JP3331986B2 - Multi-cylinder internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art Conventionally, in an internal combustion engine, for example, a diesel engine, an engine exhaust passage and an engine intake passage are connected by an exhaust gas recirculation (hereinafter referred to as EGR) passage in order to suppress the generation of NOx. Exhaust gas, that is, EGR gas, is recirculated through the 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 decreases, the amount of generated NOx decreases. Therefore, the higher the EGR rate, the lower the amount of generated NOx.

As described above, it has been known that the amount of generated NOx can be reduced by 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
The amount of x and smoke was determined to be as small as possible. However, in this way EGR
Even if the rate is set so as to minimize the generation of NOx and smoke, there is a limit to the reduction of the generation of NOx and smoke, and in fact, a considerable amount of N
At present, Ox 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 to about 55% or more. It becomes almost zero. That is, it was found that soot was hardly generated. In this case, N
It has also been found that the amount of Ox generated is extremely small.
After that, the reason why no soot was generated was examined based on this finding, and as a result, unprecedented soot and NO
Thus, a new combustion system capable of simultaneously reducing x has been constructed. 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.

[0009]

However, a new combustion system as described above has not been disclosed yet. Therefore, the conventional combustion system already disclosed cannot exhibit new effects based on the new combustion system described above.

Accordingly, the present invention provides a method for controlling the torque generated in each cylinder when the first combustion is performed while simultaneously preventing soot (smoke) and NOx from being discharged from the internal combustion engine. It is an object of the present invention to provide an internal combustion engine that can prevent the generated torque of each cylinder from further fluctuating due to an increase or decrease in the fuel injection amount when the fluctuation occurs.

Further, the present invention also provides a cylinder in which the generated torque fluctuates to a small side when low-temperature combustion is performed while simultaneously preventing soot (smoke) and NOx from being discharged from the internal combustion engine. It is an object of the present invention to provide an internal combustion engine that can suppress the variation in the generated torque of each cylinder by increasing the generated torque of the cylinder or reducing the generated torque of a cylinder that has scattered on the side where the generated torque is large. .

[0012]

According to the first aspect of the present invention, as the amount of the inert gas supplied into the combustion chamber increases, the amount of soot generated gradually increases and reaches a peak. When the amount of the inert gas supplied into the combustion chamber is further increased, the temperature of the fuel and the surrounding gas during combustion in the combustion chamber becomes lower than the temperature at which soot is generated, so that soot is hardly generated. A 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 amount of generated soot becomes a peak and the amount of 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 having a peak amount, and correcting the variation in the fuel injection amount of each cylinder. Fuel injection amount correction means for performing And, when the first combustion is performed, a multi-cylinder internal combustion engine so as to prohibit to correct the variation of the fuel injection amount of each cylinder is provided.

According to the second aspect of the present invention, the fuel injection amount correcting means detects an engine angular speed in a stroke including an expansion stroke of each cylinder, and detects a fuel in each cylinder based on the detected engine angular speed. A multi-cylinder internal combustion engine according to claim 1, wherein the variation in the injection amount is corrected.

In the multi-cylinder internal combustion engine according to the first and second aspects, 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 becomes a peak, and soot is hardly generated. When the first combustion is performed, the correction of the variation in the fuel injection amount of each cylinder is prohibited. by the way,
The second combustion in which the amount of the inert gas supplied into the combustion chamber is smaller than the amount of the inert gas at which the generation amount of soot becomes a peak,
It takes place in a lean atmosphere with plenty of air. Therefore, when the second combustion is performed, if the fuel injection amount varies on the increasing side, the amount of fuel contributing to the combustion increases, and the generated torque increases. On the other hand, when the fuel injection amount varies on the decreasing side, the fuel amount contributing to combustion decreases, and the generated torque decreases. Therefore, when the variation of the fuel injection amount of each cylinder is corrected when the second combustion is performed, when the engine angular speed in the stroke including the expansion stroke of each cylinder fluctuates on the large side, that is, the generated torque is large. When the fuel injection amount varies, the fuel injection amount is reduced to correct the generated torque to a smaller side. On the other hand, when the engine angular velocity in the stroke including the expansion stroke of each cylinder fluctuates on the small side, that is, when the generated torque fluctuates on the small side, the fuel injection amount is increased to correct the generated torque on the large side. You. However, the first combustion is performed in an atmosphere where the air tends to be insufficient. For this reason, when the first combustion is performed, if the fuel injection amount varies on the increasing side, the air becomes more and more insufficient, so that the combustion deteriorates and the generated torque decreases. On the other hand, when the fuel injection amount varies on the decreasing side, the combustion is improved, and the generated torque increases. That is, between the time when the first combustion is performed and the time when the second combustion is performed, when the engine angular velocity in the stroke including the expansion stroke of each cylinder fluctuates to the small side or the large side, the fuel injection amount is increased. It should be the opposite of whether to perform the weight loss correction. Therefore, as described above, claims 1 and 2
In the multi-cylinder internal combustion engine described in (1), when the first combustion is performed, it is prohibited to correct the variation in the fuel injection amount of each cylinder. As a result, when the first combustion is performed and the engine angular velocity in the stroke including the expansion stroke of each cylinder fluctuates on the small side, that is, when the generated torque fluctuates on the small side, the fuel injection amount increases. The generated torque further varies due to the correction, and when the first combustion is performed and the generated torque varies to the larger side, the fuel injection amount is corrected to be reduced so that each cylinder is generated. Further variation in torque can be avoided. Here, the “stroke including the expansion stroke”
It refers to only the expansion stroke or the expansion stroke and the compression stroke adjacent thereto (the same applies hereinafter).

According to the third aspect of the present invention, as the amount of the inert gas supplied into the combustion chamber is increased, the amount of soot generated gradually increases and reaches a peak, and is supplied into the combustion chamber. When the amount of inert gas 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, and soot is hardly generated. and detecting the engine angular velocity in stroke including the expansion stroke of each cylinder, comprising a fuel injection amount correction means for correcting the variation of the fuel injection amount of each cylinder based on the detected engine angular velocity, the soot is hardly generated A multi-cylinder internal combustion engine is provided in which, when non-combustion is performed, a fuel injection amount of a cylinder having a small engine angular velocity is reduced.

In the multi-cylinder internal combustion engine according to the third aspect, 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 the soot is hardly generated. Is performed, the fuel injection amount of the cylinder having the low engine angular velocity is corrected to decrease. By the way, the combustion in which the soot is hardly generated is performed in an atmosphere where the air tends to be insufficient. Therefore, when the combustion in which the soot is hardly generated is performed, when the fuel injection amount is reduced, the shortage of air is slightly eliminated and the combustion is improved, and the generated torque, that is, the engine angular speed in the stroke including the expansion stroke increases. The phenomenon that it does. Therefore, as described above, in the multi-cylinder internal combustion engine according to the third aspect, when the combustion in which the soot is hardly generated is performed, the fuel injection amount of the cylinder having a low engine angular velocity is corrected to be reduced. As a result, when the combustion in which the soot is hardly generated is performed, it is possible to increase the generated torque of the cylinders that are scattered to the side where the generated torque is small, and to suppress the variation of the generated torque of each cylinder.

According to the fourth aspect of the present invention, as the amount of the inert gas supplied into the combustion chamber increases, the amount of soot generated gradually increases and reaches a peak, and is supplied to the combustion chamber. When the amount of inert gas 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, and soot is hardly generated. and detecting the engine angular velocity in stroke including the expansion stroke of each cylinder, comprising a fuel injection amount correction means for correcting the variation of the fuel injection amount of each cylinder based on the detected engine angular velocity, the soot is hardly generated There is provided a multi-cylinder internal combustion engine in which the fuel injection amount of a cylinder having a large engine angular velocity is increased and corrected when unburned combustion is performed.

In the multi-cylinder internal combustion engine according to the fourth aspect, 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 becomes a peak, and the soot is hardly generated. Is performed, the fuel injection amount of the cylinder having the higher engine angular velocity is increased and corrected. By the way, the combustion in which the soot is hardly generated is performed in an atmosphere where the air tends to be insufficient. Therefore, when the combustion in which the soot is hardly generated is performed, if the fuel injection amount is increased, the air becomes further insufficient and the combustion deteriorates, and the generated torque, that is, the engine angular velocity in the stroke including the expansion stroke, is reduced. Is seen to decrease. Therefore, as described above, in the multi-cylinder internal combustion engine according to the fourth aspect, when the combustion in which the soot is hardly generated is performed, the fuel injection amount of the cylinder having a high engine angular velocity is increased and corrected. As a result, when the combustion in which the soot is hardly generated is performed, the generated torque of the cylinders that vary to the side where the generated torque is large is reduced, and the variation in the generated torque of each cylinder can be suppressed.

According to the fifth aspect of the present invention, the engine angular velocity is obtained by detecting a time required for a part of a stroke including an expansion stroke of each cylinder. The multi-cylinder internal combustion engine according to the above is provided.

In the multi-cylinder internal combustion engine according to the fifth aspect, the engine angular velocity can be obtained by detecting the time required for a part of the stroke including the expansion stroke of each cylinder. That is,
The engine angular velocity is detected, for example, at the timing when the generated torque reaches a peak.

According to the present invention, the engine angular velocity is obtained by detecting a time required for the entire stroke including an expansion stroke of each cylinder. A multi-cylinder internal combustion engine as described is provided.

In the multi-cylinder internal combustion engine according to the sixth aspect, the engine angular velocity can be obtained by detecting the time required for the entire stroke including the expansion stroke of each cylinder.

According to the present invention, a catalyst having an oxidizing function is disposed in an engine exhaust passage for oxidizing unburned hydrocarbons discharged from the combustion chamber.
A multi-cylinder internal combustion engine according to any one of claims 3 and 4, is provided.

According to the invention described in claim 8, wherein the catalyst is an oxidation catalyst, a multi-cylinder internal combustion engine according to claim 7 comprising a single even without least of the three-way catalyst or NOx absorbent is provided.

In the multi-cylinder internal combustion engine according to the seventh and eighth aspects, the unburned hydrocarbon discharged from the combustion chamber is oxidized in the engine exhaust passage, so that the unburned hydrocarbon is discharged from the internal combustion engine. Can be prevented.

According to a ninth aspect of the present invention, there is provided an exhaust gas recirculation device for recirculating exhaust gas discharged from the combustion chamber into an engine intake passage, wherein the inert gas is supplied to the engine intake passage. A multi-cylinder internal combustion engine according to any one of claims 1, 3 and 4, comprising recirculated exhaust gas recirculated therein.

[0027] In the multi-cylinder internal combustion engine according to the ninth aspect, the recirculated exhaust gas that is recirculated into the engine intake passage by the exhaust gas recirculation device is used as an inert gas, so that the exhaust gas can be prevented from entering the combustion chamber from outside. The necessity of providing a special means for supplying the active gas can be avoided.

According to the tenth aspect of the present invention, the amount of recirculated exhaust gas supplied into the combustion chamber is larger than the amount of recirculated exhaust gas at which the amount of generated soot becomes a peak, and soot is hardly generated. Switching means for selectively switching between the first combustion and the second combustion in which the amount of recirculated exhaust gas supplied into the combustion chamber is smaller than the amount of recirculated exhaust gas at which the generation amount of soot is peaked; From the first combustion to the second
10. The multi-cylinder internal combustion engine according to claim 9, wherein the exhaust gas recirculation rate is changed stepwise when the combustion is switched to the first combustion or when the second combustion is switched to the first combustion.

[0029] In the multi-cylinder internal combustion engine according to the tenth aspect,
By changing the exhaust gas recirculation rate in a stepwise manner when switching from the first combustion to the second combustion or from the second combustion to the first combustion, the exhaust gas recirculation rate is reduced by the soot generation amount. Can be prevented from being set to the exhaust gas recirculation rate that peaks.

According to the eleventh aspect, when the exhaust gas recirculation rate during the first combustion is substantially 55% or more and the second combustion is performed. The multi-cylinder internal combustion engine according to claim 10, wherein an exhaust gas recirculation rate of the engine is approximately 50% or less.

[0031] In the multi-cylinder internal combustion engine according to the eleventh aspect,
By setting the exhaust gas recirculation rate when the first combustion is performed to approximately 55% or more and the exhaust gas recirculation rate when the second combustion is performed to approximately 50% or less, The exhaust gas recirculation rate can be prevented from being set to the exhaust gas recirculation rate at which the generation amount of soot becomes a peak.

According to the twelfth aspect of the invention, the operating range of the engine is set to the first operating range on the low load side and the second operating range on the high load side.
11. The multi-cylinder internal combustion engine according to claim 10, wherein the first combustion region is divided into the first combustion region and the second combustion region is performed in the second combustion region. 12. Is provided.

[0033] In the multi-cylinder internal combustion engine according to the twelfth aspect,
When the first combustion can be performed, that is, when the temperature of the fuel and the surrounding gas during the combustion in the combustion chamber can be maintained lower than the soot generation temperature, the engine has a relatively low calorific value due to the combustion. The first combustion is performed in the first operation region on the low load side and the second combustion is performed in the second operation region on the high load side because the operation is limited to the load operation. therefore,
Appropriate combustion can be performed according to the operation range.

[0034]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows a four-stroke compression ignition type 4 according to the present invention.
1 shows a first embodiment applied to a cylinder 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,
Reference numeral 6 denotes an electrically controlled fuel injection valve, 7 denotes an intake valve, 8 denotes an intake port, 9 denotes an exhaust valve, and 10 denotes an exhaust port. The intake port 8 is connected to the surge tank 1 via the corresponding intake branch 11.
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. An inlet of the compressor 16 is connected to an air cleaner 18 through an air suction pipe 17, and a throttle valve 2 driven by a step motor 19 is provided in the air suction pipe 17.
0 is placed. A mass flow detector 21 for detecting the mass flow of the intake air is disposed in the air suction pipe 17 upstream of the throttle valve 20.

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.

The exhaust pipe 28 connected to the outlet of the catalytic converter 26 and the air suction pipe 17 downstream of the throttle valve 20 are connected to each other via an exhaust gas recirculation (hereinafter referred to as EGR) passage 29, and are connected to the EGR passage. An EGR control valve 31 driven by a step motor 30 is arranged in the inside 29. 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 via a fuel supply pipe 33 to a fuel reservoir, a so-called common rail 34. 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 is connected to a read only memory (ROM) 42, a random access memory (RAM) 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. The engine speed is measured by the crank angle sensor 52.
Is calculated based on the output value of. Further, the input port 45
Is connected via an AD converter 47 to an acceleration sensor 60 which generates an output pulse every time the camshaft rotates 360 °. Crank angle sensor 52 and acceleration sensor 60
, An engine angular velocity in a stroke including an expansion stroke of each cylinder is detected. 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 30, and the fuel pump 35 via a corresponding drive circuit 48.

FIG. 2 shows the throttle valve 2 when the engine is under low load operation.
The graph shows changes in output torque and changes in smoke, HC, CO, and NOx emissions when the air-fuel ratio A / F (horizontal axis in FIG. 2) is changed by changing the opening degree and the EGR rate of 0. 7 shows an experimental example. 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 decreased by increasing the EGR rate, the smoke is reduced when the EGR rate becomes about 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 Ox is considerably reduced. On the other hand, at this time, HC,
The amount of generated CO starts to increase.

FIG. 3 (A) shows the change in the combustion pressure in the combustion chamber 5 when the air-fuel ratio A / F is around 21 and the amount of generated smoke is the largest. FIG. 3 (B) 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 (2), the generation amount of NOx is considerably reduced. N
The decrease in the amount of generated Ox means that the combustion temperature in the combustion chamber 5 has decreased. Therefore, it can be said that the combustion temperature in the combustion chamber 5 has decreased when little soot is generated. . 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.

Second, when the amount of generated smoke, that is, the amount of generated 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. .

These results based on the experimental results shown in FIGS. 2 and 3 are summarized as follows. When the combustion temperature in the combustion chamber 5 is low, the amount of generated soot 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 it cannot be said how many times the temperature changes, this certain temperature has a deep relationship with the amount of generated NOx. Therefore, this certain temperature can be defined to some extent from the amount of generated NOx. it can. That is, as the EGR rate increases, the temperature of the fuel during combustion and the gas temperature around it decrease, and the amount of generated NOx decreases. At this time, when the generation amount of NOx becomes about 10 p.pm or less, soot is hardly generated. Therefore, the above certain temperature is NO
The temperature 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 a catalyst having an oxidation function as described above, it is extremely difficult to discharge hydrocarbons from the combustion chamber 5 in the state of a precursor of soot or in the state before the soot or in the form of soot from the combustion chamber 5. There is a big 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.

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, the air separated from the fuel hardly absorbs the heat of combustion heat of the fuel. 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, when a fuel is present in a mixed gas of a large amount of inert gas and a small amount of air, the situation is slightly different.
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 the 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 strongly cooled, the amount of soot generation peaks at a position 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.
When the R gas is cooled slightly, the amount of soot generation peaks when the EGR rate is slightly higher than 50%,
In this case, if the EGR rate is set to about 65% or more, 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 is small, the EGR rate at which the amount of soot peaks slightly decreases, and almost all soot is generated. The lower limit of the EGR rate to be eliminated also slightly decreases. As described above, the lower limit of the EGR rate at which almost no soot is 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 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, and is 70% or more in the embodiment shown in FIG. That is, the total intake gas amount sucked into the combustion chamber 5 is represented by a solid line X in FIG. 6, and the ratio between the air amount and the EGR gas amount in the total intake gas amount X is as shown in FIG. The temperature of the fuel and the gas around it will be lower than the temperature at which soot is produced, so that no soot is generated. At this time, NOx
The amount generated is around 10 p.pm or less, and therefore the amount of NOx 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 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.

When the supercharging is not performed, the upper limit of the total intake gas amount X sucked into the combustion chamber 5 is Y. Therefore, in FIG. 6, the required load is larger in the region where the required load is larger than Lo. As the ratio increases, the air-fuel ratio cannot be maintained at the stoichiometric air-fuel ratio unless the EGR gas ratio is reduced. In other words, when the supercharging is not performed and the required air-fuel ratio is maintained at the stoichiometric air-fuel ratio in an area where the required load is larger than Lo, the EGR rate decreases as the required load increases, and In the region where the required load is larger than Lo, the temperature of the fuel and the surrounding gas cannot be maintained at a temperature lower than the temperature at which soot is generated.

However, as shown in FIG. 1, when the EGR gas is recirculated through the EGR passage 29 to the inlet side of the supercharger, that is, into the air suction pipe 17 of the exhaust turbocharger 15, the required load is larger than Lo. In EGR rate 5
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. When the EGR rate is set to 55% or more in a region where the required load is larger than Lo, E
The throttle valve 20 is opened when the GR control valve 31 is fully opened.
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 smaller than the air amount shown in FIG. 6, that is, the air-fuel ratio is made rich. Even so, while suppressing the generation of soot, the generation amount of NOx was reduced to 10 p.p.
m 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. Meanwhile, the amount of generated NOx can be reduced to about 10 p.pm or less.

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 to soot, thus producing soot. There is no. At this time, only a very small amount of NOx is 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, NOx
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. However, the generation amount of NOx 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 during combustion in the combustion chamber and the gas around it can be suppressed to a temperature lower than 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, during the low load operation in the engine, the first combustion, that is, the low-temperature combustion is performed by suppressing the temperature of the fuel during combustion and the gas around it to a temperature below the temperature at which the growth of hydrocarbons stops halfway. 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 performed normally in the past, is a 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 is peaked. Say that.

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 operation range from the first operation range I to the second operation range II is made based on the first boundary X (N), and the change from the second operation range II to the first operation range II is performed.
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 as follows. 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, but the unburned hydrocarbon is replaced by the precursor of soot or the state before it. It is discharged from the combustion chamber 5 in the form. At this time, the unburned hydrocarbon discharged from the combustion chamber 5 is oxidized well by the catalyst 25 having an oxidizing function.

As the catalyst 25, an oxidation catalyst, a three-way catalyst, or a NOx absorbent can be used. When the average air-fuel ratio in the combustion chamber 5 is lean, the NOx absorbent
And has the function of releasing NOx when the average air-fuel ratio in the combustion chamber 5 becomes rich. This NOx absorbent uses, for example, alumina as a carrier, and has, for example, potassium K, sodium Na, lithium Li, cesium Cs
Alkali metals such as barium Ba, calcium Ca
Alkaline earth, lanthanum La, yttrium Y
And at least one selected from rare earths such as
And a noble metal such as

In addition to the oxidation catalyst, the three-way catalyst and the NO
The x absorbent also has an oxidizing function, and thus the three-way catalyst and the NOx absorbent can be used as the catalyst 25 as described above.

FIG. 8 shows the output of the air-fuel ratio sensor 27. 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 idle operation, the throttle valve 2
0 is closed to almost fully closed, and at this time, the EGR control valve 31
Is also closed to near full closure. When the throttle valve 20 is closed close to the fully closed state, 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, during idling operation, the throttle valve 2
0 is closed until it is almost fully closed.

On the other hand, the operating region of the engine is the first operating region 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 operation 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,
Each curve represented by A / F = 18 has a target air-fuel ratio of 1
5.5, 16, 17, and 18, and the air-fuel ratio between the curves is determined by proportional distribution. FIG.
As shown in (A), the air-fuel ratio is lean in the first operating region I, and in the first operating region I, the target air-fuel ratio A / F becomes leaner as the required load L decreases.

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. Target air-fuel ratio A /
As F increases, the fuel consumption rate increases. Accordingly, in order to make the air-fuel ratio as lean as possible, in the embodiment according to the present invention, the target air-fuel ratio A / F is increased as the required load L decreases.

The target air-fuel ratio A / F shown in FIG. 10A is stored in advance in a ROM 4 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.

FIG. 12A shows the target air-fuel ratio A when the second combustion, that is, ordinary combustion by the conventional combustion method is performed.
/ F. Note that A / F in FIG.
= 24, A / F = 35, A / F = 45, and A / F = 60 indicate target air-fuel ratios of 24, 35, 45, and 6, respectively.
0 is shown. The target air-fuel ratio A shown in FIG.
/ F is a function of the required load L and the engine speed N as shown in FIG.
Is stored within. Also, the throttle valve 20 required to set the air-fuel ratio to the target air-fuel ratio A / F shown in FIG.
The target opening ST 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.
As shown in FIG. 13 (B), the target opening degree SE of the EGR control valve 31 required to obtain the target air-fuel ratio A / F shown in FIG. It is stored in the ROM 42.

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 in the form of a map as a function of the required load L and the engine speed N as shown in FIG.

Hereinafter, the operation control of this embodiment will be described. Before describing the operation control of the present embodiment, the relationship between the air-fuel ratio and the generated torque will be described. FIG. 15 is a graph showing the relationship between the air-fuel ratio and the generated torque (engine angular speed). In FIG. 15, the horizontal axis indicates the air-fuel ratio A / F, and the vertical axis indicates the generated torque T (engine angular speed).
As shown in FIG. 15, the second combustion (combustion by the conventional combustion method) is performed in a region where the air-fuel ratio in which air is sufficiently left is relatively lean. Therefore, when the second combustion is performed, if the fuel injection amount is corrected to decrease, that is, the air-fuel ratio is changed from A / F ₃ to A / F ₃ in accordance with the correction of the decrease in fuel injection amount.
Increases F ₄ and (becomes lean), the generated torque with that contribute fuel quantity to the combustion is reduced is reduced by [Delta] T _2. On the other hand, low-temperature combustion (first combustion) is performed in a region where the air tends to be insufficient and the air-fuel ratio is richer than in the case of the second combustion. Therefore, when low-temperature combustion is performed,
When the amount of fuel injection is corrected to increase, that is, the air-fuel ratio with the increasing correction of the fuel injection amount is decreased from A / F ₁ to A / F ₂ and (becomes rich) air even more scant As a result, combustion deteriorates and the generated torque decreases by ΔT ₁ .

Next, the operation control of this embodiment will be described with reference to FIGS. Referring to FIGS. 16 to 18, first, in step 100, the times T ₁ and 3 required for the stroke including the expansion stroke of the first cylinder obtained by executing the TDC 180 ° CA interrupt routine shown in FIG. The time T ₂ required for the stroke including the expansion stroke of the No. 4 cylinder, the time T required for the stroke including the expansion stroke of the No. 4 cylinder
Time T ₄ required for the stroke including the expansion stroke of the _third and second cylinders
Is read.

FIG. 19 shows TDC 180 ° CA for detecting variation in fuel injection amount between cylinders of the internal combustion engine according to the present embodiment.
9 is a flowchart illustrating an interrupt routine. This routine is performed at the top dead center 180 ° crank angle (TDC1
(80 ° CA). FIG.
As shown in FIG. 9, when this routine is started, first, in step 1900, the crank angle sensor 52 and the acceleration sensor 60 determine which cylinder is currently in a stroke including the expansion stroke, Update the number i. Since the internal combustion engine of the present embodiment performs the expansion stroke in the order of the first cylinder, the third cylinder, the fourth cylinder, and the second cylinder,
When it is determined that the cylinder in the stroke including the current expansion stroke is the first cylinder, the cylinder number i is set to 1 (i ← 1), and
When it is determined that the cylinder in the stroke including the current expansion stroke is the third cylinder, the cylinder number i is set to 2 (i ← 2), and
When it is determined that the cylinder in the stroke including the current expansion stroke is the fourth cylinder, the cylinder number i is set to 3 (i ← 3),
When it is determined that the cylinder in the stroke including the current expansion stroke is the second cylinder, the cylinder number i is set to 4 (i ←
4).

Next, at step 1901, the time TIMER required for the stroke including the expansion stroke calculated based on the output signal of the crank angle sensor 52 is set to the time Ti required for the stroke including the expansion stroke of the i-th cylinder. (Ti ← TIM
ER). Next, at 1902, TIMER is reset, and preparations are made to measure the time required for a stroke including the next cylinder expansion stroke.

That is, when this routine is executed for the first time, for example, if the time T ₁ required for a stroke including the expansion stroke of the first cylinder is obtained, the next time this routine is executed, 3
Ban time T ₂ required for the process, including an expansion stroke of the cylinder is obtained, then the time T ₃ required for stroke, including an expansion stroke of the fourth cylinder when executing this routine obtained, then executes this routine at time T ₄ required for stroke, including an expansion stroke of the second cylinder is obtained.

In the present embodiment, the engine angular velocity in the stroke including the expansion stroke of each cylinder is obtained by detecting the time Ti required for the entire stroke including the expansion stroke of each cylinder. In the embodiment, the engine angular velocity in the stroke including the expansion stroke of each cylinder may be obtained by detecting the time required for a part of the stroke including the expansion stroke of each cylinder.

Returning to the description of FIGS. 16 to 18, next, at step 101, the average time Tave (= (T ₁ + T) which is the average of the time required for the stroke including the expansion stroke of each cylinder.
_{2 + T 3 + T 4)} / 4) is calculated. Next, at step 102, 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 10
Proceeding to 3, it is determined whether or not the required load L has become larger than the first boundary X1 (N). When L ≦ X1 (N), the routine proceeds to step 107, where low-temperature combustion is performed.

When it is determined in step 103 that L> X (N), the routine proceeds to step 104, where the flag I is reset, and then proceeds to step 112 where the second combustion is performed.

On the other hand, when it is determined in step 102 that the flag I is not set, that is, when the operating state of the engine is in the second operating region II, step 105
It is determined whether the required load L has become lower than the second boundary Y (N). When L ≧ Y (N), the routine proceeds to step 112, where the second combustion is performed under a lean air-fuel ratio.

On the other hand, at step 105, L <Y
When it is determined that (N) has been reached, the routine proceeds to step 106, where the flag I is set, and then proceeds to step 107 to perform low-temperature combustion.

In step 107, the target opening ST of the throttle valve 20 is calculated from the map shown in FIG.
The opening of the throttle valve 20 is set to the target opening ST.
Next, at step 108, the target opening SE of the EGR control valve 31 is calculated from the map shown in FIG.
The opening of the control valve 31 is set as the target opening SE. Next, at step 109, the mass flow rate of the intake air detected by the mass flow rate detector 21 (hereinafter, simply referred to as the intake air amount).
Ga is captured, and then in step 110 FIG.
The target air-fuel ratio A / F is calculated from the map shown in FIG. Next, at step 111, the fuel injection amount Q required for setting the air-fuel ratio to the target air-fuel ratio A / F is calculated based on the intake air amount Ga and the target air-fuel ratio A / F, and this routine ends. That is, when low-temperature combustion is performed, it is prohibited to correct the variation in the fuel injection amount Q of each cylinder.

When the required load L or the engine speed N changes during the low-temperature combustion, the opening of the throttle valve 20 and the opening of the EGR control valve 31 immediately change to the required load L and the engine speed N. Target opening ST according to
Matched to SE. Therefore, for example, when the required load L is increased, the amount of air in the combustion chamber 5 is immediately increased, and the generated torque of the engine is immediately increased.

On the other hand, the opening degree of the throttle valve 20 or the EGR
When the opening degree of the control valve 31 changes and the intake air amount changes, the change in the intake air amount Ga is detected by the mass flow rate detector 21, and the fuel injection amount Q is controlled based on the detected intake air amount Ga. Is done. That is, the fuel injection amount Q is changed after the intake air amount Ga actually changes.

In step 112, the target fuel injection amount Q is calculated from the map shown in FIG. 14, and the fuel injection amount is set as the target fuel injection amount Q. Next, in step 113, the time T ₁ required for the stroke including the expansion stroke of the first cylinder, the time T ₂ required for the stroke including the expansion stroke of the third cylinder, and the time required for the stroke including the expansion stroke of the fourth cylinder T ₃
And all the time required for stroke T ₄ including an expansion stroke of the second cylinder is whether equal to the average time Tave is determined. If YES, the variation correction of the fuel injection amount Q at the time of the second combustion is not executed, and the process proceeds to step 115 as it is. On the other hand, when NO, that is, the time T ₁ required for the stroke including the expansion stroke of the first cylinder, the time T ₂ required for the stroke including the expansion stroke of the third cylinder, and the stroke T including the expansion stroke of the fourth cylinder at least one average time period required for stroke, including an expansion stroke of the amount of time spent T ₃ and the second cylinder T ₄ Tav
If it is different from e, the routine proceeds to step 114, where the variation correction of the fuel injection amount Q during the second combustion is executed.

FIG. 20 is a flow chart showing a routine for executing a variation correction of the fuel injection amount Q during the second combustion. As shown in FIG. 20, when this routine is started,
First, in step 2000, it is determined whether or not the time Ti required for a stroke including the expansion stroke of each cylinder is longer than the average time Tave. When YES, it is determined that the generated torque varies to the small side because the fuel injection amount Q of the cylinder varies to the small side, and therefore, it is determined that the time required for the stroke including the expansion stroke is long. Proceed to. In step 2001, the fuel injection amount Q is increased and corrected to increase the generated torque of this cylinder (Q ← Q + ΔQ1). On the other hand, in the case of NO, it is determined that the fuel injection amount Q of this cylinder varies to a large side, and the generated torque varies to a large side, and therefore, it is determined that the time required for the stroke including the expansion stroke is short, Proceed to step 2002. In step 2002, the fuel injection amount Q is corrected to reduce the generated torque of the cylinder (Q ← Q−ΔQ1). Although not shown, the above-described variation correction execution routine of the fuel injection amount Q at the time of the second combustion is performed for all of the first, third, fourth, and second cylinders.

Returning to the description of FIGS. 16 to 18, next, at step 115, the target opening ST of the throttle valve 20 is calculated from the map shown in FIG. Next, at step 116, the target opening SE of the EGR control valve 31 is calculated from the map shown in FIG. 13B, and the opening of the EGR control valve 31 is set as the target opening SE.

Next, at step 117, the intake air amount Ga detected by the mass flow detector 21 is taken. Next, at step 118, the fuel injection amount Q and the intake air amount Ga
From this, the actual air-fuel ratio (A / F) _R is calculated. Next, at step 119, the target air-fuel ratio A / F is calculated from the map shown in FIG. Next, at step 120, it is determined whether or not the actual air-fuel ratio (A / F) _R is larger than the target air-fuel ratio A / F. (A / F) If _R > A / F, the routine proceeds to step 121, where the throttle opening correction value ΔS
T is reduced by a constant value α, then step 12
Proceed to 3. On the other hand, when (A / F) _R ≤A / F, the routine proceeds to step 122, where the correction value ΔST is increased by a constant value α, and then the routine proceeds to step 123. In step 123, the final target opening ST is calculated by adding the correction value ΔST to the target opening ST of the throttle valve 20, and the opening of the throttle valve 20 is set as the final target opening ST. That is, the opening of the throttle valve 20 is controlled so that the actual air-fuel ratio (A / F) _R becomes the target air-fuel ratio A / F.

When the required load L or the engine speed N changes during the second combustion, the fuel injection amount immediately matches the target fuel injection amount Q corresponding to the required load L and the engine speed N. I'm sullen. For example, the required load L
Is increased, the fuel injection amount is immediately increased, and thus the generated torque of the engine is immediately increased.

On the other hand, when the fuel injection amount Q is increased and the air-fuel ratio deviates from the target air-fuel ratio A / F, the opening of the throttle valve 20 is controlled so that the air-fuel ratio becomes the target air-fuel ratio A / F. That is, the air-fuel ratio is changed after the fuel injection amount Q changes.

In the embodiments described above, the fuel injection amount Q is controlled by open loop when low-temperature combustion is being performed, and the air-fuel ratio is controlled by the opening degree of the throttle valve 20 when the second combustion is being performed. It is controlled by changing.
However, the fuel injection amount Q can be feedback-controlled based on the output signal of the air-fuel ratio sensor 27 when the low-temperature combustion is being performed, and the air-fuel ratio can be controlled by the EGR control when the second combustion is being performed. The control can also be performed by changing the opening of the valve 31.

As described with reference to FIG. 15, since the second combustion is performed in a lean atmosphere having a sufficient amount of air, the fuel injection amount increases when the second combustion is performed. If it varies to the side, the amount of fuel contributing to combustion increases, and the generated torque increases. On the other hand, when the fuel injection amount varies on the decreasing side, the fuel amount contributing to combustion decreases, and the generated torque decreases. Therefore, as described above, step 11 in FIG.
In 4, when the variation of the fuel injection amount of each cylinder is corrected when the second combustion is performed, when the engine angular speed in the stroke including the expansion stroke of each cylinder fluctuates on the large side, that is, when the generated torque is When it scatters on the big side,
In order to correct the generated torque to a smaller side, the fuel injection amount is reduced and corrected. On the other hand, when the engine angular velocity in the stroke including the expansion stroke of each cylinder fluctuates on the small side, that is, when the generated torque fluctuates on the small side, the fuel injection amount is increased to correct the generated torque on the large side. You.

On the other hand, as described with reference to FIG. 15, since the low-temperature combustion is performed in an atmosphere where the air tends to be insufficient, when the low-temperature combustion is performed, if the fuel injection amount fluctuates to the increasing side, Since the air tends to be further insufficient, the combustion deteriorates and the generated torque decreases. On the other hand, when the fuel injection amount varies on the decreasing side, the combustion is improved, and the generated torque increases. That is, when the low-temperature combustion is performed and when the second combustion is performed, when the engine angular velocity in the stroke including the expansion stroke of each cylinder fluctuates to the small side or the large side,
Whether the fuel injection amount should be increased or decreased should be corrected. Therefore, in the present embodiment, when the low-temperature combustion is performed as described above, the correction of the variation in the fuel injection amount of each cylinder is prohibited. As a result, when low-temperature combustion is performed and the engine angular velocity in the stroke including the expansion stroke of each cylinder fluctuates on the small side, that is, when the generated torque fluctuates on the small side, the fuel injection amount is increased and corrected. As a result, the generated torque further fluctuates, and when the first combustion is performed and the generated torque fluctuates on the larger side, the generated torque further fluctuates due to the decrease in the fuel injection amount. Can be avoided.

Hereinafter, a second embodiment of the multi-cylinder internal combustion engine of the present invention will be described. The configuration of this embodiment is almost the same as the configuration of the first embodiment shown in FIG. FIG. 21 to FIG.
The operation control of the present embodiment will be described with reference to FIG. Referring to FIGS. 21 to 23, first, in step 100, the time T ₁ , 3 required for the stroke including the expansion stroke of the first cylinder obtained by executing the TDC 180 ° CA interrupt routine shown in FIG. The time T ₂ required for the stroke including the expansion stroke of the No. 4 cylinder, the time T ₃ required for the stroke including the expansion stroke of the No. 4 cylinder, and the time T ₄ required for the stroke including the expansion stroke of the No. 2 cylinder are read.

Note that, as in the first embodiment, in this embodiment, the time T required for the entire stroke including the expansion stroke of each cylinder is taken.
By detecting i, the engine angular velocity in the stroke including the expansion stroke of each cylinder is obtained, but in other embodiments,
By detecting the time required for a part of the stroke including the expansion stroke of each cylinder, the engine angular velocity in the stroke including the expansion stroke of each cylinder may be obtained.

Returning to the description of FIGS. 21 to 23, next, at step 101, the average time Tave (= (T ₁ + T) which is the average of the time required for the stroke including the expansion stroke of each cylinder.
_{2 + T 3 + T 4)} / 4) is calculated. Next, at step 102, 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 10
Proceeding to 3, it is determined whether or not the required load L has become larger than the first boundary X1 (N). When L ≦ X1 (N), the routine proceeds to step 107, where low-temperature combustion is performed.

When it is determined in step 103 that L> X (N), the routine proceeds to step 104, where the flag I is reset. Then, the routine proceeds to step 112, where the second combustion is performed.

On the other hand, when it is determined in step 102 that the flag I is not set, that is, when the operating state of the engine is in the second operating region II, step 105
It is determined whether the required load L has become lower than the second boundary Y (N). When L ≧ Y (N), the routine proceeds to step 112, where the second combustion is performed under a lean air-fuel ratio.

On the other hand, at step 105, L <Y
When it is determined that (N) has been reached, the routine proceeds to step 106, where the flag I is set, and then proceeds to step 107 to perform low-temperature combustion.

In step 107, the target opening ST of the throttle valve 20 is calculated from the map shown in FIG.
The opening of the throttle valve 20 is set to the target opening ST.
Next, at step 108, the target opening SE of the EGR control valve 31 is calculated from the map shown in FIG.
The opening of the control valve 31 is set as the target opening SE. Next, at step 109, the mass flow rate of the intake air detected by the mass flow rate detector 21 (hereinafter, simply referred to as the intake air amount).
Ga is captured, and then in step 110 FIG.
The target air-fuel ratio A / F is calculated from the map shown in FIG. Next, at step 111, a fuel injection amount Q necessary for setting the air-fuel ratio to the target air-fuel ratio A / F is calculated based on the intake air amount Ga and the target air-fuel ratio A / F.

Next, at step 2200, the first cylinder
Time T required for the stroke including the expansion stroke ₁3rd cylinder expansion
Time T required for the process including the process_Two4th cylinder expansion stroke
Time T required for the process including_ThreeAnd the expansion stroke of cylinder 2
Time T required for the process including_FourIs the average time Tave
It is determined whether it is equal to or not. If yes, low temperature
The variation correction of the fuel injection amount Q during combustion is not executed,
This routine is terminated as it is. On the other hand, when NO,
Time T required for the stroke including the expansion stroke of the first cylinder₁,
Time T required for the stroke including the expansion stroke of the third cylinder_Two4th
Time T required for a stroke including a cylinder expansion stroke_ThreeAnd second
Time T required for the stroke including the cylinder expansion stroke _FourAnd
If one of them is different from the average time Tave,
Proceeding to 2201, variation in the fuel injection amount Q during low-temperature combustion
Correction is performed.

FIG. 24 is a flow chart showing a routine for executing variation correction of the fuel injection amount Q during low temperature combustion.
As shown in FIG. 24, when this routine is started, first, in step 2000, it is determined whether or not the time Ti required for the stroke including the expansion stroke of each cylinder is longer than the average time Tave. When YES, it is determined that the generated torque varies to the small side because the fuel injection amount Q of the cylinder varies to the large side, and it is determined that the time required for the stroke including the expansion stroke is long, and step 240
Proceed to 1. In step 2401, the fuel injection amount Q is reduced and corrected to increase the generated torque of the cylinder (Q ← Q
-ΔQ2). On the other hand, in the case of NO, it is determined that the fuel injection amount Q of this cylinder varies to a small side and the generated torque varies to a large side, and therefore, it is determined that the time required for the stroke including the expansion stroke is short, Step 24
Go to 02. In step 2402, the fuel injection amount Q is increased and corrected to reduce the generated torque of this cylinder (Q ←
Q + ΔQ2). Although not shown, the above-described variation correction execution routine of the fuel injection amount Q at the time of low-temperature combustion is 1
This is performed for all cylinders of the No. 3 cylinder, the No. 3 cylinder, the No. 4 cylinder, and the No. 2 cylinder.

When the required load L or the engine speed N changes during the low-temperature combustion, the opening of the throttle valve 20 and the opening of the EGR control valve 31 immediately change to the required load L and the engine speed N. Target opening ST according to
Matched to SE. Therefore, for example, when the required load L is increased, the amount of air in the combustion chamber 5 is immediately increased, and the generated torque of the engine is immediately increased.

On the other hand, the opening degree of the throttle valve 20 or EGR
When the opening degree of the control valve 31 changes and the intake air amount changes, the change in the intake air amount Ga is detected by the mass flow rate detector 21, and the fuel injection amount Q is controlled based on the detected intake air amount Ga. Is done. That is, the fuel injection amount Q is changed after the intake air amount Ga actually changes.

In step 112, the target fuel injection amount Q is calculated from the map shown in FIG. 14, and the fuel injection amount is set as the target fuel injection amount Q. Next, in step 113, the time T ₁ required for the stroke including the expansion stroke of the first cylinder, the time T ₂ required for the stroke including the expansion stroke of the third cylinder, and the time required for the stroke including the expansion stroke of the fourth cylinder T ₃
And all the time required for stroke T ₄ including an expansion stroke of the second cylinder is whether equal to the average time Tave is determined. If YES, the variation correction of the fuel injection amount Q at the time of the second combustion is not executed, and the process proceeds to step 115 as it is. On the other hand, when NO, that is, the time T ₁ required for the stroke including the expansion stroke of the first cylinder, the time T ₂ required for the stroke including the expansion stroke of the third cylinder, and the stroke T including the expansion stroke of the fourth cylinder at least one average time period required for stroke, including an expansion stroke of the amount of time spent T ₃ and the second cylinder T ₄ Tav
If e is different from e, the routine proceeds to step 114, where the variation correction of the fuel injection amount Q during the second combustion is executed by the routine for executing the variation correction of the fuel injection amount Q during the second combustion shown in FIG.

Next, at step 115, the target opening ST of the throttle valve 20 is calculated from the map shown in FIG. Next, at step 116, the target opening SE of the EGR control valve 31 is calculated from the map shown in FIG. 13B, and the opening of the EGR control valve 31 is set as the target opening SE.

Next, at step 117, the intake air amount Ga detected by the mass flow detector 21 is taken. Next, at step 118, the fuel injection amount Q and the intake air amount Ga
From this, the actual air-fuel ratio (A / F) _R is calculated. Next, at step 119, the target air-fuel ratio A / F is calculated from the map shown in FIG. Next, at step 120, it is determined whether or not the actual air-fuel ratio (A / F) _R is larger than the target air-fuel ratio A / F. (A / F) If _R > A / F, the routine proceeds to step 121, where the throttle opening correction value ΔS
T is reduced by a constant value α, then step 12
Proceed to 3. On the other hand, when (A / F) _R ≤A / F, the routine proceeds to step 122, where the correction value ΔST is increased by a constant value α, and then the routine proceeds to step 123. In step 123, the final target opening ST is calculated by adding the correction value ΔST to the target opening ST of the throttle valve 20, and the opening of the throttle valve 20 is set as the final target opening ST. That is, the opening of the throttle valve 20 is controlled so that the actual air-fuel ratio (A / F) _R becomes the target air-fuel ratio A / F.

As described above, when the required load L or the engine speed N changes during the second combustion, the fuel injection amount immediately matches the target fuel injection amount Q corresponding to the required load L and the engine speed N. I'm sullen. For example, the required load L
Is increased, the fuel injection amount is immediately increased, and thus the generated torque of the engine is immediately increased.

On the other hand, when the fuel injection amount Q is increased and the air-fuel ratio deviates from the target air-fuel ratio A / F, the opening of the throttle valve 20 is controlled so that the air-fuel ratio becomes the target air-fuel ratio A / F. That is, the air-fuel ratio is changed after the fuel injection amount Q changes.

In the embodiments described above, the fuel injection amount Q is controlled by open loop when low-temperature combustion is performed, and the air-fuel ratio is controlled by the opening degree of the throttle valve 20 when the second combustion is performed. It is controlled by changing.
However, the fuel injection amount Q can be feedback-controlled based on the output signal of the air-fuel ratio sensor 27 when the low-temperature combustion is being performed, and the air-fuel ratio can be controlled by the EGR control when the second combustion is being performed. The control can also be performed by changing the opening of the valve 31.

As described with reference to FIG. 15, since the low-temperature combustion is performed in an atmosphere where the air tends to be insufficient, if the fuel injection amount is reduced at the time of the low-temperature combustion, the shortage of the air is slightly increased. The phenomenon that the combustion is improved by being eliminated and the generated torque, that is, the engine angular velocity in the stroke including the expansion stroke is increased. Therefore, in the present embodiment, as described above, in step 2401, when low-temperature combustion is performed, the fuel injection amount of the cylinder having a low engine angular velocity is corrected to be reduced. As a result, when low-temperature combustion is performed, it is possible to increase the generated torque of the cylinders that have scattered on the side where the generated torque is small, and to suppress the fluctuation of the generated torque.

As described with reference to FIG.
Since the low-temperature combustion is performed in an atmosphere where the air tends to be insufficient, when the low-temperature combustion is performed, if the fuel injection amount is increased, the air becomes further insufficient and the combustion deteriorates,
The phenomenon that the generated torque, that is, the engine angular velocity in the stroke including the expansion stroke, is reduced. Therefore, in the present embodiment, as described above, in step 2402, when low-temperature combustion is performed, the fuel injection amount of the cylinder having a high engine angular velocity is increased and corrected. As a result, when low-temperature combustion is performed, it is possible to reduce the generated torque of the cylinders that fluctuate to the side where the generated torque is large, and to suppress the fluctuation of the generated torque.

[0124]

According to the first and second aspects of the present invention,
Emission of soot (smoke) from the internal combustion engine and NO
x is simultaneously prevented from being discharged, and when the first combustion is performed and the generated torque of each cylinder varies, the generated torque of each cylinder is corrected by increasing or decreasing the fuel injection amount. Can be further prevented from varying.

According to the third aspect of the present invention, when low-temperature combustion is performed while simultaneously preventing soot (smoke) and NOx from being discharged from the internal combustion engine, the generated torque is small. By increasing the generated torque of the cylinders scattered on the side, variations in the generated torque of each cylinder can be suppressed.

According to the fourth aspect of the present invention, when low-temperature combustion is performed while simultaneously preventing the emission of soot and NOx from the internal combustion engine, the generated torque is large. By reducing the generated torque of the cylinders scattered on the side, it is possible to suppress variations in the generated torque of each cylinder.

According to the fifth and sixth aspects of the present invention, the engine angular velocity can be obtained by detecting the time required for part or all of the stroke including the expansion stroke of each cylinder as necessary.

According to the seventh and eighth aspects of the present invention, it is possible to prevent unburned hydrocarbons from being discharged from the internal combustion engine.

According to the ninth aspect of the present invention, it is possible to avoid the necessity of providing a special means for supplying an inert gas from the outside into the combustion chamber.

According to the tenth and eleventh aspects of the present invention, it is possible to prevent the exhaust gas recirculation rate from being set to the exhaust gas recirculation rate at which the amount of generated soot reaches a peak.

According to the twelfth aspect, appropriate combustion can be performed according to the operating range.

[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 NOx generated;

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 diagram 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 an air-fuel ratio and the like in a second combustion.

FIG. 13 is a view showing a map of a target opening degree of a throttle valve and the like.

FIG. 14 is a diagram showing a map of a fuel injection amount.

FIG. 15 is a graph showing the relationship between the air-fuel ratio and the generated torque.

FIG. 16 is a flowchart for controlling the operation of the engine of the first embodiment.

FIG. 17 is a flowchart for controlling the operation of the engine of the first embodiment.

FIG. 18 is a flowchart for controlling operation of the engine of the first embodiment.

FIG. 19 is a flowchart showing a TDC 180 ° CA interrupt routine.

FIG. 20 is a flowchart showing a routine for executing a variation correction of the fuel injection amount during the second combustion.

FIG. 21 is a flowchart for controlling the operation of the engine of the second embodiment.

FIG. 22 is a flowchart for controlling operation of the engine of the second embodiment.

FIG. 23 is a flowchart for controlling the operation of the engine of the second embodiment.

FIG. 24 is a flowchart illustrating a fuel injection amount variation correction execution routine during low-temperature combustion.

[Explanation of symbols]

 5: Combustion chamber 6: Fuel injection valve 29: EGR passage 31: EGR control valve 52: Crank angle sensor 60: Acceleration sensor

──────────────────────────────────────────────────の Continuation of front page (51) Int.Cl. ⁷ Identification code FI F02D 41/04 F02D 41/04 380J 43/00 301 43/00 301H 301N 45/00 301 45/00 301F F02M 25/07 570 F02M 25/07 570J (72) Inventor Takekazu Ito 1 Toyota Town, Toyota City, Aichi Pref. Inspector, Toyota Motor Corporation Examiner Satoshi Murakami (56) References JP-A-7-4287 (JP, A) JP-A-86251 (JP, A) JP-A-8-177651 (JP, A) JP-A-9-287527 (JP, A) JP-A-9-287528 (JP, A) JP-A-1-271634 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) F02D 41/00-45/00 F02M 25/07

Claims (12)

(57) [Claims] 1. As the amount of inert gas supplied to the combustion chamber increases, the amount of generated soot gradually increases and reaches a peak, and the amount of inert gas supplied to the combustion chamber further increases. As a result, the temperature of the fuel during combustion in the combustion chamber and the surrounding gas temperature become lower than the temperature at which soot is generated, and soot is hardly generated, so that the amount of soot generation reaches a peak. First combustion in which the amount of inert gas supplied into the combustion chamber is larger than the amount of inert gas and soot is hardly generated, Switching means for selectively switching between the second combustion in which the amount of inert gas supplied to the cylinder is small, and fuel injection amount correction means for correcting a variation in the fuel injection amount of each cylinder. When the combustion of No. 1 is performed, the fuel of each cylinder A multi-cylinder internal combustion engine that prohibits correction of variations in fuel injection amount. 2. The fuel injection amount correcting means detects an engine angular speed in a stroke including an expansion stroke of each cylinder, and corrects a variation in a fuel injection amount of each cylinder based on the detected engine angular speed. 2. The multi-cylinder internal combustion engine according to 1. 3. 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. A multi-cylinder internal combustion engine in which the temperature of fuel and the surrounding gas during combustion in the combustion chamber becomes lower than the soot generation temperature and soot is hardly generated , and includes a stroke including an expansion stroke of each cylinder. The engine angular velocity at
Fuel injection amount correction means for correcting the variation of the fuel injection amount of each cylinder based on the detected engine angular velocity,
A multi-cylinder internal combustion engine in which a fuel injection amount of a cylinder having a small engine angular velocity is corrected to be reduced when combustion is performed in which little soot is generated. 4. As the amount of inert gas supplied to the combustion chamber increases, the amount of soot generated gradually increases and reaches a peak, and the amount of inert gas supplied to the combustion chamber further increases. A multi-cylinder internal combustion engine in which the temperature of fuel and the surrounding gas during combustion in the combustion chamber becomes lower than the soot generation temperature and soot is hardly generated , and includes a stroke including an expansion stroke of each cylinder. The engine angular velocity at
Fuel injection amount correction means for correcting the variation of the fuel injection amount of each cylinder based on the detected engine angular velocity,
A multi-cylinder internal combustion engine in which the fuel injection amount of a cylinder having a high engine angular velocity is increased and corrected when combustion is performed in which little soot is generated. 5. The multi-cylinder internal combustion engine according to claim 2, wherein the engine angular velocity is obtained by detecting a time required for a part of a stroke including an expansion stroke of each cylinder. 6. The multi-cylinder internal combustion engine according to claim 2, wherein the engine angular velocity is obtained by detecting a time required for the entire stroke including an expansion stroke of each cylinder. 7. The multi-purpose catalyst according to claim 1, wherein a catalyst having an oxidizing function is disposed in an engine exhaust passage for oxidizing unburned hydrocarbons discharged from the combustion chamber. Cylinder internal combustion engine. 8. The catalyst according to claim 1, wherein the catalyst is an oxidation catalyst, a three-way catalyst or NO.
multi-cylinder internal combustion engine according to claim 7 comprising a single even without less of x absorbent. 9. An exhaust gas recirculation device for recirculating exhaust gas discharged from the combustion chamber into an engine intake passage, wherein the inert gas is recirculated into the engine intake passage. The multi-cylinder internal combustion engine according to any one of claims 1, 3 and 4, comprising a gas. 10. The first combustion in which the amount of recirculated exhaust gas supplied to the combustion chamber is larger than the amount of recirculated exhaust gas at which the amount of generated soot becomes a peak, and soot is hardly generated, and the generation of soot. A second amount of the recirculated exhaust gas supplied into the combustion chamber is smaller than an amount of the recirculated exhaust gas having a peak amount;
Switching means for selectively switching between the first combustion and the second combustion or when the second combustion is switched to the first combustion. 10. The multi-cylinder internal combustion engine according to claim 9, wherein the internal combustion engine is changed in a shape. 11. The exhaust gas recirculation rate during the first combustion is substantially 55% or more, and the exhaust gas recirculation rate during the second combustion is substantially 50%. The multi-cylinder internal combustion engine according to claim 10, which is equal to or less than a percentage. 12. 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 the first combustion is performed in the first operating region. 11. The system according to claim 10, wherein the second combustion is performed in a second operation range.
A multi-cylinder internal combustion engine according to claim 1.