JP3342200B2 - 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 an exhaust gas purifying apparatus for an internal combustion engine.

[0002]

Absorbs NO _x when the air-fuel ratio is lean of the Related Art inflowing exhaust gas, arranged catalyst discharged into the engine exhaust passage an NO _x absorbed and supplying a reducing agent into the exhaust gas flowing An exhaust control valve is disposed in the engine exhaust passage upstream of the catalyst, and a reducing agent supply device for supplying a reducing agent to the catalyst downstream of the exhaust control valve is provided. Usually, the exhaust control valve is opened. N contained in the exhaust gas
The O _x absorbed in the catalyst, as in when releasing the NO _x from the catalyst to reduce NO _x to the reducing agent was released with the release of NO _x from the catalyst is supplied to the catalyst along with closing the exhaust control valve A known diesel engine is known (see JP-A-62-106826).

[0003]

[SUMMARY OF THE INVENTION However NO _x in the NO _x absorbed in the catalyst is assumed to be released into the atmosphere, thus in addition to the release of NO _x from the catalyst in the atmosphere in this diesel engine It is an essential requirement that a reducing agent be supplied so that it is not released as it is.

[0004] The present invention is not premised on such conventional thinking was to almost all NO _x contained in the exhaust gas based on the novel idea that recycled to the combustion chamber for purifying the exhaust gas exhaust It is to provide a purification device.

[0005]

SUMMARY OF THE INVENTION That is, according to a first aspect of the invention, in an internal combustion engine rich Do mixture is burned in at least some combustion chamber region, NO _x contained in the exhaust gas and NO _x trapping means for trapping, NO _x and _the NO _x releasing means allowed to release the captured NO _x by trapping means, NO _x recirculating means allowed to recirculate NO _x released from the NO _x trapping means in the combustion chamber And N
The O _x recirculation means is provided in the combustion chamber where an rich mixture is formed.
The recirculated gas containing NO _x is blown out toward the area
It is sea urchin.

According to the second invention, at least a part of the fuel
When the rich mixture is burned in the firing chamber
In combustion engine, to capture the NO _x contained in the exhaust gas
And NO _x trapping means that, captured by NO _x trapping means
And NO _x emission means allowed to release the NO _x, NO _x capture hand
N which allowed to recirculate NO _x released from the stage into the combustion chamber
The amount of soot comprising the O _x recirculating means, for generating in the combustion chamber
Amount of NO _x is caused to recycle the combustion chamber as but increased
Is to be increased.

According to the third invention, at least a part of the fuel
When the rich mixture is burned in the firing chamber
In combustion engine, to capture the NO _x contained in the exhaust gas
And NO _x trapping means that raises the temperature of the NO _x trapping means
NO _x trapped by the NO _x trapping means by Rukoto
And _the NO _x releasing means allowed to emit, from the NO _x trapping means
NO _x again allowed to recirculate released NO _x in the combustion chamber
Circulation means.

According to the fourth invention, at least a part of the fuel
When the rich mixture is burned in the firing chamber
In combustion engine, to capture the NO _x contained in the exhaust gas
And NO _x trapping means that, captured by NO _x trapping means
And NO _x emission means allowed to release the NO _x, NO _x capture hand
N which allowed to recirculate NO _x released from the stage into the combustion chamber
; And a O _x recirculating means, NO _x trapping means NO _x absorption
From particulate filter coated with absorbent
Becomes, NO _x releasing means capturing the particulate filter
By burning the captured particulates
To release the NO _x absorbed in _the NO _x absorbent Te
I'm trying.

[0009]

FIG. 1 shows a case where the present invention is applied to a diesel engine. Referring to FIG. 1, reference numeral 1 denotes an engine body, 2
Is a piston, 3 is a main chamber, 4 is a sub chamber, 5 is a nozzle of the sub chamber 4,
Reference numeral 6 denotes a fuel injection valve for injecting fuel into the sub-chamber 4, reference numeral 7 denotes an exhaust valve, and reference numeral 8 denotes an exhaust port. An intake port (not shown) is connected to the corresponding branch pipe 9 and surge tank 1.
0 is connected to the air cleaner 11. On the other hand, the exhaust port 8 is connected to an exhaust pipe 14 via an exhaust manifold 12 and an exhaust pipe 13.
And a first exhaust passage 16a and a second exhaust passage 16b branched at. An exhaust gas discharged from the engine is supplied to the first exhaust passage 16a or the second exhaust passage 1 in the branch portion 15.
6b is provided with a flow path switching valve 17 for mainly flowing into one of the flow paths 6b. The passage switching valve 17 is controlled by an actuator 18.

A first casing 17a is arranged in the first exhaust passage 16a, and a first heater 18a is arranged on the upstream side and a first particulate filter 19a is arranged on the downstream side in the first casing 17a. Similarly, a second casing 17b is disposed in the second exhaust passage 16b, and a second heater 18b is provided upstream in the second casing 17b.
However, a second particulate filter 19b is disposed downstream. The first heater 18a and the second heater 18b are connected to a power supply via the corresponding relays 20a and 20b, respectively. The first exhaust passage 16a and the second exhaust passage 16b are provided with particulate filters 19a, 19b.
Are joined to each other downstream of the
The outlet of the first exhaust passage 16a or the second exhaust passage 16b
Selectively closed chain possible flow path switching valve 22 to the outlet portion of the are arranged. The flow path switching valve 22 is controlled by an actuator 23.

The first exhaust passage 16 upstream of the first heater 18a
a is provided with a first secondary air supply port 24a,
In the second exhaust passage 16b upstream of the second heater 18b, the second
Of the secondary air supply port 24b is disposed. These first
The secondary air supply port 24a and the second secondary air supply port 24b are connected to an air pump 26 via a first air valve 25a and a second air valve 25b, respectively. On the other hand, the first exhaust passage 16a downstream of the first particulate filter 19a is connected to the first exhaust circulation valve 27a and the exhaust recirculation passage 2a.
The second exhaust passage 16b downstream of the second particulate filter 19b is connected to the surge tank 10 via a second exhaust circulation valve 27b and an exhaust recirculation passage 28.

The electronic control unit 30 is composed of a digital computer, and a ROM (read only memory) 32, a RAM (random access memory) 33, a CPU (microprocessor) 34, and an input port 35 interconnected by a bidirectional bus 31. And an output port 36. As shown in FIG. 1, a load sensor 38 that generates an output voltage proportional to the amount of depression of an accelerator pedal 37 is provided, and the output voltage of the load sensor 38 is input to an input port 35 via an AD converter 39. . Further, the input port 35 is connected to a rotation speed sensor 40 for generating an output pulse representing the engine rotation speed. On the other hand, the output port 36
Are the actuators 1 via the corresponding drive circuits 41, respectively.
8, 23, relays 20a, 20b, air valves 25a, 25
b, connected to the exhaust circulation valves 27a, 27b.

Each of the particulate filters 19a, 19
b is made of, for example, a monolithic cordierite having a honeycomb structure, and the particulate filters 19a and 19b function to capture particulates contained in exhaust gas, that is, soot. Furthermore, this particulate filter 1
9a, is on 19b NO _x absorbent capable of absorbing the NO _x in the exhaust gas discharge is coated. This _the NO _x absorbent to, for example alumina as a carrier, an alkaline earth such as the carrier on, for example, potassium K, sodium Na, cesium Cs, barium Ba, calcium Ca, lanthanum La, as yttrium Y And at least one selected from rare earths and a noble metal such as platinum Pt.

[0014] The _the NO _x absorbent absorbs NO _x in the exhaust gas when there is an excess of oxygen in the temperature is relatively low and the exhaust gas of the NO _x absorbent, the temperature of the NO _x absorbent is increased the absorbed NO _x forms an absorbing and releasing action of the NO _x to be emitted. Although the detailed mechanism of the absorption / release action of the NO _x absorbent is not clear, it is considered that the absorption / release action is performed by the mechanism shown in FIG. In the following, this mechanism will be described by taking as an example a 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, when the temperature of the NO _x absorbent is relatively low and excessive oxygen is present in the exhaust gas, as shown in FIG. 2, these oxygens O ₂ are converted to platinum Pt in the form of O ₂ ⁻ or O ^2−.
Adheres to the surface of On the other hand, NO in the exhaust gas is platinum Pt.
O ₂ on the surface of the ^- or O ^2- and reacts, becomes NO ₂ (2
NO + O ₂ → 2NO ₂ ). Then part of the generated NO ₂ is platinum Pt on nitrate ions NO as shown in FIG. 2 while being absorbed into the absorbent while being oxidized bonding with the barium oxide BaO by ₃ ^- in the form of absorbent Spread. In this way, NO _x is absorbed in the NO _x absorbent. In contrast _the NO _x absorbent nitrate ions NO ₃ are diffused into the temperature increases in _the NO _x absorbent of ^- decomposes, resulting NO _x absorbed in the absorbent in which it is NO _x is absorption _of NO _x Released from the drug.

[0016] In diesel engines, combustion is usually carried out under excess air, so that excess oxygen is present in the exhaust gas at this time. Therefore, at this time, the particulates contained in the exhaust gas are converted into the particulate filter 1.
9a and 19b, and at the same time NO in the exhaust gas
_x will be absorbed by the NO _x absorbent. On the other hand, when a large amount of particulates is captured by the particulate filters 19a and 19b, the particulates must be removed. For this purpose, in the embodiment according to the present invention, the flow path of the exhaust gas is periodically switched by the flow path switching valve 17.

That is, in the embodiment according to the present invention, the first exhaust passage 16a is provided by the flow path switching valve 17 as shown in FIG.
Is closed, and the outlet of the first exhaust passage 16a is closed by the flow path switching valve 22, so that the first exhaust passage 16a is closed.
Is closed, the inlet and outlet of the second exhaust passage 16b are opened, and the second exhaust passage 16b is in an open state through which exhaust gas can flow. On the other hand, when the inlet of the second exhaust passage 16b is closed by the passage switching valve 17 and the outlet of the second exhaust passage 16b is closed by the passage switching valve 22, the second exhaust passage 16b is closed. The inlet and outlet of the first exhaust passage 16a are opened, and the first exhaust passage 16a is in an open state through which exhaust gas can flow.

As can be seen from FIG. 3, the second exhaust passage 16b
Is opened, the first exhaust passage 16a is closed.
At this time, the exhaust gas flows into the second casing 17b.
You. At this time, the exhaust gas flowing into the second casing 17b is
The particulates contained in the powder are the second particulate
Filter 19b and contained in this exhaust gas.
NO_xIs applied to the second particulate filter 19b.
NO coated _xAbsorbed by absorbent.

On the other hand, when the first exhaust passage 16a is closed, as shown in FIG. 3, the first heater 18a is turned on, and the first air valve 25a is opened. as a result,
The first heater 18a generates heat, and secondary air is supplied from the first secondary air supply port 24a. When the first heater 18a generates heat and the supply of the secondary air is started, first the first heater 18a generates the first air.
The particulates captured at the upstream end of the particulate filter 19a burn, and then the downstream particulates are sequentially burned. When the particulate combustion is started, the first particulate filter 1
9a temperature increases, the resulting NO _x absorbed in the absorbent which do the NO _x is released. Therefore, CO ₂ , NO _x and a small amount of H are output from the first particulate filter 19a.
C, N ₂ , O _{2 and the} like are discharged. On the other hand, as shown in FIG. 3, while the first exhaust passage 16a is in the closed state, the first exhaust circulation valve 27a is opened, and therefore, the CO exhausted from the first particulate filter 19a.
₂ , NO _x and a small amount of HC, N ₂ , O _2, etc. are supplied into the surge tank 10 through the exhaust gas recirculation passage 28 and then sent into the main chamber 3 and the sub chamber 4.

The total particulate matter that has been captured by the first particulate filter 19a is burned, when the total NO _x which had been absorbed in _the NO _x absorbent is time released the first exhaust passage 16a is an open state And the second
The exhaust passage 16b is closed. First exhaust passage 16a
There particulates contained as in the exhaust gas is in the open state is captured by the first particulate filter 19a, the _the NO _x absorbent NO _x is coated to the first particulate filter 19a in the exhaust gas Absorbed.

On the other hand, when the second exhaust passage 16b is closed, the second exhaust circulation valve 27b is opened as shown in FIG. Further, the second heater 18b is turned on, and the second heater 18b is turned on.
The air valve 25b is opened and secondary air is supplied from the second secondary air supply port 24b. Thus to particulates are captured by the second particulate filter 19b is burned, from _the NO _x absorbent which is coated on the second particulate filter 19b NO _x is released, the second particulate filter CO ₂ , NO _x and a small amount of HC, N ₂ , O _2, etc. discharged from 19b are supplied to the surge tank 10 via the exhaust gas recirculation passage 28.

[0022] NO _x in the exhaust gas in this embodiment of the present invention as described above is absorbed in _the NO _x absorbent, i.e. NO _x trapped by the absorbent, NO released from _the NO _x absorbent
_{Since x} is sent into the main chamber 3 and the sub-chamber 4 again, NO _x is not released into the atmosphere at all. At least a portion of the NO _x sent into the main chamber 3 and the sub chamber 4 is reduced during combustion. It is necessary to understand the soot generation mechanism in order to understand the NO _x reduction action. Therefore, first, the soot generation mechanism will be described with reference to FIG.

FIG. 4A shows the state of fuel molecules contained in light oil. At this time, the molecular weight of the fuel molecule is approximately 200. At this time, the fuel molecule has a shape in which carbon atoms are connected in a chain as shown in FIG. Next, when the combustion is started, the fuel molecules are changed to (2) in FIG.
It becomes an annular structure to C ₁₂ C ₆ as shown in, then become spherical cluster A of C ₆₀ or C ₇₂ as shown in (3) in FIG. This cluster A is formed of a combination of a cyclic structure composed of six carbon atoms and a cyclic structure composed of five carbon atoms, as shown in FIG.

Next, when the time further elapses, (4) in FIG.
As shown by B, a partially spherical structure formed from a combination of a cyclic structure composed of 6 carbon atoms and a cyclic structure composed of 5 carbon atoms is generated. Are sequentially stacked around the cluster A. The particles thus generated continue to grow, and eventually have a particle size of about 3 nm.

Next, a plurality of these particles are gathered together as shown in FIG.
An aggregate of particles as shown in (5) is formed. The aggregate of the particles is called an inner shell. As described above, each particle constituting the inner shell has a strong activity because it is surrounded by the unstable structure B consisting of five carbon atoms, and thus the inner shell has a strong activity. . Then, after a further elapse of time, stable graphite is generated, and these graphites C are sequentially stacked around the inner shell as shown in FIG. In this way, the inner shell and the particles of graphite C surrounding the inner shell continue to grow,
The particle size of these particles is finally about 30 nm. Thus, at this stage, the particles comprise an inner shell and a layer of graphite C surrounding the inner shell, and this layer of graphite C is referred to as the outer shell. Graphite C is stable and has little activity, so the outer shell will have little activity.

Next, as shown in FIG. 4 (6), particles composed of the inner shell and the outer shell surrounding the inner shell are connected in a chain as shown in FIG. 4 (7). Such a group of particles connected in a chain is generally called soot. When soot is generated when the fuel is burned, the soot is always formed by the inner shell and the outer shell. That is, regarding the soot generation process, an inner shell having strong activity is first formed, and then an inert outer shell is formed around the inner shell. In this case, when an inner shell having a strong activity is formed, if there is sufficient oxygen around the inner shell, the inner shell is instantaneously oxidized. On the other hand, when the inner shell is formed, there is not enough oxygen around the inner shell, and instead, NO _x
In the presence of such an oxide, the inner shell deprives NO _x of oxygen and burns it, while NO _x is reduced to N ₂ .

That is, if a rich mixture is formed in the combustion chamber even if it is localized, an inner shell is formed. In the rich mixture, oxygen is insufficient, so the rich mixture is formed. If NO _x is present, this NO _x will be reduced by the inner shell. However when such a fuel injection to the auxiliary chamber 4 as shown in FIG. 1 in the sub-chamber 4 are rich Do mixture is formed, thus NO _x released from the absorbent the NO _x Is recirculated into the main chamber 3 and the sub-chamber 4, this NO _x is mainly reduced in the sub-chamber 4.

The amount of NO _x discharged from the engine increases, and accordingly, the NO _x recirculated into the main chamber 3 and the sub-chamber 4
When the amount is increased amount of NO _x is reduced in the auxiliary chamber 4 is increased. Therefore never concentration of NO _x becomes higher by recycling the NO _x, concentration of NO _x will be attached fallen in certain equilibrium value. As described above, in order to reduce NO _x using the strong activity of the inner shell, it is necessary to form at least a locally rich mixture region in the combustion chamber. Therefore, the internal combustion engine may be a direct injection type internal combustion engine having no sub-chamber as long as a rich mixture region can be formed in the combustion chamber.

FIGS. 5 and 6 show an exhaust gas purification control routine, which is executed by interruption every predetermined time. Referring to FIGS. 5 and 6, first, at step 50, the count value T is incremented by one. Next, at step 51, the first exhaust passage 16
It is determined whether or not a flag F indicating that a should be closed is set. If the flag F is set, the routine proceeds to step 52, where the inlet of the first exhaust passage 16a is closed by the passage switching valve 17 and the outlet of the first exhaust passage 16a is closed by the passage switching valve 22. And
The inlet and outlet of the second exhaust passage 16b are opened. Next, at step 53, the first exhaust circulation valve 27a is opened, and the second exhaust circulation valve 27b is closed.

[0030] Then whether or not the count value T at step 54 exceeds the set value T ₁ is is determined. When the T ≦ T ₁ is the first heater 18a is turned on by turning on the relay 20a proceeds to step 55, then the first air valve 25a is made to open at step 56.
Next, the routine proceeds to step 59. On the other hand, the first heater 18a proceeds to step 57 becomes to T> T ₁ is turned off, then the first air valve 25a is made to closed at step 58. Next, the routine proceeds to step 59. In step 59, it is determined whether or not the count value T has exceeded a set value T ₂ (> T ₁ ). When T ≧ T ₂ , the routine proceeds to step 60, where the flag F is reset. Then, at step 61, the count value T is set to zero.

When the flag F is reset, in the next processing cycle, the process proceeds from step 51 to step 62 in which the inlet of the second exhaust passage 16b is closed by the passage switching valve 17 and the second passage is opened by the passage switching valve 22. The outlet of the exhaust passage 16b is closed, and the inlet and outlet of the first exhaust passage 16a are opened. Next, at step 63, the first exhaust circulation valve 27a is closed, and the second exhaust circulation valve 27b is opened.

[0032] Then whether or not the count value T at step 64 exceeds the set value T ₁ is is determined. When the T ≦ T ₁ is the second heater 18b is turned on by turning on the relay 20b proceeds to step 65, then the second air valve 25b is made to open at step 66.
Next, the routine proceeds to step 69. On the other hand, the second heater 18b proceeds to step 67 becomes to T> T ₁ is turned off, then the second air valve 25b is made to closed at step 68. Next, the routine proceeds to step 69. Whether step 69 the count value T has exceeded the set value T ₂ is determined. When T ≧ T ₂ , the routine proceeds to step 70, where the flag F is set.
Is set to zero.

FIG. 7 shows another embodiment. 7, the same components as those in FIG. 1 are denoted by the same reference numerals. Referring to FIG. 7, in this embodiment, a recirculation gas storage tank 80 for storing a recirculation gas containing NO _x is provided, and the recirculation gas storage tank 80 is provided with an exhaust gas recirculation passage 2.
8 is connected. A pressurizing pump 81 that is constantly driven during operation of the engine is disposed in the exhaust gas recirculation passage 28, and the recirculating gas containing NO _x discharged alternately from the particulate filters 19 a and 19 b is supplied by the pressurizing pump 81. Pressurized and sent into the recirculated gas storage tank 80. Thus the recycle gas storage tank 80 will be filled with high pressure recycle gas containing NO _x.

On the other hand, the recirculated gas storage tank 80 is connected to the recirculated gas supply passage 82 and the recirculated gas supply device 8.
On the other hand, it is connected to the surge tank 10 via a safety valve 84 which opens when the pressure in the recirculating gas storage tank 80 becomes abnormally high.
The recirculation gas supply device 83 is connected to the output port 36 via the corresponding drive circuit 41, so that the recirculation gas supply device 83 is controlled by an output signal of the electronic control unit 30. Further, a pressure sensor 85 for generating an output voltage proportional to the pressure in the recirculation gas storage tank 80 is attached to the recirculation gas storage tank 80, and the output voltage of the pressure sensor 85 is transmitted via a corresponding AD converter 39. Input port 3
5 is input.

FIG. 8 is an enlarged side sectional view of the engine main body 1. Referring to FIG. 8, the recirculation gas supply device 83 includes an on-off valve 83 a, an actuator 83 b for driving the on-off valve 83 a, and a recirculation gas outlet 8 opening into the sub chamber 4.
3c. Fuel F is supplied from the fuel injection valve 6 to the sub-chamber 4.
Is injected toward one side wall surface of the recirculation gas outlet 83c.
Is directed to the spray formation region by the injected fuel F. Therefore, when the on-off valve 83a is opened by the actuator 83b, the recirculated gas containing NO _x stored in the recirculated gas storage tank 80 is supplied to the recirculated gas supply passage 8.
2 and recirculation gas outlet 83c via on-off valve 83a
From the sprayed fuel F toward the spray forming region.

The fuel spray injected from the fuel injection valve 6 has a diffusion combustion portion, which is an aggregate of droplets, formed at the center thereof.
A premixed combustion section which is sufficiently mixed with air is formed around the diffusion combustion section. In the premixed combustion section, there is sufficient oxygen around the fuel, so NO _x is mainly generated in the premixed combustion section. On the other hand, in the diffusion combustion section, there is not enough air around the fuel droplets, and therefore, the diffusion combustion section is a rich mixture region formed by fuel evaporated from the droplets. When such a rich mixture is formed, an inner shell having strong activity is generated as described above. On the other hand, NO _x is not generated so much in such a rich mixture region, and therefore, in the rich mixture region, the inner shell grows and soot is generated.

[0037] In this case, NO _x when intensively supply the NO _x denser Do mixture region are being made to reducing the inner shell having a strong activity, at the same time inner shell is extinguished without growth is oxidized into soot Resulting in. Thus, simultaneous reduction of NO _x and soot can be achieved. Accordingly injected fuel recirculation gas containing NO _x to provide a concentrated manner NO _x in a region rich Do mixture is formed in the embodiment of the recirculation gas port 83c shown in FIG. 8 F To be sprayed into the spray forming area.

By the way in this case, be in the supplies intensively NO _x in the diffusion combustion portion of a fuel spray jetting recycle gas into the auxiliary chamber 4 near the compression top dead center immediately before or after the start of fuel injection preferable. However, since the pressure in the sub chamber 4 becomes considerably high near the compression top dead center, the recirculation gas is stored in the recirculation gas storage tank 80 in order to eject the recirculation gas into the sub chamber 4 near the compression top dead center. The pressure of the recirculated gas would have to be quite high.

On the other hand, if the pressure in the sub-chamber 4 is low at the beginning of the compression stroke, the recirculated gas is supplied into the sub-chamber 4 at the beginning of the compression stroke. It is not necessary to increase the pressure of the recirculated gas that is used. When the compression stroke is started and the air in the main chamber 3 flows into the sub-chamber 4 from the nozzle 5, a swirl is generated in the sub-chamber 4 as indicated by an arrow S. When the recirculated gas is jetted into the sub-chamber 4, the recirculated gas turns on the swirl in the sub-chamber 4. Thus, in this case, the fuel is injected into the swirling recirculated gas, so that also in this case, NO _x is supplied into the rich mixture region of the fuel spray. However, the degree of concentration of the recirculated NO _x to rich Do mixture region as compared with the case of supplying in the vicinity of the compression top dead center of the recirculation gas in this case is slightly lower.

In the embodiment shown in FIG. 8, the recirculated gas can be supplied into the sub chamber 4 during the intake stroke. However, in this case the concentration level of the recycle NO _x to rich Do mixture region is further reduced. As described above, in the embodiment shown in FIG. 8, the recirculation gas is supplied to the intake stroke or the compression stroke. In this case, as described above, the more the recirculation gas supply timing is delayed, the more the rich mixing is performed. it is possible to increase the degree of concentration of recirculated NO _x to the gas region.

An actuator for driving the on-off valve 83a is provided.
The hydraulic actuator that can be electrically controlled is used as the tutor 83b.
Actuator, mechanical actuator or electric actuator
A tutor can be used. By the way, rich mixing
All inner shells generated in the air disappear without growing to soot
At this time, NO_xGood reduction
To produce NO in proportion to the amount of inner shell generated_xRecirculation including
It is necessary to supply the ring gas into the sub-chamber 4. In this case,
The amount of inner shell generated in a rich mixture is NO_xRecirculate
It can be estimated from the amount of soot generated when there is no soot. FIG.
Represents the amount of depression L of the accelerator pedal and the engine speed N.
Amount of generated soot K₁The amount of inner shell generated is
Soot generation K ₁Will be proportional to Therefore, the on-off valve 8
The valve opening time of 3a is shown in FIG.₁If you make it proportional to
NO in proportion to the amount generated_xCan supply recirculated gas containing
Will be.

The supply amount of the recirculating gas containing NO _x increases as the pressure in the recirculating gas storage tank 80 increases, and therefore the opening time of the on-off valve 83a depends on the pressure in the recirculating gas storage tank 80. Must be taken into account. In this embodiment keep predetermined in the form of a function of the pressure P of the recycle gas storage tank 80 as shown the correction coefficient K ₂ for the valve opening time of the on-off valve 83a in FIG. 10, K shown in FIG. 9 ₁ and K shown in FIG.
The open time T _n of the on-off valve 83a using ₂ T _n = K ₀ ·
It is determined from the equation K ₁ · K ₂ . Here, K ₀ is a constant.

That is, as shown in FIG. 11, first, at step 100, K ₁ is obtained from the relationship shown in FIG. 9, then at step 101, K ₂ is obtained from the relationship shown in FIG. 8
3a obtains the valve opening time _{T n = (K 0 · K} 1 · K 2) , followed so that to supply the processing of the NO _x into auxiliary chamber 4 at step 103.

FIG. 12 shows a case where the present invention is applied to an internal combustion engine in which fuel is directly injected into the combustion chamber 3a. In FIG. 12, the same components as those in FIG. 8 are indicated by the same reference numerals. In this embodiment, the fuel injection valve 6 is disposed at the periphery of the combustion chamber 3a, and the recirculation gas outlet 83c of the recirculation gas supply device 83 is directed to the center of the combustion chamber 3a. From the fuel injection valve 6 is fuel injected toward the central portion of the combustion chamber 3a, the fuel spray this time diffusion combustion portion F ₁ is a collection of droplets is formed at the center thereof, the diffusion combustion portion F ₁ premixed combustion section F ₂ was mixed well with the air around the is formed. The recycle gas containing NO _x in Example is made to ejected toward the forming area of the diffusion combustion portion F ₁ from the recycle gas ejection ports 83c, thus to concentrate recirculation NO _x is the diffusion combustion portion F ₁ Will be supplied. As a result, good simultaneous reduction of soot and NO _x can be achieved.

The case where the present invention is applied to a diesel engine has been described above, but it goes without saying that the present invention can be applied to a gasoline engine. Further, in the embodiments described so far, the fuel is directly injected into the combustion chamber. However, even when the fuel is injected into the intake port, a rich mixture region is formed in the combustion chamber. Where possible, the present invention can be applied. Thereby ejecting a recycle gas containing NO _x towards the combustion chamber in a region rich Do mixture is formed it is preferred in this case.

[0046]

According to the present invention, it is possible to completely prevent NO _x from being released into the atmosphere.

[Brief description of the drawings]

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

FIG. 2 is a diagram for explaining an absorption / release effect of NO _x .

FIG. 3 is a time chart of exhaust gas purification control.

FIG. 4 is a diagram for explaining a soot generation process.

FIG. 5 is a flowchart of exhaust gas purification control.

FIG. 6 is a flowchart of exhaust gas purification control.

FIG. 7 is an overall view showing another embodiment of the internal combustion engine.

FIG. 8 is an enlarged side sectional view of the engine body shown in FIG. 7;

FIG. 9 is a diagram showing the generation amount of soot.

10 is a graph showing the change in the correction factor K _2.

FIG. 11 is a flowchart for controlling the supply of NO _x .

FIG. 12 is a side sectional view showing another embodiment of the internal combustion engine.

[Explanation of symbols]

 16a, 16b: Exhaust passage 17, 22: Flow switching valve 18a, 18b: Heater 19a, 19b: Particulate filter 24a, 24b: Secondary air supply port 28: Exhaust recirculation passage 80: Recirculation gas storage tank 83 ... Recirculated gas supply device

────────────────────────────────────────────────── ─── Continued on the front page (51) Int.Cl. ⁷ Identification code FI F01N 3/08 ZAB F01N 3/08 ZABA F02M 25/07 550 F02M 25/07 550R 580 580D ZAB ZAB (72) Inventor Kotaro Hayashi 1 Toyota Town, Toyota City, Japan Toyota Motor Co., Ltd. (72) Inventor Yasushi Yasushi 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Co., Ltd. (72) Inventor Kiyoshi Kobata 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Co., Ltd. (72) Inventor Tomooto Ishiguro 41-1, Chukumi Yokomichi, Nagakute-cho, Aichi-gun, Aichi Prefecture Toyota Central Research Institute, Inc. (56) References JP-A-6-317142 (JP, A) JP-A-62-159715 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) F01N 3/08-3/36 F01N 3/02

Claims (4)

(57) [Claims] 1. A least rich Do mixture is an internal combustion engine to be burned in the part of the combustion chamber region, and the NO _x trapping means for trapping NO _x contained in the exhaust gas,
NO _x and _the NO _x releasing means allowed to release the captured NO _x by trapping means was released from the NO _x trapping means NO
comprising a NO _x recirculation means allowed to recirculate _x in the combustion chamber, is the NO _x recirculating means the rich Do mixture is of form
Recycle gas containing NO _x towards the combustion chamber of the area
Exhaust purification device for an internal combustion engine that emits water. 2. The overheating in at least a part of the combustion chamber region.
In an internal combustion engine where a rich air-fuel mixture is burned,
And NO _x trapping means for trapping NO _x contained in the gas,
Allowed to release the trapped NO _x by NO _x trapping means
_The NO _x releasing means and, NO released from the NO _x trapping means
NO _x recirculation means for recirculating _x into the combustion chamber
The more the amount of soot generated in the combustion chamber increases, the more the combustion chamber
An exhaust purification system of an internal combustion engine to increase the amount of NO _x is caused to recycle within. 3. The overheating in at least a part of the combustion chamber region.
In an internal combustion engine where a rich air-fuel mixture is burned,
And NO _x trapping means for trapping NO _x contained in the gas,
By increasing the temperature of the NO _x trap, NO
NO that releases NO _x captured by _x capture means
and _x releasing means, the NO _x released from the NO _x trapping means
Comprising a NO _x recirculation means allowed to recycle to the combustion chamber
Exhaust emission control device of an internal combustion engine. 4. An overheating in at least a part of the combustion chamber region.
In an internal combustion engine where a rich air-fuel mixture is burned,
And NO _x trapping means for trapping NO _x contained in the gas,
Allowed to release the trapped NO _x by NO _x trapping means
_The NO _x releasing means and, NO released from the NO _x trapping means
NO _x recirculation means for recirculating _x into the combustion chamber
And Bei, coated the NO _x trapping means the _the NO _x absorbent
Were made from the particulate filter, release the NO _x
The output means is a filter captured by the particulate filter.
_The NO _x absorbent by burning Tikyureto
An exhaust purification system of an internal combustion engine to discharge the absorbed by and NO _x to.