO for the quantity_xFlows into the selective reduction catalyst 10a
NH_ThreeInsufficient quantity is prevented, thus NO_XTo
It can be purified well. In the diesel engine shown in FIG._xSelection
NH flowing into selective reduction catalyst 10a_ThreeIf the quantity is NO_xReturn
NO flowing into source catalyst 10a_XNecessary to purify the quantity
NH _ThreeSame as amount or required NH_ThreeMore than the amount
I'm trying. NO_xExcess in the selective reduction catalyst 10a
NH became_ThreeIs NO_xAdsorbed on the selective reduction catalyst 10a
As a result, NH_ThreeIs prevented from being released into the atmosphere
ing. As described above, NO_xSelective reduction catalyst 1
NH adsorbed on Oa_ThreeIs NO_xSelective reduction catalyst 10
NH flowing into a_ThreeWhen the amount decreases or NO_xReturn
NO in the source catalyst 10a_XNO when inflow_xSelective reduction catalyst
Released from 10a. Therefore, NO _xSelective touch
Medium 10a is NH_ThreeIs also prevented from saturating. As described above, the lean operation is performed in each cylinder.
The first and second sub-cylinder groups 1aa and 1ab
The exhaust air-fuel ratio of the exhaust discharged from the engine is lean,
Therefore, the exhaust of the sub-cylinder groups 1aa and 1ab is set to NO.
_XIf the storage reduction catalysts 12a and 12b are directly guided, NO_X
Exhaust air-fuel of exhaust flowing into the storage reduction catalysts 12a, 12b
The ratio becomes lean. So, NO_XStorage reduction catalyst 12
a, make the exhaust air-fuel ratio of the exhaust gas flowing into 12b rich
NO_XUpstream of the storage reduction catalysts 12a and 12b
Secondary supply of reducing agent into the exhaust branch pipe 8 or the cylinder
Like that. That is, in the diesel engine shown in FIG.
To make the exhaust air-fuel ratio of the exhaust gas to be rich_XOcclusion reduction
In the cylinder corresponding to the catalyst, the fuel injection valve 7
Fuel is secondary injected in addition to the normal injection. like this
Such a secondary fuel injection is called a secondary injection.
It is performed in the latter half of the expansion stroke or in the exhaust stroke. This secondary injection
Fuel in exhaust or NO_XThe storage reduction catalyst 12a,
NO by reacting with oxygen on the 12b surface_XOcclusion return
The oxygen concentration in the source catalysts 12a and 12b decreases and NO
_XNO stored from the storage reduction catalysts 12a and 12b
_XIs released. Therefore, NO_XStorage reduction catalyst 12
good NO from a, 12b_X2 to ensure release action
To ensure a good reaction between fuel and oxygen by the next injection
In the second half of the expansion stroke, where the exhaust gas temperature is relatively high, secondary injection is performed.
Is preferred. The fuel from the secondary injection is engine output
Does not contribute to The fuel injection amount AF in the secondary injection is, for example,
If NO_XThe exhaust air-fuel ratio of exhaust flowing into the storage reduction catalyst is about
It is determined to be 13.8. As a result, secondary fuel
A large amount of NH while keeping the injection amount AF small_ThreeGenerate
be able to. Note that this secondary fuel injection amount AF is
Between the depression amount DEP of the engine pedal 31 and the engine speed N.
In the form of a map shown in FIG.
It is remembered. NO_XFlow into storage reduction catalysts 12a and 12b
Reducing agent to make the exhaust air-fuel ratio of the exhaust
Gasoline, isooctane, hexane, hepta
Hydrocarbons such as gas, light oil, kerosene, or liquid
Uses hydrocarbons such as butane and propane that can be stored
be able to. However, in the diesel engine of FIG.
In the first or second sub-cylinder group 1aa, 1bb
By performing the secondary injection with the fuel injection valve 7,
NO_XThe exhaust air-fuel ratio of the exhaust flowing into the storage reduction catalyst
And therefore additional injection for reductant supply
No valves or additional reductant tanks are required. Further, NO_XExhaust gas flowing into the storage reduction catalyst
When the exhaust air-fuel ratio of the
Intake throttle valves 14a, 14 arranged in the intake branch pipes 2 of the group
The opening degree of b is reduced, that is, the intermediate opening degree between full opening and full closing
As a result, the engine air-fuel ratio of the corresponding
Slightly leaner than theoretical air-fuel ratio (A / F) S
Like that. By doing so, the secondary fuel injection amount A
F can be reduced. Intake throttle valve 1 in this case
The intermediate opening MID of 4, 14b is equal to the depression of the accelerator pedal 31.
FIG. 4 shows a function of the set amount DEP and the engine speed N.
It is stored in the ROM 22 in advance in the form of a map shown. On the other hand, NO_XThe storage reduction catalyst 12a,
The exhaust air-fuel ratio of the exhaust flowing into 12b should be lean
The secondary injection in the corresponding sub-cylinder groups 1aa and 1ab
Shooting is stopped, that is, only normal injection is performed. Next, exhaust
Control of the timing of changing the air-fuel ratio state will be described. Up
Between the above-described first exhaust air-fuel ratio state and the second exhaust air-fuel ratio state
May be performed at predetermined intervals, for example.
it can. However, in the diesel engine of FIG.
O_XNO stored in the storage reduction catalysts 12a and 12b
_XQuantity, that is, storage NO_XQuantity S1 (NO_X), S2 (N
O_X), And the exhaust air-fuel ratio of the inflowing exhaust gas is rich.
NO_XStorage reduction catalyst, that is, NO_XEmitting
NO_XStorage NO of storage reduction catalyst_XUnder the predetermined amount
Exhaust air-fuel ratio state when falling below the threshold LT
The change action is performed. This way,
NO_xMake sure the selective reduction catalyst 10a has NH_ThreeCan supply
Can be. FIG. 5 shows NO in the diesel engine of FIG.
_XStorage NO of storage reduction catalysts 12a and 12b_XQuantity S1 (N
O_X), S2 (NO_X), Rich flag RF, and N
O_XExhaust gas flowing into the storage reduction catalysts 12a and 12b
Time chart showing air-fuel ratio (A / F) N1 and (A / F) N2
It is a chart. The rich flag RF indicates the exhaust air-fuel ratio state.
It is set to 1 when the first exhaust air-fuel ratio state is to be set, and the second
This coefficient is set to 2 when the exhaust air-fuel ratio state is to be set.
In FIG. 5, the time zero indicates that the rich flag RF is 2.
Time. Referring to FIG.
When RF = 2, the second exhaust air-fuel ratio state is set.
You. That is, the secondary injection is performed in the second sub-cylinder group 1ab.
Is performed and the intake throttle valve 14b is set to the intermediate opening degree MID.
NO_XExhaust gas flowing into the storage reduction catalyst 12b
The exhaust air-fuel ratio (A / F) N2 of the
Secondary injection is stopped in the first sub-cylinder group 1aa and
NO when the throttle valve 14a is fully opened MAX_X
The exhaust air-fuel ratio of the exhaust gas flowing into the storage reduction catalyst 12a (A /
F) N1 is made lean. As a result, NO_XOcclusion reduction
NO from catalyst 12b_XIs released, so that S2 (NO_X)
Gradually decreases, and NO _XNO on the storage reduction catalyst 12a_XBut
S1 (NO_X) Gradually increases. Next, at time a, S2 (NO_X) <L
When it becomes T, the rich flag RF is set to 1. That is,
Storage NO_XNO released when the amount decreases_XSmall amount
And therefore NO_xSupplied to the selective reduction catalyst 10a.
NH_ThreeThe amount is reduced. Therefore, NO_XOcclusion reduction
Storage NO of catalyst 12b_XQuantity S2 (NO_X)
NO_XNH in the storage reduction catalyst 12b_ThreeRaw
Stop the action, NO _XNO from the storage reduction catalyst 12a_X
And release NH_ThreeIs generated. That
As a result, a relatively large amount of NH_ThreeContinuously NO_xSelective touch
It can be supplied to the medium 10a. When RF = 1, the first exhaust air-fuel ratio state
To be. That is, in the first sub-cylinder group 1aa, 2
The next injection is performed and the intake throttle valve 14a has the intermediate opening degree MID.
NO_XFlows into the storage reduction catalyst 12a
The exhaust air-fuel ratio (A / F) N1 of the exhaust
Sometimes, the secondary injection is stopped in the second sub-cylinder group 1ab
And the intake throttle valve 14b is fully opened MAX
NO_XExhaust air-fuel ratio of exhaust flowing into storage reduction catalyst 12b
(A / F) N2 is made lean. As a result, NO_XSucking
NO from the storage reduction catalyst 12a_XIs released, so that S1 (N
O_X) Gradually decreases and NO_XN is added to the storage reduction catalyst 12b.
O_XIs stored, so that S2 (NO_X) Gradually increases
You. Next, at time b, S1 (NO_X) <L
At T, the rich flag RF is set to 2 again. But
Accordingly, the first exhaust air-fuel ratio state is set again. Like this
The first and second exhaust air-fuel ratio states are alternately repeated.
Will be By the way, NO_XStorage reduction catalysts 12a, 12b
Occlusion NO_XQuantity S1 (NO_X), S2 (NO_X) Directly
It is difficult to ask. Therefore, in this embodiment, NO_X
NO flowing into the storage reduction catalysts 12a and 12b_XQuantity, sand
That is, the first or second sub-cylinder group 1aa, 1ab is discharged.
NO_XNO from quantity_XStorage reduction catalysts 12a, 12b
Occlusion NO_XQuantity S1 (NO_X), S2 (NO_X)
I am trying to do it. That is, the engine speed N becomes high.
The amount of emissions emitted from the engine per unit time
NO as the engine speed N increases_XSucking
Flows into the storage reduction catalysts 12a and 12b per unit time
Inflow NO_XThe amount increases. Also, as the engine load increases
That is, the depression amount DE of the accelerator pedal 31
The engine displacement increases as P increases.
The engine load is high because the combustion temperature is high.
The amount of depression of the accelerator pedal 31
As the DEP increases, emissions from the engine per unit time
NO issued_XThe amount increases. FIG. 6A shows one of the values obtained by the experiment.
NO emitted from the cylinders per unit time_XQuantity Q (NO
_X), The depression amount DEP of the accelerator pedal 31, the engine
FIG. 6A shows the relationship with the rotation speed N.
Curves are the same NO_XIndicates the amount. As shown in FIG.
Discharged from the cylinder per unit time_XQuantity Q
(NO_X) Indicates that the depression amount DEP of the accelerator pedal 31 is
The engine speed N increases as the engine speed increases.
Increase as the number increases. Note that NO shown in FIG._X
Quantity Q (NO_X) Is in the form of a map as shown in FIG.
It is stored in the ROM 22 in advance. That is, the exhaust air-fuel ratio of the inflowing exhaust gas is
NO_XStorage NO of storage reduction catalyst_XQuantity S (NO
_X) Is Q (NO_X). did
Therefore, the exhaust air-fuel ratio of the inflowing exhaust gas is lean NO
_XStorage NO of storage reduction catalyst_XQuantity S (NO_X) Is the following formula
Is done. S (NO_X) = S (NO_X) + Q (NO_X) ・ DLT Here, DLT is Q (NO_X) Represents the detection time interval
Q (NO _XDLT is the last processing route
NO between the routine and the current processing routine_XOcclusion reduction
NO stored in the catalyst_XIt represents the quantity. On the other hand, FIG.
NO per unit time_XStorage reduction catalysts 12a, 12b
NO released from_XQuantity D (NO_X)
You. In FIG. 7A, the solid line is NO_XStorage reduction catalyst 12
a and 12b indicate when the temperature is high, and the broken line indicates NO.
_XIt shows when the temperature of the storage reduction catalysts 12a and 12b is low.
ing. TIME indicates that the exhaust air-fuel ratio of
Indicate the time since the switch from lean to rich
I have. NO_XNO in storage reduction catalysts 12a and 12b
_XNO decomposition rate_XTemperature of storage reduction catalysts 12a and 12b
The higher the degree, the faster. Therefore, FIG.
NO as indicated by the solid line_XStorage reduction catalysts 12a, 12
b is high, that is, NO_XStorage reduction catalyst
Exhaust gas temperature TNC of the exhaust gas flowing into 12a, 12b is high
Sometimes NO_XExhaust air on the surface of the storage reduction catalyst 11a
While the fuel ratio does not become sufficiently rich, a large amount of NO_XIs NO
_XNO release from the storage reduction catalysts 12a and 12b_XSucking
Temperature of the storage reduction catalysts 12a and 12b, that is, the exhaust gas temperature T
When the NC is low, as shown by the broken line in FIG.
Small amount of NO_XIs NO_XFrom the storage reduction catalysts 12a and 12b
Released. In other words, the exhaust gas temperature TNC increases.
NO per unit time_XReleased from storage reduction catalyst 11a
NO_XQuantity D (NO_X) Increases. This NO_Xamount
D (NO_X) Is a function of the exhaust gas temperature TNC and the time TIME.
In the form of a map shown in FIG.
Is stored within. Note that NO_XStorage reduction catalyst 12
a, the temperature TNC of the exhaust gas flowing into the 12b is detected by the temperature sensor 2
8a and 28b. However, engine operation
The rotation state, that is, the depression amount DEP of the accelerator pedal 31
And the engine speed N. That is, the exhaust air-fuel ratio of the inflowing exhaust gas is
NO_XStorage NO of storage reduction catalyst_XQuantity S (NO
_X) Is D (NO_X) Only decrease. did
Therefore, the exhaust air-fuel ratio of the inflowing exhaust gas is rich NO
_XStorage NO of storage reduction catalyst_XQuantity S (NO_X) Is the following formula
Is done. S (NO_X) = S (NO_X) -D (NO_X) ・ DLT Here, DLT is D (NO_X) Represents the detection time interval
And therefore D (NO _XDLT is the last processing route
NO between the routine and the current processing routine_XOcclusion reduction
NO stored in the catalyst_XIt represents the quantity. FIG. 8 is a flowchart for executing the above-described exhaust air-fuel ratio control.
FIG. This routine is predefined
This is executed by an interrupt at each set time. Figure 8
For reference, first, at step 40, the rich flag RF is set.
It is determined whether it is 1 or not. When RF = 1,
(A / F) N1 is made rich and (A / F) N2 is made rich.
If it should be turned on, the process proceeds to step 41. Stay
In step 41, the release NO is determined from the map of FIG._XQuantity D
(NO_X) Is calculated. In the following step 42,
NO based on_XStorage NO of storage reduction catalyst 12a_XQuantity S1
(NO_X) Is calculated. S1 (NO_X) = S1 (NO_X) -D (N
O_X) ・ DLT1 Here, DLT1 is D (NO_X) Represents the detection time interval
And therefore D (NO_XDLT1 is the previous process
NO between routine and current processing routine _XOcclusion
NO released from reduction catalyst 12a_XIt represents the quantity.
In the following step 43, the inflow NO is determined from the map of FIG.
_XQuantity Q (NO_X) Is calculated. In the following step 44
NO based on the following equation_XStorage NO of storage reduction catalyst 12b_X
Quantity S2 (NO_X) Is calculated. S2 (NO_X) = S2 (NO_X) + Q (N
O_X) ・ DLT1 Here Q (NO_XDLT1 is the previous processing routine
NO until the current processing routine_XStorage reduction catalyst 1
NO stored in 2b_XIt represents the quantity. Next steps
NO at 45_XStorage NO of storage reduction catalyst 12a_XQuantity S1
(NO_X) Is smaller than the lower threshold LT.
Separated. S1 (NO_X) <LT if step 4
Proceeding to 6, the rich flag RF is set to 2. That is, S
1 (NO_XNO if <LT_XStorage reduction catalyst 12
NO released from a_XThe amount is small and therefore NO_xSelection
A sufficient amount of NH for the selective reduction catalyst 10a_ThreeCan supply
Judge not possible and NO_XNO of the storage reduction catalyst 12a_X
Release NH_ThreeStop generating action, NO_XStorage reduction catalyst 1
2b NO_XRelease NH_ThreeStart the generation action. to this
On the other hand, in step 45, S1 (NO_X) ≧ LT
NO_XNO released from the storage reduction catalyst 12a_X
Large amount, NO_xA sufficient amount of NH for the selective reduction catalyst 10a
_ThreeAnd the rich flag RF
Is maintained at 1. On the other hand, at step 40, the rich flag
When RF is not 1, that is, when RF = 2,
(A / F) N1 is made lean and (A / F) N2 is made
When it is determined that the switch should be made, the process proceeds to step 47. Stay
In step 47, the inflow NO is determined from the map of FIG._XQuantity Q
(NO_X) Is calculated. In the following step 48,
NO based on_XStorage NO of storage reduction catalyst 12a_XQuantity S1
(NO_X) Is calculated. S1 (NO_X) = S1 (NO_X) + Q (N
O_X) ・ DLT2 Here, DLT2 is Q (NO_X) Represents the detection time interval
And therefore Q (NO_XDLT2 is the previous process
NO between routine and current processing routine _XOcclusion
NO stored in the reduction catalyst 12a_XIt represents the quantity. Continued
In step 49, the release NO is determined from the map shown in FIG._X
Quantity D (NO_X) Is calculated. In the following step 50,
NO based on the formula_XStorage NO of storage reduction catalyst 12b_Xamount
S2 (NO_X) Is calculated. S2 (NO_X) = S2 (NO_X) -D (N
O_X) ・ DLT2 Here D (NO_X)-Is DLT2 the previous processing routine?
NO until the current processing routine_XStorage reduction catalyst 1
NO released from 2b_XIt represents the quantity. The next step
NO in step 51_XStorage NO of storage reduction catalyst 12b_XQuantity S
2 (NO_X) Is smaller than the lower threshold LT.
Is determined. S2 (NO_X) <LT when step
Proceeding to 52, the rich flag RF is set to 1. That is,
S2 (NO_XNO if <LT_XStorage reduction catalyst 1
2b NO_XNO based on _xThe selective reduction catalyst 10a
A reasonable amount of NH_ThreeN cannot be supplied
O_XNO of the storage reduction catalyst 12b_XRelease NH_ThreeGenerating action
Stop, NO_XNO of the storage reduction catalyst 12a_XRelease ・ N
H_ThreeStart the generation action. On the other hand, to step 51
S2 (NO_XNO if ≧ LT_XOcclusion reduction
NO of catalyst 12b_XNO based on_xSelective reduction catalyst 10
a sufficient amount of NH for a_ThreeJudge that we can supply
To maintain the rich flag RF at 2. FIG. 9 is for executing the above-described fuel injection control.
Shows the routine. This routine is predefined
This is executed by interruption every crank angle. FIG.
First, in step 60, the first cylinder # 1
That is, the normal injection timing of the first sub-cylinder group 1aa
Is determined. Normal injection timing of cylinder # 1
Then, the routine proceeds to step 61, where normal injection is performed.
Done. That is, fuel injection around the compression top dead center
Done. In the following step 62, the rich flag RF is set to 1
, That is, NO connected to the first cylinder # 1
_XThe exhaust air-fuel ratio of the exhaust gas flowing into the storage reduction catalyst 12a is reset.
It is determined whether it is time to switch. RF = 1
I.e. NO_XExhaust flowing into storage reduction catalyst 12a
Next, when the exhaust air-fuel ratio of the
Proceeding to 63, the secondary injection is performed. That is, after the expansion stroke
A second fuel injection is performed in a half or exhaust stroke. Next
Ends the processing cycle. Step 62
When RF ≠ 1, then the processing cycle is terminated
I do. That is, in this case, in the first cylinder # 1, the normal injection
Is done. On the other hand, in step 60, the first cylinder # 1
If it is not the normal injection timing, then step 6
And proceeds to No. 4 cylinder # 2, that is, the second sub-cylinder group 1ab
It is determined whether it is the normal injection timing. No. 2
At the time of the normal injection timing of cylinder # 2,
Proceeding to step 65, normal injection is performed. Next step 66
Then, whether the rich flag RF is 2 or not, that is,
NO connected to cylinder # 2_XFlow into storage reduction catalyst 12b
Whether it is time to make the exhaust air-fuel ratio of the exhaust
Separated. When RF = 2, that is, NO_XOcclusion reduction
The exhaust air-fuel ratio of the exhaust flowing into the medium 12b should be rich
Sometimes, then, the routine proceeds to step 67, where the secondary injection is performed.
You. Next, the processing cycle ends. In contrast,
When RF # 2 in step 66, the next processing cycle
End That is, in this case, the communication is not performed in the second cylinder # 2.
Only normal injection is performed. On the other hand, in step 64, the second cylinder # 2
If it is not the normal injection timing, then step 6
8. Go to No. 8 to check if it is normal injection timing of cylinder # 3
It is determined whether or not it is. Normal injection timing of cylinder # 3
Then, the routine proceeds to step 69, where normal injection is performed.
It is. Next, the processing cycle ends. In contrast,
Normal injection timing of the third cylinder # 3 at step 68
If not, then proceed to step 70, No. 4 cylinder #
At 4, normal injection is performed. Then the processing cycle
finish. Therefore, in the second cylinder group 1b, the secondary injection
Is not done. FIG. 10 shows the execution of the above-described intake throttle valve control.
2 shows a routine for performing the following. This routine is predetermined
It is executed by an interrupt every set time. FIG.
Referring to FIG. 0, first, at step 80, the rich flag
It is determined whether RF is 1 or not. When RF = 1,
That is, NO connected to the first cylinder # 1_XStorage reduction catalyst
(A / F) N1 of 12a is made rich and the second cylinder # 2
NO connected to_X(A / F) N of the storage reduction catalyst 12b
If 2 should be made lean, then go to step 81.
Only slightly lean engine air-fuel ratio of cylinder # 1
The intermediate opening MID of the intake throttle valve that is most suitable for
It is calculated from the top. In the following step 82, the first cylinder
The opening degree V1 of the intake throttle valve 14a in the # 1 intake branch pipe 2 is
MID. In the following step 83, the second cylinder #
2, the opening degree V2 of the intake throttle valve 14b in the intake branch pipe 2 is maximum.
The opening degree MAX is set. Next, the processing cycle ends. When RF８０1 in step 80,
That is, when RF = 2, that is, when connected to the first cylinder # 1.
NO_X(A / F) N1 of the storage reduction catalyst 12a is
Connected to the second cylinder # 2_XOcclusion reduction
When (A / F) N2 of the medium 12b should be made rich,
Proceeding to step 84, the inside of the intake branch pipe 2 of the first cylinder # 1
The opening degree V1 of the intake throttle valve 14a is set to the maximum opening degree MAX.
You. In the following step 85, the engine air-fuel ratio of the second cylinder # 2
The best intake throttle valve to make the engine slightly lean
The opening MID is calculated from the map shown in FIG. The next step
At 86, the intake throttle in the intake branch pipe 2 of the second cylinder # 2
The opening degree V2 of the valve 14b is defined as the MID. Then processing
End the cycle. In the above embodiment, the present invention is applied to a diesel engine.
Applied to Seki. However, the present invention relates to spark ignition type gas.
It can also be applied to sorin engines. In this case, the first
By making the engine air-fuel ratio of the cylinders of the cylinder group 1a rich,
Even NO_XExhaust flowing into the storage reduction catalysts 12a, 12b
The exhaust air-fuel ratio of the air can be made rich. Also on
NO in the described embodiment_XBy using an occlusion reduction catalyst
Storage material and NH_ThreeAnd the catalyst to be formed at the same time.
ing. However, the storage material and NH _ThreeSeparate from generated catalyst
NH formed individually_ThreeGenerated catalyst in the exhaust passage downstream of the storage material
May be arranged. In this case, NH_ThreeGeneration touch
For example, a three-way catalyst can be used as the medium. [0056] Effect of the Invention NO_XCan be satisfactorily purified.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an overall view of an internal combustion engine. FIG. 2 is a diagram showing the NH ₃ conversion efficiency of a NO _X storage reduction catalyst. FIG. 3 is a diagram showing a secondary fuel injection amount. FIG. 4 is a diagram showing an intermediate opening degree of an intake throttle valve. [5] occluded amount of NO _X in _the NO _X storage reduction catalyst, is a time chart showing an exhaust gas air-fuel ratio of the exhaust gas flowing into the rich flag and _the NO _X storage reduction catalyst. FIG. 6 is a graph showing the amount of NO _X discharged from a cylinder per unit time. FIG. 7 is a graph showing the amount of NO _X released from the NO _X storage reduction catalyst per unit time. FIG. 8 is a flowchart for executing exhaust air-fuel ratio control. FIG. 9 is a flowchart for executing fuel injection control. FIG. 10 is a flowchart for executing opening degree control of an intake throttle valve. [Description of Signs] 1a 1st cylinder group 1aa 1st sub cylinder group 1ab 2nd sub cylinder group 1b 2nd cylinder group 2 intake branch pipe 7 fuel injection valve 8 exhaust branch pipe 10 ... exhaust gas purifying catalyst 10a ... NO _x selective reduction catalyst 12a due to NH _3, 12b ... NO _X occluding and reducing catalyst 14a, 14b ... intake throttle valve

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification code FI F01N 3/28 301 F01N 3/28 301A 301C ZAB ZAB F02D 41/04 305 F02D 41/04 305A ZAB ZAB 43/00 301 43/00 301E 301T (72) Inventor Toshiaki Tanaka 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation (56) References JP-A-9-4414 (JP, A) JP-A-4-365920 (JP, A) JP-A-6-272545 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) F01N 3/08-3/28 F02D 41/04 F02D 43/00

Claims (1)

(57) [Claims 1] A multi-cylinder internal combustion engine is divided into a first cylinder group and a second cylinder group, and N1 in the exhaust of the first cylinder group.
In the exhaust gas purifying apparatus for an internal combustion engine configured to generate NH ₃ from O _X and purify NO _{X in} the exhaust of the second cylinder group by the NH ₃ , the first cylinder group includes at least two sub-cylinder groups. NH ₃ generation for generating NH ₃ from NO _X in the inflowing exhaust gas when the exhaust air-fuel ratio of the inflowing exhaust gas is rich in each sub-exhaust passage connected to each sub-cylinder group NO _X in which the catalyst, the exhaust gas air-fuel ratio of the inflowing exhaust gas is occluded NO _X in the inflowing exhaust gas when the lean exhaust air-fuel ratio of the exhaust gas flowing is occluded becomes rich
The NH ₃ generation catalyst is disposed in the corresponding auxiliary exhaust passage downstream of the storage material or in the storage material, and each of the NH ₃ generation catalysts is disposed in the corresponding auxiliary exhaust passage downstream of the NH ₃ generation catalyst. An exhaust purification catalyst for purifying NO _X and NH ₃ in the inflowing exhaust gas is disposed in a merged exhaust passage that merges with a second exhaust passage connected to the second cylinder group. Exhaust air-fuel ratio control means for enriching or leaning the exhaust air-fuel ratio of the exhaust gas flowing into the corresponding storage material is disposed in the exhaust passage or the sub-cylinder group, respectively, and at least the second cylinder group performs a lean operation. Align, NH both the downstream absorbent storehouse material to release NO _X that is occluded from the intake storehouse material by the exhaust air-fuel ratio rich of the exhaust gas flowing by controlling the exhaust gas air-fuel ratio control means to a portion of the occlusion material ₃ and NH ₃ in the product catalyst Form, thereby supplying NH ₃ to the exhaust purification catalyst, to occlude NO _X in absorbent storehouse material by the exhaust gas air-fuel ratio of the exhaust gas flowing into the rest of the storage material in a lean exhaust air-fuel ratio of the exhaust gas flowing into An exhaust gas purifying apparatus in which NH ₃ is constantly supplied to an exhaust gas purifying catalyst by sequentially changing the storage material in which the gas is rich.