JP2000145505A - Internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely suppress engine vibration at the time of idling by controlling an intake air rate so as to converge engine rotating speed to a target value, and controlling an inert gas rate to the target value so as to converge intake pipe negative pressure to the target value, in a device wherein inert gas is supplied into a combustion chamber. SOLUTION: When inert gas is supplied into a combustion chamber 5, a generating rate of soot is increased, and attains a peak value. After that, when inert gas rate is supplied, a condition becomes an operating condition in which the soot is hardly generated. In such constituted internal combustion engine 1, an intake air rate is controlled to a target value at the time of combustion when an inert gas rate much more than an inert gas rate having peaked soot generating rate is supplied into the combustion chamber, and at the time of an idling operation, and a rate of the inert gas supplied into the combustion chamber 5 is controlled to the target value. After a rate of the inert gas supplied into the combustion chamber 5 is controlled, a rate of fuel injected from a fuel injection valve into the combustion chamber 5 is controlled to the target value so as to surely suppress engine vibration.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to an internal combustion engine.

[0002]

Conventionally than internal combustion engines, for example exhaust gas recirculation and engine exhaust passage and the engine intake passage in order to suppress the generation of the NO _x in the diesel engine (hereinafter, referred to as EGR) connected by passages, the Exhaust gas, that is, EGR gas, is recirculated through the EGR passage into the engine intake passage. In this case, the EGR gas has a relatively high specific heat, and therefore can absorb a large amount of heat.
The combustion temperature in the combustion chamber decreases as the GR gas amount increases, that is, as the EGR rate (EGR gas amount / (EGR gas amount + intake air amount)) increases. When the combustion temperature is lowered to decrease the generated amount of NO _x, thus the generation amount of the more NO _x to be increased EGR rate is lowered.

[0003] It has been found that can reduce the generation amount of the NO _x Thus conventionally increasing the EGR rate. However, when the EGR rate is increased, the soot generation amount, that is, smoke, starts to increase rapidly when the EGR rate exceeds a certain limit. In this regard, it has conventionally been considered that if the EGR rate is further increased, the smoke will increase indefinitely. Therefore, the smoke starts to increase rapidly.
The GR rate is considered to be the maximum allowable limit of the EGR rate.

Therefore, conventionally, the EGR rate is set within a range not exceeding the maximum allowable limit. The maximum allowable EGR rate varies considerably depending on the type of engine and fuel, but is approximately 30 to 50%.
Therefore, in a conventional diesel engine, the EGR rate is at most 3
It is reduced from 0% to about 50%.

As described above, conventionally, it has been considered that the maximum allowable limit exists for the EGR rate.
If the R rate is within the range not exceeding this maximum allowable limit, NO
_It was set so that the amount of _x and smoke generated was as small as possible. However, in this way EGR
Rate that there is a limit to the reduction of the NO _x and the amount of generated NO _x and the amount of smoke produced also defined to be as small as possible of smoke, in fact still a significant amount of N
At present, O _x and smoke are generated.

However, if the EGR rate is made larger than the maximum allowable limit in the course of research on the combustion of a diesel engine, the smoke rapidly increases as described above. However, the amount of generated smoke has a peak, and the peak exceeds this peak. EGR
When the rate is further increased, the smoke starts to decrease rapidly, and when the EGR rate is increased to 70% or more during idling operation, and when the EGR gas is cooled strongly, the smoke is reduced when the EGR rate is increased to about 55% or more. It becomes almost zero. That is, it was found that soot was hardly generated. In this case, N
Generation amount of O _x is also found that a very small amount.
After that, the reason why no soot was generated was examined based on this finding, and as a result, unprecedented soot and NO
_This has led to the construction of a new combustion system capable of simultaneously reducing _x . This new combustion system will be described in detail later, but in short, it is basically based on stopping the growth of hydrocarbons in the middle stage until the hydrocarbons grow into soot.

That is, as a result of repeated experimental studies, it has been found that when the temperature of the fuel and the surrounding gas during combustion in the combustion chamber is lower than a certain temperature, the growth of hydrocarbons is stopped at a halfway stage before reaching soot. However, when the temperature of the fuel and the gas around it rises above a certain temperature, the hydrocarbons grow into soot at a stretch. In this case, the temperature of the fuel and the surrounding gas is greatly affected by the heat absorbing action of the gas around the fuel when the fuel is burned, and the amount of heat absorbed by the gas around the fuel is adjusted according to the calorific value at the time of burning the fuel. As a result, the temperature of the fuel and the surrounding gas can be controlled.

Accordingly, if the temperature of the fuel and the surrounding gas during combustion in the combustion chamber is suppressed to a temperature below the temperature at which the growth of hydrocarbons stops halfway, soot will not be generated, and the fuel during combustion in the combustion chamber and its surroundings will not be generated. Can be suppressed to a temperature below the temperature at which the growth of hydrocarbons stops halfway, by adjusting the amount of heat absorbed by the gas around the fuel. On the other hand, hydrocarbons whose growth has stopped halfway before reaching soot can be easily purified by post-treatment using an oxidation catalyst or the like. This is the basic idea of a new combustion system. An internal combustion engine employing this new combustion system has already been filed by the present applicant (Japanese Patent Application No. 9-305850).

[0009]

By the way, in the new combustion system, the throttle valve is closed to almost fully closed at the time of idling operation, and at this time, the optimum E according to the required load is obtained.
The EGR control valve is closed to near full closure so that the GR gas amount is obtained. However, in order to suppress engine vibration during idling operation, it is necessary to control, for example, the rotational speed and the intake pipe negative pressure to have certain target values.

An object of the present invention is to reliably suppress engine vibration during idling operation.

[0011]

In order to achieve the above object, according to the first invention, as the amount of inert gas supplied into the combustion chamber increases, the amount of soot generated gradually increases and peaks. And when the amount of inert gas supplied into the combustion chamber is further increased, the temperature of the fuel during combustion in the combustion chamber and the temperature of the surrounding gas become lower than the temperature at which soot is generated, so that the internal combustion engine hardly generates soot. During the combustion in which the amount of generated soot is larger than the amount of the inert gas at which the peak is generated, the amount of air supplied into the combustion chamber during the idling operation of the engine during the combustion. Is controlled to be the target value, and then the amount of inert gas supplied into the combustion chamber is controlled to be the target value.
That is, during the idling operation, the intake air amount is sequentially set to the target value, and the inert gas amount is set to the target value.

According to the second invention, in the first invention, the amount of fuel injected into the combustion chamber after controlling the amount of inert gas supplied into the combustion chamber to the target value is set as the target value. Control as much as possible. That is, during the idling operation, the intake air amount, the inert gas amount, and the injected fuel amount are sequentially set as the respective target values. According to the third invention, 2
In the present invention, the timing for injecting fuel into the combustion chamber is controlled to be set to the target value after controlling the amount of fuel injected into the combustion chamber to be set to the target value. That is, during the idling operation, the intake air amount, the inert gas amount, the injected fuel amount, and the fuel injection timing are sequentially set as the respective target values.

According to a fourth aspect, in the first aspect, there is provided a recirculation device for recirculating exhaust gas discharged from the combustion chamber into the engine intake passage, wherein the inert gas is converted from the recirculated exhaust gas. Become. According to a fifth aspect, in the fourth aspect, the exhaust gas recirculation rate is approximately 55% or more.

According to a sixth aspect, in the first aspect, a catalyst having an oxidizing function is disposed in the engine exhaust passage.
In accordance In the sixth invention to a seventh aspect of the invention, said catalyst comprising at least one oxidation catalyst, three-way catalyst or _the NO _x absorbent. According to the eighth invention, in the first invention, the first combustion in which the amount of the inert gas supplied into the combustion chamber is larger than the amount of the inert gas at which the generation amount of soot reaches a peak and soot is hardly generated; Switching means for selectively switching between the second combustion in which the amount of inert gas supplied into the combustion chamber is smaller than the amount of inert gas at which the generation amount of the gas reaches a peak.

According to a ninth aspect, in the eighth aspect, the operating region of the engine is divided into a first operating region on the low load side and a second operating region on the high load side. The first combustion is performed, and the second combustion is performed in the second operation region.

[0016]

FIG. 1 shows a case where the present invention is applied to a four-stroke compression ignition type internal combustion engine. Referring to FIG. 1, 1 is an engine body, 2 is a cylinder block, 3 is a cylinder head, 4 is a piston, 5 is a combustion chamber, 6 is an electrically controlled fuel injection valve, 7 is an intake valve, 8 is an intake port, 9 Denotes an exhaust valve, and 10 denotes an exhaust port. The intake port 8 is connected to a surge tank 12 via a corresponding intake branch pipe 11, and the surge tank 12 is connected to a supercharger, for example, an outlet of a compressor 16 of an exhaust turbocharger 15 via an intake duct 13 and an intercooler 14. Be linked. An inlet of the compressor 16 is connected to an air cleaner 18 via an air suction pipe 17, and a throttle valve 20 driven by a step motor 19 is arranged in the air suction pipe 17. The air suction pipe 17 upstream of the throttle valve 20
A mass flow detector 21 for detecting a mass flow rate of the intake air is disposed therein.

On the other hand, the exhaust port 10 is connected to the exhaust manifold 2.
The exhaust turbine 2 of the exhaust turbocharger 15 via the
3 and an outlet of the exhaust turbine 23 is connected via an exhaust pipe 24 to a catalytic converter 26 having a built-in catalyst 25 having an oxidizing function. Exhaust manifold 22
Inside, an air-fuel ratio sensor 27 is arranged. Exhaust pipe 28 connected to the outlet of catalytic converter 26 and throttle valve 2
The exhaust gas recirculation (hereinafter referred to as E)
(Referred to as GR) through a passage 29, and
E driven by a step motor 30 is provided in the passage 29.
A GR control valve 31 is provided. In the EGR passage 29, an intercooler 32 for cooling the EGR gas flowing in the EGR passage 29 is arranged. In the embodiment shown in FIG. 1, the engine cooling water is guided into the intercooler 32, and the engine cooling water cools the EGR gas.

On the other hand, the fuel injection valve 6 is connected to a fuel reservoir, a so-called common rail 34, via a fuel supply pipe 33. Fuel is supplied into the common rail 34 from an electric control type variable discharge fuel pump 35, and the fuel supplied into the common rail 34 is supplied to the fuel injection valve 6 through each fuel supply pipe 33. A fuel pressure sensor 36 for detecting the fuel pressure in the common rail 34 is attached to the common rail 34, and the fuel pump 35 is controlled so that the fuel pressure in the common rail 34 becomes the target fuel pressure based on the output signal of the fuel pressure sensor 36. Is controlled.

The electronic control unit 40 is composed of a digital computer, and a ROM (read only memory) 42, a RAM (random access memory) 43, a CPU (microprocessor) 44, an input port 45, An output port 46 is provided. The output signal of the mass flow detector 21 is input to the input port 45 via the corresponding AD converter 47, and the output signals of the air-fuel ratio sensor 27 and the fuel pressure sensor 36 are also input to the input port via the corresponding AD converter 47, respectively. 45 is input. A load sensor 51 that generates an output voltage proportional to the amount of depression L of the accelerator pedal 50 is connected to the accelerator pedal 50, and the output voltage of the load sensor 51 is input to the input port 45 via the corresponding AD converter 47. . Also,
The input port 45 has a crank angle sensor 52 that generates an output pulse every time the crankshaft rotates, for example, by 30 °.
Is connected. On the other hand, the output port 46 is connected to the fuel injection valve 6, the throttle valve control step motor 19, the EGR control valve control step motor 3 via the corresponding drive circuit 48.
0 and the fuel pump 35.

FIG. 2 shows the throttle valve 2 when the engine is under low load operation.
Change in the output torque when changing the air-fuel ratio A / F (abscissa in FIG. 2) by changing the opening and the EGR rate of 0, and smoke, HC, CO, a change in emission of the NO _x It shows the experimental example shown. As can be seen from FIG. 2, in this experimental example, the smaller the air-fuel ratio A / F, the higher the EGR rate. When the air-fuel ratio A / F is smaller than the stoichiometric air-fuel ratio (≒ 14.6), the EGR rate is 65% or more.

As shown in FIG. 2, when the air-fuel ratio A / F is reduced by increasing the EGR rate, the smoke is reduced when the EGR rate becomes close to 40% and the air-fuel ratio A / F becomes about 30. The generation starts to increase. Next, when the EGR rate is further increased and the air-fuel ratio A / F is reduced, the amount of smoke generated sharply increases and reaches a peak. Next, when the EGR rate is further increased and the air-fuel ratio A / F is reduced, the smoke is sharply reduced. When the EGR rate is increased to 65% or more and the air-fuel ratio A / F is around 15.0, the smoke becomes almost zero. . That is, almost no soot is generated. At this time, the output torque of the engine slightly decreases, and N
The generation amount of O _x is considerably reduced. On the other hand, at this time, HC,
The amount of generated CO starts to increase.

FIG. 3A shows a change in the combustion pressure in the combustion chamber 5 when the amount of generated smoke is the largest when the air-fuel ratio A / F is around 21, and FIG. 3B shows the air-fuel ratio A / F. The graph shows the change in the combustion pressure in the combustion chamber 5 when the smoke generation amount is substantially zero when F is around 18. As can be seen by comparing FIG. 3 (A) and FIG. 3 (B), in the case of FIG. 3 (B) where the amount of smoke generation is almost zero, FIG.
It can be seen that the combustion pressure is lower than in the case shown in (A).

The following can be said from the experimental results shown in FIGS. That is, first, the air-fuel ratio A / F is 1
FIG. 2 when the smoke generation amount is almost zero at 5.0 or less.
As shown in ₍₁₎ , the generation amount of NOx is considerably reduced. N
That the generation amount of O _x produced falls means that the combustion temperature in the combustion chamber 5 is reduced, thus the combustion temperature in the combustion chamber 5 becomes low when the soot is hardly generated I can say. The same can be said from FIG. That is, in the state shown in FIG. 3B where almost no soot is generated, the combustion pressure is low.
The combustion temperature inside is low.

When the generation amount of the second smoke, that is, the generation amount of soot becomes almost zero, as shown in FIG.
Emissions increase. This means that hydrocarbons are emitted without growing to soot. That is, the linear hydrocarbons and aromatic hydrocarbons contained in the fuel as shown in FIG. 4 are thermally decomposed when the temperature is increased in a state of lack of oxygen, soot precursors are formed, and then mainly, Soot consisting of a solid aggregate of carbon atoms is produced. In this case, the actual soot production process is complicated, and it is not clear what form the soot precursor takes, but in any case, the hydrocarbon as shown in FIG. It will grow to soot. Therefore, as described above, when the amount of generated soot becomes substantially zero, the emission amounts of HC and CO increase as shown in FIG. 2, but HC at this time is a precursor of soot or a hydrocarbon in a state before it. .

The above considerations based on the experimental results shown in FIGS. 2 and 3 can be summarized as follows. When the combustion temperature in the combustion chamber 5 is low, the amount of soot generation becomes almost zero. Is discharged from the combustion chamber 5. As a result of further detailed experimental study on this, if the temperature of the fuel and the surrounding gas in the combustion chamber 5 is lower than a certain temperature, the growth process of the soot is stopped halfway, that is, the soot is It was found that no soot was generated, and soot was generated when the temperature of the fuel and its surroundings in the combustion chamber 5 exceeded a certain temperature.

The temperature of the fuel and its surroundings when the process of producing hydrocarbons is stopped in the state of the soot precursor, that is, the above-mentioned certain temperature, depends on various factors such as the type of fuel and the compression ratio of the air-fuel ratio. Although the change can not be said that how many times since this certain temperature has a generation amount and the closely related of the nO _x, therefore this certain temperature is defined to a certain degree from the generation amount of the nO _x be able to. That is, the fuel and the gas temperature surrounding it at the time of combustion and the greater the EGR rate, decreases, the amount of the NO _x is reduced. Generation amount at this time NO _x is soot is hardly generated when it is around or less 10 ppm. Therefore, the above certain temperature is NO
It almost coincides with the temperature when the amount of generated _x is about 10 p.pm or less.

Once soot has been produced, it cannot be purified by post-treatment using a catalyst having an oxidizing function. On the other hand, the soot precursor or the hydrocarbon in a state before the soot can be easily purified by a post-treatment using a catalyst having an oxidation function. Considering the post-treatment with the catalyst having the oxidation function as described above, it is determined whether the hydrocarbon is discharged from the combustion chamber 5 in the state of the precursor of soot or in a state before the soot, or is discharged from the combustion chamber 5 in the form of soot. There is a huge difference. The new combustion system employed in the present invention discharges hydrocarbons from the combustion chamber 5 in the form of a soot precursor or previous state without producing soot in the combustion chamber 5 and removes the hydrocarbons. The core is to oxidize with a catalyst having an oxidation function. Note the catalyst having an oxidation function oxidation catalyst, three-way catalyst, there is _the NO _x absorbent.

Now, in order to stop the growth of hydrocarbons before the soot is generated, the temperature of the fuel and the surrounding gas during combustion in the combustion chamber 5 is set to a temperature lower than the temperature at which the soot is generated. It needs to be suppressed. In this case, it has been found that the endothermic effect of the gas around the fuel when the fuel burns has an extremely large effect on suppressing the temperature of the fuel and the gas around the fuel.

That is, if there is only air around the fuel, the evaporated fuel immediately reacts with oxygen in the air and burns. In this case, the temperature of the air separated from the fuel does not rise so much, and only the temperature around the fuel becomes extremely high locally. That is, at this time, almost no heat absorbing action of the combustion heat of the fuel of the air separated from the fuel is performed. In this case, since the combustion temperature becomes extremely high locally, the unburned hydrocarbons that have received the heat of combustion will generate soot.

On the other hand, the situation is slightly different when fuel is present in a mixed gas of a large amount of inert gas and a small amount of air.
In this case, the fuel vapor diffuses to the surroundings, reacts with oxygen mixed in the inert gas, and burns. In this case, the combustion temperature is not increased so much because the combustion heat is absorbed by the surrounding inert gas. That is, the combustion temperature can be kept low. That is, the presence of the inert gas plays an important role in suppressing the combustion temperature, and the combustion temperature can be kept low by the endothermic effect of the inert gas.

In this case, in order to suppress the temperature of the fuel and the surrounding gas to a temperature lower than the temperature at which the soot is formed, an amount of the inert gas that can absorb a sufficient amount of heat to do so is required. . Therefore, if the fuel amount increases, the required amount of inert gas increases accordingly. In this case, as the specific heat of the inert gas increases, the endothermic effect becomes stronger. Therefore, the inert gas preferably has a higher specific heat. In this regard, it can be said that it is preferable to use EGR gas as the inert gas since CO ₂ and EGR gas have relatively large specific heats.

FIG. 5 shows the relationship between the EGR rate and smoke when the EGR gas is used as the inert gas and the degree of cooling of the EGR gas is changed. That is, in FIG. 5, a curve A indicates that the EGR gas temperature is substantially 9
Curve B shows the case where the EGR gas is cooled by a small cooling device, and curve C shows the case where the temperature is maintained at 0 ° C.
Indicates a case where the EGR gas is not forcibly cooled.

As shown by the curve A in FIG. 5, when the EGR gas is cooled strongly, the soot generation peaks at a point where the EGR rate is slightly lower than 50%. Above a percentage, little soot is generated. On the other hand, as shown by the curve B in FIG. 5, when the EGR gas is slightly cooled, the soot generation amount reaches a peak at a point where the EGR rate is slightly higher than 50%. In this case, the EGR rate is increased to about 65% or more. If so, almost no soot is generated.

As shown by the curve C in FIG.
When the R gas is not forcibly cooled, the EGR rate becomes 5
The soot generation amount peaks near 5%, and in this case, if the EGR rate is set to approximately 70% or more, soot is hardly generated. FIG. 5 shows the amount of smoke generated when the engine load is relatively high. When the engine load decreases, the EGR rate at which the amount of soot peaks slightly decreases, and the EGR rate at which soot is hardly generated is reduced. Also lowers slightly. The lower limit of the EGR rate at which such soot is hardly generated varies depending on the degree of cooling of the EGR gas and the engine load.

FIG. 6 shows the mixing of EGR gas and air necessary to make the temperature of fuel during combustion and the surrounding gas temperature lower than the temperature at which soot is generated when EGR gas is used as the inert gas. It shows the gas amount, the ratio of air in the mixed gas amount, and the ratio of EGR gas in the mixed gas. In FIG. 6, the vertical axis indicates the total intake gas amount sucked into the combustion chamber 5, and the dashed line Y indicates the total intake gas amount that can be sucked into the combustion chamber 5 when supercharging is not performed. ing. The horizontal axis indicates the required load.

Referring to FIG. 6, the proportion of air, that is, the amount of air in the mixed gas, indicates the amount of air necessary to completely burn the injected fuel. That is, in the case shown in FIG. 6, the ratio between the air amount and the injected fuel amount is the stoichiometric air-fuel ratio. On the other hand, in FIG. 6, the ratio of the EGR gas, that is, the amount of the EGR gas in the mixed gas, is set so that when the injected fuel is burned, the temperature of the fuel and the surrounding gas is lower than the temperature at which soot is formed. The required minimum EGR gas amount is shown. This EGR gas amount is approximately 55% or more in terms of the EGR rate. In the embodiment shown in FIG.
0% or more. That is, the total intake gas amount sucked into the combustion chamber 5 is indicated by a solid line X in FIG. 6, and the ratio of the air amount to the EGR gas amount in the total intake gas amount X is shown in FIG.
When the ratio is as shown in the following, the temperature of the fuel and the surrounding gas is lower than the temperature at which soot is generated, and thus no soot is generated. Further, the NO _x generation amount at this time is around 10 p.pm or less.
The amount of O _x generated is extremely small.

If the fuel injection amount increases, the amount of heat generated when the fuel burns increases. Therefore, in order to maintain the temperature of the fuel and the surrounding gas at a temperature lower than the temperature at which the soot is generated, the heat generated by the EGR gas is required. Must be increased. Therefore, as shown in FIG. 6, the EGR gas amount must be increased as the injected fuel amount increases.
That is, the EGR gas amount needs to increase as the required load increases.

By the way, when supercharging is not performed,
The upper limit of the total intake gas amount X sucked into the firing chamber 5 is Y.
Therefore, in FIG.₀Territory larger than
In the region, the EGR gas ratio increases as the required load increases.
The air-fuel ratio can be maintained at the stoichiometric air-fuel ratio unless reduced.
Can not. In other words, it is necessary when there is no supercharging.
Load demand is L₀Air-fuel ratio in the larger area than theoretical
When trying to maintain the fuel ratio, the required load increases.
As a result, the EGR rate decreases, and thus the required load becomes L ₀Than
In areas where the fuel and the surrounding gas temperature are
It will not be possible to maintain a temperature lower than the temperature produced.

[0039] However recirculating the required load is larger than L ₀ of the EGR gas into the air intake pipe 17 on the inlet side i.e. the exhaust turbocharger 15 via the EGR passage 29 supercharger as shown in FIG. 1 EGR rate of 5 in the region
It can be maintained at 5% or more, for example 70%, so that the temperature of the fuel and its surrounding gas can be kept below the temperature at which soot is produced. That is, if the EGR gas is recirculated so that the EGR rate in the air suction pipe 17 becomes, for example, 70%, the EGR rate of the suction gas boosted by the compressor 16 of the exhaust turbocharger 15 also becomes 70%. The temperature of the fuel and the surrounding gas can be maintained at a temperature lower than the temperature at which soot is generated, to the extent that the pressure can be increased by the compressor 16. Therefore, the operating range of the engine that can generate low-temperature combustion can be expanded. E is when the required load is the EGR rate more than 55 percent in the region larger than L ₀
The GR control valve 31 is fully opened, and the throttle valve 20 is slightly closed.

As described above, FIG. 6 shows the case where the fuel is burned under the stoichiometric air-fuel ratio. However, even if the air amount is made smaller than the air amount shown in FIG. Even so, while suppressing the generation of soot, the amount of generated NOx was reduced to 10 _p .
pm or less, and even if the air amount is larger than the air amount shown in FIG. 6, that is, even if the average value of the air-fuel ratio is 17 to 18 lean, soot generation is prevented. while the generation amount of the NO _x can be around or less 10 ppm.

That is, when the air-fuel ratio is made rich, the fuel becomes excessive, but since the combustion temperature is suppressed to a low temperature, the excess fuel does not grow into soot, and soot is generated. There is no. Further, at this time NO _x even only an extremely small amount of generated. On the other hand, when the average air-fuel ratio is lean, or even when the air-fuel ratio is the stoichiometric air-fuel ratio, a small amount of soot is generated if the combustion temperature increases, but in the present invention, the soot is suppressed to a low temperature, so that the soot is reduced. Not generated at all. Furthermore, NO _x
Only very small amounts are generated.

As described above, when low-temperature combustion is performed, soot is generated regardless of the air-fuel ratio, that is, whether the air-fuel ratio is rich, the stoichiometric air-fuel ratio, or the average air-fuel ratio is lean. Sarezu, the amount of the NO _x becomes extremely small. Therefore, considering the improvement of the fuel consumption rate, it can be said that it is preferable to make the average air-fuel ratio lean at this time.

By the way, the temperature of the fuel and the surrounding gas during combustion in the combustion chamber can be suppressed to a temperature below the temperature at which the growth of hydrocarbons stops halfway, only when the engine is operating at low load and the calorific value due to combustion is relatively small. Can be Therefore, in the embodiment according to the present invention, the first combustion, that is, the low-temperature combustion is performed by suppressing the temperature of the fuel during combustion and the gas temperature around the same at or below the temperature at which the growth of hydrocarbons stops halfway during the low load operation in the engine. In addition, the second combustion, that is, the combustion that is usually performed conventionally, is performed during the high load operation of the engine. Here, the first combustion, that is, the low-temperature combustion, has a larger amount of the inert gas in the combustion chamber than the amount of the inert gas at which the soot generation amount is at a peak, as is clear from the description so far. The second combustion, that is, the combustion that has been conventionally performed, is the combustion in which the amount of inert gas in the combustion chamber is smaller than the amount of inert gas at which the amount of soot generation peaks. Say

FIG. 7 shows a first operation region I in which the first combustion, that is, low-temperature combustion is performed, and a second operation region II in which the second combustion, that is, combustion by the conventional combustion method, is performed. I have. In FIG. 7, the vertical axis L indicates the amount of depression of the accelerator pedal 50, that is, the required load, and the horizontal axis N indicates the engine speed. In FIG. 7, X (N) is the first
Shows the first boundary between the operating region I and the second operating region II, and Y (N) represents the first operating region I and the second operating region.
2 shows a second boundary with II. The determination of the change of the operating range from the first operating range I to the second operating range II is made based on the first boundary X (N), and the determination of the change from the second operating range II to the first
The determination of the change of the operation region to the operation region I of the second boundary Y
(N).

That is, when the operating state of the engine is in the first operating region I
When the required load L exceeds a first boundary X (N), which is a function of the engine speed N, during low-temperature combustion, it is determined that the operation region has shifted to the second operation region II, Combustion is performed by a conventional combustion method. Next, when the required load L becomes lower than a second boundary Y (N) which is a function of the engine speed N, it is determined that the operation region has shifted to the first operation region I, and low-temperature combustion is performed again.

The two boundaries of the first boundary X (N) and the second boundary Y (N) on the lower load side than the first boundary X (N) are provided in the following two cases. For three reasons. The first reason is that the combustion temperature is relatively high on the high load side of the second operation region II, and even if the required load L becomes lower than the first boundary X (N), low-temperature combustion cannot be performed immediately. Because. That is, the low-temperature combustion does not immediately start unless the required load L becomes considerably low, that is, when the required load L becomes lower than the second boundary Y (N). The second reason is that hysteresis is provided for a change in the operation range between the first operation range I and the second operation range II.

By the way, when the operating region of the engine is in the first operating region I and low-temperature combustion is being performed, soot is hardly generated, and instead, the unburned hydrocarbon is replaced with the precursor of soot or the state before it. It is discharged from the combustion chamber 5 in the form. At this time, unburned hydrocarbons discharged from the combustion chamber 5 are purified by an oxidation catalyst described later in detail. FIG. 8 shows the air-fuel ratio sensor 27.
Shows the output. As shown in FIG. 8, the output current I of the air-fuel ratio sensor 27 changes according to the air-fuel ratio A / F.
Therefore, the air-fuel ratio can be known from the output current I of the air-fuel ratio sensor 27.

Next, the operation control in the first operation region I and the second operation region II will be schematically described with reference to FIG. FIG. 9 shows the throttle valve 2 with respect to the required load L.
0 indicates the opening degree, the opening degree of the EGR control valve 31, the EGR rate, the air-fuel ratio, the injection timing, and the injection amount. As shown in FIG. 9, in the first operating region I where the required load L is low, the opening of the throttle valve 20 is gradually increased from almost fully closed to about 2/3 opening as the required load L increases. E
The degree of opening of the GR control valve 31 is gradually increased from almost fully closed to fully open as the required load L increases. Also,
In the example shown in FIG. 9, in the first operation region I, the EGR rate is set to approximately 70%, and the air-fuel ratio is set to a slightly lean air-fuel ratio.

In other words, in the first operating region I, the EGR
The opening of the throttle valve 20 and the opening of the EGR control valve 31 are controlled such that the rate becomes approximately 70% and the air-fuel ratio becomes a slightly lean air-fuel ratio. In the first operation region I, fuel injection is performed before the compression top dead center TDC. In this case, the injection start timing θS is delayed as the required load L is increased, and the injection completion timing θE is delayed as the injection start timing θS is delayed.

During the idling operation, the throttle valve 20 is closed until the valve is almost fully closed. At this time, the EGR control valve 31 is also closed almost completely. Throttle valve 2
If the valve is closed close to 0, the pressure in the combustion chamber 5 at the start of compression decreases, so that the compression pressure decreases. When the compression pressure decreases, the compression work by the piston 4 decreases, so that the vibration of the engine body 1 decreases. That is, at the time of idling operation, the throttle valve 20 is closed to almost fully closed in order to suppress the vibration of the engine body 1.

On the other hand, the operating range of the engine is the first operating range I.
From the second operating region II to the second operating region II, the opening of the throttle valve 20 is increased stepwise from about 2/3 opening toward the full opening direction. At this time, in the example shown in FIG. 9, the EGR rate is reduced stepwise from approximately 70% to 40% or less, and the air-fuel ratio is increased stepwise. That is, the EGR rate at which the EGR rate generates a large amount of smoke
The engine operating range is the first because it jumps over the rate range (Fig. 5).
A large amount of smoke does not occur when changing from the operating region I to the second operating region II.

In the second operating region II, the conventional combustion is performed. In the second operating region II, the throttle valve 20 is held in a fully open state except for a part, and the opening of the EGR control valve 31 is gradually reduced as the required load L increases. In this operating region II, the EGR rate decreases as the required load L increases, and the air-fuel ratio decreases as the required load L increases. However, the air-fuel ratio is a lean air-fuel ratio even when the required load L increases. In the second operation region II, the injection start timing θS is set near the compression top dead center TDC. FIG. 10A shows the target air-fuel ratio A / F in the first operation region I. In FIG. 10A, A /
F = 15.5, A / F = 16, A / F = 17, A / F =
Each curve indicated by 18 has a target air-fuel ratio of 15.5, 1
6, 17, and 18, and the air-fuel ratio between the curves is determined by proportional distribution. As shown in FIG. 10A, the air-fuel ratio is lean in the first operating region I, and the target air-fuel ratio A / F becomes leaner as the required load L decreases in the first operating region I. You.

That is, the lower the required load L, the smaller the amount of heat generated by combustion. Therefore, low-temperature combustion can be performed even if the EGR rate is reduced as the required load L decreases. When the EGR rate is reduced, the air-fuel ratio increases. Therefore, as shown in FIG. 10A, as the required load L decreases, the target air-fuel ratio A / F increases. As the target air-fuel ratio A / F increases, the fuel consumption rate increases. Therefore, in order to make the air-fuel ratio as lean as possible, in the embodiment according to the present invention, as the required load L decreases, the target air-fuel ratio A / F increases.
Is increased.

Note that the target air-fuel ratio A / F shown in FIG. 10A is stored in the ROM 4 in advance in the form of a map as a function of the required load L and the engine speed N as shown in FIG.
2 is stored. Also, the throttle valve 2 required to set the air-fuel ratio to the target air-fuel ratio A / F shown in FIG.
The target opening ST of 0 is stored in the ROM 42 in advance in the form of a map as a function of the required load L and the engine speed N as shown in FIG.
EGR required to achieve target air-fuel ratio A / F shown in (A)
As shown in FIG. 11B, the target opening SE of the control valve 31 is stored in the ROM 42 in advance in the form of a map as a function of the required load L and the engine speed N.

When the first combustion is being performed, the fuel injection amount Q is calculated based on the required load L and the engine speed N. The fuel injection amount Q is stored in the ROM 42 in advance in the form of a map as a function of the required load L and the engine speed N as shown in FIG. FIG.
(A) shows the target air-fuel ratio A / F when the second combustion, that is, the normal combustion by the conventional combustion method is performed.
In FIG. 13A, A / F = 24 and A / F = 3.
Curves indicated by 5, A / F = 45 and A / F = 60 indicate target air-fuel ratios 24, 35, 45, and 60, respectively. The target air-fuel ratio A / F shown in FIG.
As shown in (1), a map is previously stored in the ROM 42 as a function of the required load L and the engine speed N. In addition, the air-fuel ratio is set to a target air-fuel ratio A / A shown in FIG.
The target opening ST of the throttle valve 20 required to obtain F is stored in the ROM 42 in advance in the form of a map as a function of the required load L and the engine speed N as shown in FIG. The target opening degree S of the EGR control valve 31 necessary for setting the air-fuel ratio to the target air-fuel ratio A / F shown in FIG.
E is stored in the ROM 42 in advance in the form of a map as a function of the required load L and the engine speed N as shown in FIG.

When the second combustion is being performed, the fuel injection amount Q is calculated based on the required load L and the engine speed N. The fuel injection amount Q is stored in the ROM 42 in advance as a function of the required load L and the engine speed N as shown in FIG. By the way, in FIG. 1, the NO _x absorbent 25 is disposed in the casing 26. The NO _x absorbent 25 uses, for example, alumina as a carrier, and, for example, potassium K, sodium N
a, at least one selected from alkali metals such as lithium Li and 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. It is carried. Engine intake passage, combustion chamber 5 and NO
_x absorbent 25 upstream of the exhaust passage supplying air and fuel into _the NO _x absorbent 25 the ratio of Toko called air-fuel ratio of the exhaust gas flowing into _the NO _x absorbent 25 (hydrocarbon) is in the inflowing exhaust gas air absorbs NO _x when the lean air-fuel ratio of the inflowing exhaust gas is performed to absorbing and releasing action of the NO _x that releases NO _x absorbed and becomes the stoichiometric air-fuel ratio or rich.

If this NO _x absorbent 25 is disposed in the exhaust passage of the engine, the NO _x absorbent 25 actually performs the absorption and release of NO _x , but the detailed mechanism of the absorption and release is not clear in some parts. . However, it is considered that this absorption / release action is performed by a mechanism as shown in FIG. Next, 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.

In the compression ignition type internal combustion engine shown in FIG. 1, combustion is performed with the air-fuel ratio in the normal combustion chamber 5 being lean. Thus the oxygen concentration in the exhaust gas when the air-fuel ratio is performed is combusted in a lean state is high, these oxygen O ₂ as is shown in FIG. 16 (A) at this time O
₂ ^- or O ^2- shape is deposited on the surface of the platinum Pt. on the other hand,
NO in the inflowing exhaust gas reacts with O ₂ ⁻ or O ²⁻ on the surface of the platinum Pt to become NO ₂ (2NO + O ₂ → 2N).
O ₂ ). Next, a part of the generated NO ₂ is absorbed in the absorbent while being oxidized on the platinum Pt, and the barium oxide BaO
As shown in FIG. 16 (A), it is diffused into the absorbent in the form of nitrate ion NO ₃ ⁻ while being combined. In this way, NO _x is absorbed in the NO _x absorbent 25. NO ₂ is produced on the surface of the platinum Pt so long as the oxygen concentration in the inflowing exhaust gas is high, NO unless absorption of NO _x capacity of the absorbent is not saturated
₂ is absorbed in the absorbent and nitrate ions NO ₃ ^- are produced.

On the other hand, the air-fuel ratio of the inflowing exhaust gas is made rich.
The concentration of oxygen in the incoming exhaust gas decreases,
NO on the surface of gold Pt_TwoIs reduced. NO_Twoof
When the amount of production decreases, the reaction reverses (NO_Three ^-→ NO_Two)
And thus nitrate ion NO in the absorbent_Three ^-Is NO
_TwoReleased from the absorbent in the form of NO at this time_xAbsorbent
NO released from 25_xIs shown in FIG. 16 (B).
A large amount of unburned HC and CO contained in the inflow exhaust gas
It is reduced by reaction. In this way, platinum Pt
NO on surface_TwoWhen no longer exists, the next
NO_TwoIs released. Therefore, the air-fuel ratio of the incoming exhaust gas
Is enriched in a short time, NO _xAbsorbent 25?
NO_xIs released, and the released NO_xIs returned
NO in the atmosphere to be removed_xWill not be released
No.

In this case, the air-fuel ratio of the inflowing exhaust gas is
NO even at stoichiometric air-fuel ratio_xNO from absorbent 25_xIs released
Is done. However, the air-fuel ratio of the inflowing exhaust gas is
NO if ratio_xNO from absorbent 25_xGradually
NO because only _xAbsorbed by the absorbent 25
All NO_xIt takes a slightly longer time to release.

As described above, the NO _x absorbent 25 is made of platinum P
includes a noble metal such as t, therefore _the NO _x absorbent 2
5 has an oxidation function. On the other hand, as described above, when the operation state of the engine is in the first operation region I and low-temperature combustion is being performed, soot is hardly generated, and instead, the unburned hydrocarbon is a precursor of soot or a soot. It is discharged from the combustion chamber 5 in the form of a state. However, as described above, the NO _x absorbent 25 has an oxidizing function, and therefore, the unburned hydrocarbons discharged from the combustion chamber 5 at this time are oxidized well by the NO _x absorbent 25.

[0062] Incidentally the absorption of NO _x capacity of the NO _x absorbent 25 is limited, absorption of NO _x capacity of the NO _x absorbent 25 needs to release the NO _x from the NO _x absorbent 25 before saturation. For this purpose it is necessary to estimate the amount of NO _x is absorbed in the NO _x absorbent 25. Therefore, in this embodiment of the present invention of a map as shown in FIG. 17 (A) as a function of the NO _x absorption amount A of the required load L and engine speed N per unit time when it is performed first combustion is previously obtained in the form of a map as shown in FIG. 17 (B) the absorption of NO _x amount B per unit time as a function of the required load L and engine speed N when the second combustion is being performed It is previously obtained in the form, per these unit time of absorption of NO _x amount a, so that to estimate the amount of NO _x ΣNOX being absorbed in the NO _x absorbent 25 by integrating the B.

[0063] Figure 18 shows the processing routine for _the NO _x releasing flag which is set when releasing the NO _x from the NO _x absorbent 25, this routine is executed by interruption every predetermined time. Referring to FIG. 18, first, at step 100, it is determined whether or not a graph I indicating that the operation region of the engine is the first operation region I is set. When the flag I is set, that the operating region of the engine absorption of NO _x amount A per unit time from the map shown in FIG. 17 (A) is calculated proceeds to step 101 when a first operating region I You. Then A is added to the absorption of NO _x amount ΣNOX step 102. Next, at step 103 NO _x absorption amount ΣNOX whether exceeds the allowable maximum value MAX1 is determined. ΣN
If OX> MAX1, NO in step 104 for time
A process of setting the _x release flag 1 is performed, and then, in step 105, ΣNOX is made zero.

On the other hand, when it is determined in step 100 that the flag I has been reset, that is, when the operation region of the engine is the second operation region II, step 106
Absorption of NO _x per unit from the map time shown in FIG. 17 (B) B is calculated willing to. Then B is added to the absorption of NO _x amount ΣNOX step 107. Next, at step 108 NO _x absorption amount ΣNOX permissible maximum value MA
It is determined whether or not X2 has been exceeded. ΣNOX> MAX2
Becomes a process of setting the _the NO _x releasing flag 2 by a predetermined time the routine proceeds to step 109 is performed, then ΣNOX is made zero at step 110.

Next, the operation control will be described with reference to FIG. Referring to FIG. 19, first, Step 2
At 00, it is determined whether or not a flag I indicating that the operating state of the engine is in the first operating region I is set. When the flag I is set, that is, when the operating state of the engine is in the first operating region I, step 20 is executed.
The program proceeds to 1 to determine whether the required load L has become larger than the first boundary X1 (N). When L ≦ X1 (N), the routine proceeds to step 203, where low-temperature combustion is performed.

That is, in step 203, the target opening ST of the throttle valve 20 is calculated from the map shown in FIG. 11A, and the opening of the throttle valve 20 is set to the target opening ST. Next, at step 204, the target opening degree SE of the EGR control valve 31 is calculated from the map shown in FIG.
The opening of the EGR control valve 31 is set as the target opening SE.
Next, at step 205 NO _x releasing flag 1 is whether it is set or not. When the NO _x release flag 1 is not set, the routine proceeds to step 206, where the injection control I described in detail later is performed.

[0067] On the other hand, the injection control II is performed to make the average air-fuel ratio in the combustion chamber 5 proceeds to step 208 to rich when _the NO _x releasing flag 1 is judged as being set in step 205. In this case NO _x is released from the NO _x absorbent 25. On the other hand, step 201
When it is determined that L> X (N), the routine proceeds to step 202, where the flag I is reset. Then, the routine proceeds to step 211, where the second combustion is performed.

That is, in step 211, the target opening ST of the throttle valve 20 is calculated from the map shown in FIG. 14A, and the opening of the throttle valve 20 is set to this target opening ST. Next, at step 211, the target opening degree SE of the EGR control valve 31 is calculated from the map shown in FIG.
The opening of the EGR control valve 31 is set as the target opening SE.
Then whether _the NO _x releasing flag 2 in step 213 is set or not. When the NO _x release flag 2 is not set, the routine proceeds to step 214, where the fuel injection of the amount Q calculated from the map of FIG. 15 is performed so as to obtain the air-fuel ratio shown in FIG. At this time, the second combustion is performed under the lean air-fuel ratio.

[0069] On the other hand, the injection control IV is performed proceeds to step 216 when _the NO _x releasing flag 2 has been determined to have been set in step 213. That is, FIG.
Air-fuel ratio so as to fuel injection quantity Q calculated from the map of FIG. 15 is performed, additional fuel late or during the exhaust stroke of the expansion stroke so as to release the NO _x from the NO _x absorbent 25 shown in Is injected.

When the flag I is reset, in the next processing cycle, the process proceeds from step 200 to step 209 to determine whether the required load L has become lower than the second boundary Y (N). If L ≧ Y (N), step 211
And the second combustion is performed under the lean air-fuel ratio.
On the other hand, when it is determined in step 209 that L <Y (N), the routine proceeds to step 210, where the flag I is set. Next, the routine proceeds to step 203, where low-temperature combustion is performed.

Next, the injection control I of the present invention will be described. In the injection control I of the present invention, first, it is determined whether or not the engine is currently idling. When the idling operation is not being performed, the throttle valve and the EGR valve are respectively set to Step 20.
Fuel is injected such that the air-fuel ratio shown in FIG. 10 is obtained while maintaining the opening calculated in steps 3 and 204. On the other hand, during idling operation, injection control different from this is performed. Next, this will be described in detail.

During idling operation, engine vibration is likely to occur. To suppress this vibration, the engine speed is set to a certain target speed, the intake pipe negative pressure is set to a certain target negative pressure, and the air-fuel ratio is set to a certain target negative pressure. It is necessary to set the air-fuel ratio and change the pressure in the combustion chamber 5 to a certain target pressure change. However, there is a close relationship between these parameters, and when controlling one parameter to be a target value and then controlling another parameter to be a target value, the actual value of the already controlled parameter changes. Thus, it is necessary to control the parameter again so as to be a target value. That is, in order to set the actual value of each parameter to the target value, it is necessary to control each parameter in a predetermined order.

Therefore, in the present invention, when the engine is idling, first, the opening ST of the throttle valve 20 is corrected so that the actual rotational speed is set to the target rotational speed. Next, the opening degree SE of the EGR valve 31 is corrected so that the intake pipe negative pressure becomes the target intake pipe negative pressure. However, if the intake pipe negative pressure is set as the target intake pipe negative pressure, the actual intake air amount changes, and as a result, the rotational speed changes. However, this change corrects, for example, the opening degree SE of the EGR valve 31 so that the actual rotation speed becomes the target rotation speed, and then opens the throttle valve 20 so that the actual intake pipe negative pressure becomes the target intake pipe negative pressure. It is smaller than the change when ST is corrected. That is, controlling the rotational speed and the intake pipe negative pressure by the procedure of the present invention can make these parameters target values earlier.

After the opening degrees of the throttle valve 20 and the EGR valve 31 are corrected in this way, the amount of injected fuel is corrected so that the air-fuel ratio becomes the target air-fuel ratio. That is, the injection fuel amount for making the air-fuel ratio the target air-fuel ratio is corrected based on the intake air amount. Even if the injection fuel amount is corrected at this stage, the rotation speed and the intake pipe negative pressure are not significantly affected, and it is not necessary to control the throttle valve 20 and the EGR valve 31 again to set these parameters to the target values.

After the fuel injection amount has been corrected in this way, the fuel injection timing is corrected so that the pressure change in the combustion chamber 5 becomes the target pressure change. Even if the fuel injection timing is corrected at this stage, the rotation speed, the intake pipe negative pressure, and the fuel injection amount are not significantly affected, and even if it is necessary to re-control these parameters to the target values, it is extremely small. is there. As described above, in the present invention, when the operation of the engine component is corrected in order to set a certain parameter to the target value, even if it is necessary to correct the operation of the engine component corrected before this correction again, it is extremely small. There is very little divergence of each target value and control hunting. Thus, according to the present invention, a parameter that requires control to suppress engine vibration during idling operation can be set to a target value at an early stage.

FIG. 20 is a flowchart showing the injection control I. First, in step 300, the required load L
Is smaller than the boundary Z (N). Here, the third boundary Z (N) is smaller than the second boundary Y (N).
When L ≧ Z (N) in step 300, the routine proceeds to step 306, where injection control VI is performed. That is, the fuel of the amount Q shown in FIG. 12 is injected to obtain the air-fuel ratio shown in FIG. On the other hand, in step 300, L <Z
If it is (N), the routine proceeds to step 301, where the opening degree ST of the throttle valve 20 is set so that the actual rotational speed becomes the target rotational speed.
Is corrected. Next, the routine proceeds to step 302, where the opening degree SE of the EGR valve 31 is corrected so that the intake pipe negative pressure becomes the target intake pipe negative pressure. In the present invention, the surge tongue 12 is provided with a pressure sensor 53 for detecting the intake pipe negative pressure. The output signal of the pressure sensor 53 is input to the input port 45 via the corresponding AD converter 47. Next, step 303
Then, the injected fuel amount Q is corrected based on the intake air amount so that the air-fuel ratio becomes the target air-fuel ratio. Then step 304
The fuel injection timing θ is corrected so that the pressure change in the combustion chamber 5 becomes the target pressure change. In the present invention, the combustion chamber 5
Pressure sensor 5 for detecting the pressure in combustion chamber 5 inside
4 are arranged. The output signal of the combustion pressure sensor 54 is input to the input port 45 via the corresponding AD converter 47. Finally, in step 305, the operation of each engine component is controlled based on the corrected control value.

[0077]

By controlling the intake air amount to be the target value, the engine speed becomes the target value, and then by controlling the inert gas amount to the target value, the negative pressure of the intake pipe is reduced. It will be the target value. When the inert gas amount is set to the target value after the intake air amount is set to the target value, the intake air amount actually deviates from the target value, but the deviation amount is small, and the engine vibration during idling operation is reduced. It can be said that the engine speed and the intake pipe negative pressure, which need to be controlled in order to suppress the pressure, are almost the respective target values. Therefore, engine vibration during idling operation is reliably suppressed.

[Brief description of the drawings]

FIG. 1 is an overall view of a compression ignition type internal combustion engine.

FIG. 2 is a diagram showing amounts of smoke and NO _x generated, and the like.

FIG. 3 is a diagram showing a combustion pressure.

FIG. 4 is a diagram showing fuel molecules.

FIG. 5 is a diagram showing a relationship between a generation amount of smoke and an EGR rate.

FIG. 6 is a diagram showing a relationship between an injected fuel amount and a mixed gas amount.

FIG. 7 is a diagram showing a first operation region I and a second operation region II.

FIG. 8 is a diagram showing an output of an air-fuel ratio sensor.

FIG. 9 is a view showing an opening degree of a throttle valve and the like.

FIG. 10 is a diagram showing an air-fuel ratio and the like in a first operation region I.

FIG. 11 is a diagram showing a map of a target opening degree of a throttle valve and the like.

FIG. 12 is a diagram showing a map of a fuel injection amount.

FIG. 13 is a diagram showing an air-fuel ratio and the like in a second operation region.

FIG. 14 is a view showing a map of a target opening degree of a throttle valve and the like.

FIG. 15 is a view showing a map of a fuel injection amount.

FIG. 16 is a view for explaining the NO _x absorption / release action.

FIG. 17 is a diagram showing a map of the NO _x absorption amount per unit time.

FIG. 18 is a flowchart for processing a NO _x release flag.

FIG. 19 is a flowchart for controlling operation of the engine.

FIG. 20 is a flowchart for executing injection control I of the engine.

[Explanation of symbols]

 6 fuel injection valve 15 exhaust turbocharger 20 throttle valve 29 EGR passage 31 EGR control valve

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F02D 43/00 301 F02D 43/00 301G F02M 25/07 570 F02M 25/07 570J 570G (72) Inventor Ito Takewa 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Corporation (72) Inventor Yoshi ▲ saki ▼ Koji 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Corporation (72) Inventor Hiroki Murata Toyota, Aichi Prefecture No. 1 Toyota Town, Toyota Motor Corporation F-term (reference) 3G062 AA01 AA05 BA04 BA05 BA06 CA03 CA07 CA08 EA11 ED08 FA05 FA13 GA01 GA04 GA06 GA15 GA17 GA21 3G084 AA01 BA05 BA07 BA13 BA14 BA15 BA20 BA24 CA03 CA04 DA39 FA07 FA10 FA29 FA33 FA37 FA38 3G091 AA10 AA11 AA18 AB02 AB03 AB04 BA00 EA01 EA05 EA07 EA34 FA12 FA13 FA14 GB02W GB 03W GB04W GB05W GB10X HA36 3G301 HA02 HA11 HA13 JA37 KA07 KA08 KA09 LA00 LA03 MA11 MA18 ND01 PA01Z PB08A PB08Z PD03Z PD15Z PE01Z PE03Z PF03Z

Claims (9)

[Claims] 1. As the amount of inert gas supplied into the combustion chamber increases, the amount of soot generated gradually increases and reaches a peak, and the amount of inert gas supplied into the combustion chamber further increases. In an internal combustion engine where the temperature of the fuel and the surrounding gas during combustion in the combustion chamber becomes lower than the soot generation temperature and soot is hardly generated, the amount of generated soot is larger than the amount of inert gas at which the peak occurs. During the combustion in which the amount of active gas is supplied into the combustion chamber, the inert gas supplied into the combustion chamber after controlling the amount of air supplied into the combustion chamber to its target value during idling operation of the engine. An internal combustion engine in which the gas amount is controlled to the target value. 2. The method according to claim 1, wherein the amount of inert gas supplied into the combustion chamber is controlled to a target value, and then the amount of fuel injected into the combustion chamber is controlled to the target value. An internal combustion engine as described. 3. The fuel injection system according to claim 2, wherein the amount of fuel injected into the combustion chamber is controlled to a target value, and then the timing of fuel injection into the combustion chamber is controlled to the target value. Internal combustion engine. 4. The internal combustion engine according to claim 1, further comprising a recirculation device for recirculating exhaust gas discharged from the combustion chamber into the engine intake passage, wherein the inert gas comprises recirculated exhaust gas. 5. The internal combustion engine according to claim 4, wherein the exhaust gas recirculation rate is approximately 55% or more. 6. The internal combustion engine according to claim 1, wherein a catalyst having an oxidation function is disposed in the engine exhaust passage. 7. The catalyst according to claim 1, wherein said catalyst is an oxidation catalyst, a three-way catalyst or NO _x.
7. The internal combustion engine according to claim 6, comprising at least one of an absorbent. 8. The first combustion in which the amount of inert gas supplied into the combustion chamber is larger than the amount of inert gas at which the amount of generated soot is at a peak and little soot is generated, and the amount of generated soot is at a peak. 2. The internal combustion engine according to claim 1, further comprising a switching means for selectively switching between a second combustion in which the amount of inert gas supplied into the combustion chamber is smaller than an amount of inert gas. 9. An engine operating region is divided into a first operating region on a low load side and a second operating region on a high load side, and first combustion is performed in the first operating region. 9. The internal combustion engine according to claim 8, wherein the second combustion is performed in the region.